Power Amp for Passive Studio Monitors?

PianoMan

Silver Supporting Member
Messages
1,137
I just got myself a pair of Zaph Audio SR71s (link) for a home studio setup , and now I'm looking for a power amp. I'm fairly new to this side of things however, and I can't find much information out there on what I need for power. From what I can tell from the specs (posted below), I want something that puts out 25-120 watts at 8 ohms. Anyone have any recommendations on what a good choice would be? Budget would be $250-300. For the record, I don't mind buying used.

ZA-SR71 Specifications:

Frequency response: 44 Hz – 20+ kHz
Recommended amplification: 25 W – 150 W per channel
Long term power handling: 80 W
Short term power handling: 250 W
Crossover point: 1.75 kHz (1,750 Hz)
System sensitivity: 85 dB in-box including BSC
Nominal impedance: 8 ohms
15.4” Tall x 9.1” Wide x 11” Deep
0.5 cubic foot (14 liter) bass reflex
 

Rex Anderson

Member
Messages
5,414
You want at least 150 watts because they can handle that much (250 watt short term peaks). Most blown speakers are due to not enough power which causes the amp to clip (creating square waves).

85 dB sensitivity is not high, thus you need more power to drive them louder. Headroom (more power) is safety.

A quick check on sweetwater.com showed these:

QSC GX3 and Crown XLS 1000, both selling for $299 new.
 

PianoMan

Silver Supporting Member
Messages
1,137
Thanks for that. I'm a little confused on one thing you said though. The QSC advertises 300W per channel, but the specs say I'm not supposed to go beyond 250 watts for short periods of time? Does that wattage get split between the two speakers, or am I just not understanding something?
 

LSchefman

Member
Messages
13,432
You can run a more powerful amp than your speakers are rated, if you make sure not to crank the amp all the way (which would probably be so loud there would be more to worry about than your monitors!).

I don't know what your budget is; I've always believed in getting very high quality amplification to passive monitors.

It's hard to go wrong with the Bryston power amps, though they're very expensive. I used to power B&W monitors with a Krell amp with balanced inputs in my old studio, and the sound was fabulous, but again, it's very pricey.

My feeling is that powered monitors have the advantage of having their amplifiers tailored to their limitations and strengths, meaning the amps can be cheaper. Whereas, separate passive speakers simply need great sounding amplification because you're not getting a synergistically designed systems.

An advantage to passive monitoring with a great amp is that the amp isn't being constantly vibrated by being inside the speaker cabinet. How much difference this makes in practice, of course, I can't say.

I can certainly say that Crown amplifiers have always been a studio standard.
 

Rex Anderson

Member
Messages
5,414
You will likely never approach using 250-300 watts. The difference between 250 and 300 watts may sound like a lot, but it's only 50 watts.

You have to double power to gain 3 dB (500-600 watts!) and it take 10 dB to sound twice as loud.

Don't worry about having a few extra watts of headroom to avoid clipping.

I would venture a guess that if you get even close to clipping the amp or damaging a speaker, your ears will be in pain.

But you know, I think I looked at power amps for PA purposes, not studio monitors. Those amps may be too noisy for your application.

In your price range, you should look at used hi-fi power amps like NAD, Adcom, Rotel etc. Do you have a high end hi-fi store near you that sells used gear? Good place to look.

Bryston amps are awesome, but even a used 2B or 3B will be more than you want to spend.

Let me think on this a bit longer-I'll get back to you!
 

PianoMan

Silver Supporting Member
Messages
1,137
The closest hi-fi store I know of is several hours drive away, but I only know of it because it's right by a job site my employer had me at for a while. I'll look around and look forward to your answer. Thanks for the help so far all!
 

vashuba

Silver Supporting Member
Messages
1,764
Bump-
Would you go with a crest audio la 901 or hafler2400pro?
 
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