Powerstage 700: How to protect speakers from damage

[J. Coolman]

I'm happy to be a new member to this forum. I've been playing guitar for 40+ years, and this is the first time I've ever had to consider such a drastic ratio of amp power to speaker cabinet power handling.

Is there an effective method to objectively determine the maximum volume level one can safely dial in on the Powerstage 700 without damaging the connected speakers?

I have a PS700 in my guitar rig, and just like most everyone else on earth, my speaker cabinet can handle fewer watts than the PS700 is capable of dispensing. To be exact, I'm feeding two 120w 2x12 cabs at 8ohms each, and I'm considering swapping one of the speakers in each of the 2x12s which would consequently reduce each cab's power handling to 50w. If the PS700 is capable of 350 per side at 8ohms, then I'd like to know a safe limit for the PS700's volume dial in this rig because I'd prefer to not blow my speakers.

To be upfront, I'm not interested in replacing my PS700 with a couple of PS170s or the like. I'm fine with having too much power on tap from a single unit, I just want to protect my speakers.

Looking forward to your input.

[devastone]

How loud do you play? What speaker are you going to use as a replacement? A 25W speaker? The power into the amp is shared by all the speakers, it's not set by the speaker with the lowest power rating. I would think that unless you are turning up to very uncomfortable levels you aren't going over 120W, probably not 50W but no guarantees (I could be wrong?). Maybe you can find a similar speaker tha's rated higher for the replacement? Just to be safe.

[J. Coolman]

How loud do you play? What speaker are you going to use as a replacement? A 25W speaker? The power into the amp is shared by all the speakers, it's not set by the speaker with the lowest power rating. I would think that unless you are turning up to very uncomfortable levels you aren't going over 120W, probably not 50W but no guarantees (I could be wrong?). Maybe you can find a similar speaker tha's rated higher for the replacement? Just to be safe.

Thanks for your reply. For my own tonal desires, I am replacing one of my two v30s (60w speakers) with a G12 Greenback (25w) in each cabinet. Whether I have a 50w cab or a 120w cab, it is susceptible to being overpowered by the PS700. I'm not interested in guessing what might or might not be too loud. I'm looking for a means to measure the wattage being delivered to each cab, a mathematical formula, or some other objective way to take the guesswork out of it. Given that my searches have landed me here asking this question, I doubt that there is a convenient way to do it.

[devastone]

There is a formula for cacluating power, P=I*R^2 (and substitutions based on ohms law), but it's hard to figure the exact power going to the speaker at any given moment.

[NegativeEase]

but it's hard to figure the exact power going to the speaker at any given moment.

Yeah, I was going to say this -I also doubt that rated 700W at 4ohms or 350 ohms at 8 ohms Solid state amp is presenting this to the actual speaker load.

Companies tend to be a little "Peaveyish" when it comes to lab rating optimism and ideal conditions.

but I think the amp is certainly capable of blowing up those 120W cabs to the TS point.

I wouldnt dial them past 1/2 way, and use my ears to listing to speaker performance... also consider a limiter pedal to kill the most likely risk -transient spikes asking the speaker to do something WAY outside the volume you are asking it for

[devastone]

And if you want a greenback-ish style speaker maybe look for a higher power version if you are concerned.

I was posting while drinking my first cup of coffee, so forgot to mention that since it's a SS amp the power output will be reduced as the load goes up from 4 ohms, so probably 350-ish are 8 ohms, and 175-ish at 16 ohms, and of course reduced by the "marketing factor". (Thanks NE) It is also most likely (I haven't looked at the manual) peak output, not average, so that reduces it again to ~70% of the rated number.

You are probably safer than you original thought but still should use caution if you are needing to crank it way up.

[NegativeEase]

And if you want a greenback-ish style speaker maybe look for a higher power version if you are concerned.

I was posting while drinking my first cup of coffee, so forgot to mention that since it's a SS amp the power output will be reduced as the load goes up from 4 ohms, so probably 350-ish are 8 ohms, and 175-ish at 16 ohms, and of course reduced by the "marketing factor". (Thanks NE) It is also most likely (I haven't looked at the manual) peak output, not average, so that reduces it again to ~70% of the rated number.

You are probably safer than you original thought but still should use caution if you are needing to crank it way up.

teamwork!

[jeremy]

i think youd be hard pressed to find an exact spot on the volume control that would be the "safe below this" line. you can usually hear when you are slamming a speaker too hard. if the volume control, and everything else, is linear and you are putting out 350w @ 8 ohms, then you wouldnt want to go above 1.5 on the volume control. is that actually true? i have no idea

[J. Coolman]

Thanks, everyone. You confirmed my suspicion that there is no easy or convenient way to determine the "safe range" on the volume dial. At the same time, I haven't heard any horror stories of PS700 users blowing speakers. I like NegativeEase's simple suggestion of listening to the speaker performance. I'm sure I'd notice if they start sounding like they're being overpowered. And maybe I should also consider a limiter as suggested.

[devastone]

Not sure what you're playing situation is, if you are playing in your house you're probably not getting anywhere near the 50W mark, that will shake the walls. If you are playing bigger stages or with a loud drummer you may be getting near that.

To Jeremy's point, output is rarely linear. but again, can't really pinpoint an output vs volume dial position.

The best people to ask about this are the engineers at Duncan that designed it, they will definitely have the most insight.

[NegativeEase]

I might add, I use Powerstage 170 to drive a single 2x12 120W V30 Cabinet -works well for when I bring extra cab for medium sized venues... for large venues I break out the 4x12/s and 100W tube heads

[J. Coolman]

I might add, I use Powerstage 170 to drive a single 2x12 120W V30 Cabinet -works well for when I bring extra cab for medium sized venues... for large venues I break out the 4x12/s and 100W tube heads

NegativeEase, what is the impedance of your 2x12 cabinet being driven by the PS-170? Do you notice any loss of headroom with it?

[NegativeEase]

NegativeEase, what is the impedance of your 2x12 cabinet being driven by the PS-170? Do you notice any loss of headroom with it?

8 ohms. no havent noticed any

[El Dunco]

And if you want a greenback-ish style speaker maybe look for a higher power version if you are concerned.

I was posting while drinking my first cup of coffee, so forgot to mention that since it's a SS amp the power output will be reduced as the load goes up from 4 ohms, so probably 350-ish are 8 ohms, and 175-ish at 16 ohms, and of course reduced by the "marketing factor". (Thanks NE) It is also most likely (I haven't looked at the manual) peak output, not average, so that reduces it again to ~70% of the rated number.

You are probably safer than you original thought but still should use caution if you are needing to crank it way up.

Not that I’m including the PS in this, it’s funny when they advertise car stereos and hi-fi systems as something nonsensical like 2000 WATTS! to make the revvheads go “wow!” But it’s blatantly misleading when you carefully read the specs.

[chadd]

You'll be fine. you can hear when the speakers start to stress and get additional distortion, don't go that far. Start low, work your way up to a comfortable level and you'll be fine