OK. Lets see if I did this right (proper setup of 5.2 system) - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 5 Old 11-05-2012, 05:19 PM - Thread Starter
Senior Member
 
blackangst's Avatar
 
Join Date: Jan 2010
Posts: 318
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 19
So, Ive got a 5.2 setup that consists of Polk RTi10 front l/r, Polk CS10 center, Polk FXi A6 for side surrounds, 2 Hsu 12" subs (VTF3 Mk2 and VTF2 Mk3).

First, run full auto MCACC on all 7 speakers, adjusting sub gains until MCACC marks subwoofer output at 0. Receiver inevitably sets fronts to large.
Manually change fronts to small, set MCACC to keep speaker settings, and run MCACC again.
Turn subs off.
Using a Radio Shack SPL meter from the main listening position, adjust volume using test tones, each speaker one at a time, until each reads 80db. (This results in about a +4-+6 reading in MCACC readings)
Gain match the subs (put each sub, one at a time, in the center of the room, put SPL meter on a stool 12" away from it, play test tone, and adjust gain until meter reads 85db(I like my subs a bit hot)).
Done.

Did I do this right? I cant Im disappointed in the sound at all. But, you dont know what you dont know, right? Im just wondering if there are glaring issues in the way I set this up?

Thanks everyone smile.gif

Below is a pic from the back of my listening area so you can get an idea of the room.

20120822_130047.jpg
blackangst is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 11-07-2012, 01:48 PM
AVS Special Member
 
fbov's Avatar
 
Join Date: Nov 2006
Location: Bushnell's Basin, NY
Posts: 1,014
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 28
The only thing I'd do differently is leave the subs in place when gain matching them, and measure from the listening position, so you include any room loading effects in the adjustment. I'd also be careful what sort of signal I used, as sine waves will excite room modes, and you don't want to set anything based on levels augmented by wave interference.

I would also download REW and get a patch cable to plug the RS meter into a PC. Then you can measure bass response curves directly, making issues a lot easier to quantify and address. HELP is at the top of the download page. There are some issues with the RS meter, but it's fine below 200Hz, where you'll be working, but lots of unit-unit variability at high frequencies.

Finally, you may find some bass response anomalies that won't yield to the available adjustments, indicating that the subs need to move to resolve the issue.

Nice room by the way...

HAve fun,
Frank
fbov is offline  
post #3 of 5 Old 11-09-2012, 09:17 AM - Thread Starter
Senior Member
 
blackangst's Avatar
 
Join Date: Jan 2010
Posts: 318
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 19
Quote:
Originally Posted by fbov View Post

The only thing I'd do differently is leave the subs in place when gain matching them, and measure from the listening position, so you include any room loading effects in the adjustment. I'd also be careful what sort of signal I used, as sine waves will excite room modes, and you don't want to set anything based on levels augmented by wave interference.
I would also download REW and get a patch cable to plug the RS meter into a PC. Then you can measure bass response curves directly, making issues a lot easier to quantify and address. HELP is at the top of the download page. There are some issues with the RS meter, but it's fine below 200Hz, where you'll be working, but lots of unit-unit variability at high frequencies.
Finally, you may find some bass response anomalies that won't yield to the available adjustments, indicating that the subs need to move to resolve the issue.
Nice room by the way...
HAve fun,
Frank

Hi Frank thanks for the response.

What youre suggesting is level matching, not gain matching. Everything I have read says that is NOT a good way to tune subs. Reason being, lets say I level match them. It may turn out one sub will end up with a higher gain setting than the other, which could result in bottoming out first during peaks. Everything Ive read says says since <80htz is non directional (for the most part) they need to be set exactly the same gain so they share the load equally.

Thoughts?
blackangst is offline  
post #4 of 5 Old 11-15-2012, 11:13 AM
AVS Special Member
 
fbov's Avatar
 
Join Date: Nov 2006
Location: Bushnell's Basin, NY
Posts: 1,014
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 28
I see what you're getting at... Your procedure will insure that each sub outputs the same SPL level for the same input signal voltage, correct?

However, that doesn't guarantee that they'll both clip at the same input voltge, which is what I understand as the goal of gain structure optimization. We're both using consumer-level gear, and gain matching is far more important when mixing pro and consumer gear as the pro gear has lower input sensitivity, resulting in an inability to deliver full output. (I can't think of the products used to address this....)

The issue with your approach, from a gain structure perspective, is that the VTF2 has less power than the VTF3 and so should clip first when you're done. Now 250W vs 350W isnt' a big difference, 1.5dB, compared with 8.5dB difference between my Onkyo AVR (0.2V input sensitivity) and, say, the Crown XTi series at 1.4V input required to achieve rated power. The pro vs. consumer gain difference is a factor of 7x, while your subs' difference is a factor of 1.4. Very different, I hope you'll agree, and very necessary if running your subs with pro amps, as many folks who post here do.

What I would suggest is doing some frequency sweeps with REW and your rmeter, to see where the peaks and valleys are in the frequency domain, them move the mic and see how much this pattern changes. Swings can be very large over short distances. Address this and you'll have made a real improvement in sound quality, but that's another thread...

HAve fun,
Frank
fbov is offline  
post #5 of 5 Old 11-15-2012, 11:27 AM
AVS Special Member
 
fbov's Avatar
 
Join Date: Nov 2006
Location: Bushnell's Basin, NY
Posts: 1,014
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 28
fbov is offline  
Reply Audio theory, Setup and Chat

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off