Power amp/speaker situation Wattage, suggestions

[King Tone]

Hi Folks,

I have been using the matrix gt800fx power amp with my axe fx 2 for awhile and I am running into some issues. I believe it may be just too much power.
I ran it for years with my 2x12 port city which had 2 celestion g12-65s at 8ohms. That seemed fine. I have played that for years at staggering volumes.
I have a os1x12 port city with 1 g12-65 at 8ohms. I recently blew the speaker. I was playing it fairly loud so I guess after a few years it was to be expected.
I got a scumback very similar to a 65 but at 100 watts and 16ohms. I played it with a lot less volume and it went down after only about an hour into the set.
Any ideas, I mean I assume the power must be too much. I don't seem to see power amps for this kind of rig at 50 watts a side. I have loved my fractal rig but
I can't just keep blowing speakers! Any lower watt solutions? Why don't I see any 50 watt per side power amps? Is the flat response powered cabs really the way to go?
I want it to sound like an amp in a room, which with my current rig is perfect, I just don't want to blow speakers. I could go back to a 2x12 but I am playing in clubs in
nashville where they want to see a fender combo behind a screen, not a big ultra powerful rig like this. Problem is, I like it.

Suggestions?

 

[RobinMatrix]

Hi Folks,

I have been using the matrix gt800fx power amp with my axe fx 2 for awhile and I am running into some issues. I believe it may be just too much power.
I ran it for years with my 2x12 port city which had 2 celestion g12-65s at 8ohms. That seemed fine. I have played that for years at staggering volumes.
I have a os1x12 port city with 1 g12-65 at 8ohms. I recently blew the speaker. I was playing it fairly loud so I guess after a few years it was to be expected.
I got a scumback very similar to a 65 but at 100 watts and 16ohms. I played it with a lot less volume and it went down after only about an hour into the set.
Any ideas, I mean I assume the power must be too much.

Hi,

Firstly, let's go through what the power rating on a speaker means. The number is usually the "AES continuous" rating ... which basically means the amount of power you can put into the cab, as a continuous level, for 2 hours. This is basically a thermal limit, it is the amount of heat that can go into the speaker before it melts or burns. For some reason I have never been able to pin down, some speaker manufacturers call this their "RMS rating"

Music is typically not continuous and will typically have peaks such as power chords and rests, and even gaps between songs. There is a "music rating" on speakers that is higher than the "continuous" rating ... usually the figure is double the AES "continuous" rating. So a speaker rated "100W AES" should live quite happily on an amp rated 200W at the speakers impedance. Basically, although it will be putting in 200W of heat for some of the time, it will have lower levels for most of the time, and shoudl average out no more than the "100W" continuous equivalent.

Finally there is a "peak" rating. This is usually 4 times the AES rating, although it can be subject to mechanical limits. If for example you had an electronic drum kit, you might well choose an amp rated 4 times the speakers AES rating as the sound input is very intermittent. You would be pushing the speaker to it's physical limits but probably well below the thermal limit due to the highly intermittent nature of the signal.

A true 100W/ 16 ohm speaker should take around 200W of typical music all night long. Our GT800 will only put out 125W into 16 ohms, so you should have been fine. You are not by any chance using "bridged" mode are you? That would probably be a mistake.

Remember most "50W" valve heads will put out way more. A valve head is usually rated at the point where it reaches 1% distortion ... a head rated 50W may well put out 120W when flat out and clipping, our GT1000FX can typically be used in place of any "100W" head, and of course, there is always the volume control. My car will do 120+mph, the speed limit is (at most) 70 and more usually 30 .. but you don't have to floor the gas pedal. Same with amps, having that headroom on the power is not a danger and well within the speakers capability, but you may have to use a little care that's all.

One thing speakers do hate (with a passion) is a clipped solid-state amplifier. If you drive a solid state amp into clipping, it is quite common (apart for it sounding terrible) to cook the speaker, even with amps rated less than the speakers published capability. You are usually safer with a bigger power amplifier than one too small.

it does sound a little odd to blow a 100W 16R speaker at moderate levels .. I suspect something else other than raw power may be the culprit.

If you played a 2x12 on the amp "for years" without issue, then I would say something has changed. Have you let more bass through on the patches? It may be worth having the amp checked -- or at least check your clean patches still sound clean. If you need to send it in, let us know. Did you get the blown speakers inspected? A lot can be learned about the reason for failure by an experienced technician examining the voice coil when it has been cut out of the speaker.

 

[Lightningboy]

Even at full power the GT800 will only dish out 120w at 16 ohms so that should be within the peak rating of the driver. Were you running bridged mode on the amp? Even with a loud drummer, general stage volumes tend to get only up around 100w (60-80w usually). Going lower wattage may not necessarily solve your problems especially if you are needing volume and using a 1x12 (no matter how good the quality) to cover a large stage will always require more power to get the extra coverage. Things like extra bottom end required will make the driver work harder and there is the possibility of doing some damage.

 

[King Tone]

Alright so after some discussion with Jim at Scumback, I believe the second speaker blown (the scumback) may have been my fault. I have not blown a lot of speakers, therefore not replaced a lot. I always just stuck them in the cab and tightened up the screws fairly tight. The scumback installation method is somewhat like tuning a snare drum lug to lug. You tighten in an x pattern and not really tight. Having them too tight (what I did) does not let the voice coil move properly and guess what…

So this is where I am now. I have a 1x12 and 2x12. I blew the 1x12 (65 8ohm) speaker and put one of the 65 (16ohm) from my 2x12 in the 1x12. I then tried the scumback 100 watt 16ohm (blew it from install) now I am back on my 65 that I transplanted from my 2x12, which sounds great and those speakers really take a lot, which was a surprise when one blew. At 16ohms instead of 8 and maybe being careful I may be ok. Maybe when I get some more money I would try another scumback but I am tapped out for now. I plan to sell the 2x12 (too big and powerful) and get another identical cab and put the other speaker from the 2x12 in it. This way if I need more kick I can add the 2nd cab (and do stereo) plus it can be a backup if I blow anything else. I highly recommend Jim at scumback, he has been beyond helpful if need speakers or info on them.