A question about Acme B2

[AudioDwebe]

Hey guys, I need your expertise.

I recently took home the Low B2 and picked up a Hartke HA4000 (pushing 400 watts) locally to see what the difference would be between something with the recommended wattage versus something with a lot less (150 from the MB 150S I was first using).

Firstly, there was quite a difference in the sound. Don't know if it's the result of the wattage or the different amp makes, but I much preferred the Hartke over the GK.

So anyway, last night I was messing around with my bass and trying different sounds and volumes and trying to get a feel for the cab/amp combo. Everything sounded great, except when I tried to pop higher up on the G string with the treble turned up with the pup on the bridge only (don't know if just being on the bridge makes any difference). It was like static city. It sounded like a blown speaker.

But if I turned the treble down, it wouldn't happen.

It's like maxed treble equals bad; not maxed treble equals okay.

I had the volume on the amp at about 3/4, but its overall loudness wasn't too loud. I mean, I was just in my living room with no other instruments competing for sound.

I don't think the speaker is blown, but maybe just distressed at that frequency. But I really don't know.

So...

Is this the result of the amp not being up-to-snuff, or is it just one of those things the cabinet won't do well? Or is the cabinet bad and it needs to be returned (GC and about 21 days left on return policy).

Thanks in advance.

Mamoru

 

[will33]

Check the tweeter. IIRC, those are passed quite high and maybe don't contribute much to the overall sound unless you're snapping high notes with the treble cranked. If it's bad, perhaps Acme has a replacement diaphram for it.

If it's a GC purchase, I'd have them fix it, or use the return policy to exchange it for another one.

 

[KJung]

My experience with the Acme's is that slapping is kind of a no-no. You get the double wammy of those drivers hitting the plates on the massive slap spikes (even on the G string... remember, lots of subbass coming out of the higher strings also), and the Acme itself driving even some high powered amps into hard limiting clipping on those slap transients.

Great cabs, but even in the manual, it states that those who have very aggressive technique (of which slapping is an example) might do better with a different cab.

 

[Razman]

Sounds like you were clipping the input on the amp, not a blown speaker. A blown HF driver will be silent. My 800rb exhibits this with a hot input signal and when I'm really hammering some notes. Try turning the master volume down to confirm this, or lower your input level.

 

[KJung]

Sounds like you were clipping the input on the amp, not a blown speaker. A blown HF driver will be silent. My 800rb exhibits this with a hot input signal and when I'm really hammering some notes. Try turning the master volume down to confirm this, or lower your input level.

The Acme's are a different thing, but your general idea is correct. My guess is, he is hitting and blowing through the power amp limiter.

That is another thing with the Acme's. It isn't so much the absolute wattage (after a certain point), but rather the power management system. For example, my 4ohm Acme FullRange took my Markbass F500 to full, out and out, hitting the rails power amp distortion at moderate volumes when digging in (and this is a head that drives a typical 4ohm 212 to ear splitting volume with no issues). On the other hand, my Streamliner900, while regularly hitting the 'power management' indicator light (which I've never had come on with any other cab other than an 8ohm fEARful driven hard) sounded beautiful all the way to the limits of the FullRange.

These cabs are just a bit of a different beast. If you know what you are doing, have some external hi passing (in some cases), controlled technique, and enough power, they are quite something.

 

[BassmanPaul]

It is also possible that the contacts on the protection lamp have become a little corroded. Is your B2 Series 1, aluminium strapping, or series 2 with the black strapping?

The protection lamp is a standard auto tail lamp that can be purchased at an auto supply house. I would try replacing it.

 

[AudioDwebe]

Check the tweeter. IIRC, those are passed quite high and maybe don't contribute much to the overall sound unless you're snapping high notes with the treble cranked. If it's bad, perhaps Acme has a replacement diaphram for it.

If it's a GC purchase, I'd have them fix it, or use the return policy to exchange it for another one.

The sound only happens with the treble cranked and popping. I'm guessing it's not the tweeter, itself.

I'm not entirely sure how to go about testing it out, though. In all my years in audio, I've only had one tweeter go out and with that, the volume didn't make a difference, but rather it was a certain frequency.

So that's why I was guessing it wasn't the speaker, itself.

My experience with the Acme's is that slapping is kind of a no-no. You get the double wammy of those drivers hitting the plates on the massive slap spikes (even on the G string... remember, lots of subbass coming out of the higher strings also), and the Acme itself driving even some high powered amps into hard limiting clipping on those slap transients.

Great cabs, but even in the manual, it states that those who have very aggressive technique (of which slapping is an example) might do better with a different cab.

Yep, that's why I was asking if it was the limitation of the cabinet design. I guess the best thing would be to quit acting like a rock star and tone it down a bit?

Sounds like you were clipping the input on the amp, not a blown speaker. A blown HF driver will be silent. My 800rb exhibits this with a hot input signal and when I'm really hammering some notes. Try turning the master volume down to confirm this, or lower your input level.

Maybe it's the midrange driver? I just assumed it was the "tweeter" since it happens when I crank the treble. It could very well be the mid driver.

But then, back to the "it only happens when I crank the treble and turn the volume up" scenario, which leads me to believe it's the limitation of the amp rather than the cabinet.

It is also possible that the contacts on the protection lamp have become a little corroded. Is your B2 Series 1, aluminium strapping, or series 2 with the black strapping?

The protection lamp is a standard auto tail lamp that can be purchased at an auto supply house. I would try replacing it.

It's the Series II. Do I just remove the front grill to get to the light?


Thanks all for your quick responses. I really appreciate it.

I actually can't wait to get home to make some more noise out of the Acme. I'm really diggin' the sound from that thing.

 

[BassmanPaul]

You remove the grille and the bottom driver to access the crossover and thus the lamp. Please be careful, it's so easy to slip and run your screw driver through the surround, been there, done that!

Being a Series 2, your cab might possibly have the electronic fuse and how that's installed is beyond my experience.