2445J/2380 + 2404H passive xo help

[Ian Mackenzie]

The suggestion of the SL diaphragm has merit.

Are your diaphragms the original diaphragms?

If they are or if you have not looked at them before it can be beneficial to have them serviced and the SL diaphragms installed.

[Juntuin]

I would like to get those diaphragms, is there any supplier other than random sellers in ebay? Mine are with original Ti, never serviced i guess.

[Ian Mackenzie]

http://www.audioheritage.org/vbullet...l=1#post100783

https://reconingspeakers.com/product...0sl-diaphragm/

I recommend you do a search and read up on other users comments and suitability of these diaphragms for your specific drivers. (Make sure they fit)

I’m a Tad4003 user so l don’t use the JBL2445 driver

[Juntuin]

When and if it'll go to changing diaphragms, what about using D16R2441 and just run it as a 2-way system with some eq applied?

[more10]

The D16R2441 will start break up at 7 kHz. It is much better than the ti diaphragm.

I would not use a JBL large format driver/horn without a supertweeter. Certainly not the 2445 with its "inferior" phase plug.

Are you still thinking passive xover?

[more10]

Use what you have. You can always improve things later. 2404 can be used down to 4 kHz. If you cut at 4 kHz you will get rid of the break up modes of the 2445, it will sound just perfect.

[sguttag]

Having used countless 2380 horns (with 2245 and 2246 drivers), I would never cross it over below 800Hz, unless I had no other choice. The driver will be loaded down to 500Hz but the response and control are gone below 800Hz. I'll see if I can dig up the polar response of the 2380. Below 800Hz, it is just a circle. Now, a 2360 horn, that I would go down to 500Hz with absolute confidence.

[ivica]

[QUOTE=sguttag;416474]Having used countless 2380 horns (with 2245 and 2246 drivers), I would never cross it over below 800Hz, unless I had no other choice. The driver will be loaded down to 500Hz but the response and control are gone below 800Hz. I'll see if I can dig up the polar response of the 2380. Below 800Hz, it is just a circle. Now, a 2360 horn, /QUOTE]

Hi,

https://www.jblpro.com/pub/components/2380a.pdf

From the JBL data it is mentioned that you can use 2380a from the 500Hz, but I would suggest something like 700 Hz or more. Its polar response is quite ok from 500Hz over 10kHz.
Using 2441 AL diaphragm would give possibility to use it may be up to 15kHz, but sharp filter has to be used in lower frequency due to the aluminum diaphragm diamond shaped suspension.
Regards
Ivica

[more10]

Your initial plan was to use minidsp as crossover between bass and midrange, and passive between midrange and tweeter?

If so, the passive filter will give you nothing since the minidsp will already have "destroyed the signal" :-)

Go for a full active three or four way system. You can handle the comb filtering problem with digital delay. A small class-d amp will be cheaper than the passive filter components :.)

https://www.minidsp.com/products/minidspkits/minisharc-kit
https://www.minidsp.com/products/minidspkits/minidac8

Create your filter with pos rePhase. pos is a member here.

[sguttag]

Its polar response is quite ok from 500Hz over 10kHz.
Ivica

I don't quite know how you got to that conclusion. It has no pattern control below 1KHz


500Hz
For a 90x40 horn, that is essentially omni-directional.


Its frequency response below 700Hz is pretty drastic too.

Compare that to its big brother, the 2360A:


Now that has pattern control down to 500Hz though perhaps unfair to the 2380A because of its size.

So using another Lansing (Altec this time), the MRII594A which is a similar class/size to the 2380A and you can see that it has better though barely pattern control down to 500Hz and much improved pattern control at 630Hz.



And the frequency response is really down to 500Hz:



So I come back to, I'd avoid using the 2380A horn below 800Hz.

In actual use, this has been born out. But hey, do what you want.

[Ian Mackenzie]

As requested here is a simple passive network for crossover of 5000 hertz to the 2404 from the 2445/2380.

Looking at the response of the 2445/2380 on the basis that you use the mini dsp for the high pass crossover and EQ to flatten the response say 700-3000 hertz a simple 6 dB slope network is mostly all you require as the driver has roll off above 5000 hertz. But l have also given a 12 slope network. I have included a fixed 10 dB pad as l believe noise will otherwise be an issue.

The networks are based on 12 ohm impedance of the driver in the area of interest.

The 2404 crossover is a 12 slope as specified by Jbl and is at 5000 hertz based on a 10 ohm impedance in the area of interest. Again the response falls off below this point. I have included a 5 dB pad so the 2380 and the 2404 should be level matched. Some level adjust could be accomplished with a variable L pad if required but this will be ball park.

This crossover point should be a step in the right direction based on your experience with the 2445/2380 to date and Jbl published technical data. Using the drivers in their optimum range and using a simple crossover design usually delivers a good outcome.

These networks are real and they will work but some adjustment may be required in practice. Placement of the transducers will effect your crossover transitions and l recommend you experiment to obtain the best overall result.

Good luck with your project

Ian

[dn92]

I have impedance measurements for 2450J/2380A and 2404H, this would ease crossover simulation. Just need the time to find them and be back home to share them.
I've also on axis response but without reference timing between the two.

[Ian Mackenzie]

http://www.audioheritage.org/vbullet...work-need-help

An interesting thread on the 2404 crossover

The fixed Lpad l have used will moderate impedance variations.

Maybe Rob has a schematic he can compare.

This is all tough as old boots SR drivers so it’s not like attempting a magazine curve in a HiFi magazine.

[dn92]

JBL 2404H.frd.txt
JBL 2404H.zma.txt

Remove ".txt" in the file name.
Response mesurement was done at 1m distance, on axis. Sound transmission delay removed (Phase aligned to minimal phase), some gating to get a clean phase response.

Files can be directly used in a crossover simulator such as XSim.

[dn92]

JBL 2450J 2380A.zma.txt

Remove ".txt" in the file name.