I have a crown XTi 2000 and 2 SRX828 subs. One sub is powered, the other is not. The XTi 2000 is rated at 800W @ 4 ohms per ch, the SRX828S is rated at 1200W @ 4 ohms. To utilize the full power of this sub with the XTi2000 I was thinking of putting the XTi 2000 in Bridge-Mono mode, which according to the manual outputs 1950W @ 4 ohms in a single channel.
1. Is it advised to do that? One sound guy told me I could break the amp in the long-run. But since this is an official mode supported by the manufacturer and also I won't use the full 1950W of power, why would I break the amp?
2. How much dB should I remove in the amp's DSP settings to make sure I won't overload the sub, which is only able to handle 1200W?
Thanks
1. Is it advised to do that? One sound guy told me I could break the amp in the long-run. But since this is an official mode supported by the manufacturer and also I won't use the full 1950W of power, why would I break the amp?
2. How much dB should I remove in the amp's DSP settings to make sure I won't overload the sub, which is only able to handle 1200W?
Thanks
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Bridge mode would not affect the amplifier's useful life, but it does restrict the speaker impedance
to 8 ohms or more.
to 8 ohms or more.
I don't understand why, the manual says the output in bridge-mono mode is either 1950W @ 4 ohms or 1600W @ 8 ohms
According to the manual, it can output between 2 ohms and 8 ohms in stereo mode and between 4 ohms and 8 ohms in bridge-mono mode.
Screenshot-2021-07-05-112444 — ImgBB
Screenshot-2021-07-05-112444 — ImgBB
First, the datasheet you link to actually explains that the rated power is measured for only one minute.
This is in my opinion rather short - old fashioned measurements stated a requirement for 30 minutes duration (AES specification? - cannot recall).
Secondly: The specification that the amplifier can only (!) deliver 1950 W in 4 Ohms when capable of delivering 1600 W in 8 Ohms is either a sign that an over current protection is kicking in or that the power supply is what I would call overloaded.
If it is an over current protection, then a normal speaker would most likely give the amplifier a hard time as most socalled 4 ohms speakers will show impedances down to 3 ohms (or even less) at some frequencies.
Given the short duration specified for maximum output I suspect that it is actually a sign that the power supply will be pressed very hard to coexsist with a 4 ohms load.
But if you only use the maximum power rarely and when so only for a few seconds it might be OK.
Still though, I would say it would be pushing it and I would personally settle with 800W from one amplifier channel - the difference is after all only 1.7dB.
And then have an amplifier that easily can cope with the expected lower-than-4-ohms from the speaker.
Cheers,
Martin
This is in my opinion rather short - old fashioned measurements stated a requirement for 30 minutes duration (AES specification? - cannot recall).
Secondly: The specification that the amplifier can only (!) deliver 1950 W in 4 Ohms when capable of delivering 1600 W in 8 Ohms is either a sign that an over current protection is kicking in or that the power supply is what I would call overloaded.
If it is an over current protection, then a normal speaker would most likely give the amplifier a hard time as most socalled 4 ohms speakers will show impedances down to 3 ohms (or even less) at some frequencies.
Given the short duration specified for maximum output I suspect that it is actually a sign that the power supply will be pressed very hard to coexsist with a 4 ohms load.
But if you only use the maximum power rarely and when so only for a few seconds it might be OK.
Still though, I would say it would be pushing it and I would personally settle with 800W from one amplifier channel - the difference is after all only 1.7dB.
And then have an amplifier that easily can cope with the expected lower-than-4-ohms from the speaker.
Cheers,
Martin
Thanks for th explanations. In the manual the 1 minute continuous spec is for @220VAC, they don't say what it is for @110VAC. But you might be right, this is pretty short.
The amp would never deliver near the maximum 1950W of power, since the speaker is rated only for 1200W and my plan was to set a limiter in the DSP to not overload the speaker (still trying to find how to calculate this however, since the limiter uses DB not wattage). Even at 1200W you think the amp would be pressed too hard?
The amp would never deliver near the maximum 1950W of power, since the speaker is rated only for 1200W and my plan was to set a limiter in the DSP to not overload the speaker (still trying to find how to calculate this however, since the limiter uses DB not wattage). Even at 1200W you think the amp would be pressed too hard?
There should not be any difference between 220VAC and 110VAC for the duration of the load.
The specification for the DSP I can not help you with - as I simply can not guess how a limiter threshold is specified in dB's.
dB's is a representation of a ratio - and that needs to involve two values (in some cases dB is used with an implicit reference - like sound pressure where 0dB corresponds to 20uPascal sound pressure).
Are you sure that the dB-"thing" for the DSP doesn't actually use dBu or dBV?
(in which case the reference would be either 775mV or 1V resp.)
Cheers,
Martin
The specification for the DSP I can not help you with - as I simply can not guess how a limiter threshold is specified in dB's.
dB's is a representation of a ratio - and that needs to involve two values (in some cases dB is used with an implicit reference - like sound pressure where 0dB corresponds to 20uPascal sound pressure).
Are you sure that the dB-"thing" for the DSP doesn't actually use dBu or dBV?
(in which case the reference would be either 775mV or 1V resp.)
Cheers,
Martin
And: 1200W should be handable by the amplifier (if the specification is not being overly optimistic).
Do note however that power ratings for speakers are assuming quite a bit about the input signal.
Lots can be and has been written about this - but in short: 1200W continously delivered into the speaker will burn the speaker (think of an electric heater), the power rating is assuming that the input signal is like music with a significant difference between maximum and average power (typically 10 times or more).
This is one reason I would play it safer by just using one side (800W).
Cheers,
Martin
Do note however that power ratings for speakers are assuming quite a bit about the input signal.
Lots can be and has been written about this - but in short: 1200W continously delivered into the speaker will burn the speaker (think of an electric heater), the power rating is assuming that the input signal is like music with a significant difference between maximum and average power (typically 10 times or more).
This is one reason I would play it safer by just using one side (800W).
Cheers,
Martin
The SRX828 has dual 750 watt amplifiers, one for each driver, with a rated peak output of 1000w. Why not use one channel of your Crown XTi 2000 for each of the two drivers in your unpowered subwoofer? Seems like a near perfect match.
Olivierr91,
The XTi 2002 is rated for operation at four ohms bridged, and current limits to protect itself in that operation. It can deliver peaks of 2000 watts. Music signal would typically average less than 200 watts "continuous" (RMS) with 2000 watt peaks, assuming a 10dB or more crest factor.
Some forms of music, such as EDM, or severe mixer clipping may reduce low frequency dynamic range, which could result in more average level than "typical", at worst approaching around 3dB dynamic range (same as a sine wave). That type input could possibly result in an average level approaching or exceeding the continuous rating of the SRX828S.
The SRX828S is rated for 4800W peak, 2400W program, 1200W "continuous".
The SRX828S will handle the 2000 watt peaks the bridged XTi 2002 can produce with no problem to the amp or the drivers, assuming the program material is not severely compressed.
If you don't run overly compressed/clipped program material, the XTi 2002 limiter threshold could be set to .5dB to keep it from clipping, while still allowing near full peak power.
If you are concerned about compressed/clipped program material allowing too much average level, you could reduce the threshold to -2 or -3dB and not have to worry about the DJ set roasting the sub.
Of interest, the drivers in the powered SRX828PS are 2 ohms, each potentially getting 1000 watt peaks as Johnmath pointed out.
The passive SRX828 uses two 4 ohm drivers. Since the XTi 2002 only delivers 475 watts peak into 8 ohms, to get the same peak potential as the SRX828PS will require the amp to be bridged mono.
Art
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Another vote for using dual mono mode with each driver getting it's own channel. This is a bit easier load for the amp to manage and it will produce the same output power for all intents and purposes as bridged mono. The only thing needed to do this is a 4 conductor speaker cable and a jumper has to be moved on the subs input terminal plate.
I am confused by the different informations I have here.
@johnmath, each drivers of the non-powered version (JBL 2279 LF) can handle 2400W Peak, 1200W Program, 600W Continuous, not 750W. I think using one channel of 800W RMS for each driver would blow them.
@weltersys, the ratings in the manual are stated to be "Minimum Guaranteed Power", "1 minute continuous" and "1/8 power pink noise". In my understanding this terminology is much closer to "RMS" than "peak power". Which makes the bridge-mono mode to deliver 1950W continuous for music with a normal dynamic range. Unless I am misunderstanding something here? I'm not convinced the bridge-mono mode at full power would not blow the speaker.
@conanski, not a bad idea, but I would like not to have to disassemble the input terminal plate when I change subwoofer configurations to use them with a properly matched amp. The only externally accessible switch on the SRX8282S is the +/-1 or +/-2 Selectable.
Anyway thanks for all your help, I'm going to settle for a single 800W channel until I buy a proper 1200W amp. I thought getting an amp in bridge-mono mode to match a single sub would be a lot easier than that. I wish Crown could provide an output wattage limiter or output wattage display like in my D&B amps.
@johnmath, each drivers of the non-powered version (JBL 2279 LF) can handle 2400W Peak, 1200W Program, 600W Continuous, not 750W. I think using one channel of 800W RMS for each driver would blow them.
@weltersys, the ratings in the manual are stated to be "Minimum Guaranteed Power", "1 minute continuous" and "1/8 power pink noise". In my understanding this terminology is much closer to "RMS" than "peak power". Which makes the bridge-mono mode to deliver 1950W continuous for music with a normal dynamic range. Unless I am misunderstanding something here? I'm not convinced the bridge-mono mode at full power would not blow the speaker.
@conanski, not a bad idea, but I would like not to have to disassemble the input terminal plate when I change subwoofer configurations to use them with a properly matched amp. The only externally accessible switch on the SRX8282S is the +/-1 or +/-2 Selectable.
Anyway thanks for all your help, I'm going to settle for a single 800W channel until I buy a proper 1200W amp. I thought getting an amp in bridge-mono mode to match a single sub would be a lot easier than that. I wish Crown could provide an output wattage limiter or output wattage display like in my D&B amps.
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If speaker is rated 1200W|(I´d LOVE to read the fine print around that spec) and amp can deliver 800/4 as the "basic" setup, by all means use that.
It will be chest thumping wall shaking power anyway but specially, will be SAFE.
I would never ever use an amp rated HIGHER power than what speaker can handle, unless used at home only, where the "10% rule" ,"10 dB headroom rule" or the "1/8" pink noise" may apply, but again: NEVER EVER in a PRO situation (PA or DJ).
And at home, both 800W RMS and 1950W RMS are exactly the same: INUSABLE so why agonize for a perceived "loss"?
It will be chest thumping wall shaking power anyway but specially, will be SAFE.
I would never ever use an amp rated HIGHER power than what speaker can handle, unless used at home only, where the "10% rule" ,"10 dB headroom rule" or the "1/8" pink noise" may apply, but again: NEVER EVER in a PRO situation (PA or DJ).
And at home, both 800W RMS and 1950W RMS are exactly the same: INUSABLE so why agonize for a perceived "loss"?
That's not possible with any kind of music program. Unless the speakers will be exposed to sine waves for extended periods they are in no danger, with the amp limiters active to prevent clipping this rig will be perfectly safe.. just like the powered version.
Are you thinking there is a danger because of too little power, or that you need 1200w/driver to be safe? This is a widely misunderstood topic and much of the information available online is misleading at best.
In my passive system the sub drivers are rated at 700w continuous and I power them with an amp channel that generates 1100w, limiters are set to prevent clipping so the drivers see all that power. The compression drivers are rated at 110w and are driven by an amp that generates 350w/ch, but these are limited to around 1/4 of that. The low-mid drivers are technically underpowered at their rms rating but that is enough for this combo to produce balanced sound. This rig gets driven for all it's worth by DJs mostly(some live bands) and there has never been a problem.
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Not arguing, just commenting on Real World use:
They will drive any sound system they use 10-15dB beyond maximum signal, even very good limiters will smash (that´s their job) any music program through them into a very good thermal equivalent of a continuous sinewave, at 95% RMS power out.
They will heat up > distort > melt > burn any voice coil available.
To begin with, NO speaker coil can handle 600-800W RMS.
Think of an office-bedroom infrared heater with a couple quartz tube "sticks" which get red hot with 600W dissipated inside a 40-45 cm long quartz tube.
Now imagine that same amount of electrical heat being dissipated by a 3" or 4" diameter voice coil inside a speaker and glued to a paper cone (and cloth spider).
An enthusiastic excited DJ + all those HOT girls shaking their bums to his Music + 4-6-8 hour raves
and you end up with:
or worse.
There is a reason reconing high power speakers is a lucrative market.
No need to go far away for an example, en ex employee who learnt the trade assembling my speakers, "flew away" and is VERY busy reconing Car Audio subwoofers, those "1800W" monstrosities.
Try DJ use 😱
They will drive any sound system they use 10-15dB beyond maximum signal, even very good limiters will smash (that´s their job) any music program through them into a very good thermal equivalent of a continuous sinewave, at 95% RMS power out.
They will heat up > distort > melt > burn any voice coil available.
To begin with, NO speaker coil can handle 600-800W RMS.
Think of an office-bedroom infrared heater with a couple quartz tube "sticks" which get red hot with 600W dissipated inside a 40-45 cm long quartz tube.
Now imagine that same amount of electrical heat being dissipated by a 3" or 4" diameter voice coil inside a speaker and glued to a paper cone (and cloth spider).
An enthusiastic excited DJ + all those HOT girls shaking their bums to his Music + 4-6-8 hour raves
and you end up with:
or worse.
There is a reason reconing high power speakers is a lucrative market.
No need to go far away for an example, en ex employee who learnt the trade assembling my speakers, "flew away" and is VERY busy reconing Car Audio subwoofers, those "1800W" monstrosities.
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No PA amplifier made today, regardless of price, can put out its full rated power at 2 ohms indefinitely. The last amplifier that came close was the OLD Peavey CS800, which could hold full power at 4 ohms indefinitely (but not at 2). The heat sinks on that 800 watt amp are the same size as the ones on a 5000 watt amp today. Class H or TD help with the heat, but only by a factor of 2 not 10. “Continuous” only means a steady sine wave - some limitation on duration applies. If the Crown specifies one minute, that probably accurate. Some of these 1U high 10kW class D’s specify for tens of milliseconds. Anything that will run 2 ohms for a minute or so will likely run full power at 8 ohms indefinitely, and for a reasonable period of time at 4. Yes, many instrument amps will run at full power at its lowest impedance indefinitely - but they HAVE to, and when was the last time you saw a 2 kilowatt guitar amplifier? Any why would anyone want one unless they are Marty McFly? The heat sink to put out 200 watts indefinitely is reasonably sized/priced. “1/8 power pink noise” is the test signal for which the AC line current is specified. Run it harder and it WILL draw more. In real professional use PA amplifiers will never be run harder than that, except for the crescendo at the end of a set. That only lasts 10 seconds or so and then it gets quieter. DJs who run their own sound rigs may have other “requirements” - ones that don’t understand equipment limitations will have a string of blown speakers/amps. Where the sound is hired out, the rig is sized appropriately (a lot bigger than what DJs can typically afford, store, or transport).
Any audio signal intelligible as music will vary in level continuously and have some average level that is lower than the maximum. You could take a track like Dark Horse and run the sub 3 dB into clip and get something that’s close to a sine wave - but then it literally *sounds* like someone putting their thumb on the end of and RCA cable and just leaving it there (with a short interruption every three seconds or so). If you anticipate running your gear that hard, even for short periods of time, use speakers with a thermal power rating equal to that of the amp, and run it at an impedance where it will put out full power indefinitely. That’s why I bought 8 ohm drivers for my lates subs - bridge 4 ohms when headroom is important, and drop it down to 8 ohms stereo when the crowd might want it turned up to 15. Same equipment can be used (CA18’s driving 18TBW100’’s).
At that rave, the system is probably 100kW an cost three quarters of a million dollars.
Any audio signal intelligible as music will vary in level continuously and have some average level that is lower than the maximum. You could take a track like Dark Horse and run the sub 3 dB into clip and get something that’s close to a sine wave - but then it literally *sounds* like someone putting their thumb on the end of and RCA cable and just leaving it there (with a short interruption every three seconds or so). If you anticipate running your gear that hard, even for short periods of time, use speakers with a thermal power rating equal to that of the amp, and run it at an impedance where it will put out full power indefinitely. That’s why I bought 8 ohm drivers for my lates subs - bridge 4 ohms when headroom is important, and drop it down to 8 ohms stereo when the crowd might want it turned up to 15. Same equipment can be used (CA18’s driving 18TBW100’’s).
At that rave, the system is probably 100kW an cost three quarters of a million dollars.
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I do.. regularly, read my second reply just above your last post. This is real world use, I run a sound and lighting business that caters to wedding/corperate party DJs.
Most of the DJs I work with are pretty good at keeping their levels reasonable, there are a few that tend to push the levels up as the night wears on but they're still not solid redlight types. Even so the sound system will regularly spend a lot of time at the limiting threshold with those lights flashing away to the beat, that I don't mind and has proven itself to be safe and to not sound bad.
Digital liniters don't work the same way as an analog comp/limiter, the algoritim looks ahead and actually reduces gain momentarally to keep the signal within limits so there is no squashing going on at the limiter. That doesn't help with compression that could be a result of overdriving the DJ mixer/controller but I generally don't have much problem with that.
An 800W amp cannot deliver 800w of music continuously unless driven into severe clipping, which will of course sound pretty disgusting. At best with heavy compression and restricted to electronically crossed bass frequencies an 800W amp will deliver 800W "program" which is below the 1200W "program" rating of each speaker. The active version of the sub has an amplifier rated at 750W continuous for each driver.