# Sub-woofer Placment verses Room treatment



## trcns (Sep 15, 2015)

From one of my previous posts I was advised to read an article "THE SCIENCE BEHIND SUBWOOFER PLACEMENT". There is no doubt what great article it is. But usual more I read more confused I am. Here I will not ask all question came up after read the article and the areas got lost.

Questions I have is; who important these calculations are, after placing base traps in a room?


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## tesseract (Aug 9, 2010)

trcns said:


> From one of my previous posts I was advised to read an article "THE SCIENCE BEHIND SUBWOOFER PLACEMENT". There is no doubt what great article it is. But usual more I read more confused I am. Here I will not ask all question came up after read the article and the areas got lost.
> 
> Questions I have is; who important these calculations are, after placing base traps in a room?


Hello, Tajammul.

The calculations are a rough guide, based on perfect rooms. Few rooms are perfect. Have you measured you actual room response? That would help not only with speaker placement, but guide the room treatment process, as well.


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## trcns (Sep 15, 2015)

I am very new to this side of technology, so

Have you measured you actual room response? That would help not only with speaker placement, but guide the room treatment process, as well.

If measuring Room Response means "Using REW and taking measurements for each speaker. Yes I did.

I saw plenty of videos on how to take the measurements, all over the YouTube. Believe or not I read the whole REW user guide.

I can see and understand where are the peaks and null, but there is no guide line I could find, which says okay to eliminate this peak/Null move your speaker/subwoofer here.

After these readings every body jumps into selling base traps and diffusers. Is there a guide translating measurements into speaker placement?


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## Lumen (May 17, 2014)

trcns said:


> I can see and understand where are the peaks and null, but there is no guide line I could find, which says okay to eliminate this pick/Null move your speaker/subwoofer here.


Try this article about the "subwoofer crawl." Then come back with questions. We love questions! :bigsmile:



trcns said:


> After these readings every body jumps into selling base traps and diffusers. Is there a guide translating measurements into speaker placement?


Please post a link to the thread, so the accuracy of the information can be reviewed. Thanks!


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## tonyvdb (Sep 5, 2007)

Can you post your REW results? that would be very helpful in giving you some guidance.


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## Blacklightning (Nov 22, 2011)

Lumen said:


> Try this article about the "subwoofer crawl." Then come back with questions. We love questions! :bigsmile:


I have not tried this but try a sub crawl with measurements. Place the Sub in the LP and remove the mic around the room and measure in different sub spots.

Most room treatments will not touch bass (below 50hz) and that includes bass traps so placement is key.


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## trcns (Sep 15, 2015)

I understand the subwoofer crawl, and I believe subwoofers are placed at their best possible place. I just finished re-arranging the room and now I am working on the room treatment, the readings are without room treatment. Attached are the Sub Woofer measurements.


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## Blacklightning (Nov 22, 2011)

What are the models of the two subs that you are using? and what is the crossover frequency you are using?

From what I can see your bass looks like it will suffer from One Note bass.


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## trcns (Sep 15, 2015)

One is Rel G1 and the second is PSB SubSonic which I originally had. REL was connected with high level input as well as LFE. PSB is connected via LFE. When I took the readings. Crossover for high level is set for 45hz inside the REL sub. LFE is set for 80 hz in the Mcintosh MX 121 prosessor. Last night I removed LFE form REL. but the result remains the same.


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## tonyvdb (Sep 5, 2007)

Your trying to blend two very different subs and thats going to be a real challenge. I would suggest removing the PSB and put it aside for other use. The REL is a far superior sub and placed properly in your room should produce a much smoother response than what you have with the PSB added.


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## rab-byte (Feb 1, 2011)

If you plan to keep both subs I'd suggest only using the rel as an extension of the mains. Feed LFE to the other sub. 

Keep the rel as centered with the mains as possible and adjust crossover and phase for the mains first then address the other sub as a single sub solution. 

This would be ideal for 2ch playback and let the other sub handle deep bass for movies.


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## Blacklightning (Nov 22, 2011)

trcns said:


> I believe subwoofers are placed at their best possible place. I just finished re-arranging the room and now I am working on the room treatment, the readings are without room treatment. Attached are the Sub Woofer measurements.


I agree with Tony, work with just the REL for now. Find the spot in your room that keeps that 45hz peak at a minimum. 

Most room treatment that you might add will not touch the Rel's frequency range in your room.
Can you place your sub in a couple different places in the room and run some tests?


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## Lumen (May 17, 2014)

Lumen said:


> Try this article about the "subwoofer crawl."





Blacklightning said:


> I have not tried this but try a sub crawl with measurements. Place the Sub in the LP and remove the mic around the room and measure in different sub spots.
> .
> .
> Can you place your sub in a couple different places in the room and run some tests?





trcns said:


> I understand the subwoofer crawl, and I believe subwoofers are placed at their best possible place.


Looks like I was mistaken about the sub crawl. See this thread for more info why measurements are more important than listening.


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## trcns (Sep 15, 2015)

Okay so PSB Sub woofer is gone, not only from my system but also from my home. So I will not be tempted to put it back again.

Now Next: Since my crossover frequency is set for 45HZ in the Sub woofer and it is connected through High Level input.

Should my measurements limit from 18HZ to 45 HZ or will they be from 20HZ to 100HZ or 150HZ?


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## Blacklightning (Nov 22, 2011)

trcns said:


> Should my measurements limit from 18HZ to 45 HZ or will they be from 20HZ to 100HZ or 150HZ?


You should run it from 15Hz to 200Hz with your speakers on and off.
I understand you have the Rel hook up two ways at once but will your LFE channel be played at full range below 120Hz?


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## trcns (Sep 15, 2015)

Rel Tech Support asked me to set LFE crossover to 200HZ.


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## Lumen (May 17, 2014)

Are you sure it's the LFE crossover? According to the REL-G1 User Manual, the LFE circuit passes the .1 low-level input signal through with only the required 120Hz fourth-order crossover. The crossover control on the REL G1 is accessible only via its remote control, and affects only the High-Level (Speakon) and Low-Level (RCA) inputs. The .1 LFE input is isolated from that circuit.

Unaware of the entire conversation between you and REL, I can only guess at answering your last post. I imagine REL told you to peg the crossover at it's highest setting because they concluded it was beneficial to your situation, and that it would let your AVR handle all crossover functions. For (simplified) example: if your AVR was set to cross from sub to mains at 80Hz, then the AVR's bass management would pass everything below 80Hz to the sub and everything above to the mains. But you also have the High-Level Speakon input connected, so the sub receives the same signal as the mains - essentially bypassing the AVR's bass management. So you'll have audio signals between 80Hz and 200Hz playing through both the mains and the sub. That can create an artificial bass boost which may not be pleasing to your ears.


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## trcns (Sep 15, 2015)

This the advice i got 

Hello Tajammul,

Thank you for the email, there are a few items we need to go over before we answer your question.


1. The first thing we need to check is the lfe cutoff on your processor. Can the MX 121 be set any higher? Some older units can't but if yours can, please set it to 200 HZ not 80 HZ.

2. Second, the configuration of the subwoofer in the processor needs to be checked. You do not want the processor sending bass to both the lfe and the main speakers. Please make sure to set the subwoofer settings in the processor to YES, not both. To answer your question one input does not supercede another.Explain it fully.
Think of the high level connection as something that simply turns your 802 into a (truly) full range speaker.This is true and beneficial for both music and movies.
The .1 is a special effects channel for movie-only bass. When these signals occasionally (it is much less frequent than you think) come along the REL simultaneously reproduces these. How? In the same way that sound mixing boards at rock converts shove many channels through the same towers of speakers at the same time.


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## tonyvdb (Sep 5, 2007)

I dont understand their thinking of setting the processors crossover at 200Hz, that would send frequencies to the sub that would make it sound like mud. 80Hz is the recommended setting by many professionals including THX as anything higher make the subwoofer heard not just felt and that makes placement even harder. 
Disconnect the PSB and put the REL on the LFE (sub out) channel. the MX 121 will route anything below 80Hz to the sub. not just the dedicated .1 of the movie soundtrack (unless you use direct mode)


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## Blacklightning (Nov 22, 2011)

tonyvdb said:


> I dont understand their thinking of setting the processors crossover at 200Hz, that would send frequencies to the sub that would make it sound like mud. 80Hz is the recommended setting by many professionals including THX as anything higher make the subwoofer heard not just felt and that makes placement even harder.


I think they are talking about the LFE crossover which in most newer AVR can only be set at 120hz or lower. The Small Speaker crossover will still be set at 80hz (or what ever you want)


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## RTS100x5 (Sep 12, 2009)

I always recommend dual subs (same subs / not different ) This method, unscientific as it may be, nearly always creates a much more even bass response in a given listening area - and then using REW or Audessy and the like, can really smooth out the frequency peaks and nulls....


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## trcns (Sep 15, 2015)

So finally, After getting rid of PSB Subwoofer, and moving speakers around and installing five base traps in this room. Attached are the measurements I took after completion. How can I fix the nulls and peaks?


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## Blacklightning (Nov 22, 2011)

trcns said:


> So finally, After getting rid of PSB Subwoofer, and moving speakers around and installing five base traps in this room. Attached are the measurements I took after completion. How can I fix the nulls and peaks?


Okay first thing first, I'm guessing 1,2,3 are 3 different positions?

Does your room have lots of sound proofing?

Your distortion is crazy high. For distortion Position 1 is the best.
Your Sub level seems really high but I can't really tell without a full range measurement.

Run your sub in position 1 and run 7 tests:
Sub only again 14hz to 200Hz
Sub L 14hz to 20000hz
Sub R 14hz to 20000hz
Sub with both speakers
Speaker L No Sub 14hz to 20000hz
Speaker R No Sub 14hz to 20000hz
Both Speakers No Sub 14hz to 20000hz


Right now your system is setup in your Music mode with the 45hz crossover with your speakers running full range. (I'm I correct?)
At some point you will need to run this test again in HT mode.
Also the Right side of your room seems to be handling bass a lot better in your room.
Can you take a picture of your layout?


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## Blacklightning (Nov 22, 2011)

something really weird is going on in your room. Maybe someone with more experience will chime in.
Not much decay happening in your room.


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## trcns (Sep 15, 2015)

No I did not move any thing. I just took three samples each device. I also have reading from 15 Hz to 20000Hz, I can post them as well.


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## Blacklightning (Nov 22, 2011)

trcns said:


> I just took three samples each device.


Okay what is going on the graphs should all look the same then????

Please explain or take pics of the setup.


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## trcns (Sep 15, 2015)

Okay, will post tonight.


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## trcns (Sep 15, 2015)

Attached are the new readings, each reading is based on 8 swipes.

I also attached the pictures of the room. I replace the blinds with curtains, added base traps, all pictures and paintings are 2" thick base traps. Both speakers are 20" to 25" away from side walls and about 50" away from back wall. Room dimensions are 15'.10" wide, 24'.8" long and 8' high.


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## Blacklightning (Nov 22, 2011)

Sorry, I took so long to get back to you. First, I think I'm in over my head because I'm not sure what is going on with your Mic and readings.

1. Just looking at your room, the Layout is perfect. I would not change a thing.
2. Your speakers are full range and I would not run a sub while playing Music. 
3. Your Delay graph shows that your room is holding on to frequencies under 200hz.
4. Your Distortion seems really high. This might be the Mic or the Room as your speakers should not have this kind of distortion.
5. RT60 I have no idea what this means but it's way different than mine.
6. Your Spectrogram is also crazy

I don't have any advice for you as your Data looks really off.
Sorry.


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