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Title: What do you Bi-amp with?
Post by: Ian Coughlin on August 20, 2010, 01:45:46 pm
Recently I've been debating my SRX715's.  In my research I have noticed that there aren't any amps in the same range (iTech, PL3's, etc.) that would meet the power requirements for the HF and LF selection of any speaker.  Example I have SRX715's, I would need an iTech 6000 for the LF and a XTi1000 for the HF selection.  I don't know if its because I'm anal and like matching amps or the increased functionality of and iTech over an XTi. It bothers me that I can't have an iTech power my HF (I know I can get an IT4000 and limit the RMS but that wouldn't be a rational decision).  Why don't any of these companies make a lower powered amp in their "flagship" series amp lines?
Title: Re: What do you Bi-amp with?
Post by: RYAN LOUDMUSIC JENKINS on August 20, 2010, 02:08:23 pm
I think that the IT4000 or even IT6000 IS a rational decision for all frequency bands, including your highs.  Your HF drivers/horns are so efficient that you would almost never get to the program rating of the drivers anyways because it would be way too loud.  I use Camco Vortex 6 amp on all the frequency bands and I have never ever had an issue.  Thats about 1350 watts available to the HF drivers and my drivers are only rated at 80 Watts RMS.  I have my limiters set for 160 watts and I have never seen the limit light flicker on my DSP.

As far as the manufacturers making lower power versions of their flagship amps, I don't think that there would be enough of a cost difference to the end user to warrant making the amps less powerful when the bigger amps work just fine for the lower power applications.
Title: Re: What do you Bi-amp with?
Post by: Tom Reid on August 20, 2010, 02:09:25 pm
Ian Coughlin wrote on Fri, 20 August 2010 12:45

Recently I've been debating my SRX715's.  In my research I have noticed that there aren't any amps in the same range (iTech, PL3's, etc.) that would meet the power requirements for the HF and LF selection of any speaker.  Example I have SRX715's, I would need an iTech 6000 for the LF and a XTi1000 for the HF selection.  I don't know if its because I'm anal and like matching amps or the increased functionality of and iTech over an XTi. It bothers me that I can't have an iTech power my HF (I know I can get an IT4000 and limit the RMS but that wouldn't be a rational decision).  Why don't any of these companies make a lower powered amp in their "flagship" series amp lines?


I bi-amp with XTIs.  It get's a little tricky, even with internal DSPs as the XTIs all have a different gain.
I run my SRX 725s off an XTI6000 for mids,and XTI1000 for tops.  
If you look at the way Crown and JBL setup the DSP parameters for XTI and Itech, they suggest using (for example) 1/2 and IT 4000 for mids, the other for highs.  This solves the gain issue as the DSP preset programs the correct gain for each.  It also indicates that you 'can' use an IT4000 for SRX horns, just be gentle!

As far as using an XTI1000 for tops, the amp runs at an 8 ohm load and never passes %60 input/output (in my situation).  The amp doesn't work that hard, the output is clean, and the sound is so much better than the padded passive crossover.

ymmv.
Title: Re: What do you Bi-amp with?
Post by: Tim Brackett on August 20, 2010, 04:51:56 pm
I bi-amp my VRX boxes, 2/side, with an XTi1000 for the highs and an iT6000 for the lows.  I just took the gain difference in account an made it up in the bandpass gain of the crossover.  It is just not worth 3 times the cost and several more pounds to me to have the amps match.  The XTi does great on the highs and is the last amp in my rig I have to watch when pushing the system.
Title: Re: What do you Bi-amp with?
Post by: Matt Vivlamore on August 20, 2010, 04:54:38 pm
While I don't use the SRX tops, I plan on Bi-Amping my QRx212s with 2 IT4000s.  Just incase one of the IT amps goes down, I can flip a few switches & settings and run the night in Passive for the show.
Title: Re: What do you Bi-amp with?
Post by: Ian Coughlin on August 21, 2010, 02:24:39 pm
Good input from all.  I like the idea of having redundancy, going with two iTechs.  I also like the feasibility of an XTi1000 at the moment and knowing that it can "comfortably" power the HF sections of any JBL box that i own or plan on upgrading to (SRX/VRX).

As far as processing goes, do you use the amps internal DSPs and daisy chain them or do you have a processor (DR260, etc.) in the mix?  Or use a mix of both?
Title: Re: What do you Bi-amp with?
Post by: Silas Pradetto on August 22, 2010, 07:03:58 am
Tim Brackett wrote on Fri, 20 August 2010 16:51

I bi-amp my VRX boxes, 2/side, with an XTi1000 for the highs and an iT6000 for the lows.  I just took the gain difference in account an made it up in the bandpass gain of the crossover.  It is just not worth 3 times the cost and several more pounds to me to have the amps match.  The XTi does great on the highs and is the last amp in my rig I have to watch when pushing the system.


What everyone is forgetting is that different DSP amps have different latencies that need to be compensated for in the phase alignment of the crossover. I don't think the XTi latency is published but the Itech is.

In comparison to the feature set of an Itech, the XTis appear to be a heap of garbage, and usually sound like it too...

And if you use a DSP amp with an external DSP then you're missing the point. With possibly the exception of using the AES digital inputs on the Itechs to avoid the extra AD/DA conversion.
Title: Re: What do you Bi-amp with?
Post by: Bob Josjor on August 22, 2010, 11:34:24 am
Tom Reid wrote on Fri, 20 August 2010 12:09

   

I bi-amp with XTIs.  It get's a little tricky, even with internal DSPs as the XTIs all have a different gain.



You know, occassionally I get a little crap for having all Peavey amps in my rig, but I think most people would have to agree that at least Peavey has the forethought to make ALL their amplifiers with the same gain.  It sure makes things a lot easier and makes a helluva lot more sense.
Title: Re: What do you Bi-amp with?
Post by: Tom Reid on August 22, 2010, 11:55:47 am
Silas Pradetto wrote on Sun, 22 August 2010 06:03

Tim Brackett wrote on Fri, 20 August 2010 16:51

I bi-amp my VRX boxes, 2/side, with an XTi1000 for the highs and an iT6000 for the lows.  I just took the gain difference in account an made it up in the bandpass gain of the crossover.  It is just not worth 3 times the cost and several more pounds to me to have the amps match.  The XTi does great on the highs and is the last amp in my rig I have to watch when pushing the system.


What everyone is forgetting is that different DSP amps have different latencies that need to be compensated for in the phase alignment of the crossover. I don't think the XTi latency is published but the Itech is.

In comparison to the feature set of an Itech, the XTis appear to be a heap of garbage, and usually sound like it too...

And if you use a DSP amp with an external DSP then you're missing the point. With possibly the exception of using the AES digital inputs on the Itechs to avoid the extra AD/DA conversion.


Johnny scrimped and saved for 2 years to buy his first XTI.
He's been longing for an ITECH but just can't get the cash together.
He's so proud of his first purchase that he made a new account on PSW to talk with real people about his amp.
Then he saw Silas post telling him that his new purchase is garbage.
Four years back in therapy for Johnny.

When one has a point they're trying to get across, they sound more intelligent if they don't bash things.
Title: Re: What do you Bi-amp with?
Post by: Silas Pradetto on August 23, 2010, 03:22:36 pm
Tom Reid wrote on Sun, 22 August 2010 11:55

Silas Pradetto wrote on Sun, 22 August 2010 06:03

Tim Brackett wrote on Fri, 20 August 2010 16:51

I bi-amp my VRX boxes, 2/side, with an XTi1000 for the highs and an iT6000 for the lows.  I just took the gain difference in account an made it up in the bandpass gain of the crossover.  It is just not worth 3 times the cost and several more pounds to me to have the amps match.  The XTi does great on the highs and is the last amp in my rig I have to watch when pushing the system.


What everyone is forgetting is that different DSP amps have different latencies that need to be compensated for in the phase alignment of the crossover. I don't think the XTi latency is published but the Itech is.

In comparison to the feature set of an Itech, the XTis appear to be a heap of garbage, and usually sound like it too...

And if you use a DSP amp with an external DSP then you're missing the point. With possibly the exception of using the AES digital inputs on the Itechs to avoid the extra AD/DA conversion.


Johnny scrimped and saved for 2 years to buy his first XTI.
He's been longing for an ITECH but just can't get the cash together.
He's so proud of his first purchase that he made a new account on PSW to talk with real people about his amp.
Then he saw Silas post telling him that his new purchase is garbage.
Four years back in therapy for Johnny.

When one has a point they're trying to get across, they sound more intelligent if they don't bash things.


Maybe I was getting a bit grumpy after being awake for 25 hours at a really tough gig Laughing

Anyhow, XTis have their place, but running them with Itechs really is a bad idea due to the delay problems.

Also, if you compare the feature set of the two amps, it will in fact seem like the XTi is severely lacking, just like I said as my grumpy self.

I am always extremely surprised at the number of people that buy DSP amps and then run them with their external DSP anyway. I'm not saying that anyone in this thread is doing it, but don't these people realize that they are experiencing a severe sound quality hit when they do this?

And, I don't see the problem using Itechs to power HF drivers at all. I routinely biamp cabinets with one Itech per, and it makes lots of sense. XTis don't have the capability to be deployed and managed in any sort of large numbers (like more than 1 rack full) because they don't have Ethernet.

Also consider that your 75 watt HF driver may be able to withstand a 500 watt peak with no issue--there usually isn't an excursion problem like with woofers because of the higher frequency.

I think it was Sound Image that uses Itech 8000s on everything, even the HF in their wedges.

I'll try to be happier after getting my 23 hours of sleep Laughing
Title: Re: What do you Bi-amp with?
Post by: Ian Coughlin on August 23, 2010, 04:13:53 pm
Silas,
So you daisy chain all your iTechs... what do you use for feedback elimination/control?
Title: Re: What do you Bi-amp with?
Post by: E. Lee Dickinson on August 23, 2010, 05:19:04 pm
Ian Coughlin wrote on Mon, 23 August 2010 16:13

Silas,
So you daisy chain all your iTechs... what do you use for feedback elimination/control?


Not to answer for Silas, but I use my FOH EQ (in the board, in my case) for feedback control. Doing that in the system processors would seem like kindof a PITA.
Title: Re: What do you Bi-amp with?
Post by: Rob Spence on August 23, 2010, 05:38:23 pm
E. Lee Dickinson wrote on Mon, 23 August 2010 17:19

Ian Coughlin wrote on Mon, 23 August 2010 16:13

Silas,
So you daisy chain all your iTechs... what do you use for feedback elimination/control?


Not to answer for Silas, but I use my FOH EQ (in the board, in my case) for feedback control. Doing that in the system processors would seem like kindof a PITA.

And in the analog world, the graphic eq that you have for each mix.
DSP (formally known as Speaker Processors) doesn't (in my opinion) replace controls at the mix position. Many people seem to think that because a DSP advertises all sorts of features, you have to use them all or you are wasting them  Confused
Title: Re: What do you Bi-amp with?
Post by: Tom Reid on August 23, 2010, 07:59:51 pm
I'llhave to check my alignment,I'm triamping with XTI1000,XTI6000, and Itech6000.  Using the DSP on all.

As far as controlling them,I think the max I can run would be 254 with a USB>>Ethernet bridge.
Title: Re: What do you Bi-amp with?
Post by: Todd Rasmussen on August 24, 2010, 10:56:27 pm
My old garage system SR4732A with a QSC PL3.4 on lows, PL236 on highs, DCX2496 handling that and subs.
Title: Re: What do you Bi-amp with?
Post by: Todd Rasmussen on August 24, 2010, 10:56:40 pm
My old garage system SR4732A with a QSC PL3.4 on lows, PL236 on highs, DCX2496 handling that and subs.
Title: Re: What do you Bi-amp with?
Post by: Bennett Prescott on August 24, 2010, 11:12:46 pm
Ian Coughlin wrote on Fri, 20 August 2010 13:45

I know I can get an IT4000 and limit the RMS but that wouldn't be a rational decision

Why not?

HF drivers need very low power from amplifiers with very high voltage rails. The logical solution is to limit for long term power so you don't burn up the voice coil, and provide a big enough amp to meet the excursion capabilities of the driver. An XTI 1000 is really pretty baseline in this regard, at least for good pro drivers.

Sorry if someone already covered this, I just skimmed the rest of this post.

P.S. Look at the impedance curve of your HF driver and think about just how much of that voltage is being turned into actual heating power, especially at the top end of the HF response. Not much!

P.P.S. For instance, here is a screenshot of the impedance curve for a 1" exit, 1.7" voice coil HF driver rated for 60W AES that I work with a lot. That driver is powered by an amplifier capable of delivering 330w to it. Up at the top of its response that amplifier would be clipping its rails pretty hard trying to deliver even half that.

index.php/fa/32205/0/
Title: Re: What do you Bi-amp with?
Post by: Craig Smith on August 25, 2010, 12:06:11 am
Bennett Prescott wrote on Tue, 24 August 2010 20:12

P.P.S. For instance, here is a screenshot of the impedance curve for a 1" exit, 1.7" voice coil HF driver rated for 60W AES that I work with a lot. That driver is powered by an amplifier capable of delivering 330w to it. Up at the top of its response that amplifier would be clipping its rails pretty hard trying to deliver even half that.


Sorry, I'm not sure I understand.  Are you saying the amplifier can only deliver 165W because the impedance at the top end is double the nominal impedance?  But the speaker is only rated for 60W, so is that a problem?

Thanks.
Title: Re: What do you Bi-amp with?
Post by: Craig Smith on August 25, 2010, 12:09:53 am
Am I crazy to want an amp with 2 differently-sized channels?  I would like a single amp devoted to a single speaker so I can put it near the speaker and avoid long cables.
Title: Re: What do you Bi-amp with?
Post by: Bennett Prescott on August 25, 2010, 12:24:02 am
Craig Smith wrote on Wed, 25 August 2010 00:09

Am I crazy to want an amp with 2 differently-sized channels?  I would like a single amp devoted to a single speaker so I can put it near the speaker and avoid long cables.

http://www.crownaudio.com/pdf/legacy/134168.pdf
Title: Re: What do you Bi-amp with?
Post by: Bennett Prescott on August 25, 2010, 12:41:57 am
The speaker is rated for 60W long term. Consider 12dB crest factor, which is hardly uncommon in live music. That 60W RMS has peaks of nearly 500 "watts". To reproduce this signal that the driver can handle thermally, you need an amplifier at least that big.

This is all confused because amplifiers actually supply voltage. How many watts of power that creates depends on the load.
Title: Re: What do you Bi-amp with?
Post by: Craig Smith on August 25, 2010, 10:47:41 am
Bennett Prescott wrote on Tue, 24 August 2010 21:41

The speaker is rated for 60W long term. Consider 12dB crest factor, which is hardly uncommon in live music. That 60W RMS has peaks of nearly 500 "watts". To reproduce this signal that the driver can handle thermally, you need an amplifier at least that big.

This is all confused because amplifiers actually supply voltage. How many watts of power that creates depends on the load.


OK, got it, thanks! But aren't amps also rated at RMS?

Anyway, yeah, I've wondered about the value of wattage specs, since speaker impedance varies so much.
Title: Re: What do you Bi-amp with?
Post by: Craig Smith on August 25, 2010, 10:50:14 am
Bennett Prescott wrote on Tue, 24 August 2010 21:24[url

http://www.crownaudio.com/pdf/legacy/134168.pdf[/url]


Interesting, exactly!
Title: Re: What do you Bi-amp with?
Post by: Bennett Prescott on August 25, 2010, 02:55:39 pm
Craig Smith wrote on Wed, 25 August 2010 10:47

OK, got it, thanks! But aren't amps also rated at RMS?

Yes, usually (always?) a sine wave (3dB crest factor) into a load, driven to the onset of clip. How clipping is defined varies by method.

Speakers can be rated any number of ways, but the usual method is AES, which IIRC is band-limited pink noise with 6dB crest factor.
Title: Re: What do you Bi-amp with?
Post by: Daniel Postilnik on February 07, 2011, 11:55:51 am
Does the Crown XLS drivecore series dsp include limiting of watts? So far I've only seen that it can limit based on the input level, like "-2db" or whatever it may be. Is this the same thing?
Title: Re: What do you Bi-amp with?
Post by: Silas Pradetto on February 07, 2011, 12:21:16 pm
Daniel Postilnik wrote on Mon, 07 February 2011 11:55

Does the Crown XLS drivecore series dsp include limiting of watts? So far I've only seen that it can limit based on the input level, like "-2db" or whatever it may be. Is this the same thing?


There is no way to DSP limit watts unless the amplifier can do real-time impedance analysis of the load, or somehow compare the current and voltage waveforms being sent to the speaker. Usual amplifier and DSP limiters are entirely based on voltage, even the Itech limiters that use watts (they actually ask for nominal impedance and watts, and calculate voltage based on that).

Theoretically, voltage (and therefore wattage) could be calculated using "-2dB" limiters, but it wouldn't be easy, or particularly accurate.

The attack, release, ratio, and other specifics of the limiter would also influence its effectiveness, and whether it was more of a "peak" or "rms" limiter.