AR10Pi crossover schematics

[KlausDK]

Hello All

Just bought a set of AR10Pi speakers here in Denmark, the high range tweeters are not working, but new are available from different sources, ABtechservices.com looks to me like a good choice?

Does anybody have the schematics of the complete crossover for this speaker? Or does anybody have experience with "restoring" the crossover, more specifically replacing the capacitors, which I guess must be pretty much dried out and off-value by now after 25 + years.

BR Klaus

[Guest Bret]

>Does anybody have the schematics of the complete crossover for this speaker? Or does anybody have experience with "restoring" the crossover, more specifically replacing the capacitors, which I guess must be pretty much dried out and off-value by now after 25 + years.<

I'll tell you everything I know all at once. That shouldn't take too long, but it will make for a long-looking single message.

I do not have a schematic.

Working on the crossovers in these is an object lesson in patience. There isn't much room and the soldering terminal strip that makes it very easy to connect components while the crossover is on an assembly line makes it very, very hard to cope-with once installed in the cabinet. They could teach a foul language class using these for motivation.

Tweeters: I have no experience with the current replacement tweeters offered by ABTech. My experience with older replacement tweeters was that they were awful. Not only did they throw the cabinet out of balance but they were harsh and terrible - even with the original capacitors (which were bad and had gone "dark")still in the system.

Someone else may know something more, but all I can recommend from experience is that you try to get original drivers. It took well over a year of watching eBay, but I was finally able to get some of the first generation (light domed) tweeters. These I compared to second-generation (black domed, no foam) and the later replacement drivers (black domed w/foam). The differences in the black and white domes were evident, but not earth-shaking. The originals were best, the second-generation were a close second and the replacements were an extremely distant third.

Capacitors - First: 100, 40, 20, and 10uF; I'll skip much detail;

Two pairs of 10pi speakers under simultaneous repair:

Don's; Early production, Sprague Compulytic caps, sound; dark and foreboding

Mine; Later production, Callins caps, sound; really bad, peaky

Common experience: Supertramp's "Even in the Quietest Moments", remastered Redbook - completely unlistenable; made you grind your teeth with raspy highs.

Based on reading here, I chose Solen 400v metalized poly caps and replaced all of mine. At first it was amazingly awful. Everything went "back into balance" top to bottom, more or less, but the experience was like nails across a chalkboard. Also based on reading here I let them screech through a weekend and they mellowed some. Encouraged, I let them play and play and play. Hundreds and hundreds of hours later there is a barely perceptable harshness in some frequency range as yet unidentified.

At this stage when comparing Don's to mine; Mine were far, far more "open" sounding and a great deal more detailed even when my attenuators were down and Don's were up. Mine were substantially brighter even attenuated.

Don then replaced his original Spragues with new electrolytic caps. Immediate improvement. Everything in his cabinet goes back into balance. Now with my attenuators down 3db and his up there was little difference in "amount" of high-end, but mine were clearly "cleaner" (we attribute this to the noise-floor of the caps, but we really have no technical way to confirm it).

Encouraged by an experience I had with another set of speakers, Don opts for "audiophile" Zen capacitors from North Creek and installs them on one speaker, by-passing (installing parallel) his 10uF with a "Crescendo by-pass cap." He decides to go "all the way" and replaces mid and tweeter wire with super-duper silver wire and increases the gauge of the woofer wires to 10 and puts better binding posts (from old Allisons) on his.

Now we A/B his to mine -> His sounded slightly less bright. What I can only call the "noise floor" moves several feet below the basement (they are very very clean and clear with no perceptable "fuzz") and his sounds really, really good.

Unable to contain himself, the following day he does a "down and dirty" capacitor change in the other of his speakers without the super-duper wire and without removing the crossover from the cabinet.

We then A/B again, his to his, and his to mine. The kind of differences we heard between his were so small, and so subtle, that we can't even be sure they are there, but over time we believe that one of his midranges is not "matching" the other. Two additional driver swaps later we are able to get his speakers closely matched and sounding wonderful. If the wire exchange did anything at all the effect is so small as to make it questionable.

However, A/Bing his to mine made it difficult to listen to mine, anymore. We don't know why, perhaps it was the "by-pass" capacitor, or maybe some difference in the contruction of the capacitors (as asserted by the capacitor manufacturer and explained by a materials expert who frequents this forum). Even after two hundred or more hours on mine, his immediately sounded better in a way I can only describe as "less electronic" or "mellower" or. . .something.

Common experience; Supertramp's "Even in the Quietest Moments", remastered Redbook - marvelous. No rasp, just very, very "airy."

At this point he "let" me take mine home! ;-)

One of his 4PDT switches went bad and new was ordered from Digikey. I suggest that you somehow test your bad tweeter to be certain that you aren't fighting a switch problem as I have 3 of 6 switches going bad in my AR-9s and another has gone bad in one of his 10pi's. (note, they aren't all 4PDT switches)

Having fooled-around with (read: swapped around a lot) woofers it is my opinion that unless one of yours is damaged, you resurround them ONLY and only when they need it.

Some say that you can't hear the difference in a Solen and North Creek Zen capacitor. Note that not a single soul who has ever tried it says that. Not one. I suppose mass hysteria and collective hallucination is one possible explanation for our positive shared experiences, but the other explanation (that there is a difference)seems to make more sense. Instead of telling you why it can't possibly be true, or why it is, I'll just testify that I experience the difference for reasons I can't explain.

--------------NOTE NOTE NOTE ----------- a few things:

One: It is now Don's and my opinion that the 10pi's may be a tad too bright with poly caps. Just a tad. Maybe. Having said that, neither of us would ever consider going back to the way they were, we just attenuate them.

Two: Although there was a striking difference in the electrolytic and poly caps, the electrolytics were inexpensive and were never given hundreds of hours to form and "settle-in." Using either designer electrolytics (Black Gate, certain Nichicon low-ESR, or other) or a combination of electrolytics and poly or film-and-foil caps for by-passing might get the same "clean" result without changing the brightness. We just don't know from experience.

Considering how mine are placed (well off the floor, away from the walls, tweeters just above ear level) in a relatively live room, it is reasonable that I would have to attenuate the tweeters.

It is very possible that using poly caps, some adjustment needs to be made for the lost resistence of the old capacitors, particularly on the 100uF capacitor where the ESR may have been a third or a quarter of an ohm it may have prevented an output peak. We don't know this, but there is reason to suspect it.

The ESR of the 2500uF capacitor is probably a really important design component. For that reason, until I learn what the ESR of the original capacitor was (probably up-to half an ohm) I am not replacing it. I may change my story once I replace it, but as of now I don't think I can hear a problem being caused by this capacitor.

There is a 10 ohm and 15 ohm resistor in the crossover. I would replace those. It is possible that some of the differences we think we might hear between Don's speakers is because the resistors have been changed in one and not the other. This is highly unlikely, but resistors are cheap.

The poly caps are for-the-most-part much, much larger than the originals and two of them are a challenge to find room for on the original board. You just have to "find" a spot.

Lastly, whichever capacitors you choose to use I feel sure you will be happy with the results. Since specs on most of these components were +/- 10% there is only a limited amount of being ultra-careful that makes sense.

That, in a nutshell, is just about every useful thing I know about fixing a 10pi. I even threw-in some things of limited usefulness, just for fun.

Bret

[KlausDK]

Dear Bret

Thank you very much for your comprehensive answer regarding capacitor replacement. My tweeters are with black caps, both tweeters are silent and one of them is clearly damaged. I will take the other one out to see if it is working and the malfunction is caused by the switch. I will be watching eBay first to see if any tweeter(s) should emerge.

Once again, thanks for the answer

Klaus

[KlausDK]

Hi Bret and all other AR-10Pi owners

Since it seems that there is not a Crossover schematic around for this speaker, I am doing my best to put one together. By combining the patent information for the bass enhancement patent and the midrange/tweeter schematics from AR-11, and off course inspecting my speakers inside wiring, this is how far I have come by now.

The interesting thing (in my opinion) is, that the signal for both high and mid drivers is passing through the 2500 myF capacitor/10 Ohm resistor. This leads me to beleive, that it would be worthwile to try a polypropylene bypass capacitor on the 2500 myF capacitor of 10+ myF to see if that would improve the sound in the high register, is that something you have tested?

BR Klaus

[dynaco_dan]

Hi Bret and Klaus;

I certainly enjoyed reading this very interesting topic today.

I never had the opportunity to even hear these particular great speakers, but I enjoyed following the steps you've taken.

It is all about what we end up hearing, in the end, that's what's important.

[Guest Bret]

>I am doing my best to put one together<

Klaus -

Hold that thought.

The JPG you provided seems to be based on the tweeter and midrange schematic from an AR-11. A 10pi does not attenuate the tweeters and midrange with resistor-banks, but changes taps on the transformer.

Wait just a little while and I hope that all will become clear.

Bret

[Rlowe]

Hi BR Klaus

The following has taken a little while to prepare but if you look at the attachment you will find that it includes three sketches. The sketches are a bit "smudged" due to the JPG compression, but this allowed me place the 3 sketches in the one file.

Sketch 1 - This is a pictorial of the 10pi, its basic crossover configuration and its relationship to the AR11.
Sketch 2 - This is a sketch of the crossover components in the box.
Sketch 3 - This shows the connections for the swithes used behind the front panel for the Woofer Environmenal Control, the Midrange and the tweeters.

This is a copy of the original components of my 10pi.

I hope you find these sketches useful.

An extract from the patent document describes the purpose of the capacitor;
<>>

I'd like to thank Tom Tyson and Bret Thiel for their assistance in preparing the sketches. It was fun.


http://www.classicspeakerpages.net/dc/user_files/1027.txt
You can save this "txt" file, using the "save as" item from a menu which appears if you use your RIGHT mouse button. Then rename it a 1027.pdf file, or any other name as long as it has the .pdf suffix.

<><><><><><><><

22 Sep 2014 UPDATE.

Following Kim's (kj2005) posting # 18 I have decided to provide an update.

The attached pdf < AR10pi-CircuitNotes Version 1.1 Sep2014> updates 1026.pdf (& 1027.pdf).

Sketch 1 - This AR10pi components Schematic (V2.0) has been changed to refer to the 10pi crossover only.

o - It has been changed to match the wiring diagram in Sketch 2.

o - Reference to the AR-11 has been removed.

Sketch 2 - This is a diagram of the crossover components in the box.

o - No wiring has been changed.

o - Edits have been added to make it easier to read.

- The Autotransformer has been rotated to have the connector numbers to match the installation.

- The circuitboard for the switches has been rotated so that it shows the connections from the back of the board.

Sketch 3 - This shows the connections for the switches used behind the front panel for ;

o - the Woofer Environmental Control

o - Midrange

o - Tweeter

Hope this helps

1026.pdf

1027.txt

AR10pi-CircuitNotes Version 1.1 Sep2014.pdf

[dynaco_dan]

>Hi BR Klaus

>

>The following has taken a little while to prepare but if you

>look at the attachment you will find that it includes three

>pictures. The picture is a bit "smudged" due to the

>JPG compression, but this allowed me place the 3 sketches in

>one file. (you can use the Adobe Reader

>"View/rotate" to manipulate the 3 sketches when you

>look at them).

>

>Sketch 1 - This is a pictorial of the 10pi, its basic

>crossover configuration and its relationship to the AR11.

>Sketch 2 - This is a sketch of the crossover components in the

>box.

>Sketch 3 - This shows the connections for the swithes used

>behind the front panel for the Woofer Environmenal Control,

>the Midrange and the tweeters.

>

>This is a copy of the original components of my 10pi.

>

>I hope this is useful.

>

>I'd like to thank Tom Tyson and Bret Thiel for their

>assistance in preparing the sketches. It was fun.

>

Hi there;

All I can say is, WOW.

What a great job you did with the drawings.

Certainly beats the old hand drawn sketch on the back of a pack of cigarettes, by a mile or kilometer or two.

Excellent reference work.

Thank you, fellas.

[Guest Bret]

No need to thank me, Richard. You did absolutely all the work, I just admired from afar.

I have every reason to believe that these will come-in extremely useful over the years.

Bret

[KlausDK]

Hi Richard

Thank you so much, this is really impressive and it will certainly save me a lot of work.

I will be very grateful if could I persuade you to send me the uncompressed dokuments to my email address:

klausm@netadresse.dk

Best Regards

Klaus

[Guest Bret]

>Thank you so much, this is really impressive and it will certainly save me a lot of work.<

We really can't thank Richard enough. He has hours and hours and hours in this. . . this. . . unique zoo of wires and configurations.

Almost makes you want to try to build one from scratch, doesn't it?

Bret

[KlausDK]

Hi

Acquired another set of 10Pi this week, When I removed the woofers for refoam, I realised, much to my surprise, that the X-Overs were turned 180 degrees compared to what I have seen previously, pls see pictures. The picture to the left with the transformer in front (courtesy of Tom Tyson) and my new 10Pi to the right with the transformer in the back. These are relatively early versions of 10Pi SN around 4000 and messing logo badge. Cabinet and woofer dated 1975.

Anyone else seen that position of the X-Over in a set of 10Pi?

BRgds Klaus

[sidecar]

Hi

Acquired another set of 10Pi this week, When I removed the woofers for refoam, I realised, much to my surprise, that the X-Overs were turned 180 degrees compared to what I have seen previously, pls see pictures. The picture to the left with the transformer in front (courtesy of Tom Tyson) and my new 10Pi to the right with the transformer in the back. These are relatively early versions of 10Pi SN around 4000 and messing logo badge. Cabinet and woofer dated 1975.

Anyone else seen that position of the X-Over in a set of 10Pi?

BRgds Klaus

Hi Klaus

In my set too!

Mine serials are around 13000 and plastic black logo. Certainly have been made in Europe and the switches haven't red caps. If you want we can exchange pictures of our speakers for more details.

Brgds, Claudio

[KlausDK]

Hi Klaus

In my set too!

Mine serials are around 13000 and plastic black logo. Certainly have been made in Europe and the switches haven't red caps. If you want we can exchange pictures of our speakers for more details.

Brgds, Claudio

Hi Claudio

Here's a picture of mine, the woofers are out for refoaming. The switches has red plastic covers.

BRgds Klaus

[kj2005]

Hi BR Klaus

The following has taken a little while to prepare but if you look at the attachment you will find that it includes three sketches. The sketches are a bit "smudged" due to the JPG compression, but this allowed me place the 3 sketches in the one file.

Sketch 1 - This is a pictorial of the 10pi, its basic crossover configuration and its relationship to the AR11.

Sketch 2 - This is a sketch of the crossover components in the box.

Sketch 3 - This shows the connections for the swithes used behind the front panel for the Woofer Environmenal Control, the Midrange and the tweeters.

This is a copy of the original components of my 10pi.

I hope you find these sketches useful.

I'd like to thank Tom Tyson and Bret Thiel for their assistance in preparing the sketches. It was fun.

Hi Rlowe,

I have received a very damaged pair of AR10pi's. The cabinets has been used with drivers which had larger diameter than the originals and the mounting holes has been destroyed by an electric jigsaw. The original crossover has been resoldered and one capacitor is missing.

I have disassembled the speakers and have started to rebuilt the wood-cabinets. Piece by piece. After that I searched the AR10pi schematic and found your work and drawings.

Great work you have done for all of us!

I have found one difference between the "Common components" schematic drawing and the other document " An AR-10pi Components".

If you take a look at the later, the midrange should have a connection from the 40uF Sprague directly to the minus of the speaker unit, but the "An AR-10pi components" paper shows that there are a connection from "6" to the sprague capacitor and then a connection from the 40 uF Sprague to the 0,044mH coil which after that is connected to the plus on the midrange speaker.

On the schematic paper the 0,044mH coil is connected directly to plus (+) on the midrange, and the 40 uF to the minus (-).

I have seen a similar way of wiring on other crossovers, but is the AR-10pi schematic drawing right or is it the actual component arrangement that's correct?

Thanks in advance

Kim

Denmark

[Rlowe]

Hello Kim,

Thank you for picking up the discrepancy.

From talking to RoyC.

" The junction of the two coils (one parallel and the other series) with the mid cap is the same in the AR-3a and 3a

Limited. In the 3a it all happens on the -ive side of the circuit, and in the 3a Limited it happens on the +ive side. I

have never seen them on opposite sides of the circuit as shown in the CSP AR-11 schematic... though it should sound the same"

Hope this helps.

[kj2005]

Hi Rlowe,

Thanks for your answer.

I have received original info about the AR-10pi crossover and accordingly to the data I have drawn the schematic for own use . see attached

Thanks again for your work with the AR-10pi crossover.

Best regards

Kim

[kj2005]

Original AR-10pi dokumentation over the wire colour code's .

Midrange: Orange wire to + positive terminal......Brown wire to - negative terminal

Tweeter : Yellow wire to + positive terminal........Blue wire to - negative terminal.

As Roy says next , AC signals to the woofer and midrange shares the same polarity, and the tweeter receives the signals with reverse polarity.

Rgds. Kim

[RoyC]

<<Normally you phase invert the midrange when the woofer uses 12 dB / octave .... and sometimes that the tweeter again has been phased towards the midrange when using 12 dB/octave (but not here).>>

Not this time...The tweeter is wired with reverse polarity relative to the midrange and the woofer in the AR-10pi and the AR-11. The mid and woofer are wired with like polarity. Richard's drawing is correct in this regard.

Roy

[Rlowe]

Refer to post #8.

[KlausDK]

The tweeter is wired with reverse polarity relative to the midrange and the woofer in the AR-10pi and the AR-11. The mid and woofer are wired with like polarity. Richard's drawing is correct in this regard.

Roy

Dear All

I have a set of later 10pi (aluminium/black coloured plastic logo plate) in for repair, and I have checked polarity on those, and they are wired like Roy says and as indicated on Richards drawings: woofer and midrange the same, tweeter reversed polarity.

Furthermore, the wire colours correspond to this, as posted by Kim:

Midrange: Orange wire to + positive terminal......Brown wire to - negative terminal

Tweeter : Yellow wire to + positive terminal........Blue wire to - negative terminal.

BRgds Klaus

[Rlowe]

Update to post #8

[kj2005]

<><><><><><><><

22 Sep 2014 UPDATE.

Following Kim's (kj2005) posting # 18 I have decided to provide an update.

The attached pdf < AR10pi-CircuitNotes Version 1.1 Sep2014> updates 1026.pdf (& 1027.pdf).

Sketch 1 - This AR10pi components Schematic (V2.0) has been changed to refer to the 10pi crossover only.

o - It has been changed to match the wiring diagram in Sketch 2.

o - Reference to the AR-11 has been removed.

Sketch 2 - This is a diagram of the crossover components in the box.

o - No wiring has been changed.

o - Edits have been added to make it easier to read.

- The Autotransformer has been rotated to have the connector numbers to match the installation.

- The circuitboard for the switches has been rotated so that it shows the connections from the back of the board.

Sketch 3 - This shows the connections for the switches used behind the front panel for ;

o - the Woofer Environmental Control

o - Midrange

o - Tweeter

Hope this helps

Hello Rlowe,

Thanks for the AR-10pi schematic update.

The determined speaker wire colour codes certainly helps, if you are about to reinstall the crossover, and you want get as close to the original schematic as possible.

Kim

[drewpo]

Can anyone tell me which type (NPE, Polyprops, etc) of caps are in the original 10 PI's?  I think I've read through every topic and have not found that answer.  Thanks guys.

[RoyC]

They are all NPE's.  Manufacturers varied.

Roy