AR 14 tweeter

[Sonnar]

Hello, I have a question. The AR 14 tweeter is the same mounted in the AR 48S? In the AR 14 x-over frequency is at 1.3 KHz , very low.

[ra.ra]

This information all comes from the Library. There is a drawing for 1" High Range Assembly (Jul 77) which denotes its use as the tweeter in two-way models AR-14 and AR-15 - - both the drawing and part number are 200024. ADD product literature shows the x-o freq. as 1700 Hz for the AR-15 (smaller woofer and cabinet).

Subsequent drawing number 100046, AR-48s Final Assembly (May 81), shows the same 200024 tweeter being used for this three-way model, and its product literature notes the mid-to-tweet x-o freq. as 2500 Hz.

[Jeff_C]

Here is a link to an old thread about the AR-14

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=816

[Sonnar]

Thank You, , I have a nice pair of AR 2, an excellent woofer but the double cones tweeter is awful and has a lot of limits in high frequencies. The x-over frequency is at 2 KHz, but I believe the upper limits of the 10" woofer is about 1.3 / 1.4 KHz, so I need a good tweeter to replace the double cones combo.

[aquila2010]

On ‎9‎/‎1‎/‎2015 at 8:57 AM, Sonnar said:

Thank You, , I have a nice pair of AR 2, an excellent woofer but the double cones tweeter is awful and has a lot of limits in high frequencies. The x-over frequency is at 2 KHz, but I believe the upper limits of the 10" woofer is about 1.3 / 1.4 KHz, so I need a good tweeter to replace the double cones combo.

Imho, you'd better to try to keep AR double cones midranges/tweeter and use a pair of AR 2a tweeters (to upgrade the AR 2 to AR 2a) or a pair of Electrostat-3 as reported in http://www.audiokarma.org/forums/showthread.php?t=480259.

If you think to use a pair of AR 14 tweeters (produced in a different time), imho, you'd better to use a pair of up to date tweeters such as inexpensive HiVi tweeters or, if you want, more expensive dynamic or electrostatic/isodynamic modern tweeters.

 

[JKent]

Imho, you'd better to try to keep AR double cones midranges/tweeter and use a pair of AR 2a tweeters (to upgrade the AR 2 to AR 2a) or a pair of Electrostat-3 as reported in http://www.audiokarm...d.php?t=480259.

...or the easier-to-find MicroStatics. I have a spare pair but shipping to Rome could be pricey.

Here are some threads:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=8325

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=3251&hl=microstatic#entry68788

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=3254&hl=microstatic

I have a pair of AR-2a's that I'm not using right now but IIRC I really liked the sound. They're essentially an AR-2 with the addition of a supertweeter so adding the Electrostat-3, JansZen 1-30, MicroStatic or or other supertweeter array may do the trick.

-Kent

[Sonnar]

The real problem is on the frequency crossover , 2 Khz is too high . With B&K measuring signals pinl noise test, it' s obvious that AR 2 's woofer has its upper limit at 1.4 Khz. I Wouldn 't switch my AR 2 into a three-way loudspeaker, just finding a good tweeter able to go low down to 1.3 / 1.4 Khz, to realize a classic two-way bookshelf like AR 14, 38s, or Advent Loudspeaker or KLH Six.

[ra.ra]

Not quite sure what the objective of this project is here, but if you are dissatisfied with the original dual tweeters of the AR-2, why not simply replace them with the 3-1/2" driver (the one w/fiberglass damping and wire mesh) and convert them to AR-2x speakers. This driver served as the tweeter in the AR-4 and the mid in the AR-2ax, and AR even made a simple conversion kit for this exact purpose. Since you do have the AR-2 model, that means you have the early 10" cloth woofer, and I believe all models using this woofer had the same x-o frequency at 2000 Hz.

These tweeters are often available and very affordable, and the 6uF cap used in the circuit could not be simpler. What is unclear is why you think this woofer tops out at 1300 or 1400 Hz if AR designed several models using this woofer which all had x-o points at 2000 Hz? Are you stating that you have measured these speakers and are finding a frequency gap between 1300 and 2000 Hz that is not covered by the original drivers?

[Sonnar]

Yes I have the early AR 2 with 10" woofer cloth surrounds. I use B&K pink noise frequency test disc and an oscilloscope , capturing output signals with a Sennheiser MD 421 . It's a home- made reliable way to show the behaviour of speakers in your listening room . My AR 2 are positioned on the wall, four feet away from corners, two feet from the ceiling , and I 've measured a linear response from 500 Hz up to 1.4 Khz, then a large hole until 2.5 Khz. In my opinion, maybe 2 Khz is a too high x-over point for a 10" woofer, while is probably ideal for 8" woofer like in AR 6 . In fact, the AR 14's 10" woofer is crossed at 1.3 Khz.

[Jeff_C]

I would trust AR's engineering to have produced speakers with a decent flat FR, when new, and operating fully in spec, even if the design pushed the boundaries relating to distortion nearing the crossover frequencies.

AR engineers cannot have foreseen what would happen in all rooms however. Generally though I would have thought that room and speaker positioning may account for what happens up to between 300Hz to 500Hz and then the speaker should take over. So have you considered that the woofer(s) are out of spec?

[Sonnar]

Yes, early 10" woofer have Alnico magnet, and they are 57 years old. But also my two pairs of AR 3 have Alnico magnet and are very aged . However , I can't detect any failure in their sound or measurements. In the Library there is an AR 2's frequency response graphic that shows some problems of linearity above 1.4 Khz , and it seems to confirm my theory.

[genek]

The frequency response of classic ARs is almost entirely derived from the responses of the individual drivers. The crossovers are there mostly for tone shaping (and, of course, to cut off low frequencies that might damage mid and high drivers).. So the designers probably let the 1.4kHz end of the "hole" you measure in your 10" woofer be the beginning of woofer rolloff, put the crossover at 2kHz to suppress the rise of other end of the "hole" at 2.5kHz and then used tweeters with a response that complemented the woofer in the 1.4kHz-2kHz range.

If your measurements are showing both ends of the "hole," my guess is that your crossover isn't rolling off the highs over 2kHz anymore. Could be you need to recap.

If you want to replace the original tweeter with something different, you'll need to revise the crossover to suit the tweeter's response.

[Sonnar]

I use to recap every vintage speaker immediately, using Jantzen paper/oil for AR 2 and AR 3, or Mundorf electrolytics for AR 3a and Altec Valencias. I left only original inductance. AR 2 crossover has x-over components on the negative pole , and I left it this way. I 'm tryin' some tweeters , and I have a good sound with an italian 1" silk soft dome crossed with a 11.5 cap and a 4.7 ohm resistor in series and 6.8 ohm in parallel. Seas , Scan-Speak and Audax are also excellent tweeters, but a little " bright " and cold , while the italian soft dome has a " sweet " and musical sound , probably dued to the memory of the great success of AR speakers in Italy .

[Sonnar]

Here are two pics of my AR 2 with the mentioned 1" soft dome.

[genek]

Do your measurements correspond to the AR-2 curve in the brochure in the library? While there is a dip you can see on the chart, the response is still within +/- 3dB of zero. Are you measuring a bigger "hole" than that? If so, I'm thinking that perhaps the tweeters you're trying roll off too much in that 1.4kHz range.

[Sonnar]

You ' re probably right. With original double cones combo I measured a response very similar to the response shows in the graphic , but the sound is a little " dull " compared to AR 3 . With 1" soft dome tweeter the sound is more complete but it shows a wider dip over 1.4 Khz. That's the reason for I asked the AR 14 tweeters , I 've found a pair of it on ebay and AR crossed it at 1.3 Khz . Unfortunately, I 'm not able to found an AR 14 x-over schematic.

[genek]

There's an AR-14 crossover drawing in the Drawings section of the library. It's an assembly drawing rather than a schematic, but it will tell you what the capacitor values are.

[ra.ra]

Or you can find the drawing in either of these threads. Looks like maybe a 20uF cap on the tweeter in the AR-14.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=6660

http://www.audiokarma.org/forums/showthread.php?t=425874

[Sonnar]

Thank You! Interesting crossover design, it seems an 18 db/oct. , probably to protect tweeter because the low frequency crossover point. I listened AR 14 many years ago, probably in late seventies, and I remember an equilibrate sound, very smooth, perhaps better than New Advent Loudspeaker I had at the time: but Advents had deeper bass response.