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Old 7th February 2013, 08:05 PM   #11
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The only way EQ can reduce peaks measured in the room that do not exist in the speakers native response is to reduce the energy coming from the speaker in the frequency band of interest. This is a compromise at best, yes it may tame the magnitude of the room response peaks, but that comes at the expense of reducing the dynamics and ballance of a presumably acurate and ballanced speaker. You're just not putting the energy that agrivates the room into the room.

Using a frequency domain solution for a time domain problem is at best a bandaid, maybe better than nothing but,,.
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Old 7th February 2013, 08:19 PM   #12
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Originally Posted by 1audiohack View Post
The only way EQ can reduce peaks measured in the room that do not exist in the speakers native response is to reduce the energy coming from the speaker in the frequency band of interest. This is a compromise at best, yes it may tame the magnitude of the room response peaks, but that comes at the expense of reducing the dynamics and ballance of a presumably acurate and ballanced speaker. You're just not putting the energy that agrivates the room into the room.

Using a frequency domain solution for a time domain problem is at best a bandaid, maybe better than nothing but,,.
We're talking about acoustically small rooms, right? 80Hz is 4.3m, 40Hz is 8.6m, 20Hz is 17.2m. There is no direct sound at those frequencies. Reflections from walls hit our ear before it even gets the chance of hearing a full period of a direct sinewave. Our hearing needs to be exposed to several cycles to even perceive pitch. What we hear at these low frequencies in acoustically small rooms is the steady-state response hence the time domain at those low frequencies becomes meaningless.
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Old 7th February 2013, 08:28 PM   #13
gedlee is offline gedlee  United States
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Markus - quite correct

there is a new presentation on multiple subs at Loudspeakers It has my latest thinking on this topic.

Multiple subs to smooth out the spatial response and independent EQ to smooth out the frequency response. The net result always turns out to be very good. Problem solved!

The thing is that this approach often needs a lot of EQ and many subs lack the headroom for 10 dB differences in gain across the bandwidth. Its not usually a "power" problem, but it is a voltage problem. Large peak voltage gains at one frequency can wreak havoc on plate amp subs.

PS. Markus - I still owe you a response from some time ago - maybe someday!
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Old 7th February 2013, 08:29 PM   #14
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Originally Posted by markus76 View Post
EQ can effectively deal with peaks (and dips to some extend) caused by room modes below about 100Hz.
Here're 3 articles worth reading: Bass Integration Guide – Part 1
No, it can't. EQ is only useful for tweaking the overall response shape of bass units (which IS helpful, though), and the article you linked to agrees.

EQ out a modal peak at one location, and you've increased a null at another location. EQ out a null at one location (actually impossible if it's a bad one), and you've increased a peak somewhere else and drastically decreased the dynamic capability of your system. It's chasing your tail with the wrong tool in hand.

Last edited by dumptruck; 7th February 2013 at 08:31 PM.
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Old 7th February 2013, 08:36 PM   #15
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EQ out a modal peak at one location, and you've increased a null at another location. EQ out a null at one location (actually impossible if it's a bad one), and you've increased a peak somewhere else and drastically decreased the dynamic capability of your system.
Only true if spatial variations are large but multiple low frequency sources can reduce those variations significantly hence equalization will improve a whole area and not just a single point.
Regarding dynamic capabilities, yes, subs need to be able to move lots of air.

Another approach is to use low frequency sources in the near field. Please see Comparison of different near field and far field subwoofer configurations
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Old 7th February 2013, 09:38 PM   #16
AllenB is offline AllenB  Australia
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What we hear at these low frequencies in acoustically small rooms is the steady-state response hence the time domain at those low frequencies becomes meaningless.
Maybe so, but it looks as if you may have missed the initial point, even if it wasn't stated that in a poorly damped room with a single source, EQ will be struggling.

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Originally Posted by gedlee View Post
Multiple subs to smooth out the spatial response and independent EQ to smooth out the frequency response. The net result always turns out to be very good. Problem solved!
Can multiple source configurations behave more or less constructively than each other?, ie: in the case of a poorly damped room with low spatial variation, the multiple sources may drive the entire room into resonance, increasing the apparent level versus the power supplied due to the entire room ringing...yet could another multiple source setup driving a similar room be phased/located to produce less ringing (by the sources counteracting (constraining?) each other) and creating less total room power than the first case vs room input power? Would there be a noticeable difference?

Last edited by AllenB; 7th February 2013 at 09:42 PM.
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Old 7th February 2013, 11:30 PM   #17
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You should definitely watch the SMWTMS "Earl Geddes on Multiple Subwoofers in Rooms" video:
Earl Geddes on Multiple Subwoofers in Rooms, smwtms Captured on Ustream:Earl Geddes on Multiple Subwoofers in Small Rooms, plus a CES Report, and New Faces...

Along with the PowerPoint slides: (as they go by fast in the video)
http://www.gedlee.com/downloads/Opti...l%20Rooms.pptx

Note that the PowerPoint is a .pptx

and as above (post #13):
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Old 8th February 2013, 12:25 AM   #18
gedlee is offline gedlee  United States
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Can multiple source configurations behave more or less constructively than each other?, ie: in the case of a poorly damped room with low spatial variation, ...
A poorly damped room would have a very high spatial variation - since your assumption is incorrect, the rest of the discussion is moot.
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Old 8th February 2013, 01:23 AM   #19
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Originally Posted by markus76 View Post
We're talking about acoustically small rooms, right? 80Hz is 4.3m, 40Hz is 8.6m, 20Hz is 17.2m. There is no direct sound at those frequencies. Reflections from walls hit our ear before it even gets the chance of hearing a full period of a direct sinewave. Our hearing needs to be exposed to several cycles to even perceive pitch. What we hear at these low frequencies in acoustically small rooms is the steady-state response hence the time domain at those low frequencies becomes meaningless.
In feet, 565/ RLD (Speed of Sound divided by the Room Largest Dimension) is the lower limit of standing wave possibility. Below this, the room can have no influence. You are in the direct pressure zone. In this zone there can be no ringing or "steady state", the pressure is uniform throughout the room.
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Old 8th February 2013, 01:58 AM   #20
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I just wanna make it clear, I do NOT have a sub, I hace two speakers with a 15 inch woofer each! Do they act like 2 subs? is it necessary to a add a real sub for a multiple sub configuration and dealing better with the room modes?
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