Audio power meters

[shinychrome0]

I'm looking for something to monitor the wattage that my amp is sending to my speakers.  Its very hard to find anything that's suitable, and doesn't have a bunch of extra features.  I play a digital Line 6 preamp into a 300 watt tech 21 amp, which powers 90 watts of speakers.  So i would really like to be able to tell how much power the speakers are getting.  I would love to be able to turn up more, but i'm afraid to blow my speakers.  Tone tubby's aren't cheap, and neither are celestion century's.  I've seen a few units like the radio shack APM units from the 70's, but is there anything in current production that does the same thing?  I prefer buying new rather than used for stuff like this.

[J M Fahey]

You are playing with fire.
Anyway, a meter won't help you much, unless you put it on a mic stand, one foot in front of your eyes, and have your eyes glued to it all night long.
Suppose you set your system to deliver, say, 70W RMS.
Playing has dynamics , one chord might deliver 30W, the next one 120W.
*If* you play with, say, a 60 or 80W amplifier it's different, because it clips (limiting power) at it's rated maximum output power.
Your best bet would be to introduce a good limiter (such as some DBX or similar Pro quality unit) into your signal path, and set it to limit at, say, 70W, which it will do all day long, automatically, without your intervention.
Or, you could use a 60/70 W power unit.
Please post links to your power amp and speakers, I might suggest you some other solution.

[shinychrome0]

http://www.tech21nyc.com/archive/powerengine400.html  - i have the 300 watt mono version of this

I have one of each of these in my 212 cabinet
http://professional.celestion.com/guitar/products/classic/spec.asp?ID=2  - rated 60 watts
http://www.hempcone.com/pro/store.html - its the 12"  ceramic tone tubby.  rated 50 watts

I would be using the meter to set the max output power somewhere around 90 to 100 watts (hopefully less, but i can't tell without a meter) so that most of my playing will be below the rating of the speakers, but can never exceed it.    I understand your point about the big swing in power, but i want to make sure my MAX volume does not exceed 100 watts at any time.

[bry melvin]

what impedance are your speakers?  Assuming 8 ohms?  your amp puts out 300 watts at 4 ohms with the speakers parallel.  It would put out 200 watts with 8 ohm load. )according to specs)

For starts; Particularly if your speakers are 8 ohms I would run them in series.  with a 16 ohm load  your amp will produce less watts.

If you have 16 ohm versions and run in series It would beless likely that your amp power would overload the speakers.

Generally increasing speaker impedance isn't going to hurt an SS amp, just reduce power available. (Amp will clip sooner too.)

[shinychrome0]

They are 16 ohm version, which according to tech 21 would make the amp have a max output of 90 watts.  But it would clip at that, and don't clipping amplifiers kill speakers faster than anything?

[bry melvin]

The amp will clip when it's nearing max power no matter what....Just using at 32 ohms your not likely to blow the speakers.

If you want high volume and clean...your kind of using the wrong kind of speakers to start with.

Those are guitar speakers designed TO start breaking up long before getting to their power rating. Although adding MORE of the same speakers will give you higher volume at the same power level.

A power meter to me is not a solution...I've spent several thousand hours watching meters and indicators. They are good for telling you what just broke, not often preventing it.

Simplest solution...match the speaker power >= amp power output. 32 ohm setup is how you would do that with your speakers.

as far as clipping and speakers...ALL guitar distortion IS clipping Don't run the amp that high? Or get more speakers to match speakers/amp

SO roughly in order of cost

solution 1 run 32 ohm load   speakers ratings and amp then match. Just don't run the amp maxed out. If volume is inadequate without clipping see solution 3.
solution 2 run smaller power amp
solution 3 add speakers such that power amp and speaker ratings match. This will give more apparent volume. EX 4 speakers is louder than 2 at same amp settings. (idea behind the "full stack")
solution 4 add speaker management system/limiting...way overkill for two speakers...cheaper to add another pair

BTW if you're playing bass not guitar forget all the above and get a set of speakers that work for bass You'll eventually kill those with bass. 90 watts of speakers for playing out today just won't do. Maybe try a set of Carvin PS12s or something similar if your budget is tight.(300 watt bass/pa 12 inch speakers)

If you are after really clean Like playing steel etc Might want to look at PA/Bass Keyboard amp speakers too.

Additionally if you're using the Line 6 processing amp models cabinet models etc you probably SHOULD be using PA type speakers as guitar type speakers don't work that well with modeling...they are meant to change the sound (breakup etc)

[shinychrome0]

If you want high volume and clean...your kind of using the wrong kind of speakers to start with.

-I never said i was going for clean.  but power amp distortion sounds like absolute crap.  Not quite the distortion i want.


Those are guitar speakers designed TO start breaking up long before getting to their power rating. Although adding MORE of the same speakers will give you higher volume at the same power level.

-I would love to add more speakers, but unfortunately all my money is currently being pooled towards a new classical guitar.


A power meter to me is not a solution...I've spent several thousand hours watching meters and indicators. They are good for telling you what just broke, not often preventing it.

-I don't really see it as protection.  I just want to use it to find out how much volume i can safely get out of my current setup






Additionally if you're using the Line 6 processing amp models cabinet models etc you probably SHOULD be using PA type speakers as guitar type speakers don't work that well with modeling...they are meant to change the sound (breakup etc)
-this i disagree on.  I have always gotten a much better sound out of the amp models by leaving the speaker simulations turned off and running through these speakers. But thats a whole other thread on its own. lol.


-Part of the reason i do not want to rewire my cabinet for a 32 ohm load is that i often use only one speaker (they are connected to separate inputs on the back) especially when i am recording.  I will only plug the amp into the one i am currently tracking so that i can hear what is going on more accurately, and so the mic only picks up that one speaker.  So i would love to keep it wired the way it is now. 

So aside from all the advantages/disadvanteages of a power meter, back to the original question.  Does any company currently produce one or should i just shop used?

[bry melvin]

cheapest may very well be a kit:

power led meter kit:

http://store.qkits.com/moreinfo.cfm/K4307


I found this meter which supposedly will go to 300 watts:
http://www.aqdi.com/powermeter.htm

dbx speaker management:

http://pro-audio.musiciansfriend.com/product/dbx-DriveRack-PA-Complete-Loudspeaker-Management-System?sku=620494

Carvin speaker management:
http://www.carvinguitars.com/products/single.php?product=XD88&cid=61

[J M Fahey]

Hi shiny.
I think you are under the wrong (yet very common) impression that you can *set* your amp to a given power level (say 70W) and it will not surpass that.
That is not so. What you set is *gain*, not power, and any signal louder than expected will push those speakers beyond their limits.
The only solutions are clipping (usually by using a smaller power amp or mismatching speaker load, as suggested above) or, as I suggested before, using a good compressor/limiter.

[Enzo]

You may be right JM, an alternative might be that he doesn;t know how much power is being delivered for a given loudness.   For example, "Gee, this is pretty loud."  But is it 12 watts or 50?  I guess just to orient myself I might monitor power levels to get an idea how loud the amp can get before crossing into too much power for the speakers.   That is a real oversimplification of the system, but maybe that is his plan.  Once you know how loud 90 watts is, then you can try to keep the amp less loud than that.  Of course that assumes your "hearing memory" is up to that task.

[shinychrome0]

I went ahead and bought one of those radio shack meters.  It seemed like the cheapest and quickest way, and the thing practically looks brand new.  And yes enzo, you are correct.  I was mainly just looking for a way to find out how loud max power is for my cabinet.  The short answer: way louder than i will ever turn it.  The speakers i have are both extremely sensitive, and i was pleased with what i saw.  With heavy, bassy, compressed power chords at an excrutiating volume, i was barely lighting up the 15 watt peak bulb, and the RMS display showed only about 10 watts.  So it was 50 dollars well spent to know that i can get as loud as i need to in band rehersals (where we don't have equipment to mic the amps) without fear of blowing anything.  My guess is that based on how loud i usually kept it before (which was usually when i could visibly see the cone start to move)  it was probably only about 5-7 watts peak.  And no one could hear me.  So i guess its good that i didn't spend extra money on a limter or something since i'm not coming anywhere near to peak power anyway.  I'll be lucky if i ever touch the 50 watt bulb with a really delay heavy screaming lead part or something.