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Just blew a cab for the first time

#61
2F/2F said:
Well, moving on to fixes:

How about some suggestions for a good way to get the amount of cleanliness, volume, and low end I want from this amp. I know it's in there, because I heard it the first time I played through the cab at lower volume (about noon on the master) with more lows dialed in. The tone was great; the volume didn't cut it. I just need the right cab/s to let it out. I will get this little guy fixed up for lower intensity situations, or maybe use my friend's PF-350 through it, and find a better cab for gigs.

I'd love it if the solution was within the Portaflex line, but I could be open to something outside the line. That Ampeg 2x12 does look tempting (almost bought it initially instead of the PF-115HE). The 4x10 Portaflex cab would probably be my next trial. Hope it fits in a Challenger. That is a consideration for me. Would love it to be flip top, but I guess that ain't in the cards with the PF-800.
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2 410HEs for real. But, the Peg 2x12s are amazing. But...I still love my 610hlf. Great sound, good power, loud af, just big enough...til I hook up another one :)
 
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#62
Bander said:
A couple thoughts. Usually, when you are overdriving a woofer, you should hear it reaching its mechanical limits - popping, edgy, general bad sound. That's usually the hint that you are overdriving it. Second, its easier than we think to crank a large rig at home. I run a 700W rig, and when I first got it, I was cranking it to nearly half volume with two cabs, I knew it was loud, but it didn't seem louder than gig volumes. But when playing in a loud cover band with two Marshalls, I never cranked it more than 1/3, and it sounded too loud then. Something about playing in the house masks just how loud it is. Not that your 400W cab is that delicate, but just pointing out how deceptive loudness is, and dependent on the room and situation.
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Right? I've got a pretty good size house, and wood floors. For some reason, the low end just drops. Somehow though every window, door, and anything hanging is rattling as all hell. I actually knocked all my wedding pictures off the wall when I first got my set up. Wife was pissed. It didn't seem half as loud, or low as I wanted it to be. On stage, volumes at like 2. If even. No PA. Bass is roaring in videos.
 
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#63
2F/2F said:
I barely got the blink if I really tried hard. I set the gain using that as an indicator, i.e. set so that I barely got the blink at a level or ferocity I would not be playing at. I was not actually playing it like that.
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Gain was too low, master was too high. Lows were likely also contributing to speaker damage.

I think you were really just asking a bit too much of a single 15" driver.
 
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#66
Obviously the cab couldn't take the amp settings I had it at; the proof is in the pudding on that. But what really confuses me is that the thing did not sound distorted before it went. The amp sounded strong but clean, and very tonally balanced – as in not particularly weighted toward any part of the tone spectrum. It was loud enough to play with a medium volume drummer, as I was doing, but not loud enough to keep up with a "real" heavy rock drummer. It sounded a rather boring tone, really. I was playing on the E string, just thinking I'd head over and monkey with the tone in a bit (I was gonna dial in more dirt/less master), and then it just blew.

I switched over to my B-100R, and it was about as loud, bassier, and very distorted. Considering the significant distortion levels I've been hammering my B-100R with for 20 years with perfect reliability, nothing about the PF-800's tone seemed to be a warning sign. Gain super low, master proportionally lower than I run it on my other amp, less low end than I normally use, way more clarity than I normally use, higher rated speaker than I normally use, not hammering the strings, etc. Just a pop, then nothing but fuzz.

I understand that I obviously blew it, but I'm trying to find where the common sense saves the day here. I actually thought I was heeding the advice I had received here and treading a bit lightly on the new setup, considering the very low amount of gain and distortion, and relatively moderate use of the bass knob (which I am used to running at 3/4 to full up, with dimed master volume on the B-100R).

Out of technical curiosity, how would two PF-115HEs handle the amp at 800W better than one PF-115HE would handle the amp at 400W? Amp wouldn't need to be pressed as hard to get the same amount of volume and low end in the room?

I've got old B-42X, B-25B, and V-4 cabs here, but after today, this amp ain't gettin' near 'em! Gonna hafta get this PF-115HE fixed before using the PF-800 again.
 
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#68
bass71 said:
So how many times in the past did you dime the bass? ....a speaker will only put up with that for so long...sounds like it decided to call it a day.
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Never on this amp or cab. OP states the amp has been played for a total of 10 minutes and 30 seconds over two sessions two months apart. The first time, I played relatively quietly alone with flat-ish e.q. for 10 minutes. This time I played with a relatively quiet drummer. I often dime (or close to dime) the bass and master on my B-100R; that's what I'm referring to when I say things like "what I'm used to" or "what I normally do."
 
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#70
From here, it is not possible to know if the woofer was weak or faulty before it blew. Also, it is hard to know exactly how much power was going into it when it failed due to differences in subjective assessment of volume, amount of bass, and other factors. In short, we know that it blew, but not exactly why, though overpowering seems the most likely cause.

By adding another similar cabinet in parallel you lower the impedance seen by the amp which increases the amp's available power (but bear in mind the minimum rated load). Adding coupling effects, this provides a roughly 6dB increase in volume, which is an easily audible difference. This allows you to get more volume overall, but with less stress on the individual drivers because they share the load. If more volume is needed, adding more drivers is generally a much better idea than pushing more power into a single speaker.

It also sounds like the B-100R was routinely overdriven, yet the drivers were able to take the abuse. Perhaps it has a built-in limiter? Also note that the harmonics generated by clipping make the sound subjectively louder than a clean, deep, signal. A 25W guitar amp running with full distortion lead guitar can easily overpower most 500W bass amplifiers reproducing deep bass. This is due in part due to differences in the sensitivity of the human ear and the fact that it generally requires much more power (and larger/heftier drivers) to reproduce low fundamentals at similarly high sound pressure levels.
 
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#71
Bassmec said:
So I just sold my old Acoustic 408 for proper money to a nice bloke in Italy, so minimalist rulz don't apply everywhere.:)X
PS I don't think rock and roll deserves downsizing personally.
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Eh, there's downsizing, and then there's downsizing. IMO there's a big difference to showing up with something like a TE Elf 2x8 and a BF Super Twin.

2F/2F said:
Well, moving on to fixes:
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I know that it's never fun to take gear, new or old, into the shop, but I think that that is potentially the next step. A few posters here have made the good suggestion to make sure that the amp isn't misbehaving as well - and a tech looking at the cab might be able to tell you more about what's gone awry.

Barring that, IMO a 212AV would likely be the next step up, or adding another 15" to your existing cab once repaired.
 
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#74
2F/2F said:
Out of technical curiosity, how would two PF-115HEs handle the amp at 800W better than one PF-115HE would handle the amp at 400W? Amp wouldn't need to be pressed as hard to get the same amount of volume and low end in the room?
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Volume is basically air displacement. The more the total cone area, the more air gets moved. You need to keep the cone size reasonable due to the physics in the equation. There’s a practical limit to how big you can economically make them. So four or more 10s became the winning combination for high volume bass. That kept things tight but still pushed air.

There’s a lot more to it than that. And I ran roughshod over the actual technicalities and physics a bit. But the takeaway is: if you want more volume, you want more speakers or cabs - not more watts - almost every time.
 
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#75
2F/2F said:
Obviously the cab couldn't take the amp settings I had it at; the proof is in the pudding on that. But what really confuses me is that the thing did not sound distorted before it went.

I understand that I obviously blew it, but I'm trying to find where the common sense saves the day here.

Out of technical curiosity, how would two PF-115HEs handle the amp at 800W better than one PF-115HE would handle the amp at 400W? Amp wouldn't need to be pressed as hard to get the same amount of volume and low end in the
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All good questions, and like you, its unexpected for a cabinet to be that delicate, when there's no audible indication of distortion. Did I read that you disconnected the horn? If so, could you have bypassed the crossover, so the mid and high frequency was going to the woofer? You wouldn't hear some heavily clipped mid or high frequency, and that could over heat it?

Two cabs will divide the power in half so each only sees half. If you ran your 800W dimed into two cabs, each would only see 400W. One cab will see the whole 800W.
 
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#79
So this penguin is driving through Alabama in the middle of the hottest summer in memory, and his car suddenly starts running really badly. He pulls into the first service station he sees, and the mechanic tells him they will take a look. Since it's so hot, and he's a penguin, he goes to the Dairy Queen next door for some ice cream while the mechanic puts his car on the lift.
Half an hour later he waddles back to the service station. It's so hot that his vanilla ice cream has melted faster than he can eat it, and he's got it all over his chin and it's dripping down onto his chest. He goes into the service bay and the mechanic says, "looks like you blew a seal."
The penguin looks down and says, "Oh, that's just ice cream."
 
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#80
2F/2F said:
I have not blown so much as a fuse in my 25+ years of playing, so this is rather a new thing for me.
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Hi 2F/2F :)

:poop: happens! :sorry:

2F/2F said:
I was loud, but not extremely loud
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Looks like your speaker (RIP) did not share this point of view. :(

What can I say? 400 watts@ 8 ohms can easily fry a 400 watt 8 ohm speaker!

Most TB members will tell you to use your "common sense" :D
and what they mean is, " keep the volume down" :laugh:

I won' t say that is wrong.
I try to keep my stage volume as low as possible these days. (getting old :D)
But I played in a "two 412 guitars and a loud drummer rockshow" for 25 years

"Common sense" is for sissys! ;) What you need is more headroom! :hyper::hyper::hyper:

Get two cabs, to get the max out of that pf800!
And make them "bigger" than just 400 Watt each!!!!!!!!

Wise(b)ass

btw: someone posted, that you should have your amp checked!
IMO that was good advice. :thumbsup:
 
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