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Author Topic: Anyone ever taken apart JBL SRX818sp and SRX828sp?  (Read 400 times)

Ben Polius

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Anyone ever taken apart JBL SRX818sp and SRX828sp?
« on: November 28, 2017, 04:18:05 pm »

Ok, so i feel i might get slated for this, buy here go's......

I have 4x SRX818sp. I assume they have 8ohm drivers in them. I also assume the SRX818sp has the same amp and processing etc as the SP828sp.

Assuming both these assumptions are correct  :o, is there any reason i can't buy 4x SRX818s (passive), put a Speakon on the back of the actives, and connect with bin links?

Im sorry if I'm hurting anyones feelings with this devil talk lol

Also, i have some questions about my SRX configuration. Should i right about it here? Or start a separate thread? sorry, i'm new and don't know all your rules here.

Thanks

Ben
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Rob Spence

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Re: Anyone ever taken apart JBL SRX818sp and SRX828sp?
« Reply #1 on: November 28, 2017, 04:32:35 pm »

Why do you assume the active units have 8 ohm drivers?
Why would a single 18 have the same power amp as a dual 18?



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TJ (Tom) Cornish

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Re: Anyone ever taken apart JBL SRX818sp and SRX828sp?
« Reply #2 on: November 28, 2017, 04:43:13 pm »

I also assume the SRX818sp has the same amp and processing etc as the SP828sp.
They don't.

You can't do what you want to do without seriously devaluing your current speakers, and I doubt it would even work, as load monitoring in the amp would probably not be happy with a big impedance change.
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Ben Polius

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Re: Anyone ever taken apart JBL SRX818sp and SRX828sp?
« Reply #3 on: November 28, 2017, 04:49:45 pm »

Why do you assume the active units have 8 ohm drivers?
Why would a single 18 have the same power amp as a dual 18?



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The assumptions are just my thought process. I'm airing them to spark a conversation to find out some things i don't know. I'm fully aware that they might be 4ohm. They also might not be. So i'm looking for the facts from someone who knows. Which is the purpose of a forum correct?
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Ben Polius

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Re: Anyone ever taken apart JBL SRX818sp and SRX828sp?
« Reply #4 on: November 28, 2017, 04:52:51 pm »

They don't.

You can't do what you want to do without seriously devaluing your current speakers, and I doubt it would even work, as load monitoring in the amp would probably not be happy with a big impedance change.

Good info thank you, so the amp modules probably have load monitoring like i itech. Which is what you'd expect from a speaker at this level. Thats that crazy idea out of the window.

Have you had much experience with SRX? Can i throw a couple of questions at you please?
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Luke Geis

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Re: Anyone ever taken apart JBL SRX818sp and SRX828sp?
« Reply #5 on: November 28, 2017, 08:36:22 pm »

If you read closely the passive model uses a 2279H while the powered version a 2279F. I would will a pretty good bet that the powered model is closer to a 2 ohm speaker. I know that they were even utilizing 1 ohm speakers in some powered products at one point. Its how they can get the efficiency to power ratio that they have. The powered model SRX828 is only a 2000 watt peak amp, but still gets max output!!!! The passive model can handle 2,400 watts peak for the 818 and the 828 4,800 watts!!! As you can see there is no way that the two product version can really work hand in hand.
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Ben Polius

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Re: Anyone ever taken apart JBL SRX818sp and SRX828sp?
« Reply #6 on: November 29, 2017, 06:32:56 am »

That all makes complete sense! I did wonder how they Rrived at those figures, and weight etc. Iím going to open one up when they come back to base and have a look. I wonder if the PRX range employs similar ideas?
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Luke Geis

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Re: Anyone ever taken apart JBL SRX818sp and SRX828sp?
« Reply #7 on: November 29, 2017, 02:43:24 pm »

They do.

It's their dual coil differential drive stuff that employs this technology. They change the impedance of the speaker for the passive models to keep within a standard. If my understanding is correct, there is no difference between them other than the impedance. The peak ratings I am not sure about as much?

As I understand it, speaker power is: the square of the voltage / by the impedance of the speaker. So if two different ohm speakers were fed the same voltage, the one with the highest impedance will have less power dissipated through it. For example 100v squared = 10,000 / 8 = 1,250 watts. Whereas a 2 ohm load would dissipate 5,000 watts!!!! If it follows that model you can see how it would require less amplifier power to make a 2 ohm speaker make the same volume as an 8 ohm. I could be correct on my assumption, but I hadn't really studied that aspect of speaker design yet. I just know how you can arrive at the speaker power with the voltage you feed it.
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TJ (Tom) Cornish

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Re: Anyone ever taken apart JBL SRX818sp and SRX828sp?
« Reply #8 on: November 29, 2017, 03:44:50 pm »

They do.

It's their dual coil differential drive stuff that employs this technology. They change the impedance of the speaker for the passive models to keep within a standard. If my understanding is correct, there is no difference between them other than the impedance. The peak ratings I am not sure about as much?

As I understand it, speaker power is: the square of the voltage / by the impedance of the speaker. So if two different ohm speakers were fed the same voltage, the one with the highest impedance will have less power dissipated through it. For example 100v squared = 10,000 / 8 = 1,250 watts. Whereas a 2 ohm load would dissipate 5,000 watts!!!! If it follows that model you can see how it would require less amplifier power to make a 2 ohm speaker make the same volume as an 8 ohm. I could be correct on my assumption, but I hadn't really studied that aspect of speaker design yet. I just know how you can arrive at the speaker power with the voltage you feed it.
Impedance affects the voltage required to dissipate a given power (wattage).  Changing impedance does not give you something for free - a 4Ω 1000w driver and an 8Ω 1000w driver will require different voltages to be fully driven, but the energy supplied by the amp module and the sound output will be the same.
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