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[Justin Philip]

I just bought a used Itech 4000 on single srx728 cab and I am blown away by how much better it sounds compared to when I had the xti 4000, macrotech 2402, or rmx 2450hd on there!

i am doing my processing through a driverack 260. The amp is bridged.

Can someone help with me how to configure the limiter settings in the ITech? I read every thread it feels like on the board and tried to piece together some stuff.

Found this from an older thread.

ITech Peak limiters at 120v (attack .010sec, release 1 sec)
and RMS at 800w (attack 4 sec, release 6 sec) for my 728's.

Even though the amp is bridged, it still has to options to turn on the limiters for both output channels..I am a little confused on whether I apply the settings to both?

[Jonathan Betts]

Are you running two 728's off one 4000 in bridge mode? I would run one per side in stereo and use the RMS limiters. I use the 4000 on my 728's, one per channel and they perform very well.

[Tim McCulloch]

I just bought a used Itech 4000 for my lonely srx728s and I am blown away by how much better it sounds compared to when I had the xti 4000, macrotech 2402, or rmx 2450hd on there!

i am doing my processing through a driverack 260. The amp is bridged.

Can someone help with me how to configure the limiter settings in the ITech? I read every thread it feels like on the board and tried to piece together some stuff.

Found this from an older thread.
Even though the amp is bridged, it still has to options to turn on the limiters for both output channels..I am a little confused on whether I apply the settings to both?

Yes, you'd apply the settings to both channels.

As for running a pair of 728s, I'd say no.  That's a 2 ohm load in bridged mode.  NO.  Just no.  If this is the way you were running the other amps you mention, I'm not surprised that you're unhappy with their performance and I'm more surprised they lived to tell about it.

Remember that when you go back to stereo mode, you'll need to increase your sub drive level 6dB.  Why?  Bridge mode creates a de facto increase in your input sensitivity of 6dB.

[Scott Carneval]

I believe he's only running one sub.  He even referred to it as 'lonely' haha.

Remember the correct model number is SRX728S.  JBL felt the need to include the 'S' on the end so you would remember it is a subwoofer...in case simply turning it on wasn't enough to tell you. 

[Tim McCulloch]

I believe he's only running one sub.  He even referred to it as 'lonely' haha.

Remember the correct model number is SRX728S.  JBL felt the need to include the 'S' on the end so you would remember it is a subwoofer...in case simply turning it on wasn't enough to tell you.

Good catch.

In which case Justin can keep running in bridge mode. 

[Justin Philip]

Sorry everyone. I clarified in the original post. It's only one sub. I had two single 18 jrx subs (if that's what they want to call that thing) before.

Does the limiter settings I posted in the original post look ok? For learning purposes, how does someone get those numbers? I thought the RMS for the cab was 1600w?

On a related note, when I was setting up the gain structure, DriveRack told me to turn the attenuation up on the amp to 0dB, and set the crossover gain for the sub to -18dB. Does that seem right? I never had to do that before so I ended up putting the crossover gain back to 0db, and set the attenuation on the amp to the level I want.

[Tim McCulloch]

Sorry everyone. I clarified in the original post. It's only one sub. I had two single 18 jrx subs (if that's what they want to call that thing) before.

Does the limiter settings I posted in the original post look ok? For learning purposes, how does someone get those numbers? I thought the RMS for the cab was 1600w?

On a related note, when I was setting up the gain structure, DriveRack told me to turn the attenuation up on the amp to 0dB, and set the crossover gain for the sub to -18dB. Does that seem right? I never had to do that before so I ended up putting the crossover gain back to 0db, and set the attenuation on the amp to the level I want.

I use an empirical measurement to get the RMS limits.  If I told you how, I'd have to kill you... .  Seriously, that's a part of how I make my salary and I don't think my boss would appreciate my discussing it.  If you run only rock and roll kick drum and bass guitar (i.e. not EDM), you can probably raise the RMS limit above what I use, but the chances are you'll never see it kick in at 800w.  The attack time is far too slow for rock and roll.  You're much more likely to hit the peak limiters, and if you find yourself constantly into the peak limiter you probably need More Rig for the Gig.

I can't speak for how the DR wizard arrives at its suggestions, but remember that in bridge mode you pick up an extra 6dB of input sensitivity, so that might account for some of it.  It's also possible that the sub outruns a single top, but since we don't know what you're using for tops, I'm only guessing.

In the XTI preset (and in the I Tech device file I created for the 728/725 combination) the tops and sub amps are assumed to have the same gain, and as I note above, by bridging you change that by 6dB.  At any rate, in the preset the subs are about 2dB hotter at the pass band output relative to the top box.  The DR wizard wanting you to set the sub output at -18 makes no sense to me.  What changes are you making at the power amp input attenuators?

In System Architect, you can change the input sensitivity of the amp by clicking on the "Source" radio button in the Input frame, and I suggest you first set the input sensitivity to match whatever amp you are using for the tops, then use the down arrow in the Analog Source window to lower the input sensitivity to 6dB lower than the top box amp.

[Justin Philip]

I use an empirical measurement to get the RMS limits.  If I told you how, I'd have to kill you... .  Seriously, that's a part of how I make my salary and I don't think my boss would appreciate my discussing it.  If you run only rock and roll kick drum and bass guitar (i.e. not EDM), you can probably raise the RMS limit above what I use, but the chances are you'll never see it kick in at 800w.  The attack time is far too slow for rock and roll.  You're much more likely to hit the peak limiters, and if you find yourself constantly into the peak limiter you probably need More Rig for the Gig.

I can't speak for how the DR wizard arrives at its suggestions, but remember that in bridge mode you pick up an extra 6dB of input sensitivity, so that might account for some of it.  It's also possible that the sub outruns a single top, but since we don't know what you're using for tops, I'm only guessing.

In the XTI preset (and in the I Tech device file I created for the 728/725 combination) the tops and sub amps are assumed to have the same gain, and as I note above, by bridging you change that by 6dB.  At any rate, in the preset the subs are about 2dB hotter at the pass band output relative to the top box.  The DR wizard wanting you to set the sub output at -18 makes no sense to me.  What changes are you making at the power amp input attenuators?

In System Architect, you can change the input sensitivity of the amp by clicking on the "Source" radio button in the Input frame, and I suggest you first set the input sensitivity to match whatever amp you are using for the tops, then use the down arrow in the Analog Source window to lower the input sensitivity to 6dB lower than the top box amp.

Hey Tim, you can tell me and then kill me. At least I would die knowing haha.

So the tops are Turbosounds single 15 cabs, 300w rms @ 8ohms powered by an XTi 4000 (650w stereo). Sensitivity (volts RMS) for full rated power at 4 ohms = 1.4V.

After setting the driverack crossover gains to 0db, the top amp (xti) attenuator is at 3 o clock position, and Itech is at -8db. Nothing is clipping and the system sounds balanced with music.

Subs are actually used 99% of the time for kick drum and bass guitar reinforcement in a typical rock music scenario.

Thanks a lot for your help. You must be on other forums too because you're everywhere. :-)

[Tim McCulloch]

Ooops....

will repost this when I can re write it.

[Matt Vivlamore]

I would un-bridge the IT4000 for the SRX728 and run the pre-set from JBL/Crown for the SRX718/SRX728 subs.

The IT4000 has enough power to drive the 728 in “dual” mode.