Subwoofer / Low Frequency Optimization

[Disruptor]

hey,
ive measured my room last week andi think ive done a ok job with my room treatment
those mesurments are bevor applying any eq
Smoothing 1/12

i guess the only solution for the long decay times at around 45hz are bass traps right?

 

[Jag768]

In your amplitude response graph, you set the scale at 20 dB/division, that seems a bit excessive . What kind of room treatment did you apply?

Handling standing waves in a listening room is a complex topic. In the end it boils down to getting the amplitude response as linear as possible. Increasing the number of low frequency sources helps a great deal, see opening post. But for best results a dedicated DSP channel for each sub is required. There is software that can help you set up the DSP, it's called multi sub optimizer. But it takes time to learn to use it.

 

[Disruptor]

P

In your amplitude response graph, you set the scale at 20 dB/division, that seems a bit excessive . What kind of room treatment did you apply?

Handling standing waves in a listening room is a complex topic. In the end it boils down to getting the amplitude response as linear as possible. Increasing the number of low frequency sources helps a great deal, see opening post. But for best results a dedicated DSP channel for each sub is required. There is software that can help you set up the DSP, it's called multi sub optimizer. But it takes time to learn to use it.

Thanks for the answer first of all.
What scale would you recommend for those graphs, first time doing them
And about my room treatment ive build 15 skyline diffusers with the help of the calculator from http://www.mh-audio.nl with those parameters

6 of those in 3x2 are hanging on the front wall and a huge cluster of 3x3 are at the back.
In addition those diffusers ive got 10 Rockwool 100x62x80 pannels with a St/Ve value of 6 scattered around the room

And well to the tipp of adding more subs is kinda tricky because ive got the JBL LSR 305 and the JBL LSR 310s Sub and adding another sub to this without buying another mixer of some sort with 4 outputs and crossovers wouldnt be possible and i think i will upgrade soon ("soon means 1-2 years for me") to either Dutch & Dutch 8c or Genelecs in that pricerange.

 

[Jag768]

P


Thanks for the answer first of all.
What scale would you recommend for those graphs, first time doing them
And about my room treatment ive build 15 skyline diffusers with the help of the calculator from http://www.mh-audio.nl with those parameters View attachment 21025

6 of those in 3x2 are hanging on the front wall and a huge cluster of 3x3 are at the back.
In addition those diffusers ive got 10 Rockwool 100x62x80 pannels with a St/Ve value of 6 scattered around the room

And well to the tipp of adding more subs is kinda tricky because ive got the JBL LSR 305 and the JBL LSR 310s Sub and adding another sub to this without buying another mixer of some sort with 4 outputs and crossovers wouldnt be possible and i think i will upgrade soon ("soon means 1-2 years for me") to either Dutch & Dutch 8c or Genelecs in that pricerange.

So the absorption panels are 80mm thick? When placed against a whall, it will damp approx from 200Hz on up. So while this is helpful to reduce reverb, this won't help you with your low frequency response. In fact, using absorption for <100Hz is very hard to do, that's why almost nobody does it .

For scale, i mostly use 5 dB / division. Well, there are no rules for this, but running the scale from -60 dB till +160 dB is a bit much , you won't see any detail anymore. This is @ my place.

This is an example to show the problem of standing waves and using a single sub in real life. This first graph shows the amplitude response of 4 identical subwoofers measured @ the main listening position. It shows that the resulting amplitude response is dictated by the room resonances rather than the subwoofer itself and is highly dependent on positioning.

The second graph shows the amplitude response of the second subwoofer, the one with the most flat response inroom, at 4 listening positions. Although the positions are quite close to one another, the resultant amplitude response is also highly variable with the level varying approx 4dB.

Using 4 subs, and spending lots of time on tweaking an individual dsp filter for each sub, the variability is greatly reduced. And one can have a flat response at 4 positions. I use delay only for the 2 subs in the back and have equal gain for all 4. Each sub has its own PEQ filters and also low pass settings differ. But there are endless possibilities / permutations, that's why the software that optimizes these settings for you, multi sub optimizer, thanks AndyC . Note, this graph has a slightly different scale, not intentional

I use this software also for integrating subs and fronts

 

[watchnerd]

Thanks so much for posting this.

However, I can't do any of the textbook optimum configs.

So if I can only easily put subwoofers along the wall behind the speakers, should I use 1 in the middle or 2 in the corners?

 

[watchnerd]

Follow up question:

If I have a suspended floor with crawl space, is there any reason to put the subwoofers in the crawl space? Or is that just stupid?

 

[andreasmaaan]

Thanks so much for posting this.

However, I can't do any of the textbook optimum configs.

So if I can only easily put subwoofers along the wall behind the speakers, should I use 1 in the middle or 2 in the corners?

I haven’t followed the entire thread so sorry if I’ve missed something.

According to Harman’s research into sub placement (don’t have the link handy now unfortunately), two in the corners is highly likely to give better results than one in the middle.

Follow up question:

If I have a suspended floor with crawl space, is there any reason to put the subwoofers in the crawl space? Or is that just stupid?

Would it save needed space or allow you more flexibility in terms of placement?

 

[watchnerd]

Would it save needed space or allow you more flexibility in terms of placement?

In theory, I could possibly go to a 4 corners placement, although I don't know the downsides of having the subs under the floor.

 

[andreasmaaan]

In theory, I could possibly go to a 4 corners placement, although I don't know the downsides of having the subs under the floor.

I can’t imagine any inherent downsides. how would you do it specifically though?

 

[watchnerd]

I can’t imagine any inherent downsides. how would you do it specifically though?

I'd have to crawl under and look. Some kind of bracket mount maybe.

 

[andreasmaaan]

I'd have to crawl under and look. Some kind of bracket mount maybe.

Are there grills or openings of some sort through the floor though?

 

[watchnerd]

Are there grills or openings of some sort through the floor though?

only for heater vents, so no.

 

[andreasmaaan]

only for heater vents, so no.

That would be the issue then IMO. The floor itself would block a lot of the output from the subs unless you had them firing through it somehow.

 

[amirm]

Follow up question:

If I have a suspended floor with crawl space, is there any reason to put the subwoofers in the crawl space? Or is that just stupid?

Crawl space volume can be used for ultra-low-frequency subs like rotary. You can also put regular subs there but keeping them from rattling and such would be work. You would also have to design custom subs for this.

If you want to hide the subs, you can get wall mounted ones that fit between the studs.

 

[amirm]

So if I can only easily put subwoofers along the wall behind the speakers, should I use 1 in the middle or 2 in the corners?

Assuming your room is a square, this is what the performance is for various number and locations of subs:

#3 is one sub in the middle. #4 is one sub in each front corner. I am surprised that their performance is so close to each other. Usually placing them in the corner gives you higher gain so two in the corner should have had more LF output.

If your room is not square/rectangular, none of these recommendations work. You would ideally have a smart audio-eq that can optimize all of them in which case you can put them where it is convenient.

 

[andreasmaaan]

Assuming your room is a square, this is what the performance is for various number and locations of subs:

View attachment 23788

#3 is one sub in the middle. #4 is one sub in each front corner. I am surprised that their performance is so close to each other. Usually placing them in the corner gives you higher gain so two in the corner should have had more LF output.

If your room is not square/rectangular, none of these recommendations work. You would ideally have a smart audio-eq that can optimize all of them in which case you can put them where it is convenient.

Thanks for posting that. I stand corrected on my post #27. Should have looked it up rather than going off my memory.

 

[watchnerd]

Assuming your room is a square, this is what the performance is for various number and locations of subs:

View attachment 23788

#3 is one sub in the middle. #4 is one sub in each front corner. I am surprised that their performance is so close to each other. Usually placing them in the corner gives you higher gain so two in the corner should have had more LF output.

If your room is not square/rectangular, none of these recommendations work. You would ideally have a smart audio-eq that can optimize all of them in which case you can put them where it is convenient.

Thanks.

What is 'LF factor' in that graph?

BTW, the room is 22' x 15', but has 3 openings, a fireplace, and a sloping ceiling that goes from 10' to 15'.

 

[amirm]

What is 'LF factor' in that graph?

It is the amount of low frequency power. Some configurations work well as far as removing variations but are not very efficient. LF shows the efficiency factor. Corner placement of subs usually results in better LF although sometimes that energy is used to cancel out modes.

 

[Soniclife]

BTW, the room is 22' x 15', but has 3 openings, a fireplace, and a sloping ceiling that goes from 10' to 15'.

Have a play with the room sim in REW, see if it correlates at all with in room measurements for you, I found it useful, but my room is a simple shape.

 

[watchnerd]

Crawl space volume can be used for ultra-low-frequency subs like rotary. You can also put regular subs there but keeping them from rattling and such would be work. You would also have to design custom subs for this.

If you want to hide the subs, you can get wall mounted ones that fit between the studs.

JL Audio apparently also has new ceiling mounted models:

http://www.jlaudio.com/ics-sys-208-home-audio-in-ceiling-subwoofer-systems