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[Mark Wilkinson]

.....do you think the 4x3.5k would push 4 orbit shifters (2 per channel) along with the 3tx noesis without any problems or would the 12000hd be better to push 4 orbit shifters alone...keep in mind my orbit shifters are 4ohm...or just get 2 i tech hd 4x3.5k like you recommend?

Not trying to answer for Tim, who will no doubt have a broader, better perspective.......
 
but I wouldn't expect 4 ohm orbit shifters, to work real well 2 per channel on the 4x3500.
Looking closer at the specs, per channel 20-20k power is only 2100W @ 2 ohms. 
Using Jeff's 85v RMS limiting recommendation, you're gonna want the amp to give each OS 1800W for at least 2 seconds.

It's probably also worth noting Jeff's 4 ohm peak limiting recommendation calls for 7200W @ 20ms.
So even with one 4ohm OS per channel, the 4x3500 comes up short of banging peak for 20ms...(which ain't necessarily a bad thing

Given the price of amps you're looking at, did you consider the Dyna ?

[Ron Ventour]

Not trying to answer for Tim, who will no doubt have a broader, better perspective.......
 
but I wouldn't expect 4 ohm orbit shifters, to work real well 2 per channel on the 4x3500.
Looking closer at the specs, per channel 20-20k power is only 2100W @ 2 ohms. 
Using Jeff's 85v RMS limiting recommendation, you're gonna want the amp to give each OS 1800W for at least 2 seconds.

It's probably also worth noting Jeff's 4 ohm peak limiting recommendation calls for 7200W @ 20ms.
So even with one 4ohm OS per channel, the 4x3500 comes up short of banging peak for 20ms...(which ain't necessarily a bad thing

Given the price of amps you're looking at, did you consider the Dyna ?

Ok not sure I understand the 2nd and 3rd paragraph but I’m guessing it’s because the 4x3500 @2ohms (2 4ohm Orbit Shifters on the same channel) will only get 3500watts and won’t be enough to push the 2 os? and you are also saying even one 4ohm OS per channel the 4x3500 amp still wont be enough? what about the 1200hd or a powersoft k10 or k20?

[Mark Wilkinson]

Ok not sure I understand the 2nd and 3rd paragraph but I’m guessing it’s because the 4x3500 @2ohms (2 4ohm Orbit Shifters on the same channel) will only get 3500watts and won’t be enough to push the 2 os? and you are also saying even one 4ohm OS per channel the 4x3500 amp still wont be enough? what about the 1200hd or a powersoft k10 or k20?

Hi Ron, I'll try to be a little clearer.
Yes, I was talking about a pair of your 4 ohm OS's putting a  2 ohm load on a single 4x3500 channel.
And then looking deeper into the manual's amps specs.....

See how the 2-ohm 3500W is a 1 kHz 20ms Burst spec ?
versus only 2100W for 20Hz -20 kHz ?

My take is 2100W is all the amp really has to give, for sub duty at 2 ohms......

As far as one OS per channel, that's not a bad fit IMO. 
The amp makes more, 2400W, than where Jeff recommends RMS limiting (see link earlier in thread)
I was just commenting that the burst rating at 4 ohms is less than Jeff's peak recommendation (a little underpowered, but no prob IMO.)

Just to be able to reach peak voltage limiting, and see how it sounds, I've used Jeff's RMS and peak limiting recommendations with all 4 channels of a PLD4.5 configured in bridged/parallel mode (4200W cont; 7500W peak per QSC)........the OS was awesome sounding!

If you'll look at the HD12000 manual, you'll see a channel is good for 3500W into 2 ohms. Better !
I'm not sure how to interpret the Powersoft 'Maximum Output" specs, but the amps sure have a hell of a good reputation, huh?
So does the Danley Dyna /Linea......

[Nathan Riddle]

If it was me I'd do powersoft or Danley/linea better day/limiter sections. More power, etc.

[Ron Ventour]

Hi Ron, I'll try to be a little clearer.
Yes, I was talking about a pair of your 4 ohm OS's putting a  2 ohm load on a single 4x3500 channel.
And then looking deeper into the manual's amps specs.....

See how the 2-ohm 3500W is a 1 kHz 20ms Burst spec ?
versus only 2100W for 20Hz -20 kHz ?

My take is 2100W is all the amp really has to give, for sub duty at 2 ohms......

As far as one OS per channel, that's not a bad fit IMO. 
The amp makes more, 2400W, than where Jeff recommends RMS limiting (see link earlier in thread)
I was just commenting that the burst rating at 4 ohms is less than Jeff's peak recommendation (a little underpowered, but no prob IMO.)

Just to be able to reach peak voltage limiting, and see how it sounds, I've used Jeff's RMS and peak limiting recommendations with all 4 channels of a PLD4.5 configured in bridged/parallel mode (4200W cont; 7500W peak per QSC)........the OS was awesome sounding!

If you'll look at the HD12000 manual, you'll see a channel is good for 3500W into 2 ohms. Better !
I'm not sure how to interpret the Powersoft 'Maximum Output" specs, but the amps sure have a hell of a good reputation, huh?
So does the Danley Dyna /Linea......

ok i understand now, thanks for the explanation..been reading up on the powersoft, lab gruppen and linea amps they seem to do a better job @2ohms than the crown hd...need a little more info on the lab fp14000..you see alot of these on those big sound systems in jamaica for bass...

[Steve Litcher]

I'd also give Jeff a call or send him an e-mail - he won't steer you wrong and has a ton of experience with various amps and people's experiences. I believe he has several PLM10000Q amps at the shop.

[Tim McCulloch]

ok i understand now, thanks for the explanation..been reading up on the powersoft, lab gruppen and linea amps they seem to do a better job @2ohms than the crown hd...need a little more info on the lab fp14000..you see alot of these on those big sound systems in jamaica for bass...

ITech amps are designed for maximum output at 4 ohms.  Running subs at 2 ohms is not recommended as a matter of general practice and why I indicated earlier that doing so should be considered only in "limping along" circumstances.

[Ivan Beaver]

ITech amps are designed for maximum output at 4 ohms.  Running subs at 2 ohms is not recommended as a matter of general practice and why I indicated earlier that doing so should be considered only in "limping along" circumstances.

Another consideration about running at 2 ohms vs 4 ohms (no matter what amp) is the power loss over the cable is twice as much at 2 ohm vs 4 ohms.  And 4 times the loss at 8 ohms.

[Ron Ventour]

I'd also give Jeff a call or send him an e-mail - he won't steer you wrong and has a ton of experience with various amps and people's experiences. I believe he has several PLM10000Q amps at the shop.

thanks sure will

[Ron Ventour]

ITech amps are designed for maximum output at 4 ohms.  Running subs at 2 ohms is not recommended as a matter of general practice and why I indicated earlier that doing so should be considered only in "limping along" circumstances.

gotha tim..thanks

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