passive equalization for 2380A horn

[aust-ted]

Hi

I have just constructed a pair of bass boxes each using a pair of 2235H drivers. The boxes are about 15 cu ft each and tuned to 20 Hz.

Am using them with 2450/2380A mids and 2404 baby bums. For my main system I have used active xovers (JBL M553). Am pretty happy with the result.

Now the query.

I also wish to use these speakers as part of a theatre set up using passive xovers and a surround processor amp. It is not practicable to use my main amps in the theatre set up. I have some JBL 3110s and was planning on making my own HF networks. Can anyone give me advice on how to add passive equalization for the 2380A CD horns?

Regards
Ted

[Robh3606]

Sure what you can do is look at JBL Pro's site to fing a couple of systems that have them then go into there techsheets for the schematics. Post more later. The curves/hinge points are in your M553 manual.

Rob:)

[aust-ted]

Rob

Thanks for the reply. I was thinking along similar lines and discovered that the 4670D uses the 2380A horn. However I have been unable to uncover a xover schematic (N4638 or 320910-001 ???) on the JBL or Heritage sites.

However since I read your message I checked again and discovered a 4670B which uses a 3152A network for which I found a schematic on the JBL site. Would this be useful? Not sure if the 3152A has the necessary equilization.

Also saw a ref to 4673 which uses a 2380A horn with a 3115A network. This confuses me as I thought the 2380A was only good down to 800Hz and the 3115A crosses over a 500 Hz. Have I got this wrong? Also I read somewhere that the 3110A network has an equilization circuit inbuilt but the 3110 does not. Is this correct? Unfortunately my networks are the 3110s (not the A version).

I have a copy of the M553 manual but not exactly sure on how to translate its equilization circuit to add to a 3110.

Regards
Ted

[4313B]

The 3110A has been a tough schematic to find.
Here it is again for reference.
S1 is HF Boost and S2 is HF Gain Control.

[Robh3606]

Hmm

So they use the same circuit topography used in the 4435/4430 an inductor in series to get the last octave boost. Good to know.

Rob:)

[4313B]

Take a look at the 3131 network in the old 4331 Rob. That was good for a few extra dB out of the fog horn on the top end.

3131 Network (http://www.jblproservice.com/pdf/Network%20Schematics/3131%20Network.pdf)

[aust-ted]

Giskard
Thanks for the schematics

Can you confirm that the 3110A will provide the equalization for the 2380A horn? What setting on the HF boost should you use?
Surprised that I could find no reference to this on the JBL site.

The other problem that I have is that I have is that the 3110 networks I have have different inductor values as well as being significantly different in other respects. May be difficult to mod them. Does anyone know the history of the develkopment of these designs?

Regards
Ted

[Robh3606]

Hello Ted

Take a look at the 3110A network again. The mid and high positions are in parallel to the rest of the HF network. All you need to do is drop it in paralel with you current network outside the box. Either position has a series cap so you don't have to worry about a protection cap for the compression driver. I would go with the Cap/Inductor but I don't like too much roll off up top. Just give it a try.

Rob :)

[aust-ted]

Rob

Thanks

My apologies for the late reply. Got somewhat sidetracked.

I understand you refer to adding something like the HF boost circuit which is on the 3110A, to my 3110s. Sounds fairly straight forward if I can implement it correctly. No one jumped in but I assume the 3110A xover is designed for both the 2380 and 2360 CD horns which require different levels of equilization.

Anyway will do some modelling and see what comes of it.

Regards
Ted

[johnaec]

The 3110A has been a tough schematic to find.Yeah - nothing I could find at JBL. 'Not sure if I'd seen it here before...thanks!

John