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Room Acoustics, minimal treatment and measurements

Afternoon all.  Thought this might be helpful to some with wondering if room treatments can help with your 2-channel, and how to help visualize and measure what you may not fully grasp hearing wise.  I am just using a Mac Laptop and cheapo microphone, and REW, and 6 insulation panels.

This is my Step Fathers system, and pretty much empty LARGE  basement listening space.  There is a LOT of echo-reverb-ringing that (to my ears) over excites mid to upper frequencies, like being in a busy store/restaurant. With music, this can in ways help make a recording sound like it's in a larger studio/hall/space, but it also mashes a lot together and can over-color the music.  This results in lost focus and change in ACTUAL recorded acoustics: so an intimately microphoned musician will sound like an empty room, where an empty room sounds like an empty gymnasium.  This, also over-washes a bit of the mid-range and higher bass-losing it's tone and timbre.    Major thanks to @erik_squires who has been gracious to help with this process with dead-on advice.

FULL BASEMENT MEASUREMENTS:
34'long x 22'wide x 10'high

LISTENING AREA MEASUREMENTS:

15'long x 22'wide x10'high

Empty room, no treatments and RT60 plot.  Listening seat is *in the middle of the whole basement space, under an 18" boxed beam.*

 

"Treated" room, with RT60 plot.  Notice the overall mid-upper frequency taming from 700ms of "ring/decay", to 500ms.  Even with this, if you snap your fingers, you still hear a flutter echo.  This is from the whole other half of the basement room behind me, mostly.


Crude room response measurement:



Sketch and measurements of where things are in the listening room:


I hope this is helpful and gives you some things to try out that don't cause major disruptions to your system, until you really determine if and where your issues are and then you can buy and mount things.  My next step is to see where ON the walls I can place absorbing panels, and how many might be needed for a nominal improvement.  My thinking is the bigger issues are the ceiling, front wall, and then 'filling' the space behind the seat just to eat up ambient stray ringing.
 

128x128amtprod
mapman's avatar
mapman
22,308 posts
 

Always a good idea to make sure the mains are operating properly before adding subs. So if bi-amping with EQ is what is neded for that, definitely do that first and see where you land. What make and model are the speakers again? If they turn out to be too problematic in that room at some point, it may be time to look at alternatives that might be implemented to their fullest more easily. It really all depends on what the end goal is. Also of course how much time and money you are willing to invest.

 

Also I would say that you are starting out with a much larger than normal bass deficiency.  Can optimizing the speakers alone resolve that?   Probably to some extent.  THen from there its a question of is that good enough or time to add powered subs to finish things off.

erik_squires
16,138 posts
 

If this was my system, I'd bi-amp, using a miniDSP as an active crossover in front of the amps.  It sounds really good.  This is going to give you the ability to properly high pass the mid-woofers, low pass the woofers, which will improve off-axis imaging and overall smoothness, give you a lot of extra headroom AND let you equalize the 12" drivers to function as subs.  Also, I'd plug the ports, which will raise the -3 dB a little, but also slow down the rolloff below 100 Hz significantly.

Fortunately, plugging the ports just takes a pair of clean socks.  I suggest organic cotton ... :D  Really anything that closes the ports and doesn't get lost. 

You may seriously want to try plugging the ports and re-measuring anyway.  You may find this extends the bass in just the right way.

erik_squires
16,138 posts
 

OP:

To confirm what I thought I read in the polish site, can you measure the frequency response for 1 speaker 45 degrees off axis? 1 to 2 meters away (3 to 6’) is fine. I want to see if there’s a major dip there.

If you see a big dip, unplug the woofers and see if it vanishes.

Thanks!

 

Erik

amtprod's avatar
amtprod OP
106 posts
 

@erik_squires   Yea I'll do a sweep to see that potential dip.  Are you thinking there's some frequency cancelling happening or a cross-over issue? 
I've read up on MINIDSP and watched a bunch of videos on their use.  I think things like DSP is a MAJOR step forward in music reproduction (which yes can also be over done).  I  agree with you though I would still do all the heavy lifting with proper room treatment (regardless of speakers or equipment), then concentrate on "better" speaker placement for a better balance of frequency response and sound staging.  Then, the DSP "should" only need to do really minor adjustments and moves which will keep all the best qualities of all aforementioned aspects.  I would 100% bi-amp:  that would be another HUGE increase in audio quality and presence..

Morning @mapman .  The speakers are (now) 4 year old Legacy Focus SE, (link below).  From all I have seen so far, the woofers are working properly---but I want to try running pink or white noise thru them and measuring what the voltage is at/on the speaker terminals (inside the speaker).  I am 100% certain there is no way dad would change them for anything else.  Again, to him, things sound perfectly fine but he isn't aware of how much the basement is swallowing the sound.  What is that saying about how humans bias their hearing....?  😆  With that much bass fall off, honestly the only thing to fill that void would be subs.  Bi-amping and obviously making those best practices of balancing proper speaker placement for frequency response AND sound staging combined with proper room treatment all needs to be exercised FIRST.  He's locked himself into one aspect: most accurate "best soundstaging" based on room dimensions.  (I think I'm assessing that right?).

 

 

erik_squires
16,138 posts
 

@erik_squires Yea I’ll do a sweep to see that potential dip. Are you thinking there’s some frequency cancelling happening or a cross-over issue?

If there is no bass to mid-bass crossover, then I expect destructive interference (frequency dips) somewhere, either horizontally or vertically. I also expect the 7" drivers would sound much better if not trying to reproduce 20 Hz.

It may be worthwhile talking to Legacy and asking if the woofers actually have a low pass filter. Your measurements, and the impedance charts from Poland suggest the answer is no.

The way to tell without opening your speakers is with an impedance sweep. REW has a way to do this if you make a custom jig, or you can purchase Dayton DATS. Measure the combined impedance, and separately. Take a look at this blog post to understand "High pass impedance" and "Low Pass Impedance"

 

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