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

[AllenB]

@ Earl, I'll take this to the other thread.

Originally Posted by murillollirum

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?

The room can not see the difference. Yes, view them as energising the room as a sub might. You'll be limited by their placement options. A separate sub (at least) would be a good move IMO. The powerpoint presentation would make a good read if you haven't already.

[markus76]

Originally Posted by AllenB

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.

EQ still would be better than doing nothing.

[markus76]

Originally Posted by 1audiohack

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.

Below the lowest mode a room behaves like a pressure chamber but this is irrelevant for the discussion. The lowest mode for a room of 4x5x2.5m is 34Hz. It will be lower the bigger the room gets.

[markus76]

Originally Posted by murillollirum

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?

The best locations for subs is not necessarily where the mains are. Mains should be placed for best imaging, subs should be placed for lowest point-to-point differences within the listening area. Best case they also act as active absorbers, reducing modal ringing.

[markus76]

Originally Posted by gedlee

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!

Hi Earl,

That's some nifty software you got there. Did you also look at how modal decay is affected by the process?

[AllenB]

Originally Posted by markus76

EQ still would be better than doing nothing.

It would, but we've all been there. Those days are behind me, hallelujah...but we are on the same page Markus.

[gedlee]

Originally Posted by markus76

Hi Earl,

That's some nifty software you got there. Did you also look at how modal decay is affected by the process?

Thanks - no I did not look at the modal decay, but I suspect that it being a minimum phase system, as the frequency response is made smoother the modal decay will follow suite.

[markus76]

Originally Posted by gedlee

it being a minimum phase system

John Mulcahy (author of REW) has shown that this is not always the case: Minimum Phase

[Joel Wesseling]

If you want the best solution IT IS BASS TRAPS.. Most people are simply using inferior commercialy driven products that arent very effective or do nothing at all..(ie)light weight foam wedges.. EQ is a good tool to show improvement for the problem but bass traps will sound better by reataining your systems characteristics..

The challenge is you need many bass traps including ones with High Density Insulation(2lb per cubic foot) and 1/8" and 1/4" thick panel traps.. I'm planning a room for a friend based on this were the traps are built into the new framed wall and ceilng with alternating insulatiuon trap and panel trap..

In an existing room you might need 20 or 30 large 4" thick traps plus some panel traps and this is were the problem is as most will get a few and wonder why there isnt a big improvement and give up.. the waves are large and need to absorb going in and absorb refected wave coming out.. Then there's the cosmetics but making then yourself will help..Mine are diy wood frame and fabric covered.. Picture shows 4 traps spaced apart from each other behind the speaker and attached to back wall is a wood panel trap to reduce even more energy that otherwise will come off wall strong..Room has 20 plus bulk heads and Absorbers hidden in ceiling behind fabric..

My room was measured with ETF and Cal Mic and watched and listened to the response smooth out and the ringing stop and now listen to recordings a better way.. Audio Keen People that listen in my room find it a complete JOY with the Focused soundstage and spatial information and balanced bass.. When turned up It's loud in the soundstage and not loud in the room if you know what I mean..

Off Topic some what but If you were to consider this than the rooms diffused energy will have to be considered and theres 2 camps on this.. Some want some or a lot and others want none or very little.. most recordings already have ambient information built in, fake, or real and this built in information revealed more in a more dead configuration..

If you follow Ethan Winer on other forums, he has a deep understanding of this topic and helpful.. I read his comments with passion but watch some get scared away as he also sells treatments so could be taken as a sales pitch if he says you need more bass traps by I chuckle inside becasue I know he"s being honest and it's driven by passion..

Cheers, Joel

[gedlee]

That there could be frequencies that the system is not MP is possible. That these are a dominate issue at LF is improbable. Hence "in general" flattening the response minimizes the decay.