BillFitzmaurice.info

Would this amp work for T39's with a 3012LF Kappalite? Or is there not enough power? It's rated at 350 into 8 ohms per side and can be bridged to give 2,000 watts into 4 ohms.

Would like to see if this will work non-bridged - one T39 per side - being that it would be limited to 50 volts. The ohm voltage calculation says yes, and it is for live sound, not a DJ rig.

I get 52V out of 350W/8 ohms by the calculator I use.

The T39 with the 3012lf will have a nominal impedance of 10 ohms. Recalculating means you only need 250W for a 10 ohm load for max volume to limit.
By and large, I would use it.

Some would say that a couple of volts only over max is perhaps going to take an amp to the bleeding edge at max volume, and would suggest a larger amp with say another 50-100W of output (not run in bridge mode when possible).

I guess in the end it would depend if Ashly have been conservative in their figures.

Where the amp you are asking about falls down is: if you are ever going to use more than 1 cab/channel you can't reach max output of the cab at the bleeding edge.
Calculator says the 600W/4 ohms is 48V. Recalculating again to 5 ohms still means you're right at the edge.

IMO you should always future proof new purchases to some extent...

I actually called them today and they said the voltage swing is 53 volts, which would seem enough.

And correct me if I'm wrong but for live music, wouldn't the 53 volts be enough? It's not like I'm slamming it like a DJ does with compressed music. Or would the kick drum's "kicks" send it into clipping?

I thought volts are the same regardless of load - in other words if it puts out 53 volts at 8 ohms it should also do the same at 4 ohms?

yigba wrote:I actually called them today and they said the voltage swing is 53 volts, which would seem enough.

I thought volts are the same regardless of load - in other words if it puts out 53 volts at 8 ohms it should also do the same at 4 ohms?

If you want to limit to 50V with one pair of T39's, ie one per channel, then you're getting very close to the max output (RMS output, not peak) of the amp you mention. Whenever and wherever possible, you should not run an amp hard all the time. Something is likely to give after a period of time, usually mid gig. Not good for the show or your reputation.

Say you end up doing outdoor live sound or larger indoor venues. Your sub cab ratio to top ratio should be a minimum of 4 cabs (not 2) for that situation. ie 4 ohm figures come into play because you're going to have 2 cabs/channel

Sadly your assumption is incorrect regarding voltage vs load.
From Ashly specs for the KLR2000:
Output per channel is 350W/8ohms = 52.9V
600W/4ohms = 48.9V
1000W/2ohms = 44.7V
Amplifier output as impedance load is lowered is rarely linear (ie regardless of load you don't get the same voltage output). Energy cannot be created nor destroyed, only converted to other forms of energy.
As impedance lowers, amperage increases, producing more heat. The increasing heat, in part, accounts for the loss in Voltage output. The other influencing factor is often enough the amplifiers power supply's ability to keep up with demand.
As you can see from the specs above, voltage output has decreased as impedance load is lowered.

And correct me if I'm wrong but for live music, wouldn't the 53 volts be enough? It's not like I'm slamming it like a DJ does with compressed music. Or would the kick drum's "kicks" send it into clipping?

This depends entirely on what type(s) of live music you're doing.
If you want "chest thump" for a kickass R&R band, then you need a minimum of 110dB in the 50 to 70 HZ range. That's not to hard to achieve at the cabs, but you lose 6dB with each doubling of distance. So if you're doing PA in a room that's 48 feet or 16 yards deep, and want chest thump at the back of the room, your output requirement has jumped to 134dB at the cabs. That's 2 x T39 3012lf loaded about running at max or 50V. You might have clipping, it would depend on your gain structure somewhat, but once again, you're running your amp at the bleeding edge of it's capability, give or take a few volts. Even brick wall limited to 50V a few volts is only 40 odd watts shy of the 53V value.

Even if you don't want chest thump to the back of the room, and it's not a R&R band, but still want nice fat bass and kick drum, you're still going to be up there in dB output due to the loss over distance.

Hope this makes sense as is understandable...

edit:
You may think the answer is to bridge with the amp you're looking at.
2000W/4ohms = 89.4V. Somehow, you have to find a way all of a sudden to limit by 39.4V which may be beyond the capability of your limiter to achieve.

Speaking of limiters, what are you using?

Thanks for the educational reply.

I use a BSS-336 Minidrive as my DSP and I use the limiter in that unit. I guess I'll be looking at a higher powered amp.

yigba wrote:Thanks for the educational reply.

I use a BSS-336 Minidrive as my DSP and I use the limiter in that unit. I guess I'll be looking at a higher powered amp.

No worries.
Honestly, you're not looking for a whole heap more output. If you can find someting that's about 400W/8 ohms you should be fine I reckon...

Grant's reply is completely correct. Running amplifiers at their rated max is usually not a good idea. Except in this case. It's one of the reasons I went to Ashly. They will run 2 ohm loads all day long and not sweat. I know of several users who routinely run 2 ohms and have for a couple of years at many many gigs.

They are overbuilt and underspec'd by most standards.

Leland -are you saying this amp would work for 2 T39's without bridging? Have you ever done a voltage test on the KLR 2000 to see what the max was?

By the way - you built (or I think your son did) the T39's for me two summers ago.

I haven't, but I can. There's one sitting in my shop.

I'd appreciate if you could do that for me.

Bumping the clip lights right at 49 volts with pseudo noise. Just the meter, no load.

For anyone who wants to know -just picked up this amp (used) and it has a great power reducing feature. In bridge mode if you switch the input sensitivity from 1 volt to 26db the max voltage prior to clipping is around 72 volts. Perfect for a pair of T39's with some limiting.