Room Too Dead

@dekay

+1

Thin plastic can reflect highs while still letting bass go through and get absorbed by underlying layers. You’ll need to get it distributed on opposite walls so the sound can bounce around again. By selectively livening up parts of the room you may be able to achieve a desirable effect where immediate early reflections are absorbed but later reflections can stay alive for a while and reach your ears to create some spacious ambience. If you can prevent early reflections from reaching your ears for the first 10 to 15 milliseconds and then have some ambience sustain after that in the room, that should sound really good. That corresponds to a path length of about 14 to 20 feet, so the sound from the first reflection should travel an additional 14 feet to your ear after the direct sound from the speaker arrives. Delayed reflections that cross your head at angles of 60 degrees or more are desirable to create maximum inter-aural difference. Reflections from straight ahead and behind  are less useful and should be deflected to the sides of the room.

@soix

That’s just mid bass and not what I’d consider “lows.”

Mid bass is usually what needs to be gotten after. What you call "lows" are very difficult to absorb.

I agree with your earlier statement that curtains and such are not going to absorb much bass or even midbass behind the plastic.

@erik_squires

Interesting what you said about too many TubeTraps causing mid-range suckout. This is not a situation that I’ve heard brought up before. Are we talking about midrange as below 600Hz? I’ve been told that a good goal for a home listening room is to shoot for an RT60 of about 0.3 seconds in the lower midrange and mid-bass, rising somewhat higher in the bass and upper treble. That sounds like a small amount of midrange suckout. From what I’ve seen of people’s rooms, it’s easy enough to get a rising RT60 in the bass, but getting it to also rise in the upper treble, that’s not something I’ve actually seen yet in a room measurement. My room is currently fairly flat around 0.3 seconds from about 400hz on up, which I consider to be a fairly fortunate result. Most of the time I see the RT60 falling in the treble, with the clarity conversely going up. It’s super easy to absorb the high frequencies. They also don’t tend to get dispersed from the speaker as well.

I’ve found a room can sound dead with one set of speakers and not another. The dead-ness I think is caused as much by the average frequency response of the reflections as anything, so a speaker that’s beamy in the midrange and widens quickly in the midbass can make a room sound murky. One that stays wider up to a higher frequency in the midrange can make the whole room sound more lively. I just bought several different waveguides to experiment with. EQing them all flat on axis, the overall effect in the room is strikingly different between them. A beamy tweeter needs to be matched to a well controlled, similarly beamy midbass, which is hard to do. Or you need to absorb a lot of midbass out of the room, and not the highs.

@erik_squires

Well that’s exactly the opposite of what we would hope to achieve with liberal use of TubeTraps, and not a complaint I’ve heard before concerning TubeTraps. One note bass has been used a lot to describe bass where a particular room mode is dominating. Why a lot of TubeTraps would cause it rather than lessen it is something that requires some deep thought. Was that the 2019 California Audio Show? I was at that show and got to hear several rooms before and after we treated them with TubeTraps. Honestly, I was struggling to notice much of a significant difference. I was new at the time, unfamiliar with the listening spaces, and unfamiliar with the audio equipment, and tired. Most of the rooms we treated were large and I don’t think we were able to put enough treatment in them to get something highly noticeable to happen. The people that were running the rooms felt there was significant improvement, and chose the amount they wanted based somewhat on our own recommendations but also on their ears. Often they wanted even more but we only had so many to offer.

In my own experience, one note bass is mostly a speaker placement issue, but can also be addressed successfully with equalizing down peaks. I know some people are dead set against any kind of equalization, so if that’s out of the question, I think a distributed array of subs to break up the major modes is the only workable solution. Or, a very powerful and extensive array of bass absorbers.

@mannytheseacow

Easily achieve the same effect DIY? I guess that depends on your definition of easy. Dennis recommends very extensive treatments of absorbers that use activated carbon. To do what he suggests is going to take a lot of effort and money. Less money but more effort if you DIY.

I got to hear a room he set up last year at the Pacific Audio Show. It sounded good, but there was not much bass because he said he didn’t bring enough subwoofer for the size of the room. He brought a semi-truck load worth of acoustics just to treat a portion of that one room. He basically built a room within a room, building four walls out of bass traps and diffusers. He also intentionally used a mid level Klipsch system with some basic electronics to prove the point that the acoustics could make even a lower end system sound great.  

On a similar note, at the 2019 California Audio Show we acoustically treated a conference room that had a basic Behringer PA system with an array of TubeTraps all around the room and flanking each speaker. The point of that room was to allow manufacturers to give presentations about their products. Between talks the system would play music. I had several people tell me that room was possibly the best sound at the show! I don't know if I would go that far myself, but it was very nice listening to movements from Swan Lake there.