Re: We need Help for AR-3a speakers from Roy Allison and Chuck McShane

[mluong303]

"... Back in 1968, AR said that to achieve a “flat” response we need BOTH pots set to max increase AND a slight treble boost. The best way to do this is to cut the wires going to the wipers and solder them directly to the tops of the pot."

Hi Jerry,

I would like to find out Who at AR stated such a Big statement in 1968? To the best of my knowledge, it would never be from Roy Allison or Chuck McShane. AR-3a speakers at the time had just hit the market and still having the Alnico magnet AR-3 woofer with the #7 coil in them along with brand new pots which shouldn't have any problem for at least 5 years even in the worst climate environment such as Hong Kong!

Both Roy Allison and Chuck McShane are still alive and well, I hope. I wish they will post a short acknowledgment someday in the Classic Speaker Pages AR forum of their gratefulness to all the people around the World who had bought AR-3a speakers and still feel the 3a are the most wonderful sounding speakers after all these years...

These Gentlemen certainly can pin point the right way to bypass the pot in the tweeter path as well as the midrange path. Also they are the people who should be able to pick out an decent low cost tweeter available in the open market of their choice and change the crossover components to adapt it to the AR-3a design rather than we all hoping for a new 3/4" replacement tweeter being made in the uncertainty future...!

To Mr. Roy Allison and Mr. Chuck McShane, if you are reading my post, Please give us the right direction to keep our AR-3a speakers remain singing correctly for as long as we own them...

Thankyou in advance for any lead you may provide,

Minh Luong

mluong303@aol.com

[onplane]

Hi, Minh!

I think there is a little confusion here.

My comment was that "Back in 1968, AR said that to achieve a “flat” response we need BOTH pots set to max increase AND a slight treble boost." PERIOD

Next sentence - "The best way to do this (40 years later) is to cut the wires going to the wipers and solder them directly to the tops of the pot."

My point Minh, is today 40 years later setting the pots to max is NOT the same as it was 40 years ago. That is, setting those 40 year old pots to max today guarantees ... NOTHING!

The wipers are corroded and consequently can add resistance where none is supposed to be. Minh, soldering to the top achieves the intended flat response regardless of the amount of corrosion.

BUT ... by all means please feel free to ask those gentlemen if my logic is correct. In addition, according to a memo in our library Chuck McShane is reported to have recommended we completely eliminate the tweeter pot. Would you please verify the accuracy of that comment as well.

Thanks,

Jerry

[Guest tubesman]

>BUT ... by all means please feel free to ask those gentlemen

>if my logic is correct. In addition, according to a memo in

>our library Chuck McShane is reported to have recommended we

>completely eliminate the tweeter pot. Would you please verify

>the accuracy of that comment as well.

I can verify Chuck's statement about the tweeter pot. Chuck told me many times the elimination of the pot entirely added about 1 db to the tweeter level.

BTW, Chuck is still with us, but he's having a hard time with some health issues, memory is a problem, etc. Sadly, I doubt he'll be able to contribute too much more to the AR legacy.

BTW, I'm his nephew, that's how I know this stuff.

[onplane]

>I can verify Chuck's statement about the tweeter pot. Chuck

>told me many times the elimination of the pot entirely added

>about 1 db to the tweeter level.

>

>BTW, Chuck is still with us, but he's having a hard time with

>some health issues, memory is a problem, etc. Sadly, I doubt

>he'll be able to contribute too much more to the AR legacy.

>

>BTW, I'm his nephew, that's how I know this stuff.

Jim, thanks ever so much for that clarification.

I have followed your uncle's recommendation on tweeter pot elimination and my AR-3a's have never sounded so good.

I am the original owner and have enjoyed them for close to 35 years. I still listen to them everyday and as a matter of fact, … they are “singing” right now.

Sorry to hear about your uncle’s health issues. Jim, just let him know that all of us AR owners appreciate the work he did years ago in designing and building some of the world’s finest speakers.

In thinking about AR’s, I have to say it’s very rare that us engineers get to design ANYTHING that’s appreciated for so … looooong! Obsolescence usually sets in a matter of years. Your uncle’s work has already been appreciated for a long time and … there is no end in sight!

Regards,

Jerry

[Guest violin]

Jerry,I have been reading your comments about soldering the tweeter wire to the top of the pot and thus eliminating the pot from the tweeter path on the AR3a speakers. I have a pair of AR3s and wonder will this work the same way with them or is the cross-over different so as to prohibit this from being done to the AR3?

Thanks

Carter

[ToastedAlmond]

Tubesman,

Around 1987 or so I was on a trip with the military to Utah. Had a day off and me and a couple guys drove into the mountains by SLC. Found Heber City. Found Jim Fosgate's little storefront. Went in and asked the gentleman in charge if he was Jim Fosgate. "Nope, I'm Chuck McShane, and the AR-3 was my baby." The fellow I was with had AR-LST's at the time and I had a pair of AR-5's. Our jaws dropped when we realized we were in the presence of greatness.

Your uncle's a nice man and I hope he gets through his problems.

[onplane]

>Jerry,I have been reading your comments about soldering the

>tweeter wire to the top of the pot and thus eliminating the

>pot from the tweeter path on the AR3a speakers. I have a pair

>of AR3s and wonder will this work the same way with them or is

>the cross-over different so as to prohibit this from being

>done to the AR3?

>

>Thanks

>

>Carter

Hi, Carter!

In answer to your question, whenever we solder the wiper lead to the “top of a pot”, this is exactly the same as setting the pot to max increase BACK WHEN THE POTS WERE NEW.

Problem is that 35 to 40 years later the wipers on the pots are corroded. Consequently, when we set them to max increase, this corrosion adds resistance so the response is NOT the same as it would have been years ago. Soldering merely solves the corrosion problem, but leaves the pot in the circuit.

That is, the pot still dissipates energy through the 16 ohm resistance that’s in parallel with the driver.

What we are talking about in this thread, Carter, is ELIMINATION of the pot from the circuit. Now, the way we do this is we cut both the wiper lead AND the lead at the top of the pot and solder these two together. This takes the 16 ohm resistance totally out of the circuit and increases the tweeter output by approx 1.25db.

Will this makes the AR’s a littler brighter? Absolutely!

1.25db, however, is very close to the threshold of detection by the average person. That is, some people will notice a difference and others won’t. In my own case, I know I’m slowly losing the ability to hear much above 10K, so anything I do to increase the SPL in this range is … working in my favor.

Carter, I hope this helps ...

Regards,

Jerry

[Guest violin]

Thanks Jerry for your reply. I understand clearly now how to eliminate the pot entirely from the tweeter,and I assume that this method will give the same results with the AR3 as well as the AR 3a and not have any adverse affect due to other cross-over differences between the two models.Am I right to assume this?

Thanks ,

Carter

[onplane]

>Thanks Jerry for your reply. I understand clearly now how to

>eliminate the pot entirely from the tweeter,and I assume that

>this method will give the same results with the AR3 as well as

>the AR 3a and not have any adverse affect due to other

>cross-over differences between the two models.Am I right to

>assume this?

>

>Thanks ,

>

>Carter

Carter, the tweeter xover in the 3 and the 3a are essentially identical, so no problems with the pot elimination mod.

My recommendation is that you modify just one speaker as follows:

1. eliminate the tweeter pot entirely from the circuit

2. solder the wiper lead on the mid-range pot to the top of the pot

In both of the above you leave the pot terminals with the YELLOW wires alone. That is, the yellow wire leads are left as they were originally designed. It’s the other two terminals that come into play. Also leave just a little of the original wire on the cut leads to the pot terminals. This way, if you ever want to return to the original wiring, that little bit of left over wire will make it easy to figure out which wire goes to which terminal.

Now, Carter, the reason for modifying just one speaker is to verify that you like the “new” sound. Just hook up both speakers and play a mono source (like FM mono) and compare the sound to see whether you like it before you spend time modifying your other speaker.

Regards,

Jerry

PS: Carter, please let us know how it goes and whether you can hear any difference. Finally, if you hear a difference, how do you like it?

[Guest violin]

Thanks Jerry, I will let you know how it sounds after I get the change made to one speaker as you suggested and have compared the two after some listening.

Thanks for all of your help and directions.

Regards,

Carter

[Carlspeak]

....."What we are talking about in this thread, Carter, is ELIMINATION of the pot from the circuit. Now, the way we do this is we cut both the wiper lead AND the lead at the top of the pot and solder these two together. This takes the 16 ohm resistance totally out of the circuit and increases the tweeter output by approx 1.25db.

...."

Jerry:

Are you saying that taking a maximum 16 ohms of series resistance out of the circuit to the tweeter will reduce the tweeter's output only 1.23 dB? That sounds rather low. As you say, that change is barely perceptable to human hearing. Then why would AR's designers bother with the pots at all if that's all they were going to get?

Typically, series resistors of only 1-4 ohm range of values ahead of a tweeter will attenuate it approximately 2-4 dB.

Am I missing anything?

I did some close miked tests of an AR3a 3/4 inch dome tweeter over a range of frequencies from 5 kHz to 16 kHz and typically got a range from zero to about 30-45 dB attenuation when stroking the pot from min to max.

It's all about the music

Carl

Carl's Custom Loudspeakers

[onplane]

>Jerry:

>Are you saying that taking a maximum 16 ohms of series

>resistance out of the circuit to the tweeter will reduce the

>tweeter's output only 1.23 dB? That sounds rather low. As you

>say, that change is barely perceptable to human hearing. Then

>why would AR's designers bother with the pots at all if that's

>all they were going to get?

>Typically, series resistors of only 1-4 ohm range of values

>ahead of a tweeter will attenuate it approximately 2-4 dB.

>Am I missing anything?

>I did some close miked tests of an AR3a 3/4 inch dome tweeter

>over a range of frequencies from 5 kHz to 16 kHz and typically

>got a range from zero to about 30-45 dB attenuation when

>stroking the pot from min to max.

>

>

>It's all about the music

>

>Carl

>Carl's Custom Loudspeakers

Hi, Carl and a Happy New Year to you!

Carl, I think you misunderstood my comments about eliminating the tweeter pot. First off, if we eliminate the “parallel” 16 ohms resistance of the tweeter pot:

1. Removing the pot INCREASES the impedance for the tweeter network

2. Higher impedance means LESS current flows through the tweeter network @ same voltage

3. Nevertheless, MORE current flows through the tweeter

4. On average 11% more current flows through the tweeter with the pot removed

5. Approx. 25% more power in the tweeter and 25% more SPL

6. Tweeter network increases in sensitivity for the same applied voltage

7. Reduction in xover frequency is really negligible (less than 2% difference between 4000 and 5000 hz)

See:

http://www.classicspeakerpages.net/dc/dcbo...id=11184&page=2

So, removing the pot INCREASES the tweeter output (with the same applied voltage) and it raises the tweeter network’s impedance (a good thing) closer to 4 ohms.

Now, Carl, here is where we need to be clear. This increase of approx. 1.25db is comparing a 3a with the tweeter pot eliminated against a 3a with the pot set to max increase (the recommended position for a flat response).

Now, when AR sold the original 3a’s the tweeter pot setting at that time was recommend to be near the dot (which is lower than the max setting) and this was due to the emphasis applied by record companies at that time to high frequencies.

Since the advent of digital recording and play back, that high frequency emphasis no longer is done. Leaving the pots at the dot when listening to music on modern playback devices causes the frequency response curve to be depressed in the high frequencies.

Carl, does this help??

Regards,

Jerry

[Carlspeak]

Thanks Jerry.

It's become obvious now that we're comparing apples to oranges here.

I missunderstood your original post and assumed you were comparing 16 ohm resistance (min increase setting) with essentially no resistance (i.e. pot bypassed).

It's all about the music

Carl

Carl's Custom Loudspeakers

[Guest tubesman]

> Tubesman,

>

> Around 1987 or so I was on a trip with the military to Utah.

>Had a day off and me and a couple guys drove into the

>mountains by SLC. Found Heber City. Found Jim Fosgate's little

>storefront. Went in and asked the gentleman in charge if he

>was Jim Fosgate. "Nope, I'm Chuck McShane, and the AR-3

>was my baby." The fellow I was with had AR-LST's at the

>time and I had a pair of AR-5's. Our jaws dropped when we

>realized we were in the presence of greatness.

>

> Your uncle's a nice man and I hope he gets through his

>problems.

Thanks a lot for the kind words. He is a VERY nice man, and I'm so glad you got a chance to meet him. I'll tell him about your note for sure!

Jim McShane

[mluong303]

Hello Jim

When you see your uncle Chuck McShane and talk to him again, would you ask him if the AR-3a speaker design is his or Roy Allison. I just want to verify who is the real designer behind the AR-3a speaker rather than base on AR literature or what I heard! Also if it is possible to pose old pictures of him when he working for AR that would be great.

Please forward our Best Regards to Him.

Thanks for your time and efforts,

Minh Luong

mluong303@aol.com