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Author Topic: JBL's New SRX800 Series Subs - How do they compare?  (Read 26139 times)

Andrew Brubaker

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #60 on: October 28, 2016, 05:10:43 pm »

I would use the 1600 watts at the continuous rating-NOT the program rating.

So that would be 80V.  I would also change the attack time to 20-30ms.

Remember that the peaks are generally short, so they will pass before the attack time start to dramatically limit them.

You MUST weigh getting that little extra dB or so out of a cabinet-vs burning them up.

What is most important?

To me-having the cabinet working at the end of the night is MUCH more important than trying to squeeze an extra dB or so out of the cabinet-that NOBODY would every notice.

Having my gear intact at the end of the night is obviously the more important thing here. Would having the peak voltage at the program rating really be that likely to harm the subs? I appreciate your wisdom and insight on this matter, Ivan!

Please see the attached revision. Do the release and attack times for the RMS (thermal) limiter look in line with what they should be?
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David Sturzenbecher

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #61 on: October 28, 2016, 05:15:43 pm »

Andrew, if you look at some attack times that JBL uses on their itechHD presets for their own subwoofers, they are in the 4-7 second range. I know Ivan recommends a little shorter 1-2 seconds. Kinda all how cautious you want to be. 


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Ivan Beaver

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #62 on: October 28, 2016, 06:16:46 pm »

Andrew, if you look at some attack times that JBL uses on their itechHD presets for their own subwoofers, they are in the 4-7 second range. I know Ivan recommends a little shorter 1-2 seconds. Kinda all how cautious you want to be. 


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For those woofers-I would probably go with 2-3 seconds.

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Ivan Beaver
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Ivan Beaver

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #63 on: October 28, 2016, 06:28:04 pm »

Having my gear intact at the end of the night is obviously the more important thing here. Would having the peak voltage at the program rating really be that likely to harm the subs? I appreciate your wisdom and insight on this matter, Ivan!

Please see the attached revision. Do the release and attack times for the RMS (thermal) limiter look in line with what they should be?
It is not the limiter settings that will harm the subs, but rather the program content.

For example-if you want to "squeeze every watt" out of any loudspeaker, then tell me what SONG you want to play.

I can analyze it and come up with some settings to "get the most" out of the loudspeaker.

You DO NOT get to play any other song-because the settings will be different for the different song.

Different styles put different strains on different parts of loudspeakers.

How long the system is operated and under what conditions also affects the limiter settings.

A system that is run 24hours a day for 3 days with no break MUST have lower limiter settings than one that plays for 45 minutes and takes a 15 min break.  And has breaks between songs that there is some talking.

At best-limiter setting is a guess/estimate, based on experience with a particular loudspeaker, and how a particular DSP reacts.

The limiters on different DSPs (just like the eq and crossover settings) ARE NOT the same from model to model.

It is best to "tighten up" on the limiters (setting them lower than specs would indicate)-just in case.

There is no "simple answer" to the VERY COMPLEX question of setting limiters.
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Ivan Beaver
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Chris Grimshaw

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #64 on: October 31, 2016, 05:20:46 am »

For example-if you want to "squeeze every watt" out of any loudspeaker, then tell me what SONG you want to play.

I can analyze it and come up with some settings to "get the most" out of the loudspeaker.


Okay, here's one that I know is particularly evil for subs (caution - NSFW lyrics): https://www.youtube.com/watch?v=UnQY3swM4tA
I believe its basically a compressed 36Hz sine wave with a peak-to-average ratio of less than 3dB.


One thing that isn't addressed is the frequency dependance of power handling. For instance, if you've got a cabinet that tunes to 36Hz and play that track, the woofer will barely be moving. Most bass drivers rely on forced air movement to keep the motor cool. No cone movement = no cooling, so now you're going to need to severely de-rate your thermal power handling.
What would you set for that track and a TH115?

For what its worth, most music isn't as bad as this. Live rock, for instance, has most of the LF power in the kick drum (ie, very peaky), so you're in more danger of over-excursion than burning the drivers.

Chris
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Ivan Beaver

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #65 on: October 31, 2016, 06:12:39 am »


I believe its basically a compressed 36Hz sine wave with a peak-to-average ratio of less than 3dB.



What would you set for that track and a TH115?


If that is your "reference and want to reproduce the 36 Hz tone loud, then I would not use a TH115-because 36 Hz is below the -3dB point.

But if you did want to use the TH115-then I would raise the HP filter a bit to maybe 35Hz, put some out of band eq down low to get a steeper slope without as much phase shift as a steeper filter would produce.

The actual limiter settings would depend on what particular settings were available.

But if you were talking sine waves below specs, then I would go for 1/4 power.  So if using the 4 ohm version, then 31 V with a 2  second attack,  would be a good number to start with.
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Chris Grimshaw

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #66 on: October 31, 2016, 06:43:18 am »

Hi Ivan,

I was under the impression that the TH115 has a 36Hz tuning frequency, but (as with most tapped horns I've seen) rolls off slightly before that. Perhaps the TH118, then?

Either way, just curious about how cautious you'd be with music that approximates sine waves, and the worst-case where the sine wave happens to be at a frequency where there's not much driver cooling. You've certainly tested more speakers than me, so any insight into what happens when the going gets really tough would be appreciated.

Cheers
Chris
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Ivan Beaver

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #67 on: October 31, 2016, 01:32:22 pm »

Hi Ivan,

I was under the impression that the TH115 has a 36Hz tuning frequency, but (as with most tapped horns I've seen) rolls off slightly before that. Perhaps the TH118, then?

Either way, just curious about how cautious you'd be with music that approximates sine waves, and the worst-case where the sine wave happens to be at a frequency where there's not much driver cooling. You've certainly tested more speakers than me, so any insight into what happens when the going gets really tough would be appreciated.

Cheers
Chris
If you want to only use 1 song, then there are all sorts of options you can do for limiting-such as using a side chain on the limiter that is tuned for the "particular freq".  Actually study the freq, the durations etc in the song to get a better idea of how it would heat up and cause excursion issues.

But you would also have to study the impedance graphs of the sub, the excursion plots etc to come up with the "ultimate limiter" for that song.

But play a different song and now it is different.

So the best you can come up with is decent guess that would cover a wide range of material.

It is a waste of time trying to come up with the proper settings for one song-unless that is all you are going to play.

BTW-we do have some large systems (think multiple Jerichos for each install) and all they will ever play their entire life is part of ONE song.  Usually 30 seconds or less.

So in that case you could make the argument for spending the time.  But since they are not run at max capability, squeezing out every last dB is not that important.
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Ivan Beaver
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Art Welter

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Re: limiters
« Reply #68 on: October 31, 2016, 02:25:10 pm »

I was under the impression that the TH115 has a 36Hz tuning frequency, but (as with most tapped horns I've seen) rolls off slightly before that. Perhaps the TH118, then?
Chris,
Both TH-115 and 118 are basically the same box, with the same Fb. At Fb, the excursion is at minimum as well as the impedance being at minima.

Therefore, the driver consumes the most power at the frequency where there is the least cooling- the coil is not pumping the heat out of the magnet assembly like it will just 1/3 octave above Fb where excursion is greatest, but impedance much lower.

Since the TH power specs are just reprints of the AES driver free-air rating based on a nominal 4 ohm driver with a given voltage (not wattage), the actual in-cabinet power dissipation due to the much lower impedance of the TH loading is much greater, hence Ivan's  advice "if you were talking sine waves below specs, then I would go for 1/4 power".

Otherwise, it's like the old song:
"Burn, baby Burn,
Disco Inferno"


Cheers,
Art
« Last Edit: October 31, 2016, 02:27:56 pm by Art Welter »
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Chris Grimshaw

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Re: JBL's New SRX800 Series Subs - How do they compare?
« Reply #69 on: December 12, 2016, 07:51:35 am »

That's what I'd do, for sure....too easy and low $ vs cost of a lateral change...
I could see a jump to TH-118's or Orbit Shifters or something in that vein, but why spend very much money for any move less than that..

Here's a good review of the 800 series, that you'll need to put in google translate..http://www.production-partner.de/test/jbl-srx-800-im-test/
It's mostly about the 835 and 815, but it does provide some info about the 828..


edited for more clarity

Just read through that. Thanks for the great link.
I'm going to see if I can do some similar testing with my own speakers - with all the unobtainable max.SPL figures that manufacturers are pushing out, having some solid numbers (this box will produce this SPL in this range with a maximum of 10% THD) is really useful to compare.

Cheers
Chris
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