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Subwoofer pushed too hard?


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32 replies to this topic

#1 of 33 OFFLINE   Sam Pat

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Posted June 16 2004 - 05:02 AM

I have a Paradigm PS1200 which I bought a couple of months ago. Been having lots of fun with movies at loud volumes, where it literally shakes the house. It's a hoot!

However, recently I told this to my friend and he mentioned that I should make sure I'm not overdriving the sub. I'm really an audio noob so this sort of thing isn't intuitive for me. I've been running it hard because I haven't noticed any major distortions (like the bass sounding totally loose, or rattling really loud). Making matters more complicated, I do almost 100% movies which means alot of the time it's hard to tell whether my sub is distorting or it's the signal.

From listening position, I do hear rattles on occassion when playing at my normal, pretty loud volumes, but alot of that is from the blinds and doors and other furniture of the room so I've been ignoring them.

I decided to put on a test. I would play a bassy sequence over and over and put my ear up to the sub turning the volume up and down. However, I noticed that even at moderate volumes, I hear a slight rattle coming from the sub. My buddy told me that ANY rattle from the sub is bad - something about the cone hitting something. I normally play the sub louder than the volumes where I first start hearing a rattle, too. So does this mean I've been beating the sub too hard and it's now damaged?

How do you tell whether you're pushing the sub too hard? What is this "clack" I've heard about? Is my sub OK?

I've also read that the sub I have tends to be boomy, so is that why it tends to rattle slightly?

#2 of 33 OFFLINE   Ryan Leemhuis

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Posted June 16 2004 - 07:16 AM

Well....I don't know about your rattling sound but if you are overdriving it...it will sound frankly like your sub is farting. Its loud...annoying bass. Unfortunately it can be tough to notice. You have to be careful.

#3 of 33 OFFLINE   Ted Lee

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Posted June 16 2004 - 08:30 AM

Quote:
However, I noticed that even at moderate volumes, I hear a slight rattle coming from the sub. My buddy told me that ANY rattle from the sub is bad - something about the cone hitting something.
don't quote me on this, but i think you're talking about the excursion of the driver.

it's the amount of "travel" that the woofer cone can move. if you push it too hard, you cause the bass driver to bottom or top-out. kinda like a car engine piston slamming into the engine.

if you're hearing this rattle, even at low volumes, then i would agree that something may not be right. you may wanna get it checked out.

ps, while bass is good, too much bass is really *not* good. you should calibrate your sub (do a search for how to do that), then bump it up a touch if you want. only for special occasions, i'll allow you to crank it up! Posted Image
 

#4 of 33 OFFLINE   Sam Pat

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Posted June 16 2004 - 09:48 AM

Thanks for the replies. I still don't know whether my sub is broken, or whether I've been overdriving it. Any sure way to find out?

#5 of 33 OFFLINE   Ted Lee

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Posted June 16 2004 - 10:03 AM

Quote:
I still don't know whether my sub is broken, or whether I've been overdriving it.
isn't that the same difference? Posted Image
 

#6 of 33 OFFLINE   keir

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Posted June 16 2004 - 10:04 AM

more often than not, it is a wallboard or other lose item near the sub that's making the sound. you might try moving the sub away from that wall and playing at the same volume to see if the rattle goes away or is obviously coming from somewhere else. at moderate volume the sub wouldn't rattle unless theres a piece loose somewhere, which is doubtful. i wouldn't worry about driving the subwoofer too hard. its much harder to damage a subwoofer driver than say, a tweeter driver. if you reach the excursion limit of the driver it may make a pretty noticable sound when the driver slaps against whatever suspension is nearest. if the sub is in distress the sound it makes should be pretty obviously uncharacteristic of normal bass notes.

just wanted to add, you should probably get a sound level meter and test disk. a lot of the time people run their subwoofer much louder than the other speakers, and that could definately cause a subwoofer to be driven beyond it's limits. bumping the bass a little is ok, but when you have it 15 dB higher than the other speakers you can easily run into trouble.

#7 of 33 OFFLINE   Sam Pat

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Posted June 16 2004 - 10:47 AM

Thanks, keir. I'll try that.

Before I do, that slapping sound you're speaking of when being run to its limits, will it be noticeable at the listening position? The rattling I'm hearing from the sub is slight, I need to put my ear next to the ports to hear it.

#8 of 33 OFFLINE   Johnny_M

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Posted June 16 2004 - 11:08 AM

I wouldnt worry too much about a rattle. Could be the driver or the amp just not tightened down enough. When you ruin a sub you will know it. You might want to get an SPL meter and find out how loud your actually pushing it. You may be over reacting for nothing.


Johnny

#9 of 33 OFFLINE   Sam Pat

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Posted June 16 2004 - 11:09 AM

I just did more listening. Maybe the sound I'm hearing isn't a rattle, after all. It's not distinct enough to be classified as a rattle. It's more like looseness. But I don't even know if it's just that particular signal that's loose. You know the theme song from the Sopranos? That's what I've been using. The louder I put the sub, the more "loose" it gets. How loose is too loose? How loose is = overdriving the sub? Even at the loudest, I don't really hear any distinct "rattle", just more looseness. At the highest volume, the bass becomes a flubbing noise, like it's fluttering or choking. I take that to mean that's bad. But at moderate volumes, it's just a scaled down version of that. It's just less loose.

I'm so confused.

#10 of 33 OFFLINE   Johnny_M

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Posted June 16 2004 - 11:18 AM

If your comfortable doing this, and if its easily accessable on your sub, take the driver out of the box and then play your theme song. If the problem is the speaker you will still hear that sound. If the sound goes away its probably just a rattle.


Johnny

#11 of 33 OFFLINE   Sam Pat

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Posted June 16 2004 - 11:24 AM

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.

#12 of 33 OFFLINE   Aaron Gilbert

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Posted June 16 2004 - 11:25 AM

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. Posted Image


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#13 of 33 OFFLINE   Aaron Gilbert

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Posted June 16 2004 - 11:30 AM

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.


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#14 of 33 OFFLINE   Sam Pat

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Posted June 16 2004 - 11:45 AM

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.

#15 of 33 OFFLINE   Aaron Gilbert

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Posted June 16 2004 - 11:54 AM

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

#16 of 33 OFFLINE   Sam Pat

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Posted June 16 2004 - 05:02 AM

I have a Paradigm PS1200 which I bought a couple of months ago. Been having lots of fun with movies at loud volumes, where it literally shakes the house. It's a hoot!

However, recently I told this to my friend and he mentioned that I should make sure I'm not overdriving the sub. I'm really an audio noob so this sort of thing isn't intuitive for me. I've been running it hard because I haven't noticed any major distortions (like the bass sounding totally loose, or rattling really loud). Making matters more complicated, I do almost 100% movies which means alot of the time it's hard to tell whether my sub is distorting or it's the signal.

From listening position, I do hear rattles on occassion when playing at my normal, pretty loud volumes, but alot of that is from the blinds and doors and other furniture of the room so I've been ignoring them.

I decided to put on a test. I would play a bassy sequence over and over and put my ear up to the sub turning the volume up and down. However, I noticed that even at moderate volumes, I hear a slight rattle coming from the sub. My buddy told me that ANY rattle from the sub is bad - something about the cone hitting something. I normally play the sub louder than the volumes where I first start hearing a rattle, too. So does this mean I've been beating the sub too hard and it's now damaged?

How do you tell whether you're pushing the sub too hard? What is this "clack" I've heard about? Is my sub OK?

I've also read that the sub I have tends to be boomy, so is that why it tends to rattle slightly?

#17 of 33 OFFLINE   Ryan Leemhuis

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Posted June 16 2004 - 07:16 AM

Well....I don't know about your rattling sound but if you are overdriving it...it will sound frankly like your sub is farting. Its loud...annoying bass. Unfortunately it can be tough to notice. You have to be careful.

#18 of 33 OFFLINE   Ted Lee

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Posted June 16 2004 - 08:30 AM

Quote:
However, I noticed that even at moderate volumes, I hear a slight rattle coming from the sub. My buddy told me that ANY rattle from the sub is bad - something about the cone hitting something.
don't quote me on this, but i think you're talking about the excursion of the driver.

it's the amount of "travel" that the woofer cone can move. if you push it too hard, you cause the bass driver to bottom or top-out. kinda like a car engine piston slamming into the engine.

if you're hearing this rattle, even at low volumes, then i would agree that something may not be right. you may wanna get it checked out.

ps, while bass is good, too much bass is really *not* good. you should calibrate your sub (do a search for how to do that), then bump it up a touch if you want. only for special occasions, i'll allow you to crank it up! Posted Image
 

#19 of 33 OFFLINE   Sam Pat

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Posted June 16 2004 - 09:48 AM

Thanks for the replies. I still don't know whether my sub is broken, or whether I've been overdriving it. Any sure way to find out?

#20 of 33 OFFLINE   Ted Lee

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Posted June 16 2004 - 10:03 AM

Quote:
I still don't know whether my sub is broken, or whether I've been overdriving it.
isn't that the same difference? Posted Image
 


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