mark fader Posted July 16, 2019 Author Share Posted July 16, 2019 (edited) that's kinda what I'm thinking . i wonder if this is why jack frazier chose a pot instead of a L-pad . maybe that is why he was able to get this kind of sound out of this kind of setup . hypothetically speaking , if this were the case then replacing the pot with a L-pad would be changing the sound . is that too much of a stretch to assume this is what he was doing ? then why do some models actually have L-pads , or at least appear to have L-pads ? has anybody ever taken a measurement / take one of those apart and actually seen what exactly it is ? or did he use pots just because ... and im looking waaaayyyyy to much into it ? Edited July 18, 2019 by mark fader Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 17, 2019 Author Share Posted July 17, 2019 is there anyway to get ahold of todd crane ? he should be able to give some incite on the matter ? Quote Link to comment Share on other sites More sharing options...
glens Posted July 18, 2019 Share Posted July 18, 2019 Maybe he chose a pot because it was less expensive than an L-pad, sizing it's values appropriately, designing the crossover to be right for what should be the proper position within a narrow useable range of motion, and called it a day? Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 18, 2019 Author Share Posted July 18, 2019 Maybe. I’m not discarding any thoughts right now. And that is most likely what happened. Or maybe they were out of lpads and he used a pot because that’s all he could get at the moment. It would be nice to know the real answer so I would know that replacing the pots with pads is ok. Quote Link to comment Share on other sites More sharing options...
glens Posted July 18, 2019 Share Posted July 18, 2019 You're overthinking it. Get the next-lowest resistance pot if not the stock value. Any difference between what you end up with and stock, make up that difference (near enough) with fixed resistor(s) between the third tap and the pair of common wires. You'll lose a little adjustment range is all. If you need to swap that range the other direction, just wire the resistor(s) between the other fixed tab and that lead instead of "floating" the commons. Very simple and correct enough, evidently, to restore what you've got. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 18, 2019 Author Share Posted July 18, 2019 (edited) I usually do overthink things. I can’t help it I’m a toolmakers by trade and we work in exact all the time and now it’s just a way of life. There is no “ good enough “ in our trade. It’s either right or wrong. I don’t have my notes in front of me but I remember only a 2 ohm difference between the pot and pad at the crossover( on the midrange out of the crossover ). Is that enough to make any difference? The terminals at the back of the cabinet ( amp in ) remained the same ( 7.5 ohms ) no matter if a pot or pad was installed. I never considered a resistor on a pot. The closest pot I can find is 25 ohms or 47 ohms. Edited July 18, 2019 by mark fader Quote Link to comment Share on other sites More sharing options...
glens Posted July 18, 2019 Share Posted July 18, 2019 The 25 + a 4.7 resistor wired like I said. The resultant overall value is 99% of the original, not counting tolerances which exist in all the old and new. The main thing functionally different is you'll lose the last 16% of adjustment. It'll be as if you'd put a positive stop in the original pot to limit travel a bit short on one end. If that area is where you need the range of adjustment, just put the resistor on the other end instead. There would be a minor difference in terms of knob/indicator location in that you'll still have full range of knob motion covering what would have been only 84% of range so each degree of turn will now cover the same ground as 0.84 degrees did before - a little better resolution than originally. If the knob is in the middle at original reference and you match up the physical end points, the new reference position will be slightly off-center electrically. If there's a reference mark on the face plate, determine the resistance from the wiper in that position to whichever end that doesn't have the outboard resistor on the replacement, match that value on the new and install the pot so the knob aligns with the reference mark in that knob position. Just looked at your photos. Is that screw through the middle of the coil a magnetic screw? If so and it wasn't so originally, then replace it with something non-magnetic. It isn't much metal but it could alter the value of the inductor nonetheless if magnetic. Just do exactly whatever was original in that matter. And you're absolutely sure nobody's been in there replacing parts with new that only resembled the old? It'd be a shame for you to have been fretting over finding something to match something which wasn't correct! Quote Link to comment Share on other sites More sharing options...
glens Posted July 18, 2019 Share Posted July 18, 2019 5 hours ago, mark fader said: I don’t have my notes in front of me but I remember only a 2 ohm difference between the pot and pad at the crossover( on the midrange out of the crossover ). Is that enough to make any difference? The terminals at the back of the cabinet ( amp in ) remained the same ( 7.5 ohms ) no matter if a pot or pad was installed. 2 ohms difference would alter both, the crossover frequency, and driver level by a couple dB. Unless your meter is using AC to measure resistance, at a frequency high enough to get through the capacitor, you could short the HF leads coming out of the crossover and still read 7.5 ohms at the input terminals (where you're measuring the woofer and its crossover inductor). So there's no value to you in that reading, in this particular matter. Quote Link to comment Share on other sites More sharing options...
glens Posted July 18, 2019 Share Posted July 18, 2019 One final notion: be sure to match any internal inductance (hopefully none) of the old pot with the new. A change there will be unwanted. Can Honeywell maybe put perfect replacement guts in those pots for you? Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 18, 2019 Author Share Posted July 18, 2019 (edited) i see what you are getting at about adding the resistor to the pot . although i don't understand it totally i understand that it will be a little different . at this point i don't know if i really care . to be honest , i just set the pots a little lower than full . so if i can get in that range then i will be satisfied . i never set them below half . but now they have new caps so if that changes anything then i will have to adapt . i still don't see me going below half . the screw in the coil is the same screw i took out . it is stock . that being said , i don't know what it is my dad bought the speakers new about 1985 . im pretty sure he never did anything to them . that is why I'm 98% sure they were stock when i got them . you lost me on the measuring part . im not really skilled at that kinda stuff . all i did was compare #'s . ( i had one cabinet with the original pots and one with new L-pads ) i haven't heard back from honeywell yet . they may be able to make replacements for me .that would be perfect if they could !!!! at this point it looks like the pot with a resistor is my best choice given what's available . i wonder if i could even hear the difference between the original pots , the l-pads , or the new pots with resistor ? maybe ill just set aside a saturday afternoon and try all thee and see if there is any difference to my ears . will the L-pads hurt anything ? Edited July 18, 2019 by mark fader Quote Link to comment Share on other sites More sharing options...
DizRotus Posted July 18, 2019 Share Posted July 18, 2019 1 hour ago, mark fader said: will the L-pads hurt anything ? I wouldn’t want one in the eye, but using, or not using , them should do no harm to your speakers or amp. Quote Link to comment Share on other sites More sharing options...
glens Posted July 18, 2019 Share Posted July 18, 2019 I shouldn't think any harm would come with L-pads. Certainly none from any equipment safety standpoint. Unless by harm you mean different-from-stock sonics which may or may not result from the change. When you stick your meter on the input terminals and take an ohms reading you're most likely injecting a small DC signal, the meter reads the voltage drop in that signal and reports the ohms required to produce that drop. DC from the meter will not get through the capacitor(s) in series with a high frequency driver, so anything behind the cap(s) is excluded from that result. Quote Link to comment Share on other sites More sharing options...
pzannucci Posted July 18, 2019 Share Posted July 18, 2019 Based on the simplistic crossover, you might want to just go with real 8 ohm lpads. It will probably manage keeping the crossover closer to the required impedance so that there is less shift. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 19, 2019 Author Share Posted July 19, 2019 I agree with all of you because I don’t know enough about the specifics to disagree. I’m out of town the next few days so I won’t be able to try any different set ups but once I get back I’ll see what I can do. Once I do I’ll post the results. In the meantime I’ll get some pots and resistors and work on the idea above. If I hear anything from Honeywell I’ll post it. Thanks you guys. Any others are free to chime in. I want to hear it all. Quote Link to comment Share on other sites More sharing options...
glens Posted July 19, 2019 Share Posted July 19, 2019 7 hours ago, pzannucci said: Based on the simplistic crossover, you might want to just go with real 8 ohm lpads. It will probably manage keeping the crossover closer to the required impedance so that there is less shift. The only thing I have against that notion (and I'd usually suggest the same) is that from what I not much know about Fraziers is that off-the-shelf parts were combined in specific ways to good result. Hence my focus heading to staying stock. Were it me, I'd try both ways and have them speak to a umik so I could see what I was hearing too. Or maybe just go stock and be done with it. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 19, 2019 Author Share Posted July 19, 2019 (edited) On the other site ( audiokarma ) there is a guy named snade. Who was in the same situation as me. He had the same pots and couldn’t find a replacement. He went with the l-pads and he claims that he can’t hear any difference. Others on the site who have heard them say the same thing. His reasoning was that other sevens he saw had l-pads. I would love to stay stock , but if I can’t I’m leaning towards the pads because that makes sense to me. I’ll let my ears decide once I try the other set ups out. Edited July 19, 2019 by mark fader Quote Link to comment Share on other sites More sharing options...
pzannucci Posted July 19, 2019 Share Posted July 19, 2019 3 hours ago, glens said: The only thing I have against that notion (and I'd usually suggest the same) is that from what I not much know about Fraziers is that off-the-shelf parts were combined in specific ways to good result. Hence my focus heading to staying stock. Were it me, I'd try both ways and have them speak to a umik so I could see what I was hearing too. Or maybe just go stock and be done with it. I'd generally agree. I bought a pristine pair of 20 yr old La Scalas, finished from the factory and I didn't like the sound. I didn't modify them because of the same reason. Not even an lpad or anything to balance the sound. Sold them because I thought they needed to stay stock. (I do kick myself for that though :-) ) Just looked and didn't realize there were two versions of Sevens. My Mark Vas were with the piezo and 5lb alnico magnet on the woofer (same as yours). 1975 version. The main thing with Frazier is the efficiency. The pots aren't going to add anything there. I rebuilt my Mark Va's into Seven's when I owned them and did seek out the midranges and tweeters if I wanted to build an Eleven since you could buy parts from the Frazier dealers. Nothing to gain in the efficiency area from the specs on the original drivers. The series crossover also didn't hurt and probably helped ease the use of the pots. I think a lot of the Frazier's gains were from simplicity and good drivers. On the tweeters, since they are capacitive (assuming piezo), the pot could probably be replace with a different value that was close and be reasonably good. If you are stuck, lpads would be the way to go if you want flexibility/ adjustability and can't find the pots. Also there are ways to sweeten up the tweeters that is worth looking into. Then you would likely want to switch to lpads on the tweeters. I noticed the Seven with the mud version of the woofer on AK and it appears that had lpads. Think that would have been a little newer. Quote Link to comment Share on other sites More sharing options...
glens Posted July 19, 2019 Share Posted July 19, 2019 16 hours ago, mark fader said: the screw in the coil is the same screw i took out . it is stock . that being said , i don't know what it is A straight-slotted rather gnarled screw? (Should be taken in a light-hearted manner.) I was just re-looking at the photos, getting the lay of the land. I noticed in the shot with the plywood the tweeter leads look for all the world like they're out of phase (or is it more PC to say the polarity is reversed?). I don't know what all's at the end of the leads heading out. I'd assume it's a two-way series second-order filter with all the drivers, or their volume controls, wired in to the appropriate side, each running what's left of full range from there. The crystal tweeters won't do anything on their own below a point a bit higher than the filter. And I guess the mid driver rolls off the upper end on its own, likely near the point where the tweeter kicks in. I still think I'd match the pot overall with one resistor either end of the pot. And check on that polarity thing. Is that what you want? Great, if it's what's called for. I don't know but would guess same polarity for mid and hi. But I don't know. However they factory wired it, I'd bet it weren't by chance. Unlike me, sitting at a solid 50% on this one :^) Quote Link to comment Share on other sites More sharing options...
glens Posted July 19, 2019 Share Posted July 19, 2019 No! Wait! Just gandering at the pic again and the tweeter's right. It's the mid looks polarity-reversed to me. Hadn't sufficiently narrowed down the root cause of what caught my eye earlier. Quote Link to comment Share on other sites More sharing options...
mark fader Posted July 19, 2019 Author Share Posted July 19, 2019 You are right. that’s original wiring. My top post has an original pic and a post pick. I don’t know why it’s that way but it was the same on both cabinets. I just copied what was there. I looked and looked at that and although it is out of phase it is how Frazier wired it up. I even confirmed that to another website post with pictures. His were just like mine except his had L-pads not pots. He says the pads are original. If I can find the link I’ll post it. Quote Link to comment Share on other sites More sharing options...
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