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Rogerfederer

need help w/ AR5 crossover

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hello classic speaker gurus!

this is my 1st post, though i've been a member for a while. i am taking a look at my AR 5 crossovers to see if they need updating. i did some research and found carl's schematic (attached), another schematic (looked the same), and some pictures.

so i was surprised when i opened up the box and found this: http://albums.phanfare.com/isolated/Dk50KRQL/1/6272416

i expected 3 capacitors: 4uF, 24 uF and 72 uF. instead i only found one object i immediately recognized as a capacitor (i am a novice at this). it is the 4uF cap. so where are the 24 and 72 uF caps? there is a boxlike object with several wires running into it that seems to be sealed with wax? are there capacitors in there?

i bought them from an engineer who said he had restored them but i don't think he remembered the details. maybe i can try to contact them.

anyways, would love any advice!

AR5_schematic.pdf

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The large wax block is indeed 2 capacitors ( 24 and 72 uf) on a single chassis. The wire-wrapped block is providing the resistance as per the original crossover design so all of the parts are there as per Carl's schematic. Not sure how this was ever restored as the parts all appear original (old) but regardless, if you follow Carl's schematic you could update the caps with newer individual caps and maybe replace the wire-wrapped block with an audio grade noninductive resistor for a simple upgrade.

If you follow the AR 3A restoration project on this Web Site youi can do a whole lot more to restore these classic speakers.

Good Luck ! ;)

Dean

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hey that is great. just what i needed to know.

since i only have access to the 4uF cap maybe i should test it with my peak ESR meter and if it measures poorly i could assume the rest of the caps need to be replaced as well.

does that make sense? otherwise i can't really know if the caps in the box are good or not...

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the 4uF cap tested leaky so i have ordered the caps to replace all of them. thanks again for the quick advice!

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if you follow Carl's schematic you could update the caps with newer individual caps and maybe replace the wire-wrapped block with an audio grade noninductive resistor for a simple upgrade.

The resistor value in the schematic is incorrect. It is showing the value for the AR-3a, not the AR-5. It should be 1.5 ohms, not .51.

Roy

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Not sure how this was ever restored as the parts all appear original (old)

Looks to me like he re-foamed the woofer and replaced the pots with L-pads.

Kent

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I don't see the resistors that should be used with the L-pads, not sure if that will cause any issues or not.

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The resistor value in the schematic is incorrect. It is showing the value for the AR-3a, not the AR-5. It should be 1.5 ohms, not .51.

Roy

The schematic the OP posted was a very old version. The one now in the library has a 1.35 ohm resistor. That correction was made quite sometime ago.

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carl,

i found the updated schematic. thanks for the tip. will take a look at the resistors.

doug

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The schematic the OP posted was a very old version. The one now in the library has a 1.35 ohm resistor. That correction was made quite sometime ago.

Not sure where I got the attached schematic but it shows a 1.5 ohm, not 1.35. Of course AR may have changed the parts at some point, and the difference between 1.35 and 1.5 is negligible.

1.5 will be much easier to find. Partsexpress, Madisound and Erseaudio all have 1.5 but not 1.35. Erse has 1.3.

These Mundorfs are nice if you are ordering from Mad http://www.madisoundspeakerstore.com/mundorf-10-watt/mundorf-1.5-ohm-metal-oxide-film-resistors/

If you decide to shop locally just make sure you get at least 7w. Your local Rat Shack may have these, if the salesman knows what a "resistor" is and doesn't try to sell you a cell phone instead: http://www.radioshack.com/product/index.jsp?productId=12580067&filterName=Type&filterValue=10-watt+resistors

Kent

AR-5 schematic (from AR).pdf

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Not sure where I got the attached schematic but it shows a 1.5 ohm, not 1.35. Of course AR may have changed the parts at some point, and the difference between 1.35 and 1.5 is negligible.

1.5 will be much easier to find. Partsexpress, Madisound and Erseaudio all have 1.5 but not 1.35. Erse has 1.3.

These Mundorfs are nice if you are ordering from Mad http://www.madisoundspeakerstore.com/mundorf-10-watt/mundorf-1.5-ohm-metal-oxide-film-resistors/

If you decide to shop locally just make sure you get at least 7w. Your local Rat Shack may have these, if the salesman knows what a "resistor" is and doesn't try to sell you a cell phone instead: http://www.radioshack.com/product/index.jsp?productId=12580067&filterName=Type&filterValue=10-watt+resistors

Kent

Kent,

Your schematic is an original AR document, and is correct. Since Carl and I discussed this awhile back (resulting in his revision), I have seen some late production AR-5's. All were equipped with conventional sandcast 1.5 ohm resistors, matching your schematic.

Frankly, there is no reason to replace the original resistor if it is functioning properly. I have never seen a failed one of these.

Roy

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I don't see the resistors that should be used with the L-pads, not sure if that will cause any issues or not.

Hi John,

The midrange can be a bit too much for some people without the added resistor.

The added output provided by the L-pad, however, usually enhances the old tweeter's response...though it does become easier to blow at high volume levels.

Roy

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Roy,

Thanks for that explanation. I kind of figured it was along those lines but I wanted someone much more knowledgeable like yourself to answer.

Thanks,

John

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hey guys,

thanks for all the helpful advice. i have the new caps in one speaker and am starting on the 2nd. also have the resistors and will try to pop them in, though will require bending my arms in a funny way:)

a new question: i noticed that someone added a resistor across the woofer in each speaker. see the last 2 pictures in this album:

http://albums.phanfare.com/isolated/Dk50KRQL/1/6272416

any idea what the goal of that is? not identified in the schematic. of course, as noted above, the pots have been replaced so that has altered the original scheme...

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OK, one theory... if you look at the 3rd to last photo in the album it identifies the woofer as a replacement. i wondered why it had foam instead of cloth surrounds. perhaps the resistor was added to make the woofer behave like the original cloth surround woofer.

just a guess

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Just FYI--the AR-5 never had a cloth surround woofer. Quite the opposite: When it was introduced in 1968, AR's literature made a big deal out of the fact that the AR-5's new 10" woofer used a newly-developed foam surround. It was touted as a major advancement.

Soon afterwards, all AR 10" woofers had foam surrounds. The "new" 2ax, introduced in 1970, used essentially the identical woofer as the AR-5, as did the LST-2, introduced in 1974.

The AR-8 also used a foam surround, although at the time of its introduction, AR said that the AR-8's woofer was a little different from the 2ax/5, by virtue of the 8's having a lower FAR and supposedly (although unspecified in any documentation that I've ever seen) greater power handling.

In recent times, all Classic-era AR 10" replacement woofers have come to be regarded as "universal" (foam), with one unit being used as a replacement for all original drivers.

But again, the AR-5 was foam all the way.

Steve F.

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OK, one theory... if you look at the 3rd to last photo in the album it identifies the woofer as a replacement. i wondered why it had foam instead of cloth surrounds. perhaps the resistor was added to make the woofer behave like the original cloth surround woofer.

Good guess.

I asked Roy for his thoughts and he wrote; "That AR-5 replacement woofer appears to be a later Tonegen...The resistor is probably intended to tame it a bit. Response characteristics are somewhat different."

So, as Steve said the original had a foam surround, but you are correct that the resistor is there to make the replacement behave more like the original.

Kent

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kent,

thanks to you (and roy) for the info. do you think the resistor was added by AR or maybe someone tinkering w/ these speakers? do you recommend this modification?

i guess i'm wondering if i should take the resistors out, or maybe try to hunt up some original 10" woofers.

best,

doug

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kent,

thanks to you (and roy) for the info. do you think the resistor was added by AR or maybe someone tinkering w/ these speakers? do you recommend this modification?

i guess i'm wondering if i should take the resistors out, or maybe try to hunt up some original 10" woofers.

best,

doug

Doug,

Removing the resistor will not produce a matching response to the original woofer. Assuming it is original, the added resistor is worth a try, though it is still not likely to be an exact match. Original drivers are always the best bet, but you should get a general feel for the 5 as is.

Roy

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Since we have mentioned AR-5 crossover changes in this thread, it should be noted that Carl's schematic and the AR schematic posted by Kent both depict the later AR-5 crossover with the #10 (3.83mh) and #11 (2.3mh) AR coils. Doug's photos show #6 (1.37mh) and #8 (3.00mh) coils used in the early AR-5's.

#10 replaced #8 and #11 replaced #6.

It is not known if the changes reflected a change in the woofer. Inductor values were increased in all AR models of that era.

Roy

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Roy

Thanks for the useful info. I will see how the woofer with the added resistor sounds now that I'm recapping the crossovers.

So the inductors shown suggest an early ar5. I assume that doesn't change the cap or resistor values I should be using.

Well, I'll finish them up and see how they sound! I do have some 2ax with the foam surround woofers so I could swap those in to compare...

Doug

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