JBL SRX718 & 722 System tunings?

V

Vinny D'Agostino

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Jan 12, 2011
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Warwick, Rhode Island, United States
Helping someone with a (2)718 x (1)722 setup per-side, looking for tuning settings for a Itech.
If I could figure out how to get them from JBL's website I would.....
I can't seem to be able to open there files for some reason, but I do have System Arch. and I can punch in settings manually.

The 722's are being powered by a IT4K
The 718's are being powered by a IT6k

The 722's are being run passive.
Looking for EQ, Crossover & limiter settings if possible.

Thanks,
Vinny
 
Re: JBL SRX718 & 722 System tunings?

JBL does not appear to have off-the-shelf Itech tunings for SRX. Measuring one of the DSPs they do support and matching the Itech to that would be the best way to go, but otherwise you might be able to use settings from the PDF and then just measure the box to see how they did. They will need adjustment.
 
Re: JBL SRX718 & 722 System tunings?

The original I-Techs' DSP is "based on" the dbx 480/4800 math, according to the guys at JBL. I'd start with any crossovers & filters for the 480 and give the rig a listen.

Have fun, good luck.

Tim Mc
 
Re: JBL SRX718 & 722 System tunings?

Tim McCulloch said:
The original I-Techs' DSP is "based on" the dbx 480/4800 math, according to the guys at JBL. I'd start with any crossovers & filters for the 480 and give the rig a listen.

Have fun, good luck.

Tim Mc
Click to expand...

Tim, if I were a betting man, I'd bet that there is nothing similar between the 480 and 4800, especially considering the 4800 is double the sampling rate. Considering that, I bet neither is exactly the same as the Itech DSP, either. Bennett probably has measurements to confirm, since he just did that big article on how DSPs are a mess.
 
The 480 is polarity inverse, first of all, and the 4800 is not. The 4800 has the same BZT filter warping in the HF but at the 96kHz sample rate it is different than that in the 480. All the Harman products have different HF shelf definitions. I'd have to look at my measurements to know more.
 
Re: JBL SRX718 & 722 System tunings?

Vinny D'Agostino said:
The 722's are being run passive.
Looking for EQ, Crossover & limiter settings if possible.
Click to expand...

I-Tech and dbx 260 filters match pretty closely at the low levels of boost JBL prescribes (yes, I've measured both). The 722 in passive mode requires no PEQ, only a high pass filter to cross into the sub. Here are the settings you should use in the I-Techs:

SRX718
High pass: 30.4 Hz, BW 18 dB/octave
Low pass: 88.4 Hz, L-R 48 dB/octave
PEQ1: 41.7 Hz, +1.5 dB, Q 5.016
PEQ2: 68.2 Hz, +2.0 dB, Q 5.016
Delay: 0.0 ms
Gain: 0.0 dB

SRX722
High pass: 74.3 Hz, L-R 48 dB/octave
Low pass: Out
PEQ: None
Delay: 0.0 ms
Gain: -6.5 dB

The relative gain between the SRX718 and SRX722 may need to be adjusted to account for the two-sub-to-one-top ratio and for the 0.8 dB difference in voltage gain between the I-Tech 4k and 6k (when they are set to their default 1.4 V input sensitivity). I would anticipate increasing the gain of SRX722 by 2 to 4 dB.

There are no limiter parameters in the dbx 260 file. Even if there were the behavior of 260 and I-Tech limiters is almost certainly different. Your best bet is to see if someone at JBL can help out.
 
Re: JBL SRX718 & 722 System tunings?

Rich Frembes said:
I-Tech and dbx 260 filters match pretty closely at the low levels of boost JBL prescribes (yes, I've measured both). The 722 in passive mode requires no PEQ, only a high pass filter to cross into the sub. Here are the settings you should use in the I-Techs:

SRX718
High pass: 30.4 Hz, BW 18 dB/octave
Low pass: 88.4 Hz, L-R 48 dB/octave
PEQ1: 41.7 Hz, +1.5 dB, Q 5.016
PEQ2: 68.2 Hz, +2.0 dB, Q 5.016
Delay: 0.0 ms
Gain: 0.0 dB

SRX722
High pass: 74.3 Hz, L-R 48 dB/octave
Low pass: Out
PEQ: None
Delay: 0.0 ms
Gain: -6.5 dB

The relative gain between the SRX718 and SRX722 may need to be adjusted to account for the two-sub-to-one-top ratio and for the 0.8 dB difference in voltage gain between the I-Tech 4k and 6k (when they are set to their default 1.4 V input sensitivity). I would anticipate increasing the gain of SRX722 by 2 to 4 dB.

There are no limiter parameters in the dbx 260 file. Even if there were the behavior of 260 and I-Tech limiters is almost certainly different. Your best bet is to see if someone at JBL can help out.
Click to expand...

In both cases I wouldn't worry about peak limiters - the IT4k or 6k don't have enough peak voltage to hurt any of the boxes. Since the regular IT amps have easy fields for Impedance and Watts for the RMS limiter, just punch in the specs of the box, or maybe a little less to help avoid power compression. Maybe 600 watts @ 8 ohms for the SRX718S and 1000 @ 4 ohms for the 722? Neither box really needs much of a limiter with such 'small' amps.

Also, you will clip the inputs of the Itechs if you leave the output bandpass gain below unity. Make the 722 run at unity (0) and the subs run at +6 or whatever sounds right to you.
 
Re: JBL SRX718 & 722 System tunings?

According to the JBL guy I talked to, 4800 settings will work exactly the same in the iTech series (as well as current BSS units).

The oddity is that the settings in the 728 preset are not what's in the 722+sub preset (I've asked about this, but have not received a response).
 
Re: JBL SRX718 & 722 System tunings?

Took me a while to find, but here's what I ended up with after tuning a friend's SRX rig a few years ago... This was the 722 over 728, so I'm not including the sub settings in this.

JBL SRX722 (full range):

HPF: 78hz, 4th order L/R

EQ:
1: -3 @ 250hz, Q3.4
2: -2 @ 550hz, Q4
3: -4 @ 2.5k, Q2.2
4: -4 @ 5k, Q8
5: +3 @ 9.6k, HI SHELF (Adjust to taste)




Evan
 
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