JBL surrounds for home cinema

[Kwikas]

After much consideration I've decided to embark on my first DIY build and make some surrounds for my HT. I'll be building 8 in all.

Although I want to try and model the cabinet size (and shape) on the JBL 8340/8340A, I am considering the use of different compression drivers and possibly different 10" transducers. The 8340's utilise a 2412 compression and a 127H 10".

But since this is a DIY, I'm not restricted to those drivers and perhaps the collective brains trust around here have some better idea's on what can/should be used. Please note though, that cost is of importance and I've noticed that once you start moving beyond the 2418 compression drivers, prices start to rise significantly.

From my understanding, the 2412H compression driver isn't one of JBL's standouts so what do you folks think about the use of 2408's, 2414's, 2416's or 2418's for this? Any idea's on suitable 10" drivers would also be of great help too.

I"ll be happy to settle on the 2412's and 127H's if you tell me they are best suited to this type of speaker.....and if they are the best fit for the size and type of cabinet.

Just in case this is important, I wont be fitting any active crossover inside the cabinets. All crossover duties will be handled through my Soundwebs.

I look forward to your comments and advice. Many thanks.

[Robh3606]

The horns/waveguides you use will dictate your crossover point which will influence what drivers you use. You need to look at the total system. The older compression drivers will most likely play lower but not have the extreme top end above 15K.

Rob:)

[Kwikas]

Rob, thanks for giving me a starting point.

When you say older drivers, can I assume that these are models with a lower number than 2412 (as presently fitted to the 8340's)? Such as a 2408 etc. While I'm not sure how the JBL model sequencing goes, I am guessing that the higher numbers mean a later model.

If my understanding is correct, then any of the 2416, 2417 and 2418 types would/could give me the higher frequencies I will need - provided I have the right wave guides fitted.

Okay, waveguides....that's something I hadn't considered. There's not much room in the 8340 cabinets and the wave guides appear to be built in to the front baffle - at least on the 8340A they are. They are quite small. I'll see what else I can find out.

[Robh3606]

2416, 2417 and 2418

Those are the older drivers. They are 1" compression drivers with a 1.44" Dome. The newer drivers are a mix of 1" domes and ring radiators.

Rob:)

[Kwikas]

Thanks again.

What about 2408's? Will these give me the HF I'm after (coupled with the right wave guide)? Any suggestion on the guide specs or where I could locate these?

I've got 3 JBL 3632 Screen Arrays up front which use 2418 HF drivers and I've got a spare 2418 driver that I can use but it may not be the best choice for what I'm wanting to do.

[Robh3606]

Try using the Search it works quite well

http://www.audioheritage.org/vbulletin/showthread.php?18999-2408H&highlight=2408

Rob:)

[jcrobso]

For a 10" JBL 2123 is a good choice, in a 1.5 cu ft box and it will get down to 80hz.
Yes, the 2412 is NOT JBL's best driver. I know of some that have replaced it with this one.
http://www.parts-express.com/pe/pshowdetl.cfm?&DID=7&Partnumber=264-270&ctab=2#Tabs
Is is a Selenium driver(now JBL) it comes in a bolt version as well.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-271

[grumpy]

...a Selenium driver(now JBL)

Selenium is, as I understand it, now a Harman company... it is not now JBL.
(perhaps that was what was meant, in an easily misunderstood shorthand).

[lgvenable]

while its fun to DIY, these can be found at theaters which are closing here in the States. I got a load of 30 surrounds 8330's and 8340's at 50.00 each; making it a lot easier to buy 6 for my theater room.....so I kept an extra 6 for when we move (retire) to Oklahoma. You might be able to find some in the old outback that cost less to refurbish than to build.

[Kwikas]

Many thanks for the responses.

lgvenable, the 8340's are indeed a good price second hand...the 8340A's somewhat less so. However, I'm in Australia and the cost of shipping down here from the USA is very horrid. Really horrid.

The 8340A's are lighter than the original 8340's so while you pay more up front to buy the 8340A's, you pay less in shipping costs to get them down here. It's the other way around for the 8340's. But either way, since I'm up for 8 surrounds, it's not a small amount of change.

The prices you paid are very good. I'm restricted to ebay unfortunately since I'm not on the ground in the USA and I'm unable to get to check out local sales. I've not seen any 8340A's on ebay for less than $150.00/each....but I might have missed some.

jcrobso, thanks for the suggestion with the drivers and I'll look into these. Certainly the Selenium is within my budget. Do you have any suggestions on waveguides to use with this combo?