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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
amtprod's avatar
amtprod OP
108 posts
 

@erik_squires  See, I told ya!   ....you know....I genuinely (and you already know this) thought I was going absolutely crazy, especially the first listen when I got here.  He was beaming so proud and my first thought was ".....uh.......so are the woofers on a different amp?.......are you bi-amping?  Oh that's probably it, and you forgot to flip that amp on!......."   He has the grills on the speakers, so when he's not around I am going to pop it off and check and see.  In general though there is VERY LITTLE air coming from the dual ports on the back.  He is bi-wiring them from the Rega Illicit, and does not have the straps on the dual posts (usually not needed).

@mapman thanks for helping confirm my confusion too.  So the size of the room generates no real prominent nodes.  Honest to god, there is so little to no "bass" being generated that I walked around the entire space along all walls and floor and couldn't find a single spot that 'bloomed' or resonated or any note below 150hz that even sounded a tiny bit more prominent.  It's FREAKY!  Can you imagine sitting there listening to something 70x bigger than your own speakers (I have the Legacy Studio HDs in my little home living room) and you are listening to INFINITELY LESS BASS!!!  I'll post a pic of MY tiny living room's frequency response-just the bookshelf speakers. 

@simao my step father was an electrical engineer (microwave technologies) so he's pretty keen on things involving measurement and formulas, and Jim Smiths book was right up his alley. 

Legacy Studio HD Bookshelf Speakers-Tiny Living Room

erik_squires
16,243 posts
 

OP:

And I told you not to claim you had no bass problems until we got to them... 😂

Once you get your woofers pumping we may have to revisit that issue. 

amtprod's avatar
amtprod OP
108 posts
 

@erik_squires I KNOW I KNOW YOU WERE RIGHT!!!!!!!! 😆

I’m gonna sneak down and pop the baffles off when he’s in the shower, and I’ll for sure do another quick room measurement. Do you know is there any harm to an amplifier with bi-wiring AND having the terminal jumpers attached? I know the speaker wires are properly fully connected from amp to speakers (I double checked that first listen)...but I am so curious to determine if it’s possible that the woofers are somehow NOT connected (internally?!). Though at the same time I am preparing myself for things to all be working properly....  ~Alan

erik_squires
16,243 posts
 

SO, yes, straps and cables are fine, but you can do some more basic tests first.

Since you are bi-wiring it’s quite possible your problem is one speaker or woofer section is wired out of phase with the other. Check for that before attaching straps. That would explain the lack of bass and lack of room mode problems.

Some basic tests with a multimeter include making sure that the two paris of terminals at the end of the biwiring have perfect continuity (disconnect the amp first!) and that the woofer sections show around 3-16 Ohms. Not sure what it should be honestly, varies by speaker.

A 1.5 to 9V battery and wires can be used to test the woofer sections. Attaching + to + and - to - should have the woofers moving in the same direction, usually towards the listener. 9V is about 10 watts if the battery could actually deliver that much current (it can’t), so it’s generally safe. The battery voltage will sag long before you get to 10W. All 4 woofers should move in the same direction when tested this way.

amtprod's avatar
amtprod OP
108 posts
 

@erik_squires and @mapman I just popped the front grill off and ran a 60hz and 80hz tone thru the speakers, and they ’move’, but their output (volume) is like 1/2 of a 100hz tone. SO what you see in the REW graph is at least what I’m hearing and seeing in speaker movement. To get a similar volume, I have to really crank the volume.

 

@erik_squires I see what you are thinking: that potentially internal to the crossover there is one of the woofers that is hooked up out of phase (reversed)? I’ll see if I can test that without changing wiring or removing anything (I think I have an app that puts out a test tone and reads the phase output).  I also know how to do that battery test you mentioned with the 9V, I'll see if I can check that out as well to see if both are moving in and out together in sync. 

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