Can equal amp/cab watt ratings cause distortion?

[PuffusMaximus]

I have a fender TB1200 that i run through a carvin 2x15 4ohm 800w cab. The head runs 800w at 4 ohms. when i really dig into the lower notes the sound gets pretty distorted. Ive been told that its a good practice to get a cab with a higher watt rating than the amp puts out, which makes sense, but can having the equal watt rating be a bad thing and be causing the distortion perhaps by putting out just a little too much power?

[Marton]

DOes the distortion come from the head or the cab ?

[BurningSkies]

Yes. Most cabs are rated by their thermal limits. Distortion is caused when a speaker has reached its displacement limits. Most speakers reach their displacement limits well before they hit their thermal rating. The more lows you have in your sound, the more your speaker moves, and the closer you are to its displacement limits.

Displacement limit is known as x-max. The x-max of a speaker is when the voice coil leaves the magnetic gap. At that point the speaker goes non-linear and distortion occurs. If your speaker goes even further, it will exceed x-lim, the mechanical limit of the speaker, that's the point where your speaker has ripped itself to shreds.

[BassmanPaul]

Remember that most cabinet ratings are the thermal limits of the drivers. That's the point where they start to melt. Real world is about half the thermal ratings. So yes if you get past that point the drivers have run out of excursion.

[PuffusMaximus]

@marton im thinking the head. i hooked the amp to a 410 that rated 600 at 8 ohms (head puts out 550 at 8ohm) and it had a tiny bit of distortion, but not as much as with the 215. i could also be mistaking that for a bit of growl with the 410?
on the head there is volume for tube tone and a master. before with the heavy distortion, i had the tube volume all the way up. but then i put it at 5 and it was pretty much gone

[will33]

Cabs run into distortion when they start to exceed xmax. That's the excursion limit, or how far the cone can physically move back and forth and still reproduce the frequencies it's fed by the amp evenly and clearly. When you exceed that point, the speaker can't produce anymore bass, the upper harmonics may still get a little louder accompanied by distortion and farting in the lows and whatever power you feed it beyond that has to be burned away as heat in the voice coil. The power it takes to reach that point it always much less than it's "wattage" rating. In the case of speakers, those power numbers represent how much heat the voice coil can take before it melts, not how much power the speaker can actually make use of/turn into sound. Unless it has top shelf premium drivers, which the vast majority don't, including yours and mine, the excursion limit will be roughly half, in some cases 1/3 of the speakers power rating. Excursion limited power is never published because it results in smaller numbers which don't look as impressive.

[will33]

Amps are rated at a certain power at a certain % of distortion. If you run the amp wide open it has can put out more power than it's rating accompanied by more distortion, unless it's initials are "T" and "C".

If these two points happen to be close to each other regarding amp and speaker, it can sometimes be hard to tell if it's the amp, the speaker or both causing the distortion. If you're using distortion as part of your sound, it can make it very hard to hear when your speakers are in trouble and easier to blow them. In those cases, it's best to use more speaker than you need to be sure it can handle it and let the pedals, or in the case of tube heads, the amp provide the distortion.

[PuffusMaximus]

@BurningSkies @BassmanPaul thanks for the info, i love lurning these kinds of things
@will33 so do i possibly have a bad setup?

[Rick Auricchio]

Originally Posted by PuffusMaximus

...im thinking the head. i hooked the amp to a 410 that rated 600 at 8 ohms (head puts out 550 at 8ohm) and it had a tiny bit of distortion, but not as much as with the 215.

That's a false assumption. It could simply be that the 410 cab handles higher levels without farting out.

[rockstarbassist]

Do you have a lot of uber-lows maxed out or really high? Say, anything under 150hz? That's an easy way to fart out even great cabs is not scaling back the Bass and Low End EQ when you get loud.
When I do say an outdoor show and I know the amp will need to be turned up, I cut back my Bass and other EQ points considerably so I don't run into that.

[PuffusMaximus]

@Rick so it might not be because the 410 had a little headroom and the 215 didnt?

[PuffusMaximus]

@rockstarbassist my eq is almost flat. i have the bass all the way down, mid all the way up, and treble all the way up. then with my 'vari-q' i cut the mids around the 300hz range

[Thunder Pulse]

You didn't say what volume you're playing at when you hear the distortion?

You could be playing at a low volume and still hear distortion if you're digging in hard enough to overdrive the front end of the amp.

[will33]

You don't have a bad setup, just listen to the speaker, when it start to distort, that's the limit. Just turn down the volume or bass knob slightly from that point and consider that full power, wherever the knob happens to be set. You can add more volume and less bass or more bass and less volume, just find a balance you like the sound of. If it's not loud enough, add another cab. Your amp isn't putting out all that power unless it's cranked way up. Most people who think they're pushing 1000 watts are consistently using maybe 100 or 200 of that save for the transiet spike at the beginning of a note or the attack on a pop or slap.

[rockstarbassist]

Originally Posted by Thunder Pulse

You didn't say what volume you're playing at when you hear the distortion?

You could be playing at a low volume and still hear distortion if you're digging in hard enough to overdrive the front end of the amp.

This too. Try cutting back Gain, increasing Master Volume?

[PuffusMaximus]

Originally Posted by Thunder Pulse

You didn't say what volume you're playing at when you hear the distortion?

You could be playing at a low volume and still hear distortion if you're digging in hard enough to overdrive the front end of the amp.

heard it at all volumes on the master control, and everything past 6 on the tube volume. when i turned the tube volume down it went away significantly

[will33]

You can use a 10,000 watt amp on a 10 watt speaker if you don't turn it up too high. Point is don't worry too much about matching ratings, just listen to your speaker, it'll tell you when it's had enough.

[will33]

Originally Posted by PuffusMaximus

heard it at all volumes on the master control, and everything past 6 on the tube volume. when i turned the tube volume down it went away significantly

Could've been overdriving the pre tube which won't hurt anything, it's a tone you can get out of such a setup, put there on purpose. I do this on my tmax sometimes by setting the pregain higher than the post gain (all that's before the master). If yours doesn't have both knobs, it may have a fixed post gain built in meaning when you turn the tube gain up to a certain point, it'll start to overdrive the tube.....on purpose.

[dukeorock]

Originally Posted by PuffusMaximus

I have a fender TB1200 that i run through a carvin 2x15 4ohm 800w cab. The head runs 800w at 4 ohms. when i really dig into the lower notes the sound gets pretty distorted. Ive been told that its a good practice to get a cab with a higher watt rating than the amp puts out, which makes sense, but can having the equal watt rating be a bad thing and be causing the distortion perhaps by putting out just a little too much power?

I have had a couple TB1200's...still have one and those things are one of the loudest amps I've ever heard! For a few years, I ran that amp with two Fender 810 Pro cabs, getting the full 1200 watts at 2ohms...you could knock over buildings with that thing! For in-town, smaller gigs I briefly ran that amp with a Genz Benz 410XB2 cab (8ohms) and it sounded wonderful...I can't stress enough the importance of a really serious cab to handle that much horsepower. The Fender 810 Pro cab is a very nice match for it, though I did once blow a cab to bits at at outdoor festival. The Genz Uber series cabs can take a lot of juice...regardless of what cab you get, make sure it can take it...that amp is a hoss!

[Pilgrim]

If you have the bass frequency boosted too much, you can get the amp to distort or fart out at much lower volumes than normal. Don't neglect that possibility.