Any Fried model R fans??

[Benjib]

I am going to go with Solen NP 100v electrolytic capacitors for the mid/low and and Solen 4.7mfd Fast Capacitors 400v PB Series Metallized Polypropylene for the high circuit. I do find the treble a little laid back and I read that the Solens caps are known to be be bright. But looking at the schematic, I wonder if the tweeter circuit caps should be 5.0mfd or 4.7mfd? I know Fried used 4.7mfd but could that be because that's all that was available? Why would (5.0) be noted? I am also curious about the low frequency circuit. The diagram shows one 80mfd capacitor but the board has two, 50+33 = 83uf. Wouldn't it be more elegant to install one 80uf 100v capacitor at this point?

 

[Nat]

Without any actual knowledge or experience of this situation, I suspect that the small differences are essentially meaningless. There are going to be slight variations in the impedance and efficiency of the drivers, and in the capacitance, inductance and resistance of the the other components, and I'd bet that the uncertainty in the effect of all those variances will nullify any particular precision in the caps you install. And that assumes you could actually hear any difference, which is not a given - this isn't a slam on your hearing acuity or whatever, but a recognition that all the parts of a system, especially the room, and placement of the speakers and the listener often swamp minor variations in the speakers.

 

[Benjib]

Thanks for your thoughts, Nat. The crossover components chosen by the original designer factored in impedance and efficiency of the drivers, and in the capacitance, inductance and resistance of the the other components... that's why it matters (to me) to get as right as possible. I'd feel the same way updating a classic sports car; that parts should be as true as possible to the original engineering/intent, outside of proven quality upgrades. Even then I could side with the all original crowd. In doing these Fried Model R II crossovers, I'd like to get it as right as humanly possible; that's part of the hobby for me. I'm not the 'close is good enough' type.

 

[Robint]

In post #68 I compared McCarty250 board with mine. I have 80mfd caps against his 83mfd. I have a 47mfd against his 50mfd cap. Agreeing with Nat I doubt if you could here the difference.

 

[Benjib]

Thanks Robint. I looked at post #68 but I don't see the comparison you reference.

My questions are not about audible difference, they are about crossover design which I am just learning. I know that the values don't matter much within a certain tolerance; The 47mfd vs 50mfd and 80mfd vs 83mfd. I guess I wasn't very clear in my questions. Do you think Fried wanted 5mfd caps but settled for 4.7mfd in the HF circuit as that was what was available? Or why else would be notate (5.0)?

For the LF circuit, I know installing a singular 80mfd cap is fine as opposed to two, one 47mfd and one 33mfd. I read the capacitance adds up but so does the voltage. In the 1970s, using two 50v caps (47+33 each at 50V) would add up to 80mfd with 100v, right? So I wouldn't want a 80mfd 50v cap in that circuit, I would want 80mfd 100v, correct? And there is no harm in leaving one of the two LF capacitor spots empty?

Thank you for your guidance! I want to make sure I get this right. I plan to enjoy these speakers for a very long time to come and want them as perfect as can be.

 

[Robint]

You can use a higher voltage cap, usually when ordering caps go to a higher voltage. Maybe Fried wanted 5mfd caps but used what he could obtain. Using an 80mfd cap to replace the 2 caps is fine. Maybe when these were built a 80mfd cap was more expensive than a 33 and 47mfd cap or maybe Fried used 2 caps so he fine tune the circuit. McCarty250 and yours are both higher serial numbers so in later versions Fried increased to 83mfd caps. All conjecture, however I have spent an hour in the man cave listening to my R lli and the sound great to me.

 

[Benjib]

thank you for your thoughts. Much appreciated. Is the improvement circuit possible by such an amateur as myself? I'd hate to hire out the job if I can possibly do it. I don't know understand the schematic well enough.

 

[Robint]

You can't be less of an amateur than I am. If you can tell one end of a soldering iron from the other you are good to go, I bought a cheap soldering iron and some good leaded solder. I worked around the board replacing one cap at a time. That way I didn't make any mistakes. The only difficulty was deciding where to connect the 0.47 mfd cap in the tweeter circuit after removing the 10 Ohm resistor. The 3 10 Ohm resistor and the 2.2 mfd cap I put inline right behind the tweeter. So far I am happy with the result!

 

[Benjib]

I finally got around to getting a closer look at my crossovers ahead of ordering replacements capacitors. Turns out I was mistaken about one thing - the low frequency caps. These are 25mfd + 47mfd! So do I replace with the same or go with what adds up to 80mfd as per the schematic?

 

[Robint]

Can we get a picture of the whole board.

 

[Benjib]

 

[Robint]

Definitely series ll, So yours have 72mfd, mine are 80mfd and mccarty350 are 83mfd. I would go for 80 or 83mfd. You can use 1 or 2 caps providing they add up to the required capacitance, your choice.

 

[Benjib]

Wonderful, exactly the feedback I was hoping for. I'll order caps tomorrow. The inline resistors for the tweeter circuit upgrade, I wish you had a photo of how that's wired. It looks very straightforward in the schematic but it would help me to see exactly how you did it. Might you have a photo?

 

[Robint]

No photo! All I did was take the three resistors and capacitor twisted the leads together and soldered them together. I removed the tweeter and cut the positive wire a couple inches from the spade terminal and soldered in the resistor and cap bundle, and reinstalled the tweeter.

 

[Benjib]

Ok great. That does sound easy. Is that .47 soldered in where it looks to be, same through-holes as the 3.9 and 4.7?

 

[Robint]

Looking at the circuit diagram the ,47 cap is from the + side of the 3.9 to negative side if the 4.7 caps which I worked out as soldering the .47 cap leads to the respective leads as in the photo.

 

[Benjib]

I did it. I did the recap plus the improved high frequency circuit. I used Solen caps, including their AchrOhmiC mil spec resistor and 400/630v metallized polypropylene. Total cost was about $100 Canadian. I'm stunned. I thought my KEF 104ab (also updated) sounded great but these Friend Model R series IIi are from another planet. I won't be able to sleep tonight. Thank you very much for the help, Robint. Here's a before and after and my room.

 

[Robint]

Glad it worked out. After you have a few hours listening to them give us your comments.

 

[Benjib]

Imaging, separation, clarity, articulation, range; all spectacular. I'm blown away. Horns, strings, piano, voices, they are in the room with me. The bass! Audible to the low 20s in my room . Who needs a true transmission line?! These are end-game speakers. I can't imagine anything better. I'm literally thrilled. Would love to know if anyone has ran a pair with tubes

 

[Robint]

I agree the Fried R lli are end-game speakers! The great thing for 50 year old speakers is that can get new drivers from Falcon Acoustics in England.