My acoustically treated Home Theatre (updated)

[sarumbear]

It’s better than no fixing at all.

I respectfully disagree. Reducing the bass energy in a room makes the sound unlikeable. Everyone likes bass even if it’s peaky.

 

[Zaireeka]

Excellent paper. Concentrated on the speech range but it explains everything you need to know about acoustics of resonators eloquently.

I find this compact design particularly interesting, and still possible to be constructed without needed specialized machinery or a 3D printer as suggested. If only I had more time...

 

[sarumbear]

I find this compact design particularly interesting, and still possible to be constructed without needed specialized machinery or a 3D printer as suggested. If only I had more time...

View attachment 221328

Depending on your room size it is possible that energy absorbed with such small absorber (even though it’s compacted) is not enough to bring down the peaks.

 

[-Matt-]

What specifics you want to know further than what I already said on this thread?

How was the variable sized opening achieved?

Is it best to position the resonators at room corners if possible?

I've skimmed throught the paper and have seen equations to calculate the resonant frequency. How does one tune the amount of attenuation? By adding multiple resonators? Is it possible to calculate in advance how many will be needed?

 

[sarumbear]

How was the variable sized opening achieved?

I create a rectangle opening (port) and over it slide a flap to change the port area. Once the required frequency is reached I tighten the screws (that are acting like a guide to the flap) to fix the flap in place.

I see adjustable length vents on the market but I don’t use long vents on my resonators.

 

[sarumbear]

Is it best to position the resonators at room corners if possible?

Yes but large resonators will be less position dependant.

I've skimmed throught the paper and have seen equations to calculate the resonant frequency. How does one tune the amount of attenuation? By adding multiple resonators? Is it possible to calculate in advance how many will be needed?

Easiest way to find the room modes is via a manual sweep of sine-wave and watch the frequency reading.

You can then place the microphone inside resonator and tune it to those frequencies.

 

[-Matt-]

You mention having your resonators in the ceiling and false walls. Does the port need to open into the room (so that a hole is visible) or do the bass frequencies pass throught the ceiling with sufficient ease that it doesn't matter.

I have a potential space below wooden floorboards and carpet, perhaps this would attenuate too much and an open vent would be needed?

 

[sarumbear]

You mention having your resonators in the ceiling and false walls. Does the port need to open into the room (so that a hole is visible) or do the bass frequencies pass throught the ceiling with sufficient ease that it doesn't matter.

I have a potential space below wooden floorboards and carpet, perhaps this would attenuate too much and an open vent would be needed?

My false ceiling is acoustically transparent at bass frequencies. Most likely a floorboard with carpet on it will not be. As you said though if the port is open to the room then you are good to go. You should be able to have two vents, protruding from the floor, each tuned to a different frequency.

 

[abdo123]

I respectfully disagree. Reducing the bass energy in a room makes the sound unlikeable. Everyone likes bass even if it’s peaky.

Then why did you treat your room and buy a top of the line processor and a setup that makes 99% of users here emasculated if ‘Everyone likes bass even if it’s peaky’

Might as well be happy with a sound bar and a subwoofer.

 

[sarumbear]

Then why did you treat your room and buy a top of the line processor and a setup that makes 99% of users here emasculated if ‘Everyone likes bass even if it’s peaky’

Might as well be happy with a sound bar and a subwoofer.

I don’t understand your point. However, I can see that it’s not meant to be nice even though I said I respectfully disagree.

 

[-Matt-]

Yes that was disagreeable ...moving swiftly on...

Do you use any wadding to increase absorption within the resonators and lower Q?

 

[sarumbear]

Yes that was disagreeable ...moving swiftly on...

Do you use any wadding to increase absorption within the resonators and lower Q?

I don’t lower the Q because I have many separate resonators, each working on a separate frequency. In my room that was a better compromise. (It’s always a compromise.) The main problem with increasing the resistance of the port is the power of the resonator is also reduced, hence you need bigger enclosures.

Besides, as I said above I don’t use long ports and there are not many practical ways to “wad” a short port.

The paper that was linked above is a great document and has practical advise. Try to read it. It’s not full of boring math.

 

[Newman]

I suggest in investing a microphone and use the free software REW. Averaging will hide the room modes.

Assuming you have a microphone and REW too, please show the unsmoothed responses at positions 1, 2, and 3.

 

[sarumbear]

Assuming you have a microphone and REW too, please show the unsmoothed responses at positions 1, 2, and 3.

I’m afraid I can’t. I do have REW but due to familiarity with other software I am not using it.

Besides, the Q of a 1/6 octave bandwidth is almost 8.5. It is considerably higher than any room mode bandwidth that can exist in an a acoustically leaky room like mine.

 

[Newman]

It would be nice to see and pretty simple to do though…

Oh, and I meant to add, show the unsmoothed plot only from 20-300 Hz…

 

[sarumbear]

It would be nice to see and pretty simple to do though…

Oh, and I meant to add, show the unsmoothed plot only from 20-300 Hz…

It is not simple for me. There is no computer on that room. My computer is a floor stander workstation in a room at the other end of the house and I do not own a laptop.

Meanwhile, you do realise that my source is pink noise. I use that in order to "load" the room and make sure the standing waves have time to reach their peak level. It is problematic to do that with a sine wave sweep as the sweep has to be slow, which other than timing issues within REW also causes the artefacts that exists in a living room to rattle, confusing the measurements further. Remember, it is a large space that is also a kitchen!

 

[hemiutut]

I respectfully disagree. Reducing the bass energy in a room makes the sound unlikeable. Everyone likes bass even if it’s peaky.

If the person doing the equalizing doesn't know what they're doing, it sure sounds bad.
It is very easy to see what the EQ does well in the lower frequencies by looking at the waterfall

Besides, it is not necessary to put any resonator below the schroeder frequency, since with a multisub configuration it is solved.
Do you have measurements made with REW? Can you put the .mdat file?
It is simple curiosity to see the acoustics of the room?.
written with translator

Greetings

 

[-Matt-]

Besides, it is not necessary to put any resonator below the schroeder frequency, since with a multisub configuration it is solved.

I've also tried using MSO (although with only 2 subs). My subjective experience was that by controlling the relative delay of the subs you could smooth out the response a bit but this caused a reduction in the impact of bass. Also MSO suggested too high a level on my rear sub which caused it to be quite localisable. I prefer the bass to come more from the front of the room.

I find that greater bass impact can be achieved by adjusting delays based on the impulse measurements in REW but this can leave peaks in the frequency response (below Schroeder) due to room modes.

The room mode peaks that I see are at the limit of what can be corrected with EQ. If a resonant absorber can bring down those peaks it will likely leave less work for the EQ to do; therefore yielding better results.

(Not an expert on this - just my 2 cents)!

 

[hemiutut]

I've also tried using MSO (although with only 2 subs). My subjective experience was that by controlling the relative delay of the subs you could smooth out the response a bit but this caused a reduction in the impact of bass. Also MSO suggested too high a level on my rear sub which caused it to be quite localisable. I prefer the bass to come more from the front of the room.

I find that greater bass impact can be achieved by adjusting delays based on the impulse measurements in REW but this can leave peaks in the frequency response (below Schroeder) due to room modes.

The room mode peaks that I see are at the limit of what can be corrected with EQ. If a resonant absorber can bring down those peaks it will likely leave less work for the EQ to do; therefore yielding better results.

(Not an expert on this - just my 2 cents)!

SteveGTR 9th March 2017

Here is a new room we just worked on, adding the multi-sub system, with a number of refinements that have produced results that even surprised us. In particular, full range extension from 15Hz, near perfect time alignment and unanimously positive response from a number of pro engineers who had a chance to spent some real time in extended listening. Everyone describes as a new experience of hearing true full range where everything is properly aligned and it 'feels right'. Results attached are before and after the dsp/alignment/tuning process

Main monitors - ATC 20s
Subs- (4) HSU ULS-15 MK2

https://gearspace.com/board/studio-...ng-even-out-freq-response-9.html#post12491247

Greetings

 

[-Matt-]

Here is a new room we just worked on...

Looks great. Not sure if it is a fair comparison with a home system but perhaps when Trinnov is involved...!

How do the impulse measurements look? Are distinct peaks (in the time domain) visible (i.e. one for each sub)?

What is the approximate difference in arrival time (at the MLP) between the impulse peaks for the first sub and the last? Does this span a few ms, or more?

I could believe that having four subs would make the individual time arrival peaks less objectionable than when there are only 2 subs. They could potentially blend together more cohesively.