Possible Blown Speaker-Was She Overpowered!? (Aguilar DB750/Epifani ul112 content)

Budder84 · #1 04-12-2011, 07:39 AM

So I landed a db750 a few days ago and was extremelly eager to get it in the mix. At rehearsal last night I ran it with a single Epifani ul112. My volume and gain were both set around 9 oclock ish. We were not playing loud. The Epi 112 has been my stable rehearsal cab for a year now with no worries at all (usually ran with a wt800).

A few jams into it, some major distorition started coming from my cabinet. Specifically, when I hit a "D" on the "A" string. Extreme farting.

Did I blow the driver!? Was I over powering the thing!? Or was this an amp issue?

I had to jump on a backup combo amp in the space to keep the rehearsal rolling and havent had a chance to go back and revisit the issue.

The db750 is 750 watts @ 4ohms meaning my 8ohm ul112 was getting about 375, which looking at the ul112 specs seems pretty acceptable especially not being stressed.

Ideas?

Arjank · #2 04-12-2011, 07:59 AM

Tough to say if it's the amp or the cab.
Try to run the cab with a different amp or run a different cab on the amp.
You can also unscrew the 12" driver and move the cone in and out by hand to feel if the voice coil touches the air gap.
Do this very carefully and add a bit of pressure at the center (put your fingers on the sides of the dustcap) of the speaker.

4Mal · #3 04-12-2011, 08:05 AM

Ratings don't mean jack. If you hit the DB 750 with enough oomph on the front end and / or have the low end boosted you can take out a driver like 'snap'. Sounds like that is what happened. Hopefully Epi can point you to a reconer.

Budder84 · #4 04-12-2011, 08:19 AM

Bummer

And for clarification, Eq was set flat on the db750, bright switch engaged. Slight boost on the highs and mids on my lakland 44-02. Input mode was set on "active".

Music is ambient acid jazz and I really dont dig hard, if that helps add to the discussion at all.

Arjank · #5 04-12-2011, 08:21 AM

Quote:

Originally Posted by Budder84

Bummer

And for clarification, Eq was set flat on the db750, bright switch engaged. Slight boost on the highs and mids on my lakland 44-02. Input mode was set on "active".

Music is ambient acid jazz and I really dont dig hard, if that helps add to the discussion at all.

The settings don't tell much about what happened.
You first need to make sure if it's the amp or the speaker.

4Mal · #6 04-12-2011, 08:30 AM

Quote:

Bummer

Pretty much. Trying another amp through the cab is a reasonable test but it sounds a lot like it went over the edge. A call to Epifani on the reconing topic would be my next course of action. That is a likely scenario so being prepared for that eventuality would be in order.

There is other stuff you can try. Remove the grille, make sure that all the speaker bolts are tight, nothing loose in the cab, etc - due diligence in other words. It sounds a lot like a stressed driver though.

Budder84 · #7 04-12-2011, 08:37 AM

And... bummer again.

Yea, as I said, I havent had a chance to try another amp but will do so when I get home this afternoon.

Given the context of the sound though, it really sounded like the cab, esp certain frequencies. As I said, when I specifically hit a D on the A string it faaaarted like no other.

Just unbelievable the scenario would have caused it to blow.

And the reconing topic.... how much are we talking there?

Budder84 · #8 04-12-2011, 08:44 AM

I guess the bottom line of this whole thing is: is a db750 to overbearing for a single 12" cab? Even a db112 is rated at 300watts. Is it pushing the envelope to much running it solo?

ChrisPbass · #9 04-12-2011, 08:52 AM

it's not overbearing because you have a volume knob. I asked all the same questions years ago on TB and was told 'use your ears' to which i'd say 'Yes but 400 watts a billion ohms playing a modulus in a basement w/40% humidity' and TB would say 'use your ears'. I'd say' but the ratings say....' and they'd say 'use your ears'.
You have to use your ears because you can blow a '500 watt' speaker w/a '400 watt' amp under the right situations.

you can use that combo ALL night long, safely, but you might not be able to hear it all all.
Turn the highs and mids OFF on your amp and play at low volume and then turn it up slowly. Listen. The lows will move the speaker and give you some insight.

/sorry if this sounds condescending. it is not meant to be.

christw · #10 04-12-2011, 09:05 AM

Quote:

Originally Posted by Budder84

I guess the bottom line of this whole thing is: is a db750 to overbearing for a single 12" cab? Even a db112 is rated at 300watts. Is it pushing the envelope to much running it solo?

It can be. It sounds like it might be in your case. Did you hear the speaker stressing at all up until that point? Usually you can hear it when you're hitting a speaker too hard.

Oh, and 300 RMS watts is the meltdown power of the voice coil in the speaker. I'd bet it's useful wattage (before it hits its mechanical limitations) is in the 110-140 watt range. There's good info in the Amps FAQ on power ratings. JimmyM's "rant for amp manufacturers" was about exactly this and did a great job of explaining it.

Budder84 · #11 04-12-2011, 09:11 AM

Quote:

Originally Posted by ChrisPbass

/sorry if this sounds condescending. it is not meant to be.

No worries, appreciate it. And apologize if Im beating a dead horse here but I've used this cab for a year + in the same rehearsal scenarios and the same volumes etc with no problems whatsoever (with a WT800). We do not play loud, its very controlled. I know I wasnt pushing the thing hard at all.

But I've also read that volume does not equal wattage, meaning no matter how loud you are, the speaker is still getting that wattage, whether on 1 or 10. Truth to this?

Thanks for the insight guys, I'll search for JimmyMs rant for amp manufactueres"

And if indeed the useful wattage is in the 110-140 watt range, yikes, end of discussion, that guy is fried.

christw · #12 04-12-2011, 09:16 AM

No truth to that wattage thing. The amp will hit it with 2 watts if you're super quiet or 200 if you're rocking it.

Oh, here it is for you! Hey, listen up, cab manufacturers! Rant coming!

Sundogue · #13 04-12-2011, 10:12 AM

Watts don't mean squat. It's ALL about displacement limitation.

The wattage rating of speakers (and therefore the wattage rating of the cabs they are in, including multiples of those speakers...i.e.- two 100 watt rated speakers in one cab = a 200 watt rated cab) means ONLY the wattage at which you'll melt the voice coils.

Most (not all) cabs are generally displacement limited to about half their wattage rating. Which means the speakers will only put out so much volume up to their displacement limitation and then anything above that will only be wasted heat and energy and they will fart out and blow long before you melt their voice coils.

I know just how much people love us fEARful lovers for bringing it up, but I'm trying to make a point here, so take a fEARful 15/6 for example...That is a cab where it's displacement limitation is near the wattage rating and you could literally melt the voice coil with enough wattage before it reaches its displacement limitation. Down side is you have to be careful not to melt the voice coil because you'd probably not hear it fart out before that happens. Up side is they can take a lot of power and get hellishly loud.

But yeah as mentioned, JimmyM's rant was about these stupid wattage ratings from manufacturers as if it really meant something in the real world, with regards to their cabs. No way they are going to tell you their cab can really only take half of what the "rating" states. Wattage ratings look better, so it sells more. What do you think they will tell you?

I'd listen to their argument on the subject if they'd be willing to put their money where their mouth is (or "fingers on keyboard" in this instance). Just ask them to post excursion charts for their cabs under different wattage.

Budder84 · #14 04-12-2011, 11:09 AM

great info, I learned something today

Budder84 · #15 04-12-2011, 05:57 PM

Well now that I've had adequate time to diagnose the problem, it looks like it is indeed the amp itself and not the cab. Causes farting with my ul410 as well. No idea now, looks like it might be off to the tech...

Arjank · #16 04-13-2011, 12:40 AM

Quote:

Originally Posted by Budder84

Well now that I've had adequate time to diagnose the problem, it looks like it is indeed the amp itself and not the cab. Causes farting with my ul410 as well. No idea now, looks like it might be off to the tech...

Maybe a bad transistor...