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guidance in restoring AR-1's


shadetreehifi

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I'm going to go ahead and ask this: please tell me if this is not the place. I've got a pair of Realisitic Mach Ones which use the sh-15 tweeter. It's nominally 7 ohms. Could I stack this HF driver atop the AR1 with a suitable capacitor wired in series (wiring the HF driver in parallel with the AR1s)? Again, I've never built speakers before, so I don't know whether I'm opening a can of worms by asking, but I thought since I've got these HF drivers not in service at the moment, maybe I could put them to use.

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One question I have is this: if I were to lower the resistance of the pots in the AR1's, could I up the relative volume on the Altecs?

The original pots would not result in more output from the Altecs. The 25 ohm pots actually result in more output at each setting, as well as more overlap with the woofer.

Roy

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Today I took the tweeters and L-pads out of the mach ones and wired them up with a high pass filter at about 8500 hz on top of the AR1 cabinets. While these tweeters probably aren't the best match for the AR1s (a little too agressive), I was surprised at what a little bit of high frequency can do to fill out the soundstage. To hear the tweeters by themselves I can barely tell they are playing, yet their contribution to the mix is audible.

Now I'm thinking of building a tweeter array in the manner of the microstatics or the 3st to go with the AR1s. For now I'll just keep my ears open and see what comes along. Parts Express has some phenolic ring tweeters which according to their customer reviews have done well at replacing AR4x tweeters...

Thanks for the great information and knowledge base while these drivers were coming together. Now on to the cabinets!

Here are a couple of pictures (bad lighting) of the decidedly shadetree rig I've got going right now. Elegant it is not, but it sounds good with my eyes closed. When I find some tweeters whose character matches the AR1 I'll build a suitable cabinet for them.

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Although the Microstatic add-ons look superficially similar to the Janszens, they are a totally different design concept. They were not designed to replace tweeters that are lacking in HF response or to extend their high end, but to widen the effective dispersion of the existing tweeter. I have several of them, and none of them make the speakers they are paired with produce more HF output, but they make the sound even more "airy" than they already are (which is quite a lot already). The effect is sort of like they're converting the box and its single tweeter into a sort of poor man's LST.

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For sure, the Microstatic will make an AR-3a sound more "airy", because it's designed to broadly disperse high frequencies; but while the AR-3a is already a full-range system, the HF response of the AR-1 plummets above 10kHz, and should benefit from the Microstatic's above-20kHz extension, no?

Shadetree - you could consider an AR-3 or 3a tweeter (or even one from the 9-series) as an add-on.

Has anyone ever heard the AR-1 with the AR-3st tweeter, which was designed to extend the range of the AR-1?

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I think the MS would not do a good job of extending the AR-1, because its two innermost drivers are smaller and produce less output than its two outermost. When paired with a tweeter that already has good on-axis output it expands horizontal dispersion to nearly 180 degrees, but put on a speaker with deficient on-axis HFs, I think it would leave a "hole" in the on-axis output.

Of course, if the OP builds his own array using four identical tweeters, that wouldn't be a problem.

An AR-1 with an AR-3st on it sounds like an AR-3, if you adjust the AR-1 jumper to woofer-only configuration. With the Altec in the mix, I expect it would have a pretty big midrange bump.

When I was doing the refurbishment on my ar-3a's, while they had no HF drivers I temporarily ran them in woofer-only with a pair of AR-1ms in parallel and sitting on top of them. Considering that the setup had no way of adjusting the 1ms output in relation to the effective AR-1W I had them on, it sounded pretty good.

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When you consider the fairly large number of mid/hi units that were available in the 50s, and the fact that the AR-1W was sold as an add-on subwoofer for existing speakers pretty much from the beginning, there's probably not any such thing as a "wrong" combination. If you think the sound is a bit too aggressive, try playing with the L-pad some more or use ones with more attenuation instead.

Today I took the tweeters and L-pads out of the mach ones and wired them up with a high pass filter at about 8500 hz on top of the AR1 cabinets. While these tweeters probably aren't the best match for the AR1s (a little too agressive), I was surprised at what a little bit of high frequency can do to fill out the soundstage. To hear the tweeters by themselves I can barely tell they are playing, yet their contribution to the mix is audible.

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When you consider the fairly large number of mid/hi units that were available in the 50s, and the fact that the AR-1W was sold as an add-on subwoofer for existing speakers pretty much from the beginning, there's probably not any such thing as a "wrong" combination. If you think the sound is a bit too aggressive, try playing with the L-pad some more or use ones with more attenuation instead.

That's a good point. I'm going to keep my ears open for an open and relaxed-sounding tweeter. Something along the lines of the AR4x tweeter. I haven't heard the 3a. The horn loading of the mach one tweeters may be responsible for their forward sound. When I take the horns away, the "agressiveness" goes away, but these tweeters are nowhere near as "musical" as the 4x's. They sound blurred in comparison. So that leads me to consider whether a high-dispersion quick-response non-horn-loaded tweeter, like a ribbon waveguide, might be in order.

Does anyone have experience comparing dome tweeters with ribbons in conjunction with vintage speakers? As I understand it, the Janszen 130 is an electrostatic array, and the 3a incorporates a dome-style tweeter, which some listeners augment with microstatic dome arrays. How do these two approaches differ in practice?

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The Microstatics use cone tweeters. The effect is sort of dome-like, but only horizontally.

The debate about horns vs cones goes back pretty much to the beginnings of hi fi. And then the development of domes and other drivers just made it even more complicated.

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I have been experimenting with this tweeter from parts express http://www.parts-express.com/pe/showdetl.cfm?partnumber=277-110&utm_source=google&utm_medium=cpc&utm_campaign=pla in conjunction with the AR-1s.

Right now I have it crossed in at 13k hz at 6db per octave on an 8ohm l-pad at 9:00 position. I rigged up some cardboard baffles that are as wide as the top of the AR-1 cabinets. They sound good to my ears, smooth and airy. However, the upper range of vocals begins to sound artificially sharp when the tweeters are switched on.

I figure this is because of the gentle attenuation slope on my high pass filter which is allowing overlap between the upper frequencies of the Altecs and the below-crossover frequencies of the tweeters, so I'm going to try a third-order high pass at 18db per octave.

My question is: what effect does a third-order filter have on frequency response at and above the crossover point? Ideally, I would like to have minimal overlap between the Altec and the tweeter, just a greater sense of space and air.

I'll post some pics of my getup when I'm around the speakers again.

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I rigged (emphasis on rigged...better more permanent work to follow) a third-order high pass to the Beston ribbon tweeters and am in the process of listening to them. They cut in at 13k hz.

My complaint with the first-order high pass was that there was doubling in the upper midrange and treble frequencies, which clouded the sound of the Altecs.

That problem is completely solved. No more bright tinny edges on vocals, no peaks in the piano range when a performer goes up and down the keys. The Altecs are allowed to do their thing, and it all comes through. What's above them is mostly air and small details, which is all I wanted to add. I can now hear the details of snares and trumpet work that was not apparent before.

This was the cheapest ribbon tweeter I could find anywhere. It came with no spec sheet. Fortunately, for my ears at least, I got lucky.

Pics attached. Yes, that is a malt liquor carton housing the tweeters. Permanent housing to come soon, along with refurbishment of the cabinets on the AR-1. I'm thinking walnut. I like cherry a lot, but walnut seems to go better with various decor. I'm thinking these things will be around through a lot of changes.

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Caveat emptor: I am an english major, and my baseline for any philosophical inquiry is that it result in a net increase in one's quality of life. I was just sitting out on my porch, and realized that my appreciation for varying frequencies of sound, as a result of my attention to different qualities of speaker, has resulted in an enhanced perception of real-world sound, such as the play of crickets against the high-frequency range of automobile and airplane (and the occasional freight train) sound.

I was wondering if any of you have noticed such an increase in real-world awareness, and what you have done with that increase. For myself, I have focused it on my fiction writing, in the form of an increased attention to the way words play against one another.

I have noticed a kind of anti-audiophile strain in various forums I've encountered as a result of my AR-1 restorations (not here), and I wonder how you all, if you have ever experienced it, have rationalized your interest / obsession with aural nuances.

Note: before the porch-sitting moment, I was listening to Paul Horn inside the great pyramids, and also Ravi Shankar, on the AR-1s.

Thanks for any input you may have. I think it is interesting to examine whether a philosophical infatuation (like critical listening, or wine tasting) results in a net gain for quality of life.

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A little off-topic, but I was visiting my girlfriend's place of employment today, which is a local high school, and noticed that it features some very interesting loudspeaker enclosures in the main hallway, a throwback to the original 1950's construction...which I am willing to bet (unless they've been gutted) contain some now-decorative 755a's (the whole school now uses ceiling units of the modern type). I am in the process of talking with the administration to give them a good home. Wish me luck!

Like these:

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Update here with the Franken-AR-1's: I finally got around to replacing the pots with the correct 15 ohm values, and the results are very sweet. As Roy said before, the 25 ohm versions I had in there (previous owner was running 8 ohms in one and 25 in the other for some reason, experimenting I imagine) lowered the crossover point of the Altec drivers just a tad, resulting in a bump in the midrange where they overlapped with the woofer. All my favorite vocalists now sound like they have recovered from a head cold; the vocal range is nicely opened up. I ordered some guitar amp pots from Amazon, and though they are huge (three times the size of the originals) they fit, and are working well. Thanks for your help and knowledge- sharing here. After playing around with the Beston magnetoplanar tweeters, placing them off-center and moving them back from the plane of the other drivers to compensate for their greater speed, the high end now sounds as smooth and coherent as my AR4x's, though a tad more analytic since they go up to 40khz. I have them crossed over at 10khz with a third-order high pass, since the Altecs drop off pretty steeply above 10k. Now I can build proper baffles for them. I'll definitely post when I begin re-veneering the AR-1 cabinets, but with all the other stuff going on right now (dissertation...) I can't say when that will be. Happy listening.

link to the pots here: http://www.amazon.com/Amico-Rheostat-Guitar-Amplifier-Resistor/dp/B008DFXBW8

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So I'm thinking about starting in on the AR-1 cabinets, and wondering about the separate housing within the cabinet in which the Altec 8'' sits: why so little room?

Looking around the web at those who run the 755a full range, they are either running it open-baffle or in a 2-cubic-foot cabinet with a sloped face like the Altec 618 cabinet.

I was thinking I could build new cabinets for these drivers (thus saving the old cabs from modification) in which I might enlarge the enclosure for the 755a while keeping volume for the woofer the same. Anyone have any thoughts about what effects that might have on the behavior of the 755a?

I have no experience with designing cabinets, so even if you wouldn't want to venture a guess as to how this specific driver will react, general rules of thumb about frequency response as it relates to cabinet architecture (or general recommendations for literature to dive into) will all be appreciated.

Thanks.

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