[Blueshound]

Hey James!

I want to edit a goof in my previous post - when I mentioned the OP, I was really referring to JT Sully.

I couldn't find a way to edit my earlier post.

Brian

[TJ-Sully]

HI

Ok just remember when you say absorbtion you are not dealing with low frequency information.  You are absorbing through the mids and upper octaves.  This helps with slap echo and reverb  time etc. (which is helpful) but will not do anything at the lower frequencies due to wave lengths involved.

james

Thanks James. This is very helpful, and the mathematics you presented clearly identify the unique challenges of low frequency absorption.  Massive foam!

[TJ-Sully]

Hi;

I'm an industry guy who's had the privilege of serving as the lead designer & project co-ordinator for quite a few private theaters / listening rooms.  I like music, so almost every room I've ever been involved with on works for 2-channel listening as well as with movies (you might be shocked to know how many "professionally done" home theaters can't produce a decent 2-channel stereo image). While we all have our biases based on personal preference and different experiences, I absolutely agree with James that over-damping can be a negative.  As he's said, this is largely because real-world damping is typically very efficient at high frequencies, with effective absorption declining as frequency falls. So it's easy to wind up killing high frequencies disproportionately with mids. Subjectively, and in my opinion, peaks in the upper mids do more to make a system sound artificially bright and harsh-sounding than some moderate lift in the extended highs. (This is why almost every element in the signal chain for electric guitars is almost always designed to "peak" the upper mids - so that the guitar sound can "cut through" the other midrange voices & instruments on stage or in a mix.)

When we design theaters, even with all wall surfaces covered with fabric for a harmonious appearance, there are different materials behind the fabric, according to location. These would typically include absorption, reflection, diffusion or diffraction. Absorption and reflection are the most important ones.

Most of us, who love music and the gear that makes it sound good, start with existing rooms that need some modification to be better for listening. We don't usually have the option of a large undeveloped space that can be designed from scratch, with sufficient size and volume to permit extra-depth walls or room-within-room construction to improve wide-band frequency response within the shell. So what works best is to nullify the worst of the problems, and in the process, not to create new ones (over-damping of highs can result in both dull AND boomy - not good).

Some damping of high frequencies and down through the upper mids almost always improves how you perceive imaging. Generally speaking, if you want to tighten up and make that aural perception of an instrument or vocalist at a specific point in space more believable, you have to reduce the destructive effects of the early reflections, slap echo, etc. from nearby surfaces. The closer the room boundaries, the greater the benefit of some absorption. 

To the OP, from your pics, you already benefit a little bit from the drop ceiling and ceiling panels (not much, but if you feel you want to experiment, you can buy panel replacements that are rated for sound absorption). It also looks like you're listening across the short dimension of the room?  This has the benefit of leaving lots of space from the speakers to the side walls, so that the reflections have a longer propagation time back to the listener compared to the main sound; if this time is long enough, the reflections detract less from the primary sound.

I appreciate that there are always conflicts with appearance preferences, but if you were to consider a much larger area rug, or even wall to wall carpet, that would also help.

An easy way to find the most destructive locations of early reflections is just to sit in your usual listening position and have someone move a mirror along the side walls so that you can see the mirror.  The spots where you can see the speakers in the mirror are the first locations to treat.

Is the sofa against the rear wall?  Or is there some distance between the primary listening position and the rear wall? Unless there is a substantial distance, you might also consider something on the rear wall, behind your listening seat. You have a number of options for this, from purpose-built panel(s) to a decorative rug hung as a tapestry.

I'm with James when it comes to bass traps, they're not always what they're cracked up to be.  The main problem is that they can result in an unbalanced end result - you absorb in specific physical locations in the room, corners for example, but you're absorbing so selectively that the net improvement may not be what you hoped for.

But I'm definitely in the camp of favoring some absorption, and it can be one of the cheapest and most effective improvements you can make to your listening experience. Just don't overdo it.

Hope this helps.

Brian

Brian,

Thank you a ton for your in depth analysis of absorption, reflection and characterizes of frequency response in any given room type. Super helpful man.

The wall behind me is only about 12 inches away from my ears.  I will experiment with adding some decorative materials or even some acoustic panels. The right side wall is about 6 feet from the right speaker. The left side wall must be 15  feet away. So I would suspect the mirror check would be appropriate for the right wall.

We're just moving in to this house and we definitely need more, and larger rugs. I'll continue to work on this.

Also, new to my rig is the addition of a REL 328 sub. It has brought a whole new feel to acoustic tracks, like Gillian Welch, Alison Kraus etc, and the movies now just SLAM. Which is fun.  But when I use with the My Mini T's it seems almost too much boom.  Maybe I just need to admit it and turn it down. Or perhaps adjust the frequency crossover dial on the sub. I love it all and looking forward to tuning the system over the coming weeks and  months.

Thanks again for your thoughts on this.

Regards,
TJ

[Blueshound]

No problem, TJ. Happy to help. 

Re: the sub, I don't know if this is a factor in your system and setup, but there are two separate schools of thought in integrating a subwoofer with satellite speakers that are, or almost, full range in their own response (within 3db to 40Hz I would consider full range in this conversation). One school argues for leaving the L & R speakers full range, and blending the subs in, with the sub's low pass filter affecting only the sub's output, but not the satellites.  In theory this can work, but in my experience, it often leads to a low frequency character that is muddy and overblown, and very difficult to dial in as re: the sub's output level.

The other thing that sometimes happens is a user unintentionally has two crossovers affecting the signal, one in a surround processor for example, and also the one built into the sub.  This creates a double filtering at the pass-band, and can cause the sub volume to be set too loud due to the excessive dip around the crossover frequency.

Integrating a sub is difficult at best, so be sure you try all scenarios, and listen for a smooth extension as notes step lower in frequency.

But above all else, have fun.

Edit:  I wanted to add, re: one side wall being much closer to the speakers than the other, when we design a listening room from scratch, symmetry is one important consideration.  We typically want the left side of the room to be a mirror image of the opposite side, for the best audio result.  Sometimes there are reasons why we are forced to deviate a bit, but it's a goal none the less.  In your case, adding some absorptive material on the side closest to the speakers will reduce the effect of the asymmetry.  The highs and upper mids on the side with lots of distance from the nearest speaker should be much less affected, because the delay is longer, whereas the side closer to the speaker has totally different reflection characteristics.  You can reduce this discrepancy somewhat, at least in the highs, using absorption on the side that's close. Effectively, one speaker will sound more similar to the other speaker, which is one key to imaging.

Brian