6 replies to this topic

[outbreak198x]

Hello,

We have 3x itech 8000 and 1 Xti 4000 - with 8x JBL SRX728S + 4x JBL SRX722F.
Now i'm not happy with the configuration - because it sounds not realy good.
I tried some different settings (official settings from JBL and many many different settings we tried)
We play 4 Woofers with 1xItech 8000 2x1channel - other itech same @
31.5 BW18 HPF
80hz LR24 LPF
Bell PEQ @ 75hz Q=3.41 1.5dB
that sounds very nice.

But not the 722 biamped... itech8000 (mid) + xti4000 (high)
2x722 1 channel - settings from JBL

I think the problem in this configuration are the ohms because everything is bridged

Any suggestions?

[dakos]

Hello,

We have 3x itech 8000 and 1 Xti 4000 - with 8x JBL SRX728S + 4x JBL SRX722F.
Now i'm not happy with the configuration - because it sounds not realy good.
I tried some different settings (official settings from JBL and many many different settings we tried)
We play 4 Woofers with 1xItech 8000 2x1channel - other itech same @
31.5 BW18 HPF
80hz LR24 LPF
Bell PEQ @ 75hz Q=3.41 1.5dB
that sounds very nice.

But not the 722 biamped... itech8000 (mid) + xti4000 (high)
2x722 1 channel - settings from JBL

I think the problem in this configuration are the ohms because everything is bridged

Any suggestions?

Any other processors/mixers other then the on board DSPs? What's bridged? It looks like everything except the XTI is in stereo 2 ohms. What settings do you have for the biamped 722? Do you sum the signal to the subs?

[outbreak198x]

No other processorts, just onboard dsp's,
yes its nearly everything @ 2 ohm
bridged are 2 woofers on each channel of one itech8000
and bridged are the mids of 2x722 on each channel - itech 8000
and the high's of 2x722 on each channel - xti4000

settings for biamp:
itech 8000:
HP BW 18db 62,5Hz
LP LR 48db 1,22khz
EQ1 648Hz -4db Q 2,45

Xti 4000: -6,5db
HS Filter 5,5db
6,28khz
HP LR 48db 1,155khz
LP BW 6db 20khz

I think thats the last settings we had

[dakos]

I see a few basic flaws in your settings such as the overlapping of the crossover frequencies, they shouldn't overlap, in fact there should be a gap between them otherwise you get a comb filter effect (boosting some frequencies and cancellation on other frequencies), that makes for a bad sounding system!!!

I suggest you try the turnings from JBL for "bi amping with subs":

728s SUBS
HP 31.5 Hz
HP FILTER/SLOPE BUT18
LEVEL 0dB

LP FREQUENCY 80 Hz
LP FILTER/SLOPE LR24

EQ F1 SUBS
TYPE BELL
FREQUENCY 75 Hz
GAIN -1.5dB
Q 3.41



722 MIDS
HP 90 Hz
HP FILTER/SLOPE LR24
LEVEL 0dB

LP FREQUENCY 1.12 KHz
LP FILTER/SLOPE LR24

EQ F1 722 MIDS
TYPE BELL
FREQUENCY 630 Hz
GAIN -3.5dB
Q 2.63



722 HIGHS
HP 1.18 KHz
HP FILTER/SLOPE LR24
LEVEL -10dB

LP FREQUENCY NONE
LP FILTER/SLOPE...

EQ F1 722 HIGHS
TYPE BELL
FREQUENCY 1.6 KHz
GAIN -1.5dB
Q 3.41

EQ F2 722 HIGHS
TYPE H-SHELF
FREQUENCY 6.7 KHz
GAIN 5.5dB
Q 9 dB/octave


I would also try this with only one pair of speakers and 2x728s cabs standing next to each other (center clustered). Doing that would eliminate speaker placement errors.
Do you use signal summing for the subs or are they running in stereo?
Lets start here and see how it sounds.

I'm pretty sure that's not an impedance issue.

[outbreak198x]

signal = summing (i think so) - i will try the settings in a few hours

[dakos]

signal = summing (i think so) - i will try the settings in a few hours

Signal summing is a feature on you amps DSP, it takes the signal from channel A and summs it with the signal from channel B, the result is a mono signal that has the data from both channels. You need it for subs so make sure you use that.

[outbreak198x]

Yes i know, and it runs @ the settings above in the moment, (andno more time to try something else, but it sounds good :-D Thanks a lot