Just blew a cab for the first time

[tzohn]

Maybe standing in a bass-cancellation point? I would guess that with these settings you should be able to hear a lot of bass

 

[2F/2F]

IMHO that EQ is sending a lot of low end to the speaker, especially with the mid range voicing set on #1 and the ultra low switch engaged. Also the mids are boosted pretty good, so obviously the speaker couldn't handle it. That said, I still think something may have happened to the speaker before you took it home, whether it was pushed really hard in the store or had the levels way up and someone unplugged a bass without muting the amp thus trying to launch the driver out of the cab, because those settings don't seem necessarily extreme.

Thanks for the input. It makes sense.

I do want to point out that the bass boost switch was *not* depressed, however. Might look like it in a straight-on pic, but definitely was not.

 

[ThisBass]

I think most of underrated artifacts may belong to transient noise which comes (naturally) along with any playing of an stringed instrument. Fourier Analyses in the infinite time domain does NOT address these artifacts. Roughly explained this noise appears with any touch or plug a string and also is caused by the envelope decay an vibrating string needs to "settle down" just to produce the perceived loudness. This noise easily underruns the lowest tuning of the instrument and as long as there was no protecting filter (HPF) there is harm to damage a loudspeaker with (random) sub harmonic content.

 

[Bander]

This horn switch has a few settings, one of which is completely off (or so it says, anyhow).

Is it possible someone altered the horn wiring, so that full frequency is going to the low frequency driver?

 

[Kro]

Is it possible someone altered the horn wiring, so that full frequency is going to the low frequency driver?

I'd estimate that most 2-way cabs allow the woofer to roll-off naturally. Highly unlikely to be what's at fault, I'd wager.

 

[ThisBass]

Maybe standing in a bass-cancellation point? I would guess that with these settings you should be able to hear a lot of bass

That's indeed an possible (room acoustical) issue but (naturally) applies to a third or quard interval at most.

 

[dbsfgyd1]

Your methodology for setting up the gain seems sound enough. Needing to have bass up to 3 - and still not having it potentially be enough low end - that either tells me, again that the cab might not be the right one for you (if you're trying to overcome the cab's natural lack of bass for your taste) or, that the same underlying issue that lead to the cab's failure was maybe giving out a warning sign in the form of weakened bass.



Yes, that does seem puzzling.

Is it possible that the cab was not properly ported for the particular speaker inside? The op mentioned this was a demo-used. I think I like to know if this was a stock speaker design4d for this cab. Just a thought.

 

[ThisBass]

Is it possible someone altered the horn wiring, so that full frequency is going to the low frequency driver?

There is way too less energy stored in the highish range of the spectrum which (as additional) energy might be addressed as responsible to fry a woofer

 

[ThisBass]

Did the OP already told his personal sound goals and playing style technique and loudness needs?
IIRC once a bass player fried cabs frequently due to very expressive (excessively) solo parts.
edit, which brings me back to consider transient noise artifacts

 

[Ross W. Lovell]

Got a PF-800 and PF-115HE back in Feb. Played it once for about 10 minutes back then, and haven't played it since. Turned it on today I and blew the thing in about 30 seconds with my passive Jazz Bass.

I was running the PF-800 with very little gain (red light would only slightly light up if I pounded on the E string – well above my actual playing level), and the master at about 2:30 o'clock. Mid band selection switch on 1, mids at 2 o'clock. Bass at 3 o'clock. Treble at 10 o'clock. None of the push-button switches engaged. I was loud, but not extremely loud, and I wasn't playing really hard. No warning signs in the tone; it was nice and clean. Speaker just turned to a thin buzz instantly and I smelled that burned electrical smell. I opened the top panel and smoke poured out.

I would not call those very extreme settings, personally. I had plenty of room to go up on the master, as well as the bass and low mids. The bass tones did not seem huge or boomy, but rather "just right." However, what do you think? This thing was a floor model, so it could've been hammered before I ever touched it. Or were my settings really that unsuitable for this cab? I have not blown so much as a fuse in my 25+ years of playing, so this is rather a new thing for me.

Interesting. Before the PF-800, I had one bass amp for 20+ years (B-100R). I feel like I have totally abused that amp: run with the volumes pegged sometimes, and always turned up high. Bass knob is usually turned to 8, 9, or often 10, with the boosts always engaged. Low mids run on 7.5, never lower. Kept in in my trunk for literally years straight, etc. It has never had a single problem. I finally "upgraded" so I wouldn't have to push my amp so damned hard all the time. Ironically enough, I was worried about finally killing the B-100R, so I got the PF.

I was under the impression, possibly mistaken, that my speakers should be able to take twice the RMS Rating of my amp? Anything less and if the amp somehow clips it's going to make TWICE the watts IPP?

I know very few single speakers that would take double that amp's rating, but I'm sure the others will educate me on what new stuff is out there.

 

[ThisBass]

I was under the impression, possibly mistaken, that my speakers should be able to take twice the RMS Rating of my amp? Anything less and if the amp somehow clips it's going to make TWICE the watts IPP?

I know very few single speakers that would take double that amp's rating, but I'm sure the others will educate me on what new stuff is out there.

Actually its possible to strain a 200 Watt power handling device with 600 watt for a short time period but its not possible to strain a device with twice the rated power over time.

Again it would help us a lot if we would know something about your sound goals and playing style technique. I want to tell you again that transient noise can cause very nasty things ....

 

[Kro]

I was under the impression, possibly mistaken, that my speakers should be able to take twice the RMS Rating of my amp?

In theory, cabs should be able to withstand bursts of power double that of their RMS rating.

The flip side is that amps are usually capable of also putting out approximately double their RMS rated output in bursts. Those smarter than me can weigh in, but I believe that whether we're talking amps or cabs, the formal calculation for burst or "max" power is double RMS (or is it RMS is half of burst...)

I'm not going to go into the difference between thermal and mechanical limitations here, but suffice to say that from an RMS standpoint, as long as the values aren't manipulated or misrepresented they're at least somewhat useful as far as a cab's thermal rating being aligned is concerned.

Anything less and if the amp somehow clips it's going to make TWICE the watts IPP?

Unless I'm mistaken, it's not like an amp starts clipping and all of a sudden immediately produces double the watts. Amps are given their RMS rating at a certain, usually still "clean" level of distortion (THD). Go above that, and you get more power with more distortion - audibly more as you get higher and higher.

Depending on how you run your amp, you might only get those bursts on transients, and so they're pretty fleeting, which is why they might not be very noticeable, but they can still tax a speaker.

 

[Just George]

So some of you are saying that this is Ampeg's fault? LOL! Yeah, right! As the owner of a PF800, I know that if you turn the gain up to the point right before it starts clipping and put the master at 2:30, you're pretty much giving your cab everything that the head has to give and then some. Don't forget that heads can produce more power past their RMS rating in peaks. This is why you must never ever trust numbers or knob positions over your own common sense. I regularly use my PF800 with the PF112hlf, and because I use my common sense, I've never even come close to blowing the speaker. If you want to be that loud, you need considerably more cab.

Also, regarding the 30w head blowing a 410, it would have to be a really weak-ass 410 for it to blow.

Yep....I routinely use my PF-800 through 1 SVT-112AV with no blowing up...I normally have the gain around 1:30 and the Master varies. Through an 8 ohm cab it's putting out roughly 400 watts. I'm also careful not to run the bass control too high. I also use the PF-800 through 2 SVT-112 AV's in which case there is less to worry about but still I can tell when enough is enough. As far as the comments on it being Ampeg's fault.....Nope.

 

[Old Garage-Bander]

Clock position has "o'clock" after the number.

Yup, just sayin' it's probably best to not mix clock with 1-10.
You know, for those of us who have trouble with multiple, simultaneous concepts.

 

[12bass]

Don't mind mixing terminology so much... but saying 9 o'clock whilst meaning 3 o'clock is definitely confusing! Perhaps the speaker got so confused by the knob position that it lost the will to live and gave up....

 

[Old Garage-Bander]

We clearly need something simpler. I propose we standardize on clock hour hand position, expressed as bells.

Invalid Link Removed

Not to be further confused by the audio measurement value, bel which is 10 decibels.

 

[Acoustic356]

Got a PF-800 and PF-115HE back in Feb. Played it once for about 10 minutes back then, and haven't played it since. Turned it on today I and blew the thing in about 30 seconds with my passive Jazz Bass.

Obvious question, but since no one has asked it yet, I will...

Were you using speaker cables to connect the head to the bass or guitar cables?

 

[BadExample]

Not to be further confused by the audio measurement value, bel which is 10 decibels.

Best not to crank the bass past 6 bells, afternoon watch in most cases. Many cases, not past 8 bells on the forenoon watch.

 

[Bander]

There is way too less energy stored in the highish range of the spectrum which (as additional) energy might be addressed as responsible to fry a woofer

I agree, its not a design issue with either the amp or the cabinet. Its got to be something unconventional. Modern cabs and drivers are very robust, and forgiving. Either the amp is malfunctioning, or the cabinet has some issue. If the high frequency is heavily clipped, the coil cant respond fast enough to cool itself, and could overheat, correct?

 

[Kro]

Modern cabs and drivers are very robust, and forgiving.

Modern amps are exceedingly powerful...