Giskard, concerning CS3115; confusion reigns....

[mikebake]

not long back we conversed on the forum about the crossover to the m209-8A mid from the 2226 in the CS3115. You mentioned 600hz and I think also perhaps how the mids are prone to blowing (and/or I have also heard this from others)

WELL, what do you make of this??

In the CS3115 they state 340hz and 1.8khz

http://www.jblproservice.com/pdf/AS%20Series/CS3115.pdf

In the SR4735X, same drivers etc. it is 600hz and 2.8 khz..

http://www.jblproservice.com/pdf/SRX-F%20Series/SR4735XF.pdf
What gives?????

Now I understand that 600 gives the whole system better power handling, less prone to damaging the mid, but still, why change the 1.8 to 2.8? Or do you think there is a mistake in the info? One is for theater, one for live sound. Personally I have been using about 340-380 with an outboard crossover, and like it better, but what do you think of all this?? The reason I ask is I want to have some passive crossovers purchased/made to be able to use them that way also, and this will of course be critical.

MBB

[subwoof]

it's a typo mike......

Yu shood SE all the typo's that git by the "proofreeders" at JBL.

600 is correct for that 8", BUT maybe when that puppy is in a *sealed* horn loaded chamber it can go lower? I doubt it.

That is a pretty short horn for 340hz to work properly. AND that integral HF horn is also short for 1.8Khz

The 1.8 to 2.8 usually means that the horn geometry or the soundfield desired is different. Since the boxes are **identical** and the components are too, it's physics not marketing.

I'll bet the lower xover points was for a different model ( maybe the 10 / 1.5" ???? ) and someone burned the midnight oil to get that sheet ready for a press release and " haha " no one caught it.

sub

[4313B]

Yeah, could be.

That error was perpetuated to the SR4735X (http://www.jblproservice.com/pdf/SR-X%20Series/SR4735X.pdf) tech sheet?

What does the operator's/owner's manual state?


Originally posted by subwoof
it's a typo mike......

Yu shood SE all the typo's that git by the "proofreeders" at JBL.Yes, a long standing issue actually.

[4313B]

Guys,

Putting the bandpass filter for the SR4735X/F into spice and running a voltage drive yields a -3 dB downpoint at ~ 400 Hz and ~ 1.25 kHz using an 8 ohm dummy load.

[mikebake]

Hey subwoof; were you the one that chimed in before? I thought it was Giskard.
Anyway, my thought was that maybe in a cinema setting they liked/allowed the mid to run lower; more controlled environment than in live sound. And yes, it is front and rear loaded with a thermal transfer back chamber. I have never had any problem running it at 380, where I believe it sounds distiinctly better than letting the 2226 run into the heart of the midrange.
THEN you got me thinking about the damn horn length, and yes, it does look a little short for 340. What is the physical distance for a front horn to be able to load at 340???
NOW, the water gets really muddy.
It's also the same unit as the VS3115, other than the 4 ohm woofer in the CS.

http://www.jblpro.com/pub/obsolete/venue/vs3115.pdf

And read the tuning page for crossover points for the VS series here

http://www.jblpro.com/pages/tunings/venue.pdf

What does it say they should be set at? (Somehow I'm thinking that the internal mid to hi point IS 1.6khz.)


This is the sheet I originally accessed to begin my settings for the crossover/delay. JBL says .416ms delay on woof, I set the crossover at .4 (close enough) (and yes, you can hear the difference.)

Then they show EQ; a narrow bump here, a broader cut there, etc.

Then the crossover points. Pardon my dumbassness, but I read this (there was not owners manual; new in box from tent sale, only a warranty card) as telling me to roll in the mid at 341 with a 24db LR filter, and then at 1.62 the internal takes over (or you can flip the switch and triamp). So IF that is right, then we have the CS3115 pdf saying 340 hz to bring on the mid, AND the VS3115 tuning parameters saying the same thing??? HELP??!!

I was actually thinking of ordering a factory network one of the 4735 series so I could also power them with a passive on occassion and really lighten my load when I want to use them, using one amp or a powered mixer now and then.

(do we have a smilie that shows a smiley face getting in over his (#%(% head??)

[mikebake]

Originally posted by Giskard
Guys,

Putting the bandpass filter for the SR4735X/F into spice and running a voltage drive yields a -3 dB downpoint at ~ 400 Hz and ~ 1.25 kHz using an 8 ohm dummy load.

What does that seem to suggest about what is proper?

[subwoof]

above all else, confusion reigns.

the "active" filter suggests 341 hz / 1.62 Khz with a **24** db/oct filter....

Use the passive ( which is only 12 db/oct ) and the filter points move up and up.....:)

Again basic physics..:cheers:

HOWEVER I do agree that in some listening enviroments lower crossover points make sense - and I *have* seen 2440 drivers run at 500hz in cinema's for years without damage...

BUT I can't tell you how many 8's I have seen with folded paper cones ( near the dust cap/cone seam ) that have resulted from too-low a crossover point or gross overpowering.

If you want to compare horn length, tape measure a 2380 ( or 2370 ) and compare it's polar patterns ( available online from jbl )

I don't think the combo waveguide in yours are posted anywhere...:)

sub

[mikebake]

I see, Steep slope is of course safer. So it DOES say 341 for the units for which NO passive is made, then? Makes sense. 4735, passive, 12db, move point to 600 to protect driver, etc.

Dangit, I knew this would help me. It's the freakin' slope.

I am most generally NOT an overpower kinda guy, and for any live audio stuff I can simply crank the crossover point up and let the woofer eat more juice. Makes sense.
I can honestly say that over all the years I don't think I have ever blown a single driver under my use, home audio, pro drivers, anything. For me, really jammin' is still probably an 80% of max thing.

I had those 2370A's; speaking of freakin typos, read this on the current JBLPro site

Components - 2370A
2370A Specification Sheet
2370A Flat-Front Bi-Radial® Horn
Key Features:
90° x 40 ° nominal dispersion
Uniform horizontal on and off axis frequency response
Precise horizontal pattern control
Full horn loading to 630 Hz
Flat front, compact size, and lightweight construction
25 mm (1 in) throat entry

The JBL Model 2370A is a compact Bi-Radial® horn with a nominal coverage pattern of 90° horizontal x 40° vertical. The horn provides uniform on and off axis frequency response in the horizontal plane from 630 Hz to beyond 16 kHz. The horn's small vertical mouth dimension was chosen to allow a gradual narrowing of the vertical coverage pattern with increasing frequency. This provides acoustic equalization of the frequency response of the horn in the horizontal plane and compensates for the falling power response of all compression drivers. Should constant vertical pattern control be required, two or more 2370As may be stacked to restore full Bi-Radial® performance.

Did you see the typo? First it says full horn loading TO 630hz, then later it says FROM 630hz!! HAR!!
Anyway, that horn is only 6.84 inches deep. The horn on the M209 8A is MUCH deeper, thus may support the 340hz. I'm not at home but I am thinking it's easily 15 inches deep or more. Where is the formula for horn depth to freq. it loads at?

Thanks.
MBB