why is 125 watts blowing our 350 watt speakers?

[i love everyone]

okay, so my band's bassist uses a 2x15 cab loaded with brand new versions of the Peavey Black Widow speakers that it came with a long time ago, and plays through a Peavey Mark VI head with a compressor that puts out 250 watts RMS into the 4-ohm load from the 2x15 cab. the speakers are 8 ohms each wired in parallel, and each is rated at 350 RMS, 700 watts program.

the band we're in now plays super-raw, noisy punk, and the bass is basically set with the pre-gain at 10, the low at 0, and the high at 10, and gives a really really trebly, noisy sound when played loud enough. i realized this would potentially be unsafe for the speakers, so we made sure the cab could handle way more than the amp gave it (250 watt amp, 700 watt cab), and even used 12-guage wire in the cab as a precaution. however, a few weeks ago, the speaker closest to the input jack blew, and we got a replacement basket for it (which is very convenient on these Black Widows). then tonight, the other, unreplaced speaker blew, and we had it connected in the position closest to the input jack, as well (i didn't think that would make a difference, though).

anyway, i was very surprised that this happened twice in such a short time, especially because we weren't using the extremely bassy settings that i usually associate with blown speakers, and the speakers were rated for well over twice the power they were receiving. any advice on how this can be prevented in the future? different speakers/amp settings? because it's becoming a very annoying, and expensive problem.

 

[Christobevii3]

Re: why is 125 watts blowing our 350 watt speakers?

Clipping will cause the signal to double. Also thermal power handling a mechanical power handling aren't the same. They depend on the type of enclosure they are in too.

 

[Boogie Bill]

Re: why is 125 watts blowing our 350 watt speakers?

Actually, it sounds to me like you're not using enough power.

Bill

 

[jeremy]

Re: why is 125 watts blowing our 350 watt speakers?

how high is the post gain set?

that 250w rms amp could be pushing easily double that and possibly way more if you are running it really high. 250w is the "clean" power rating

if you are clipping the power section on the amp then you will continue to blow bass speakers.

the 12 gauge wire is letting as much of the frequency and power get to the speakers from the amp, the amp might run cooler but if anything having that big a pipe line may be hurting the situation.

typically you want to overpower pa and bass speakers so that you can hit them with XXXw of clean power. which i think is what bill is suggesting. if you have a 500w cab you want to be able to hit it with 495w of clean power which i would use an amp that is about 50% more potent than you need, so 700w-800w. thats not an industry spec but just a range i think works well.

in your situation you may not want to do that if part of the tone is the way the amp sounds when its cranked. if you are really punishing the speakers i might go for a high power guitar speaker that was designed with handling distortion in mind. eminance makes so good speakers that arent overly expensive and i believe are still made in the usa

 

[Metalman_666]

Re: why is 125 watts blowing our 350 watt speakers?

Jeremy, just curious: wouldn't a guitar speaker be worse off for a powerful bass amp? I guess I must be wrong but I would assume the guitar speaker would blow or rip or just be damaged a lot more easily than a bass speaker.

 

[Binnerscot]

Re: why is 125 watts blowing our 350 watt speakers?

Sounds like power amp clip. Highly compressed signals will also wear of speaker voice coils much faster. It is one of the reason sound guys do not compress live shows to the level of compression you hear on recordings. Solid state power amps clip in a square wave fashion, which is fatal for speakers. Tubes tend to compress more and do not clip is a square wave (though excessive tube saturation will also produce a highly compressed signal also, which will wear the speakers faster)

You need more power for a clean signal.

....like Jeremy said.....

 

[jeremy]

Re: why is 125 watts blowing our 350 watt speakers?

Jeremy, just curious: wouldn't a guitar speaker be worse off for a powerful bass amp? I guess I must be wrong but I would assume the guitar speaker would blow or rip or just be damaged a lot more easily than a bass speaker.

typically yes but if you read the post if says they run the bass off so that becomes less of an issue. if he was using the bass amp in a more traditional way (loud thumpy bass heavy tones) then a guitar speaker wouldnt be a good option, but since we seems to be talking about buzzsaw bass i think a different approach might be necessary

 

[ksmith63]

Re: why is 125 watts blowing our 350 watt speakers?

amp clipping will greatly increase the power sent to your speakers. it can also send a subsonic signal to them causing lots of damage.

Jeremy, just curious: wouldn't a guitar speaker be worse off for a powerful bass amp? I guess I must be wrong but I would assume the guitar speaker would blow or rip or just be damaged a lot more easily than a bass speaker.

guitar speakers are designed to be mid range drivers. the higher the frequency, the less the speaker cone has to move, the cone doesnt have to be as thick to stay linear, less power is needed so you dont have to worry as much about melting the voice coil, and the speaker fs (resonant frequency) doesnt have to be low. if you played lots of bass through guitar amp speakers you will kill them in no time.


BUT there are speakers that are known to do both guitar + bass. electro voice made some (12L? maybe) that were supposed to be heavy duty enough for bass but also had enough high end for guitar.

 

[J Moose]

Re: why is 125 watts blowing our 350 watt speakers?

Another vote for square wave clipping.

With solid state amps (and in general) you should ALWAYS overrate the amps to the speakers. Use 500 watts to drive 300 watt speakers..not the otherway around.

Unless this new set of speakers are rated much lower (like 100 watts each) they'll eventually blow up too.

 

[lastwinj]

Re: why is 125 watts blowing our 350 watt speakers?

could also be a bad power amp. i had a client who blew a peavey PA 15". was using an old acoustic PA amp. i checked the output, no DC voltage, but all of a sudden, it spiked to 60vDC. that will kill a speaker quick. it was intermittent, and i couldnt get it to do it again, but it explained the problem.

 

[marvar]

Re: why is 125 watts blowing our 350 watt speakers?

Actually, it sounds to me like you're not using enough power.

Bill

This is the problem
You are clipping the power amp, which in turn is producing square waves.
Speakers don't like square waves- just like shooting the speaker with DC current.
BTW- have you ever seen a speaker catch fire? extremely cool to watch, a great stage effect!

 

[ginormous]

Re: why is 125 watts blowing our 350 watt speakers?

+1 for amp clipping. Does the compressor also have different attack settings? Maybe it's not grabbing the first transient spike fast enough, and the speakers are eating the top of the signal.

Try backing off the preamp to 8 or 9; alternatively, wire a circuit breaker just after the input jack, that is if there's a switch plate to mount it on. Might save money on bass drivers.

 

[Reload in 5]

Re: why is 125 watts blowing our 350 watt speakers?

This is the problem
You are clipping the power amp, which in turn is producing square waves.
Speakers don't like square waves- just like shooting the speaker with DC current.
BTW- have you ever seen a speaker catch fire? extremely cool to watch, a great stage effect!

square waves have the same basic effect as DC on a speaker.

Have you ever plugged a speaker wire into AC from the wall ?
4ohm 100w speaker + 3000w 60Hz = lots of noise and smoke.

 

[i love everyone]

Re: why is 125 watts blowing our 350 watt speakers?

yeah, i talked to a tech at Peavey and he said just like everyone here, that it was power amp clipping.

also, would it be safe to use a stronger power amp? is that so you get speaker distortion before amp distortion? otherwise we'll probably just use a distortion pedal instead.

 

[baritone]

Re: why is 125 watts blowing our 350 watt speakers?

Another vote for square wave clipping.

With solid state amps (and in general) you should ALWAYS overrate the amps to the speakers. Use 500 watts to drive 300 watt speakers..not the otherway around.

Unless this new set of speakers are rated much lower (like 100 watts each) they'll eventually blow up too.

That doesn't sound right to me. I try to look for speakers which handle at least 3x the amps output. My 4x10 cab handles up to 300 watts, which is about 10x the output of my amp head.

 

[jeremy]

Re: why is 125 watts blowing our 350 watt speakers?

for guitar speakers you want as much or more power handling than your amp can dish out. for pro audio and many bass applications the reverse is true

 

[J Moose]

Re: why is 125 watts blowing our 350 watt speakers?

also, would it be safe to use a stronger power amp? is that so you get speaker distortion before amp distortion? otherwise we'll probably just use a distortion pedal instead.

Yeah, something like that. A speaker can only get so loud in a given space before it starts becoming painful, doesn't matter if it's a 1x12 50 watt combo or a 5000 watt PA rig.

With PA rigs, bass amps etc. you NEVER want the amp to run out of headroom and clip...the occasional clip is fine & won't hurt anything, but running into the red all night is going to fry stuff.

Kinda like an engine. You don't always want it turning at 7500rpm...

When the amp clips and the speaker gets a square wave on the input, rather then moving in & out in a 'circular' motion, the speaker moves out and stays out...then moves in & stays in... do it long enough and it'll build up heat, melting the glues and voicecoil.

Like Jermey pointed out, the inverse is true for tube guitar amps & actually...tube power amps in general. Soft clipping vs. hard (solid state) clipping.

 

[devastone]

Re: why is 125 watts blowing our 350 watt speakers?

Like Jermey pointed out, the inverse is true for tube guitar amps & actually...tube power amps in general. Soft clipping vs. hard (solid state) clipping.

Just to clarify, the inverse is true for TUBE amps, you can still run into square wave clipping and blown speakers from SS guitar amps.

Of course, you also have to use your head. You may have 10,000W of power in your PA, into speakers that can handle 6000W, the power to the speakers will be clean, but, if you crank the power way over the limits of the speakers, you can still smoke them with too much clean power. (same applies to a bass rig, or SS guitar rig for that matter).

But the general rule is correct, always have more power than you think you need for SS applications.

 

[aleclee]

Re: why is 125 watts blowing our 350 watt speakers?

the pre-gain at 10, the low at 0, and the high at 10, and gives a really really trebly, noisy sound when played loud enough.

Clipping will cause the signal to double.

Hmmm. Preamp gain at 10 and you think that there might be clipping?

 

[James Rock]

Re: why is 125 watts blowing our 350 watt speakers?

With solid state amps (and in general) you should ALWAYS overrate the amps to the speakers. Use 500 watts to drive 300 watt speakers..not the otherway around.

Maybe im getting this wrong but i thought it was that u should match wattage and never reach clipping but not have a power amp that puts out more wattage then the speakers can handle.