Re: I keep blowing damn speakers! Why?

This may help a little: http://austin.craigslist.org/msg/839057150.html


On Sep 25, 11:33 pm, C W Smith <cwsmit...@xxxxxxxxx> wrote:
Ok, I take it you are stating facts from the top of your head as you
couldn't have read what I wrote as you stated using the crossover when
I said to bypass it which Peavey has already set up.

Then next thing is that I stated that the amp was putting out 700w for
the woofer and only 50w for the horns at that is at 8 ohms where the
Peavey cabinet is 4 ohms for the horns and 4 ohms for the 15.

As for the speakers being different I will argue that one, here are
the specs for both the 8ohm and the 4ohm Blackwidow

Impedance: 8 Ohms Power capacity: 1400 W Peak, 700 W Program, 350 W
Continuous
Sensitivity: 98.9 dB / 1 W 1 m
Usable freq. range: 40 Hz ~ 2 kHz
Cone: Kevlar® impregnated cellulose
Voice coil diameter: 4.0 inch / 100 mm
Voice coil material: Aluminum ribbon wire, Polyimide-impregnated
fiberglass former, Nomex® stiffener, Solderless diffusion welded OFHC
copper leads

Impedance: 4 Ohms Power capacity: 1400 W Peak, 700 W Program, 350 W
Continuous
Sensitivity: 98.4 dB / 1 W 1 m
Usable freq. range: 40 Hz ~ 2 kHz
Cone: Kevlar(R) impregnated cellulose
Voice coil diameter: 4.0 inch / 100 mm
Voice coil material: Aluminum ribbon wire, Polyimide-impregnated
fiberglass former, Nomex(R) stiffener, Solderless diffusion welded
OFHC copper leads

Ok, there is a difference, on is 4 ohm and the other is 8 ohm. Now you
have the specs for the Amp and the 15, the cabinet is a discontinued
model so it isn't easy to get the specs for it or for the 8" speakers
as Peavey does not list them in their replacement ***. What I do
know about them is that they are Peavey Scorpions each at 8 ohms, I'm
not sure about the power handling however I am sure that they are a
minimum of 100w each.

On Sep 25, 11:00 pm, "Mike Rieves" <mr...@xxxxxxxxxxx> wrote:



"C W Smith" <cwsmit...@xxxxxxxxx> wrote in messagenews:33e7d637-4271-4679-bde3-d82acb59e600@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Mike, to make a long story short, the cabinet handles 400 watts, the
amp hes using is 750 watts. If he were to change from a 4 ohm speaker
(this is what came with the cabinet) to an 8 ohm speaker, he would be
changing it with the 8 ohm version of the Black Widow with otherwise
the same specs as the 4 ohm.

Now instead of going over formulas to figure out what should or
shouldn't be put into the cabinet he really has a few choices:
1. If he likes the cabinet and the sound maybe if he were to pick up
another one just like it.

  If he does that, unless the amp will handle two ohm loads, he'll need to
install eight ohm drivers in both cabs and unfortunately, your assumption
that the Black Widow 4 and 8 ohm 1502 speakers have the same specs is wrong,
they vary considerably, certainly enough to affect the sound of the cabinet.
There would also still be the problem of lower impedance at higher
frequencies due to the 8" speakers. He could use another 1516 with his other
amp, but the volume gain might not be enough to prevent damaging the
speakers. Alternatively, he could rig cables that allow him to run the two
cabinets in series, which might solve his power handling problem, but would
likely bring up other issues with sound. If the 1516 was an 8 ohm cabinet,
that would have been my first suggestion.

2. Purchase another cabinet that can handle the amp he has

That would be my suggestion.

3. Purchase another amp that is better suited for the cabinet

But judging from what's happening to the speakers, that wouldn't help, he
would still be trying to drive the cabinet too hard, and with a lower
powered amp, that would result in clipping which would likely damage the 8"
speakers as well as the 15..

4. Do not use the crossover and bi-amp the cabinet (this is already
setup for that) which would allow the amp to run it's channels however
here is the catch on this one. The amp that he has is 50 watts to the
horn and 700 watts to the woofer which is still 350 watts over what
he contiuous program of the speaker allows.

The issue of overpowering the 15 would still remain. In this case, bi-amping
would solve nothing as far as his current issue goes. Also it doesn't have a
horn, it has two 8" speakers, which probably crossover at around 200 Hz, and
50 watts most likely wouldn't be enough power with a crossover frequency
that low. Crossing over at a high enough frequency that would allow driving
the highs with 50 watts would probably adversely affect the sound, and would
place more load on the 15, which is the issue now..

Now here is the idea behind the 8 ohm speaker instead of the 4 ohm,
look at the specs of the amp, the 8 ohm load will take the amp down to
a 460 watt output instead of 700 watts which may at least help in
stopping the speaker from being blown yet again. The 8" speakers would
still be set at 4 ohms and have the 50 watts even though they can
handle much more then that. The idea I would think is that he likes
what he has and just wants to fix it if possible.

As I said, there is considerable difference in specs between the 8 ohm and 4
ohm speaker, the Theile-Small parameters are totally different, they aren't
really interchangable. Secondly, dropping the power will also drop the
volume, and he's going to have to turn the amp up to compensate, resulting
in the same issue he has now. If he could find another 4 ohm speaker with
similar Theile-Small parameters and a much higher power handling capacity,
that might solve his problem, but chances are it would still change the
sound of the cabinet at least somewhat.

   All things considered, finding another cabinet that will handle the power
is the simplest and probably best solution. The efficiency of the 1502 is
98.4 dB SPL/W/M, there are plenty of speakers out there with higher
efficiency ratings and that would be helpful as well. A cabinet rated at 103
dB SPL/W/M, for example, would be considerably louder with the same power
input. If it were me, that's the way I would go.- Hide quoted text -

- Show quoted text -

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