MAJOR bass cancellation probs.(bass traps?) HELP PLEASE

Mike<>P · 05-10-2004, 12:22 PM

Hey folks, I'm just about done with the construction my new theater/listening room and I think I've created a monster.

Like a typical guy I set up the electronics first. What I have now is a large room with virtually zero bass at the listening position. Of course at the corners and along walls there is a decent quantity of bass but it is quite muddy. When I leave the room and go(through the door)into the kitchen there is the loudest bass I have ever heard, in a house at least.

The bass at the listening position sounds so bad it almost messes with your equilibrium. Sort of an out of phase sound(yes all the drivers are in phase) The only bass to be heard there is sort of a resonant bass, in other words it has ZERO impact(though if it did it still would sound like crap)

So, from what I have gathered over the phone with various people and also on the internet, I have reflection/cancellation issues. Bass traps seem to be the only solution to my problem.

I guess my questions are;

2) Has anyone heard the effectiveness of bass traps.
3) If bass traps are the solution, is it a sure bet. In other words will the proper amount of traps TOTALLY cure the problem.

If anyone has any questions please ask. I will be making posts, including pix, reguarding other specifics including components, speakers, general photos, etc..... Thanks

Rutgar · 05-10-2004, 01:17 PM

In my opinion, you'll be wasting your money and time buying bass traps. You didn't say anything about your gear. Do you have a subwoofer? If so, there is a current thread in the "Speakers/Subwoofer" section of this forum that is very helpful in setting it up. If you don't have a Subwoofer, and money isn't a big problem, the new Velodyne "Digital Drive" subs will allow you to "tune" the low end of your system for a smooth Bass response. A cheap alternative to this particular Sub is the Behringer "BFD Feedback Destroyer". It is a Parametric equalizer that costs about $120.00 at most professional music gear stores (such as Guitar Center). To set it up, you need to also get a Radio Shack sound level meter. Here is a link that tells you how to set it up, step by step. Hope this info helps.

http://www.snapbug.ws/bfd.htm

- Rutgar

Mike<>P · 05-10-2004, 01:33 PM

I have 2 subs w/3 15" drivers total. One Klipsch KSW15 and a DIY dual 15" Titanic ported box.I am in the process of building a web page @yahoo so I'll be able to post pix of my rack and speakers. I figured I could just attach an image like an e-mail to post pix.....sorry. It'll be done in a little while.

Rutgar · 05-10-2004, 02:22 PM

I also run two subs (two Velodyne ULD-15's). Right now, I have them in opposite corners of the room, and have almost perfect response (without the BFD). It took me a lot of experimenting to finally get them right. Also I corrected the link in my first post. It should work now.

- Rutgar

Mike<>P · 05-10-2004, 03:42 PM

I have tried every position(except opposite corners)with the subs with the same outcome. Even w/o the subs on,my mains have very very little bass in the listening position. They are Klipsch Cornwall II's which are VERY good at producing bass. In my last room which was only 13x15 they,for the average joe,were more than adequate w/o using a sub. The room before that was 24x24 with a 25' cathedral ceiling and they also sounded excellent. Which leads me to believe it's my room acoustics.

I even played one of those dedicated rap bass cd's(read MEGABASS)with and w/o the subs and still the room exibited the same response but I go out into the kitchen and there the bass is! In other words I'm standing outside the cancellation zone(or what is now appearing to be the twilight zone!)

Anyway,I'm still working on getting some pix up( i guess I need to have 15 posts in order to do so) so please be patient. In the meantime I'll try the opposite corner placement. Thanks,Rutgar

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Wayne A. Pflughaupt · 05-10-2004, 05:50 PM

Hi Mike,

Quote:

So, from what I have gathered over the phone with various people and also on the internet, I have reflection/cancellation issues. Bass traps seem to be the only solution to my problem.

Bass traps do nothing for cancellation issues. They are designed to reduce peaking frequencies – the opposite of what you’re experiencing.

A couple of things you wrote give some clues to what is happening:

Quote:

I have 2 subs w/3 15" drivers total. I have tried every position(except opposite corners)with the subs with the same outcome.

Separating the subs usually aggravates cancellation problems, because the half-way point between them will function like a room boundary. As if you don’t have enough of those already – don’t make it worse.

Quote:

What I have now is a large room with virtually zero bass at the listening position. Of course at the corners and along walls there is a decent quantity of bass but it is quite muddy.

This tells me that you probably have your seating position in the center of the room (i.e., away from any boundaries). The problem you’re having will be typical in a large room like yours. It’s very common for bass to be stronger along boundaries and weaker in the center. I don’t know what you can do about it, except get more potent subs, move the seating closer to a boundary, or reduce the size of the room.

Regards,
Wayne

Ronald Epstein · 05-10-2004, 06:06 PM

Folks,

Mike (the author of this thread) sent me these
pictures to upload for all of you to see....

Mike<>P · 05-10-2004, 06:58 PM

Gee,thanks Wayne!

thats real encouraging news! From what I understand the cancellation is caused by reflecting waves off the surfaces in the room interacting with each other thus destroying themselves. In other words the waves have nowhere to go. Bass traps, from what I understand, absorb low frequency energy and in turn give it a place to go. Therefore the bass would be louder and more defined due to the theoretical lack of bass energy bouncing back. Kind of like listening to a killer car stereo with the windows up. Roll the windows down and the bass gets much louder. The waves are allowed to escape thus minimal cancellation occurs.

Indeed I do have a large room 21x31 but like I said earlier my now bass problematic mains sounded great in the 24x24 room. The major differences between the rooms are the old room had a smaller 20x10 room off of it(w/o dividing walls),two doorways(one to the kitchen,one to a bedroom)and a hallway. Also it is a log home with well...log walls-not particularly airtight and very good for diffusing sound waves.

Yes the listening point is 2-3' beyond the center point of my current room not unlike the log cabin room.(maybe I should kick my parents out and move back home!)

It would seem like I am really sold on the bass trap idea but I believe all signs point to this type of phenomenon, maybe I'm wrong but it sure makes sense.Any elaboration or other input is appreciated. Thanks again,Wayne

Rutgar · 05-11-2004, 07:09 AM

Mike, before you spend lots of money on Bass Traps, I would click on the link that I supplied in my first post, go to the section that supplies the links for test tones and the Microsoft Excel spreadsheet, download the spreadsheet, and test tones, burn the test tones to an audio CD. Then buy the Radio Shack sound level meter, take measurements at your listening area, use the spread sheet to plot what you're listening to. That way, you'll have a clear idea of what you're dealing with in your room. I would suggest taking measurments with both subs, as well as each individually, and at different posistions. In other words experiment. Bass Traps are expensive if you buy them, and they're a pain build, if you make them. Plus, they're very hard to tune the room with. Moreover, as Wayne said, they really do nothing for "suckouts". The meter, spreadsheet, and test tones are cheap and easy way to get a really good look at what's going on your room. Trust me, I've gone through what you're going through. I have two very large Bass Traps now sitting in my garage, because they're useless. I put them in the same catagorie as "Bi-Wiring" and painting one side of your CD's green.

Keep us informed on your progress.

- Rutgar