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bamboo72
08-04-2007, 05:49 AM
Cheers all. OK here are the specs on my fledgling JBL project. Basically this is a cab refinish (dare I say re-veneer?) and total seek and install on the components. Ha.

Now... here is a photo taken by the previous owners. I pick the cabs up this weekend and will take clearer detailed before shots of everything.

http://i57.photobucket.com/albums/g215/medeld/d60f_3web.jpg


http://i57.photobucket.com/albums/g215/medeld/c50sweb.jpg


So given the layout of the existing holes I am guessing that this was once filled with the S8 load? Wow that's a lot to find huh? A million dollars or what?? Another forum member checked these out locally and let me know I am in for a task. Whatevs. I got help right?? ;)

Mr. Widget
08-04-2007, 09:34 AM
Is your goal music reproduction or restoration of a vintage system?

For the purist vintage approach you are right, you'll need to track down an S8 component package, however if you are simply looking for good tunes in a cool vintage cabinet, I'd add a bit of bracing, a pair of 2235Hs with ports tuned to 30Hz, a pair of mid horns and drivers of your choice, and a pair of tweeters. If you are not terribly adventurous you could build a system based on the L300/4333... horn depth might be an issue though as the H92/2312 is pretty deep.

If you are feeling creative there are many options... Zilch has played around with quite a few tiny horns... and some not were not so small...:D One of our forum members had a pair of Olympus C50s with walnut Westlake horns simply sitting on top of the cabinets and they sounded pretty darn good and looked cool too.


Widget

bamboo72
08-04-2007, 10:01 AM
Thanks Widget! Actually I am open to both options. Of course, right now, at this moment the restoration aspect sounds really good to me. Maybe not so good sounding to my wallet. Either way the ultimate goal is to have a sweet sounding set of speakers that will last forever. Open to any suggestions!

I would love to see some pics of some creative uses with these cabs though!

Zilch
08-04-2007, 10:14 AM
I did these 20 years ago. Yes, 2235H bass is VERY nice from them.

I'd do mid/high differently today, and may rework these or mod another pair I have first, so I can A/B them.

While S8 was possible, more likely yours were S7 with a supplemental UHF driver.

Sonically, neither of those vintage systems would be worth pursuing, in my experience. You can get much better sound for much less money using contemporary components.... :yes:

bamboo72
08-04-2007, 10:18 AM
Looks cool! What do you suggest Zilch?

Zilch
08-04-2007, 10:50 AM
To the best of my knowledge, I'm the only member who's had the temerity to actually mod C50s, but I think everyone would agree that 2235H is an appropriate woofer to use. You can get a used pair of those for $300 to $450, or make up an "as-new" new pair for $500 or less by reconing 2225Hs. I think you can still get 2235Hs new from JBL for like $800 a pair last time I looked.

Tuning's not a problem once you've made the cutouts for 4" ducts. Just vary the length to achieve a desired tuning frequency between 30 and 34 Hz.

For mid/high, I'd use BMS drivers on PT-F95HF Progressive Transition waveguides. $300 to $500 the pair, depending upon which combination you use. Add $150 for parts to build DIY passive crossovers, or simple compensation filters plus an active crossover. As Mr. Widget suggests, you can try out the M/H system sitting on top before committing to cutting the baffles to install it within the cabinets.

http://www.jblpro.com/ae/pdf/PT_WaveGuide.pdf

http://www.bmspro.info/

For under $1000, then, you can have a mighty fine sounding brand new two-way system playing in those, perhaps 1/3 the cost of a sonically challenged vintage load. Add $1000 - $2000 if you want to spring for JBLs current best M/H compression drivers.

bamboo72
08-04-2007, 04:11 PM
Thanks Zilch you are mad scientist! So basically pursuing the vintage purist route will yield several times the total cost on this project and I would wind up with sonically less desirably sound? Hmmm, is that a trade off for "braggability" ?? Anyone anyone?

Again... I am "audiophilically" (??) challenged!! I think I could deal with having contemporary components and an amazing end result set of speakers. My plan is to pick up a McIntosh 1500 or possibly a Fisher 500c, but have also wondered about a possible MC240 /MX110 mac combo. Would this work for me, or am I just way to attracted to the vintage element?? Maybe I could afford the macs if I go with the less expensive speakers huh? Ha.

OK another really dumb question, but do you have a specific BMS model driver to recommend? Oh, and one more extra dumb question... "M/H" is that abbreviated for mounted horn?? OK I go now... :D

Zilch
08-04-2007, 08:19 PM
M/H is Mid/High. These are two-ways, no tweeter or UHF driver, which is unnecessary because the BMS drivers play out to 20 kHz.

The $10 JBL PT waveguide only comes in 90° x 50° dispersion and has a 1" throat with thread-on driver attachment. Use BMS 4550 and P-Audio PC-35 throat adapter to mount it, or, if you want the luxury of neodymium and more detailed highs, which I think I do hear, 4552.

The heavier, better $98 PT waveguide is available in 60° x 40, 90° x 50° and 100° x 100° dispersion patterns with a bolt-on 1.5" throat. BMS 4555 mounts directly with no throat adapter, once you drill the requisite mounting holes in the flange. There is no neodymium version of that driver as yet. All of these "Compact" PT waveguides are the same size and mount in the same cutout, once you make it in the baffle.

With this design, the crossover is in the range of 800 to 1200 Hz, and both the 2235H woofer and the BMS/PT waveguide combination are being operated near their useable limits. Thus, I recommend biamping with a 24 dB/octave active crossover such as JBL M552/3 or Behringer CX3400 so that you can adjust the system for the optimum crossover frequency within that range, based upon listening evaluations.

There are better active crossovers, but I have no experience with them; either of those will get you up and running. Implicit in this active approach, however, is that you must select separates, or an amp operable as separates. Preamp out feeds the crossover, which then drives low and high frequency amplifiers individually.

If all that seems too much hassle, a passive crossover is feasible; we've recently done similar with Altec systems here on the forum.... :yes:

Zilch
08-04-2007, 08:54 PM
The equivalent conventional load would be quasi-L300 three-ways, comprising 2235H woofers, 2425/6 compression drivers with HL91 exponential horns and dispersion lenses, and 2405 slot UHF drivers, plus DIY L300 passive crossovers of proven design. These drivers and horns will very likely fit your existing baffle cutouts, i.e., no mods to the cabinets.

Many forum members are running similar systems with excellent results in terms of satisfying performance. It's not the true "Vintage" drivers, rather, more contemporary equivalents of them, which actually play better together than the originals. That combination will cost about $1500 - $2000 to get set up, depending upon whether you want new drivers, how skillfully you acquire the components, and whether you can build the crossovers yourself.

Here again, there's compromise. As Mr. Widget mentioned above, the preferred exponential horn is H92, which will play down to L300's 800 Hz. H91 will play there, but not without coloration; it's a 1200 Hz horn. You can check the dimensions, but I believe if you want to use H92, you'll have to punch the compression drivers out the rear of the cabinets.

So, there's another option for you to consider. This one comes with braggin' rights, 'cause nobody'll know the difference.... :thmbsup:

bamboo72
08-06-2007, 02:33 PM
Thanks Zilch!

If I go with one of the alt options (or combo of them) is the general idea to lose the tweeter, and add a horn/waveguide?

Here is what the guy who sold me the cabs recommended. He had some great sounding gear. He told me to definitely not lose the tweeters. So I am guessing that the M/H drivers do away with that. (Does that make it easier/more efficient to bi-amp?)

He recommended to bi amp using a tube amp for the tweeters and mids and then using a beefier solid state amp for the woofers. I do plan on using the McIntosh MX110 preamp and would like to stick to the vintage vibe.

He also suggested using an electronic crossover (like the ones you suggested)

Any suggestions on a cool vintage solid state amp? If I were to stay all Mc Intosh could I go with the MC2100 solid state and the MC240 or similar for the highs/mids perhaps?? Any input on that one?


Thanks again and pardon my ignorance. I guess you either get dumba$$es like myself or guys getting a quick value on their stuff (before killing guys like myself on ebay.) Ha! Hopefully I am a couple levels above "that guy."

P.S. Picked up the cabs today and they look awesome! Pics to follow!

Zilch
08-06-2007, 04:29 PM
Option 1, a two-way, loses the tweeter, but requires changing the hole for the mid in the baffle. Your expert is correct that you need the tweeter with the standard components, but he is likely unfamiliar with what I propose.

Option 2 is a three-way that keeps the tweeter. It can also be biamped with two amps; the tweeter is often not powered separately....

bamboo72
08-06-2007, 05:07 PM
Thanks Zilch! No...no... you are the expert! :D I seriously appreciate the myriad options you have presented! More to come!

Any suggestions on amps? Is there an advantage on using a solid state and a tube amp on these speakers?

David

Zilch
08-06-2007, 11:19 PM
All I know is that classic tubes sound different.

I hook up my EICO HF-87 to contemporary JBLs, and it instantly recalls the sound of when I originally built that amp and carried it and a pair of AR2a speakers off to college in the '60s.

It measures the same, but sounds different. Call it "Vintage." There's plenty written about this, but I don't care to spend the rest of my life sorting it all out. If I want that sound, I turn it on, is all. It has the added benefit of taking the chill out of the room after about an hour.

There are also contemporary tube designs with which I have no experience. That's esoteric (and overpriced) territory I don't care to visit. Others can fill you in, perhaps.

I'm saying I don't buy into the proposition that any particular brand amp or amp topology is "better" with any speaker, and consider it a recipe for madness to seek an optimum combination of the two as some contend exists.

Do JBLs play better on some particular Sansui, Yamaha, or a resurrected Magnavox console amp?

I don't give a whit, basically; it's all solid-state pro amps here, except for Sony ES with illuminated power meters for show, and the aforementioned EICO for conversation. Good speakers play well on all of them.... :thmbsup:

bamboo72
08-07-2007, 10:52 AM
That is a great guide to follow Zilch. I also believe in if it sounds good it doesn't matter the source. I have had $3000 drum sets and had $50 garage sale kits that have both served their purpose. Thanks again Zilch!!

bamboo72
08-17-2007, 11:48 AM
Just a couple quick follow up dumb questions on this one-

1) What is the difference between a waveguide and a horn in relation to this cab?

2) When tuning this box what is the best way to do it? (never done it before)

3) How much baffle cutting will be needed to go with the waveguide or a horn?

Thanks guys!
David

Zilch
08-17-2007, 02:41 PM
1) What is the difference between a waveguide and a horn in relation to this cab?A horn is a subclass of waveguide. "Waveguide" usually refers to shorter devices with rapid flares functioning primarly to control high frequency dispersion characteristics as opposed to coaxing low frequency response from a compression driver. In relation to this cabinet, it doesn't matter, unless you particularly want the crossover frequncy below 1 kHz. My 2370A horns in the pic are crossed at 800 Hz.



2) When tuning this box what is the best way to do it? (never done it before). As I stated above, you'll cut holes for tuning ducts as shown in my pic, and vary the length of those ducts to tune the cabinet. Modeling software will calculate an initial length, once the internal volume of the cabinet is known and the woofer chosen. After that, it's listening and measuring using a signal generator or test-tone disk. More precision can be achieved via additionally using a multimeter and a resistor to perform electrical measurements.



3) How much baffle cutting will be needed to go with the waveguide or a horn?Using the vintage exponential horns, your baffles are already cut to fit. For the waveguides I'm suggesting, the round horn hole above the woofer becomes a 10.5" x 5" rectangular cutout. To squeeze a 2370A horn in that space, you need to notch the flange a bit, as shown....

bamboo72
08-18-2007, 01:08 PM
Amazing. Thanks again Zilch. If you have a book out there somewhere that you have written I would buy it in a second! :D