Measured effects of bass traps?

Rich Carlson · « **on:** 29 Sep 2004, 11:21 pm »

Has anyone seen published (or posted, for that matter) measurements of the effects of using bass traps of any kind?
Thanks,
Rich

zybar · « **Reply #1 on:** 30 Sep 2004, 12:34 am »

Quote from: Rich Carlson

Has anyone seen published (or posted, for that matter) measurements of the effects of using bass traps of any kind?
Thanks,
Rich

Check www.realtraps.com

I am not associated with the company, just a very happy customer.

George

davejcb · « **Reply #2 on:** 30 Sep 2004, 04:31 am »

Just took them for you. This is no bass trap vs. two floor to ceiling corner bass traps, made of 4" 6lbs/ft3 FSK faced fiberglass. BIG difference. I have two more to make, should be good.

Compare!

Red Dragon Audio · « **Reply #3 on:** 30 Sep 2004, 04:34 am »

Hey DaveJCB,

How does it sound in the room now? I'm still waiting for my box of Insulation Boards from the place in SLC.

davejcb · « **Reply #4 on:** 30 Sep 2004, 04:36 am »

You know what, I can't really remember what it was like before. I will A/B with and without traps and listen... Seems like bass is tighter and louder than before though.

Only thing is I sold the dAck!, so now I only have the Panasonic DVD-A7 to listen with... But I do have a ~500WHP turbo!!!

Red Dragon Audio · « **Reply #5 on:** 30 Sep 2004, 05:31 am »

holy hell. 500WHP. damn.

It's final. We're getting that house (unless something else arises to stop us; knock on wood or do something lucky for us).

So when we move in, the basement is all mine to finish off. Of course we won't have any money to do so.

Maybe in a year, I can go full force on the basement listening/Office showroom after saving up some cash.

At which time I will be able to fully build traps, absorbers, etc to my heart's content. Then I too can comment on their apparent goodness.

Ethan Winer · « **Reply #6 on:** 1 Oct 2004, 12:57 pm »

Rich,

> Has anyone seen published (or posted, for that matter) measurements of the effects of using bass traps of any kind? <

Thanks to George for mentioning my company's products.

You can see the results of a before/after test in the MiniTraps demo video on our site. Here's a direct link:

www.realtraps.com/videos.htm

Note that bass traps do two very different things: One is to flatten the low frequency response, lowering peaks and raising nulls. That's what's shown in our video. The other thing bass traps do is reduce modal ringing - sort of like low frequency reverb - and that's just as important because it avoids "overhang" on bass notes that makes it difficult to hear which notes are being played. You need a program like ETF or a sophisticated hardware analyzer to measure that and see the change after installing bass traps.

--Ethan

ctviggen · « **Reply #7 on:** 5 Nov 2004, 12:04 am »

Those are cool videos. Also, it makes sense that the bottom corner and top corner of the floor are the same, but didn't click in my head until you (Ethan) said that. Also, I may put something on a door, too, so it was interesting to see how you did that.

ctviggen · « **Reply #8 on:** 5 Nov 2004, 12:41 am »

Ethan,

Is there a source that describes how non-room-modes are created? I can understand room modes, but I'm not sure that I understand non-room-modes.

Thank you.

Rich Carlson · « **Reply #9 on:** 5 Nov 2004, 11:38 am »

A very belated but sincere thank you for the responses! I somehow missed the followups until now - sometimes work gets in the way of my hobby

. Davejcb, thanks especially for the graphs. And Ethan, thanks for the direct link. I'll be thinking about what to do in my room.
Best,
Rich

Ethan Winer · « **Reply #10 on:** 5 Nov 2004, 06:35 pm »

Bob,

> Is there a source that describes how non-room-modes are created? <

By non-room mode do you mean peaks and nulls related to speaker and listener position in the room? Those are very real, but they're not modes. The term mode is reserved for resonances whose frequencies are determined by the various room dimensions.

Non-modal peaks and nulls are caused by simple acoustic interference: A wave strikes a surface and reflects back into itself. At 1/4 wavelength from the boundary a null occurs. This is explained in several of the articles on my company's site, as well as in the video Non-modal Peaks and Nulls, also on our site.

--Ethan

ctviggen · « **Reply #11 on:** 5 Nov 2004, 07:23 pm »

Thanks, Ethan. I did watch your video, but I wanted more information to satisfy my scientific mind (I'm an engineer by trade, although I happen now to use my engineering mind as a patent attorney). I've ordered some books about acoustics, and I'll look on your site, too.

Rob Babcock · « **Reply #12 on:** 5 Nov 2004, 10:02 pm »

Ethan, isn't improving the reverberent time in the low freqs another benefit of bass traps? In other words, my understanding has been that it's not just a measure of how many dBs the bass will change but a factor of how the bass notes decay. But I'm a tad fuzzy on the details.

Red Dragon Audio · « **Reply #13 on:** 6 Nov 2004, 12:20 am »

Quote from: Rob Babcock

Ethan, isn't improving the reverberent time in the low freqs another benefit of bass traps? In other words, my understanding has been that it's not just a measure of how many dBs the bass will change but a factor of how the bass notes decay. But I'm a tad fuzzy on the details.

I would think so. If bass is being distorted and boosted, then the decay/reverb is affected. So if traps absorb some of the "excess bass" then it should sound cleaner, tighter and probably more natural...which I bet is related to the decay/reverb time you speak of.

lonewolfny42 · « **Reply #14 on:** 6 Nov 2004, 08:08 am »

Quote from: Ethan Winer

Rich,

> Has anyone seen published (or posted, for that matter) measurements of the effects of using bass traps of any kind? <

Thanks to George for mentioning my company's products.

You can see the results of a before/after test in the MiniTraps demo video on our site. Here's a direct link:

www.realtraps.com/videos.htm

Note that bass traps do two very different things: One is to flatten the low frequency response, lowering peaks and raising nulls. That's what's shown in our video. ...

Thanks Ethan....interesting video's...so I bumped it up in case other's have not seen them.

Ethan Winer · « **Reply #15 on:** 6 Nov 2004, 04:11 pm »

Bob,

> I did watch your video <

I just wanted to point out that there are two videos, and the second one addresses non-modal peaks and nulls. In truth, all peaks and nulls are caused by basic acoustic interference. The difference between modal and non-modal peaks/nulls is simply that for modal frequencies the waves fit exactly between opposing room boundaries.

Besides that video, there are two articles on our site that address this. One is "Do room modes even matter?" and the other is "A new approach to small room acoustics." In the first one I point out that modes are a subset of acoustic interference.

--Ethan

Ethan Winer · « **Reply #16 on:** 6 Nov 2004, 04:17 pm »

Rob,

> isn't improving the reverberent time in the low freqs another benefit of bass traps? <

You bet. It's at least as important as improving the response. With "midrange" musical instruments reverb can sort of simulate chords and multiple notes sounding, which adds richness. But with bass instruments the same effect just makes the music muddy sounding. When one note continues to ring (in the air) after another note starts, it's difficult to distinguish either note.

--Ethan

ctviggen · « **Reply #17 on:** 8 Nov 2004, 08:01 pm »

Hi Ethan,

I did watch both videos, and I liked them. I hope to purchase software prior to doing my own treatment of my room so that I can see what benefit the treatment has. I may use my RS meter, though, because the cost of the software plus a good microphone is pretty high (particularly when I'll be using the software only a few times). I will also read your recommended articles. Thanks!

zybar · « **Reply #18 on:** 9 Nov 2004, 12:24 am »

Quote from: ctviggen

Hi Ethan,

I did watch both videos, and I liked them. I hope to purchase software prior to doing my own treatment of my room so that I can see what benefit the treatment has. I may use my RS meter, though, because the cost of the software plus a good microphone is pretty high (particularly when I'll be using the software only a few times). I will also read your recommended articles. Thanks!

Bob,

I have the software, maybe we can figure out a way to finally get me up there...

George

ctviggen · « **Reply #19 on:** 9 Nov 2004, 01:32 pm »

George,

That sounds good. For the next weekend, though, I'll be helping my friend get his house ready to be put on the market (he's moving to Minnesota -- couldn't find a job here in CT after months of trying). After that, though, the weekends should be pretty clear (except Thanksgiving day).

But I probably won't be able to afford the traps (and 8th nerve stuff) for a while. So, an initial analysis would be good (and could help me figure out a problem I may be having -- my imaging seems shifted to the right for some reason; maybe measurements with only one speaker hooked up then measurements with the other speaker only would verify this), but I also don't want to waste your time. Anyway, I'll email you once my friend finally moves.