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#1
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Porting of very small speaker cabinets
What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. I know there are some speaker experts here, but if there are other groups that deal with this type of thing, please advise. Thanks |
#2
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
"R" What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. ** That is a very small cabinet - less than 2 cubic feet. The way to "port" it is to make a shelf under the speaker. The front opening is full width, maybe 2 or 3 inches high with an internal partition about 10 inches deep. Adjust depth for best sound. ......... Phil |
#3
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
R wrote: What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. I know there are some speaker experts here, but if there are other groups that deal with this type of thing, please advise. Thanks Having a 12" speaker in a 1.1 cu.ft box is like having an elephant in the loungeroom; If it ****s, you ARE in trouble. I fear you are asking for solution which is impossible to easily provide. The speaker should be left alone. Perhaps placing a couple of polyester wool bats inside may tame reflections from inside the box the outside through the cone. A port may make things sound worse. Perhaps you should consider buying another to give a good reflex box match, or if you want a ported box with that driver you have, then you'd need to apply the speaker program WINisd which is a free download to find out ideal ported box design for that driver. I recently re-engineered a pair of AR12 with 10" bass drivers in 2 cu.ft.sealed boxes. Bass became more extended when i added a plinth of 3" under the exising box, and a port under the box of about 14" long. This way the port volume didn't make the internal box volume any smaller. Even the guy's wife thought the result was a marvel. The box volume was barely big enough for the driver to get a good match. Many makers used closed boxes because reflexed sounded worse, and besides, it was easy to lie to the public about bass performance, and save on construction costs, transport costs by keeping the box undersize, and not boring the extra port hole and fixing in a cardboard tube for the port. Speaker mass production is about marketting, not an application of very best practices at all times; best practices are something likely to send a maker broke, or most certainly likely to make the shareholders very unhappy. Patrick Turner. |
#4
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
R wrote:
What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. If the driver is good, why not build a larger box for it? If you _must_ modify it, try a slotted back approach, and provide some dampening across the slots. No matter what you do, you'll most likely end up with either a bumpy upper-bass ride or other artefects. As already mentioned here, the box is rather small for any changes. -- Kind regards, Mogens V. |
#5
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
On Mon, 05 Mar 2007 04:50:13 -0500, R wrote:
What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. I know there are some speaker experts here, but if there are other groups that deal with this type of thing, please advise. Thanks If this is a guitar amp speaker - just take the back off... replace it with a partial plate to hold the jacks... If it's for a synth or something - you need a bigger box! Of course, it also depends on the speaker... telling us the make and model and exact intended purpose would help... |
#6
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
On Mon, 05 Mar 2007 11:28:51 GMT, Patrick Turner
wrote: R wrote: What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. I fear you are asking for solution which is impossible to easily provide. Yeah, I knew that. I'm looking for any possible improvement. The speaker should be left alone. Perhaps placing a couple of polyester wool bats inside may tame reflections from inside the box the outside through the cone. A port may make things sound worse. The existing cabinets are closed, with internal polywool padding. They don't sound very good at all. Could be the particular speakers (I've tried Altec 417s and EV SRO's ...see below). I was considering just sawing out the entire back to let the speaker at least breathe, though the baffle size would not lend to spectacular sound. That's a drastic measure, and of course could have its own set of problems. So I'm looking more for any interim compromises before doing that. The ports, as suggested elsewhere, Perhaps you should consider buying another to give a good reflex box match That would be ideal, but unfortunately there is not enough space. That was the reason that these cabs exist in the first place. The two speakers mentioned (Altec 417, EV SRO) are/were not available in smaller sizes, so 12" is it. Again, the purpose is for nonlinear musical instrument monitoring, mostly guitar, so exact linearity is not imperative. Fender Deluxe Reverb amps get by with open-back cabs with just a bit more baffle area than these. But again, I thought there may be a better way than completely opening the backs. , or if you want a ported box with that driver you have, then you'd need to apply the speaker program WINisd which is a free download to find out ideal ported box design for that driver. There's a good lead, thanks! I just tried the program. Strange results (unexpected linearity!), so I'm probably doing something wrong. I started with the ALtec 417, as they did not have Theile-Small presets for EV SRO speakers (old alnicos with large white 'coffee can' magnet...anyone know the T-S params?). Entered approx 15" x 15" x 14" for size, using both ported and unported models. In all plots, the response is surprisingly UNpeaky, with an expected bass cutoff at around 80hz to 100hz. Bass for guitar doesn't really need to extend below 80hz, so that is not a concern. I don't understand why the program indicates reasonable response in other respects though. I had expected drastic resonant peaks in low mids. That's what the closed cab sounds like anyway. Also, vent lengths show as a fraction of an inch, no matter what size vent I specify. Thanks, Patrick |
#7
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
On Mon, 05 Mar 2007 18:01:59 +0100, "Mogens V."
wrote: R wrote: What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. If the driver is good, why not build a larger box for it? The speakers themselves are great for what I want to do. Unfortunately, there is limited space for the cabinets in this particular case. If you _must_ modify it, try a slotted back approach, and provide some dampening across the slots. No matter what you do, you'll most likely end up with either a bumpy upper-bass ride or other artefects. I'm not familiar with slotted back. Are there examples somewhere? As mentioned in a previous post, I tried WinISD at the suggestion of Patrick. It shows surprisingly smooth rolloff curves for some reason. Again, I must be entering some wrong params, as the actual sound is about what you indicated, with peaky sounding low-mid/upper bass. |
#9
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
R wrote: On Mon, 05 Mar 2007 11:28:51 GMT, Patrick Turner wrote: R wrote: What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. I fear you are asking for solution which is impossible to easily provide. Yeah, I knew that. I'm looking for any possible improvement. The speaker should be left alone. Perhaps placing a couple of polyester wool bats inside may tame reflections from inside the box the outside through the cone. A port may make things sound worse. The existing cabinets are closed, with internal polywool padding. They don't sound very good at all. Could be the particular speakers (I've tried Altec 417s and EV SRO's ...see below). I was considering just sawing out the entire back to let the speaker at least breathe, though the baffle size would not lend to spectacular sound. That's a drastic measure, and of course could have its own set of problems. So I'm looking more for any interim compromises before doing that. The ports, as suggested elsewhere, Perhaps you should consider buying another to give a good reflex box match That would be ideal, but unfortunately there is not enough space. That was the reason that these cabs exist in the first place. The two speakers mentioned (Altec 417, EV SRO) are/were not available in smaller sizes, so 12" is it. Again, the purpose is for nonlinear musical instrument monitoring, mostly guitar, so exact linearity is not imperative. Fender Deluxe Reverb amps get by with open-back cabs with just a bit more baffle area than these. But again, I thought there may be a better way than completely opening the backs. , or if you want a ported box with that driver you have, then you'd need to apply the speaker program WINisd which is a free download to find out ideal ported box design for that driver. There's a good lead, thanks! I just tried the program. Strange results (unexpected linearity!), so I'm probably doing something wrong. I started with the ALtec 417, as they did not have Theile-Small presets for EV SRO speakers (old alnicos with large white 'coffee can' magnet...anyone know the T-S params?). If you don't have the TS parameters, or know the fiddly way to measure them using a known volume sealed box of about 2cu ft, you are stuck. Entered approx 15" x 15" x 14" for size, using both ported and unported models. In all plots, the response is surprisingly UNpeaky, with an expected bass cutoff at around 80hz to 100hz. Bass for guitar doesn't really need to extend below 80hz, so that is not a concern. Just what real world response you might get is anyone's guess all the same. The subjective "constricted tone" is probably due to the harmonics and tones well above the bass F where the box size s important. I don't understand why the program indicates reasonable response in other respects though. I had expected drastic resonant peaks in low mids. That's what the closed cab sounds like anyway. The WINISD only really gives some idea for box matching in the critical area below 100Hz. The makers response plots for real world F response are never factored in to the driver data. Also, vent lengths show as a fraction of an inch, no matter what size vent I specify. The program says you don't need more than a hole in the cabinet wall. Not every speaker needs a long port, but if one is added, the box resonant F goes lower as the port L reduuces. I am surprised with the results you have got, and that there isn't a peaky response indicated between 100 and 50Hz, and that a long port isn't needed. You can select different port lengths and box sizes, or show sealed or vented for the same driver. Patrick Turner. Thanks, Patrick |
#10
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
R wrote:
On Mon, 05 Mar 2007 18:01:59 +0100, "Mogens V." wrote: R wrote: What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". If you _must_ modify it, try a slotted back approach, and provide some dampening across the slots. No matter what you do, you'll most likely end up with either a bumpy upper-bass ride or other artefects. I'm not familiar with slotted back. Are there examples somewhere? As mentioned in a previous post, I tried WinISD at the suggestion of Patrick. It shows surprisingly smooth rolloff curves for some reason. Again, I must be entering some wrong params, as the actual sound is about what you indicated, with peaky sounding low-mid/upper bass. Slotted back is fairly non-critical. Just drill a series of half inch holes or so at the length of, say, 4-5 inches, and cut the wood between them to have a slot. Doesn't have to be a perfect slot. Repeat to have 4-5 slots. You can dampen the slots with some mineral wool or such to tune the effect domewhat. Since you've already mostly made up your mind to cut off the back, maybe try the slots first. If you do cut cut off the back, do note that an open baffle box require a speaker with a somewhat stiff suspension and a not too weak magnet (I do't know your Altec driver), else you may have excessive cone movements - especially if you crank up the bass and play staccato bass strings notes while dampening strings with the hand. This technique can produce sound somewhat below the E6 80hz string. -- Kind regards, Mogens V. |
#11
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
On Tue, 06 Mar 2007 01:40:53 -0500, R wrote:
On Mon, 05 Mar 2007 22:32:26 -0500, wrote: On Mon, 05 Mar 2007 04:50:13 -0500, R wrote: What is the best way to port a -very- small cabinet? It is about 16"x16" across the baffle side. 14" deep. The speaker itself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep the speaker from sounding constricted, as it does with a closed cabinet. I know there are some speaker experts here, but if there are other groups that deal with this type of thing, please advise. Thanks If this is a guitar amp speaker - just take the back off... replace it with a partial plate to hold the jacks... Yes, primarily for guitar, and I was just going to saw the backs of the cabinets out (they are one piece. Speakers are front-mounted). The cabinets are actually hooked into a stereo tube amp with relay-switched preamp circuits. I'd like to keep it as versatile as possible, considering that it could be useful for keyboards, etc. Still I'd sacrifice some low-end response to keep sharp resonance minimized. It would be great if I could get a handle on things via computer modelling, but I don't think the response curves that I've got from WinISD so far are representative of what's actually happening. If it's for a synth or something - you need a bigger box! Of course, it also depends on the speaker... telling us the make and model and exact intended purpose would help... I originally tried Altec 417-C's. Changed to EV SRO speakers. Both are old huge-magnet alnicos that are long obsolete. I believe the Altecs were sometimes used in hifi gear at one time. Not sure about SROs. Both are great speakers, and both weigh close to 25 lbs (Altec a bit lighter I think). I have speakers like that, and believe me, they are only good for guitar! The only box you could use them in to get bass would be a 10 cubic foot bin, a total waste of time I think, since the bass wouldn't be very impressive. Those speakers are resonant up around 50 or 60 Hz, you could beat them with a modern 8". I'm sure you've seen the SROs. Similar to the ones from this Ebay auction: http://cgi.ebay.com/ws/eBayISAPI.dll...m=160085867944 There was a preset in WinISD for an Altec 417 model, though I believe it may have been one of the later ceramic models. No luck with the EV SRO (it did have later ceramic EV models). You'd think that would have been there, given the legendary status of SRO speakers. Win ISD won't be of much help, you need different speakers if you want a full range small box. I'd suggest you sell them to a guitarist and then get something full range. Or keep tham for your guitar and get a sub for other uses. |
#12
Posted to rec.audio.tubes
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Porting of very small speaker cabinets
On Mar 5, 6:28 am, Patrick Turner wrote:
R wrote: What is the best way to port a -very-smallcabinet? It is about 16"x16" across the baffle side. 14" deep. Thespeakeritself is 12". This is intended for use with musical instruments, so absolute flat response is not necessary. I'm primarily looking for any way to keep thespeakerfrom sounding constricted, as it does with a closed cabinet. I know there are somespeakerexperts here, but if there are other groups that deal with this type of thing, please advise. Thanks Having a 12"speakerin a 1.1 cu.ft box is like having an elephant in the loungeroom; If it ****s, you ARE in trouble. I fear you are asking for solution which is impossible to easily provide. Thespeakershould be left alone. Perhaps placing a couple of polyester wool bats inside may tame reflections from inside the box the outside through the cone. A port may make things sound worse. Perhaps you should consider buying another to give a good reflex box match, or if you want a ported box with that driver you have, then you'd need to apply thespeakerprogram WINisd which is a free download to find out ideal ported box design for that driver. Of course, the driver must be tunned with proper box size and port dimensions, if the driver is suitable for ported boxes. Adding stuffing is most always done, otherwise it sounds like hell. Fiberglass and foam have the most impact on internal damping. Polyester is not as effective. Open boxes relieves the need to damp interior surfaces. greg |
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