What causes a loudspeaker to distort at low volume?

BillyB_from_LZ · #1 01-04-2007, 02:20 PM

I have a spare Hartke XL series 10 in. woofer.

When playing through it at conversational levels, the sound from it is distorted (like the amp is overloading, but it isn't). Gently pushing on the cone with even pressure, there were no rubbing sounds and I couldn't find any damage to the cone, surround, dust cap or spider. One would assume then that the voice coil was damaged and that the speaker is "blown".

Since no one sells a recone kit for Hartke aluminum cone speakers (this one is made by Eminence... Spec. No. 10768, built 18th week of 1995), I figured that I might as well have some fun with it.

Last night, I disassembled the speaker, carefully removing all of the moving parts as one unit. I found the voice coil to be in pristine condition...no signs of overheating, rubbing, loose windings, etc.

Anyone have any idea why a speaker that looks fine and seems fine mechanically, sounds distorted?

Trevorus · #2 01-04-2007, 02:24 PM

The surround may have had a crack in it. They can be all but invisible until you move the cone.

BillyB_from_LZ · #3 01-05-2007, 10:14 AM

After I got home last night, I checked everything again. The surround, cone, dustcap and spider are all undamaged.

Anyone have any thoughts?

billfitzmaurice · #4 01-05-2007, 11:23 AM

Did the same symptoms occur with a different source? Did the same source cause the symptoms with a different speaker? If you have the volume control of your bass very low and the amp set normal, for instance, the system signal to noise ratio can be quite poor. For that reason you usually turn the volume down starting at the last volume control in the chain.

BillyB_from_LZ · #5 01-05-2007, 11:58 AM

I used one bass (passive) and one amplifier (Walkabout) but two different speakers sharing the same 1x10 cabinet (one at a time of course).

The volume was controlled by the master volume of the amp with the bass full up and the gain on the amp's input adjusted to a clean tone.

The non-Hartke was clean and free from distortion, the Hartke wasn't. That's why it's so perplexing!

Scutterflux · #6 01-05-2007, 12:35 PM

I think I might be going throught the same thing with a pair of EA cxl-112's. One has a distortion at lower volumes, and can be drowned out, the other is fine. It seems like the distortion is about the same volume no matter what volume I play at. There's no rub, no evidence of damage, I'm not taking it apart though. If you figure it out I'd like to hear your advise, otherwise I'll be getting a replacement.

BillyB_from_LZ · #7 01-05-2007, 12:42 PM

I know what sound you're describing, but this is different.

I guess I should have said that the sound is distorted no matter the volume. It's like it's a special overdrive speaker.

My other thought is that the magnet might be weak or something but the frame sure attracts my steel tools...

62bass · #8 01-05-2007, 04:38 PM

Quote:

Originally Posted by BillyB_from_LZ

I know what sound you're describing, but this is different.

I guess I should have said that the sound is distorted no matter the volume. It's like it's a special overdrive speaker.

My other thought is that the magnet might be weak or something but the frame sure attracts my steel tools...

Well, obviously the speaker doesn't work correctly. If you can't get it reconed you'll have to replace it.

Who knows why it distorts. Sounds to me like the voice coil is rubbing. I've had that happen with speakers before. The voice coil did not seem to be rubbing when I moved the cone by hand. But it was when under power. If you played through it for any length of time it would quit completely.

But it doesn't matter. Just get it fixed or replace it.

BillyB_from_LZ · #9 01-05-2007, 05:19 PM

Quote:

Originally Posted by 62bass

...

But it doesn't matter. Just get it fixed or replace it.

But that's no fun!

BTW, I also wrote to Ted Weber (WeberVST) and he thought that there might be something in the gap. I'll have to look into that (literally).

Seems as though it's quickly becoming landfill fodder

62bass · #10 01-05-2007, 05:31 PM

But that's no fun!
/QUOTE]

Sorry. I was being practical.

Sounds like it's ready for the landfill already.

BillyB_from_LZ · #11 01-05-2007, 05:52 PM

Quote:

Originally Posted by 62bass

...Sorry. I was being practical.
...

I know. I just hate to give up so easily... I've taken a couple speakers (a (different) 10 and an 18) with sheared-off magnets (deemed "unrepairable" by the experts), carefully removed the cone/voicecoil assembly, reattached the magnet to the frame (using a special jig that I built in the process) and reinstalled the "motor" bringing them back to life.

spiritbass · #12 01-05-2007, 08:10 PM

Creased cones sound bad at all levels, been there

...

Ken

Scutterflux · #13 01-07-2007, 11:14 AM

You might already know this, but fold some tape sticky side out over a buisness card and run that through the magnet to clean it up nice

BillyB_from_LZ · #14 01-07-2007, 12:13 PM

Thanks! I'll give it a try.

**IvanMike** · #15 01-07-2007, 01:08 PM

i'm leaning towards a bit of something in the gap, perhaps solder or other manufacturing material that got in there when it was made. one time i sent a driver to eden for a recone and got back a perfectly good looking replacement that distorted liek your hartke. they made good and sent me a new one, and stated that the likley culprit was as i described.

RockBobby · #16 01-07-2007, 04:27 PM

Quote:

Originally Posted by BillyB_from_LZ

Thanks! I'll give it a try.

You already cut the spider

Anyway, when I brought my speaks to New England Speaker, they cut off the dustcap and then used a bent cardboard to reform the VC around the magnet (making sure it was round and concentric). I bought a Fender cab with 2-15s and did the push/9vbattery check. I plugged it in and it rubbed. Must be out of round.

Jerrold Tiers · #17 01-08-2007, 10:52 AM

Distortion a LOW volumes is often an air leak. They can sound like something between crossover notch and clipping.

Often not a problem with the actual speaker, but rather with the seal of the speaker to the cabinet.

Usually, you can, with some effort, find a particular spot that the noise comes from. You can often locate the leak with a piece of lightweight paper, or, if you are more curious than cautious, with a lighter flame...... I would advise being mighty careful with the latter, if you try that .

Low volumes is the key, where there is enough air movement and pressure to show up a leak, but not enough sound to drown it out.