Enclosure within an enclosure??????

[mrmuse]

Am in the process of rebuilding old Ross (Kustom) 3 way cabs. They originally contained 2 18's (not sure of brand) 1 8 inch (enclosed w/big horn flare) and HF Driver and horn....

I am upgrading/replacing with JBL K151's, 2 8 inch, 1 2426H, 2 EV T35 tweeters...

What I'm wondering is this. The original 8 inch on the flare/waveguide??? Is in a fiberglass sub-enclosure. Do they sell these?? What and where do I look for???.. Do I need to enclose the 2 8's in the new design??

I will post pix of the one I'm workin on, the untouched on, and the sub-enclosure. Any help or ideas would be great...

Thanks

mrmuse

[moldyoldy]

Sealed mids are common in direct radiators to prevent LF IM distortion, a factor that also applies to cone-driven horns. However, cone-driven horns will be far more critical of the volume and shape of the rear enclosure, (Vb) as it can be an additive reactance, or a cancelling reactance, and is highly dependant on the parameters of the cone driver and the horn.
Matching the parameters of the original cone driver would be essential in this case, and as it appears to be a relatively high compression ratio, even more so.

I'd suggest learning all you can about the original 8" drivers, if you can't find the T-S data for them, it'll be pretty difficult to match them without doing some simulations based on accurate measurements of the horn.

As to the actual enclosure, it can be made from any non-resonant material or item as long as the dimensions are correct (i.e. PVC pipe, plastic salad bowls, flower pots,.....)

(Add/Edit) My bad, I misread your intent to do away with the horns. Still would recommend an enclosure for your new setup, either DIY, or you might find some readymades at a car audio seller.

[mrmuse]

None of the drivers are original. I have 2 Knight professional loudspeakers with the number 33002110302 that came in the boxes. One spare..

The 8 inch you see in the picture with a "whizzer" cone are Yamaha, I think made by Eminence. They were a 20.00 deal off Ebay....

My thought was when running them full range using the internal crossover, was that the 18's would be going too high due to the 2 way crossover. I pulled the xovers from my 4628b's and the same thing running them 3 way. I have 4 way active crossovers, and plenty of power amps, so that was my thought. A nice 4 way system in a 39x39x20 cab.

I did notice that the 8 inch in the 4628b's were not in a sub enclosure. Would I be better off buying 4 matching 8 inch and building a sub-enclosure that would fit into the space??? That was my other thought...

I currently just have the baffle for the dual 8's and the tweeters screwed on the front of the cab for testing. It will eventually go inside. I had to measure for the internal bracing so I tacked it up outside...

Also, I have various 18s to choose from in addition to the K151's, I have 4 Eminence LF18s, 6 EV 18B's, so if there is a better combo I would use whatever drivers were called for....

I hooked these up 4 way, using the 4x18's, 4x2225's 2x2426h and 4xT35 tweeters, and they sounded awesome. But the 2225's are in separate cabs, and I had the mids and highs in separate cabs. But I need to make one cab that is easy for me to handle, as I do a lot of live work....

I tried to run them 3 way off my 4 way stereo crossover and just could not find crossover points that sounded "tight", which is what I'm looking for..I hate "boom".

FYI. I do have a couple Behringer DSP 8024's and a condenser mic to RTA with if that is needed...

I just thought instead of "cobbling" them together, I would come here for professional, and sound advice....

Thanks

mrmuse

[duaneage]

I think your going to have to do a great deal of A-B testing to get what you want. This includes mocking up crossover networks to see how that interacts. Creating a system from different drivers is a real challange since the manufacturers had intents on their products being matched to certain drivers in certain applications. JBL is a clear example since many of their drivers were for specific applications.

That being said, as long as each driver is used in manner consistant with it's intention, and you properly cross them over you should be OK. You are going to need to fine tune the efficiency of each driver with either L-pads or resistor networks ( preferred) to match them to each other. Get a sound level meter from radio shack as a start and find a room that is dead enough for sweep testing.

Remember, this is for fun and frolic so be patient.