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[Tim McCulloch]

Hey everyone, i myself have 2 3tx (90/60 4ohm) version and 2 (4ohm) orbit shifters and to be honest never once used them as yet...been still using my srx800 rig for most of my events so my jtr rig is just sitting there...Looking on advice as to which amps i should get for my jtr rig, i have narrowed it down to either the crown hd 4x3500 to push the entire rig or 1 crown itech hd1200 for the orbit shifters and a hd5000 for the 3tx..or the power soft k8,k10 amps...keep in mind i will be getting 2 more orbit shifters in the future to make 4 total....any advice on the amps would be greatly appreciated..thanks

What are the revenue prospects for the JTR rig?  You have 100% excess capacity with represents 100% loss right now.  If your SRX rig is making money and clients aren't lining up to hand you more money I'd seriously consider why I made the Noesis/OS purchase....

That said, I manage a shop heavily invested in Harman and we're very pleased with our ITech HD 12k amps (we have over 50 of them) and I think they'd do well for you.  The 4x3.5k would do your entire JTR rig right now, 1 sub, 1 3TX per channel.  If you add more 2 more OS later, I'd consider another 4x3.5k to give you some backup - if one of the amps went down you could cut half the subs and go back to the old way or, if you're not doing EDM events you could just run the sub channels with a nominal 2 Ohm load in a pinch.

Jeff at JTR is a very helpful and friendly guy; whatever amps you purchase I suggest calling him and chatting about limiter settings, delay time for the tops, and crossover points.

edit ps:  I would not have purchased the 4 ohm versions.  While it seems like a good idea as amplifiers tend to deliver more current (up to a point) with lower impedance loads, the POWER COMPRESSION of the loudspeakers tends to negate any advantage.  If the woofer in the sub hits the -3dB compression at say, 600 Watts after 10 minutes, shoving more current into the voice coil will not make it louder, it will only overheat the coil and lead to eventual failure of the woofer.  There is this myth (esp. relating to JBL subs) that one needs a huge amount of power reserve to "light them up" or "perform best".  While I greatly appreciate headroom throughout a system it's expensive at the amplifier end.  If you don't mind seeing occasional clip lights on peaks (not on sustained, continuous program like EDM subby stuff) it doesn't make sense to spend $$ on separate HD12k for subs, for example.  If you're doing EDM, you don't want to see a clip light on these big amps as you're very close to re-coning the subs...  When I do dub-type gigs I power limit my subs to around (proprietary number, but it's less than the hypothetical number I used above).  If you're doing live bands that play pop, country, rock and roll... you can take advantage of a larger amplifier's capacity to deliver more transient impact without fear of overheating your sub transducers.

[Ivan Beaver]

When I do dub-type gigs I power limit my subs to around (proprietary number, but it's less than the hypothetical number I used above). 

My general "go to" number for thermal limiting of loudspeakers is 1/4 power, 1/2 voltage of the continuous rating.

This correlates pretty good with the power compression on a voice coil that is not mounted in a magnetic field-from the testing we have done. Of course when it is mounted in a magnetic field, there will be a bit of additional cooling.  But we are looking at worst case.

For typical attack times, I suggest the following:

Large subs 3 seconds
Normal high power woofers 1 second (maybe 2 depending on various factors)
Mids 0.5 seconds
Highs 0.1 second.

NOTE: Your mileage may vary, depending on how the limiters actually react (they are NOT all the same-some not even close to others), what other limiters you have available (peak, continuous, etc) and the rating of the amplifiers vs the speakers hooked up to them.

So yes, once again-it depends.

[Chris Grimshaw]

edit ps:  I would not have purchased the 4 ohm versions.  While it seems like a good idea as amplifiers tend to deliver more current (up to a point) with lower impedance loads, the POWER COMPRESSION of the loudspeakers tends to negate any advantage.

Tim, I'm not sure how you came up with that.

1KW into an 8ohm driver will produce as much heating effect as 1KW into a 4ohm version of that driver. Of course, you don't need as much voltage swing for the latter so a "smaller" amp can be used to achieve the same thermal compression as a "larger" amplifier working on a higher impedance load.

Chris

[Nathan Riddle]

For typical attack times, I suggest the following:

Large subs 3 seconds
Normal high power woofers 1 second (maybe 2 depending on various factors)
Mids 0.5 seconds
Highs 0.1 second.

So yes, once again-it depends.

What about when it is a 2 way or 3 way cab/mains speaker?

Split the difference?

[Jean-Pierre Coetzee]

What about when it is a 2 way or 3 way cab/mains speaker?

Split the difference?

I feel more then likely lowest common denominator.

I'm pretty sure that you will make it sound like balls though if you go anywhere near the limiter.

[David Morison]

Tim, I'm not sure how you came up with that.

1KW into an 8ohm driver will produce as much heating effect as 1KW into a 4ohm version of that driver. Of course, you don't need as much voltage swing for the latter so a "smaller" amp can be used to achieve the same thermal compression as a "larger" amplifier working on a higher impedance load.

Chris

Not that Tim can't explain himself perfectly well, but here's what I took away from it.

If John Q Punter is looking at a speaker that can nominally take 1kW for some amount of time, and was thinking of powering it with an amp which could do say 900W into 8Ω or 1600 into 4Ω (numbers scientifically pulled out of my ass for the sake of the example), he might think that getting the 4Ω version of said speaker would net him more output.

I believe Tim's point is that by the time you're anywhere close to 900W (into a nominally 1kW speaker), adding an extra couple of dB of theoretical extra power by going to the 4Ω version of the speaker is only inviting more power compression.

Of course, if one uses it as an opportunity to save a little £ by buying the next model down in the series of amps, that's another story, with the necessary caveats about being careful to avoid clipping, and having less capacity to double up the number of speakers per channel in the event of a channel going down, etc etc etc.

[Jason Joseph]

My general "go to" number for thermal limiting of loudspeakers is 1/4 power, 1/2 voltage of the continuous rating.

This correlates pretty good with the power compression on a voice coil that is not mounted in a magnetic field-from the testing we have done. Of course when it is mounted in a magnetic field, there will be a bit of additional cooling.  But we are looking at worst case.

For typical attack times, I suggest the following:

Large subs 3 seconds
Normal high power woofers 1 second (maybe 2 depending on various factors)
Mids 0.5 seconds
Highs 0.1 second.

NOTE: Your mileage may vary, depending on how the limiters actually react (they are NOT all the same-some not even close to others), what other limiters you have available (peak, continuous, etc) and the rating of the amplifiers vs the speakers hooked up to them.

So yes, once again-it depends.

What about release times? Or is that depending on the hardware you are using?

[Tim McCulloch]

What about release times? Or is that depending on the hardware you are using?

On long term power limiting for subs - around a 3-4 second attack, 6 second release.

[Ron Ventour]

What are the revenue prospects for the JTR rig?  You have 100% excess capacity with represents 100% loss right now.  If your SRX rig is making money and clients aren't lining up to hand you more money I'd seriously consider why I made the Noesis/OS purchase....

That said, I manage a shop heavily invested in Harman and we're very pleased with our ITech HD 12k amps (we have over 50 of them) and I think they'd do well for you.  The 4x3.5k would do your entire JTR rig right now, 1 sub, 1 3TX per channel.  If you add more 2 more OS later, I'd consider another 4x3.5k to give you some backup - if one of the amps went down you could cut half the subs and go back to the old way or, if you're not doing EDM events you could just run the sub channels with a nominal 2 Ohm load in a pinch.

Jeff at JTR is a very helpful and friendly guy; whatever amps you purchase I suggest calling him and chatting about limiter settings, delay time for the tops, and crossover points.

edit ps:  I would not have purchased the 4 ohm versions.  While it seems like a good idea as amplifiers tend to deliver more current (up to a point) with lower impedance loads, the POWER COMPRESSION of the loudspeakers tends to negate any advantage.  If the woofer in the sub hits the -3dB compression at say, 600 Watts after 10 minutes, shoving more current into the voice coil will not make it louder, it will only overheat the coil and lead to eventual failure of the woofer.  There is this myth (esp. relating to JBL subs) that one needs a huge amount of power reserve to "light them up" or "perform best".  While I greatly appreciate headroom throughout a system it's expensive at the amplifier end.  If you don't mind seeing occasional clip lights on peaks (not on sustained, continuous program like EDM subby stuff) it doesn't make sense to spend $$ on separate HD12k for subs, for example.  If you're doing EDM, you don't want to see a clip light on these big amps as you're very close to re-coning the subs...  When I do dub-type gigs I power limit my subs to around (proprietary number, but it's less than the hypothetical number I used above).  If you're doing live bands that play pop, country, rock and roll... you can take advantage of a larger amplifier's capacity to deliver more transient impact without fear of overheating your sub transducers.

Hi Tim thanks for the reply. I bought the JTR rig mostly for outdoor gigs, the srx boxes sounds excellent indoors but outdoors i felt i needed more of that in your face sound so i sold my srx828 subs and srx835 tops and purchased the orbit shifters and 3tx noesis tops....I kept my srx812 and srx818 boxes for small to med stuff and i have no complaints on that set up....As far as the amps for the jtr rig and i will be getting 2 more orbit shifters by christmas i could not decide on the crown i tech hd,powersoft or lab gruppen for the jtr rig...did a lot of research online and in the forum and many seems to think the crown has a warmer sound and the powersoft delivers more raw power so ive leaned more towards buying the crown amps....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?

[Ron Ventour]

I also have the Noesis 3TX (60x90, 4ohms) and Orbit Shifters. I haven't used them for a lot of gigs at this point but I will confirm that the sound & build quality are first rate. The specs listed are accurate, if not conservative and the service from Jeff is great. My biggest gig with them has been on the top open deck of a cruise ship, 200 people, the artist was playing very intense Trap & Hardstyle EDM and the Noesis were incredibly loud but accurate, while loafing along at about 1/3 power from a Crown XTI6002.

are you using your orbit shifters on the XTI6002 or just the tops? how does the XTI6002 performs on the subs?

[ProSoundWeb Community]