Helmholtz Resonators vs. Broad Absorption? One or the other or Both?

DaveC

[Industry Expert]
Nov 16, 2014
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#2
They are for different purposes. If you have standing waves at a certain frequency due to unfortunate room dimensions a helmholtz would specifically address that peak. Broadband absorption is useful for reducing decay times in the listening room.

Typically a room may need some absorption adjust how "live" the room is, or the rt60 reverberation decay times. This may take different forms depending on the frequencies you want to absorb. Helmholtz resonator otoh seems to be rarely needed but if the room has multiple identical dimensions it might be a good idea.
 

caesar

Active Member
May 31, 2010
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#3
Thanks. Some say broadband absorption is too much and kills aliveness of music. Others say Helmholtz approach it too narrow and doesn't take care of all the standing bass waves. Never know whom to trust. Seems like some more audio voodoo sh!t! :)
 

Leif S

[Industry Expert]
Feb 14, 2015
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California
www.vonschweikert.com
#4
The thought of putting a hollow box with an adjustable port in a room......I have not had good success with this at all. With the little time I did get to experiment with these traps, it just seem to shift the peaks to different places in the room. Pass
 

Leif S

[Industry Expert]
Feb 14, 2015
511
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0
California
www.vonschweikert.com
#5
The thought of putting a hollow box with an adjustable port in a room......I have not had good success with this at all. With the little time I did get to experiment with these traps, it just seem to shift the peaks to different places in the room. Pass
In all fairness, I have very little experience with these so I probably shouldn't have commented on this.
 
Jan 29, 2014
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Cape Town South Africa
#6
use a tube trap , it can do all 3 ,bass absorption , diffusion and midrange/hf absorption
Its a pressure device , sits in corners and along side walls , depending how you rotate them , you either get diffusion or absorption or a combo of both as 1/2 the tubes diameter is absorptive and the other 1/2 reflects and scatters .. so you can tune the room as you like and get rid of the nasty bass peaks with a single device
As you go up in tube diameter , the lower the bass you can absorb.. 20" ID with a 2" wall thickness can even work in the 20hz region. Portable tool .. you need quite a few .. google DIY tube traps for instructions
Im busy with 12x 2.4m x 500mm tube traps to replace my existing ones and all my flat traps
 

DaveC

[Industry Expert]
Nov 16, 2014
2,175
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#7
Thanks. Some say broadband absorption is too much and kills aliveness of music. Others say Helmholtz approach it too narrow and doesn't take care of all the standing bass waves. Never know whom to trust. Seems like some more audio voodoo sh!t! :)
It's just physics... ;)

Absorption can certainly be applied too heavily but it depends on the speaker and personal preference. I've heard totl Focals in a very dead room and they sounded great, other speakers wouldn't work out as well in the same room. And there's room for personal preference too so it can be hard to know who to trust, but that doesn't mean one person is wrong, they may just have different tastes.
 

JackD201

[WBF Founding Member]
Apr 21, 2010
10,986
1
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Manila, Philippines
#8
It's just physics... ;)

Absorption can certainly be applied too heavily but it depends on the speaker and personal preference. I've heard totl Focals in a very dead room and they sounded great, other speakers wouldn't work out as well in the same room. And there's room for personal preference too so it can be hard to know who to trust, but that doesn't mean one person is wrong, they may just have different tastes.
Trust Sabine :)
 

Ron Lapporte

Industry Expert
Jun 26, 2011
4
0
0
Deerfield, Illinois
#9
AXPONA 2016 with VonSchweikert and SMT Varitune Helmholtz Resonators

In all fairness, I have very little experience with these so I probably shouldn't have commented on this.
Hi Leif,
Great seeing you at AXPONA recently. Quite an impressive showing of the Ultra 11s this year. Even more impressive was the fact that you guys managed setup in one day!
If you recall, last year when we demonstrated the VR-55 Aktives in the Burton Room at AXPONA (2016) we had a very strong modal problem in the mid-60 Hz range. The decay was quite long and dominated the bass response over much of the listening area. We had four adjustable Helmholtz Resonators (SMT Varitune V-4s) in the room located in high-pressure areas which reduced the problem significantly.
I didn’t save our measurements from the show, but you can see two examples below where SMT’s Helmholtz concept were used.
The graph below shows before/after measurements taken from the listening position. The target mode was 35 Hz. Note the reduction of the null centered around 35 Hz at the listening position and the overall broadband bass improvement.

What's best jpeg.jpg

The video link below demonstrates the narrow tuning of the hatch to the target mode and the broad band result measuring with the microphone in front of the box.
https://youtu.be/GjdACNPLzzg
My experience with Helmholtz resonators is that they are extremely effective at reducing the high amplitude and decay of bass modes, without absorbing mid- and high-frequency energy, allowing those areas to be addressed independently. Just my two-cents as a fan and retailer of SMT products, including Varitune Helmholtz Resonators.
 

flyer

VIP/Donor
Dec 16, 2012
325
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Belgium
www.ultisone.com
#10
My experience with Helmholtz resonators is that they are extremely effective at reducing the high amplitude and decay of bass modes, without absorbing mid- and high-frequency energy, allowing those areas to be addressed independently. Just my two-cents as a fan and retailer of SMT products, including Varitune Helmholtz Resonators.
hello Ron, you don't mention it explicitally so I thought I would do so for the following: the use of helmholtz resonators that have no absorber inside (like SMT), work effectively narrow band attacking the problematic frequency at once (if tuned for it properly) WITHOUT losing its energy!

Quite a few brands market helmholtz resonators but normally they are stuffed with absorbant material, to increase the effective domain in which this resonator is active but as such greatly reducing their efficiency + they reinject much less the energy into the room, thus creating an overall reduction in SPL in the bass region wherein they are effective.

IF the latter were desired, then this can easily be done with the SMT varitunes as well by just putting sheets of absorber inside but it is not recommended doing so. But you have the choice, which is great.
 

Ron Lapporte

Industry Expert
Jun 26, 2011
4
0
0
Deerfield, Illinois
#11
hello Ron, you don't mention it explicitally so I thought I would do so for the following: the use of helmholtz resonators that have no absorber inside (like SMT), work effectively narrow band attacking the problematic frequency at once (if tuned for it properly) WITHOUT losing its energy!

Quite a few brands market helmholtz resonators but normally they are stuffed with absorbant material, to increase the effective domain in which this resonator is active but as such greatly reducing their efficiency + they reinject much less the energy into the room, thus creating an overall reduction in SPL in the bass region wherein they are effective.

IF the latter were desired, then this can easily be done with the SMT varitunes as well by just putting sheets of absorber inside but it is not recommended doing so. But you have the choice, which is great.
Hello Flyer,

Thank you for your comments. I'll confess that during my more compulsive moment, of which there are many, I will add a limited amount of absorptive material to a Varitune Resonator to lower the Q when a broader resonant peak is measured. I don't often find this to be necessary, but agree that is useful to have the ability to lower the Q when it's useful.

Thanks again for mentioning this issue.