Sonic character of replacement AR driver?

[Guest Tube747]

Hello!

I have to refurbish my AR LST and some of the tweeter has been damaged for some reason when bought from the owner several year back.

I saw a company called AB tech selling the replacement for LST. What do you think their mid-range and tweeters units. How it's sound? Someone said the new one is more transparent and clear.

http://www.abtechservices.com/arspeakers.html

Any thoughts?

Thanks!

Regards,

CHAN

[Guest rbrumett]

Hello!

I have to refurbish my AR LST and some of the tweeter has been damaged for some reason when bought from the owner several year back.

I saw a company called AB tech selling the replacement for LST. What do you think their mid-range and tweeters units. How it's sound? Someone said the new one is more transparent and clear.

http://www.abtechservices.com/arspeakers.html

Any thoughts?

Thanks!

Regards,

CHAN

The AR3a restoration guide which can be downloaded from this site has some very useful info on those speakers

[genek]

I have to refurbish my AR LST and some of the tweeter has been damaged for some reason when bought from the owner several year back.

I saw a company called AB tech selling the replacement for LST. What do you think their mid-range and tweeters units. How it's sound? Someone said the new one is more transparent and clear.

The AB service replacement is a ferrofluid cooled tweeter that is a drop-in replacement for the AR-10pi, 11 and later models. These models used different crossover specs, and Ken Kantor has determined that you'll need to mount a .07mH inductor in parallel with it to approximate the 3a/LST tweeter performance with their original crossovers. I have heard some describe these tweeters with the proper crossover mod as an improvement over the original, but how they'd be mixed in with originals in the same box is another matter. I have a pair of original 10pi/11 tweeters in transit to me and will be doing some comparisons when they get here.

[Rich W]

Hello!

I have to refurbish my AR LST and some of the tweeter has been damaged for some reason when bought from the owner several year back.

I saw a company called AB tech selling the replacement for LST. What do you think their mid-range and tweeters units. How it's sound? Someone said the new one is more transparent and clear.

http://www.abtechservices.com/arspeakers.html

Any thoughts?

Thanks!

Regards,

CHAN

Hi Chan,

I can't speak for the AB Tech midrange driver, as I only replaced the tweeters as part of my recent AR-3a restoration (the AR-3a uses the same replacements as the AR-LST). I can say that the AB Tech replacement tweeter, with the addition of .07 mh inductor recommended in the AR-3a restoration manual, sounds superb to my ears. This is borne out by several diffuse-field (approximately 14 feet from the speaker) 1/3 octave pink noise tests I've run. Without any equalization, I measured the frequency response to be +/- 2.5 dB from 500 to 10K. This is outstanding performance, and speaks to the seamless transition from the traditional AR-3a "fried egg" midrange to new AB-Tech tweeter.

Ken Kantor's test comparison with the original AR-3a tweeter reveal that the AB-Tech replacement does not exibit quite as good off-axis performance above 10K, and there has been some criticism leveled against the AB-Tech driver for that reason. I would question how meaningful this difference is in real-world applications, and for the AR-LST, with its multiple drivers on different planes, I would consider it a moot point. From a purely subjective standpoint I can say that the overall sound of my AR-3a are as open, well-disbursed, and "non-speaker like" as I've ever experienced, and far superior to the sound with the original tweeters, which were probably at the end of their useful life due to internal decomposition of foam as noted by Roy C.

Hope this helps.

Best Regards,

Rich W

[RoyC]

Thanks for sharing your experience, Rich. Very few results have been posted regarding this tweeter since we discussed Ken's recommendations.

I have a small quibble or two with the ABT tweeter, but agree that it is a worthy replacement, and the ease of installation certainly makes it an attractive option. I'm also in agreement that the difference in measured dispersion is not a big issue.

I was recently told that none of the ABT "replacement" drivers for the 3a/LST pictured on the ABT website are in stock.

Roy

[genek]

Ken Kantor's test comparison with the original AR-3a tweeter reveal that the AB-Tech replacement does not exibit quite as good off-axis performance above 10K, and there has been some criticism leveled against the AB-Tech driver for that reason. I would question how meaningful this difference is in real-world applications, and for the AR-LST, with its multiple drivers on different planes, I would consider it a moot point. From a purely subjective standpoint I can say that the overall sound of my AR-3a are as open, well-disbursed, and "non-speaker like" as I've ever experienced, and far superior to the sound with the original tweeters, which were probably at the end of their useful life due to internal decomposition of foam as noted by Roy C.

I've been playing with one of those AR-218v 3/4" domes in one of a pair of AR-3a's, and the lesser dispersion shows up mainly as a reduction in the listening position "sweet spot." It's definitely noticeable in a single-tweeter system, but I also suspect that on a multi-driver system like an LST it would be less of an issue. On-axis sound is perfectly fine, even next to an original tweeter in the other speaker. I wouldn't describe the sound as "superior" to that of the original, but that may be because the inductor being used was selected with the intention of duplicating the response of the original as much as possible.

[RoyC]

I've been playing with one of those AR-218v 3/4" domes in one of a pair of AR-3a's, and the lesser dispersion shows up mainly as a reduction in the listening position "sweet spot." It's definitely noticeable in a single-tweeter system, but I also suspect that on a multi-driver system like an LST it would be less of an issue. On-axis sound is perfectly fine, even next to an original tweeter in the other speaker. I wouldn't describe the sound as "superior" to that of the original, but that may be because the inductor being used was selected with the intention of duplicating the response of the original as much as possible.

Among the tweeters we sent to Ken Kantor were a couple of AR303 tweeters. That tweeter is very similar to the AR-218v mentioned above. In reference to it being an AR-3a replacement tweeter, he stated in his notes that "The AR303 tweeter is least suitable". "Its dispersion is limited..." He went on to suggest that it would require more crossover modifications to approach the "target response of the AR-3a". The AB Tech tweeter tested better than the AR303 tweeter in most respects pertaining to its use in the AR-3a. As we know, Ken concluded that the AB Tech tweeter "works well with the AR-3a with the addition of a single .07mh shunt inductor". He also found response irregularities among the original tweeters we sent to him, with one of mine biting the dust in the process.

With Ken's findings and the high cost of the increasingly hard to find AB Tech tweeter in mind, I have experimented with several other dome tweeters (a pair of which Ken kindly sent me as a replacement for my deceased 3a tweeter) in the 3a and 2ax, and have come to believe there are probably any number of modern dome tweeters that would work satisfactorily with a shunt inductor and a cabinet hole adapter. Under typical use in a *pair* of speakers, I have NOT found dispersion to be a problem of significance with domes that are not highly recessed in their face plates. Obviously these are subjective comments that are influenced by listening environment and listening preferences.

I have also experimented with a planar tweeter in the 3a, and it sounded surprisingly good on axis, but dispersion irregularities ARE a problem with planars.

Roy

[Carlspeak]

I've had success with Scanspeak 3/4 inch tweeters and Fountek NeoCD3.0 True Ribbon Tweeters. Ribbons characteristically have good off-axis response. However, in all cases with the 3a it's the recessed baffle and close proximity of the tweeter's location to the corner, there are inherent diffraction issues AR eventually addressed to some extent with the 3a "improved" model.

[soundminded]

Hello!

I have to refurbish my AR LST and some of the tweeter has been damaged for some reason when bought from the owner several year back.

I saw a company called AB tech selling the replacement for LST. What do you think their mid-range and tweeters units. How it's sound? Someone said the new one is more transparent and clear.

http://www.abtechservices.com/arspeakers.html

Any thoughts?

Thanks!

Regards,

CHAN

In direct A/B comparison the results will be different. Depending on the deviation of the electrical parameters L and R of the replacement and their sensitivity, the loudness and crossover frequencies will not match the original but I cannot say to what degree.

Also of signifigance is the difference in the geometry of the dome and a recess directly around it if there is one. This will result in a different dispersion pattern. As Tom Tyson reported, the AR3a tweeter used in LST is down only 5 db at 15 khz 60 degrees off axis. Most other tweeters are down at least 10 db and don't even indicate curves at this angle in their published literature. A 5 db falloff means that only 32% of the on axis output is radiated at that angle at that frequency. But the side tweeters are only 45 degrees angled compared to the center tweeters so the difference may be closer to 50% or 3db. This is a very good match suggesting that hi frequency response will be very uniform throughout the listening area in the front hemisphere of the speaker using the original tweeters. But tweeters with slightly recessed domes and/or having a larger diameter will not achieve this goal, the high frequency output relative to the midrange and woofer falling from 0 to 22.5 degrees and then rising again as you approach the axis of the side tweeters. A 10 db falloff means only one tenth as much output.

Also of importance are the early reflections of high frequencies off the side walls, floor, and ceiling which will be less at the highest frequencies for the replacement tweeters. How much effect his has will depend on speaker placement and room acousitcs. Both Floyd Toole and Leo Beranek have determined that early lateral reflections add to the enjoyment of music, Toole as it relates to loudspeakers in listening rooms, Beranek as it relates to concert halls. Unfortunately, the current speaker design philosophy emphasizes restricted off axis reflections to minimize room interactions. That is why there are no tweeters of comparable dispersion to AR3a's or AR LST's manufactured anymore.

[genek]

With Ken's findings and the high cost of the increasingly hard to find AB Tech tweeter in mind, I have experimented with several other dome tweeters (a pair of which Ken kindly sent me as a replacement for my deceased 3a tweeter) in the 3a and 2ax, and have come to believe there are probably any number of modern dome tweeters that would work satisfactorily with a shunt inductor and a cabinet hole adapter. Under typical use in a *pair* of speakers, I have NOT found dispersion to be a problem of significance with domes that are not highly recessed in their face plates. Obviously these are subjective comments that are influenced by listening environment and listening preferences.

In direct A/B comparison the results will be different. Depending on the deviation of the electrical parameters L and R of the replacement and their sensitivity, the loudness and crossover frequencies will not match the original but I cannot say to what degree.

This past week I did some swapout trials with a 200011-1 tweeter (AR-10pi/11). I mounted the tweeter alone and with the .07mH Ken Kantor mod in one of a pair of 3a's. Although I could hear slight differences between both configurations and the stock 4600-1 tweeter in the other speaker of the pair, I can't honestly say I would call any of them "harsh," as the AB tweeter in 3a without crossover mod has been described, or any other particularly negative connotation; they were just different, and in both cases I could achieve what sounded to my subjective hearing test like a "close enough" match for the 4600-1 treble balance by tweaking the tweeter level control. This exercise, combined with my tinkering with the AR-218v tweeter, leads me to conclude the following:

1) There really isn't all that much sound up in the tweeter range; most of what we describe as "highs" is really coming from the mid driver and what comes out of the tweeter is mostly what we sometimes describe as "airiness."

2) Hearing is very adaptable and has a short memory (at least mine does), and given some adjustment time, non-original drivers will probably not be much of an issue as long as the completed system isn't mixing original and non-original drivers (iow, if you decide on a non-original replacement, change them all out), at least as far as on-axis sound is concerned (though I do find the shrunken listening "sweetspot" to be an irritation I'd rather live without if I can).

3) The good news is, the 10pi/11 dome tweeter seems to have dispersion similar to the 3a's. You'll just have to tinker with inductors a bit to see what sounds best to you.

My next experiment (probably not for a few weeks) is going to be to take an old -2 AR-5/2ax tweeter and try mounting a 5 ohm resister in parallel to see what happens when you drop its nominal 5 ohm DCR down to 2.5 ohms.