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Replacement Drivers 2.0

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Nick Falbo:

--- Quote from: Cyril Hebert on January 18, 2019, 02:52:13 pm ---
If anything, the pitty of this story is that the other half of the 2000 watt (max) amp module in the JBL SRX 818sp, isn't even being used.  If JBL made a true dual voice coil speaker (like the 2268FF from the vrx 918sp) and used both sides of the amp, I bet they would sell more of the single 18 powered SRX boxes because as far as i'm concerned, the SRX818sp doesn't have enough output. When the boxes were in their original form, I had to turn the volume back to -2 on the SRX815p tops that I have and the SRX 818sp's (one per side) were turned to +4 to get what I thought was somewhat "ballanced" (roughly 6 db difference).  There are probably those out there saying, "buy the 828sp if more output is needed".  That is true but, there are times when a dual 18 is not practical due to the space given at a venue or the packing space and weight double 18 cabinets command. (just my opinion though) 


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I was under the impression that the 818 and the 828 used different amp modules completely. The 818 had a single set of speaker outputs putting out 750watts RMS (Part number 5069594X) while the 828 had dual speaker outputs putting out 750watts each for a total of 1500watts total (Part Number 5069595X). Now i am kind of interested to tear apart a couple of the SRX subs to see if one amp module will work in the other since they both have different part numbers..... It is funny because the amp module for the 818 is $40 more than the one for the 828....

The only thing I would worry about with Fatial Pro woofers is that they are 1000 watts RMS at 4ohms, and the amp only puts out 750 watts at 2 ohms, it's 4 ohm power will be less most likely (we don't know because JBL doesn't release the specs). I know numbers are just that and don't always equate well into real world scenarios, but I would worry about major clipping if the subs are run hard, since the gain has to be turned up higher to match the output of the stock woofers. The factory settings for the limiters now mean nothing, so they could actually be clipping well before the limit indicator comes on due to the factory presets were programmed for just the stock woofer. We don't know what the outcome is and I am not sure what your use case for these subs are, how much they will be used, how loud you use them, etc. but Just keep in mind all the built in speaker protection and DSP is now pretty much useless due to the modifications you have made.

Cyril Hebert:

--- Quote from: Nick Falbo on January 23, 2019, 08:35:26 pm ---I was under the impression that the 818 and the 828 used different amp modules completely. The 818 had a single set of speaker outputs putting out 750watts RMS (Part number 5069594X) while the 828 had dual speaker outputs putting out 750watts each for a total of 1500watts total (Part Number 5069595X). Now i am kind of interested to tear apart a couple of the SRX subs to see if one amp module will work in the other since they both have different part numbers..... It is funny because the amp module for the 818 is $40 more than the one for the 828....

I'm going to assume that all of the amp modules in the entire SRX800 line are the same module with the exception of how they were programmed from factory based on the different components in each cabinet.  Their part numbers are all only off by by a fews digits on the last number.  I'd be interested to see if the other half of the 818's module is active.

The only thing I would worry about with Fatial Pro woofers is that they are 1000 watts RMS at 4ohms, and the amp only puts out 750 watts at 2 ohms, it's 4 ohm power will be less most likely (we don't know because JBL doesn't release the specs). I know numbers are just that and don't always equate well into real world scenarios, but I would worry about major clipping if the subs are run hard, since the gain has to be turned up higher to match the output of the stock woofers. The factory settings for the limiters now mean nothing, so they could actually be clipping well before the limit indicator comes on due to the factory presets were programmed for just the stock woofer. We don't know what the outcome is and I am not sure what your use case for these subs are, how much they will be used, how loud you use them, etc. but Just keep in mind all the built in speaker protection and DSP is now pretty much useless due to the modifications you have made.

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I completely understand what you are saying.  It is a bit or a risk, I know.  The limiters were kicking in at the same time when I matched the volumes of the stock vs. upgraded cabinets however so I don't think the speakers will be without any kind of protection.  If anything, the distortion level of the amp should be lower (better) going into a 4 ohm load vs. a 2 ohm load (at least that's how it is with respect to power amps for passive boxes, more speaker ohms = less amp distortion).

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