Small rooms under 150Hz, is there any solution.

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Mini swarm-style distributed system with DSP?

Could you tell what Mini swarm is please ?

Whatever loudspeakers that i've used (except a recent multiple dipolar desing), the room resonaces are the same, there are room cancellations and boosts.
The sound change from night to day at each position of the room.
My current setup has get rid of this problem but i'm tring to know if i've missing a good trick from the loudspeakers Yodas of diyaudio :D

Thx
 
Also, some people have used nearfield bass with a delayed signal. I believe with nearfield the direct signal swamps out the modes and you don't get the peaks and dips in the listening position but it's been a while since I looked at the theory. Happy listening!
 
Hi,
A number of people have reported success with the result. Harman and Gedlee have written papers on the techniques but I believe one must be able to eq to get an optimal result.

https://www.harman.com/sites/default/files/white-paper/12/11/2015 - 06:12/files/multsubs.pdf

Can't find the gedlee paper link right now but good luck!

4 subwoofers are enough !
Fantastic ! but these subwoofers needs a lot of headroom to be correctly equalized (more than two dozens of dB)

Also, some people have used nearfield bass with a delayed signal. I believe with nearfield the direct signal swamps out the modes and you don't get the peaks and dips in the listening position but it's been a while since I looked at the theory. Happy listening!

Too complex for me, i've tried to place four subs on a lot of positions... with simple equalizers.
The bruteforce dipolar infrasub near the center of the room give the best results witout extreme equalizations possibilities.

Thx.
 
Last edited:
with extensive bass trapping on the right frequencies you can do a lot to minimize room modes. But that requires some skills in acoustics and redesigning your room arround the acoustics (like they do in music studio's) so your room is death sounding.

Otherwise you will always have those kind of problems...
 
James Romeyn has a simpler variation of the Harmon system - 3 or 4 bass drivers but really well distributed in the room first to get even bass - then add some dsp if required and refrain from the large boosts to limit power requirements to quite reasonable levels

There's a number of speakers developed to specifically fit small rooms like bedrooms, etc - a lot of the small sphere type speakers function quite well here like Gallo, etc
 
with extensive bass trapping on the right frequencies you can do a lot to minimize room modes. But that requires some skills in acoustics and redesigning your room arround the acoustics (like they do in music studio's) so your room is death sounding.

Otherwise you will always have those kind of problems...

I can't modify or add anything in the room... this is for me the only interesting part of the problem.
I must do something... but i can't, i'm still trying.

James Romeyn has a simpler variation of the Harmon system - 3 or 4 bass drivers but really well distributed in the room first to get even bass - then add some dsp if required and refrain from the large boosts to limit power requirements to quite reasonable levels

There's a number of speakers developed to specifically fit small rooms like bedrooms, etc - a lot of the small sphere type speakers function quite well here like Gallo, etc

Hi,

Note that the harmon paper is not about getting the best overall response.
It is about getting the most consistent response that can then be corrected.
The two are not remotely the same thing, in terms of subwoofer placement.

rgds, sreten.

All my tests gives me the same resonances regardless of the subwoofers number or placements, perhaps i'm wrong or not enough skilled.
 
Member
Joined 2008
Paid Member
I got real-world significant different responses from testing a single sub in a dozen locations at one end of the room. Clearly aggravating or alleviating eigentones.

While testing four speaker in lots of locations would be wonderful, you are likely to reap benefits from any distribution fine-tuned or not.

I know it pains the wannabee engineers when I say this, but aim for heterogeneity of types of speakers, locations, etc. Low bass is pretty much a mono signal.

Ben
 
Last edited:
One problem that seems nearly universal is that so many people scrimp on the $s when it comes to bass - cheap bass drivers/boxes with cheap nasty bass amplifiers - hard to get a good sound with poor quality sources but very common, unfortunately.

Yeah Ben, low bass is pretty well mono - pity the rooms don't do the same!

I did a small room once with 4 x 10" subs (2 @ 80, 2 @100Hz!) and one box ended up high on a side wall, another was reverse phase near a back corner pointed up on a 2 ft high stand (yeah, well - thinking outside that box here!), and the main one ended up dead smack under the centre of the piano on the floor (behind the pedals)! - crazy setup - everything 'wrong' according to 'the book' as they say - even Jim Smith would look a bit sideways at that one! (and, naturally, the wife absolutely hated the boxes all over the place but loved the sound of that Andre Rieu music in the room. Go figure!

It helps if the amps have separate volume, variable phase adjustment, etc - good bass is 'magic'!
 
try higher q sealed designs or if going ported for output try smaller boxes tuned lower than "optimal"
while one can fuss and fret over room modes etc, it can be a relatively simple thing to get decent bass in a bedroom sized space even with small drivers, depending on spl requirements of course. many simulation programs have a room gain or equalization adjustment in them, knowing where your room starts its gain should be an important part of any design.
 
I'd recommend 2 separate woofers, away from corners if possible, away from each other to the degree that is practical, and then I'd build an active low bass EQ circuit, and/or some good Baxandall tone controls; one for low bass and one for lower midrange. You'll probably want to turn up the low bass and turn down the lower midrange to cut boominess.
 
I got real-world significant different responses from testing a single sub in a dozen locations at one end of the room. Clearly aggravating or alleviating eigentones.

While testing four speaker in lots of locations would be wonderful, you are likely to reap benefits from any distribution fine-tuned or not.

I know it pains the wannabee engineers when I say this, but aim for heterogeneity of types of speakers, locations, etc. Low bass is pretty much a mono signal.

Ben

Absolutely, and it can be interesting in a stéréo setup for the two main speakers to reach the low frequencies.
We need feel the bass pressure coming from the left if the artist/recording engeneer want it for an artistic purpose.

One problem that seems nearly universal is that so many people scrimp on the $s when it comes to bass - cheap bass drivers/boxes with cheap nasty bass amplifiers - hard to get a good sound with poor quality sources but very common, unfortunately.

Yeah Ben, low bass is pretty well mono - pity the rooms don't do the same!

I did a small room once with 4 x 10" subs (2 @ 80, 2 @100Hz!) and one box ended up high on a side wall, another was reverse phase near a back corner pointed up on a 2 ft high stand (yeah, well - thinking outside that box here!), and the main one ended up dead smack under the centre of the piano on the floor (behind the pedals)! - crazy setup - everything 'wrong' according to 'the book' as they say - even Jim Smith would look a bit sideways at that one! (and, naturally, the wife absolutely hated the boxes all over the place but loved the sound of that Andre Rieu music in the room. Go figure!

It helps if the amps have separate volume, variable phase adjustment, etc - good bass is 'magic'!

I've tried to find a tri-dimentional acoustic modelisation that can exhibit the room comportement VS frequencies...
The ennemi seem pretty invisible and these modelisations are highly controversial, it seem to be as complex as the atmospheric modelisations of the weather predictors.

try higher q sealed designs or if going ported for output try smaller boxes tuned lower than "optimal"
while one can fuss and fret over room modes etc, it can be a relatively simple thing to get decent bass in a bedroom sized space even with small drivers, depending on spl requirements of course. many simulation programs have a room gain or equalization adjustment in them, knowing where your room starts its gain should be an important part of any design.

Monopolar radiation woofers don't perform as well as dipolar ones in my room.

I'd recommend 2 separate woofers, away from corners if possible, away from each other to the degree that is practical, and then I'd build an active low bass EQ circuit, and/or some good Baxandall tone controls; one for low bass and one for lower midrange. You'll probably want to turn up the low bass and turn down the lower midrange to cut boominess.

I've chosen high QTS transducers from Visaton (because their engineers have designed them for that purpose and they are as cheap as necessary).
Wide band response equalizations are useless with such narrow band speakers configurations as infrasonic subwoofers.

Just as a simple experiment put a small slow speed fan in front of the woofer so that the sound is chopped a bit by the fan blades.

Eminent Technology’s Bruce Thigpen... too low for me !
 
Member
Joined 2008
Paid Member
We need feel the bass pressure coming from the left if the artist/recording engeneer want it for an artistic purpose.
The almost-meaningful part of your sentence might be re-written, "... we sense the bass instrument coming from....." to make it somewhat meaningful.

If you know anything about concerts, the double-basses can be found all over different parts of the stage in different halls and orchestras. So your anxiety really is about the aesthetic wisdom of the recording producers, so as they might have any and not about what Mahler had in mind in Vienna.

On music, there is no sense of location for notes below maybe 150 Hz, even if trick-lab research can show lower discrimination. The upper partials grab your attention unalterably and your mind's eye goes where Blumlein's stereo math says it should.

I am assuming your speakers do not have terrible distortion (which are high enough in frequency to be locatable) or too lazy a cross-over slope (ditto).

Ben
 
Last edited:
Hi bentoronto,

The almost-meaningful part of your sentence might be re-written, "... we sense the bass instrument coming from....." to make it somewhat meaningful.Ben

On some of my recordings the bass is sometimes only at one side or sometimes panned between the right of left side, it is fun mastering effect.

If you know anything about concerts, the double-basses can be found all over different parts of the stage in different halls and orchestras. So your anxiety really is about the aesthetic wisdom of the recording producers, so as they might have any and not about what Mahler had in mind in Vienna.Ben

I don't know anything about concerts, i usually listen studio recordings, i'm trying to stay in the stereo paradigm.

On music, there is no sense of location for notes below maybe 150 Hz, even if trick-lab research can show lower discrimination. The upper partials grab your attention unalterably and your mind's eye goes where Blumlein's stereo math says it should.Ben

Have you tried to ear a 150Hz waveform and spanned it between the two speakers in a near field situation ?
Everyone is able to localise my sub if i put it on the right side or le left side of the listening position (very close)
When you are very close to the speakers you can feel the sound pressure on your skin (with your corpuscles) and localise the low notes even at moderate levels.
We cant see the infrared light... but we can feel the thermal radiance on our skin.

I am assuming your speakers do not have terrible distortion (which are high enough in frequency to be locatable) or too lazy a cross-over slope (ditto).
Ben

I will try perform distortion measurements for fun, but i don't expect good results. all my active filters uses 24dB/oct slopes.
 
Last edited:
Member
Joined 2008
Paid Member
On some of my recordings the bass is sometimes only at one side or sometimes panned between the right of left side, it is fun mastering effect.

I have the impression you don't understand the difference between where the frequencies are and where the virtual instruments are.

It makes no difference in localization where in your room you are outputting tones of say 80 Hz (a number chosen low enough to avoid dispute, for the moment).

There are obvious reasons why a recording engineer would put all the bass they can into all the channels they have. And they can.

Ben
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.