B450 Crackle

pickettj · #1 09-07-2011, 11:28 AM

I'm starting to get a little concerned about my amp. I have an Acoustic B450 amp that I have been playing with and I do NOT clip the amp at all. Today when I plugged in to it and plucked a string, the speakers made a crackle. It doesn't happen every time I play a note, only on the low stuff and only occasionally. It doesn't seem normal and I need some expert input as to what the problem is and what I can do to fix it, even if it means replacing the speakers.

fenderhutz · #2 09-07-2011, 11:33 AM

Without hearing it, it sounds like a possible loose solder joint. Low note vibration is causing the issue.

RickenBoogie · #3 09-07-2011, 11:34 AM

It may be , especially if you're boosting the lows, that the speakers cannot handle what you're putting into them. This is a combo amp? The internal speakers will usually give up, and max out at lower frequencies, and the only thing you can do is cut the lows, and/or volume.

pickettj · #4 09-07-2011, 11:37 AM

It's not distortion. It's a definite crackle. Best way I can describe it is the sound olden day LPs sounded. That background crackle. I think if I drop the lows then it'll probably clean it up, it just bothers me. It sounded so clean and clear last time we played. We play loud, but the volume stays around 1/2 on the amp and the gain is always between 10-15%. And yes, the B450 is a combo amp.

pickettj · #5 09-07-2011, 11:38 AM

I suppose it could also be compared to the crackle of a loose input jack on a guitar, but it's not that severe and it can't be replicated by playing with the jacks. If I'm standing/sitting motionless (aside from playing the bass, of course), it still makes the sound.

fenderhutz · #6 09-07-2011, 11:41 AM

Just have the head and the cab with the powered on without an instrument hooked up. I know this sounds crazy, but take your fist and pound around the top of the amp. Not overly hard of course and see if the crackle happens. If it does, something is loose.

pickettj · #7 09-07-2011, 11:43 AM

not a bit. sounds like something is rattling in there, but no crackle.

pickettj · #8 09-07-2011, 11:47 AM

I think I found the source...The bottom speaker sounds like it's got a windy fart when I play it. I think I may have a blown speaker. Just doesn't make any sense because I never have it cranked. I would never have guessed that the speakers would give out with the volume staying around half.

Bass_Pounder · #9 09-07-2011, 11:53 AM

Quote:

Originally Posted by pickettj

I think I found the source...The bottom speaker sounds like it's got a windy fart when I play it. I think I may have a blown speaker. Just doesn't make any sense because I never have it cranked. I would never have guessed that the speakers would give out with the volume staying around half.

A) The position of the volume knob has NO relationship to the amount of output (1/2 way up does not mean 1/2 power).

B) Wattage ratings for speakers mean nothing. Depending on how you EQ, most speakers hit their mechanical limits WAY before the "wattage rating".

pickettj · #10 09-07-2011, 11:54 AM

Quote:

Originally Posted by Bass_Pounder

A) The position of the volume knob has NO relationship to the amount of output (1/2 way up does not mean 1/2 power).

B) Wattage ratings for speakers mean nothing. Depending on how you EQ, most speakers hit their mechanical limits WAY before the "wattage rating".

Well, after turning it up and listening closely, the speaker is toast. Now to see if that warranty I paid dearly for was worth the money. Otherwise, I guess I'll be picking up a new speaker.

Bass_Pounder · #11 09-07-2011, 11:58 AM

Quote:

Originally Posted by pickettj

Well, after turning it up and listening closely, the speaker is toast. Now to see if that warranty I paid dearly for was worth the money. Otherwise, I guess I'll be picking up a new speaker.

You may want to open it up and do a visual inspection first.

Without hearing what your hearing, it still could be possible that there is a loose connection of the wires on that bottom speaker. Also, look to see that there are no wires close to the back of the speaker that could be vibrating against the moving cone.

For what it is worth, I have heard that getting replacements under warranty is pretty simple.

pickettj · #12 09-07-2011, 12:04 PM

I just talked to Guitar Center. I have to ship the amp for the claim. If I open the cabinet up (it would require a LOT of work) then it would void the warranty. I can't even remove the front screen without compromising the warranty. Hopefully there is a fast turn around. I'm going to see if I can see anything visually before I call to make the claim.

RickenBoogie · #13 09-07-2011, 01:38 PM

Yeah, combo amps, or heads with big cabs even, can be damaged quite easily when you use the low eq. More low end you add, the more volume you rob yourself of. Sounds like you need more speakers to do the job you want, so best of luck getting it sorted.

pickettj · #14 09-07-2011, 02:26 PM

Yeah, I've been looking at picking up a 15" and running both but I was worried about it sounding muddy. I'm hoping to replace this setup with a mark bass setup anyways. Maybe a cab with 2-10's and a 15 or 2-10's and a 12. I haven't really looked to see what is available since I can't afford it right now anyways.

Thanks for your help guys.

SurferJoe46 · #15 09-07-2011, 02:50 PM

If you take the front grill off it is easy. I had the same trouble and fixed it in a very short time.

The ONLY access to the drivers is through the grill. If you try it otherwise, you'll have to use a hammer to rip the cab apart. THAT - I am sure would void any warranty. No-one can tell if you take the grill off - it's held on with Velcro anyway.

And I've NEVER heard GC say that you have to ship the cab to Acoustic. If it is bad, GC will trade it in on spot for another one.

BUT - the B-450s have this same problem all the time and the factory repair is gonna be the same poor parts on the ends of the wires and you'll STILL have the potential of it becoming a bad connection.

It wasn't the speaker or a solder joint - it was a poor spring on the spade connections at the UPPER speaker. It made my lower speaker cut in and out according to the volume and amount of bass I used.

The lower speaker was going ON and OFF so fast that it seemed like a blown driver.

It wasn't. I originally thought it was loose screws - but it was the wire ends on the lugs. So - this pix set has the idea of a loose screw as the reason for this noise existing, but you need to go into the cab through the driver hole - the TOP one.

Taking the grill off is easy:::

The speakers are held in with Nut-Serts and the threaded portions won't strip in spite of someone saying they were just wood screws.

I soldered pigtails on the speakers and totally eliminated the future possibility of them ever coming loose again. But here's a pix of what you can expect once you take the UPPER speaker out:::

If you add much new wiring to the speaker lugs, then make sure that you staple the excess out of the way and so they cannot get to the back of the cones and make a new noise.

OK - I edited the original pixs to more-fit your circumstances.

pickettj · #16 09-07-2011, 03:53 PM

Well, I took the front off and plugged the amp back in to verify it was the bottom speaker and the noise stopped. I don't know if laying it down moved something out of the way or what but I'm just going to use it and see what happens...

SurferJoe46 · #17 09-07-2011, 05:06 PM

Yeah - I think you just had gravity on your side and the connex made a better contact.

It may return to bite you later. At least you have a hint at what's going on now and it prolly is the connections I mentioned - since a driver won't be affected by alignment with the earth's gravity field to be bad in one direction and good in another.

I hate things that seem to repair themselves.

5port · #18 09-07-2011, 05:09 PM

Wow could you get any more thorough than SurferJoe's example? What he said. I was going to suggest the same thing as the Acoustic 4X10 suffers the same malady. Turning the amp over to work on it only put the wires in a different position so it is only a temp fix. Some people just solder the lugs to the speaker. Add a star if you can solder.

pickettj · #19 09-07-2011, 06:54 PM

Quote:

Originally Posted by SurferJoe46

Yeah - I think you just had gravity on your side and the connex made a better contact.

It may return to bite you later. At least you have a hint at what's going on now and it prolly is the connections I mentioned - since a driver won't be affected by alignment with the earth's gravity field to be bad in one direction and good in another.

I hate things that seem to repair themselves.

Me too...now I have to explain to the warranty department why I don't need a repair...should've waited.

SurferJoe46 · #20 09-07-2011, 08:26 PM

Just tell them the noise went away - you'll call them if it returns later.

I tried to tell Acoustic that they use crappy spades and they just iggy'd me - so they can rot as far as I'm concerned.

I'm still keeping my gear and loving it :0 but I won't send it in if it ever gets to be a problem.

One thing - I bought the forever-n-ever GC-Pro Coverage on the stuff and it says in the clauses: "For ANY reason" - so that sounds good for my purposes.