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AVS › AVS Forum › Audio › Subwoofers, Bass, and Transducers › What does it mean for a sub to bottom out?
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What does it mean for a sub to bottom out?

post #1 of 27
Thread Starter 
Like what happens to the sound? Just wondering if I have experienced it with my sub.
post #2 of 27
it sounds.....funny. lol, bad way to say that. its just that the sub has reached the limit of its excursion. it has a thumpy wumpy sound. like if it was wired backwards.
post #3 of 27
Best I can describe it is a clacking sound.

A speaker cone moves in and out. It can only move so far. When it bottoms out it is hitting its maximum extension.
post #4 of 27
Quote:
Originally Posted by swgiust View Post

Best I can describe it is a clacking sound.

Spot on. The sound it makes is reminiscent of a sledgehammer hitting a frying pan. Uh. .

Regards,
post #5 of 27
Not all subwoofers sound the same when they bottom. Depends on how they were manufactured and other things like limiters preventing a "hard bottom" on commercial subs. Some woofers are made to "soft bottom" so that way they don't contact the back plate and warp the VC former in a permanent way. Other times its just an electronic limiter coming into play to prevent the woofer from being overdriven. So in that case, the sound of the subwoofer may just sound flat, compressed or distorted.

I don't really overdrive my subwoofers anymore...mainly because I will prolly break more than the woofer if I attempt to do that... but I've heard a few bottom. The ones I heard sound like a thumpy sound when it bottom. Or kinda like a "WHOMP!" sound. Some people have bottomed their subs and heard a hard metallic "CLANK!" sound. That is definitely a bad sound and not one you want to reproduce often. That is if you want to keep said woofer in working condition.
post #6 of 27
Wait til the end of the video. Oops. Luckily my sub didn't have any permanent damage.

http://www.youtube.com/watch?v=nsGnGDUsAKQ
post #7 of 27
What about the "farting" noise?
post #8 of 27
Quote:
Originally Posted by ecox View Post

Wait til the end of the video. Oops. Luckily my sub didn't have any permanent damage.

http://www.youtube.com/watch?v=nsGnGDUsAKQ

This hurt me to watch. Ouch!
post #9 of 27
i used to bottom out my HSU VTF3 MKii quite often...hence why i sold it. obviously i was pushing it too hard..so i ordered 2 MFW15's to replace it. hopefully that will be enough bass for me.
post #10 of 27
Thread Starter 
Quote:
Originally Posted by ecox View Post

Wait til the end of the video. Oops. Luckily my sub didn't have any permanent damage.

http://www.youtube.com/watch?v=nsGnGDUsAKQ

oh my. ok, i guess my sub has never bottomed out before.
post #11 of 27
My cheap Onkyo HTIB sub would bottom out fairly often, and I wasn't watching many bass heavy movies. Upgrading it solved that problem.
post #12 of 27
Here's a better video of a driver bottoming out. It is the clacking noise at the end. I have those subs and to get the voice coil to hit the back plate, the cone is moving 40+mm in each direction.

http://www.youtube.com/watch?v=2QFAT...eature=related

-Robert
post #13 of 27
Kind of curious, I am purchasing a PB-13 Ultra next month and am wondering what it would take to bottom that thing out? Would I have to be pushing way beyond reference? Kinda new to this...

Thx
post #14 of 27
Quote:
Originally Posted by Rebellion View Post

Kind of curious, I am purchasing a PB-13 Ultra next month and am wondering what it would take to bottom that thing out? Would I have to be pushing way beyond reference? Kinda new to this...

Thx

Some driver's can't be bottomed out. It all depends on their design. Since the ultra driver uses an underhung voice coil, it is much shorter so there must be much more excursion to bottom it out. My guess is that the suspension components (spider and surround) will fail before the driver bottoms out. But since this is a complete sub, SVS will try to make it bottom out proof. The amp has a subsonic filter to block extreme low bass and I'm sure there is more than enough suspension travel in the driver.

But if you really want to try, you can make sure all 3 ports are not blocked and set the amp to sealed mode. That should eliminate the subsonic filter. Then play a 10hz tone at full blast.

-Robert
post #15 of 27
Quote:
Originally Posted by rlj5242 View Post

Here's a better video of a driver bottoming out. It is the clacking noise at the end. I have those subs and to get the voice coil to hit the back plate, the cone is moving 40+mm in each direction.

http://www.youtube.com/watch?v=2QFAT...eature=related

-Robert

What is the jackhammer-like sound that precedes the loud clack at the end? I ask because if turned up loud enough, my sub will make that sound when I play test tones below 40 Hz.
post #16 of 27
Quote:
Originally Posted by ecox View Post

Wait til the end of the video. Oops. Luckily my sub didn't have any permanent damage.

http://www.youtube.com/watch?v=nsGnGDUsAKQ

My Insignia sub did that on Valkyrie When I had it running too hot!
post #17 of 27
The sharp crack you hear on some subs when the bottom out is the voice coil former (bobbin) hitting the back of the magnet!

This can warp the former causing the voice coil to rub in the magnetic gap. The cure for this is a new voice coil, a delicate and in most cases, uneconomical procedure on most home and car audio woofers. Some professional units have field replaceable cones or baskets.

If its hard enough, one bottom can destroy a woofer. A few small subwoofers met their doom this way after I fixed a 200W amp that was given to me when I was 17.... my first taste of real power. (fond memories.... that system lives on now that I'm in college, its just gotten smarter and a lot cleaner but its still the envy of more than a few frat houses)

Some woofers have a "bumped back" magnet which reduces the likelihood of hard bottoming. Soft bottoming is extending the suspension (the spider and surround) to their maximum limits. Over time this can damage the suspension. Once the suspension becomes excessively compliant, the likelihood of bottoming increases.
post #18 of 27
Quote:
Originally Posted by tima94930 View Post

Quote:
Originally Posted by rlj5242 View Post

Here's a better video of a driver bottoming out. It is the clacking noise at the end. I have those subs and to get the voice coil to hit the back plate, the cone is moving 40+mm in each direction.

http://www.youtube.com/watch?v=2QFAT...eature=related

-Robert

What is the jackhammer-like sound that precedes the loud clack at the end? I ask because if turned up loud enough, my sub will make that sound when I play test tones below 40 Hz.

By "jackhammer-like sound that precedes the loud clack at the end", I'm asking about the several instances of seconds-long, fluttering, sputtering, motorboating, jackhammer sounds that comprise the first 16 seconds or so of the video, that are completely different than the loud clack at the end of the video, after which, there is silence. The clack occurs at about 0:17. The fluttering noise is what I get if I play (say) a 25 Hz test tone above a certain loudness. In contrast, if I play (say) a 40 Hz test tone, it sounds like a continuous pure tone. Is there an explanation for it?
post #19 of 27
"What does it mean for a sub to bottom out?"

It means it's time to buy a bigger sub
post #20 of 27
over time you will be able to see when the speaker is reaching its limit rather then hear it. If you just pay close attention to how far its moving you will know when to back off the power to the sub.

The foam suspension should be an indication of how far it can move. Some of the foam surrounds on these newer woofers look like small bike tire inner tubes or somthing and most can move along way out.
post #21 of 27
Quote:
Originally Posted by tima94930 View Post

By "jackhammer-like sound that precedes the loud clack at the end", I'm asking about the several instances of seconds-long, fluttering, sputtering, motorboating, jackhammer sounds that comprise the first 16 seconds or so of the video, that are completely different than the loud clack at the end of the video, after which, there is silence. The clack occurs at about 0:17. The fluttering noise is what I get if I play (say) a 25 Hz test tone above a certain loudness. In contrast, if I play (say) a 40 Hz test tone, it sounds like a continuous pure tone. Is there an explanation for it?


Two reasons, the sub is in free air, bass is canceled out and much of the asymmetrical distortion does not, But that's about 10% of what you hear, the other 90% is because the vent is resting on the counter (top of the box in this case) and you hear the air squeezing out of the vent between the t-yoke and flat surface, the air pressure is very high and is lifting the sub woofer off the table and making it rattle.. you can see the driver moving in the video, its 35 pounds and the moving mass is only about 250 grams... its trying really hard to vent!

here is another free air video with 18's. Below 10Hz, it sounds exactly like a motorcycle
http://www.youtube.com/watch?v=8yZjSYdtBck
post #22 of 27
Kool vid Kyle.

I always like seeing the TC skunkworks in action.
post #23 of 27
Quote:
Originally Posted by rnatalli View Post

"What does it mean for a sub to bottom out?"

It means it's time to buy a bigger sub

Or Put your (Alcoholic) Drink down, because you have it up too loud.
post #24 of 27
Quote:
Originally Posted by union1411 View Post

What does it mean for a sub to bottom out?

It means its upgrade time, give Mark Seaton a call.
post #25 of 27
Quote:
Originally Posted by ecox View Post

Wait til the end of the video. Oops. Luckily my sub didn't have any permanent damage.

http://www.youtube.com/watch?v=nsGnGDUsAKQ

Yeah, wow! That was very bad.


Tim
post #26 of 27
Quote:
Originally Posted by OvalNut View Post

Yeah, wow! That was very bad.


Tim

You havent seen bad until the surround falls off.
post #27 of 27
Quote:
Originally Posted by KyleLee View Post

here is another free air video with 18's. Below 10Hz, it sounds exactly like a motorcycle
http://www.youtube.com/watch?v=8yZjSYdtBck

Would it be correct to say that making it sound like a motorcycle for a short period of time isn't harmful, but making it bottom out is?

(If it matters, my sub is sealed.)
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