Home Theater Forum and Systems banner

1 - 8 of 8 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter #1 (Edited)
Hey guys,

I've just purchased my first sub (well not exactly first, but I haven't had one in more than 10 years), and I'm in the process of integrating it into my 2 channel system (which also serves as HT system). I'm hoping that you can help me get things properly set up.

My system consists of the following:
Denon 3312ci AVR
Oppo BDP-93
Salk SongTower (L,R,C)
Salk Custom Sub (LMS Ultra 5400, sealed, 3.3 cu ft)
SpeakerPower SP1-2400 Amp (for the sub, running on its own 20amp circuit)

Gain Structure and Clipping:

First, I want to be sure that I set the gain correctly on the amp. I read through Wayne's comprehensive discussion of gain structure as a guide. I measured the sub pre-out on my AVR with a volt meter and found that it produces 6.8 volts (with volume at max and speaker-level for the sub at max). I didn't have a way to identify where this signal begins to clip, so I took Wayne's advice and subtracted 30% from the max voltage to obtain an estimate of clean signal output--this came to 4.76 volts. I then adjusted the volume on the AVR down until the sub pre-out produced 4.76 volts. Then I connected the sub amp (but disconnected the subwoofer) and played the 60Hz signal provided by Wayne. While playing this signal, I then proceeded adjust the gain on the amp until the clip light started to blink. Wayne said to adjust the gain until the clip light becomes solid, but I only had enough gain to adjust it until the light was blinking fairly rapidly. So my question is, have I done this properly? As set, it appears that the amp can take all 4.76 volts from the AVR as it starts to clip.

After setting the gain as described above, I adjusted the speaker-level for the sub pre-out back down to 0db (since it was maxed out at 12db for the gain structure process). Then I further adjusted the speaker-level for the sub down after measuring with REW since it seemed too high (now it is set at -3db). Set here, the sub pre-out now produces 4.76 volts when the AVR volume is set to +10db. So, supposedly this is where the pre-amp signal clips and also where the amp clips.

Should I assume that the signal driving the internal amps in the AVR (for the fronts and center) also clip here? I seem to get distortion in the fronts before reaching this point (+10db on the AVR) and I wonder if this is due to the AVR amp clipping or the speakers not being able to handle the power? Or maybe the amp itself does't produce clean power at this level?

Am I on the right track with all of this?

Noise (Buzz and Hum):

When I initially connected the sub, it exhibited a very disturbing hum. I assumed it was a ground loop problem and quickly discovered that it was largely from the cable box connected to the AVR. I checked the cable outside and found that the cable company literally installed a faux ground cable. It literally ran from the grounding block attached to the coax down a plastic conduit (for the incoming phone line) nearby and attached to....NOTHING. So I ran a new ground to the main electrical ground stake. That eliminated the loud hum, but it did not eliminate the noise entirely. As long as a signal cable is connected to the amp and the AVR is on, there is a hum that is fairly audible (definitely not acceptable). Should I be looking at installing an isolator or some other device? Jensen seems to make a few different products for dealing with this issue, but I'm fairly lost as to what the best approach is. Also, whatever I do will need to be compatible with the addition of future EQ (maybe miniDSP) for the sub.

Crossover:

I set my crossover to 80Hz thinking and it seemed to work OK, but I think I get better results via REW measurements when using 60Hz. I'm new to REW, but this is what I measured (via REW, Tascam 144, Cross Spectrum Labs calibrated mic):

Green Line is Crossed at 80Hz and the Brown/tan line is crossed at 60Hz (1/12 smoothing)


There is no EQ applied yet (that's a bridge I'll cross later), so the sub (being sealed) should roll off at about 30Hz. Given that, do my readings seem high between 10 and 30Hz? Could that be room gain, or am I making a mistake with REW? Which crossover point would you recommend considering that EQ will be added later?

If you've made it this far, sorry for the very long post! But I am very curious to hear some good feedback.
 

·
Registered
Joined
·
19 Posts
Discussion Starter #2 (Edited)
I just realized that I didn't have enough posts to link pictures, so the graph didn't show. I'll try to get it posted later if I can.

OK, here it is. And one more time...Green Line is Crossed at 80Hz and the Brown/tan line is crossed at 60Hz (1/12 smoothing). I'll get my future graphs in line with recommendations for posting REW graphs (I read that post a little late, so there is smoothing in this one).
 

·
Registered
Joined
·
19 Posts
Discussion Starter #3
Bueller...Bueller....

Seriously, I apologize for the lengthy post and boring topic (?), but can anyone help me out. I've posted this over at another popular forum, but I haven't quite resolved the gain structure issues.

Maybe I can buy Wayne a steak dinner for some advice...I just realized that he lives fairly close by.
 

·
Registered
Joined
·
213 Posts
Hi there. Your Denon has distance settings that you can adjust. It appears that in both cases, your response takes a deep null dive at the crossover point. You may be able to remedy this through the distance setting for the sub and/or placement experimentation. I would also suggest going ahead and running Audyssey which should help automatically take care of some of the issues.
 

·
Registered
Joined
·
248 Posts
Wich version of Audyssey has your receiver.
Or have you manual set the distance of the speaker,s and sub.?
 

·
Registered
Joined
·
19 Posts
Discussion Starter #6
Thanks for the replies.

My AVR has MultiEQ XT (not the fancier XT32 version). I haven't run it yet since I was planning to use manual EQ to flatten the curve for the sub at a later point.

I set the speaker distances manually by carefully measuring. Are you guys suggesting that I should mess around with changing the distance specified in the AVR for the sub? Unfortunately, I don't have a dedicated listening room (actually I'm lucky to even have this sub at all!), so I can't move the sub, itself, around to find the best location for performance (a shame, but a reality of my situation).
 

·
Registered
Joined
·
248 Posts
No i dont think so,if you did it by hand is usualy give,s a good result.
I have an older version of ADSY to,and do the distance manual by carefully measuring,just like you.

After that whit REW and my ears afther REW for finetuning.
Not every room is the same,so i alway,s listen a lot between setting de eq of ADSY manual.

Mine doesn,t even has a sub EQ,i have the cheap ADSY.
Butt ok for de 5 speakers,and my 2 sub,s are powered by a Inuke DSP so that is external.

If the sub can only stand at that place,we start work whir that,no problem.
Some of my friend,s have te same problem,we alway,s try to make te best of it.

One case was a downfire SDX15.........terrible response.
After 5 years finaly he got it made,he could putt in where he wanted,and it became a front fire.
Very big upgrade


Are you missing on the low freq,i would like to see an 60 hz cross whit no smooting.
Is that possible?

See or you have a problem.
PS Whit the distance you can set the phase in vere little step,s ,you are setting the timing what is basicly fase.
Try the best result whit the fase from the sub ,whit distance of the AVR you can make littke adjustment in the timing/fase.

Learned on this forum,in the REW section:
Try phase at 0 and 180 degrees to see which gives the smoothest response through the crossover region, then fine tune by varying the distance setting.
 

·
Registered
Joined
·
19 Posts
Discussion Starter #8
No i dont think so,if you did it by hand is usualy give,s a good result.
I have an older version of ADSY to,and do the distance manual by carefully measuring,just like you.

After that whit REW and my ears afther REW for finetuning.
Not every room is the same,so i alway,s listen a lot between setting de eq of ADSY manual.

Mine doesn,t even has a sub EQ,i have the cheap ADSY.
Butt ok for de 5 speakers,and my 2 sub,s are powered by a Inuke DSP so that is external.

If the sub can only stand at that place,we start work whir that,no problem.
Some of my friend,s have te same problem,we alway,s try to make te best of it.

One case was a downfire SDX15.........terrible response.
After 5 years finaly he got it made,he could putt in where he wanted,and it became a front fire.
Very big upgrade


Are you missing on the low freq,i would like to see an 60 hz cross whit no smooting.
Is that possible?

See or you have a problem.
PS Whit the distance you can set the phase in vere little step,s ,you are setting the timing what is basicly fase.
Try the best result whit the fase from the sub ,whit distance of the AVR you can make littke adjustment in the timing/fase.

Learned on this forum,in the REW section:
Try phase at 0 and 180 degrees to see which gives the smoothest response through the crossover region, then fine tune by varying the distance setting.
Excellent. Now I understand how to fine tune phase. I was wondering how to get beyond either 0 or 180 via the polarity switch.

I'll post the correct graph with no smoothing shortly.
 
1 - 8 of 8 Posts
Top