Dual Subs & Soundstage

[Muzykant]

Hello All,

I recently added a second subwoofer to my system and experienced drastically deteriorated soundstage. All sounds seem out of focus (sounds like the fake surround effect on old TVs) and trebles seem muffled. In short, system lost all its clarity.

The main speakers and subwoofers have symmetrical placement along the wall, and are equal distance from the seating position. They are facing forward, as tilting them towards the couch seems to worsen the soundstage further. Subwoofers are located between the TV and the mains, not too far from either. The gain is set not too high, so that the excursion never exceeds half an inch during the peaks.

I tried moving the subs to the corners and other available locations, but nothing seems to help. Turning either one of them off improves things immediately. With the speakers off, the bass lines from the subs seem clear and powerful.

What could be the problem?

 

[crossedover]

Equipment list?

 

[ski2xblack]

Hard to say what the problem is with so little to go on, but that weird unfocused effect you describe sounds like a phase issue.

 

[ImcLoud]

sounds like a phase issue.

What are your settings/ Room correction? Are you using LFE? What are the subs set too?
I have never heard subs make mains sound bad unless they are crossed too high or your mains are not crossed too low...

 

[Muzykant]

Speakers: Definitive Technology SM 65 (5)
Subwoofers: SVS SB13 Ultras (2)
Processor/Preamp: Emotiva UMC-200
Amplifier: Emotiva XPA-5
TV: 64" Samsung Plasma F8500

 

[Muzykant]

I have not applied any room correction (had bad results years ago, never used it since). I am using LFE. Subs have no adjustments on their amps (full range), but the processor has them and the speakers crossed over at 50 Hz with a 24 db/octave slope.

It feels like a phase issue to me as well so far...

 

[ImcLoud]

I would try the room setup, the umc200 should handle it, but first go through your subs controls and make sure they are set correctly... Shut one off and go through the phase adjustments...

 

[MidnightSensi2]

And if you lower the volume of the second subwoofer to zero, the imaging returns / problem goes away?

Your crossed over very low, especially for those large subwoofers with fairly small mains. I'd try 80Hz as a solid starting place.

Another thing that can kill the perception of imaging is too much bass. A lot of people add subwoofers thinking they'll be adding 'punch' .. but, 'punch' comes from the lower midrange. Taking some stress off the Def Tech's midrange drivers might really help them perform better. Then to get more bass, you simply turn up the volume.

 

[shadyJ]

50 Hz is pretty low for those speakers. You would be doing your speakers a bigger favor by taking the crossover up 10 or 20 Hz. No way are they going to play 50 hz as cleanly as your subs.

What's strange is how is subs causing those kind of issues at such a low crossover point and steep rolloff? Your subs shouldn't even be seeing that much use, especially for music, at those settings. I think the problem might be deeper than just phase issues.

 

[Muzykant]

Thank you for your prompt replies!

Both subs are set the same, with all the fancy adjustments set to off, phase set to 0, and gain to -5. Setting it to -10, for example, provides pretty weak bass. With my current setting, the subs' cones move less than one inch (2 ways) during peaks.

Setting the crossover to a higher position sounded like a very logical thing to do, but I could always localize the sub (when I had only one) and missed some of the mid bass details from the speakers. I had it at 60 hz for a while, but lowering it to 50 was a clear improvement. With 2 subs the higher I set the crossover, the worse it sounds.

Turning either one of the subs off fixes the problem.

 

[ski2xblack]

That's just weird. Maybe one of the drivers are mis-wired within your subs, making your 'zeroed out' setting not actually zeroed out on one of them. Try a face-to-face cancellation test with the subs to check for this.

 

[Muzykant]

I tried setting the phase to 180 and anything in between on the new sub. Having both of them at 0 seems to provide the strongest bass.

I know this sounds weird. After a week of searching, I couldn't find anything online to help the issue.

Maybe I should find the microphone for UMC-200 and run the room correction software. I never even unpacked that microphone, good luck to me finding it...

 

[ski2xblack]

Ok. So much for that bright idea.

We may be veering off into speaker/room issues that require more information. You're using two subs presumably for modal smoothing, not increased output, yes? What is your room like? For a typical rectangular room, you may want to try centrally located subs on opposing walls, for example. Do you have any sort of RTA gear to get a more solid handle on what's going on? How old is the AVR? The latest and greatest Audyssey is much better than older versions. Tell us more.

 

[crossedover]

Thank you for your prompt replies!

Both subs are set the same, with all the fancy adjustments set to off, phase set to 0, and gain to -5. Setting it to -10, for example, provides pretty weak bass. With my current setting, the subs' cones move less than one inch (2 ways) during peaks.

Setting the crossover to a higher position sounded like a very logical thing to do, but I could always localize the sub (when I had only one) and missed some of the mid bass details from the speakers. I had it at 60 hz for a while, but lowering it to 50 was a clear improvement. With 2 subs the higher I set the crossover, the worse it sounds.

Turning either one of the subs off fixes the problem.

The mid bass from your mains is never going to compare to those subs. You won't localize till you start getting over 110/120Hz. Hard to do the crawl test with those subs and with two. Start with phase adjustments and see from there.

 

[ImcLoud]

time to call SVS or Emotiva...

 

[Muzykant]

I really don't want to call those companies unless I absolutely have to. I called SVS once about my SB-2000 not turning on after I moved it, and they were ready to send me a replacement. And then I saw that I connected the sub to the wrong out and it was so embarrassing! Months later that episode still bugs me.

Room is 17X20 feet with slanted ceiling. Roughly it's about 3100 square feet. The TV is positioned in the middle of the longer wall, with speakers and subs symmetrically to its sides. The mid section of the rear wall is a large glass door, so subwoofer can't be positioned there. On my left and right I have bookcases with glass doors opening out, so it's impossible to place subwoofers there as well.

 

[MidnightSensi2]

Well, subwoofers don't image - period. That said, even at 24db/octave, some midrange content will be played through the subwoofers. If their amplitude is significantly higher than the mains levels (which, most homes run subwoofers pretty hot), that could cause phase issues with the speakers to be more noticeable.

Besides adjusting placement, here are a few other things to try:
What does the newer subwoofer sound like on its own? We can rule out the second/newer subwoofer by lowering the volume of the first/older one that you know works.

Might also help to remove the Emotiva from the chain and try using the subwoofers crossovers to see if the Emotiva is doing something weird in bass.

...

If there is no mechanical defect in the chain, I have a hunch placement is the issue.

 

[Muzykant]

Once again, thank you for your replies. Both subs sound just about the same (the new one moves a tad less during the peaks, probably because it's not broken in). I am now almost convinced it's the phase issue. It makes sense because the higher I set the crossover, the worse the soundstage gets. Higher sounds are more localized, and issues in that register are more apparent to the ear.

Does anybody have any suggestions about how to pinpoint the problem with the phase and solve it? Are there any procedures/tests?

Thanks a lot!

 

[crossedover]

Once again, thank you for your replies. Both subs sound just about the same (the new one moves a tad less during the peaks, probably because it's not broken in). I am now almost convinced it's the phase issue. It makes sense because the higher I set the crossover, the worse the soundstage gets. Higher sounds are more localized, and issues in that register are more apparent to the ear.

Does anybody have any suggestions about how to pinpoint the problem with the phase and solve it? Are there any procedures/tests?

Thanks a lot!

Are you using the crossover on the subs and the Emotiva? Just for grins move the inputs from lfe to the stereo and use just the subs crossover and set the Emotiva to full range (ie run them from the main preouts) and see what sound you get.

 

[GIEGAR]

Once again, thank you for your replies. Both subs sound just about the same (the new one moves a tad less during the peaks, probably because it's not broken in). I am now almost convinced it's the phase issue. It makes sense because the higher I set the crossover, the worse the soundstage gets. Higher sounds are more localized, and issues in that register are more apparent to the ear.

Does anybody have any suggestions about how to pinpoint the problem with the phase and solve it? Are there any procedures/tests?

Thanks a lot!

It's really just a stab in the dark at what the problem(s) might be. You now have a pair of top notch subs with a good set of speakers... I suggest you now make a relatively small investment in room measurement and analysis gear. This will pinpoint any problems quickly and allow you to optimise what you have for your room. These are both excellent options with abundant on online support:

• Dayton Audio OmniMic V2 Precision Measurement System ($298 shipped)
  
  
• miniDSP UMIK-1 ($75 ex. shipping) plus REW (Free!)