# Sub Placement measurements



## TigerGenetics (Jun 17, 2014)

Hi all, I have finally gotten around to taking some test measurements for my sub setup (IB). I took measurements at 6 positions and need some help deciding which one may work best. 

Thanks for any input, advice, and opinions!


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## Phillips (Aug 12, 2011)

Middle left of centre looks the best. 

The peak is a room mode about 38hz.

Do you have EQ, adjustable or AVR that has EQ?


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## TigerGenetics (Jun 17, 2014)

Phillips said:


> Middle left of centre looks the best.
> 
> The peak is a room mode about 38hz.
> 
> Do you have EQ, adjustable or AVR that has EQ?


I definitely noticed the room mode peak. I have a Pioneer Elite SC-79 receiver but I am planning to run the sub-EQ through the Behringer FBQ1000 (new version of DSP1124P I believe). 

The main point regarding the middle locations (last three graphs) is that those were all done near a ceiling fan. Would the outlet of these subs being above the blades of the fan cause any issues?

Thanks!


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## TigerGenetics (Jun 17, 2014)

Quick question, should I redo my measurements so that they are more along a lower level, such as 75dB or should I be fine with what I have for applying the filters?


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## Phillips (Aug 12, 2011)

75-80db is fine, option is to measure the noise by simply using the SPL meter in REW with no test signal.

Turn them off then re-measure if results do show there is noise of the fans. 

Another option is to use the RTA (real time analyser) to find the best position this saves taking a lot of measurement's, then fine tune with the sweep (normal measurements).

I would try the Pioneer to EQ, how old is it? If it has Audyssey it is generally good.


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## TigerGenetics (Jun 17, 2014)

Phillips said:


> 75-80db is fine, option is to measure the noise by simply using the SPL meter in REW with no test signal.
> 
> Turn them off then re-measure if results do show there is noise of the fans.
> 
> ...


The Pioneer uses MCACC. 

Pardon the newbie question, but how do I utilize the RTA function? Meaning, what factors do I look for with that test? This may be a good option along with the measurement sweeps to find the optimal location. Once I find the best spot, there is going to be a rather large hole in my ceiling and I would really like to get it done right the first time. haha


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## red99 (Dec 10, 2014)

TigerGenetics said:


> The Pioneer uses MCACC.
> 
> Pardon the newbie question, but how do I utilize the RTA function? Meaning, what factors do I look for with that test? This may be a good option along with the measurement sweeps to find the optimal location. Once I find the best spot, there is going to be a rather large hole in my ceiling and I would really like to get it done right the first time. haha


I could be wrong since Im a newbie with all of this, but I am assuming he is referring to TrueRTA Audio Spectrum Analyzer software. I haven't read anywhere of REW using Real Tiime.


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## JohnM (Apr 11, 2006)

red99 said:


> I could be wrong since Im a newbie with all of this, but I am assuming he is referring to TrueRTA Audio Spectrum Analyzer software. I haven't read anywhere of REW using Real Tiime.


REW RTA Window.



> how do I utilize the RTA function?


The RTA is best used with REW's Pink PN test signal, so you get an SPL trace that doesn't need any averaging. Look for the same things as in a sweep measurement SPL plot. Here are suitable RTA settings:


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## red99 (Dec 10, 2014)

I just noticed tonight that REW does have RTA and came back to post that. Thanks John for correcting me. 
As I said, Im a Newbie to this.


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## TigerGenetics (Jun 17, 2014)

Join the newbie club haha. 

I feel like I get the idea of the RTA, but what is the best approach to get the readings? I use the Pink PN test signal and just move the mic (umik-1) around until I find the best response? I assume this would be similar to individual measurements using "sweeps", but in a more dynamic manner?


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## Phillips (Aug 12, 2011)

TigerGenetics said:


> Join the newbie club haha.
> 
> I feel like I get the idea of the RTA, but what is the best approach to get the readings? I use the Pink PN test signal and just move the mic (umik-1) around until I find the best response? I assume this would be similar to individual measurements using "sweeps", but in a more dynamic manner?


One way is to place the sub at your listening position (this saves lugging the sub around) then move the mic around where you can place the sub, where the best location is place the sub there. All this using RTA.

RTA basically gives you real time measurement's (live)


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## TigerGenetics (Jun 17, 2014)

Phillips said:


> One way is to place the sub at your listening position (this saves lugging the sub around) then move the mic around where you can place the sub, where the best location is place the sub there. All this using RTA.
> 
> RTA basically gives you real time measurement's (live)


Ok that makes sense and was in line with what I was thinking. The good news is the measurements posted were done with the sub at the listening position and holding the mic about 6" from the ceiling in the desired locations. I will test with the RTA soon and compare the sweeps I ran prior.


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## TigerGenetics (Jun 17, 2014)

I finally got around to taking a few more measurements, this time using RTA to try and locate a "sweet spot".

I have narrowed it down to two locations, most likely with a 4-sub cube manifold. 

My main question is how far back is too far for IB in-ceiling setups? The location I am looking at primarily is roughly 4-5 feet in front of the main listening point. The front location is between the two mains and the same distance from the wall (~2 feet).

I am attaching the various graphs for review. The graphs show no smoothing and 1/6 smoothing at each position and also an overlay for a direct A-B comparison.


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## Talley (Dec 8, 2010)

TigerGenetics said:


> Join the newbie club haha.
> 
> I feel like I get the idea of the RTA, but what is the best approach to get the readings? I use the Pink PN test signal and just move the mic (umik-1) around until I find the best response? I assume this would be similar to individual measurements using "sweeps", but in a more dynamic manner?


being in houston why don't u figure it all out then come over to my place and help me. I'm told my Umik-1 mic will ship out later this week so hopefully next week I can start taking measurements. Want to do that bare and then start doing some treatments.


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## TigerGenetics (Jun 17, 2014)

Bmxer241 said:


> being in houston why don't u figure it all out then come over to my place and help me. I'm told my Umik-1 mic will ship out later this week so hopefully next week I can start taking measurements. Want to do that bare and then start doing some treatments.


Ha! You seem to have more faith in me than I do haha. I sit in bed at night for hours reading this forum and "The IB Cult" trying to figure all this stuff out. I must say, this forum has provided me with so much information that I am still trying to take it all in. Wayne P.'s technical articles and how-to's, along with brucek's articles have been invaluable. 

I am always willing to help, even if it just holding a microphone in place.


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## nwf477 (Feb 8, 2015)

This is what I did based on some suggestions. All of this is on REW, go to Generator select Pink Pn hit play. Next go to RTA select record button now the fun part move the sub around till you find the smoothest response. I know for a fact the moving stinks but you will find a good location based on the RTA. Word of warning do not remove the furniture and do this because once you think you are set and you decide to check after furniture is back all the moving you did was for nothing.


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## TigerGenetics (Jun 17, 2014)

nwf477 said:


> This is what I did based on some suggestions. All of this is on REW, go to Generator select Pink Pn hit play. Next go to RTA select record button now the fun part move the sub around till you find the smoothest response. I know for a fact the moving stinks but you will find a good location based on the RTA. Word of warning do not remove the furniture and do this because once you think you are set and you decide to check after furniture is back all the moving you did was for nothing.


The graph labeled "Back" is the smoothest response I found using the Pink PN with RTA that you mention. My concern is that it is closer to the back of the room, but not behind the LP. It is actually about 4-5 feet in front of the LP.


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## Talley (Dec 8, 2010)

Well... 4-5' from the LP will give you a good impact. more of a hit since it's close.

one tip I can offer is going to harbor freight and buying a less than $20 cart: http://www.harborfreight.com/movers-dolly-39757.html

then put the sub on this and then you can roll it around and not have to pick it up or nothing. Ya even on carpet it may be a pain to roll but pushing is better then lifting.


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## TigerGenetics (Jun 17, 2014)

Bmxer241 said:


> Well... 4-5' from the LP will give you a good impact. more of a hit since it's close. one tip I can offer is going to harbor freight and buying a less than $20 cart: http://www.harborfreight.com/movers-dolly-39757.html then put the sub on this and then you can roll it around and not have to pick it up or nothing. Ya even on carpet it may be a pain to roll but pushing is better then lifting.


I'm placing the sub at the LP (it's in a 24"x24" sealed box) and using the RTA to move around the room, holding the microphone at various points that make sense (areas that the sub can be mounted due to space restrictions from the slope of the roof, where joists are, etc). I'm holding the mic 6" from the ceiling and watching the graphs change at each location. The position that was closest to the LP seemed to be flatter while the position up front showed a nasty room mode peak around the 40Hz point, but that can be tamed most likely with my FBQ1000.


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## AudiocRaver (Jun 6, 2012)

You have an interesting situation with your sub-in-ceiling approach. Not sure how well the "sub crawl" will work to predict IB or in-ceiling location. Mic close to boundary is at high-pressure, low-amplitude point. Your actual situation with subwoofer there will be a low-pressure, high-amplitude point, so wavelengths are different. At least that's the way it seems to me, someone correct me if I'm looking at it wrong. Just hate to see you make your decision and have the result be way different from what you are expecting.


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## TigerGenetics (Jun 17, 2014)

AudiocRaver said:


> You have an interesting situation with your sub-in-ceiling approach. Not sure how well the "sub crawl" will work to predict IB or in-ceiling location. Mic close to boundary is at high-pressure, low-amplitude point. Your actual situation with subwoofer there will be a low-pressure, high-amplitude point, so wavelengths are different. At least that's the way it seems to me, someone correct me if I'm looking at it wrong. Just hate to see you make your decision and have the result be way different from what you are expecting.


I'm following guidelines in the IB FAQ section as well as from the IB Cult forums. I know it isn't perfect but it should get me pretty close.


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## AudiocRaver (Jun 6, 2012)

Well, they are the ones who should know how it is done.:bigsmile:


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## TigerGenetics (Jun 17, 2014)

AudiocRaver said:


> Well, they are the ones who should know how it is done.:bigsmile:


I sure hope so. I'm about to put a large hole in my ceiling. Haha


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