Intro to bi-/tri-amping

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Daniel Postilnik

Junior
Jan 14, 2011
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San Francisco, CA
Seeing as how I can't afford the a rig I want yet, I figured I would spend some time learning how to use it!



Specifically I'm wondering about different drivers in a cabinet outputting signal at different levels because they're powered with different. I know the loudspeaker has recommended amp power for each driver, but how else would I ensure a balance between the two, other than by ear? Will speaker processor settings from the manufacturer provide info about this?



Thanks!
 
Re: Intro to bi-/tri-amping

Daniel Postilnik wrote on Sat said:
Seeing as how I can't afford the a rig I want yet, I figured I would spend some time learning how to use it!



Specifically I'm wondering about different drivers in a cabinet outputting signal at different levels because they're powered with different. I know the loudspeaker has recommended amp power for each driver, but how else would I ensure a balance between the two, other than by ear? Will speaker processor settings from the manufacturer provide info about this?



Thanks!
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Typically, if the speaker has "processor settings" they will list passband levels that indicate how much more or less gain the highs, mids, and lows need.



Most manufacturers assume you will use amplifiers with matched gain. I.e. 30dB gain on all pass bands. If they don't match, you can adjust that in the crossover (with additional changes to passband levels) or by using the attenuator knobs on the front of the amp.
 
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Re: Intro to bi-/tri-amping

One of the first QSC products I bought was a combination stereo crossover/HF amp (X1.2? I still have it, somewhere). The owners manual had a very concise explanation of how to compute pass-band levels based on component sensitivity (1w/1meter) and amplifier gain. QSC may still have that information on their web site.



If I were faced with speakers & amps I'd not used before and the crossover was ''zeroed-out'', I'd hook it all up, guestimate crossover points, send pink noise to the subs or LF and run it until the amp clipped or speakers reached their excursion limit, and back down a bit. Whip out the Rat Shack SPL meter, note the level, and turn off the LF and bring up the next pass band. With any luck it will achieve at least as much SPL as the previous band, and then move to the next pass band. This is fast and dirty; the pink noise keeps you from making decisions based on the spectral content of the music. It's meant only to get in the ballpark, not make definitive decisions.



None of that procedure will deal with what happens at the *acoustic crossover*, but it's a place to start.



Have fun, good luck.



Tim Mc
 
Re: Intro to bi-/tri-amping

I guess I should just specify what amp-speaker combination I would be planning to use.



EV Deltamax 1152 (one or two per side)

HF - Manual recommends ''125-250 watts continuous into 8 ohms''

Amp: Crown XLS 2500 (775w @ 4ohms, 440w @ 8ohms)



LF - Manual recommends ''600-1,200 watts continuous into 8 ohms''

Crown XTi 4000 (625w @ 8ohms, 1200w @ 4 ohms)



I've already heard all the bashing about the Xtis, so spare me please. I think they're ok power-rating-wise for the woofer, but do I stand a chance of blowing out the compression driver with the xls 2500?



Thanks!
 
Re: Intro to bi-/tri-amping

Daniel Postilnik wrote on Mon said:
I guess I should just specify what amp-speaker combination I would be planning to use.



EV Deltamax 1152 (one or two per side)

HF - Manual recommends ''125-250 watts continuous into 8 ohms''

Amp: Crown XLS 2500 (775w @ 4ohms, 440w @ 8ohms)



LF - Manual recommends ''600-1,200 watts continuous into 8 ohms''

Crown XTi 4000 (625w @ 8ohms, 1200w @ 4 ohms)



I've already heard all the bashing about the Xtis, so spare me please. I think they're ok power-rating-wise for the woofer, but do I stand a chance of blowing out the compression driver with the xls 2500?



Thanks!
Click to expand...



You probably won't blow the compression driver with the XLS2500. Even though the power rating seems high, the driver will appreciate the extra voltage. Usually, if you don't hear distortion you'll be OK. The only time an issue could arise is if there is a big feedback squeal or other impulsive sound that could blow the driver, or at least damage it. This is why limiters are a good idea, but they have to be properly set.



Also, why are you mixing DSP amplifiers and regular amps? This makes no sense. You don't want to use an external DSP with the XTis; they are already noisy enough and the additional AD/DA stage won't help you at all. Might as well pick up an XTi1000 for $200 for the HF, and use internal XTi DSP. Heck, you could probably sell your external DSP and other amp and recoup the cost anyway.
 
Re: Intro to bi-/tri-amping

Daniel Postilnik wrote on Mon said:
I guess I should just specify what amp-speaker combination I would be planning to use.



EV Deltamax 1152 (one or two per side)

HF - Manual recommends ''125-250 watts continuous into 8 ohms''

Amp: Crown XLS 2500 (775w @ 4ohms, 440w @ 8ohms)



...but do I stand a chance of blowing out the compression driver with the xls 2500?!
Click to expand...



You certainly run a risk, yes, if you don't have proper limiting in place. By proper limiting, I mean two-stage limiting to keep both rms and peak power under control. The long term power handling/rms of the HF driver is only 75 watts. So ~150 watts would be considered program power. The driver is rated for short term (peak) power of 300 watts, or 4x the rms rating. At 440W without proper limiting in place, it's more than possible to cook the driver. You need a processor that has the ability to do 2-stage limiting. As far as I know, the BSS Minidrives are the least expensive processor that will do this.



Greg
 
Re: Intro to bi-/tri-amping

Silas, I'm a bit confused by your response. I thought both of these amps had dsp capabilities. Are you saying I shouldn't use the onboard dsp on either amps? I didn't mention any outboard dsp, though the only thing involved most likely would be an ashly 3.24CL.



Regarding the xti1000, other than being better-matched for hf in terms of power output, how else would I benefit from switching?
 
Re: Intro to bi-/tri-amping

If the BSS is out of the price range - which it is for a lot of people. I find that the Ashly Protea 3.6Sp is a great unit for the $$. We have them on our 3 way systems and on our biamp monitor racks and have had -0- failures. Although the limiting scheme is not as comprehensive as the BSS it works really well at about 1/2 the money. The other thing you will need is a 3-Way Rack Panel to get all your multi amp outputs out tio the speakers and make for a clean set up - you can build them or buy them but either way you need one and should make sure you think about that when budgeting



good luck
 
Re: Intro to bi-/tri-amping

Daniel Postilnik wrote on Mon said:
Silas, I'm a bit confused by your response. I thought both of these amps had dsp capabilities. Are you saying I shouldn't use the onboard dsp on either amps? I didn't mention any outboard dsp, though the only thing involved most likely would be an ashly 3.24CL.



Regarding the xti1000, other than being better-matched for hf in terms of power output, how else would I benefit from switching?
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Oops, I didn't realize you were referring to the new XLS Drivecore amps. AFAIK, the DSP in those is essentially useless, only allowing limited crossover and no EQ, am I right?



Mixing DSPs is also a somewhat bad idea, as they could have different latencies which would affect your signal alignment, and depending on what you have to measure with, it could be difficult to compensate for.



In fact, I don't even see a latency spec on the drivecore page, and I am almost sure there are no provisions for EQ. These are a ''DJ'' amplifier, almost completely useless for pro PA use. They might as well not have DSP, because what they have is so limited an external unit MUST be used to get any real features.



So, switching from XLS Drivecore to XTi at least allows you to have a useful amp instead of a pile of junk.
icon_biggrin.gif
 
Re: Intro to bi-/tri-amping

Dan Bouchard wrote on Mon said:
If the BSS is out of the price range - which it is for a lot of people. I find that the Ashly Protea 3.6Sp is a great unit for the $$. We have them on our 3 way systems and on our biamp monitor racks and have had -0- failures. Although the limiting scheme is not as comprehensive as the BSS it works really well at about 1/2 the money.
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That was sort of the point though - using a DSP with peak only limiting will not protect the driver when used with a well oversized amp. I have no doubt the Ashly is a fine processor, but it's not the right tool for proposed setup. You'll have diaphragm toast with a side of bacon if the amp's output averages 1/5 of it's maximum clean power capability. If you're hitting clip at all, you'll have breakfast before the waiter finished taking your order.



Greg

 
Re: Intro to bi-/tri-amping

I can appreciate that...but that is not my experience. We use Crest CA6 on QRX153 Highs and a Crest PRO7200 on highs for a our monitors.... That is well over the power rating for those drivers... these rigs get hammered (we did death angel this week who beat it like a red headed stepchild) and in 5+ years we have had no HF damage. Thats just one mans experience though.
 
Re: Intro to bi-/tri-amping

Quote: said:
I'm wondering about different drivers in a cabinet outputting signal at different levels because they're powered with different. I know the loudspeaker has recommended amp power for each driver, but how else would I ensure a balance between the two, other than by ear?
Click to expand...

Use a voltmeter & test tones to measure/balance level along signal path ( Pre/post crossover and input of respective amps ).

Use SPL meter and swept tones to help find gross disparity
 
Re: Intro to bi-/tri-amping

Dan Bouchard wrote on Mon said:
I can appreciate that...but that is not my experience. We use Crest CA6 on QRX153 Highs and a Crest PRO7200 on highs for a our monitors.... That is well over the power rating for those drivers...
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It's a different scenario. The QRx153 is a 3-way bi-amped box. The MF & HF drivers have an internal crossover which means the HF driver is getting a fraction of the MF power. Also, the HF driver in that box has it's own over-power protection circuit on the crossover. You're only 100W over the program rating of the MF/HF section with the 400W at 8Ω output of the CA6. And the peak power rating (600W) of the MF/HF section falls within the 400W quite easily.



In the case of the DML1152, all of the 440W is plugged into one HF compression driver rated at 75 watts rms with no protection - unless you use the matching processor with sense lines.



Greg
 
Re: Intro to bi-/tri-amping

Greg Cameron wrote on Mon said:
You need a processor that has the ability to do 2-stage limiting. As far as I know, the BSS Minidrives are the least expensive processor that will do this.



Greg
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The BSS minidrives do not allow you to make separate RMS and Peak Limiters. I have a couple and love them! They sound terrific even when the limiters are working hard.



I set my limiters on the Minidrives at the ''Program'' rating of the drivers.



I use Camco Vortex 6 amps for all frequency bands and they are rated at 1350 watts per channel into 8 ohms. My HF drivers are rated at 80/160 Watts. No issues using the higher output amps on HF drivers as long as your gain structure and limiters are set correctly.
 
Re: Intro to bi-/tri-amping

RYAN LOUDMUSIC JENKINS wrote on Mon said:
Greg Cameron wrote on Mon said:
You need a processor that has the ability to do 2-stage limiting. As far as I know, the BSS Minidrives are the least expensive processor that will do this.
Click to expand...



The BSS minidrives do not allow you to make separate RMS and Peak Limiters. I have a couple and love them! They sound terrific even when the limiters are working hard.
Click to expand...



You're correct, I was thinking of the BSS Omnidrives.



RYAN LOUDMUSIC JENKINS wrote on Mon said:
I set my limiters on the Minidrives at the ''Program'' rating of the drivers.



I use Camco Vortex 6 amps for all frequency bands and they are rated at 1350 watts per channel into 8 ohms. My HF drivers are rated at 80/160 Watts. No issues using the higher output amps on HF drivers as long as your gain structure and limiters are set correctly.
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So how are you setting your limiters then? Are you setting them so that they clamp down the voltage when 80 watts is produced? Or at 160 watts? If you're hammering them it must be at the rms level correct? Does that not kill some of the peak output capability then?



Greg
 
Re: Intro to bi-/tri-amping

Greg Cameron wrote on Mon said:
RYAN LOUDMUSIC JENKINS wrote on Mon said:
Greg Cameron wrote on Mon said:
You need a processor that has the ability to do 2-stage limiting. As far as I know, the BSS Minidrives are the least expensive processor that will do this.
Click to expand...



The BSS minidrives do not allow you to make separate RMS and Peak Limiters. I have a couple and love them! They sound terrific even when the limiters are working hard.
Click to expand...



You're correct, I was thinking of the BSS Omnidrives.



RYAN LOUDMUSIC JENKINS wrote on Mon said:
I set my limiters on the Minidrives at the ''Program'' rating of the drivers.



I use Camco Vortex 6 amps for all frequency bands and they are rated at 1350 watts per channel into 8 ohms. My HF drivers are rated at 80/160 Watts. No issues using the higher output amps on HF drivers as long as your gain structure and limiters are set correctly.
Click to expand...



So how are you setting your limiters then? Are you setting them so that they clamp down the voltage when 80 watts is produced? Or at 160 watts? If you're hammering them it must be at the rms level correct? Does that not kill some of the peak output capability then?



Greg
Click to expand...



I don't know exactly how the BSS algorithms work. They are very smooth limiters. What I think happens, only based upon my ears is that they have a soft limiter like an RMS and a brickwall. I set it so that the limiter is set at my ''Program'' rating or double the RMS voltage. The limit light on the meter comes on only on loud portions but I rarely see the ''Over'' LED light up which only comes on during the extreme peaks. There is no breathing or pumping. Even during really loud EDM stuff you won't notice the limiting, they just kinda of stop getting louder. Hope that explains them well enough.



It is hard to match the LEDs on the Minidrives with the LEDs for my Camcos because the Camcos have a multi-color LED that changes from Green to Yellow to Red very fast as you get close to the maximum output. In addition, the Camcos have a feature that actually turns down the input so that the amp itself will not create more than 1% THD. So there is a lot going on. I just did an EDM rental on Saturday for some really fancy DJ named Axwell as the headliner. I had to change the limiters for my subs a little due to it being a different configuration that normal. I ended up setting the limiter approx 1.5-2 dB lower than I would have thought based upon my math but I was still able to get approximately full output on the amp based upon the multicolor LED on the amp on the very loudest peaks.
 
Re: Intro to bi-/tri-amping

Bennett Prescott wrote on Mon said:
RYAN LOUDMUSIC JENKINS wrote on Mon said:
Camcos have a feature that actually turns down the input so that the amp itself will not create more than 1% THD.
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The amp gain is input level dependent?
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The amp has three Gain settings....26dB, 32dB and 1.4Volts sensitivity.



Rather than having a basic peak limiter like other amps have it has a speaker/amplifier protection circuit where in when you push the amp really hard, the circuit will reduce the input level of the amp to keep the amp from having more than 1% ''non-linear'' distortions. It actually compares the input signal to the output signal to do this.



I use this feature on the amp which probably keeps me from getting every single little volt possible out of the amp but If you read Nexo literature they will tell you to NOT use this feature because the NX processors take care of all the processing for you.
 
Re: Intro to bi-/tri-amping

While this is completely off topic....There have been some people in the past that claim the Camcos to be a little weak in the sub bass output. I think it is beacause of this feature keeping them way cleaner sounding than most other amps that makes them seem like they may be a little weak in the subs when in actuality the amps they are comparing them to are just distorting more and they may just like that sound on subs. Who knows for sure?
 
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