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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Subwoofer Forum => Topic started by: Mario Pollio on October 25, 2018, 06:44:48 PM
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Just wondering how you guys would go about powering a JBL 5628 Cinema sub. The rating on each transducer is 4,000 watts into 8 ohms. You can run it in parallel drive mode creating a 4 ohm load, but I don't know of any crown amps that put out 8,000 watts into 4 ohms unless you bridge the amp. So how would you power this sub? I-tech 4X3500 bridged into 2 channels, to power a single cabinet (over kill, I know), 2 I-tech 5000 HD's per 5628 bridged into each driver, or a bridged I-tech 12000HD into a single 5628 running in parallel drive mode?
Here's a link to the sub I'm talking about
http://www.jblpro.com/www/products/cinema-market/subwoofers/5628#.W9JOw2hKhPY
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Why limit yourself to Crown amps? Linea or Powersoft come to mind first.
Sent from my VS980 4G using Tapatalk
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Why limit yourself to Crown amps? Linea or Powersoft come to mind first.
Sent from my VS980 4G using Tapatalk
Mostly for simplicity and system integration. The sub will be integrated with JBL M2's which are powered by Crown I-Tech 5000HD's. I like Audio Architect as well.
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Actual ratings, the drivers are 1200W AES, and can survive peaks that are 6dB more than that.
I'd use one channel of an iTech 12000HD into the 4ohm load that would be presented and call it good. The amp will put out ~2x the long-term ratings of the drivers.
If you bridged you'd get a couple of extra kilowatts out of the amp, but you'd get less than 3dB of gain. Not worth bothering.
Chris
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Actual ratings, the drivers are 1200W AES, and can survive peaks that are 6dB more than that.
I'd use one channel of an iTech 12000HD into the 4ohm load that would be presented and call it good. The amp will put out ~2x the long-term ratings of the drivers.
If you bridged you'd get a couple of extra kilowatts out of the amp, but you'd get less than 3dB of gain. Not worth bothering.
Chris
The 2269 woofer is 2000 watts AES 2hr and 1200 watts on the 100hr IEC test that JBL uses. The IT12K will be the way to go.
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Actual ratings, the drivers are 1200W AES, and can survive peaks that are 6dB more than that.
I'd use one channel of an iTech 12000HD into the 4ohm load that would be presented and call it good. The amp will put out ~2x the long-term ratings of the drivers.
If you bridged you'd get a couple of extra kilowatts out of the amp, but you'd get less than 3dB of gain. Not worth bothering.
Chris
That's true, I lose sight of that double the power = 3db rule sometimes when dealing with huge power like this (relatively huge for what I'm used to dealing with at least). 3,500 watts seems huge until you look at the whole picture.
The 2269 woofer is 2000 watts AES 2hr and 1200 watts on the 100hr IEC test that JBL uses. The IT12K will be the way to go.
Thanks for the advice on the 12K. That will be the way I will go.
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That's true, I lose sight of that double the power = 3db rule sometimes when dealing with huge power like this (relatively huge for what I'm used to dealing with at least). 3,500 watts seems huge until you look at the whole picture.
Thanks for the advice on the 12K. That will be the way I will go.
The idea that JBL "needs" megawatt amplifiers is a mystery to me. We have HD12k and I can monitor the output in real time. On EDM gigs with sustained bass, our 4880 are bouncing around on the floor with 600 watts of current, you can smell the voice coils getting hot, too.
For impactful peaks? Sure, you need more voltage swing, but unless that level is sustained a megawatt delivery systems in not needed.
You'll do well with the HD12k. What is your application, more cinema?
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The idea that JBL "needs" megawatt amplifiers is a mystery to me. We have HD12k and I can monitor the output in real time. On EDM gigs with sustained bass, our 4880 are bouncing around on the floor with 600 watts of current, you can smell the voice coils getting hot, too.
For impactful peaks? Sure, you need more voltage swing, but unless that level is sustained a megawatt delivery systems in not needed.
You'll do well with the HD12k. What is your application, more cinema?
Having the headroom is nice, and for powering less efficient, more power hungry speakers maybe. Could be marketing as well, but I'm a firm believer in it's better to have it and not need it than need it and not have it.
And yes, the application is a large, steroidal home cinema. The left center and right channels are JBL M2's. I was looking at the SUB18's, but the 5628 is nearly the same price and has another 2269 driver in it. Somebody I've been speaking with has the same set up with both the 5628's and the SUB18's. From his experience with both, he said if you can fit the 5628's and integrate them, go with those. Much more bang for your buck.
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Having the headroom is nice, and for powering less efficient, more power hungry speakers maybe. Could be marketing as well, but I'm a firm believer in it's better to have it and not need it than need it and not have it.
And yes, the application is a large, steroidal home cinema. The left center and right channels are JBL M2's. I was looking at the SUB18's, but the 5628 is nearly the same price and has another 2269 driver in it. Somebody I've been speaking with has the same set up with both the 5628's and the SUB18's. From his experience with both, he said if you can fit the 5628's and integrate them, go with those. Much more bang for your buck.
Dude for the price of that amp you can get a Danley DTS10 and an amp for it! That bad boy has real, usable response down to 10hz. Will vaporize the JBL sub.
Sent from my VS996 using Tapatalk
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Dude for the price of that amp you can get a Danley DTS10 and an amp for it! That bad boy has real, usable response down to 10hz. Will vaporize the JBL sub.
+1.
Alternatively, DIY can be an option. Subwoofers are a good starter project, and if you've got some/all of the tools already, the price to performance ratio is off the charts.
Chris
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Dude for the price of that amp you can get a Danley DTS10 and an amp for it! That bad boy has real, usable response down to 10hz. Will vaporize the JBL sub.
Sent from my VS996 using Tapatalk
+1.
Alternatively, DIY can be an option. Subwoofers are a good starter project, and if you've got some/all of the tools already, the price to performance ratio is off the charts.
Chris
It will vaporize the JBL sub below 20hz. I'm familiar with the DTS10, as well as the many other offerings from internet direct companies like JTR, PSA, Seaton Sound etc. My current subs I'm using are the Seaton Sound Submersive HP's. Great sub, no complaints, the JTR Captivator 4000ULF is a beast as well for $3,499
http://jtrspeakers.com/captivator-4000ulf.html
I just want to try something different this time. And sub 20hz content for me is distracting. I can't hear that low, and when everything in the room starts to shake and rattle, it actually detracts from the movie IMHO. I know I'm in the minority. Nobody uses these subs at home because of their sub 20 hz output or lack thereof. I don't really mind it and want to try something most haven't tried.
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The idea that JBL "needs" megawatt amplifiers is a mystery to me. We have HD12k and I can monitor the output in real time. On EDM gigs with sustained bass, our 4880 are bouncing around on the floor with 600 watts of current, you can smell the voice coils getting hot, too.
For impactful peaks? Sure, you need more voltage swing, but unless that level is sustained a megawatt delivery systems in not needed.
You'll do well with the HD12k. What is your application, more cinema?
Just to pick up on this, a sustained sine tone has a peak-to-average ratio of 3dB, while the AES-standard test signal is 6dB. So for the same heating power at the drivers, you were using the equivalent to 1200w peaks of that test signal. For program material with 10dB peak-to-average ratio, it'll be 3000w peaks.
EDM is a weird case. Most program material demands much more headroom.
To the OP, if you don't like <20Hz content, it's much cheaper to put a highpass filter in place, rather than spend money on new amps and subs.
Chris
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Just to pick up on this, a sustained sine tone has a peak-to-average ratio of 3dB, while the AES-standard test signal is 6dB. So for the same heating power at the drivers, you were using the equivalent to 1200w peaks of that test signal. For program material with 10dB peak-to-average ratio, it'll be 3000w peaks.
EDM is a weird case. Most program material demands much more headroom.
To the OP, if you don't like <20Hz content, it's much cheaper to put a highpass filter in place, rather than spend money on new amps and subs.
Chris
The issue for headroom peaks is instantaneous output voltage swing. We need to stop thinking in Watts except for sustained delivery or heat conversion.
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Just to pick up on this, a sustained sine tone has a peak-to-average ratio of 3dB, while the AES-standard test signal is 6dB.
But that is not comparing the same types of signals, or applying the same math to each one.
For a sine wave, the 3dB difference is from the RMS of the waveform to the peak.
For an AES signal, it is the crest factor of EITHER the RMS of the waveform to the maximum levels (some people call it peak) or the peak values (the dB difference is the same.
HOWEVER, if you compare the RMS of the AVERAGE level of the AES, to the PEAK of the "peaks" (maximum levels), you will see a 9 dB difference.
Some SPL meters are like this.
If you put a calibrator on them, the normal slow and fast readings will be the same SPL, but the PEAK reading (of any weighting) will be 3dB higher.
This is because mathmatically the "peak" is the top of the signal, while the "RMS" is where most voltages are measured.
So it is important to be sure you are comparing the same thing using the same terms,
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Let's not make this harder than it needs to be. Crest factor has exactly one definition which is the ratio of peak to average power. This often is expressed in dB. It is meaningful only for signals with a bounded probability distribution such as a uniform distribution. An unbounded distribution, such as a normal or Gaussian distribution, has an infinite crest factor.
If the power results from a voltage (or current) applied to a constant resistance the crest factor may be determined from the ratio of peak to RMS voltage (or current) and will be the square root of the power ratio. In dB it will be numerically equal to the power ratio as we use 10* log10(P2/P1) for power and 20*log10(V2/V1) for voltage or current. The crest factor of a sine wave is 3 dB, as has already been stated. "RMS power" is a useless term and should be avoided.
Some confusion arises from AC voltmeters that do not measure the RMS voltage but rather the full-wave rectified average. Such meters are calibrated to show the RMS value of the AC voltage FOR A SINE WAVE. For any other waveform the calibration will off and the power calculated from that voltage will not be the power in the load.
Happy Halloween. -F