[D OB G]

I got Linkwitz’s tone-burst CD some time ago to use to identify discrete LF resonances.

My usual technique to correct the bass is to take an average of the impulses of each speaker from a number of locations around the general listening area, and then sum them (there are four sources of LF- two being sealed subs).
This acquires both FR and phase information.
Even though each channel can be equalized to have a generally flat FR, obviously the summed response will show room induced in-phase peaks, which then need to be EQd as well.
The usual measuring techniques lose resolution with lowering freq, so there are limitations.
This is where the discrete tone-bursts can reveal very narrow room resonances. 

I’m using minidsp below 400 Hz.
I can get quite a flat response with each speaker when measured at say 1-2m.
But it occurred to me, just today, that its’ capabilities might help with the inevitable degradation to the imaging and ambience that occurs because my room is quite asymmetrical.
I have the speakers 2.2m out from the wall behind them, but they are not centred on the long axis of the room. There is furniture nearby, and also between my chair and the speakers (also not symmetrical).
So I’ve been aware that front and rear radiation is spraying all over the place.
(Genuflection to those with symmetrical rooms).

By using the considerable EQ ability for each channel (24 points in total), and the 4Hz stepped tone-bursts on the CD, I was able place each freq absolutely in the centre (obviously only applies to the specific listening position).

What a difference!!!
Linkwitz announces each freq, and with each progressive correction his voice gets tighter and clearer. 
This translates to all the improvements to music that you would imagine.

Regards,
David

[studiotech]

My setup is not symmetrical either, with one speaker right against a side wall while the other is 4ft away.  Judicious use of absorption at that point AND EQ to try to match the L/R balanced helps a ton for better, more stable imaging.  There is such a stigma against any form of processing and EQ in the audiophool world, but in many cases their benefit far out-ways what amounts to a very subtle if any degradation of the sound.  Active is the way to go given the low cost of entry nowadays for decent DSP and amplifiers.

Greg

[D OB G]

Also, I’m open-baffle below that 400Hz, with a sealed 6” above that, and then a 6” waveguide from 2.2kHz.
Even in the compromised room, above 400Hz there was no need to EQ at all (only the DEQX goes above that).  All freqs were exactly centred.  Which seems to suggest that forward radiation is a minor (non-existent?) issue in my set-up.

David