Subwoofer pushed too hard? (1 Viewer)

[Sam Pat]

I called the dealer and they told me that the PS1200 has a safety cut-off, and you shouldn't even be able to play it loud enough to cause damage. Is he BSing me? I DID notice some printing about safety cutout on the back of the sub.

 

[Sam Pat]

I called the dealer and they told me that the PS1200 has a safety cut-off, and you shouldn't even be able to play it loud enough to cause damage. Is he BSing me? I DID notice some printing about safety cutout on the back of the sub.

 

[Aaron Gilbert]

Sam,

It would be hard to miss the driver reaching it's excursion limits, even in the middle of a loud action movie sequence. Driver bottoming is a very loud pronounced POP. You do start to get much greater levels of distortion as the driver goes beyond it's linear excursion range, as you describe. That said, what you describe could also be attributed to the amplifier running out of steam, or even some volume limiting circuitry kicking in. Without removing the woofer from the enclosure and testing it outside the box with a different amplifier (which I do not recommend you do!), it's hard to say which is limiting your unit, the woofer or the amp.

As has been mentioned, really any rattle sound is bad, regardless of the volume level. My subwoofer has a minimal buzz at certain frequencies, which I have determined to be a problem with the voice coil. However, it's only audible using test tones and even then you have to be really close to the woofer. I could send it in for repair/replacement under warranty, but as it's inaudible with real material, I haven't bothered yet.

In your case, it seems more like you are just reaching the output limitations of the unit. Generally speaking, as long as the electrical power handling is not exceeded and you are not bottoming the woofer, you're not going to do damage to the woofer or amp. Whether you should actually listen to something with obvious distortion, or decrease the volume, is up for debate.


Aaron Gilbert

 

[Aaron Gilbert]

Sam,

It would be hard to miss the driver reaching it's excursion limits, even in the middle of a loud action movie sequence. Driver bottoming is a very loud pronounced POP. You do start to get much greater levels of distortion as the driver goes beyond it's linear excursion range, as you describe. That said, what you describe could also be attributed to the amplifier running out of steam, or even some volume limiting circuitry kicking in. Without removing the woofer from the enclosure and testing it outside the box with a different amplifier (which I do not recommend you do!), it's hard to say which is limiting your unit, the woofer or the amp.

As has been mentioned, really any rattle sound is bad, regardless of the volume level. My subwoofer has a minimal buzz at certain frequencies, which I have determined to be a problem with the voice coil. However, it's only audible using test tones and even then you have to be really close to the woofer. I could send it in for repair/replacement under warranty, but as it's inaudible with real material, I haven't bothered yet.

In your case, it seems more like you are just reaching the output limitations of the unit. Generally speaking, as long as the electrical power handling is not exceeded and you are not bottoming the woofer, you're not going to do damage to the woofer or amp. Whether you should actually listen to something with obvious distortion, or decrease the volume, is up for debate.


Aaron Gilbert

 

[Aaron Gilbert]

Sam,

Ah, my guess about the volume limiter was correct, then. An easy way to test this type of circuitry is to do this *carefully*. Turn your receiver/processor volume down all the way. Turn the gain/level control on the subwoofer amp up all the way. Get a CD with test tones and select a fairly low frequency, say between 20Hz and 40Hz. Now turn the volume of the receiver up slowly while watching the excursion of the woofer. There should come a point where increasing the volume of your receiver makes no change in the excursion of the woofer. Some of this circuitry is done very well, so that you can't really tell it's even working (without actually watching). Others affect the sound a bit, adding their own type of distortion, which is hopefully still much less objectionable than actually overdriving the woofer would be.


Aaron Gilbert

 

[Aaron Gilbert]

Sam,

Ah, my guess about the volume limiter was correct, then. An easy way to test this type of circuitry is to do this *carefully*. Turn your receiver/processor volume down all the way. Turn the gain/level control on the subwoofer amp up all the way. Get a CD with test tones and select a fairly low frequency, say between 20Hz and 40Hz. Now turn the volume of the receiver up slowly while watching the excursion of the woofer. There should come a point where increasing the volume of your receiver makes no change in the excursion of the woofer. Some of this circuitry is done very well, so that you can't really tell it's even working (without actually watching). Others affect the sound a bit, adding their own type of distortion, which is hopefully still much less objectionable than actually overdriving the woofer would be.


Aaron Gilbert

 

[Sam Pat]

Very helpful post, Aaron!! Thanks.

I feel a bit better in that I have never heard a POP like that.

I used another tone, the Amp's test tone and it was very tight even at loud volumes, except the rattle is much better isolated and definitely there. It sounds like something is loose inside the enclosure. But like yours, I can't hear it unless I stick my ear at the ports. So I'll give it more time; the dealer said they'll be happy to fix it under warranty -- he suggested I tighten some screws on the woofer's amp first.

When you said amp, did you mean the amp built into the woofer or my receiver's amp? I have an entry level receiver, a Sony 595, and I'm not sure it's always providing enough juice, if that is related.

 

[Sam Pat]

Very helpful post, Aaron!! Thanks.

I feel a bit better in that I have never heard a POP like that.

I used another tone, the Amp's test tone and it was very tight even at loud volumes, except the rattle is much better isolated and definitely there. It sounds like something is loose inside the enclosure. But like yours, I can't hear it unless I stick my ear at the ports. So I'll give it more time; the dealer said they'll be happy to fix it under warranty -- he suggested I tighten some screws on the woofer's amp first.

When you said amp, did you mean the amp built into the woofer or my receiver's amp? I have an entry level receiver, a Sony 595, and I'm not sure it's always providing enough juice, if that is related.

 

[Aaron Gilbert]

Sam,

Actually, your receiver's power amps have nothing to do with the power being provided to your subwoofer. That all comes from the amp built into the subwoofer. Your receiver is just providing a preamp-level signal and not expending any power at all to drive the subwoofer. I was actually referring to the amp in the subwoofer itself running out of steam.

Rattles can be pesky things to isolate, but it does become a lot easier with test tones, or better yet, a sweepable signal generator. Tightening screws would certainly be a good start. If you have a definite rattle though, it's also possible that you have a wire inside the enclosure that's touching the back of the woofer or the inside wall of the box. Loose screws usually don't cause rattles, but rather air leaks.


Aaron Gilbert

 

[Aaron Gilbert]

Sam,

Actually, your receiver's power amps have nothing to do with the power being provided to your subwoofer. That all comes from the amp built into the subwoofer. Your receiver is just providing a preamp-level signal and not expending any power at all to drive the subwoofer. I was actually referring to the amp in the subwoofer itself running out of steam.

Rattles can be pesky things to isolate, but it does become a lot easier with test tones, or better yet, a sweepable signal generator. Tightening screws would certainly be a good start. If you have a definite rattle though, it's also possible that you have a wire inside the enclosure that's touching the back of the woofer or the inside wall of the box. Loose screws usually don't cause rattles, but rather air leaks.


Aaron Gilbert

 

[Matt_Smi]

Rattles/buzzing is not necessarily always a bad thing, like stated above it could just be a loose screw or something inside rubbing against something else when the bass hit causing the noise. My sub has a slight rattle that you can only hear with the front speakers off and with your ear right next to the sub. I put pressure on a few things around the back of the sub and it turns out that I can make the rattle stop by pressing firmly on the port hole in the back. So this tells me that it is not the driver or anything loose inside the cabinet, but is just the seam where the port is connected to the cabinet buzzing a bit, probably because it is not perfectly tight against the cabinet. It does not concern me because I cannot hear it when I am normally listening to music or watching a movie, and I know that there is nothing wrong with the driver. If the noise is not coming from the driver than I would not worry about it, if it is than it may be a cause for concern.

 

[frank manrique]

In order to play at spirited sound pressure levels and to lessen your current sub's work load burden, you'll need to get another sub...a 1200 model preferably. I reckon that your rattle problems will most likely disappear!

Costly a cure? Yes, but then what are the alternatives?

Remember this audio-related axiom, too: there simply is no substitute for displacement...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[Sam Pat]

Heheh, car guy here, and don't I know it... no replacement for displacement is my automotive philosophy too.