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#1
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
Hi all,
Having ruled out a home theater system, I think what I'm looking for is a receiver and some speakers. I listen to lots of different music, but almost of it is at least partially acoustic--maybe an upright bass, maybe piano, so one of my top priorities is very real, realistic sound. Like, if the record is good enough, I'd love to stand in the other room and almost think that the musicians are there in my living room. Of course that's not my #1 priority. #1 is spending less that $400 on everything--receiver (or should I be calling it an amp?) and speakers. Think that's possible, considering this "realistic sound" think I'm after? The room where I want to put this stuff is about 185 square feet. Other necessary conditions: this is primarily for music, not TV or movies. I don't want any "surround" stuff; I consider that stuff gimmicky. Nevertheless, should I get more than two stereo speakers? Should I get one of these "center speakers," which is new to me, since I haven't really known anything about home audio since 1987. Also, I'd like to at least have separate treble/bass controls, if not a 5 or so band graphic equalizer. And nothing that boasts "bass boost." I like to control the bass level myself. So, any ideas? Is all this possible? Thanks! |
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#2
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
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#3
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Nov 17, 7:00 pm, wrote:
Hi all, Having ruled out a home theater system, I think what I'm looking for is a receiver and some speakers. I listen to lots of different music, but almost of it is at least partially acoustic--maybe an upright bass, maybe piano, so one of my top priorities is very real, realistic sound. Like, if the record is good enough, I'd love to stand in the other room and almost think that the musicians are there in my living room. Of course that's not my #1 priority. #1 is spending less that $400 on everything--receiver (or should I be calling it an amp?) and speakers. Think that's possible, considering this "realistic sound" think I'm after? The room where I want to put this stuff is about 185 square feet. Other necessary conditions: this is primarily for music, not TV or movies. I don't want any "surround" stuff; I consider that stuff gimmicky. Nevertheless, should I get more than two stereo speakers? Should I get one of these "center speakers," which is new to me, since I haven't really known anything about home audio since 1987. Also, I'd like to at least have separate treble/bass controls, if not a 5 or so band graphic equalizer. And nothing that boasts "bass boost." I like to control the bass level myself. So, any ideas? Is all this possible? For $400, about the only thing that is possible is a basic receiver and two bookshelf speakers. Start with the Onkyo TX-8222, available for $160 or so with shipping he http://www.jr.com/JRProductPage.process?Product=4130301 For speakers, you might try one of the Infinity models offered he http://snipurl.com/1tt2w Another alternative would be the Paradigm Atoms, which list for $250/ pr. bob |
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#4
Posted to rec.audio.tech,misc.writing.screenplays
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Seeking advice for buying home audio equipment
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#5
Posted to rec.audio.tech,misc.writing.screenplays
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Seeking advice for buying home audio equipment
"Robert Morein" wrote in message
... This is rec.audio.tech, for professionals only. Try rec.audio.assholes or some such group and don't ask these nonsense questions here. Please to ignore the postings from the village idiot. |
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#6
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
"Kevin McMurtrie" wrote in
message The Yamaha RX-397 is simple and elegant receiver but it costs almost $300. The Onkyo TX-8222 is $200 and should be a decent unit. Sony is coming out with a $150 receiver but that's not a brand I trust. You might be able to find a high-end receiver used. Sherwood's current ca. $80 wonder turns out to be just fine for a low cost system. http://electronics.pricegrabber.com/...ers/m/7930503/ Speakers are going to be even harder because you're probably stuck with the bookshelf size in your budget. There are such things as $150 floor-standers, but... Forget about decoders that attempt to create additional audio channels from stereo. A center channel that is a pure clean mix of L and R can be pretty good, but its not a popular offering. |
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#7
Posted to rec.audio.tech,misc.writing.screenplays
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Seeking advice for buying home audio equipment
"Robert Morein" wrote in message
wrote in message ... Having ruled out a home theater system, I think what I'm looking for is a receiver and some speakers. So, any ideas? Is all this possible? This is rec.audio.tech, for professionals only. Try rec.audio.assholes or some such group and don't ask these nonsense questions here. Bob Morein (310) 237-6511 It's the buzzardnews forger, looking for attention at any cost! :-( |
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#8
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Nov 18, 6:33 am, "Arny Krueger" wrote:
Sherwood's current ca. $80 wonder turns out to be just fine for a low cost system. Have you actually checked this unit out, Arny? I tend to be skeptical of very cheap components with very big claims (100w/ch!). But if it's a solid unit, that leaves room in his budget for some better speakers, like the PSB Alphas ($280). bob |
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#9
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
wrote in message ... Hi all, Having ruled out a home theater system, I think what I'm looking for is a receiver and some speakers. I listen to lots of different music, but almost of it is at least partially acoustic--maybe an upright bass, maybe piano, so one of my top priorities is very real, realistic sound. Like, if the record is good enough, I'd love to stand in the other room and almost think that the musicians are there in my living room. Of course that's not my #1 priority. #1 is spending less that $400 on everything--receiver (or should I be calling it an amp?) and speakers. Think that's possible, considering this "realistic sound" think I'm after? The room where I want to put this stuff is about 185 square feet. Other necessary conditions: this is primarily for music, not TV or movies. I don't want any "surround" stuff; I consider that stuff gimmicky. Nevertheless, should I get more than two stereo speakers? Should I get one of these "center speakers," which is new to me, since I haven't really known anything about home audio since 1987. Also, I'd like to at least have separate treble/bass controls, if not a 5 or so band graphic equalizer. And nothing that boasts "bass boost." I like to control the bass level myself. So, any ideas? Is all this possible? **Start looking at second hand equipment. Your Dollar will go a long way. Trevor Wilson |
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#10
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
wrote in message ... Hi all, Having ruled out a home theater system, I think what I'm looking for is a receiver and some speakers. I listen to lots of different music, but almost of it is at least partially acoustic--maybe an upright bass, maybe piano, so one of my top priorities is very real, realistic sound. Like, if the record is good enough, I'd love to stand in the other room and almost think that the musicians are there in my living room. Of course that's not my #1 priority. #1 is spending less that $400 on everything--receiver (or should I be calling it an amp?) and speakers. Think that's possible, considering this "realistic sound" think I'm after? The room where I want to put this stuff is about 185 square feet. Other necessary conditions: this is primarily for music, not TV or movies. I don't want any "surround" stuff; I consider that stuff gimmicky. Nevertheless, should I get more than two stereo speakers? Should I get one of these "center speakers," which is new to me, since I haven't really known anything about home audio since 1987. Also, I'd like to at least have separate treble/bass controls, if not a 5 or so band graphic equalizer. And nothing that boasts "bass boost." I like to control the bass level myself. So, any ideas? Is all this possible? I like to spend a month every year hob-nobbing with the intensely rich on the French Riviera every year. But that's not my #1 priority, feeding my family on my meagre salary is my #1 priority, so I don't do it. Your request is like asking if there's a car for sale which will do 200+ mph and cost under $5,000. Deep down, you already know the answer. You will be extremely hard pressed to purchase equipment for $400, either new or used, that will give you the chill-down-your-spine feeling that the musicians are in your room. I'm sorry, you just won't, not even with used equipment. First off, things like Dolby, DTS, THS, ProLogic, surround, etc. are home theatre terms. They are of no use playing music. Ditto with centre channel. The common "5.1" encoding of movies means that there are 5 full-range channels (vs. 2 for stereo): 2 front, 2 rear, and a center channel. The ".1" is a dedicated LFE (low-frequency effects) or subwoofer channel. Anything with "bass boost" is trash. It's a feature designed and marketed to teenagers. Graphic equalizers were popular for a time in the 80's, and, really, offer more control over your sound than does a bass or treble control. It's your call, I don't like them either. Most of the newer stuff has all digital controls, i.e. you push a "menu" button to get to "bass" or to an equalizer frequency range like "20-60Hz", then use "+" and "-" to increase or decrease the little bar graph on the display. I'm not a big fan... I like knobs. If I were you I'd look used, the 80's and early 90's had some really good quality integrated amps and receivers. Brands such as Marantz, Harman Kardon (not their new HT stuff), Luxman, Onkyo and Sansui all made good receivers and all still command prices today that reflect their build and sound quality. The tradeoff with these units is that they pre-date remote controls so... ya' gotta' get yer ass off the chair if you want to adjust anything. You can likely pick up an amp for $100 or so (plus shipping of course) on eBay, more cheaply if you're patient and give yourself a couple of months. The other $300 of your budget should go into speakers. Your choice of speakers will have a FAR FAR greater impact on the sound than your choice of amplifier. $300 (including shipping) is a very small amount of money for good audiophile-quality loudspeakers, which is what you want if you want that in-the-room feeling. You won't get it with consumer-grade junk from the likes of Sony or JVC. Again, keep your eyes on eBay and you might score something decent. Mid-range speakers are many, watch for Klipsch, Boston Acoustics, Mission, Wharfedale, the list goes on and on and on and on. Buying new at an audio-oriented shop you'd be able to audition different speakers, possibly on a simliar amp to your own, but such is not the case with used. Good luck and good hunting. Dave S. |
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#11
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
Trevor Wilson wrote:
wrote in message ... Hi all, Having ruled out a home theater system, I think what I'm looking for is a receiver and some speakers. So, any ideas? Is all this possible? **Start looking at second hand equipment. Your Dollar will go a long way. If you can find a good amp/receiver that way, it is a good idea. But this may not be easy. Perfectly good stereo receivers (with tuners, also phono inputs) are available for well less than $200. The tuners are not very sensitive nor overload-resistant, but other than that they work nicely. But beware of having no knob for balance, bass, or treble ... or perhaps even volume. Doug McDonald |
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#12
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
Doug McDonald wrote:
Trevor Wilson wrote: wrote in message ... Hi all, Having ruled out a home theater system, I think what I'm looking for is a receiver and some speakers. So, any ideas? Is all this possible? **Start looking at second hand equipment. Your Dollar will go a long way. If you can find a good amp/receiver that way, it is a good idea. But this may not be easy. Perfectly good stereo receivers (with tuners, also phono inputs) are available for well less than $200. The tuners are not very sensitive nor overload-resistant, but other than that they work nicely. But beware of having no knob for balance, bass, or treble ... or perhaps even volume. Doug McDonald Yet not impossible. Yesterday I picked up a set of KLH model 17's at a thrift store for $8.99. They sound great, especially given that they're 40 year old technology; smooth, transparent, good imaging, solid bass...maybe a little inefficient, with 'not very' extended high end, but *very* listenable. The best subjective word I can come up with to describe them is 'sweet'...no bad habits. I need to remove the grill cloths and clean them, then sand and oil the walnut veneer. Some people say that the capacitors in the crossover should be replaced and the woofer surrounds (rubberized cloth, NOT foam!) should be 're-rubberized'. I've picked up 'formerly' high end gear at thrift stores, pawn shops, yard sales and Craigslist. I could easily put together something out odds & ends laying around that would 'do' what he needs. Excluding my time and shipping costs, I'd probably have less than $100 in the whole thing. Of course, I'm using most of my 'odds & ends'.... jak |
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#13
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
"bob" wrote in message
On Nov 18, 6:33 am, "Arny Krueger" wrote: Sherwood's current ca. $80 wonder turns out to be just fine for a low cost system. Have you actually checked this unit out, Arny? I own one. I tend to be skeptical of very cheap components with very big claims (100w/ch!). But if it's a solid unit, that leaves room in his budget for some better speakers, like the PSB Alphas ($280). I use mine with a pair of Boston Acoustics CR-9s. |
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#14
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Nov 19, 7:36 pm, "Arny Krueger" wrote:
"bob" wrote in message On Nov 18, 6:33 am, "Arny Krueger" wrote: Sherwood's current ca. $80 wonder turns out to be just fine for a low cost system. Have you actually checked this unit out, Arny? I own one. Well, all right then. I tend to be skeptical of very cheap components with very big claims (100w/ch!). But if it's a solid unit, that leaves room in his budget for some better speakers, like the PSB Alphas ($280). I use mine with a pair of Boston Acoustics CR-9s. So it should drive any reasonably efficient 8 ohm speaker, of the sort you'd find in the $300 price range these days. Probably a good choice for the OP. bob |
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#15
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
Thanks very much to all for all the detailed suggestions.
Sure enough, you guys know more than I'm presently able/willing to take all in, considering how soon I want to get some music set up. I have gleaned some useful info, though, and it will inform how I approach buying some consumer-end stuff, which is what I'm pretty sure I'm going to do. All that said, and at risk of being flamed by the buzzardnews forger again, I have one more question for now--any strong opinions about whether Polk's speakers at about this range: http://www.jr.com/JRProductPage.process?Product=3724397 are appropriate for what I'm looking for? (Yes, my budget is already expanding). And can you really get great bass, even if you're Polk, out of just a 6.5" woofer, like that product has? Thanks again. |
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#17
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
"bob" wrote in message
On Nov 19, 7:36 pm, "Arny Krueger" wrote: "bob" wrote in message On Nov 18, 6:33 am, "Arny Krueger" wrote: Sherwood's current ca. $80 wonder turns out to be just fine for a low cost system. Have you actually checked this unit out, Arny? I own one. Well, all right then. I tend to be skeptical of very cheap components with very big claims (100w/ch!). But if it's a solid unit, that leaves room in his budget for some better speakers, like the PSB Alphas ($280). I use mine with a pair of Boston Acoustics CR-9s. So it should drive any reasonably efficient 8 ohm speaker, of the sort you'd find in the $300 price range these days. Probably a good choice for the OP. Agreed. I think one can do better for the money than PSB alphas. I know that the bi-amped versions of the Behringer B2031a speakers sound very good. The passive versions are called the B2031P, have the same drivers and enclosure, and sell for less than $200 a pair. |
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#18
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
"Kevin McMurtrie" wrote in message ... And can you really get great bass, even if you're Polk, out of just a 6.5" woofer, like that product has? It takes more power and a well-designed driver and enclosure to coax bass out of a small driver. Porting the enclosure is a cheap way to get bass frequency reproduction from a smaller box. It also reduces the power required to drive the speaker. The trade-off is "tightness" in the low end as the bass is not coming off the speaker cone but is being derived by bouncing the soundwaves around in the enclosure and letting them out through the port. Some say there is a "delay" between when the bass is actually generated and when it comes out of the ported enclosure which puts the sound "off" because the higher-frequencies and the bass frequencies are out of phase. I believe this is only a factor in poorly-designed speakers given the enormous variety of ported-enclosure speakers on the market. You'll have to try them. Believe it or not, Polk has made some ****ty speakers and Optimus has made some good speakers. That's not the norm but it happens sometimes. I'd never buy over the internet without listening. Unfortunately trying them will likely not be an option. But... the beauty of eBay is that if you don't like what you get, you can likely turn around and re-sell it for about the price you paid for it, losing only the amount spent on shipping. |
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#19
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
Dave, I thought of telling him something like this, but it's very
difficult to move a person off his preconceptions, even someone with whom one has a personal acquaintance, and this fellow doesn't know us. I think it's possible to come close, but only under the tutelage of a good friend who knows the used market. That's the advantage I had when I started out. **snip** I think he could come close with $400 on the electronics, very carefully spent. The speakers are another problem for another day. Every so often, someone throws out a good pair because they can't "hear the difference." Oh if he blew his wad on the amp/preamp sure he could do really well... I think right now in my living room I've only got about $400 into my system, an Adcom pre-amp from the early 80's driving a slightly older HK big heavy bulletproof power amp. Probably 1/3 of what I paid was shipping, seriously. My speakers cost more but... poking around on eBay I see a pair of old Klipsch KG-3.5's for $100. They are great speakers, highly efficient with the horn tweeters, probably 95 db/w/m. I'm not saying they'll match the Martin Logans or Tannoys but for $80 I think the OP'd be real happy with them. Some people see more value in "new" than in "good"; I think appreciating value (the wheat in the chaff) is an acquired trait. When I was young and foolish I had a great HH Scott 222C tube amp which my dad had built from a kit. 25 wpc, fantastic construction, still brings $300-$400 on eBay. Man, I couldn't wait to get rid of that boat anchor for my brand-new technics push-button all-digital receiver with the spiffy graphic equalizer... As you also noted, some people really CAN'T hear the difference. My wife is a classic example. She's highly educated and has refined tastes in other areas, but it is honestly more important to her to have a full-function remote control than to have great sound... anything over $200 spent on audio equipment is wasted on her. Dave S. |
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#20
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Nov 20, 10:10 am, "Dave" wrote:
And can you really get great bass, even if you're Polk, out of just a 6.5" woofer, like that product has? It takes more power and a well-designed driver and enclosure to coax bass out of a small driver. Porting the enclosure is a cheap way to get bass frequency reproduction from a smaller box. It also reduces the power required to drive the speaker. The trade-off is "tightness" in the low end as the bass is not coming off the speaker cone but is being derived by bouncing the soundwaves around in the enclosure and letting them out through the port. Well, certainly one of the more interesting explanations about how a ported system works, but pretty much wrong on nearly every point, nonetheless. First, a properly design ported system is NOT a cheap way to do it. Done correctly, it's more expensive: 1. A driver suited for a ported system will generally require a larger magnet system to achieve the required electromechanical parameters needed, and the magnet system is the most expensive part of the driver, 2. The cabinet and assembly costs are more expensive, Second, it does NOT a priori reduce the amount of power needed to drive the system. One can certainly design a proper reflex system that has a relatively low efficiency by trading efficiency for enclosure size, or efficiency for bandwidth, etc. Third, the bass is most certainly NOT derived by "bouncing the soundwaves around in the enclosure and letting them out through the port. " At the frequencies where the port is active, the wavelengths are MUCH longer than the largest dimension of the cabinet (e.g., a 1/2 cubic foot cabinet tunde to, oh, 50 Hz, not atypical of a 6.5" reflex system) might have it's largest linear dimension on the order of a foot, while at 50 Hz, the wavelength more than 20 times longer. In essence at those frequencies, the sound pressure within the enclosure is pretty much the same everywhere. There's now "bouncing around" going on at all. Instead, first realize that, done right, a driver for a ported system is DESIGNED to be used in a ported system. It has a larger magnet structure needed to achieve the proper Qt for ported operation, and, all other things being equal, that larger magnet also buys you a higher efficiency. Now the combination of enclosure volume and the port together form an acoustical resonant system, tuned to a specific frequency. The combination of this driver and the resonant system of the enclosure and port result the port supplanting the driver output at the tuning frequency, leveling the frequency response. I would posit that the "tightness" claim is merely a reflection of poorly designed system. One can design a QB3 aligned reflex system with bandwidth and transient capabilities equaling an exceeding sealed box systems of similar size and efficiency. |
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#21
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
wrote in message ... On Nov 20, 10:10 am, "Dave" wrote: 1. A driver suited for a ported system will generally require a larger magnet system to achieve the required electromechanical parameters needed, and the magnet system is the most expensive part of the driver, The larger magnet driver will be more expensive than an identical-sized non-ported-use driver. However, it is potentially cheaper than the larger driver in the larger enclosure one would need to reproduce the bass frequencies if one did not use a ported design. 2. The cabinet and assembly costs are more expensive, Second, it does NOT a priori reduce the amount of power needed to drive the system. One can certainly design a proper reflex system that has a relatively low efficiency by trading efficiency for enclosure size, or efficiency for bandwidth, etc. The use of a ported enclosure DOES in fact reduce the amount of power required to drive a given driver to a given spl. Physics says that it takes more energy to move a driver which is compressing the air in a sealed enclosure than it does to move the same driver in a ported enclosure with no pressure differential. Let's take subwoofers as an example. Why is it that many if not most of the ported designs run oh, say, 100-300W internal amplifiers, whereas the same size driver in a non-ported box commonly run 600+ watt amps for the same spl output? It is somewhat to do with trading efficiency for size, but is that all of it? Third, the bass is most certainly NOT derived by "bouncing the soundwaves around in the enclosure and letting them out through the port. " At the frequencies where the port is active, the wavelengths are MUCH longer than the largest dimension of the cabinet (e.g., a 1/2 cubic foot cabinet tunde to, oh, 50 Hz, not atypical of a 6.5" reflex system) might have it's largest linear dimension on the order of a foot, while at 50 Hz, the wavelength more than 20 times longer. In essence at those frequencies, the sound pressure within the enclosure is pretty much the same everywhere. There's now "bouncing around" going on at all. Learn something new every day. Instead, first realize that, done right, a driver for a ported system is DESIGNED to be used in a ported system. It has a larger magnet structure needed to achieve the proper Qt for ported operation, and, all other things being equal, that larger magnet also buys you a higher efficiency. Now the combination of enclosure volume and the port together form an acoustical resonant system, tuned to a specific frequency. The combination of this driver and the resonant system of the enclosure and port result the port supplanting the driver output at the tuning frequency, leveling the frequency response. I would posit that the "tightness" claim is merely a reflection of poorly designed system. One can design a QB3 aligned reflex system with bandwidth and transient capabilities equaling an exceeding sealed box systems of similar size and efficiency. |
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#22
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Nov 20, 12:38 am, wrote:
Thanks very much to all for all the detailed suggestions. Sure enough, you guys know more than I'm presently able/willing to take all in, considering how soon I want to get some music set up. I have gleaned some useful info, though, and it will inform how I approach buying some consumer-end stuff, which is what I'm pretty sure I'm going to do. All that said, and at risk of being flamed by the buzzardnews forger again, I have one more question for now--any strong opinions about whether Polk's speakers at about this range:http://www.jr.com/JRProductPage.proc...uct=3724397are appropriate for what I'm looking for? (Yes, my budget is already expanding). Polk's not bad, overall. And that's quite a bargain. Given your price constraints, it might be a very good choice. You'd have to hear them to be sure, however, which is always the trick when you've going the mail-order route. And can you really get great bass, even if you're Polk, out of just a 6.5" woofer, like that product has? That product as TWO 6.5" woofers, which is maybe roughly equivalent to a single 9" woofer. So yeah, it can move a fair amount of air. But as others have noted, driver size is only a piece of puzzle. bob |
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#23
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Nov 20, 11:21 am, "Dave" wrote:
wrote in message On Nov 20, 10:10 am, "Dave" wrote: 1. A driver suited for a ported system will generally require a larger magnet system to achieve the required electromechanical parameters needed, and the magnet system is the most expensive part of the driver, The larger magnet driver will be more expensive than an identical-sized non-ported-use driver. However, it is potentially cheaper than the larger driver in the larger enclosure one would need to reproduce the bass frequencies if one did not use a ported design. "potentially" is not "is." Wood is a lot cheaper than strontium ferrite and steel and copper. Exhibit in very low-end speakers, driver costs dominate the systems materials cost. Second, it does NOT a priori reduce the amount of power needed to drive the system. One can certainly design a proper reflex system that has a relatively low efficiency by trading efficiency for enclosure size, or efficiency for bandwidth, etc. The use of a ported enclosure DOES in fact reduce the amount of power required to drive a given driver to a given spl. Physics says that it takes more energy to move a driver which is compressing the air in a sealed enclosure than it does to move the same driver in a ported enclosure with no pressure differential. Maybe your physics does, but the actual physics does not. Above the system cutoff, the system is operating in the mass-controlled region of operation. That means efficiency is determined by the moving mass of the system. Only below cutoff is the system stiffness- controlled. What that means is that in its passband, any direct-radiator driver has an efficiency which is independent of the size or type of enclosure in which it is placed. What DOES change is the cutoff frequency, but above that cutoff, the amount of electrical input power needed to produce a given sound pressure level is unchanged. Small [1] shows that the reference efficiency of the driver is determined by the square of the electromagnetic transduction factor (Bl product), and the reciprocal of the product of voice coil resistance (Re), the square of the emissive area and the square of the moving mass (eq 11). There is NO term for stiffness, either mechanical or acoustical. This is consistent with the assertion above that the system, in its passband, is mass-controlled. Further, Small states: "The closed box system efficiency in the passband region, or system reference efficiency. is the reference efficiency of the driver"[2] and "The piston-range reference efficiency of a vented- box loudspeaker system is the reference efficiency of the system driver"[3] In essence, the passband efficiency of the system is determined by the driver, NOT BY THE TYPE OR SIZE OF ENCLOSURE IT IS PLACED IN. References: [1} Small, R. H, "Direct Radiator Loudspeaker System Analysis," JAES 1972 June [2] Small, R. H., "Close-Box Loudspeaker Systems - Part 1: Analysis," JAES 1972 December [3] Small, R. H., "Vented-Box Loudspeaker Systems - Part i: Small-Signal Analysis," JAES 1973 June Let's take subwoofers as an example. Why is it that many if not most of the ported designs run oh, say, 100-300W internal amplifiers, whereas the same size driver in a non-ported box commonly run 600+ watt amps for the same spl output? It is somewhat to do with trading efficiency for size, but is that all of it? On the assumption that all other parameters are held constant (a BAD assumption) and that the system is competently design (another BAD assumption), then for a given enclosure size and cutoff frequency, a maximum-efficiency closed box system will REQUIRE a driver whose parameters make its efficiency half that of the driver REQUIRED for a maximum efficiency vented system. I might suggets, in fact, you try an experiment to confirm or refute your hypothesis: Take a driver, ANY driver. Drive it with a conventional amplifier at a constant voltage with a signal like, oh, pink noise band-limited to the passband of the driver. Measure it's acoustical output in an infinite baffle, a 2 cubic foot, a 1 cubic foot, a half cubic foot and a quarter cubic foot. Your hypothesis predicts the passband acoustical output will be different in each case, Small's model (one which I agree with) predicts the passband acoustical output will remain essentially constant. Now, it so happens that I have, in fact, the facilities all set up to do such an experiment. In fact, it takes me about 5 minutes to set up and do it. I selected a 6.5" mid-woofer and placed it in my test baffle, behind which I can attach different volumes. I measured it using an octave-wide band of pink noise centered at 250 Hz, driven so that I was producing 2.83 volts at the driver terminals. Since this is at the resistive portion of the speaker's impedance, which is, at that point, average 7.1 ohms, the speaker was dissipating on the order of 1.14 watts. Placed in the standard measuring position 1 meter on axis from the driver, is a Bruel & Kjaer 4133 1/2" condenser mic whose output can be switched between one of several SPL meters or measuring systems, such as an Audiomatica CLio, or a DRA MLSSA. Now, I made my measurements. Go make yours and let's compare them. |
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#24
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Seeking advice for buying home audio equipment
On Nov 20, 7:59 am, "Arny Krueger" wrote:
I think one can do better for the money than PSB alphas. No doubt one can. But the Alphas measure very well for their class: http://www.stereophile.com/budgetcom...sb/index4.html and they're made by one of those Canadian companies that have taken Floyd Toole's NRC research to heart. So I'd expect them to outperform what the consumer is likely to find for the price at Best Buy or Circuit City--where most non-audiophiles are likely to be shopping. bob |
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#25
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Seeking advice for buying home audio equipment
In article PPD0j.1682$HH2.533@edtnps82, "Dave" wrote:
wrote in message ... On Nov 20, 10:10 am, "Dave" wrote: 1. A driver suited for a ported system will generally require a larger magnet system to achieve the required electromechanical parameters needed, and the magnet system is the most expensive part of the driver, The larger magnet driver will be more expensive than an identical-sized non-ported-use driver. However, it is potentially cheaper than the larger driver in the larger enclosure one would need to reproduce the bass frequencies if one did not use a ported design. 2. The cabinet and assembly costs are more expensive, Second, it does NOT a priori reduce the amount of power needed to drive the system. One can certainly design a proper reflex system that has a relatively low efficiency by trading efficiency for enclosure size, or efficiency for bandwidth, etc. The use of a ported enclosure DOES in fact reduce the amount of power required to drive a given driver to a given spl. Physics says that it takes more energy to move a driver which is compressing the air in a sealed enclosure than it does to move the same driver in a ported enclosure with no pressure differential. You may incorrectly assume the port makes it easier for the driver to move, which it does not at the tunned frequency. greg |
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#26
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Seeking advice for buying home audio equipment
Now, I made my measurements. Go make yours and let's compare them. I would, but, in fact, do not own the equipment required to make such measurements. We'll have to accept the validity of your results. Feel free to publish them in this forum. Thinking of subwoofers, I would guess that they may be in a bit of a separate class from smaller loudspeakers given the large area of the cone vs. the enclosure volume. Couple this with the "long throw" high excursion of the subwoofer driver and air pressure may become a factor in the power requirements of the sealed enclosure units. I dunno, but I'll bet you probably have some thoughts on this, as would Mr. Small no doubt. Very enlightening, all this info. Dave S. |
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#27
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
"G" wrote in message ... You may incorrectly assume the port makes it easier for the driver to move, which it does not at the tunned frequency. greg That is exactly what I assumed. |
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#28
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Nov 20, 1:53 pm, "Dave" wrote:
Now, I made my measurements. Go make yours and let's compare them. I would, but, in fact, do not own the equipment required to make such measurements. We'll have to accept the validity of your results. Feel free to publish them in this forum. As measured: Infinite baffle - 86.5 dB 50 liters - 86.4 20 liters - 86.7 10 liters - 86.5 These are the averages of several measurements, each has an error of about +-0.2 dB Thinking of subwoofers, I would guess that they may be in a bit of a separate class from smaller loudspeakers given the large area of the cone vs. the enclosure volume. Nope, same physics apply: above cutoff, the system is mass-controlled, not stiffness-controlled, and the efficiency is independent of enclosure volume. Couple this with the "long throw" high excursion of the subwoofer driver and air pressure may become a factor in the power requirements of the sealed enclosure units. Where it DOES have factor is like this: suppose you want to design a subwoofer with a small volume. Indeed, the acoustic compliance of such a volume is small. You find that when you put a high-efficiency woofer with a litght- weight cone in it, the resulting system resonance is too high to be a "sub"woofer. So, you add mass to the cone. This does three things: 1. Lowers the resonant frequency of the system, 2. raises the Qt of the system, 3. lowers the system efficiency. So, yes, the small, closed box system has a lower efficiency for a given bandpass, but NOT because the air is stiff, it's because the moving mass of the cone has to be high to get the resonant frequency down there. The efficiency suffers not because the cone is "working" against the air, it's because the cone is heavy. If you took the same driver and put it into a tiny sealed box, a big sealed box, an infinite baffle and a reflex enclosure, and measured the passband efficiency, you'd get the same number for each. You'd also get different responses in the low end as well. Think of the suspension of a car. If you walk up to the bumper and try to push it down, it's hard to move because you're working against the stiffness of the spring. But now try to shake the car up and down 3-4 times per second. It's REAL hard NOT because the springs are stiff, but because you're trying to start stop and reverse a ton or two of mass. In fact, at 3-4 times per second, it'd be just as hard to shake it if it was floating in outer space, where the stiffness of the spring has no relevance: you're exciting it at a frequency where it's the mass that dominates, not the stiffness. And the point where you transition from the stiffness dominating to the mass dominating is the resonant frequency of the car/suspension system. Same for loudspeakers. |
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#29
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Nov 20, 1:56 pm, "Dave" wrote:
"G" wrote in message ... You may incorrectly assume the port makes it easier for the driver to move, which it does not at the tunned frequency. greg That is exactly what I assumed. And that's a common, but incorrect, assumption. If you have access to a sine-wave oscillator, you can see this in action. Take a ported loudspeaker and paint a small white dot on the cone, something you can easily see. Then take a cotton ball and put it in the port. Start at a high frequency, say, 500 Hz, and slowly tune downwards in frequency, watching the motion of the white dot on the cone and the cotton ball. As you move downward, you'll see that the cone moves more and more. In fact, for every octave you drop, the distance the cone travels quadruples. if it was moving ..01" at 500 Hz, at 250 it will be moving .04", at 125 Hz, and so on. And you'll see the cotton ball remain motionless. That is until you start to approach the enclosure resonant frequency. There you will see a most curious behavior: as you approach it, the cone excursion starts to drop while the motion of the cotton ball increases until you get to the resonant frequency. At that point, the cone is almost stationary, while the cotton ball is vibrating back and forth rather much. Keep going do in frequency, and the revers starts to happen: the motion of the cone increases while that of the cotton ball decreases. What that means is that at the enclosure resonance, since it is moving so little, very little of the total acoustic output comes from the cone: most of it comes from the port, while the opposite is the case at most other frequencies. |
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#30
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
On Tue, 20 Nov 2007 11:50:00 -0800 (PST), wrote:
On Nov 20, 1:56 pm, "Dave" wrote: "G" wrote in message ... You may incorrectly assume the port makes it easier for the driver to move, which it does not at the tunned frequency. greg That is exactly what I assumed. And that's a common, but incorrect, assumption. If you have access to a sine-wave oscillator, you can see this in action. Take a ported loudspeaker and paint a small white dot on the cone, something you can easily see. Then take a cotton ball and put it in the port. Start at a high frequency, say, 500 Hz, and slowly tune downwards in frequency, watching the motion of the white dot on the cone and the cotton ball. As you move downward, you'll see that the cone moves more and more. In fact, for every octave you drop, the distance the cone travels quadruples. if it was moving .01" at 500 Hz, at 250 it will be moving .04", at 125 Hz, and so on. And you'll see the cotton ball remain motionless. That is until you start to approach the enclosure resonant frequency. There you will see a most curious behavior: as you approach it, the cone excursion starts to drop while the motion of the cotton ball increases until you get to the resonant frequency. At that point, the cone is almost stationary, while the cotton ball is vibrating back and forth rather much. Keep going do in frequency, and the revers starts to happen: the motion of the cone increases while that of the cotton ball decreases. What that means is that at the enclosure resonance, since it is moving so little, very little of the total acoustic output comes from the cone: most of it comes from the port, while the opposite is the case at most other frequencies. I've just finished tuning my subwoofer ports. I did it by standing a small candle in the port and watching the flame thrash about. d -- Pearce Consulting http://www.pearce.uk.com |
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#31
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
wrote in message ... On Nov 20, 1:53 pm, "Dave" wrote: Now, I made my measurements. Go make yours and let's compare them. I would, but, in fact, do not own the equipment required to make such measurements. We'll have to accept the validity of your results. Feel free to publish them in this forum. As measured: Infinite baffle - 86.5 dB 50 liters - 86.4 20 liters - 86.7 10 liters - 86.5 These are the averages of several measurements, each has an error of about +-0.2 dB Thinking of subwoofers, I would guess that they may be in a bit of a separate class from smaller loudspeakers given the large area of the cone vs. the enclosure volume. Nope, same physics apply: above cutoff, the system is mass-controlled, not stiffness-controlled, and the efficiency is independent of enclosure volume. Couple this with the "long throw" high excursion of the subwoofer driver and air pressure may become a factor in the power requirements of the sealed enclosure units. Where it DOES have factor is like this: suppose you want to design a subwoofer with a small volume. Indeed, the acoustic compliance of such a volume is small. You find that when you put a high-efficiency woofer with a litght- weight cone in it, the resulting system resonance is too high to be a "sub"woofer. So, you add mass to the cone. This does three things: 1. Lowers the resonant frequency of the system, 2. raises the Qt of the system, 3. lowers the system efficiency. So, yes, the small, closed box system has a lower efficiency for a given bandpass, but NOT because the air is stiff, it's because the moving mass of the cone has to be high to get the resonant frequency down there. The efficiency suffers not because the cone is "working" against the air, it's because the cone is heavy. If you took the same driver and put it into a tiny sealed box, a big sealed box, an infinite baffle and a reflex enclosure, and measured the passband efficiency, you'd get the same number for each. You'd also get different responses in the low end as well. Think of the suspension of a car. If you walk up to the bumper and try to push it down, it's hard to move because you're working against the stiffness of the spring. But now try to shake the car up and down 3-4 times per second. It's REAL hard NOT because the springs are stiff, but because you're trying to start stop and reverse a ton or two of mass. In fact, at 3-4 times per second, it'd be just as hard to shake it if it was floating in outer space, where the stiffness of the spring has no relevance: you're exciting it at a frequency where it's the mass that dominates, not the stiffness. And the point where you transition from the stiffness dominating to the mass dominating is the resonant frequency of the car/suspension system. Same for loudspeakers. Thanks. That analogy makes sense. Added resonant mass lowers the frequency which can be reproduced. So, theoretically one could design a subwoofer of an infinitely small size with an infinitely low frequency response by using an infinitely heavy driver driven by an infinitely powerful amplifier. On a more practical level, that's how Velodyne's DD-10 10" sealed enclosure subwoofer uses a 310 oz. magnet and a 1250W amplifier to get down to 20Hz in a relatively tiny box. Dave S. |
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#32
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
In article , (Don Pearce) wrote:
On Tue, 20 Nov 2007 11:50:00 -0800 (PST), wrote: On Nov 20, 1:56 pm, "Dave" wrote: "G" wrote in message ... You may incorrectly assume the port makes it easier for the driver to move, which it does not at the tunned frequency. greg That is exactly what I assumed. And that's a common, but incorrect, assumption. If you have access to a sine-wave oscillator, you can see this in action. Take a ported loudspeaker and paint a small white dot on the cone, something you can easily see. Then take a cotton ball and put it in the port. Start at a high frequency, say, 500 Hz, and slowly tune downwards in frequency, watching the motion of the white dot on the cone and the cotton ball. As you move downward, you'll see that the cone moves more and more. In fact, for every octave you drop, the distance the cone travels quadruples. if it was moving .01" at 500 Hz, at 250 it will be moving .04", at 125 Hz, and so on. And you'll see the cotton ball remain motionless. That is until you start to approach the enclosure resonant frequency. There you will see a most curious behavior: as you approach it, the cone excursion starts to drop while the motion of the cotton ball increases until you get to the resonant frequency. At that point, the cone is almost stationary, while the cotton ball is vibrating back and forth rather much. Keep going do in frequency, and the revers starts to happen: the motion of the cone increases while that of the cotton ball decreases. What that means is that at the enclosure resonance, since it is moving so little, very little of the total acoustic output comes from the cone: most of it comes from the port, while the opposite is the case at most other frequencies. I've just finished tuning my subwoofer ports. I did it by standing a small candle in the port and watching the flame thrash about. That would be ported flame, flame thrower, port o fire, flammed port, or 911. greg |
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#33
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Seeking advice for buying home audio equipment
On Nov 20, 3:15 pm, "Dave" wrote:
wrote in message ... On Nov 20, 1:53 pm, "Dave" wrote: Now, I made my measurements. Go make yours and let's compare them. I would, but, in fact, do not own the equipment required to make such measurements. We'll have to accept the validity of your results. Feel free to publish them in this forum. As measured: Infinite baffle - 86.5 dB 50 liters - 86.4 20 liters - 86.7 10 liters - 86.5 These are the averages of several measurements, each has an error of about +-0.2 dB Thinking of subwoofers, I would guess that they may be in a bit of a separate class from smaller loudspeakers given the large area of the cone vs. the enclosure volume. Nope, same physics apply: above cutoff, the system is mass-controlled, not stiffness-controlled, and the efficiency is independent of enclosure volume. Couple this with the "long throw" high excursion of the subwoofer driver and air pressure may become a factor in the power requirements of the sealed enclosure units. Where it DOES have factor is like this: suppose you want to design a subwoofer with a small volume. Indeed, the acoustic compliance of such a volume is small. You find that when you put a high-efficiency woofer with a litght- weight cone in it, the resulting system resonance is too high to be a "sub"woofer. So, you add mass to the cone. This does three things: 1. Lowers the resonant frequency of the system, 2. raises the Qt of the system, 3. lowers the system efficiency. So, yes, the small, closed box system has a lower efficiency for a given bandpass, but NOT because the air is stiff, it's because the moving mass of the cone has to be high to get the resonant frequency down there. The efficiency suffers not because the cone is "working" against the air, it's because the cone is heavy. If you took the same driver and put it into a tiny sealed box, a big sealed box, an infinite baffle and a reflex enclosure, and measured the passband efficiency, you'd get the same number for each. You'd also get different responses in the low end as well. Think of the suspension of a car. If you walk up to the bumper and try to push it down, it's hard to move because you're working against the stiffness of the spring. But now try to shake the car up and down 3-4 times per second. It's REAL hard NOT because the springs are stiff, but because you're trying to start stop and reverse a ton or two of mass. In fact, at 3-4 times per second, it'd be just as hard to shake it if it was floating in outer space, where the stiffness of the spring has no relevance: you're exciting it at a frequency where it's the mass that dominates, not the stiffness. And the point where you transition from the stiffness dominating to the mass dominating is the resonant frequency of the car/suspension system. Same for loudspeakers. Thanks. That analogy makes sense. Added resonant mass lowers the frequency which can be reproduced. Well, it lowers the resonant frequency AND the efficiency of the system. That lowers the frequency above which you're in the passband of the system. You can still reproduce frequencies lower than that, just at an increasingly more attenuated level as you go lower in frequency. So, theoretically one could design a subwoofer of an infinitely small size with an infinitely low frequency response by using an infinitely heavy driver driven by an infinitely powerful amplifier. Well, ignoring the "infinite" and the inevitable undefined results, no, one cannot obtain an arbitrarily frequency with ANY woofer, because: it would have to produce continuous wind. And, in any case, such a design with an infinitely small box and a very low frequency drives your efficiency towards 0. On a more practical level, that's ho Velodyne's DD-10 10" sealed enclosure subwoofer uses a 310 oz. magnet and a 1250W amplifier to get down to 20Hz in a relatively tiny box. No, not quite. What is happening is that they are adding, in effect, supplemantary equalization to get the low frequency extension. A large woofer with a big magnet in a small box results in a high cutoff, overdamped response with high efficiency. Either with active equalization (such as Bag End do), or using feedback techniques, the idea is to produce a inverse of the 12 dB rolloff that occurs below resonance with a complementary 12 dB per octave boost. The result is a flat response below resonance with a high effieicny in a small box, but at the cost of complexity and cost and a higher order system with arguably worse transient performance. |
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#34
Posted to rec.audio.tech
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Seeking advice for buying home audio equipment
wrote in message ... On a more practical level, that's ho Velodyne's DD-10 10" sealed enclosure subwoofer uses a 310 oz. magnet and a 1250W amplifier to get down to 20Hz in a relatively tiny box. No, not quite. What is happening is that they are adding, in effect, supplemantary equalization to get the low frequency extension. A large woofer with a big magnet in a small box results in a high cutoff, overdamped response with high efficiency. Either with active equalization (such as Bag End do), or using feedback techniques, the idea is to produce a inverse of the 12 dB rolloff that occurs below resonance with a complementary 12 dB per octave boost. The result is a flat response below resonance with a high effieicny in a small box, but at the cost of complexity and cost and a higher order system with arguably worse transient performance. So the subwoofer amplifier is designed in such a way as to provide this "inverse rolloff" with a 12dB/octave slope to the sub-resonant-frequency portion of the audio spectrum. Do all subwoofer amps do this? If not is it simply a cost issue? It doesn't seem like it would take an awful lot of parts (read cost) to implement this for a known resonant frequency. I've got a Velodyne sub which goes down to 25Hz with a 12" driver, could I get lower with a different amp? I guess that amp would need to be specific to the resonant frequency of my enclosure. To recap: a heavier driver lowers the resonant frequency at the expense of efficiency. There is an known 12 dB/octave rolloff below resonant frequency which can be compansated for by means of application of an equalization boost or "inverse rolloff". Is it the box volume, the box design, the driver, or a combination of all three which determines the resonant frequency to begin with? What do you mean by "arguably worse transient performance"? |
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#35
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Seeking advice for buying home audio equipment
Dave wrote:
[subs with electrical frequency compensation] What do you mean by "arguably worse transient performance"? grossly oversimplified: the steeper the filter, the more ringing. The longer you extend frequency response downwards the steeper the roll off will need to be, a probable target curve for such a system is a fourth or sixth order highpass at some lower frequency. Kind regards Peter Larsen |
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#36
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Seeking advice for buying home audio equipment
On Nov 20, 6:49 pm, "Dave" wrote:
wrote in message ... On a more practical level, that's ho Velodyne's DD-10 10" sealed enclosure subwoofer uses a 310 oz. magnet and a 1250W amplifier to get down to 20Hz in a relatively tiny box. No, not quite. What is happening is that they are adding, in effect, supplemantary equalization to get the low frequency extension. A large woofer with a big magnet in a small box results in a high cutoff, overdamped response with high efficiency. Either with active equalization (such as Bag End do), or using feedback techniques, the idea is to produce a inverse of the 12 dB rolloff that occurs below resonance with a complementary 12 dB per octave boost. The result is a flat response below resonance with a high effieicny in a small box, but at the cost of complexity and cost and a higher order system with arguably worse transient performance. So the subwoofer amplifier is designed in such a way as to provide this "inverse rolloff" with a 12dB/octave slope to the sub-resonant-frequency portion of the audio spectrum. A couple of points: the 12 dB/octave rolloff is the asymtotic rate for closed-box or infinite baffle systems. For higher order systems (closed box and infinite baffle systems are second order) such as fourth-order ported systems, the asymtotic rate is 24 dB per octave. Now, one example of such a system is a light cone and/or large magnet in a small box, and end up with a high-efficiency system with a high resonant frequency. maybe as high as above 100 Hz that's also reasonably well damped (say, Qt =0.71, giving maximully flat amplitude response). Then do a simple second order boost EQ whose corner frequency is the same as the resonant frequency of the system, but then temrinated with its own second order rolloff at some low frequency (maybe 25-30 Hz. The result will be a maximally flat amplitude 4th order system that's flat to that low cutoff and rolls off at 18 dB octave below that. Optimized such a system will have the same phase, amplitude and transient response as a ported system with the same cutoff frequency, but have a 3 dB advantage in efficiency over the ported version for the same size enclosure. There are any number of ways of configuring such a system. Do all subwoofer amps do this? No, but many do, and if you're going to integrate the subwoofer and its amplifier into a single box, there are plenty of reasons to do it this way. If not is it simply a cost issue? Everything is a cost issue. Big cabinets are more expensive to warehouse and ship, but internal amplifiers use expensive iron and copper and silicon. It doesn't seem like it would take an awful lot of parts (read cost) to implement this for a known resonant frequency. It depends upon which parts you're talking about. Harkening to a prior discussion, if it's a matter of trading magnet for wood in an enclosure, the wood often wins because it's cheaper in raw cost than the iron, copper and expensive ferrites in the magnet. But then you have the shipping costs and so on. It's never a clear tradeoff one way or the other. I've got a Velodyne sub which goes down to 25Hz with a 12" driver, could I get lower with a different amp? Not without significantly compromising the reliability of the system. No matter how you get there with a sealed system, the required excursion for a given sound pressure level goes as the reciprocal of the square of the frequency, so producing the same level at 20 Hz taht you would do at 25, which is only 1/3 of an octave, would require 60% MORE excursion. I guess that amp would need to be specific to the resonant frequency of my enclosure. You bet it would. To recap: a heavier driver lowers the resonant frequency at the expense of efficiency. Very specifically: all other things being equal, it's the moving mass (cone, voice coil, etc) that we're talking about. And increasing that mask has several effects: 1. The efficiency goes as the reciprocal of the SQUARE of the mass. Double the mass, efficiency drops by a factor of four. 2. The resonant goes as the reciprocal of the SQUARE ROOT of the mass. Double the mass, resonant frequency goes down by about 29% (0.71 time the original). 3. The total Q goes directly s the mass. Double the mass, and the damping doubles (i.e., it's LESS damped). Now, it's not precisely double, as it depends upon the ratio of the mechanical vs electrical Q, but if we're talking about drivers with reasonable pretention of high quality where the electrical Q dominates, then it's pretty much doubling. There is an known 12 dB/octave rolloff below resonant frequency For sealed box or infinite baffle systems which can be compensated for by means of application of an equalization boost or "inverse rolloff". Only to a certain point, the design of which is determined by the mechanical and electrical power handling of the driver. Is it the box volume, the box design, the driver, or a combination of all three which determines the resonant frequency to begin with? ANy second order mechanical system has a resonant frequency. By "second order mechanical system" I'm talking about a system composed of, in essence, a mass and a spring. Imagine a long spring hanging from the ceiling and attached to the end of the spring is a weight. Pull the weight down and release it, and the system will osciallt back anf forth at a very specific rate, determined by the mass of the weight (call it M) and the stiffness of the spring (call that K). The rate or frequency (call that F) at which it oscillates is uniquely determined by these two quantities alone and is calculated by: F = 1 / (2 pi sqrt(M/K) ) That's it. Now, in a loudspeaker driver, you have a mass, the cone and voice coil and other moving parts, and you have a spring, the suspension and centering spider. The effective mass of the cone (close to but not exactly the same as the mass you would get if you pulled the speaker apart and weighed these parts) and the mechanical stiffness of the surround and centering spider determine what the resonant frequency of the driver itself is. Put it into a sealed box, and the combined mechanical stiffness of the surround and the acoustical stiffness of the entrapped air raise the total stiffness of the system, and thus a woofer in a sealed box has a higher resonant frequency than the woofer in free air. The situation with a ported system is more complex because you're no longer looking at the entrapped air as a single acoustical element: a stiffness, rather your looking at the enclosure SYSTEM as a coupled dual-resonant system, with the driver's mass and stiffness as one resonant system, and the acoustical mass of the port and the acoustical stiffness of the entrapped air as another. What do you mean by "arguably worse transient performance"? For the purpose of this discussion, there is a unique link between the frequency response of the system and its transient behavior. All other things being equal, and assuming flat frequency response in the passband, the better the transient system. But, at the same time, the faster the rolloff, the worst the transient response. But things are seldom "equal," so there are many factors in determining the final system response. That's why I used the modifier "arhuably." ' |
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#37
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Seeking advice for buying home audio equipment
On Nov 20, 7:07 pm, "Peter Larsen" wrote:
Dave wrote: [subs with electrical frequency compensation] What do you mean by "arguably worse transient performance"? grossly oversimplified: the steeper the filter, the more ringing. So far so good. The longer you extend frequency response downwards the steeper the roll off will need to be, a probable target curve for such a system is a fourth or sixth order highpass at some lower frequency. Not so. Compensating for the rolloff of a 2nd order system, if the goal is a maximally flat response, will require a 2nd order equalizer, no matter HOW far you go down. The result will ALWAYS be a 4th order system. The only thing that might dictate a higher order response is what you want to do with the stop-band information. But that's a completely separate issue. |
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#38
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#39
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Seeking advice for buying home audio equipment
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#40
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Seeking advice for buying home audio equipment
On Tue, 20 Nov 2007 23:40:43 -0500, "Soundhaspriority"
wrote: This is very commonly read, but cannot in fact be true. The driven cone only makes a certain excursion and equal energy is given to each side of the cone's swept path. Volume excursion in the port is larger because area is smaller, but *observed* air movement is not a simple mulplicative indication of true acoustic output. I just want to add a little above. If the port and the cone are matched with equal efficiency to the air, no further qualification is required.But, in some designs, the port is itself in the shape of a horn. Polk does this; the downward firing port extends onto a shaped baffle. So the impedance matching through the port is much better than through the front of the driver. Conversely, in many designs, the port is poorly matched, in which case the output through the port may be negligible compared to the driver. Yeahbut, the mouth size of any commercial speaker's possible port is negligible. No horn effect can apply; anything very small WRT a wavelength is just an obstruction at best. My stronger point is that a moving piston generates equal energy to each side, irrespective of box design. Always; can't help it. No magic, even including a real acoustic horn on either side of the moving piston, can change the fundamental theoretical 50% conversion efficiency to either "face" of the piston, and only a resonant structure can take advantage of the opposite polarity energy from the "wrong" side of the piston, and then only over the resonant structure's range. So a design equalized for flat magnitude response (in a commercially viable compromise - this isn't a religious argument) trades some conversion efficiency over a small (less than an octave - but it's an expensive octave) range for some change, usually negative, in impulse response when comparing ported to sealed boxes and with both electronically equalized for flat passband magnitude. I actually *do* have a completely intuitive touchy-feely descriptive model of loudspeaker ports that I've used successfully over the years. It's totally rock-on-a-spring and customers and my install guys get it right away. Buy it's a separate post; not on the OP's dime. Much thanks, as always, Chris Hornbeck |
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