Originally Posted by pdxrealtor
In this section I will post REW graphs and tuning info.
I have two dual opposed, one in each corner of the front of my theater.
Then about 5ft behind the row of theater chairs I have two single driver cabinets.
All are powered by a Peavy IPR2 7500 and in line is a mini-dsp, balanced version, set to 0.9 input volts.
I set the gain structure today using this guide - I'll admit I didn't read a lot of it, but read a decent amount. Add in the mini dsp input sensitivity option and it can become a time consuming task for someone who doesn't do this all the time.
Also took a piece from Ricci from this post. --- The part about using 80% of max AVR volume if the only tool you are using is a volt meter. Basically you can assume that @ 80% max volume you are close to the point of clipping the AVR under the gain structure setting steps.
Here is the best info I found on the mini-dsp input setting-
I tried both input settings, 2.0 volts and .9 volts. I went with the .9 volts
as it was a much better match. The point of clipping is -6db on the input side.
Here's some REW graphs. NOTE: I trip my dedicated 20 amp breaker before I begin to show signs of any compression. The subs have more, they just need more juice. At least for sine waves.
I didn't have time to play with any movies and the music I played with yesterday tripped the breaker, but that was before the gain setup..... not sure if that's going to matter.
Also, check out page seven for detailed data I acquired during the gain structure process.
My room gives no love, but the good part is I basically know where to put what.
I believe the problem is the wall directly behind the LP. Move the mic over to the more open L part of the room and things get better. It is what it is. At least with these subs I know
the DBs are there, I just need to dial them in. This graph is after I did all the gain structuring and level calibrating with the .9 input setting on the mini. It was one of the last measurements for the night. I will pick up from here when I start back up. I ran out of electricity before the subs ran out of juice.
Here is an average of all my LPs. The mic was placed on each side of each chair at ear level. The test was done at a calibrated 80 db.Here's one of the earlier graphs for the day. I ran it until the breaker tripped too. I'm not sure why the peak was more DB here vs. the first graph. The only thing I played around with was the time delay and volume settings in the mini dsp. I believe this was at a 3.5 ms setting on the two rear single cab subs and 0 on the front subs.
I know it looks like a couple of tests show compressing, but for some reason I only increased 4db at a time. I can't remember why, but there was a reason. I tripped the breaker on the next test, but didn't keep the measurement.
Ya...... still got that lovely null ~50 hz.
You can see the line on the last graph above. I started the tests at 80 db and moved up from there. So that shows you the peaks and dips I'm dealing with.
I'm off to Hawaii for a week on Thursday so this is it for a while.
New graphs are up. If they don't show up here they are on page one.
I did some reading on gain structure and did the process, twice. Here's some numbers I got in case someone down the road stumbles on this thread and finds it useful. Pioneer AVR SC 1522, same as the SC 68 (I think) show the following volts at LFE RCA out using a 60 hz sine wave @ -3dbs in REW:
- 30 = 0.2 volts at LFE output
0 = 8.7
+10 = 10.8
+12 (max) = 11
To gain match I turned the AVR sub trim to max and AVR volume to 80%, which is -6 on my AVR. Since I didn't have a way to tell when I was actually clipping the AVR signal I used Ricci's suggestion of 80% max volume.
I used a 60 HZ pink wave tone at -3dbs (with subs unplugged from amp) and turned up the amp gains until the clip light came on. With the mini dsp at the 2.0 input volt setting the amp gain knob was at -3 + 1 dot. With the mini dsp input setting at .9 volts that dropped the amp gain knobs down to an even -3.
However, with the mini dsp input voltage at .9 I get max voltage before I get to max output on my AVR. With the mini dsp set to an input voltage of 2.0 I could not get max input with max AVR settings. Make sense? If not read the links I posted on page one post 3.
After setting the gain structure the front woofers are ~ 8 DB louder than the rears. With both on the DB was above 75. With the mini dsp input voltage at 2.0 volts I had enough room to dial back the output using the AVR sub trim, to a combined 75 DB....even though the front was still ~ 8DB louder than the rears.
With the mini dsp input voltage at .9 the spread between the front sub channel and the rear sub channel stayed the same at ~ 8db. But when combined I did not have enough room to dial back the DB to 75 using the AVR sub trim so I used the mini-dsp output on the front channel and took a couple DBs out that way.
As it stands I'm at -12 (max reduction) on my AVR sub trim and a tick of reduction on the mini output to get the 75 DB level calibration needed.
With this setup I hit -6.2 (just before clipping) on the mini dsp input at a sub trim of -3 and an AVR volume of 0 (reference). That is 9 DB hot on the sub level, and reference on the mains/surrounds. Bump the sub trim up to a stupid +3 (that's 14 db hot!) and AVR still at reference (0) I get a -1.2 input reading on the mini dsp. Clipping happens at -6.
With the 2.0 volt input setting on the mini I got exactly 0.1 on a 60 hz sine wave with max sub trim @ 80% AVR volume (-6). That's max settings. Not getting even close to full input/output and it gets worse as you decrease sub trim and AVR volume.
.9 volts is the obvious winner.
As always I'm open to feedback.
The next thing I will read up on is how to boost the low end on a DIY sealed sub setup. If anyone has some pointers I'm all ears! I think that's the next step before Eqing some of these peaks down. But if I'm wrong let me know.
Been a looonnnngg day. Too bad I won't remember any of this in 3 months.