Bass Trap that helps with 45Hz peak - AVS Forum
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post #1 of 22 Old 11-18-2004, 06:49 PM - Thread Starter
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Hi,

I own a SVS PC-Ultra and using placement and TrueRTA and RS SLM, I have a bad 45hz peak of about 25 hz over my dip at about 63hz. I have a BFD but was hoping to look at room treatment to reduce this peak so that I can use less EQ. I tried EQing the peak and dip and although it sounds good in my Sofa, it makes it sound terrible elsewhere in the room. As my room is a multi purpose room, I do play card games and such there and at where I place my table, the sound it very boomy.

I do not have a option of moving my sweet spot. So was wondering if getting one of the bass trap that seats under the SVS would help reduce this peak. If it does, will it also reduce the 63hz dip? I tried lifting up the PC-Ultra by avout 1 feet up and it made almost no difference.

I know of products like DAAD and RPG Bass trap. Any other usual suspects?

Thanks
Oliver
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post #2 of 22 Old 11-18-2004, 06:54 PM
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These sound like room modes, are they.
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post #3 of 22 Old 11-18-2004, 08:19 PM - Thread Starter
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Guess they are room modes. But a bass trap would still help with those right?

Oliver
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post #4 of 22 Old 11-18-2004, 08:42 PM
 
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Move your subwoofer to a different location!

--Bill
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post #5 of 22 Old 11-19-2004, 03:20 AM
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Lots of different things.

First of all, moving the sub can help some. You may find that it makes it worse at your card playing position.

Depending on what your 'card' position looks like, even room treatments might not help - hard to tell with what we know. A trap that will deal with 45Hz and not 60's is going to be large. You need some pretty serious depth to deal with those kinds of low frequencies. You can do DIY perforated traps relatively easily - they will end up being around 9-10" deep most likely and pretty good sized too.

Even if you do that, you may want to just store 2 different curves in your BFD - one for your seat and one for when you play cards.

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post #6 of 22 Old 11-20-2004, 02:31 AM - Thread Starter
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Thanks for all the suggestions.

I have tried moving it to 5 different locations, right and left corners, off left, side walls beside my sitting location and the exibit more of less the same problem. The back left corner is superb. But thats very difficult to run the cables for the sub to.

I guess I have to make do with 2 different curves on my BFD. My cards playing location is also almost flat. So I guess I can just off the BFD and reduce the output slightly and that should do it.

Oliver
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post #7 of 22 Old 11-20-2004, 05:27 AM
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Sor what about the FRONT left corner? Should be similar.

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post #8 of 22 Old 11-20-2004, 10:17 PM - Thread Starter
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Quote:
Originally posted by bpape
Sor what about the FRONT left corner? Should be similar.
Thats where my door is! I placing my front right speaker closer to the right wall. The room is not optimal but it has to do for now. :-)

Oliver
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post #9 of 22 Old 11-21-2004, 05:53 AM
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Gotcha. The only reason I asked is that in general, the front is preferred for a single sub. But, you gotta do what you gotta do. Keep the xover low and you should be fine.

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post #10 of 22 Old 11-21-2004, 07:34 AM
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What you are experiencing are room modes of a single sub.It is very normal to get good bass and bad bass responces only feet apart.Advice given to move the sub around is the best you can do at this point. This is the reason to get another sub to smooth out these modes.Another sub will not increase output that much but just give a better responce across the listening position. I'm not sure what your fear is about eqing.Make sure your bandwidth is narrow enough so you're not eqing other freq. that are not causing priblems. I have 28db peaks that had to be dealt with.No problem with the FBD.My bandwidths are between 1 and no wider than 3.This unit rules.


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post #11 of 22 Old 11-21-2004, 07:37 AM
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What you would be interested in building are Helmhltz resonators tuned to 45hz. Bass traps help with the build up of standing waves in the corners of your room.I use two.48"x18", they are homebrew and do fine.I will be building two more soon.Good luck.


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post #12 of 22 Old 11-21-2004, 02:39 PM
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Here is a pic of one of my traps.Good luck.
LL


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post #13 of 22 Old 11-28-2004, 10:55 PM - Thread Starter
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kgveteran,

Wow that liikes just like my SVS Sub! :-) Maybe I can build one and put my SVS PC-Ultra on top of it?! :-)

Do you have some instructions on what you need and how to build one? Also are there any companys you know that has a bass trap exactly for 44-45hz?

I could use EQ and get it very flat and nice just for that one or two sits in my room. But in the rest of the area, it would end up sounding so boomy, it no fun. My room is a multipurpose room so we play card games and such there as well. Yes, I could have seperate EQ for each locatoin and switch it in but it does not always work as there may be two table of card games going on at the same time. So with less EQing, I gather that the boom will be much less in most locations as well. So by just turning down about 2-3db will more or less result in good non boomy sound for everyone in the room. Makes sense?

Thanks again. I somehow missed your reply as I did not get a notification from AVS.

Oliver
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post #14 of 22 Old 11-29-2004, 04:06 AM
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Treating the room will smooth things out at more locations than EQ. You'll never get the whole room to sound flat at the same time but you can get it a lot closer than trying to EQ it.

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post #15 of 22 Old 11-29-2004, 05:41 AM - Thread Starter
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Quote:
Originally posted by bpape
Treating the room will smooth things out at more locations than EQ. You'll never get the whole room to sound flat at the same time but you can get it a lot closer than trying to EQ it.
Bpape,

Thats what I am aiming for. I have always believe that less EQ will result in better sound ultimately. Of course getting a room to sound flat with only room treatment is probably possible but costly and space consuming as well.

As it is now, my room is +-12db. I am hoping for a +-5/6 before eqing. I have seen that many peoples room that were +-5/6 before eqing. But my room could just be plain bad due to the almost equal length and width and that the height is almost half of the length and width does not make things better.

Oliver
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post #16 of 22 Old 11-29-2004, 06:01 AM
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If you do DIY, the cost does not have to be terribly high either in terms of $$$ or space. Have you tried moving the sub? Up and down is not necessarily going to be what you need to do. Play with the sub location and get it as smooth as possible by ear. Then remeasure the room and see where you stand. You may not need a great deal of treatment. Also, there are other trapping options that don't take as much floor space as tube designs if that is a concern.

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post #17 of 22 Old 11-29-2004, 06:49 AM - Thread Starter
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Quote:
Originally posted by bpape
If you do DIY, the cost does not have to be terribly high either in terms of $$$ or space. Have you tried moving the sub? Up and down is not necessarily going to be what you need to do. Play with the sub location and get it as smooth as possible by ear. Then remeasure the room and see where you stand. You may not need a great deal of treatment. Also, there are other trapping options that don't take as much floor space as tube designs if that is a concern.
Hi Bpape,

I have moved the sub around. I have tried right corner, 1 feet left and front of right corner, 2 feet front of right corner, 3 feet in front of right corner, 3 meters in front of right corner (Which is right wall beside my sitting area), 2 feet right or left corner, 3 feet right of left corner, 4 feet left of left corner. The one area that sound best by ear and measurement is 4 feet right of left coner. But it is not much better then the right corner which I decided at the end as it results in the sub looking more hidden. In fact, I tried all these locations with my PC-Ultra standing on top of my REL Q100E so that it is higher by about 35cm off the floor. Almost no difference.

All the area still results in more or less a peak at 42hz and a dip at 56hz. I cannot shift my listening position right or left but shifting it front or back by +- 1.5 feet, the best position is the front one. Any more forward and It would be too near the screen. I am hoping that a bass trap will either help with the 42hz peak or the 56hz dip.

I should be able to get some temp traps by placing some 4 inch fibreglass panels behind my right corner. Will inform you of the result if any.

Oliver
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post #18 of 22 Old 11-29-2004, 06:23 PM
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I built Jon Risches from his web site.Two cost me 175.00 ! Not bad for my first tube trap. To tune at 45hz you would have to build and tune a helmholtz resonator.I have never tryed but the info is out there,google it and see what you get.I use a Behringer 1124p parametric and it works great. 120.00shipped.


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post #19 of 22 Old 11-30-2004, 12:55 PM
 
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Quote:
Originally posted by oliverlim
Bpape,

Thats what I am aiming for. I have always believe that less EQ will result in better sound ultimately. Of course getting a room to sound flat with only room treatment is probably possible but costly and space consuming as well.

As it is now, my room is +-12db. I am hoping for a +-5/6 before eqing. I have seen that many peoples room that were +-5/6 before eqing. But my room could just be plain bad due to the almost equal length and width and that the height is almost half of the length and width does not make things better.

Oliver

Hmmmmm! While doing some measurements just last night, I was wondering what is considered a "good" room response!

I thought that a good speaker had a +- 3 DB variation over the audio spectrum.

How can anyone end up with +- 5/6 DB for the speakers and the room put together?

Must be one small sweetspot in that room, or else +- 5/6 DB is just "talk"!

--Bill
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post #20 of 22 Old 12-01-2004, 08:06 AM - Thread Starter
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Quote:
Originally posted by spider_bill_2003
Hmmmmm! While doing some measurements just last night, I was wondering what is considered a "good" room response!

I thought that a good speaker had a +- 3 DB variation over the audio spectrum.

How can anyone end up with +- 5/6 DB for the speakers and the room put together?

Must be one small sweetspot in that room, or else +- 5/6 DB is just "talk"!

--Bill
Bill,

Try measuring your speakers at your sweet spot and see. I have TrueRTA with a calibrated mic and upwards of 500hz to 10Khz, I am within +-5db at my sweetspot. But If I measure at 1 meters from the speakers, I can get +-2/3db easily. Once you factor in the room, your FR goes Haywire most of the time. It is even worst at the low frequency such as 200hz and below.

In my room, just 1.5 feet left of my sweet spot, I can get +-3db from 20hz to 100hz. But at my sweet spot, I am +-10/11db. Moving my sub does not help much and unfortuntely, I cannot move my sweet spot left or right.

Oliver
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post #21 of 22 Old 12-02-2004, 09:40 AM
 
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Quote:
Originally posted by oliverlim
Bill,

Try measuring your speakers at your sweet spot and see. I have TrueRTA with a calibrated mic and upwards of 500hz to 10Khz, I am within +-5db at my sweetspot. But If I measure at 1 meters from the speakers, I can get +-2/3db easily. Once you factor in the room, your FR goes Haywire most of the time. It is even worst at the low frequency such as 200hz and below.

In my room, just 1.5 feet left of my sweet spot, I can get +-3db from 20hz to 100hz. But at my sweet spot, I am +-10/11db. Moving my sub does not help much and unfortuntely, I cannot move my sweet spot left or right.

Oliver

I have True RTA myself, but I need to buy two microphones and mixer. At least I know how to use it now!

I made a test tone CD for bass signal testing, and use I a SPL meter for now. Also, I walk around the room and find the nulls with the meter and with my two ears. The ears will tell you a lot as far as nulls go!

For bass, I know that I do not want a flat response, so the bass on my system is in the +15 -5 DB range from my volume reference tone. More boost than null, but that is what you need in the 80HZ and under department for good bass.

I try to get a large nice sounding area about 8 X 8, so my sweet spot is a general area.

--Bill
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post #22 of 22 Old 12-03-2004, 09:07 PM - Thread Starter
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Thanks for your feedback Bill.

I think I am going to leave this alone for now. Will work on fitting in some rom treatment first and decide what else can be done to get a good large sweet spot without overwheming the rest of the room. In the mean time, I just have to make use of the seperate BFD memory settings available.....

Oliver
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