Sub Integration

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THROWBACK

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Sub Integration
« on: 20 Apr 2019, 11:07 pm »
I have a pair of OB LS-9s buttressed by a pair of Rhythmik OB subs (3 stack per side), driven by A370 PEQ servo amps. The problem is  that the amps have 17 different switch positions. Moreover, the effects are interactive. The versatility of this arrangement is both a boon and a curse.
Can someone point me to a step-by-step procedure along with an indication of how one is to know when the step is optimized? I will be using Stereophile Test CD-2 with 1/3 octave warble tones and a hand-held PAA3, hand held SPL meter (I could use either flat or C weighting).
E.G. (and I'm making this up)
1. set the 17 controls in the following positions to start (list)
2. attack phase first.
    a. with SW LOW PASS switch set to 80/24, send 80Hz signal to both main and sub.
    b. starting at zero, rotate DELAY/PHASE control until minimum indication on meter
3. etc.

As I said, I was making this up. But I have been fussing with this combo for a long time by meter and ear and, although my system sounds very good, I am still not sure I have it as right as my room will allow. 

Any ideas? (BTW, I sent essentially this same message to Rhythmik this afternoon)

mlundy57

Re: Sub Integration
« Reply #1 on: 21 Apr 2019, 01:32 am »
I was never able to get things really dialed in with an SPL meter. I could get close but that was it.

To get things dialed in better I got a mimiDSP U-Mik1 (~$80 at Parts Express) and downloaded the free REW software. This made dialing things in a lot easier and was the first time I was able to get phase set correctly. The graphs make the process more intelligible and systematic. You can see the effect your changes have. Something you can’t do with an SPL meter.

If you want to go this route, I’d be happy to describe the steps I follow.

Mike

THROWBACK

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Re: Sub Integration
« Reply #2 on: 21 Apr 2019, 03:31 am »
Good idea, Mike. In fact, I have the mic and have downloaded REW, but have never used it. I'd love to get your steps to proper phase. I have a hunch that that is the first thing you should set. I'm further guessing that you should measure the phase of your main speakers then match the subs to that.
Thanks,
Chuck

Early B.

Re: Sub Integration
« Reply #3 on: 21 Apr 2019, 04:07 am »
Every component change, cable swap, placement and toe-in experiment, tweak, or even seasonal variation often requires messing with those settings. The settings can change with each recording. And if you're really anal, the settings can be a bit different for each amp if you dial them in separately as you should. At some point, you gotta set it and forget it. Regardless, it will still be some of the best bass you've ever heard, so find some solace in that.

I've found that the most important setting is phase. I rarely fool with the others.

mlundy57

Re: Sub Integration
« Reply #4 on: 21 Apr 2019, 06:00 am »
Good idea, Mike. In fact, I have the mic and have downloaded REW, but have never used it. I'd love to get your steps to proper phase. I have a hunch that that is the first thing you should set. I'm further guessing that you should measure the phase of your main speakers then match the subs to that.
Thanks,
Chuck

Chuck,

I don’t set phase first. As Early B says, each speaker is done separately.

The first thing I do after determining a starting placement and toe in (by physical measurements for placement and toe in for center image) is find the crossover point. This is done one channel at a time. Turn the sub off and run a full range sweep of the LS9. You can run three or more and average them if you like. If there are any major dips you will need to move the LS9s or possibly add some diffraction. Once there are no major dips, look at the graph and find out where the LS9s are 6dB down.

Turn the amp to the LS9s off and turn the sub amp on. For the initial settings I use:
PEQ - off
Phase - 0
Crossover - pick a setting close to what you think it should be based on the previous step
Volume -12o’clock
Line in/ low pass - AVR/12
Rumble filter - Off
Extension Frequency - 20
Damping -High.                 These are just the starting points I use

Now run a sweep from 15Hz - 250Hz. If the base is significantly elevated or depressed compared to the LS9s, turn the volume up or down as needed then run another sweep. Once the average volume of the sub is close to the LS9s, determine where the sub is -6dB on the high end. You want the sub to be -6 at the same point the LS9s are -6. Adjust the crossover control in the direction you need to go and run another sweep. Continue making adjustments and running sweeps until the sub is -6 at the same frequency the LS9s are -6.

Now compare the average output of the sub with the average of the LS9s again. If the averages are not the same, adjust the sub’s volume control again until the averages are the same. Now repeat the crossover adjustment until the sub’s -6 point is the same as the LS9. Then Check the average volumes again. Keep going back and forth until both the sub and LS9 have the same average volume and -6 point. These adjustments are all with the sub. The LS9 has not been turned back on.

Next look at the sub’s graph and see if there are any peaks or valleys. If there are any valleys deal with these first as the only way to deal with them is to physically move the sub. If you have to move the sub to fix a valley, go back and recheck the average level and crossover point as necessary. If there is a peak, turn on the PEQ and start adjusting the frequency, width, and gain until you have tamed the peak.

Now turn the LS9 back on and run a full range sweep with both it and the sub playing. If the crossover point is smooth, you’re done with this speaker. If it is not smooth, start adjusting the phase on the sub until it is.

Now do all that again with the other channel. The settings on the two sub amps will likely be close but not the same.

This will get them dialed in relatively flat.

Then I turn both channels on and run a full range sweep to see what they look like together. The shape of the two channel graph is usually very close to the individual channel graphs, just 4-6dB higher.

Now listen to music for awhile then experiment with the 50/24 and 80/24 slope positions and the damping positions to determine which you like best. You can also experiment with the extension settings.

I hope all this makes sense.

Mike


THROWBACK

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Re: Sub Integration
« Reply #5 on: 21 Apr 2019, 12:40 pm »
Wow, Mike! Did you get any sleep last night or did you stay up all night writing your wonderfully detailed response? Thank you.
It's a lot to digest, but over the next week or so, I will follow your procedure exactly. I noticed something, though. EARLY B (thanks!) says that phase is the most important parameter; you, however, never even mention it except to say that you don't look at phase first.

Now it may be speaker dependent. The LS-9s consist of twelve 6-inch mids/woofers in a stack 80” tall. Thus, each element is at a different distance from the observer’s position. I haven’t done the math, but it seems to me, therefore, that phase between the tall array and the short, floor-standing sub can be set only approximately.
 
Still, my intuition tells me that should be done first.

Now if I can only find a local, REW-savvy, bribeable (lunch and/or a glass or two of good wine), patient, audio nut to help me . . .




poseidonsvoice

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Re: Sub Integration
« Reply #6 on: 21 Apr 2019, 01:04 pm »
Chuck,

REW is a very powerful and free tool so it in and of itself requires some study. There is a learning curve with it. And it does a whole lot more than room based measurements. Having an REW savvy individual will be a good thing, along with 1 or 2 others to help with moving speakers and subs. None of yours are light. Hopefully your room allows for different sub locations, that’s one of the biggest impediments I have seen with 2ch enthusiasts.

Best,
Anand.

mlundy57

Re: Sub Integration
« Reply #7 on: 21 Apr 2019, 01:07 pm »
Chuck,

I do mention phase. It comes into play when you turn the LS9s back on. For example, in my room after I determined the -6 point for the NX-Otica and finished adjusting the sub to match there was an issue. You would expect the two speakers to reinforce each other at the -6 crossover point and boost that point up to flat. However, when I played the Otica and sub together, there was a dip at the crossover point. They were no longer crossing at the frequency where the Oticas were -6 but where they were -10. They were partially cancelling each other out at the crossover frequency.

This meant the sub and Ottica were out of phase with each other. That’s when I adjusted the phase control until the dip at the crossover point was gone. Now the sub and Otica were in phase with each other.

As Anand says, REW is powerful. I’m the first to admit I’m no expert with REW. What I’ve described is about all I know how to do with it at this point.

Mike

poseidonsvoice

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Re: Sub Integration
« Reply #8 on: 21 Apr 2019, 01:22 pm »
Chuck,

Here are 2 threads, one from Mike (mlundy57) and the other from Ed (ebag4), where they go through what they did for sub integration:

https://www.audiocircle.com/index.php?topic=159295.msg1701189#msg1701189

https://www.audiocircle.com/index.php?topic=159409.msg1702157#msg1702157

Best,
Anand.

THROWBACK

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Re: Sub Integration
« Reply #9 on: 21 Apr 2019, 02:15 pm »
Anand (PM) asked me to post my results so far. I related to him an old Chinese proverb: "Man with one watch knows what time it is; man with two watches never sure." 

I have a PDF of my results so far using "two watches."  They are certainly different, but roughly comparable. Neither is terrible, but I can't figure out a way to post it here. One was taken using warble tones from Stereophile Test CD 2 as measured by my hand-held SPL meter (PAA3 Personal Audio Analyzer). The other made a couple of weeks ago by an audio buddy using pink noise and his HP Audio Analyzer.

But - - being a hobbyist and all - - I would like to see what could be done using REW, with which I have no experience. I'm looking for a local REW-savvy, bribeable (lunch and/or a glass or two of good wine, or . . . ), patient, audio nut to help me.


HAL

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Re: Sub Integration
« Reply #10 on: 21 Apr 2019, 02:37 pm »
Chuck,
You can take a screen capture of the PDF and save it as a JPG in Paint or other picture editor.  It copies it to the clipboard on a Windows machine. 

Here is an example with Paint.





THROWBACK

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Re: Sub Integration
« Reply #11 on: 21 Apr 2019, 03:16 pm »
Previous "two watches" results of integration effort.



If this works, thank (blame?) Mike Lundy.

Chuck

THROWBACK

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Re: Sub Integration
« Reply #12 on: 21 Apr 2019, 03:22 pm »
It DID work! But blame HAL (sorry, Rich), not Mike.

HAL

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Re: Sub Integration
« Reply #13 on: 21 Apr 2019, 04:22 pm »
Chuck,
Glad it worked.

Here is what REW will do for measurements.  This can be done repetitively so you can see changes in response as you dial in the system.

This is just a measurement I did while learning the adjustments on the HX800-12OB servo amps at about 1 meter.  Similar to the A370PEQ.   This is just seeing what happens in the room with just the sub first.

There is a preferences tab where you setup your sound card and calibration data file for the mic system.  It also lets you check the system with a level test to start out.


 

mlundy57

Re: Sub Integration
« Reply #14 on: 21 Apr 2019, 04:57 pm »
Previous "two watches" results of integration effort.



If this works, thank (blame?) Mike Lundy.

Chuck

This graph has me confused. It seems to be saying an ideal room response is 8dB less at 12kHz than at 25Hz. Extending the graph out it would be even farther down at 20k.

Am I misinterpreting the graph or am I missing something else?

Mike

poseidonsvoice

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Re: Sub Integration
« Reply #15 on: 21 Apr 2019, 05:09 pm »
Mike,

Look online and read about “Target Curves” from Toole et al. Several other acousticians, Geddes, etc..have commented on the same.

Best,
Anand.

poseidonsvoice

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Re: Sub Integration
« Reply #16 on: 24 Apr 2019, 06:35 pm »

THROWBACK

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Re: Sub Integration
« Reply #17 on: 24 Apr 2019, 09:33 pm »
Good job, Anand. Great discussion of "house curve."

FY (and others')I, I had a golden-eared buddy over a couple of days ago to help fine tune my system. We listened to a bunch of music - - vinyl & SACD; classical and jazz. We found that the sound was so source-dependent, we ended up not changing a darned thing.

I'd still like to do an REW analysis though . . .

mlundy57

Re: Sub Integration
« Reply #18 on: 24 Apr 2019, 10:56 pm »
I haven’t digested the info on house curves yet, I’t’s all I can do to get ready for LSAF and my day job right now. I’ll spend more time reading up on this once things calm back down. 

What I’ve read so far looks interesting but I’m not sure how to accomplish any of them. I can boost the bass easy enough but since top end is passive it seems like it is what it is.

Mike

poseidonsvoice

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Re: Sub Integration
« Reply #19 on: 25 Apr 2019, 12:03 pm »
Here is more:

http://www.aes.org/e-lib/browse.cfm?elib=17839

Of course if you already own Toole’s “Sound Reproduction...” book, the 3rd edition, you know all this stuff.

Strongly recommended.

Best,
Anand.