RTally
Speaker addict
Thanks. After doing some reading with the help of your prodding, I realized my post above only considered the electrical transfer function, not the acoustic transfer function. As an EE I've only worked on big equipment in power plants. I am playing catch-up on speakers. Reminds me of when I was in school, a long time ago.
Blue Shadow
Waiting for Vintage Gear from this century
homebrew
Super Member
Your response about the cap in the tweeter circuit fails to account for the natural low end roll off of the tweeter. True, one cap is an ELECTRICAL crossover that is first order, but the tweeter's ACOUSTIC roll off is likely 2nd order on the low end. Combine the two, and the result is a 3rd order (18dB) crossover. In a practical sense, a true 1st order crossover is very difficult to achieve and has severe limitations on the drivers and the listener.
tmsears
Active Member
Well if I had to give mine, I would say it sounds like a three way loudspeaker with for drivers, with a low mid-range being choked, a low range tweeter that has no restraint whatsoever and another tweeter that does the upper half of the highs disconnected.
tmsears
Active Member
Right now, even with the additional fiberglass and the aforementioned improvement in bass, the fiberglass only touches the magnet of the woofer and not anywhere close to the back of the tweeter. Sold I buy more still and cram away (within reason)?
Goggle1824
Well-Known Member
If the fiberglass is just touching the woofer magnet, again only from what I've experienced in mine that I've opened, which is all of them
, I suggest adding-in one more layer. The back of the woofer magnet usually compresses into the fiberglass so when the woofer is removed there is a woofer shaped depression. Use single sheets or pieces to help ensure none of the fiberglass hits or impedes the woofer cone or surround.
Hope this helps, thanks for keeping us updated, this information and your efforts will undoubtedly be helpful to others in the future.
Goggle1824
Well-Known Member
I believe it's only the late/late versions of the tweeters that possibly used any ferrofluid. Winslow's design was all about the "air spring" tweeters so none of the masonite tweeters through the almuninum circular plate or gold-ring tweeters use any sort of fluid, they are all 1 inch "air-spring".
The Time/Energy series and the later "Epicure" series (1 through 5) MAY use fluid, I would suggest HUW is the definitive expert on this, I'm referencing his site at Humanspeakers and its' descriptions as my primary reference.
sonofagun231
Member
Me, I would never have tried repairing what are really low priced woofers - they likely cost EPI all of $5 each originally (if that). You always run the risk of not actually restoring them to their original performance specs as seems to be the case in this incidence (or ASTBTCITI 
).
Repairing woofers only counts with expensive models and even then can be a cr-p shoot depending on hoo does the repairing. Replacing the old woofers with new ones with proper Thiele parameters at least insures the woofers will not be the problem and is quite inexpensive especially when you figure in your time & labor. Certainly playing around with the stuffing or wondering how some dowels change the internal volume isn't really going to be a solution to such a problem.
). Repairing woofers only counts with expensive models and even then can be a cr-p shoot depending on hoo does the repairing. Replacing the old woofers with new ones with proper Thiele parameters at least insures the woofers will not be the problem and is quite inexpensive especially when you figure in your time & labor. Certainly playing around with the stuffing or wondering how some dowels change the internal volume isn't really going to be a solution to such a problem.
If you are restoring any of the various EPIs and related speakers, repairing the original woofers is actually very important - the low end behavior of a driver is described by Thiele/Small parameters, but the high end is not. As already noted, the EPI woofer was designed with the correct sensitivity and smooth slope so that it could be mated with the tweeter with only a cap, and the result would be balanced and well behaved. You lose that matching when another woofer is swapped in, regardless of whether it matches the enclosure in the low end.
Driver behavior above the intended bandwidth can be problematic - often it's very peaky - and not all drivers can be run without a coil to roll off the high end.
Driver behavior above the intended bandwidth can be problematic - often it's very peaky - and not all drivers can be run without a coil to roll off the high end.
Goggle1824
Well-Known Member
I have other sets of more expensive and "well regarded" speakers that I don't enjoy listening to as much as my EPI/Epicure sets.
Speaking for me, myself only, I'm much more interested in the sound a system produces than it's cost, originally or currently.
Speaking for me, myself only, I'm much more interested in the sound a system produces than it's cost, originally or currently.
sonofagun231
Member
Blue Shadow
Waiting for Vintage Gear from this century
I believe it is pretty limited possibility of getting original speaker performance from any rebuild. Surrounds are a critical part of the speaker suspension and the drivers characteristics and today's surrounds might fit the intended driver, even work well with it but in most cases it is not the exact correct surround to provide exact restoration of the driver. Don't get me started on caps and selection thereof, using a fancy film jobby in place of a cheap generic 'lytic. Will not provide an as original sound.
All that aside, restoring all these old speakers to what works best for each person doing the work or paying for it will provide the happiness of being able to enjoy the speakers again because they don't remember how they sounded when new and they sound fine now and much better than they did with crumbled surrounds and dead caps.
Is there another company other than Magnepan that restores speakers to original specs for a unit that is over 25 years old? Everything else is a generally enjoyed rebuild of older speakers.
From this page: http://www.humanspeakers.com/e/epi100.htm
According to Hue early tweeters used Silicone heatsink compound, later used FF, he
has no mention of any without some sort of cooling:
http://audiokarma.org/forums/index....ted-dome-tweeter-issues.824827/#post-11674596
According to Hue early tweeters used Silicone heatsink compound, later used FF, he
has no mention of any without some sort of cooling:
http://audiokarma.org/forums/index....ted-dome-tweeter-issues.824827/#post-11674596
This blanket statement is really alarmist thinking, here Carl measures a refoamed EPI-110
and it measures just fine:
http://audiokarma.org/forums/index.php?threads/vintage-epi-frequency-response.562481/#post-7376302
Sure there are some systems with fragile drivers that fail and cannot reasonably be repaired but
a reissue has been made for the early .75" AR tweeter and one person seems to be doing reliable
repairs of them.
Blue Shadow
Waiting for Vintage Gear from this century
Doubt it is alarmist unless the reader is one that thinks doing all the AK-inspired rebuilding, restoration, retipping and saving the old crap from the dumpster is actually bringing it back to what it was. It is not. What results can be better, worse or about the same, but in most cases it isn't the same as what was produced back then. It is good we save this crap but thinking it is what it was is silly with all the differences. Can we hear that difference, highly doubtful as we don't have the originals in new condition to compare, so enjoy what you have.
In the case of the EPI-100 you can be sure that it is as close as anything
off the production line as long as you weed out bad parts through measurements.
You state concern about refoaming and the new foam not being exactly the same
when in the case of the EPI-100 it was made with both rubber and foam edges,
can't get more different than that.
Carl's measurement _proves_ that it can be done.
off the production line as long as you weed out bad parts through measurements.
You state concern about refoaming and the new foam not being exactly the same
when in the case of the EPI-100 it was made with both rubber and foam edges,
can't get more different than that.
Carl's measurement _proves_ that it can be done.
tmsears
Active Member
Yeah it is definitely not doing that. I have been sheepish in packing the fiberglass for fear of putting to much which whould be a waste of money as it is a little pricey for me and I am on a frugal budget right nowIf the fiberglass is just touching the woofer magnet, again only from what I've experienced in mine that I've opened, which is all of them
The back of the woofer magnet usually compresses into the fiberglass so when the woofer is removed there is a woofer shaped depression. Use single sheets or pieces to help ensure none of the fiberglass hits or impedes the woofer cone or surround.
Hope this helps, thanks for keeping us updated, this information and your efforts will undoubtedly be helpful to others in the future.
. But I can man up and buy a few more mini rolls if that is what it takes 
.
tmsears
Active Member
Afraid I am quite a ways away in southeast Oklahoma, but I appreciate the offer. I wish I had half the knowledge that you have, it would make diagnosing a breeze!
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