using a sealed sub with OB subs

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mlundy57

using a sealed sub with OB subs
« on: 10 Oct 2018, 04:09 pm »
I'm wanting to try adding a sealed sub at the back ot the room to my OB H-frames/NX-Otica monitors. I actually have the sub in the back of the room for HT use.

I tried connecting it up but it did not work. The sub output was almost non existent regardless of where I had the phase control set. It also diminished the output from the H-frames. I'm not sure if splitting the signal from the preamp caused this or what. I have done this in the living room system before when I was working with the X-CS Encore/best speaker stand combo and it worked. But there were some differences between that system and my listening room system.

First off is the sub amp. In the living room system, the sealed sub amp is an A370PEQ3. This has two pairs of inputs, LFE inputs and L&R Line in inputs. The sealed sub in the listening room system has an A370PEQ amp. This amp has only one set of inputs.

My preamp has two sets of outputs, one balanced and one single ended. In the normal configuration I run the balanced inputs to the power amp that feeds the NX-Otica monitors and the single ended inputs to the A370PEQ3 amps for the H-frames.

What I tried doing was adding Y adapters to the single ended outputs from the preamp and since the HT receiver was connected to one of the sealed sub's line level inputs used another Y adapter at the sub.  I did not try removing the receiver interconnect and using both L&R ine level inputs on the sub. I probably need to try that next and see what happens.

Mike


HAL

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Re: using a sealed sub with OB subs
« Reply #1 on: 10 Oct 2018, 04:29 pm »
Mike,
If I read that correctly, putting a Y adapter at the sub to sum the R-L signal at the sub will not work, to sum two different outputs together.  Basically sounds like the preamp output is shorting the channels together.   Most likely the balanced outputs are buffered from the single ended outputs, so the balanced might still work correctly

Try running the R-L Y SE outputs from the preamp directly to the R-L inputs on the A370PEQ sealed sub without any other inputs and see what happens. 

You should then be able to reverse the polarity of the rear sub to give it a try.

Hope that helps.


mlundy57

Re: using a sealed sub with OB subs
« Reply #2 on: 10 Oct 2018, 08:21 pm »
Unplugging the AVR interconnect then using both L&R inputs on the sub amp (no Y connector at the sub) worked for getting the output from the sealed sub. However, using the Y adapters to split the single ended signal from the preamp resulted in a 20-25dB output drop from the OB subs. I have some room to increase the gain on the OB amps as they are both currently at 1 o'clock.

I'm not sure how well this is going to work. When I level match so the OB subs and the sealed subs are both reading 55dB on a SPL meter, the sealed sub sounds much louder. This could be due to location. The sealed sub is sitting next to my chair while the OB subs are 8' away. It's funny though. The SPL meter "hears" them at the same level but my ears do not.  :scratch:

Mike


Early B.

Re: using a sealed sub with OB subs
« Reply #3 on: 10 Oct 2018, 09:53 pm »
I'm not sure how well this is going to work. When I level match so the OB subs and the sealed subs are both reading 55dB on a SPL meter, the sealed sub sounds much louder. This could be due to location. The sealed sub is sitting next to my chair while the OB subs are 8' away. It's funny though. The SPL meter "hears" them at the same level but my ears do not.  :scratch:

Mike -- I hope you get this sorted out. I tried adding a third sub (actually my HT sub in the back of the room, just like your setup) and when it worked, it worked great!!!!  I kept running into various problems, much like you're experiencing. I realized, though, to really make it work well, I needed (ummm...wanted) a dedicated sealed servo sub with an A370 amp. This will be my next major upgrade. I want to try it again. With a 3rd sub, the dynamics are on another level.

poseidonsvoice

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Re: using a sealed sub with OB subs
« Reply #4 on: 10 Oct 2018, 10:21 pm »
Mike,

Upload the measurements when you can...

I remember once upon a time I dealt with the same (and the same setup, 2 OB subs with a sealed sub, all Rythmik) but it was rectified after properly manipulating the phase (variable phase control, not just a 0/180 degree switch). Hopefully yours is as simple of a solution.

Best,
Anand.

HAL

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Re: using a sealed sub with OB subs
« Reply #5 on: 10 Oct 2018, 11:49 pm »
Ahhh...

If the sub is sitting next to your chair it is arriving before the main signal and maybe cancelling it out.  Had a similar situation helping with another sub setup.

As Anand said, your A370 phase control maybe able to correct for it.  In that case set the rear sub for 8' worth of delay, or 7mSec of delay.

mlundy57

Re: using a sealed sub with OB subs
« Reply #6 on: 11 Oct 2018, 12:19 am »
Ahhh...

If the sub is sitting next to your chair it is arriving before the main signal and maybe cancelling it out.  Had a similar situation helping with another sub setup.

As Anand said, your A370 phase control maybe able to correct for it.  In that case set the rear sub for 8' worth of delay, or 7mSec of delay.

Rich,

How does that correspond to the markings on the A370 phase control?

Mike,

Upload the measurements when you can...

I remember once upon a time I dealt with the same (and the same setup, 2 OB subs with a sealed sub, all Rythmik) but it was rectified after properly manipulating the phase (variable phase control, not just a 0/180 degree switch). Hopefully yours is as simple of a solution.

Best,
Anand.

Anand,

At this point I haven’t taken any recordable measurements. I’ve just been using a hand held SPL meter to get some idea.

Mike -- I hope you get this sorted out. I tried adding a third sub (actually my HT sub in the back of the room, just like your setup) and when it worked, it worked great!!!!  I kept running into various problems, much like you're experiencing. I realized, though, to really make it work well, I needed (ummm...wanted) a dedicated sealed servo sub with an A370 amp. This will be my next major upgrade. I want to try it again. With a 3rd sub, the dynamics are on another level.

Early B,

If this turns out to be something I want to keep I will need two subs as well. While technically I only need one because I would not be listening to music and watching a movie at the same time, the amp settings are going to be very different for the two applications.

My first concern would be where would I put a second sub in this room? Get rid of the chair and sit on the sub? And all for the two or three tracks that have sub 20Hz organ or synth notes?  Even then, those are more useful as demo tracks then something I actually listen to.  :dunno:

HAL

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Re: using a sealed sub with OB subs
« Reply #7 on: 11 Oct 2018, 12:34 am »
Mike,
Here is the Rythmik Audio page that discusses the adjustment of their phase control based on the crossover frequency you have set on the A370 amp.

http://www.rythmikaudio.com/phase3.html

You can use the 8' offset distance (7mSec) as what you want.

See if this helps.

I have time delay capability in my digital crossover, so use the distance converted to time for the correction. That is Td = D/(1130ft/sec) or 8/1130=7.0mSec delay


mlundy57

Re: using a sealed sub with OB subs
« Reply #8 on: 11 Oct 2018, 01:19 am »
Mike,
Here is the Rythmik Audio page that discusses the adjustment of their phase control based on the crossover frequency you have set on the A370 amp.

http://www.rythmikaudio.com/phase3.html

You can use the 8' offset distance (7mSec) as what you want.

See if this helps.

I have time delay capability in my digital crossover, so use the distance converted to time for the correction. That is Td = D/(1130ft/sec) or 8/1130=7.0mSec delay

Rich,

That method won't work in this case because I am not using the AVR for music listening. The only adjustment I can make is by physically turning the phase knob on the A370 amp. Is the goal to get the two phase curves to superimpose on top of each other?

HAL

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Re: using a sealed sub with OB subs
« Reply #9 on: 11 Oct 2018, 02:05 am »
Yes.

There are two things that are being adjusted.  One is the level control on the rear sub to be close in level to the front subs.  You can do that with a SPL meter and just measure one set of subs at a time.   A warble tone around the crossover frequency is a good thing to use.  This separates the volume setting part of the adjustment, since you are only adjusting front or rear at a time. You just need the average SPL's to be close with the meter. 

Next use the same warble tone track and slowly adjust the phase control to get the maximum output in the range of your crossover frequency with the same meter in your listening spot.   

It is tricky with the sub near you to adjust.