There are definitely times when you want to do a complete speaker analysis. Infinity speakers, old Yammies come to mind.
One thing to keep in mind is that we used to use a lot of bypass capacitors because big films were too expensive, and achieving good results was cheaper with big electrolytics and small films in parallel.
In any event, the proper way to go about doing this is to measure each driver's electrical and acoustic properties, in place, and simulate the crossover using something like XSim. I encourage you to go over to the DIYaudio forums where people snack on these issues all day and you can post pictures.
Best,
Erik
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Don't alter the component values of that crossover! Those values were chosen by extensive listening tests by the designer! Only replace the electrolytic caps with similar values of new poly caps. You can replace the two inductors (coils) with air-core types - if the originals are solid core. But again the replacements' values must be equal or very close to the originals - to maintain proper phase and amplitude response between the woofers and tweeters. |
I owned a pair of the Tangent RS2's back in the 80's. Excellent speakers. if a bit too "British" - laid back! Well, they are not JBL's! |
The stuff I read...Pink fish. caps..
If you want to save yourself a lot of time and buy a lot better XO call parts express, their cheepo 2 or three way will be a LOT better XO than the
1-4 versions I saw. OLD crossovers like that are easy to better just because of much more accurate parts and lower prices..
Rebuild if you like, Normally when you see a pile of caps like that in a two way, it was because the parts are SUPER cheap to BUY, it doesn't mean the parts are not of ok quality at the time. The builder cut cost by doing it that way.. Maybe even tuned left to right. If the two XOs are different looking, they may have tuned left to right.. VERY rare.. VMPS did it..
No two driver are the same.. Close but back then... Never.. Seas maybe..
Even Infinity settled for production XO.. left the same as the right.. Junk compared to today's stuff..
Regards |
Many Thanks for the thoughts from all of you! By way of update, I acquired a LCR meter and tested the mystery cap and all the others and now am pretty confident. Many thanks also to Josh of Madisound.com who was most helpful! I have made a schematic of the crossover which is available here if anyone is interested: https://drive.google.com/file/d/1CKneJ4wmWGvH751mDj8dha9Ma1dkNmqm/view?usp=sharingPerhaps it will save some time for anyone else with this speaker looking to recap.Ps- Erik I'm eager to look at that Xsim but first I have to dig out my old windows computer. |
You've got 12/18 slopes with impedance compensation on the woofer and frequency compensation on the tweeter. |
it seems to have a lot of caps for a two way crossover (8 in five styles), plus 2 resistors and 3 coils. Modern designs I have looked at typically have two or three caps for 2 two way crossover. According to your schematic, seems like you can use a single 3uf film cap to replace the 10uf, 2.25uf, 1uf and 0.47uf. |
@imhififan ..... Quick question for you. I don't know this tweeter, so I have to ask. Have you seen the impedance curves of this tweeter? Are you considering the inductor to ground? Are you considering the 3 ohm resistor in series?
Not being familiar with the impedance curves of this tweeter, these questions need to be asked. |
@timlub
The OP ask why so many caps, isn’t those four caps equal to 3uf in value?
I mean the four caps on the left of 0.35mH inductor in his schematic!
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@imhififan Your basic advice is sound... It would put you in the league.... 2.7, but if the original caps are electrolytic and they change to a quality film, the ESR of 3 capacitors alone can be a difference of up to another ohm or more. ESR is measured at different frequencies, so you would need to take that into consideration also. If the op was willing to do some experimenting, its worth a try, but to just replace all of that with a 3 mic cap would not be recommended.
op @bruce19 The 2.25 mfd, 1 mfd and .47mfd add to each other to combine values, the 10 mfd after those then decreases that value. |
Correct me if I’m wrong,
2.25mfd, 1mfd parallel = 3.25mfd
3.25mdf, 10mfd in series = 2.453mfd
2.453mfd, 0.47mfd parallel = 2.923mfd
3mfd should be close enough, and I guess the 0.47mfd is not an electrolytic and has low ESR.
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3.72, 10mfd parallel = 2.711
But beyond that, I have to believe that they would not have gone to that expense to do it that way, a small film cap would be cost effective vs all of that mish mash. My head says that overall you are correct, but I'd want to run real measurements and see why they ran the .47 the way they did vs just putting it straight in parallel with the other parts. When building I tend to verify everything in measurements. |
Great dialog timlub and imhififan. Your raising some of the questions I have been wondering about as a novice in this arena. For instance is the capacitor only important as a capacitor or do its other properties such as inductance and resistance enter into shaping the sound. I am appreciating more and more why people get degrees in this stuff:-) Another question is what is the importance of the type of capacitor to the sound? Film, electrolytic, surface mount...these are terms I quickly ran into which brought me up short. Let me share a picture of the caps from this crossover. https://drive.google.com/file/d/1GPHoB3gnQhPUqh-ccHUbzXtPjyAgKBoG/view?usp=sharingI think these are all electrolytic except for the green one clearly labeled "filmcap" (Duh) and the little clear one which I suspect is called a surface mount capacitor because of its shape and size. So the question is does replacing a film cap or a surface mount with an electrolytic with the same capacitance make any difference with regard to it's function in the crossover. You will note in the picture is the infamous pink mystery cap that prompted the start of this thread, which has since measured at 2.25mF. I'd be curious if there is anyone out there who can tell me that the color code matches my measurement. For your entertainment here is a picture of the notes that resulted as I tried to decipher the color code. https://drive.google.com/file/d/1F6a-P8_wewgkkVqZXlnlbMiLfIwCBAfH/view?usp=sharing |
@bruce19 The pink cap is a film cap, most likely a mylar. If you are doing the work yourself, I would recommend replacing the parts with Polypropylene caps throughout. If they were mine, I'd do a complete crossover rebuild based on listening to the parts individually and measurements. Its hard to give much advice without a ton of information that we will not likely get on a thread like this. Good luck,
Tim |
@timlub As it turns out I have gone that route with guidance from the stellar tech support man, Josh, at Madisound I bought a mix of Solen and Claritycap polypropylene caps. It is worth mentioning that Solen is made in France and Clarity is made in England and the Tangent's Audax woofer was made in France and the KEF tweeter was of course made in England. Nice little symmetry eh?
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You'll find out if you nice symmetry when your finished. The folks at Madisound are nice folks, but through the years, I've learned to get it right, I had to do it myself. I didn't always get accurate advice. Hopefully, all will work out well for you. I started building speakers in 1979 and started in the speaker business in 1980. |
@I really appreciate your interest and input
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You will note in the picture is the infamous pink mystery cap that prompted the start of this thread, which has since measured at 2.25mF. I’d be curious if there is anyone out there who can tell me that the color code matches my measurement. The capacitor value is 2,200,000pF or 2.2µF which is within tolerance of your measured value at 2.25mF. Because the first and second digit both are red (2), that’s why the color band look thicker than other bands. The third band is green (5) represents the multiplier, the fourth band is white represents 10% of tolerance and the bottom band is red = 250V. |
@imhififan That is good news to hear your take on the value. The cap was somewhat damaged as I removed it from the circuit board so I was just a bit concerned about whether it would measure accurately.
@timlub What kind of speakers to you build? Do you do this professionally? I also built my first speakers in the 70's, 6x9" with whizzer cones in a shoebox sized wooden cabinet and lamp cord to be used as external speakers run by my parents protable record player. Can't say I pursued it much further when I got a chance to buy some used AR2's I was a happy camper.
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Hi, @bruce19 I started modifying speakers when I was a store manager at CMC Stereo. I visited the audiophile shops in the St. Louis area regularly. We had a retail store called SpeakerCraft that custom built speakers. In 1980, I took a job as General Manager at SpeakerCraft, we had a division called Marcof Electronics, we built Moving Coil head amps, cables, modified cartridges, tables and built several Amps and Preamps..
It was there that I established a fairly in depth knowledge of Speaker Design. I had a good enough foundation that over the years, I was able to expand my knowledge to a complete understanding of speaker design. The owner there had and still has a full knowledge, but when I left, I just hadn’t absorbed it all yet. I have done hundreds of repairs and builds in the past years, even here on Audiogon, I have done several modifications, a couple of repairs and a couple of designs for members. In my Listening room, I currently have an MTM with 6.8 inch woofers and a dome tweeter, I have a 3 way with a paper cone 10 inch woofer an aluminum 5 inch mid and a ribbon tweeter, I have a pair with the top end Heil AMT with a 12 inch woofer and I am currently enjoying a 15 inch woofer and 1 inch dome in a 2 way. These speakers are 86 db 4 ohm, 87 db 8 ohm, 94db 8 ohm and 95 db 5 ohm. So, that’s the best I can answer, what kind of speakers I build... As far as professionally building. My 15 inch 2 way turned out so radically good and most audiophiles would not believe a 15 and dome to be able to sound as it does, that I truly explored going into manufacturing. I bought domains, registered a name, but no shows, my industry contacts are as old or older than I am or worst... Dead. So, recently I bailed on that Idea. |
Smart move. Many years ago I was in the same situation only with turntables. Used some connections, pulled some strings, got into CES as a vendor with a (very) early prototype. That one long weekend seeing what the business is like from the inside turned me off so much, and happy for it, saved me what would have been an awful lot of emotional and more than likely financial pain. The idea that if you build a better mouse trap the world will beat a path to your door is so laughably off it could be a feature length Monty Python movie.
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@millercarbon
I hear ya, I have been to at least 20 C.E.S as a buyer, not as a vendor. Even on my end, it was easy to see how cutthroat it could be from the vendor side. Years ago, Randy Patton who briefly owned Threshold, Sumo, Meitner, PS Audio and a few others, recommended me to Martin Logan. I had a call from them asking me to come interview in Kansas. I had no interest in moving to Kansas and did not go for an interview, but that started me thinking about doing my own thing. I would still love to produce speakers, but as I eluded to earlier, I’m getting older. I would love to market this 15 inch 2 way.... At this point, not likely. |
@timlub Your 15 inch/1inch speaker sounds interesting, particularly coupled with the efficiency rating it sports. Have you considered selling it as a DIY kit? I was looking around and was surprised at the lack of selection of DIY speaker kits. Maybe a part of that problem is related to the fact that audio reviewers generally ignore kits. For instance if I had not come across reviews of the amp camp amp and the bottlehead crack headphone amp I would not have even considered kits. As it was I did build a Amp Camp Amp and am working on a second because it was fun and it sounds really good.I think that the urge to build and tinker is under exploited in this hobby. Too many people just think it is all about going out and laying down large sums for beautifully finished final products. There is nothing wrong with this mind you, but you don't learn anywhere near as much as when you get more involved.I for one might very well be interested in building a version of your speaker if it were available.
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The 15 stays between 5 and 6 ohms at all frequencies, the tweeter stays between 4.3 and 5 ohms. Any Audiogon member is Welcome to my home in Weldon Spring Mo (St. Louis area) for a listen. |
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@imhififan Wow! What a fine piece of information. Good detective work! Now I've got to decide do I go down the rabbit hole of comparing the sound of capacitors. Mmmmm.......very tempting
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I have a set of crossovers that I recently parted out of my Tangent TM1's, I am unsure if these are the same as the RS4's. I also have a pair of RS4's. Any comment on the difference, I know they use different drivers and are likely different.
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Sorry pooch2 I don’t have any experience with your TM1 speaker, so can’t offer much. |
