Stoopid amp question

bassduke49 · Post by **bassduke49** » Mon Aug 08, 2005 4:26 pm

OK, I'll confess. I'm quickly becoming an "expert" on Rick basses, thanks to all of your collective knowledge filtering through my little gray cells, but when it comes to amps, I'm stoooopid. I've got a problem, and I don't know if it's even a problem!?

I've got a Gallien Krueger 700RB15 combo amp ("bi amp" with 1 15" speaker and a high freq horn), and it's got plenty of power. More power, apparently, than the 15" woofer can handle. With volume setting close to half way up and the boost about half way up, the speaker "farts"; that's the best way I can describe it. Instead of a smooth big booming sound, it sounds like the worlds largest (and deepest) fart. I suppose the amp is overdriving the speaker, but you'd think the thing was made so that it couldn't.

Anyway, I suppose the easiest answer is to turn down the volume and mike the amp into the P.A., but my band doesn't play huge venues and that seems like overkill. Plus the drummer is the P.A. guy, and I'll bet he won't appreciate another complication. He has trouble enough mixing the vocals.

So, would getting an additional speaker (the combo has a "Speakon" connector to do so) add volume yet keep the speakers from overdriving?

Help me out here, guys.

charlyg · Post by **charlyg** » Mon Aug 08, 2005 4:38 pm

I'm a 10" sort of guy now so I can't help much, but back in the day, Grand Funk did a tune called "Inside Looking Out". Evidently that is the sound they were after cause the bass sounds like it's farting!

I will say that's a lot of watts for 1 speaker!

bassduke49 · Post by **bassduke49** » Mon Aug 08, 2005 4:50 pm

It's not really 700 watts, but I think it's rated at just under 400 somewhere.

revolver323 · Post by **revolver323** » Mon Aug 08, 2005 5:07 pm

Anytime you add an extension speaker, you'll get more coverage, which will give you an apparent increase in volume. Plus, most amps put out more wattage into lower ohms. If yours is rated at 300W, an extension should bump it up to the 400W range. That means you can run the master volume lower and still achieve the same volume level. Make sure ohmage matches, though. If your 15" is 8 ohms, your extension should also be 8 ohms. Finally, if you can convince the rest of the band to come down in volume onstage, running a line to the P.A. is a great idea. You need to have a comfortable sound level onstage, though. The worst thing I deal with is when more of me coming out of the P.A. than I do onstage.

incubus2432 · Post by **incubus2432** » Mon Aug 08, 2005 5:16 pm

^ what he said. Another side benefit is that with your amp "bumped" to putting out 400 watts (into 2 cabinets) it will be less power to that 15"....200 instead of the full 300. You'll be surprised in how full and strong your rig will sound with a 2x10 or another 1x15 added to the mix

.

lars · Post by **lars** » Mon Aug 08, 2005 10:21 pm

Every combo I have used delivers more power than the built-in speaker can handle.

grayk · Post by **grayk** » Mon Aug 08, 2005 10:59 pm

I dont know this amp but is there an input stage setting knob on it ? It sounds to me like the input stage is being overdriven. Some amps have a button for active/passive bass guitars or separate jack sockets. On a lot of amps you have to set the input so that it is comfortable and not overdriving at the point where you are playing at your hardest. I would check this out. I might be way off the mark but the symptoms you describe sound like too much input to me. If this is the case drop the level down at the input and bring your master volume up as it will have the effect of lowering the volume.

jnbass · Post by **jnbass** » Tue Aug 09, 2005 12:15 am

Paul-

the position of the vol control knob has little to do with how much power vs its rated maximum the amp is putting out. Even if the pot is linear (its not usually), the power output won't be.

Having said that, the amp may be clipping, thus sending the dreaded square wave to the speaker-which then sound like cr_p. Even a speaker rated at 500 watts will do this with a 50 watt amp.

If ya need more volume-get a bigger speaker (surface area). 2x10, 2x12 etc...

Of course I don't really play my g'tars.

leftyguitars · Post by **leftyguitars** » Tue Aug 09, 2005 1:44 am

If your speaker is "f*rting", the three most likely causes are,
1, Speaker is trying to draw more power from the amp than it can cope with (amp too powerful) and overloading (Peaks can blow the speaker).
2, Input gain is too high and the signal is clipping, this is major bad news and can damage the output stages on the amp and will blow the speaker.
3, The speaker cone is torn or damaged.

If you use an extension speaker you don't have to balance the impedance (ohmage) as long as the total impedance is not less than the recommended minimum impedance for your amp, for solid state amps. Or is more than the minimun impedance for valve (tube) amps. Usually it is printed next to the speaker out jack what the impedance should be. If you use the speaker out jack on the amp the speakers will be in parallel. The following calculations might help... 8ohm + 8ohm = 4ohm total, 8 ohm + 4 ohm = 2.666 ohm, 4 ohm + 16 ohm = 3.2 ohm.
Also the more (or bigger) speakers that you use the louder you will sound because you are moving more air. High wattage small speakers move more air by having a greater "forward/backward" movement, but this isn't ideal because the coils can overheat.

rictified · Post by **rictified** » Tue Aug 09, 2005 3:11 am

I would balance the impedance especially with a tube amp which this isn't and it is more safe to to run a tube amp at less than the correct impedance not more, they are opposite of SS amps in this regard. I used to think that also until I did some reading around. Turn the master volume low and set your preamp gain so it sounds clean as hard as you can play your bass, that eliminates #2. Then turn up the master, distortion has a different sound than mechanical rubbing (blown speaker) a blown speaker will rapidly get worse, power amp distortion shouldn't. Try unhooking the internal speaker and plugging in one of your PA bottoms, and see if you still get the sound, that way you can determine whether it's the speaker or you are just clipping the output (If the speaker's making that noise it's most likely already on it's way out)

If it's a true bi-amp try it in mono mode, if it disappears you were clipping the power amp as you get much more power in mono mode of a stereo amp. Bi-amping is pretty much useless for a bass anyway as 90% of your power is used by the bottom.

leftyguitars · Post by **leftyguitars** » Tue Aug 09, 2005 3:28 am

Oops, your right Bob, I got it the wrong way round!!! Solid state can be over but not under (but if they are over you will lose volume) and tubes can be under but not over (but ideally the same), my mistake! Sorry.

david_schwab · Post by **david_schwab** » Tue Aug 09, 2005 10:00 am

I used to own a GK-800RB bi-amped rig. Although most of your signal is in the low end, you do get benefits from bi-amping. The low frequency amp doesn't have to reproduce any high frequencies, and vice versa. This makes them run more efficient, and you get a cleaner signal. When bi-amping, two 100 watt power amps put out more than a 200 watt full range amp.

In the case of the 800RB, it had a much more powerful power amp for the low end... 300W with a 100W high frequency power amp. I used a 2X12 cab for the highs, and 1X18 for the lows. This was before anyone but Ampeg was using 10's (old Fender Bassmans not withstanding).

You can switch the amp from bi-amp to full range, and really hear a difference in tone. It's bigger and cleaner in bi-amp mode.

rictified · Post by **rictified** » Tue Aug 09, 2005 11:14 am

I bi-amped last week full range with two SVT set ups, very clean and very loud, haha!

charlyg · Post by **charlyg** » Tue Aug 09, 2005 11:23 am

Bob - Wake the dead comes to mind!

rictified · Post by **rictified** » Tue Aug 09, 2005 12:47 pm

Actually it was an outside rock a billy gig with an upright, it just sounded really nice, full and smooth I didn't bring them to earthquake anyone, but I brought a Ric 4001 with RW's on it just to see what it sounded like and it sounded like I would imagine half the people here would like their Rics to sound, Squire to a T. The old SVT cabs have a better high frequency response than the new ones do. This set up would have definitely convinced the doubters here (if their eyes were closed).