Room modes: absortion, bass traps, Eq, speaker position... what really works?

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Have you measured it? Behringer mic + phantom power amp / Holmimpulse SW will do.

I use two Anti mode DSP units on my Tapped horns. I had 15dB peaks and troughs before at volume and DSP certainly fixed them up to acceptable +/-5 dB in room at listening position.
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No connection with them other than satisfied customer.
The Anti mode I have is only good to 150Hz I think so meant for subs really.
SQ is good.
I believe they do a more comprehensive freq covering unit now. But that is a leap in cost and DSP the whole freq range.

I think proper bass traps would help too.
Something like the diagrams to be really effective.
RAM400-1000 Corner Bass TrapSound Acoustics

Depends how far you want to/can go.
 
first you need to measure your room, acousticly or dimension.
Find out if you have modes (lets call it response peaks).
If so use tuned bass traps or ressonators to damp these frequencies.
Then use as much diffusers as possible. Try as wide range as possible, back wall, sealing, side walls and front wall.
No high frequency absortion should be needed (sound will go dead without some reflections).
The end result should be incredible.
 
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Multiple subs would be a more complete solution but at the very least you could use one sub (could be smaller than 15"), covering your problem frequencies and working with the mains. Don't cross the mains, leave them as they are. Use the sub location, polarity and level to find an improvement.
 
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,,.
 
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.
 
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!
 
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.
 
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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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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.

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?
 
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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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