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Subwoofer Blown? Squeeling

post #1 of 16
Thread Starter 
Hey guys,

I'm having an issue with my subwoofer squealing/whistling. I'm not sure if it's a settings issue, or something actually wrong with the unit.

I have the Energy Take Classic II 5.1 system, but I replaced the front satellites with 2 Polk Audio RTi10 Towers with the AMP on the receiver set to BI-AMP.

I have a Denon 1712 AVR.

I ran the Audessey EQ Auto setup and went through all 8 passes, following this guide for my setup...

http://batpigworld.com/index.html

I have my sub connected via a sub cable, with the volume set to 50%, and the Low-Pass Filter set to Max.

In my receiver settings, I set my fronts to small, and left everything else to the Auto Audesssey setup. The only setting I changed was my LFE+Main Crossover Freq. to 80hz, from 40hz, which is the THX recommended setting.

The squealing/whistling seems to actually be caused by a large of amount of air rushing out of the front port hole, and not the actual sub on the bottom of the box (down-firing sub). The whistling seems to happens with very loud, very low freq sounds.
post #2 of 16
That's called port chuffing, and it's generally a sign that the subwoofer is being run too hard.

Since you have towers now that run about as low as the sub, you might try running them in Large mode such that they handle their own bass and just let the sub help the other speakers that need it.

Second, if your subwoofer channel level is close to -12db, turn down the gain (volume) on the sub such that Audyssey gives you a sub channel (trim) level much closer to 0.
post #3 of 16
Thread Starter 
The Auto EQ set the sub to +1.5 during auto setup.

Setting my fronts to Large didn't seem to have any affect on the issue.

Question. The Low-Pass Filter knob on the back of my Sub, is it normal that adjusting this, while connected to the reciever will have an effect on the level of bass?

My guide I read told me to set to to it's Max, which is 150Hz, and let the reciever control the real LPF.

But adjusting the LPF on the actual sub, still affects the level of bass, even going through the reciever.
post #4 of 16
You can also try running your fronts at a lower crossover setting for your mains to take some stress off the sub. 40hz or 60hz will be fine with those towers. THX and Dolby recommendations are only great if they make your system sound good
post #5 of 16
I saw that you hadn't gotten any more suggestions and realized my previous comment probably wasn't any help (lol).

Here's a thought that could help. If the sub was not having this problem before, and you moved the sub to a new location when you got your towers, the new placement could cause the problem. Subs respond better or worse in different places in a room. If you moved it somewhere that the sub has more trouble producing bass, Audyssey would have upped the channel level and possibly changed its EQ filters to compensate when you reran Audyssey. This would make the sub work harder to produce the same volume.
post #6 of 16
Thread Starter 
I never moved the sub, but I did mess with the settings a bit, I may re-run Audessy EQ.

If I want to take some of the stress of my towers, would I set my fronts to Large and the bass setting to LFE instead of LFE+Main?

And you were saying possibly change the front crossover to 60hz?
post #7 of 16
Quote:
Originally Posted by TotalMalice View Post

If I want to take some of the stress of my towers, would I set my fronts to Large and the bass setting to LFE instead of LFE+Main?

It may or may not help to run the towers as large and only run the LFE to the sub, because it could be the LFE signal, which is the .1 on 5.1 bluray and dvd, which is what's causing your sub to freak out.

Quote:
Originally Posted by TotalMalice View Post

And you were saying possibly change the front crossover to 60hz?

That was a dunderheaded suggestion on my part since you already said you were running your crossover at 80hz.

One thing you can do is the sub crawl. That can tell you where your sub performs the best in your room.

Any anytime you move the sub, then you have to rerun Audyssey. But changing the settings doesn't require you to rerun Audyssey.
post #8 of 16
Thread Starter 
One thing I also noticed, and I'm not sure if this is boneheaded on my part, I'm not using both the L & the R on the sub. I have the Audio cable running from the sub Pre-Amp into the R, but I don't have a Y-Cable installed. Would this make any difference?
post #9 of 16
I'm not convinced, but some people think that gives the sub more volume. It could make it louder at a given gain(volume) setting on the sub, although it's hard to see how this could increase the maximum volume that the sub can reach. If you can easily, you can try and see if it makes a difference.
post #10 of 16
Thread Starter 
I was able to reduce the chuffing somewhat, but only through adjusting my sub DB.

I reran my Audessey EQ XT, doing the full 8 passes. It set the sub @ +3.0db. I got insane port chuffing. I was able to almost get rid of it, but only by setting my sub @ -5.0db. The downside is, I get much less bass response.

Playing with the SMALL/LARGE, and frequency responses didn't seem to have any effect.
post #11 of 16
Sounds like your sub is just not powerful enough for that room. For instance, HSU which makes a higher quality 8" sub, only rates their STF-1 in rooms up to 1500 cubic feet (click the loudness icon).

See, those 8" Energy subs that come with the Takes are more mid-bass modules than subwoofers. They really won't offer much more low bass than your towers can and they just don't have that much power. You can ask on the AVS subwoofer forum. I'm pretty confidant they'll tell you that your next upgrade should be the sub.
post #12 of 16
Thread Starter 
You may be right. It's odd though, before I had the RTi10's, and was running the full Take set, I never seemed to have the issue, maybe it's cause it wasn't calibrated properly before.

I added on the Bi-Amped RTi10's, and did the full 8-pass cali with Audessy EQ XT, and then I noticed the issue.
post #13 of 16
Port noise/chaffing is caused by air speed exiting the port exceeding design limits.

Low frequencies == larger cone movement == faster air speed.
Higher volume == larger cone movement == faster air speed.

I "stuff" ports sometimes (socks or whatever to try things out) yes it changes the way the sub sounds and but it gets ride of a whole class of noises related to air speed.

Have Fun!
post #14 of 16
Quote:
Originally Posted by kmannth View Post

I "stuff" ports sometimes (socks or whatever to try things out) yes it changes the way the sub sounds and but it gets ride of a whole class of noises related to air speed.

That's got to be risky to slow down the air exiting from a sub that's already being pushed close to its limits.
post #15 of 16
Quote:
Originally Posted by cel4145 View Post


That's got to be risky to slow down the air exiting from a sub that's already being pushed close to its limits.

Actually it sort of turns the system into a sealed system. The ports no longer function to extend performance into lower frequencies. The sub will start rolling off higher in frequency but will roll offering slower. As I understand it, because the blocked port(s) aren't really sealed, once you get below a frequency somewhere around the original port tuning the driver ceases to be controlled by air pressure in the box (unloads) and can be caused to self destruct
post #16 of 16
"Self destruct" definitely = bad

LOL

Thanks for the explanation.
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