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#1
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Subwoofer Optimizer System
Saw this on Speaker City's web site.
http://www.speakercity.com/Sos/SubwooferOptimizer.shtml According to them: The Automated Controlled Environments, inc. Subwoofer Optimizer System (SOS) is an automatically calibrating, subwoofer optimization component, that acts to attenuate an audio system's major room mode resonance to provide significant improvement in measured and subjective bass system performance. After installation and calibration, your system will have a more linear frequency response, bass evenness, tightness, extension, and improved sound clarity. Anybody ever try anything like this? Comments, criticisms? |
#2
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I did a mini-review on this in Stereophile and Tom Norton did a more
extended one some time back in Guide to Home Theater (now Ultimate A/V). The key issue is that it is a single band EQ and will do great if(!) all you need is a single band of correction. Worked for me. Kal On 25 Nov 2004 15:59:33 GMT, "Michael McKelvy" wrote: Saw this on Speaker City's web site. http://www.speakercity.com/Sos/SubwooferOptimizer.shtml According to them: The Automated Controlled Environments, inc. Subwoofer Optimizer System (SOS) is an automatically calibrating, subwoofer optimization component, that acts to attenuate an audio system's major room mode resonance to provide significant improvement in measured and subjective bass system performance. After installation and calibration, your system will have a more linear frequency response, bass evenness, tightness, extension, and improved sound clarity. Anybody ever try anything like this? Comments, criticisms? |
#4
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#5
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I tried an experiment yesterday. With considerable difficulty, I put
one of my sub woofers in my usual listening position. I then played the bass tones from a Stereophile test CD and using my trusty Radio Shack meter, moved around the room. I found that at 40 hz, the corner position (where I had two of the subs) had a big suck-out. The side wall (next to my listening position) had the best response. At 60 hz, the corners were best. So, it seems you really need several subs to get the best results! A 1/3 octave equalizer could best be used to smooth out peaks caused by room resonances. ---MIKE--- |
#6
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#7
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"---MIKE---" wrote in message
... I tried an experiment yesterday. With considerable difficulty, I put one of my sub woofers in my usual listening position. I then played the bass tones from a Stereophile test CD and using my trusty Radio Shack meter, moved around the room. I found that at 40 hz, the corner position (where I had two of the subs) had a big suck-out. The side wall (next to my listening position) had the best response. At 60 hz, the corners were best. So, it seems you really need several subs to get the best results! A 1/3 octave equalizer could best be used to smooth out peaks caused by room resonances. I recall a post from Jim Johnston on RAO where he said that the typical room should really have 3 subs for best bass. |
#8
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Your method is the one I use. But, when you run 3 subwoofers at the
same time, you have to account for their interaction, which gives you new set of anomalies. FWIW In the room I currrently use, I have to use a 200hz crossover frequency because the room has nodes around 160hz that are excited to intolerable masking by the non-subwoofer channels. I never considered such a high crossover frequency until now, but it seems to clear up many of my problems. On 30 Nov 2004 23:58:02 GMT, (---MIKE---) wrote: I tried an experiment yesterday. With considerable difficulty, I put one of my sub woofers in my usual listening position. I then played the bass tones from a Stereophile test CD and using my trusty Radio Shack meter, moved around the room. I found that at 40 hz, the corner position (where I had two of the subs) had a big suck-out. The side wall (next to my listening position) had the best response. At 60 hz, the corners were best. So, it seems you really need several subs to get the best results! A 1/3 octave equalizer could best be used to smooth out peaks caused by room resonances. ---MIKE--- |
#9
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Michael McKelvy wrote:
"---MIKE---" wrote in message ... I tried an experiment yesterday. With considerable difficulty, I put one of my sub woofers in my usual listening position. I then played the bass tones from a Stereophile test CD and using my trusty Radio Shack meter, moved around the room. I found that at 40 hz, the corner position (where I had two of the subs) had a big suck-out. The side wall (next to my listening position) had the best response. At 60 hz, the corners were best. So, it seems you really need several subs to get the best results! A 1/3 octave equalizer could best be used to smooth out peaks caused by room resonances. I recall a post from Jim Johnston on RAO where he said that the typical room should really have 3 subs for best bass. Harman-Kardon has studied the use and placement of single and multiple subs systematically -- see http://www.harman.com/wp/index.jsp?articleId=1003 -- -S Your a boring little troll. How does it feel? Go blow your bad breath elsewhere. |
#10
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Nousaine wrote:
Try this at low frequencies where the wavelength is measured in feet (for example 10-feet at 100 Hz and 20 feet at 50 Hz and 50 feet at 20 Hz) you'll get significant changes in pressure at any given location relative to another. And because most nominal sized rooms have a volume that allows only the development of 5 modes below 100 Hz you'll find that the real problem is that there aren't enough modes at low frequencies to deliver even sound pressure distribution. Isn't the solution mode-cancellation? Well, that would seem to be so at first glance but its more complicated than that. The modes in any space carry the energy and while it's fairly easy to attain adequate loudness at high frequencies it gets progressively more difficult to do so at low frequencies. For example the speaker displacement required to attain a given SPL quadruples for every octave lower. For example to obtain a maximum SPL of 105 dB at 100 Hz (the reference THX level) might require an 8-inch speaker with 12 cubic inches of peak-peak displacement. To maintain this level at 25 Hz will require 195 cubic inches and 12 Hz requires 780 cubic inches or about the same as 2.2 small block Chevy V8s. What's the displacement of a 12mm clean stroke 12-inch woofer? About 44 cubic inches assumimg the amplifier will drive the soeaker to full displacement at any given frequency. So it becomes pretty to see that speaker displacement is a major issue with subwoofers. This gets really problematic if you start cancelling modes that are maintaining the energy. The best alternative with a single subwoofer is to maximize the excitation of all possible modes and the only location that will do that is closed corner. Even then Sound Pressure won't be perfectly even in most listening locations but it will allow you to put less energy selectively into the room at offending frequencies where there may be peaks instead of in large low frequency blocks. In all, with a single subwoofer corner placement will nearly always be optimal. I do not support this statement. For me the room corners are the optimal place to put absorbers for those few low frequency room modes. These can be either Helmholtz- or plate-absorbers. I move the subs 1/4 of the short and 1/3 of the longer side into the room, my listening position is almost in the middle. In the corners the sound becomes too boomy IMHO. Important is also a symmetrical placement. I find two subs to be sufficient, but 4 are a bit better if you like music with low frequency content. -- ciao Ban Bordighera, Italy |
#11
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#12
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#13
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Nousaine wrote:
A number of years ago I response mapped 13 rooms with a MLSSA system as to subwoofer location relative to the primary listening position using the reciprocal microphone technique (woofer in listening position; microphone in possible subwoofer locations) used by the owners. In every case except one a closed corner (at least 5-feet of wall to each side of the corner) provided the smoothest in-room response. [snip] The best alternative with a single subwoofer is to maximize the excitation of all possible modes and the only location that will do that is closed corner. Even then Sound Pressure won't be perfectly even in most listening locations but it will allow you to put less energy selectively into the room at offending frequencies where there may be peaks instead of in large low frequency blocks. In all, with a single subwoofer corner placement will nearly always be optimal. I'm curious, Tom whether you've had the opportunity to perform similar response mapping of rooms with multiple subs? Reason I ask is not only because your description above seems almost conspicuously focussed on single subwoofer systems, but also because I've had at least three separate acoustic consultants (none of whom had a vested interest in selling subwoofers) tell me that the best way to overcome modal-induced anomalies & get smooth low frequency response is via multiple subs distributed around the room. Note also that none of these professionals advocated the 1/4 distance or 1/3 distance from the walls or corners that I've seen various folks on Usenet or other internet discussion groups advocate. They instead recommended four subs located in either the center of each wall (equidistant between corners), or directly in each corner. |
#14
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