Great results with speaker adjustments using Room EQ and a calibration microphone.

After countless frequency sweeps this afternoon I think I have my speakers pretty darn near optimally placed.

The calibration microphone and XLR USB preamp was definitely worth the $200 to be able to run these comparison.

Small tweaks to distance from the front wall, distance apart, toe in and finally tilt made an overall pretty noticeable difference.

I also tweaked the bass adjustment knob a bit turning it down a bit, but after making the other speaker changes the bass was actually a but louder than when I started!

What I'm REALLY excited about is that the sweet spot seems wider now and my head doesn't have to be in a vice to get a great sound stage. It used to require that I keep my head in a 2' box. I feel like I'm at well over 3' now.

The cool part was that I could empirically tell exactly what changed and where and eventually started understanding what changes did what with regard to speaker placement.

Obviously this isn't perfect, but for a den with ZERO room treatments I'll take it!

Mark, that is indeed excellent results for an untreated room. I see that it basically fits in a 10dB window, which quite good for in-room.

I do not the dipole comb filtering in the mid-bass, telling me that a bit of absorption on the front wall focused on the 200 - 1Khz range would be helpful and give a 'fuller' mid-bass.

Have you looked at the impulse responses in REW? They are great way to see the reflections from the front wall.

Since you run JRiver, have you considered running Dirac room correction software there? It seems to do wonders, way better than manual EQ. They have a free trial so you could check it out yourself.

Well-written guidelines for ideal stereo metrics:

Mellor/Hedbeck White Paper

I haven't looked at the impulse responses yet.
I have nothing at all on the front wall. I can hang whatever I want on that wall "As long as it is tasteful"

Lots to learn. Thanks for the link, RUR.

This is the space I'm working with. It has lots of interesting holes and irregularities. Walking around the space I haven't heard any standing waves that jump out at me.

I am in pretty close to the speakers with a lot of room behind me.
There is also a 65" TV between the speakers and I suspect that a chunk of the reflected wave dissipates behind it.

It is funny but I think the sweet spot is nearly what the theoretical outer triangle walls would suggest.

I think I'm going to order some
http://www.amazon.com/Owens-Corning-703-Fiberglass-Boards/dp/B005V3L834/ref=pd_bxgy_267_text_y

I think this would give me what I'm looking for or at least be useful for experimentation.

I plan to glue a 1/4" ply board frame to the back of the fiber board and use the board to hang the foam.

I'll also staple fabric around the fiberboard to the 1/4" plywood backing.

And of course I'll have my wife pick out the fabric This will give her a chance to add some color to the blank wall behind the speakers.

I may also make a free standing 4x4' accoustic wall that I can put in front of the fireplace. I already know my cats will see this as a scratching post, so I'm considering wrapping sissel rope around the ends of it.

It should be fun to play with

RCHeliGuy said:

I think I'm going to order some
http://www.amazon.com/Owens-Corning-703-Fiberglass-Boards/dp/B005V3L834/ref=pd_bxgy_267_text_y

I think this would give me what I'm looking for or at least be useful for experimentation.

I plan to glue a 1/4" ply board frame to the back of the fiber board and use the board to hang the foam.

Click to expand...

2" OC 703 is a fairly thin choice, which will limit its usefulness to frequencies above ~1kHz. If that's your goal, carry on! Since it's a particle velocity absorber, it's best used with an open back and space behind the absorber. See here:



With the ply board backing, you'll see something like what's represented by the blue curve. If you can leave the back open and provide as little as 2" space behind the panel, you'll get much lower absorption, as represented by the red curve. If you can manage 4" thick with a 4" gap behind, you get this:



i.e. significant absorption much lower into the frequency band.

Good luck!

PS: Use a mask and gloves when handling the un-covered fiberglass!!!

I have a mask and gloves.

I could use 2 panels and make them 4" thick total or buy them in 4" thick sheets.

Are you suggesting that these may work best as free standing panels? I have no problem putting them in a freestanding frame.

If so that would allow me to experiment with positioning them and I could angle them and move them between the speaker and the wall and just test to see what works best.

I was looking at the Guilford of Maine acoustic panel fabrics.
I think my wife can find something she likes there.

http://guilfordofmaine.com/swatches/2299-7011

RCHeliGuy said:

I have a mask and gloves.

I could use 2 panels and make them 4" thick total or buy them in 4" thick sheets.

Are you suggesting that these may work best as free standing panels? I have no problem putting them in a freestanding frame.

If so that would allow me to experiment with positioning them and I could angle them and move them between the speaker and the wall and just test to see what works best.

I was looking at the Guilford of Maine acoustic panel fabrics.
I think my wife can find something she likes there.

http://guilfordofmaine.com/swatches/2299-7011

Click to expand...

Yup, two 2" thickness laid one atop the other is acoustically no different than a single 4" thickness.

Last time I made frames, I made a 4" wide surrounding box from 1/2" ply, inserted fiberglass, covered it with fabric then attached two cross pieces to the back from which to hang them. Lots of advice here: http://www.bobgolds.com/AbsorptionCoefficients.htm (scroll to bottom), though some of the links no longer work. I can provide other links, if you need them.

Guilfords is where I purchased, and they do have a terrific selection of acoustically transparent stuff.

I finally ordered some Owens Corning 703 4" thick foam and put 1 x 2'x4' piece behind each speaker centered on where the speakers toed in, or a bit outboard of where the speakers are situated.

I didn't want to bother my wife with ordering the pretty fabrics unless I was sure I liked the effect it had on the sound.

I did some A/B testing and the difference they make is very noticeable. Everything sounds clearer. The image seems wider.

I haven't put up the Room EQ software to measure the effect yet, but I'm very curious to see what comes out of it. I may tweak their placement based on the graphs I see, but I like this as a starting place

The image I showed above had some smoothing. I need to compare unsmoothed results. I suspect the reason I hear less background noise is because some of the high frequencies had comb filtering where they ebbed between very high and very low.

I hooked up the calibration mic and USB preamplifier and the results were perplexing. It did shift the combs but overall didn't clean things up as much as I might have liked. However I got an overall reading 2dB higher with with the sound deadening in place behind each speaker so it definitely cleaned up some cancellation of some kind.

After a lot of trial and error, I don't think I'm getting any consistent improvement in sound quality. So at this point I'm not going to bother my wife with picking out fabric for this 703 foam, and I'll write it off as an experiment.

Doh!!!!

As I was putting the 703 sheets back in the box, I realized that I had the hard side facing out!!!!!

One more time!