# Bass Traps vs EQ



## Phillips (Aug 12, 2011)

Hi i have a room mode at 37hz.

I was looking at either a Helmholz Resonators or EQ or other bass traps.

Anyone had experience or info with the Helmholz resonator i can't see anything on them?

Thanks ahead


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## robbo266317 (Sep 22, 2008)

Helmholz Resonators are tricky to get right, I would suggest standard bass traps and EQ.
Have you tried moving speakers and listening position to try and reduce it?


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## Phillips (Aug 12, 2011)

robbo266317 said:


> Helmholz Resonators are tricky to get right, I would suggest standard bass traps and EQ.
> Have you tried moving speakers and listening position to try and reduce it?



Thanks

I haven't got much room, but yes i have tried especially the listening position. I could bring them closer together?

The room is a normal lounge. 

Is there any discrete / small bass traps that improve bass that low?

I have considered changing speakers to a mini monitor (Proac Tablet Aniversary). I have floor standers Energy Veritas 2.3i currently running with 2 x REL Strata 5. 

Anything else i could try?

Thanks again


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## hjones4841 (Jan 21, 2009)

A 37Hz wavelength is very long, which makes bass trapping rather difficult. Multiple large traps may help. I have a 27Hz mode in my room. I put in a LOT of trapping. It helped upper bass a lot, but only a little at 27.


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## robbo266317 (Sep 22, 2008)

What are the dimensions of your room?

A plot of the layout would be helpful as well. :bigsmile:


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## Todd Anderson (Jul 24, 2009)

I'd agree with the notion that hitting down that low will be hard. Have you thought about adding a second sub?


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## Kal Rubinson (Aug 3, 2006)

Phillips said:


> Is there any discrete / small bass traps that improve bass that low?





hjones4841 said:


> A 37Hz wavelength is very long, which makes bass trapping rather difficult. Multiple large traps may help. I have a 27Hz mode in my room. I put in a LOT of trapping. It helped upper bass a lot, but only a little at 27.


The only small devices that will work are active. Either electronic EQ or an active trap like the BagEnd eTrap (http://www.stereophile.com/content/music-round-31-page-2) which can be tuned to your needs.


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## dspandrc (May 4, 2012)

EQ is not a complete solution to bass mode issues. You can get the amplitude of the resonant peaks to match the rest of the response (which is a lot better than doing nothing) but it does not have any impact upon the reverberation time of the resonant mode. You get the best results from absorption tuned to the resonant frequency of the mode(s).

When I designed my listening room (in an unfinished basement) I designed-in a lot of Helmholtz slot absorbers and quarter-wave bass traps. The Helmholtz slot absorbers took a lot of space and are not the sort of thing that one can add to a finished room. 

However, you may be able to add quarter-wave bass traps. There are two possible approaches you could use. The quarter-wave length of a 37 Hz signal is between 7 and 8 feet. If you have a full-height room (8 feet or higher) you could close-off corners of the room (making a triangular cavities) sealed everywhere except for an opening at the top. Stuff the cavity with loose fibreglass. The other alternative is to use the ceiling cavity to create quarter-wave traps. I have used the space between the ceiling joists to get some additional tuned absorption. You would have to cut an opening in the ceiling and then close-off between the joists to give a cavity of the appropriate length.

Active cancellation is, of course, the other option.

Just to show what can be accomplished with purely passive tuned absorption I am attaching a waterfall plot of my subwoofer response at my listening position. The axial mode fundamental is about 24 Hz, the second axial mode harmonic at about 48 Hz and there is a diagonal mode at about 37 Hz.

Tony


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## dspandrc (May 4, 2012)

Missed the attachment. I used REW waterfall default parameters.


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## Phillips (Aug 12, 2011)

robbo266317 said:


> What are the dimensions of your room?
> 
> A plot of the layout would be helpful as well. :bigsmile:


Thank you

The room is 5.8 meters (L) x 3.7meters (W) x 2.8 meters (H).

The right speaker fires over a couch (port especially)

The left is unblocked.


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## Phillips (Aug 12, 2011)

27dnast said:


> I'd agree with the notion that hitting down that low will be hard. Have you thought about adding a second sub?


Thank you

I have already two REL Strata 5 that are setup High Level.


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## Phillips (Aug 12, 2011)

Kal Rubinson said:


> The only small devices that will work are active. Either electronic EQ or an active trap like the BagEnd eTrap (http://www.stereophile.com/content/music-round-31-page-2) which can be tuned to your needs.


Thank you

I can get my hands on a Velodyne DD12 sub, would this be any advantage, work simliar to the BagEnd? The Velodyne has speaker level connectors. The sub is sitting around doing nothing, i think.

I like running the speakers full range and running the RELS high level.


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## Phillips (Aug 12, 2011)

The distance that is suggested for speaker distances
1. Is this from the middle of the driver to the side wall
2. From the front of the speaker to the wall behind the speaker or from the back of the speaker cabinet to the wall behind the speaker.

With the lounge being 3.7m (W) 5.8m (L) what would be a good starting point?

I can't bring them too forward, but width is not a problem.

Thank you


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## Phillips (Aug 12, 2011)

dspandrc said:


> EQ is not a complete solution to bass mode issues. You can get the amplitude of the resonant peaks to match the rest of the response (which is a lot better than doing nothing) but it does not have any impact upon the reverberation time of the resonant mode. You get the best results from absorption tuned to the resonant frequency of the mode(s).
> 
> When I designed my listening room (in an unfinished basement) I designed-in a lot of Helmholtz slot absorbers and quarter-wave bass traps. The Helmholtz slot absorbers took a lot of space and are not the sort of thing that one can add to a finished room.
> 
> ...



Thank you

Do you run your speakers full range then underpin them with the sub?


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## Kal Rubinson (Aug 3, 2006)

Phillips said:


> Thank you
> 
> I can get my hands on a Velodyne DD12 sub, would this be any advantage, work simliar to the BagEnd? The Velodyne has speaker level connectors. The sub is sitting around doing nothing, i think.
> 
> I like running the speakers full range and running the RELS high level.


No. The Velodyne is a sub and, while the BE starts with same guts, it has additional stuff to cancel modes actively. Not at all equivalent.


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## dspandrc (May 4, 2012)

My main front speakers are QUAD ESL 2809s with a QUAD ESL 989 as the front centre speaker. Each of these three QUADs has an associated subwoofer. I use R Bessel filters at about 80-90 Hz crossovers. With these filters the QUADs roll-off at 6 dB per octave so they are essentially used full-range but with attenuation in the bass (that is why the sub waterfall was not flat). My system measures essentially flat from about 8 Hz to 17 kHz. I use QUAD ESL 989 as the rear speakers and I run those full-range.

Tony


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## UF6 (May 10, 2012)

Standard Helmholtz Resonators are a very tricky thing (extreme notch characteristic!). I would really recommend to use slot / hole pannel resonators, they have a greater bandwith and are very good at absorption. In my oppinion this type has the best performance of all bass absorber types. 

Disadvantage: Price.


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