How to start measurements when you have multiple subs

[thsmith]

REW is working for me now and no more manual measurements, yahooooo!

My room (Living room)as most everyone elses is challenging, 4200cf, 8' to 12' sloping ceiling, hardwood floors, fireplace is 10' wide and 12' high. 6' frech door, all windows have heavy drapes and large opening in back of the room to the right from sitting position.

I have a HSU VTF3-MK3 Turbo in front left corner and HSU MBM-12s behind each main.

When I start my measuring I know I need to remove the mains, should I also turn off the MBMs and focus on just the 3 3 T and then turn off 3 3 T and turn on 1 MBM at a time to find best location for subs ?

3 3 T XO is in set at 55hz
MBMs XO out (50hz-150hz)
AVR (Denon 2808) XO set to 120hz

Thanks

[thsmith]

ANyone with past experience doing testing with multiple subs ?

Thanks

[weverb]

Mine was done with one Outlaw EX and one MBM-12. Here is one post I did where I compared the three different scenarios.

http://www.hometheatershack.com/foru...tml#post113906

[brucek]

ANyone with past experience doing testing with multiple subs ?

Your situation is not considered multiple subs. You have a low sub and a couple mid subs.

It's a very difficult job to properly integrate this arrangement into a set of mains, given the obvious time and phase hurdles that have to be overcome.

I would test each sub individually at first, simply to get an idea of how their position is interacting with the room, but I wouldn't get too crazy about trying to get a perfect response at this stage, because you're going to have to get them to play in concert eventually and they will more than likely not react in your favour.

Your low will have to be average phased with the two mid subs, since they're not co-located. Then the phase of each mid will have to be phased with the mains. Since you have them close to each main (and not beside your couch where it is recommended), then this will work in your favour for phasing. You may want to isolate a measure between a mid and its associated main to set the initial phase of each mid.

brucek

[thsmith]

Thanks Weverb, I have been following that thread.

After more thought I think I will raise my AVR XO to max

Then with measure just the 3 3 T on and XO out do a measurement

Then do the same for each MBM

and see where I have overlap and gaps.

Once I get to a happy place I want to read more about applying filters to see the changes, I think that is what you did before buying an BFD.

[thsmith]

Thanks Bruce, many things to consider and try. For some reason I always seem to do things the hard way.

I tried the MBM in nearfield and did not like it, most likely the large opening to the right and behind me.

The really cool thing is that REW makes taking measurements so much more accurate, fast and easy as opposed to the way I have been doing it with RS meter, Freq cd and Excel.

[weverb]

thsmith wrote:

Thanks Weverb, I have been following that thread.

After more thought I think I will raise my AVR XO to max

Then with measure just the 3 3 T on and XO out do a measurement

Then do the same for each MBM

and see where I have overlap and gaps.

Once I get to a happy place I want to read more about applying filters to see the changes, I think that is what you did before buying an BFD.

Let me know if I can help. Have you done the typical pink noise/RS meter 75dB calibration of...

1. Main sub to highs.
2. One MBM to highs.
3. Other MBM to highs.
4. Both MBM's to highs.
5. All subs to highs.

One of your previous graphs looked like your 3.3 was playing really low compared to the MBM mid-bass. You are going to have a lot of fun playing. You have different positions to try out, with and without turbo to try, and max output versus max extension to try. Good luck.

[weverb]

thsmith wrote:

TAfter more thought I think I will raise my AVR XO to max

I would probably not go past 120Hz. There are are a few on the avsforum that have had good luck/response with this setting.

[thsmith]

weverb wrote:

Let me know if I can help. Have you done the typical pink noise/RS meter 75dB calibration of...

1. Main sub to highs.
2. One MBM to highs.
3. Other MBM to highs.
4. Both MBM's to highs.
5. All subs to highs.

One of your previous graphs looked like your 3.3 was playing really low compared to the MBM mid-bass. You are going to have a lot of fun playing. You have different positions to try out, with and without turbo to try, and max output versus max extension to try. Good luck.

If you are referring to balancing the subs with the mains using RS SPL meter, yes I have.

The 3 3 T looks low because I have not applied the SPL meter calibration/compensation file yet. Plan to do that tonight.

I will certainly be picking your brain on setting filters to predict what a BFD can do for me.

Thanks again.

[thsmith]

Bruce, I see what you mean about the sub and MBMs not playing well together. With all 3 on I have a bad suck out at 50hz but individually they look good in that area.

1st graph with 3 3 T and both MBMs on
2nd graph with just 3 3 T on
3rd graph just MBMs on
4th graph just left MBM on
5th graph just left MBM on

[thsmith]

Interesting that with 33T and Left MBM phase set to 180 and Right MBM phase set 0 it looks better.

[weverb]

Have you added the correction file yet? Why does your graph stop before 200Hz?

[weverb]

Also, how are your MBM's playing down to 15Hz. They should drop like a brick after 50Hz.

[thsmith]

agree and why does the 33T play way past 60hz with XO in and set to 60hz ? I remember in one of your post you thought your receivers XO was not working. My case it looks like the AVR, sub and MBMs XO are not working.

Any ideas, could it be a REW or Sound card problem with setup?

[thsmith]

weverb wrote:

Have you added the correction file yet? Why does your graph stop before 200Hz?

Yes, SPL calibration file was loaded, sweep was from 15hz to 135hz. Since I had the mains disconnected I fegured it made no difference to focus on just that range.

Any issues doing this ?

[salvasol]

thsmith wrote:

agree and why does the 33T play way past 60hz with XO in and set to 60hz ? I remember in one of your post you thought your receivers XO was not working. My case it looks like the AVR, sub and MBMs XO are not working.

Any ideas, could it be a REW or Sound card problem with setup?

I just want to share this thread ... there's some post that talk about the crossover on the subwoofer and AVR ... they said that crossover is not a brick wall, and that speakers and subs will keep playing beyond the crossover frequency

[weverb]

I agree about the xo not being a brick wall as the frequency increases, but the MBM was design to fall off after 50Hz. It should not continue down to 15Hz. If you look at my post with just the MBM graph (linked to before) you can see how it did not respond after about 40Hz.

The 3.3 looks realistic.

What level are you calibrating to with REW? 75dB?

Taking a note from brucek's advice book, have you tested your sound card calibration file to make sure you get a flat line?

[weverb]

Have you tested different placement options with the 3.3 to try and get rid of that dip?

[thsmith]

weverb wrote:

I agree about the xo not being a brick wall as the frequency increases, but the MBM was design to fall off after 50Hz. It should not continue down to 15Hz. If you look at my post with just the MBM graph (linked to before) you can see how it did not respond after about 40Hz.

The 3.3 looks realistic.

What level are you calibrating to with REW? 75dB?

Taking a note from brucek's advice book, have you tested your sound card calibration file to make sure you get a flat line?

Agree with the MBM measurements. Not sure what is going on but will investigate. I was calibrating at 76hz. Below is a graph of loaded calibration files for SPL and Soundcard, dash is Soundcard. I am using the Turtle Beach SMR but no issues with calibration.

weverb wrote:

Have you tested different placement options with the 3.3 to try and get rid of that dip?

Not with REW but that will be first order of business this weekend if not sooner.

[weverb]

Try a measurement of your loopback cable to test your soundcard cal file, and remove the SPL meter calibration file and uncheck "c weighting". Make sure you are getting as flat a line response as possible. Reference the last graph on my page 6 of my post to see what I mean.

[thsmith]

weverb, cleared Soundcard cal, unchecked c weight and cleared spl cal.

Here is a screenshot of the settings page just before soundcard cal and the graph. Looks as it should compared to Brucek's, I have the TB SRM card like brucek.

See anything wrong?

Thanks,

[weverb]

Looks good. Now take a measurement of it.

[thsmith]

With C weight unchecked and SPL cal still unloaded ?

Thanks for your help !

I can not say enough about the usefulness of REW.

[brucek]

With C weight unchecked and SPL cal still unloaded ?

Yes, it should be a flat line.

See anything wrong?

No, everything looks good.

sweep was from 15hz to 135hz

Measure subs with a sweep from 0Hz-200Hz.

but the MBM was design to fall off after 50Hz. It should not continue down to 15Hz.

The response looks about like I would suspect. It does drop off at the assigned 50Hz. Below that the remaining signal is likely enjoying room gain. There also may be some low frequency noise in the room. I don't see a probelm with the MBM response. Take a near field with the sub in the middle of the room (or outside even better) to get a clearer picture.

I see what you mean about the sub and MBMs not playing well together

Ever considered an 80Hz crossover and the 3 3 T as your only sub and not use the MBM's. The 3 3 T is certainly capable enough. What is your intension/goal with the MBM's?

You do need to turn down the level of the MBM's in relation to the low sub. They're too high to integrate well with the low sub from the graphs you've posted so far. They're both peaking over 80dB. Turn them down.

As a side note on REW, it's a lot easier to evalute responses of each sub if you adjust the REW cutoff target line to the desired crossover. So, if you are testing the low sub, set the target line at 50Hz or 60Hz (there is no 55Hz) and when testing the MBM set the target at 120Hz. It has no effect (except when creating filters), but it helps you visualize how close you are to the desired target.

brucek

[weverb]

brucek wrote:

The response looks about like I would suspect. It does drop off at the assigned 50Hz. Below that the remaining signal is likely enjoying room gain. There also may be some low frequency noise in the room. I don't see a probelm with the MBM response. Take a near field with the sub in the middle of the room (or outside even better) to get a clearer picture.

I understand having some room gain, but 70-72dB at 18Hz!?! Is there a way to test for "low frequency noise in the room"? Can you turn the highs and lows off and run a measurement? Would that show you anything?