121A vs 2203H sub with BX63A

I stumbled on a NOS C8R121A kit and was amazed at the size of the mass ring!

Here is a picture comparing the 2235H (35gm) with the 121a (95gm).....

SO I was wondering if I would be better off using the kit without the ring in a 2202H basket I have here ( and then creating a 124A / 2203H )

OR

Using the mass ring and making a ferrite version of the 121A.

Any thoughts? I have plenty of power and a BX63A to process it with.

Although it was designed for a special alignment with the 2235 or 2245 BUT the 2203 is the same beast but a smaller diameter...

sub

For what it's worth, I have extensive experience with the 121 and the 124/2203.

"SO I was wondering if I would be better off using the kit without the ring in a 2202H basket I have here ( and then creating a 124A / 2203H )"

The only differences between the 121 and 124/2203 are the mass rings (95 grams versus 35 grams) and the stiffer suspension of the 121. You can't build a true 124/2203 from a 121 kit. G.T. and I recently revisited this and came to that conclusion. He suggested cutting the 121 spiders in the kits to loosen them but I'm not real wild about that.

"Using the mass ring and making a ferrite version of the 121A."

The 121 and 124/2203 came in alnico and ferrite.

"Although it was designed for a special alignment with the 2235 or 2245 BUT the 2203 is the same beast but a smaller diameter... "

The 124/2203 has significantly lower Qts and Fs compared with the 2235 or 2245. It's a real killer. It yields a response that might not work with the BX63. I'll have to get back with you on that.

I've built a significant number of 124/2203-based subs and the best combo I have found is 2.8 cubic feet tuned to 30 Hz. The 121 works best in a 2.0 cubic foot sealed box and I can't recommend it these days when used in singles. It is too inefficient and too displacement limited. You'll probably end up listening to the mass ring smack the pole piece or simply hanging the coil. I have a pair of 121A subs and they work well enough but I have to use at least two of them.

I recently finished a pair of 124H subs for use with a Tannoy dual-concentric 5.1 system. The client couldn't believe how the Tannoy/JBL system laid waste to his "precious" Infinity Reference system. He was going to use the Tannoy/JBL system strictly for HT and the Infinity system for music but after a few days he dumped the Infinity system.

Thanks oh esteemable one...

I wasn't aware of the suspension difference on this 121A kit. Yet another tidbit to file away. I just thought that the mass ring was simply MASSIVE.

I have also used the 2203H's with great success - I just wish JBL would price the kits ( assuming they have / will make them ) proportional to the C8R2235....I would be first in line for a 1/2 dozen..

And I agree on the slice and dice - I have a pair of PR10's with gaping holes in the spider and wonder HOW that stayed close to even travel...
:)

On a side note - if the 121 has a "tighter" spider, then building it sans ring would *raise* the Fs to allow it to perhaps work with the BX63A? It's been a long time since I juggled the TS parameters on this avenue.

I'm not looking to re-invent the wheel but I have a pair of 4401's that I would like to construct a matching sub for the wife's office.

Thanks again, Sub

Quote:

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Originally posted by Giskard

I recently finished a pair of 124H subs for use with a Tannoy dual-concentric 5.1 system. The client couldn't believe how the Tannoy/JBL system laid waste to his "precious" Infinity Reference system. He was going to use the Tannoy/JBL system strictly for HT and the Infinity system for music but after a few days he dumped the Infinity system.

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Which Tannoys? Saturn, D-series, TD-series, Eyris, Sensys, Kingdom series, studio monitor of some sort?

I've been listening to a pair of the new Sensys DC2s (7" DC with a 7" woofer and a supertweeter, floor standing tower), and those things just amaze me more and more. Hooked up a Audio Research SP8 and D70 to them, then an Eastern Electric MiniMax tube pre (linestage with one 12AU7 per channel) running through my recently-restored Magnavox AMP185 (6V6 output) tube amp... and was just stunned with how good the dynamics (especially in the bottom end) and soundstaging were. Even on the Magnavox, which is only 15w/ch! It's great what a speaker with even a LITTLE extra efficiency than normal, can do for dynamics!

Regards,
Gordon.

Hi Gordon,

The Tannoys were the 8" Saturns.

Subwoof,

Did you ever finish this project?

Well subwoof just put the kids back in school and finished the rental renovation just in time for the new tenants so it's time to play sub....for the new den ( just started that project...:o(

Managed to find a refoamed 121 on ebay for cheap so now I have a pair to play with.

I was thinking on putting a sealed sub into the wall behind the (future) stairs or just put the 4688-4 under the floor since I have the joists exposed.

So double 18 TCB or a dual 12 SB....Hmmm....

sub

Anyone got the T/S parameters for the 121? I've got the 124/2203, but can't find the 121's specs anywhere.

Also, WRT the spider... to make a 124 kit, I'd be inclined to take a 121 kit, cut off the spider completely, and fit/glue a softer spider onto the assembly. I've done spider replacements on JBL kits before, so I know it's plausible...

Regards,
Gordon.

ok....got a source for the 4 inch "soft" spider? I've been looking and all the generics I've found are stiff.

I may be able to get hold of some. It may take using a different spider (the ones for Gauss woofers seem to work well, they're very soft usually) and trim out the inner voice coil hole (the Gauss usually use 3" coils) to fit the JBL coil assembly. In any case, it should be possible to come up with something that will work...

I'll look around at my friendly neighborhood pro audio reconing joint... they know me well, and don't mind if I go rooting around in their parts shelves... :D

Regards,
Gordon.