Olympus C-50 surgery

[LikaComet]

Hello all,
I have a set of Olympus C-50 speakers that I inherited from my Dad. They have the S-7 set up.

I purchased a set of 077s to add to the system. I wonder what I should do for crossovers?

Also, the surrounds on the woofers need to be replaced. I wish I wouldn't have to recone if a new set of surrounds would do the trick. Any opinions?

Now here is where I possibly loose the bonds of reality. I've always been curious about the C-60 set up with their passive radiators. I'm a machinist by trade so I am accustomed to thinking out of the box so naturally I want to modify my speaker box. I can see a way to cut the front baffle out of the C-50s leaving about a 2 inch lip. Then I would mount the driven woofer and the passive radiator to a 3/4 inch aluminum plate that would be secured to the remaining 2 inch lip of the C-50 front baffle.

I wonder what the sonic difference is between the original enclosure vs the passive radiator set up. Or should I port the original C-50 enclosures. It just seems to me that it is a hit or miss proposition to locate the new port.

Thanks for your considerations, Doug

[Mannermusic]

Hi Doug -

You're sitting on a "state of the art" system for the 60s. Has real historical value. And, adding the 077 will likely make it sound even better. The LE15A in a large enclosure like the C50 - what, 8 cubic ft? - requires no port (passive or otherwise). I have a similar DIY rig (5.5 cubic ft) and it has a more linear response with no port . . . no accident JBL engineers didn't use a port. That's the whole deal with the LE (linear efficiency) series speakers - the port is not required. I'd just get the thing up to "like new" spec and see how it sounds - start with those surrounds for the woofers, as you suggest. Also, those older compression drivers often need fresh diaphrams to sound their best - would have to run a frequency sweep to see what the response is like (do they still have the red wax seals in place - never serviced?). As far as the crossover for the 077, you could use the old N8000 or use the schematic here on site to make your own. Some of us just use a simple capacitor (6 db/octave high pass) and an L-pad to trim the output, just let the horn turn itself off. Start with 1 mF and reduce until it sounds best. But, I'd get the LE85 up to snuff before doing anything. People love that driver! Find your local JBL pro shop for help - will save you $$ in the long run unless you have test equipment and experience. MM

[Zilch]

There are curves posted here on the forum demonstrating the difference between LE15A performance in closed box vs. ported and passive radiator alignments. It's now about 25 years since I "upgraded" S7 Olympus with dual 4" ports and some other stuff. The ports may be conveniently closed with ZilchPlugz™ to compare performance, available in the plumbing department of your local hardware store, disguised as plumbers' test plugs. Crossovers are 3110A and 3105. Yes, they're still here:

[nick]

Ok I'm a little confused. Are these speakers made by olympus or is that there model name?


Nick

[BMWCCA]

Ok I'm a little confused. Are these speakers made by olympus or is that there model name?

You got it; that there is a model name.

A leisurely stroll through this site's library would answer your question and maybe even help any other confusion. Failing that, there's always the Search function.

[LikaComet]

Thank you for your inputs all.

Mannermusic:
I was using the simple capacitor as the crossover between the LE85 and the 077. It was suggested to me that I use a T-pad instead of the L-pad to attenuate the 077. I'm not experienced enough to know why. Which is better I wonder? Something to do with impedance which I'm a little vague on.

Zilch:
Love the username. What kind of results did you have with the ports? How did you come up with the placement and the length of the ports? Or should I use a subwoofer if I want dramatic bass when I want it and the tighter transients of the infinite baffle when I want a more natural sound?
Also, what kind of drivers are you using behind your horn/lenses?

I know I'm asxing a lot of questions but what else can I do? Thank you guys.

[Zilch]

It's 2426J on the 2370A and the tweeter is 2404H. Woofer's 2235H.

The rest I'm gonna have to look up.

Search this forum for the curve of LE15A closed-box vs. ported in Olympus. I saw it recently....

[LikaComet]

Thanks Zilchman. I will look that stuff up.

Do you still have those speakers? Should a system like this be competitive with the L-300?

In regards to porting a cabinet. . . I wonder if the port placement is a matter of simply venting air pressure or if the vent should be at a point that back waves from the driver bounces of the back of the cabinet and out the port.

[macaroonie]

http://en.wikipedia.org/wiki/Bass_reflex

[LikaComet]

Thanks for the Wiki link Macarooni for the bass reflex info. I'll check that out later. Right now my wife is pulling my arm away from the computer so we can get out of the house.

Doug

[Zilch]

Do you still have those speakers? Should a system like this be competitive with the L-300?

That was my first JBL DIY, and they are still here. It was shortly thereafter that I acquired my first pair of 4430s, and I HAVE been meaning to get back to optimizing these ever since.

After that, I suspect they could give L300s a good run, yes....

[LikaComet]

That's great Zilchman, they sound like a part of your youth.

It has been suggested to me that I put new diaphragms into my LE-85s. What kind of real world improvements would that give me and what do you think that would cost me? I have to say that they are a bit shrill at higher volume but because the woofers are so constrained by the rigid surrounds if I had them refoamed they would be contributing more to the balance. If you know what I mean. The relationship between the LE-15 and the LE85 is all out of wack now.

But I am curious about what kind of improvements new diaphrams in the LE-85s would make.

[Zilch]

The original tangential-surround LE85 diaphragms are the smoothest in my experience, though their longevity is a function of how hard they have been worked and under what conditions. There has been some speculation of late that the current factory LE175 diaphragms are tangential and suitable, though we don't seem to have an unequivocal answer to that yet. The factory D8/16R2421 aluminum replacements are diamond surround. Another option is Radian aluminum hybrids with mylar surrounds, I believe they are. Note that I have intentionally left factory diamond-surround titaniums out of this mix of options.

In any case, it's standard practice for vintage LE85s that are actually going to be used to be opened up and rebuilt, even if the original diaphragms are reinstalled after verifying their condition. The foam damping pad in the rear cap is almost certainly mush, and may be replaced with a suitable felt. If the red wax seals are intact, a better strategy is to sell them to collectors who consider that an especially valuable "feature," and buy ratty LE85 or 2420 cores for reconditioning....

[LikaComet]

They've never been opened and they haven't been thrashed so to speak. What function does the foam damping pad serve. Could that contribute to the harshness that I experience when played at volume?

I still wonder if when the surrounds in the LE-15s are replaced and the woofers begin contributing to the mix that I won't have to crank the gain up to the point that the LE-85s are harsh. What do you think?

Do you have any input as to where I can obtain surrounds appropriate to these woofers? I'm a retired machinist so I am accustomed to working with tight tolerances. I would like to tackle the task of refoaming the drivers myself.

I can't tell you how much I appreciate the oppurtunity to discuss this kind of thing with knowledgeable peopleses with experience. This is interesting stuff.

Thank you, Doug

[rgwalker]

They've never been opened and they haven't been thrashed so to speak. What function does the foam damping pad serve. Could that contribute to the harshness that I experience when played at volume?

I still wonder if when the surrounds in the LE-15s are replaced and the woofers begin contributing to the mix that I won't have to crank the gain up to the point that the LE-85s are harsh. What do you think?

Do you have any input as to where I can obtain surrounds appropriate to these woofers? I'm a retired machinist so I am accustomed to working with tight tolerances. I would like to tackle the task of refoaming the drivers myself.

I can't tell you how much I appreciate the oppurtunity to discuss this kind of thing with knowledgeable peopleses with experience. This is interesting stuff.

Thank you, Doug

What amp are you using? I have a two way Olympus system with LE15As, 375 drivers and LX5 crossovers. There are no ports. They sounded thin with McIntosh 30 watt tube amps but sound fat with a 100 wpc solid state amp and the stuff on the walls is shaking long before they start to break up. I've always been a hard core Altec guy but I love these and I'll probably never get rid of them and convert them to three way one of these days.