Onkyo 818 - calibrate for dual subwoofers? - AVS Forum
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post #1 of 8 Old 02-02-2013, 03:56 PM - Thread Starter
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Anyone have any insight on calibrating the Audessy Multi XT with dual subwoofers for the TX-NR818?

I have a couple of the Emotiva 12's that I wanted to dial in.

Has anyone done this with any success?
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post #2 of 8 Old 02-02-2013, 09:42 PM
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You can do it level matched or gain matched but either way the avr is going to treat them as one. Look in here http://www.avsforum.com/t/1412714/onkyo-tx-nr818-official-owners-thread-discussion

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post #3 of 8 Old 02-02-2013, 10:30 PM - Thread Starter
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I was planning on setting the gain on the one in the corner about 25% less than the one in the middle of the room, maybe decreased more if needed.

Always get the corner accentuation effect.

The calibration mic should pick that up.

Just curious what others have done.
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post #4 of 8 Old 02-03-2013, 06:47 AM
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You have Audyssey XT32, top of the line. But no SubEQHT. That;s OK though you can still get two subs playing nicely. Do you have any measurement gear? Do you have an SPL meter, or a mic with REW? The new USB mics are a very inexpensive measurement set up that can really help get your system to higher performance levels.

Recently I posted the following which should be of some help. All stuff I learned here from the helpful folks around.

Gain matching makes more sense to me than level matching although at first I didn't really get the advantages. After I let it synch in a bit it just makes a ton of sense over level matching IMO. Another good thread on it here http://www.avsforum.com/t/1282064/two-subs-gain-matching-vs-level-matching Post #5 is the process but lots of good discussion there.

On the phase controls I think it is good to let Audyssey come up with the distance for the further sub which may actually be different than the physical distance and that is OK. From there I agree you want to time align the closer subs to the further one looking for optimal results. Optimal results means flattest frequency response but a users ability to determine that is really dependent on the tools they have available. Do you have SubEQHT, Minidsp or similar, SPL meter, Calibrated mic and software (REW omnimic, etc)? Are you OC? Do you enjoy tweaking and measuring?

I've commonly seen the following technique recommended, have done this myself, and it sounded pretty good. Play I sine wave at the crossover frequency (commonly 80 Hz) and tweak the distance/phase/delay settings to reach the highest SPL. You can even improve on Audyssey's results so run Audyssey for the furthest, tweak that sub as described, then add the next closet sub and tweak it's phase (or delay if you have minidsp or similar) for highest SPL, continue for additional subs.

Markus767 points out that with as much room interaction which occurs at these lower frequencies you really want to optimize the entire crossover region not just that single freq (the crossovers not a cliff like drop off but a roll off). Do some trial and error and make frequency response graphs (REW, omnimic, etc). Examine the 10, 20, or 30 Hz surrounding your crossover frequency and choose the setting combination that produces the best results. I'm very interested to find out if this is commonly producing different (which should be better) results than the sine wave at crossover frequency approach. I am going to play around with this approach and try comparing it to the sine wave approach.

Now If you don't have any tools you can do the sine wave at crossover freq thing with a SPL smartphone app. Don't trust the actual SPL values, just shoot for the higher ones. Clearly this approach is not for the OC's. Also make sure you do a sanity test playing a sine wave raising and lower the main volume to make sure the values are really moving around properly.
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post #5 of 8 Old 02-03-2013, 07:56 AM - Thread Starter
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Quote:
Originally Posted by dstew100 View Post

You have Audyssey XT32, top of the line. But no SubEQHT. That;s OK though you can still get two subs playing nicely. Do you have any measurement gear? Do you have an SPL meter, or a mic with REW? The new USB mics are a very inexpensive measurement set up that can really help get your system to higher performance levels.

Recently I posted the following which should be of some help. All stuff I learned here from the helpful folks around.

Gain matching makes more sense to me than level matching although at first I didn't really get the advantages. After I let it synch in a bit it just makes a ton of sense over level matching IMO. Another good thread on it here http://www.avsforum.com/t/1282064/two-subs-gain-matching-vs-level-matching Post #5 is the process but lots of good discussion there.

On the phase controls I think it is good to let Audyssey come up with the distance for the further sub which may actually be different than the physical distance and that is OK. From there I agree you want to time align the closer subs to the further one looking for optimal results. Optimal results means flattest frequency response but a users ability to determine that is really dependent on the tools they have available. Do you have SubEQHT, Minidsp or similar, SPL meter, Calibrated mic and software (REW omnimic, etc)? Are you OC? Do you enjoy tweaking and measuring?

I've commonly seen the following technique recommended, have done this myself, and it sounded pretty good. Play I sine wave at the crossover frequency (commonly 80 Hz) and tweak the distance/phase/delay settings to reach the highest SPL. You can even improve on Audyssey's results so run Audyssey for the furthest, tweak that sub as described, then add the next closet sub and tweak it's phase (or delay if you have minidsp or similar) for highest SPL, continue for additional subs.

Markus767 points out that with as much room interaction which occurs at these lower frequencies you really want to optimize the entire crossover region not just that single freq (the crossovers not a cliff like drop off but a roll off). Do some trial and error and make frequency response graphs (REW, omnimic, etc). Examine the 10, 20, or 30 Hz surrounding your crossover frequency and choose the setting combination that produces the best results. I'm very interested to find out if this is commonly producing different (which should be better) results than the sine wave at crossover frequency approach. I am going to play around with this approach and try comparing it to the sine wave approach.

Now If you don't have any tools you can do the sine wave at crossover freq thing with a SPL smartphone app. Don't trust the actual SPL values, just shoot for the higher ones. Clearly this approach is not for the OC's. Also make sure you do a sanity test playing a sine wave raising and lower the main volume to make sure the values are really moving around properly.

I don't have an spl meter but if the mic with REW can produce the freq response graphs, I'm all in. Any mic's you'd recommend?

I do have some previous car audio experience tweaking subs, setting proper frequency roll off, setting gains and time alignment all by ear. But very little in the home theater area.

I was hoping to hear about audio calibration CD's. A decent set of audio tools that I could fine tune using a consistent baseline. Couple that with some audio software and I could start getting measurable results.

I'm somewhat OC and I do like to measure stuff. My geek-ness often comes out to play.

I know I have a powerhouse with the 818 and really look forward to uncovering and maximizing it's potential.

I'll definitely check out the threads mentioned above.
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post #6 of 8 Old 02-03-2013, 09:54 AM
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Quote:
Originally Posted by shortnugly View Post


I don't have an spl meter but if the mic with REW can produce the freq response graphs, I'm all in. Any mic's you'd recommend?
[SNIP]
I was hoping to hear about audio calibration CD's. A decent set of audio tools that I could fine tune using a consistent baseline. Couple that with some audio software and I could start getting measurable results.

I'm somewhat OC and I do like to measure stuff. My geek-ness often comes out to play.

I'm a software engineer and love doing this stuff. You're going to love REW, then hate it, then fall head over heals. It takes some patience but is a very powerful tool. It does include a signal generator (FR sweeps from any freq to any freq, sine waves at any freq, etc...) So you probably do not need a calibration disk too.

Minidsp makes a USB mic as well but I think I'm going to pick up this one
http://www.parts-express.com/pe/showdetl.cfm?partnumber=390-808
Right now I measure with a radio shack SPL meter. The minidsp mic is slightly easier to get talking to REW, but the Dayton has individual calibrations at different angles. The minidsp is supposed to be pointed at the speakers from main listening position, how do you point it at multiple speakers??? Doesn't make since to me so I'm going with the Dayton which you point at the ceiling from MLP so it reads from all speakers equally like every other mic positioning recommendation I have ever heard of. Before the USB mics the good measurement mics usually needed a pre amp and an outboard sound card so a quality measurement set up just got cheaper and much less complex. Compare $100 to the price of your system, it is money very well spent and will likely provide much more actual improvement then most gear upgrades that cost much more.

Here is where you get REW and great feedback. The tools author John hangs out there and is very knowledgeable and helpful. The tool is free but I recommend a paypal donation. As a programmer I can tell it this was no small amount of time and expertise to write.
http://www.hometheatershack.com/forums/rew-forum/#axzz2JrGaXHgg

Traditionally REW AVS'rs just do their REW stuff over there at HTS but we now have a thread started up with some pretty helpful folks and guides as well.
http://www.avsforum.com/t/1449924/simplified-rew-setup-and-use-usb-mic-hdmi-connection-including-measurement-techniques-and-how-to-interpret-graphs/900

Good luck and look forward to hearing progress, path, impressions etc...
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post #7 of 8 Old 02-03-2013, 10:59 AM - Thread Starter
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Awesome, thanks for the tips and the links.

It'll take me some time to put some things together. I'm anticipating ear-tweaking everything, then running the Audessy calibration, then running REW to see how far off I was.

I'm still going to hunt up a reference CD with test tones for my control.

I almost bought the Radio Shack spl meter and still might. Often think about measuring the SPL on my new Scion TC during my daily commute. That'll give me something to tweak.

Thanks again for your help.

I'll share my findings with the group.
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post #8 of 8 Old 02-03-2013, 06:13 PM
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