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DIY Vintage JBL Speaker Component Question

cykotic

cykotic

New Member
I am pretty new to this but am planning on building a set of vintage JBL C35 bass reflex speaker cabinets but will be using newer JBL Components. Specifically, JBL 2226H 15" woofers, JBL 2426H/J HF compression drivers with JBL 2370A horns and JBL 3120A crossovers, crossing over at 1250 Hz . I will be pushing these speakers with a recently restored Sansui 9090DB at 8 Ohms. The 3120A JBL crossovers call for a LF of 8 ohms and a HF of 16 ohms. My question is this...will I run into a problem using an 8 Ohm HF compression driver which matches my receiver output, that being the 2426H, or would it be better to use the 16 Ohm compression driver, the 2426J, which the crossover calls for? Or does it even matter? Any help would be appreciated as I can't really find anything addressing this particular issue via Google.
Thanks much,
-CykoticSansui 9090DB Image.JPG JBL C35.jpg JBL 3120A Crossover.JPG
 
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Yeah, you need to run the impedances that the crossover was expecting for best results, but you really also need to run the components the crossover was designed to operate with, too. Not to say what you have planned won't work, and it might turn out fine. Also, the crossover will be the impedance your receiver sees now, not the impedance of the individual drivers.
 
Jeffery said:
Yeah, you need to run the impedances that the crossover was expecting for best results, but you really also need to run the components the crossover was designed to operate with, too. Not to say what you have planned won't work, and it might turn out fine. Also, the crossover will be the impedance your receiver sees now, not the impedance of the individual drivers.
Click to expand...
Thanks. This has been my dilemma. What I think I may do is just run the 2426H - 8 Ohm HF Compression Driver with the 2226H LF Woofer since my system is 8 Ohm and then try to have the crossovers tweaked somehow to match the 1250 Hz crossover frequency.
I appreciate your reply! Thanks again!
-Cykotic
 
The cross-over points are based on the impedance of the drivers. You'd probably have to redo most of the cross-over. Also, the efficiency of the drivers from 8 to 16 ohm might be different, and your whole system will be out of balance due to this fact.

Not the direction I would go.
 
That setup was used in a few different pro models (4725, 4704). Might be best to look around for a pair of crossovers from those and rebuild them. Then you'd just need to get rid of the unwanted bits like biamp stuff, etc.
 
Looks like an interesting and fun project. I would stick with the 16ohm CD if you choose to go with the 3120a network. Tweaking the crossover for an 8ohm driver is not a good idea and would be much better to build a set at that point. Your 9090 won't have an issue driving the 16ohm HF with 2226H LF at home HiFi levels.
 
HyKlas said:
That setup was used in a few different pro models (4725, 4704). Might be best to look around for a pair of crossovers from those and rebuild them. Then you'd just need to get rid of the unwanted bits like biamp stuff, etc.
Click to expand...

This is the way to go....or build from scratch if someone can help simplify the crossover schematic for you. The NSR4725 crossover was engineered for the components you plan to use...got to perform better than 3120A.

http://www.jblproservice.com/pdf/SR-Series/SR4725.pdf
 
The problem with using a crossover designed for a 16 ohm driver with an 8 ohm driver is that the 16 ohms is a value that figures into the design of the crossover filter. If you change the value of the driver, you will change the crossover frequency. Now you will have a hole between the woofer and the tweeter (crossover frequency too high) or the tweeter will cross over too low and sound bad, damage the tweeter, or both.
 
Well, I am pretty sure you can put either a 16 or 8 ohm diaphragm in the 2426 driver. That would be one option. You could stick an 8 ohm resistor in series with the 8 ohm diaphragm driver. I am not familiar with the crossover you are planning on using, but you need to make sure your horn/driver efficiencies are compatible with that crossover if there is no adjustment for the output level. I am using the 2206 12 inch version of that woofer with the 2426 driver and 2342 butt cheek horn with very good results. The 2206 and 2226 are great lower mid range drivers and cope well with the rather high 1200Hz crossover.
 
PM me if you're looking for the 16-ohm JBL diaphragms for the 2426 drivers. I think I have a pair.
 
One thing I remembered, but I had to check and make sure, was that this crossover in question has a certain degree of stability inherent, making the crossover points a little bit more consistent even in different cabinets, making it less reliant on speaker impedance. That being, the horn or Tweeter in question probably would be out of spec, but there is more flexibility than typical in this unit. This is from the spec file on that particular crossover
 

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