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In Reply to: RE: Electro-Voice Regal lll posted by CraigI on January 15, 2017 at 13:01:33
Craig
Measuring low resistances becomes tricky, as you can check by shorting the test leads of your DMM together and see what reading you get. When set with a range low enough to read typical speaker impedances even the resistance of the test leads becomes a factor, as well as how clean the speaker terminals are, and how good a connection you have on them. So we're talking Ohms in the above test? It seemed like you switched uF for Ohms in one of the other posts. With the readings you have here it seems that the T35B's (which you previously stated were labeled as 16 Ohms) have both had their diaphragms replaced with 8 Ohm ones. The mids also appear to be 8 Ohm units. It looks like the original crossover is not appropriate anymore, and certainly the tweeter L=pad/treble control will not be either if they are 16 Ohm units, as turning it up or down will actually change the crossover frequency as well as changing the volume of the treble. The terminals on the mid and tweeter should be marked, look for the color of the washers at the base like on the woofer (though they may be faded by now). Some EV drivers are marked T1 (+) and T2 (-), some had push open spring loaded terminals with red or black plastic caps.
A correctly designed crossover and appropriate L-pads will certainly improve the sound of these speakers.
Paul
Follow Ups:
I made a mistake and put uF instead of ohms. Made a correction to the original post. Shorting the test leads of the DMM gave me a reading of 0.2 about a second later it read 0.1 and then a second later it read 0.0 I did clean the contacts with sand paper to get a good contact. The washers were painted over. I scraped the paint and there is a red and black washer. In my diagram the red is on the left side of both horns. So mid horn has green wire to red contact and black wire to black contact. Tweeter has yellow wire to red contact and black wires to black contact.
I am confused to say the least. EV literature says the T35, T35B & T350 tweeters are 16 ohms.
http://www.cieri.net/Documenti/Istruzioni/Electrovoice%20-%20Tweeter%20T35,%20T35B,%20T350.pdf
But replacement diaphragms are 8 ohms.
http://www.simplyspeakers.com/ev-replacement-speaker-diaphragm-89486a.html
Craig
This has been an interesting mystery as many pertinent details have been difficult to arrive at. I have: T35's here (in both 8 and 16 Ohm versions); T35B's (only 8 Ohm versions here); and T350's (only 8 Ohms versions here). The diaphragm is nominally inter-changeable between them (though there have been detail changes and refinements though the years). It's what you have in the driver now that counts and not what a spec sheet says, or even what it says on the driver. Back in the day The Grateful Dead had a sound system with an array of multiple T350's which got blown from too much power, so this is not an unusual problem with these drivers being over driven. From your DMM measurements you have presently: a 4 Ohm woofer; an 8 Ohm mid horn driver; and an 8 Ohm tweeter. Tomorrow I'll post a schematic for a new crossover (based on the data you have supplied) and hopefully this will help. I've never heard the Regals or any of the variants, but Dave has and he can give you his opinion as to how they would stack up against similar vintage speakers. IMHO If they're EV's they are worth fixing, but I grew up listening to EV horns. My main rig now are 6 ft. tall 300 lb. EV monster horns, so I'm coming from a hard core perspective.
Paul
Craig
From the info you have provided I would go with a new crossover following this schematic. Note that the part values are just ideals, so use the next nearest standard value available. Also note the L-pad which is pictured with the shaft pointing away from you, and with the solder lugs pointing down. The L-Pads would be inserted at the X in the schematic, and I left this separate from the schematic for simplicity.
Paul
Paul,
Thanks for the schematic! Just curious, what did you use for the low and high crossover frequencies?
I was hoping I could keep the speakers original in design but update it with new caps. That's not turning out to be the case. I checked with Bob Crites. He says he has NOS 16 ohm T35 diaphragms but wants $100 each installed. Through my research I have come to believe the MR-10 horns were 16 ohms in the Regal III. That would make the 5.7uF mid cap a little closer to what is expected. Since I'm not willing to drop $200-$400 on new 16 ohm diaphragms and since mine measure 8 ohms and new 8 ohm ones are readily available it makes sense to change the crossover & L-Pads to work with what I have.
What is the reason for the 16 ohm and why did 8 ohm become common? The following are the parts I'm considering. The L-Pads have me a little confused. There are different wattages & mono vs stereo.
https://www.parts-express.com/dayton-audio-dmpc-56-56uf-250v-polypropylene-capacitor--027-425#!
https://www.parts-express.com/dayton-audio-dmpc-20-20uf-250v-polypropylene-capacitor--027-436
https://www.parts-express.com/jantzen-audio-037mh-18-awg-air-core-inductor-crossover-coil--255-222
https://www.parts-express.com/jantzen-audio-065mh-18-awg-air-core-inductor-crossover-coil--255-236
https://www.parts-express.com/speaker-l-pad-attenuator-15w-mono-1-shaft-8-ohm--260-250
Craig
Craig
The schematic I posted uses 1000 Hz for the low end and 3500 Hz for the high end like the original crossover did, and it's also a 1st order crossover. The parts you link to for C1,C2,L1 and L2 should be fine. I'm not sure how a "stereo L-pad" applies here, as you want a separate mono L-pad on each mid horn and horn tweeter. Dave wanted me to remind you that the L-pads for my schematic should all be 8 Ohm units, and it looks like you are aware of that. You pay more for higher Watt L-pads so budget according to the amp you are using.
16 Ohm speaker drivers were more common in the vacuum tube amp days as tube amps had an efficiency advantage with higher resistance drivers, while transistor amps had an efficiency advantage with lower resistance drivers. The Regal seems to come from that time in the late 60's when the transition from tubes to transistors came about in the market.
Does the schematic make sense? Note that when a wire crosses over another wire, they are not connected to each other at that point unless there is a dot at the cross road. I used the schematic format from one of the calculators we discussed here for the sketch, and I corrected an error where they omitted a dot where the mid minus connects to the amp minus. It's a trivial point but it may have confused someone not used to reading schematics.
Hope all this helps
Paul
I haven't taken the time to try and decipher the schematic. I'm guessing it is the same way the speaker is currently wired.Mystery Solved?
I was looking around the Great Plains Audio website and discovered this:NOTE 2 - When the original 24 ohm impedance is not required, use the diaphragm manufactured for the Altec Lansing 299-8A, Altec original part #25884 (8 ohms), or the diaphragm manufactured for the Altec Lansing 299-16A diaphragm, Altec original part #25885.
I had no idea speakers went above 16 ohms. When I first found the KBapps calculater I played around with it trying to get the cap values to come out to the numbers I had on the caps. If you make the tweeter = 16 ohms, mid horn = 26 ohms and woofer = 4 ohms you get a C2 value of 5.667265. It also shows L2 = 0.63662, so I might be able to reuse one of the original coils if I could verify the value.
Edits: 01/20/17
Another newbie question. The woofer surround has separated from the cone in two places. How do I re-attach the surround to the cone? I got some cloth surround sealant from Vintage-AR but now I'm not sure if this is what I should be using. It seams this sealant is used to keep air from flowing through the cloth surround. Does it also attach the surround to the cone? If it does attach the surround to the cone do I apply it between the cone and the surround?
Craig
Try a bit of the surround sealant and see how it works. In the past I've made my own speaker dope for this when the surround on one of our Pioneer CS88 in the HT started to separate. I used some DAP silicone rubber in a tube, and I thinned it with xylene as is said on the label, and it worked fine. Silicone rubber comes in different colors (looks like your project would need clear) and can be thinned with various things. I used the DAP because of the xylene which seemed a milder solvent than acetone, and I didn't want to melt the rubber surrounds on the Pioneers, but this is likely not that much of a concern on the accordion surrounds on the EV woofers.
I love the smell of rosin core solder in the morning! It smells like music!
Paul
Paul,
Crossover parts are on order. The smell of rosin core solder in the morning will be soon. Any recommendations on solder? Any reason to replace the wires in the speaker? What do you think of the possibility of the mid horn being 24-26 ohm originally; makes the calculator work.
Craig
Craig
Solder has tended to go lead-free in recent times. Radio Shack has (or at least they used to) Lead- Free Silver Bearing Solder 96/4 # 64-025 but ti's difficult to work with as the solder joints tend to look "cold" (read: not nice and shiny). So it can make an impatient expert into an amateur. I have a lifetime supply of good old Kester "44" Sn 60 which always gives good results, but I dunno if you can still buy it.
Wire: Monster XP is good, reasonably priced and easily available.
A check with your DMM of the original L-pads may reveal more of the mystery, though you should disconnect them first. A reading between the center lug and one of the other ones should reveal either a very low reading or the maximum value of the L-pad as you turn the knob to the end points. Also look for a resistor added to the L-pad which may affect the circuit impedance. To re-iterate: you stated that the T35B's are marked as 16 Ohms units, but measurements show them to currently be 8 Ohm units. If the L-pads don't match the driver they will actually change the crossover frequency as the knob is turned up or down, and it's difficult to imagine EV designing it this way.
Paul
PaulI measured both L-Pads. The low readings are 0.2 and 0.7 ohms. The high readings are 104.2 and 103.8 ohms. Both are disconnected.
Craig
Edits: 01/26/17
Measured my new L-Pads 0.1 to 7.5 ohms
Craig
This starts to explain some of the mystery of why the parts values n the original crossover didn't seem to make sense, and the nominally 100 Ohm L-pads seem to account for the missing Ohms to match the parts. As to why they did it that way I can only speculate. In the page of the 70's EV catalog I posted here they were expecting that DIY'ers would use a "building block" approach which would mean starting with a "full range" woofer in a suitable box which would be made. Later you would add a tweeter for some highs. After you had that awhile you would add a midrange horn for "presence". The mid horn and tweeter were presented as add on tone controls.
As you'll be nearing a time when you can compare the new crossover to the old one, it might be time to move this up page to a new thread, as we're stretching the limit of how far we can go to the right down here. Hopefully the speakers sound better!
Paul
Did you notice that the two caps are connected (in series?). Is that usual?
First, I forgot to mention that 8 and 16 ohm diaphragms were once available from EV`for the T35 but as far as I can tell they discontinued the 16 ohm more than 20 years ago.EV was bought out and so went the 8 ohm diaphragms too. But if Great Plains Audio did get the jig to make them, they are the best bet but they would be 8 ohm as far as I know. You could call to see if they do offer the 16 ohm and when they might have some. Forget e-mail. They aren't good at answering them.
Any new T35 diaphragms you see on line are cheap generics unless they say NOS or new old stock.
The 16 ohm T35 and T35B are a fairly common item on E-bay but unless your lucky I wouldn't expect to see a pair for under $100 and then it's risky unless the seller gives a DCR reading for each or you may end up with another headache.The T35B is just a less efficient version of the T35 with a smaller magnet and it was used with other drivers that were less efficient than some of their other drivers.
No sense in cutting back a T35 like crazy with a pot when the T35B was already less efficient.The T350 used the same diaphragm but it was more efficient than the T35 with a bigger yet magnet and it has a larger horn. Some consider it to be one of the best vintage tweeters even if it doesn't go much beyond 15KHZ like modern tweeters. What it does do it does well.
The caps aren't really in series. Yes, one end of each is tied together but that's the plus input to each and not a series connection. A real series connection would the two caps wired like they are BUT without the third connection that feeds both caps.If they were in series the resulting value would be about 1.90uf. And since you need a cap for the mid and a cap for the tweeter that would leave you with only one cap.
I do see that the 2.84 has one wire on one end and two wires on the other end. The two wires are tied together and because the cap is marked 2.84 that can only mean that there are two 1.42 caps in that bundle in parallel that adds the two values. The other end would be a common connection for the two caps.
Edits: 01/16/17
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