Has anyone looked at the Dayton 2" midrange dome as an AR3a midrange replacement?

[Tetrode]

http://www.parts-exp...tnumber=285-020

It's FR seems suitable and it "looks the part".Price ain't bad either

Any input?

[genek]

This is a nominal 8 ohm driver, not a 4 ohm as required by the 3 series. Is there a 4 ohm version?

[Tetrode]

I guess there would some crossover modification needed.

What's the dcr of the original?

[genek]

Usually somewhere around 2.5 ohms.

[ra.ra]

This topic - - - impedance of individual driver vs. impedance of overall speaker - - - baffles me a bit, too, and it prompts me to ask how this original midrange for the AR-3a (a 4-ohm speaker) differs, or maybe is identical to, the midrange driver of the AR-5 (an 8-ohm speaker)?

This very recent attached link with similar ideas may be of some interest - - - altho' mostly a thread about a Rectilinear speaker, our chatter dribbled over into KLH and then AR territory about the AR-3/AR2ax (early) tweeter.

http://www.classicsp...l=&fromsearch=1

[michiganpat]

typically system impedance is dominated by the woofer, since it takes up the most current....as far as a speaker's system impedance, they typically kinda guestimate based on the bulk of the impedance curve....an AR3 is a "4 ohm" speaker, because for a large range of frequencies it's right around 4 ohm, even though IIRC it dips as low as 2.5

[Tetrode]

Here is another viable option that might drop right in with no cabinet modification.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-857

[JKent]

Again--8 ohms. AND $135 each!

What is the point? If you want to mod the 3a, maybe this thread should go in the Mods section. If you want to restore the 3a, use original mids or the equivalent AR10Pi or AR11 mid (that's what I used).

Carl builds a nice "AR3a Super Mod" using SEAS mids and tweets (and new crossovers) but they are no longer AR3a's. Maybe they're better.

The thing is, you can't just drop in a driver because it "fits." I knew this from being told but I recently built some speakers from scratch. Getting the corrrect balance of drivers, capacitors, resistors, inductors, cabinet size, stuffing is an art AND an advanced science.

So what's up? Are you trying to build a new and improved speaker (fat chance) or trying to restore some 3a's with a bad mid? If the latter, I'd recommend checking ebay or Vintage AR for originals.

Kent

[Tetrode]

I was just curious as I read a lot about tweeter replacements for the Ar3a however there doesn't seem to be a lot of talk about the mids.

[tysontom]

Kent is exactly right: what's the point? Unless you are trying to modify the AR-3a to sound different from the original, stay with approximately the same driver; at least the same diameter. That 3-inch midrange from Tang Band is undoubtedly a good driver, but it is twice the diameter of the original midrange, and the off-axis will suffer by a predictable amount. In short, the replacement driver will give the 3a a "boxier," less spacious sound. Perhaps it will image better, but that's about it.

The AR-3a midrange is a very sturdy driver, and the driver is not likely to suffer damage unless the amplifier is overloaded or unless someone is driving the speaker to hideous output levels. The really nice thing about that driver is that it does not use foam suspension pieces or butyl rubber to coat the gap or that sort of thing. It is a conventional fabric soft-dome driver with a half-roll suspension, and the driver will sound the same forever with just a modicum amount of restraint. Replacement drivers show up on eBay regularly, so new drivers are not hard to source.

--Tom Tyson

[Pete B]

Does anyone know what the motor geometry was on the 3a mid?

Top plate thickness, and voice coil wind length?

How about the 2.83V or 1W sensitivity?

I suppose an anechoic curve with the pots in a known position would

allow the sensitivity to be determined.

Anyone have a damaged one for analysis?

I measured the midrange out of an AR-11 which should be the same

but I can't seem to find the post using the search function here.

[Tetrode]

Kent is exactly right: what's the point? Unless you are trying to modify the AR-3a to sound different from the original, stay with approximately the same driver; at least the same diameter. That 3-inch midrange from Tang Band is undoubtedly a good driver, but it is twice the diameter of the original midrange, and the off-axis will suffer by a predictable amount. In short, the replacement driver will give the 3a a "boxier," less spacious sound. Perhaps it will image better, but that's about it.

The AR-3a midrange is a very sturdy driver, and the driver is not likely to suffer damage unless the amplifier is overloaded or unless someone is driving the speaker to hideous output levels. The really nice thing about that driver is that it does not use foam suspension pieces or butyl rubber to coat the gap or that sort of thing. It is a conventional fabric soft-dome driver with a half-roll suspension, and the driver will sound the same forever with just a modicum amount of restraint. Replacement drivers show up on eBay regularly, so new drivers are not hard to source.

--Tom Tyson

Just curiousity more than anything Tom.

It is indication of how tough the driver is by the lack of post here seeking an aftermarket replacement.

[tysontom]

Attached are some of the AR 1.5 midrange (PN 1200010-1) physical characteristics and parameters. I have the top-plate dimensions and voice-coil height dimensions (but not the number of turns or wire size to my knowledge). I believe the voice coil is underhung by about 1-2 mm, but I will confirm the dimensions.

--Tom Tyson

AR_1.5-Inch-Dome-Midrange_PN1200010-1_980aeo-002.pdf

AR_1.5-Inch-Dome-Midrange_PN1200010-1_980aeo-003.pdf

[genek]

FYI, we've defined an admittedly fine line between repair/restoration, which is for the main forums, and upgrades, which go to mods and tweaks. If the object of a discussion is to find an alternative for an unobtanium part that can be used to restore original function and sound it stays here, if it's to "hot rod" a speaker and update its sound to modern preferences, it gets moved.

The grey area is add-ons, like the old Microstatics or their modern equivalents. As long as the original speaker isn't being changed internally, it'll probably stay here.

[Pete B]

Thanks very much Tom, exactly what I was looking for.

Seems to me the best thing to do would be to measure the AB tech mids

and try to determine how close they are for an AR-3a fit or if they can

be modified to work better in the 3a application. I believe that they're

built to the AR-9 spec rather than the 3a?

[tysontom]

Pete,

Here is some more data on the 1.5-inch midrange driver. This is one I've had for several years; it had a rubbing voice coil, I believe, so I dissected it. You can see the top-plate height and the voice-coil height to get an idea of the construction of the unit. This was an old midrange without Ferrofluid; the latter came in around 1977 or 1978 for the midrange, at the earliest. The bobbin is aluminum and the coil is copper.

--Tom

[RoyC]

The AR midrange situation is different than the AR tweeter isssue. The 1.5 inch mid is not suffering from the degradation and scarcity issues the tweeters are. This driver experienced relatively minor changes from the late 60's right through the Tonegen version used in the AR-3a Limited (as well as a replacement midrange) in the 90's. Any of these mids from any era is the best bet as a simple drop-in replacment for a repair or restoration project.

A word of caution...

There are folks like Pete who have the expertise to adapt an aftermarket driver using appropriate crossover changes. Anyone, however, who believes he is going to go to Parts Express and find a driver to "drop in" the cabinet which will meet the original system specs, much less "improve" anything, without making the appropriate design changes, is wasting money and effort. Even the expensive AB Tech replacement mid is not a match to the original.

Roy