Sub location based on Room Simulation

[Weston Trimble]

Hi, I'm in new to REW and to audio measurements so please bare with me. I have two subs I have in my HT system (HSU VTF2 MK4) that I'm trying to find the best position for. I have a couple options, 1. Opposing corners of the room, 2. In between the LR channels around my TV. 3 Possibly one by my listening position and one in any corner.

I'm using the Room simulation to help me get started on the best place to put them however I'm getting interesting results when I enter in either 1 sub or 2 subs. It appears to me that going with 1 sub in my room has a better, more even response than using 2 subs. I'm looking specifically from 20 hz to 50 hz. With one sub I have peaks at 25 hz, 40 hz, and 50 hz.. where as with 2 subs, I only have a peak at 50 hz. this is with time align on and off. (Can someone help me out with what Time Align means necessairly, is it due to the distance difference from the listening position? How is it different than delay?) I know peaks don't mean a good room response ( may be the opposite) but I found it interesting that I was having peaks present and more dB at 20 -50hz frequencies with just 1 sub than 2.

Is my room better off with just one sub? Thanks for all the help. I'm drinking by the firehose now trying to understand this software and the best setup for myself. I'm using a Marantz SR7011 AVR by the way as well.

 

[John Mulcahy]

Time alignment (Align Subs Individually in REW) delays sub(s) to align the sound with the arrival time of sound from the furthest sub. In a rectangular room with subs placed symmetrically in the room time individual time alignment needs to be off (so all subs are producing the same signal at the same time) in order to obtain the cancellation of some modes that can produce. That kind of symmetrical arrangement also reduces the variation of response with position, so that applying some EQ to tackle the few remaining peaks within the subs' operating range would give results that produce a more uniform response over a larger area.

If you are relying on modal resonances to extend sub response then you may not wish to have the modal cancellation, but such a resonance-extended response would tend to heavily emphasise the frequency of the resonance.

 

[Weston Trimble]

Thank you for the explanation. So the Time Align is the same as the Delay entry, except that Time Align assigns a delay value automatically based on the two subs distance difference from the listening position?

Also is my analysis of the graphs I'm getting from the Room Simulation where using one sub in the corner produces better results than two subs?

 

[John Mulcahy]

"Better" depends on your criteria. If the aim is low frequency extension then modal support can be helpful, just put the sub in a corner and it will maximally excite the room's modal resonances. If the aim is to avoid the long decays of modal resonances and reduce response variation with position multiple subs are better.