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175W amp & 300W cabinet, too underpowered?

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M

mst3k

Jul 17, 2008
30
0
Charlottesville
#1
Hi all,

I have a Genz-Benz head (the Shuttle 3.0) that is 300W @ 4ohms and 175W @ 8ohms and an Aguilar GS112 that is rated as 300W @ 8ohms. My friend (who also plays bass) is telling me this is a bad arrangement, and that I'm not giving enough power to the cabinet (with possible detrimental effects). I'm saying it's fine, and for my current purposes (small rehearsals with guitar & drums) I'm not trying to drive the setup too hard. Who's right?

I've done some looking around, and it seems to be that it's a fine setup as long as I don't drive the amp to its limits to get more volume. Should I be looking into getting a more powerful amp?

Thanks, and sorry for what has to be a question that gets asked all the time.
 
#2
No, you'll be fine. Keep an eye out for a deal on another GS112, but you'll be OK with it the way it is - no detrimental effects.

If you find it wimpy even with two GS112s, then you can get something with more power. That's what I would do, anyway.
 
#3
Jaco who? said:
No, you'll be fine. Keep an eye out for a deal on another GS112, but you'll be OK with it the way it is - no detrimental effects.

If you find it wimpy even with two GS112s, then you can get something with more power. That's what I would do, anyway.
Click to expand...

It's fine, and won't hurt anything. As for "the sound" any cab is going to have an "optimum" range. Think of hooking a pocket transistor radio up to a set of JBL 100's. Sounds like crap, not that either item isn't doing what it's meant to. What I mean is that the cab may reach a close to perfect reproduction of the sound at one level (or range of levels)where the amp doesn't hit its range until another. Usually you need lab instruments to actually hear this if the equipment is close. Kind of like putting a single barrell side draft carburator on a blown hemi V8 if you don't mind the mixed metaphores:rollno:
 
#4
mst3k said:
My friend (who also plays bass) is telling me this is a bad arrangement, and that I'm not giving enough power to the cabinet (with possible detrimental effects).
Click to expand...
He's just repeating an old, well-worn myth.
mst3k said:
I've done some looking around, and it seems to be that it's a fine setup as long as I don't drive the amp to its limits to get more volume.
Click to expand...
That's correct. :)
mst3k said:
Should I be looking into getting a more powerful amp?
Click to expand...
If you need more "loudness" than you've got now, then a larger amp might be in order, but remember that watts alone do not equal loudness. You'll get the best results by having not only adequate wattage, but also a large and efficient speaker cab or two, and EQ'ing your rig to use that wattage best by cutting some of the lows back a bit.
 
#5
No such thing as under powering a cab... It's just inexperienced players trying to push their amps too hard to achieve more volume, causing them to clip the power amp, which will blow speakers in a heart beat if you're not careful. If you're not pushing it beyond it's limits, then you'll be fine.
 
#6
RFord04 said:
No such thing as under powering a cab... It's just inexperienced players trying to push their amps too hard to achieve more volume, causing them to clip the power amp, which will blow speakers in a heart beat if you're not careful. If you're not pushing it beyond it's limits, then you'll be fine.
Click to expand...

+1

Nothing else to say here.
 
#7
RFord04 said:
No such thing as under powering a cab... It's just inexperienced players trying to push their amps too hard to achieve more volume, causing them to clip the power amp, which will blow tweeters in a heart beat if you're not careful. If you're not pushing it beyond it's limits, then you'll be fine.
Click to expand...

+2, now that I fixed it for ya. ;)
 
#8
Careful there, that advice is right on the fence between truth and myth.

The only thing that blows speakers in that scenario is pumping too much power into them. Sometimes that can happen while an amp is clipping, as an amp can put out a lot more than its rated power while clipping. But the clipping itself does not do any damage. That part is the myth.
 
#10
anytime the topic of underpowering comes up, just think of a classic svt stack.

300w tube head, 800-1600w cabinet.
by the naysayer's standards, thats a no-no but its worked for so many and will ore than likely forever remain as the stack of choice among many bassists, despite the power discrepancy.
 
#12
bongomania said:
Careful there, that advice is right on the fence between truth and myth.

The only thing that blows speakers in that scenario is pumping too much power into them. Sometimes that can happen while an amp is clipping, as an amp can put out a lot more than its rated power while clipping. But the clipping itself does not do any damage. That part is the myth.
Click to expand...

True, Jimmy, but like Bongo said, oh, I give up , man.
 
#14
ryognbass said:
anytime the topic of underpowering comes up, just think of a classic svt stack.

300w tube head, 800-1600w cabinet.
by the naysayer's standards, thats a no-no but its worked for so many and will ore than likely forever remain as the stack of choice among many bassists, despite the power discrepancy.
Click to expand...

This is true and not true. The 300W head powering a big cab is not really a problem as far as "breakage"goes. Think of it as having a Honda Accord on the Indy 500 track. Sure, the track can handle cars going 250 mph, and the car is only capable of 120 mph. Not going to hurt either.

The cabinet is pretty much, electrically, just a "load" in other words a big resistor. Go back to Watts Law, power (Watts)= IxE (current times voltage). You have a cab that is capable of handling 800 watts, that means that it can handle any combination of current and voltage that doesn't excede 800 watts according to the formula. Now the impedence of the cab is 4-8 ohms, where does that come in? We back track to Ohms Law which states E (voltage or electromotive force) = IxR (current-amps x resistance-impedance in an ac circuit). If you have any two values in anyone of these formulas you can solve the other. Resistance or impedence is usually the non variable in this problem. And amps, for the most part put out small voltages, so this is controlable.

Going back to the start, the cab is a static resistance (for the most part, ...its impedence will alter negligably with frequency of the voltage being inputed).

Since the impedance (have I spelled that word three ways yet?) remains the same, you are left with E/I=8 ohms (or 4 or whatever).

Where things get tricky is how effecient the cabinet is. In other words can it reproduce the same frequencies at say 1W as it can at 300W? No, no one has invented a speaker that can so far. So you end up with a cabinet that is capable of producing an efficient reproduction from a low to a high wattage. Say 30-watts to say 250watts, under that and the speaker insn't being pushed hard enough to reach its efficient range, above that and it is excedeing its effiecient range.

When it is being under worked, it typically is dealing with a low voltage-Contro this with the Master (the same resistance and therefore a higher current). Push the volume to 11 and you are dealing with the opposite.

Are you confused? I am.
 
#15
Well that last post definitely confused me, but I guess the gist of the thread is that I'm fine as long as I don't crank the amp to its limit and drive it at that level continuously. :)

Thanks for the help everyone. I'll save myself the money and buy something else! :D
 
#17
I'm running pretty much the same rig as you. Shuttle 3.0, Aguilar GS112, but I also have a Schroeder Mini12L as well. I can tell you that adding the second 12" made a huge difference in both the volume and the amount of low end.

I haven't had the chance to gig yet but I can't really see needing anything more than this for just stage volume. I'd recommend adding another cab before upgrading the amp.
 
#18
Sheldon681 said:
I'm running pretty much the same rig as you. Shuttle 3.0, Aguilar GS112, but I also have a Schroeder Mini12L as well. I can tell you that adding the second 12" made a huge difference in both the volume and the amount of low end.

I haven't had the chance to gig yet but I can't really see needing anything more than this for just stage volume. I'd recommend adding another cab before upgrading the amp.
Click to expand...
+1 to that. I'd get an exact match myself, but there's definitely more for you to gain by adding a cab than getting a higher wattage head. I play pro in some pretty big venues and the Shuttle 3.0 + 8 ohm 112 would be all the rig I'd ever need. Of course, it wouldn't be all the rig I WANTED, but if I added another 112 it would probably be close to it. 300w into a 212 rig a lot of power.

But yeah, tell your friend to put 32 oz of water in a 16 oz cup. That's what happens when you believe in this underpowering cabs nonsense...you start thinking small containers can handle way more than they can. I've been underpowering big cabs since I started playing pro and I haven't blown a speaker in over 30 years.
 
#19
JimmyM said:
I've been underpowering big cabs since I started playing pro and I haven't blown a speaker in over 30 years.
Click to expand...

In 30 years the only speakers I've blown were with amps rated at less or equal to the cab I used with them.

But...that isn't because they were underpowered. All the speakers I've blown were actually overpowered by amps rated lower than the cabs because the amps were pushed too hard and at times were putting out more than their rated power.

Generally I agree with you and for most folks it's safer to have amps rated lower than the cabs. I prefer higher wattage and being smart with my volume because I don't like to push either the amp or my speakers very hard.
 
#20
Thanks for all the replies!

A few folks have mentioned getting another cabinet in addition to the GS112. I don't have the money at the moment, but I'm curious as to how such an arrangement works.

I'm confused about how the second cabinet's power requirements come into play. If I have two cabinets at 300W @ 8ohms and the single head I have now, how does that head put out enough power? What's the difference between one and two cabinets -- if I can power two cabinets with one head, why can't I give more power to a single cabinet?

(You can tell that I don't know much about this stuff. :))
 
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