Pete B Posted August 21, 2006 Report Share Posted August 21, 2006 Measured a 6 bolt ALNICO woofer in an AR-2x system, through the crossover:Fc = 53 HzQtc = 1.1Qm going from memory, lost the data, was about 4.Thats a high Qtc, well beyond maximally flat, there will be some peaking at and above Fc.Pete B. Link to comment Share on other sites More sharing options...
soundminded Posted August 21, 2006 Report Share Posted August 21, 2006 I've been experimenting with a pair of AR2as which use this woofer and I am astonished at how well they performs. Does anyone have any comparisons with the 4 bolt AR2ax square magnet stamped sheet metal frame version? I've got a pair of those to refoam and AR2axs to restore as well. Looks like an entirely different animal...except for the crossover networks...which do however use both pots as voltage dividers. In AR2a, the midrange pot is used as a series resistor only (both units.) Even the woofer paper formulation seems different. My AR2a woofers have a felt ring glued to the cone. Could they have been made that way or are they likely applied after by the owner? Link to comment Share on other sites More sharing options...
Carlspeak Posted August 21, 2006 Report Share Posted August 21, 2006 >I've been experimenting with a pair of AR2as which use this>woofer and I am astonished at how well they performs. Does>anyone have any comparisons with the 4 bolt AR2ax square>magnet stamped sheet metal frame version? I've got a pair of>those to refoam and AR2axs to restore as well. Looks like an>entirely different animal...except for the crossover>networks...which do however use both pots as voltage dividers.> In AR2a, the midrange pot is used as a series resistor only>(both units.) Even the woofer paper formulation seems>different. My AR2a woofers have a felt ring glued to the>cone. Could they have been made that way or are they likely>applied after by the owner? My 6 bolt AR2a woofers have the same felt ring and are date stamped Dec. 1967. They have the cloth surrounds and wire terminals located on opposite sides of the magnet.I tested them with a Woofer tester and got the following:Fs = 27 hzQes = .82Qms = 1.47Qts = .53 Le = .52 mhVas = 7.7 cu. ft.Mms = 25 gmsSens. = 89 dBAnybody interested in purchasing them?Pete:A Qtc of 1.1 raises a slight peak but may not be necessarily a bad thing. Theory says the peak is about 1.8 dB above flat. Perhaps that's what AR was looking for - that little bit of extra bass?Remember, it's all about the musicCarlCarl's Custom Loudspeakers Link to comment Share on other sites More sharing options...
Guest Rod H. Posted August 21, 2006 Report Share Posted August 21, 2006 The woofers in my newly acquired barn sale AR-2axs have that same felt ring also.BTW, I determined all the drivers work. Yesterday I went inside one and bypassed the potentiometers, then sealed it back up and played it in the shop for a while. The woofers were very easy to remove with a paint can opener, and the stock sealant putty was pliable enough that I was able to easily form it into a rope again and reuse it.Later this week I'm doing the same to the other one. I'll also need to seal the cloth surrounds, as you can see light through them. I'm torn between three things to use for this...all that I have on hand...water thinned Aleen's tacky glue, water thinned siliconized caulk, or alcohol thinned non hardening gasket sealer. Any comments on preferences/experiences appreciated of course. I'll then will bring them into the house and have a serious listen. At this point it sounds like the cone mid/tweeter may be a little hot wide open like this, but my shop is pretty reflective and things may be fine in the house. Rod Link to comment Share on other sites More sharing options...
tysontom Posted August 21, 2006 Report Share Posted August 21, 2006 >I've been experimenting with a pair of AR2as which use this>woofer and I am astonished at how well they performs. Does>anyone have any comparisons with the 4 bolt AR2ax square>magnet stamped sheet metal frame version? I've got a pair of>those to refoam and AR2axs to restore as well. Looks like an>entirely different animal...except for the crossover>networks...which do however use both pots as voltage dividers.> In AR2a, the midrange pot is used as a series resistor only>(both units.) Even the woofer paper formulation seems>different. My AR2a woofers have a felt ring glued to the>cone. Could they have been made that way or are they likely>applied after by the owner? The performance of the 6-bolt vs. the 4-bolt woofers is close; both have the same resonance frequency (57 Hz) and so forth. The newer woofer used an improved felted-paper cone with improved damping over the earlier cone, which used the foam damping rings. The new cone is therefore somewhat smoother in the upper range, particularly the "soft" cone that so many people assume has become rotten. The newer woofer also used a slightly larger voice coil for better power-handling; but all other things remained pretty much the same. The bass harmonic distortion in both versions was very low, the hallmark of that design. At 10 watts input (fairly loud at that continuous-input level), the harmonic distortion at 40 Hz was approximately 3% or less for each version, excellent performance by any standard -- back then or by current standards.--Tom Tyson Link to comment Share on other sites More sharing options...
tysontom Posted August 21, 2006 Report Share Posted August 21, 2006 >A Qtc of 1.1 raises a slight peak but may not be necessarily a>bad thing. Theory says the peak is about 1.8 dB above flat.>Perhaps that's what AR was looking for - that little bit of>extra bass?>Carl, I believe you are correct regarding the slight peak at resonance in the AR-2 series: it was certainly *not* considered a bad thing. That Q alignment was chosen to keep the output strong down to resonance, but the Q was not so high as to cause ringing. *Consumer Reports* and other testing orgainzations regarded the AR-2's bass response as superior to other speakers in its class. I believe I read somewhere that the AR-2 had better bass extension and lower harmonic distortion than any other speaker at the time (early 60s) except the AR-1/AR-3 series.--Tom Tyson Link to comment Share on other sites More sharing options...
soundminded Posted August 21, 2006 Report Share Posted August 21, 2006 The AR2a woofer can be driven very hard without audible distortion or breakup. I'm using a Pioneer SX950 receiver rated at 85wpc and a pair are producing excellent bass in my very large open basement sitting right next to a cement wall approximately 2' off the floor. I've put a 10 mfd capacitor across each woofer voice coil. I'm operating them with the midrange pot all the way down (only reduces the high end of the midrange driver, not its volume) and the tweeter pot all the way up. I've settled on three 1/2" polys per channel, one firing directly forward in series with a 12 ohm resistor and about a 2.2 mfd cap and the other two firing straight up with each having about a 2.7 mfd in series. IMO the results are excellent, very accurate and comparable to any of today's better speakers. Very, clean and open a wonderful surprise. Link to comment Share on other sites More sharing options...
Carlspeak Posted August 21, 2006 Report Share Posted August 21, 2006 >The woofers in my newly acquired barn sale AR-2axs have that>same felt ring also.>>BTW, I determined all the drivers work. Yesterday I went>inside one and bypassed the potentiometers, Why? Didn't they work? Can they be cleaned or replaced? then sealed it>back up and played it in the shop for a while. The woofers>were very easy to remove with a paint can opener, and the>stock sealant putty was pliable enough that I was able to>easily form it into a rope again and reuse it.>>Later this week I'm doing the same to the other one. I'll also>need to seal the cloth surrounds, as you can see light through>them. I'm torn between three things to use for this...all>that I have on hand...water thinned Aleen's tacky glue, water>thinned siliconized caulk, or alcohol thinned non hardening>gasket sealer. Any comments on preferences/experiences>appreciated of course. I suggest a refoam job. Coating problematic surrounds with the likes of which you described above is a hit or miss situation. How much do you put on without affecting the woofer's compliance? How evenly can it be applied? Etc.etc......>>I'll then will bring them into the house and have a serious>listen. At this point it sounds like the cone mid/tweeter may>be a little hot wide open like this, but my shop is pretty>reflective and things may be fine in the house. >>RodRemember, it's all about the musicCarlCarl's Custom Loudspeakers Link to comment Share on other sites More sharing options...
Pete B Posted August 22, 2006 Author Report Share Posted August 22, 2006 >>I've been experimenting with a pair of AR2as which use>this>>woofer and I am astonished at how well they performs. >Does>>anyone have any comparisons with the 4 bolt AR2ax square>>magnet stamped sheet metal frame version? I've got a pair>of>>those to refoam and AR2axs to restore as well. Looks like>an>>entirely different animal...except for the crossover>>networks...which do however use both pots as voltage>dividers.>> In AR2a, the midrange pot is used as a series resistor>only>>(both units.) Even the woofer paper formulation seems>>different. My AR2a woofers have a felt ring glued to the>>cone. Could they have been made that way or are they>likely>>applied after by the owner? >>My 6 bolt AR2a woofers have the same felt ring and are date>stamped Dec. 1967. They have the cloth surrounds and wire>terminals located on opposite sides of the magnet.>I tested them with a Woofer tester and got the following:>Fs = 27 hz>Qes = .82>Qms = 1.47>Qts = .53 >Le = .52 mh>Vas = 7.7 cu. ft.>Mms = 25 gms>Sens. = 89 dB>>Anybody interested in purchasing them?>>Pete:>A Qtc of 1.1 raises a slight peak but may not be necessarily a>bad thing. Theory says the peak is about 1.8 dB above flat.>Perhaps that's what AR was looking for - that little bit of>extra bass?>>>Remember, it's all about the music>>Carl>Carl's Custom LoudspeakersYes, well the Q is higher than I might go, but it's not such a bad thing. The mild broad peak above Fc helps with baffle step loss and a Q of one crosses 0 dB at Fc rather than being attenuated as compared to say a maximally flat system that would be -3 dB at Fc, it will have much more 50 Hz bass output.The steeper rolloff in the transition region helps to reject LF material that might cause over excursion.Pete B. Link to comment Share on other sites More sharing options...
Pete B Posted August 22, 2006 Author Report Share Posted August 22, 2006 >Measured a 6 bolt ALNICO woofer in an AR-2x system, through>the crossover:>Fc = 53 Hz>Qtc = 1.1>Qm going from memory, lost the data, was about 4.>>Thats a high Qtc, well beyond maximally flat, there will be>some peaking at and above Fc.>>Pete B.The AR48s is also a 10" acoustic suspension system. The literature states: System Low Frequency Performance- -3 dB at 45Hz with an effective Q at resonance of 1.15. Looks as if they've not changed the design spec based on Qtc.I measured one AR-2ax at the link below, and at least this sample had a higher in system Qtc of 1.79:http://www.classicspeakerpages.net/dc/dcbo...ing_type=searchPete B. Link to comment Share on other sites More sharing options...
kkantor Posted August 22, 2006 Report Share Posted August 22, 2006 Pete, You mentioned that you were measuring through the xover. What procedure did you use to determine Qts? Link to comment Share on other sites More sharing options...
Guest Rod H. Posted August 22, 2006 Report Share Posted August 22, 2006 >Why? Didn't they work? No, not at all.>Can they be cleaned or replaced? The one I disassembled looked in good enough condition to clean.>I suggest a refoam job. Coating problematic surrounds with the>likes of which you described above is a hit or miss situation.>How much do you put on without affecting the woofer's>compliance? How evenly can it be applied? Etc.etc......You really think I should replace the cloth surrounds with foam?Rod Link to comment Share on other sites More sharing options...
Carlspeak Posted August 22, 2006 Report Share Posted August 22, 2006 >The woofers in my newly acquired barn sale AR-2axs have that>same felt ring also.>>BTW, I determined all the drivers work. Yesterday I went>inside one and bypassed the potentiometers, then sealed it>back up and played it in the shop for a while. The woofers>were very easy to remove with a paint can opener, and the>stock sealant putty was pliable enough that I was able to>easily form it into a rope again and reuse it.>>Later this week I'm doing the same to the other one. I'll also>need to seal the cloth surrounds, as you can see light through>them. My Alnico woofer cloth surrounds also pass light. I checked the porosity by trying to breath air thru the surround and determined there is little or none. That's all that's important regarding maintaining a good AS seal. I suggest you check yours before trying to seal them so light doesn't pass thru. I'm torn between three things to use for this...all>that I have on hand...water thinned Aleen's tacky glue, water>thinned siliconized caulk, or alcohol thinned non hardening>gasket sealer. Any comments on preferences/experiences>appreciated of course. >>I'll then will bring them into the house and have a serious>listen. At this point it sounds like the cone mid/tweeter may>be a little hot wide open like this, but my shop is pretty>reflective and things may be fine in the house. >>RodRemember, it's all about the musicCarlCarl's Custom Loudspeakers Link to comment Share on other sites More sharing options...
Guest Rod H. Posted August 22, 2006 Report Share Posted August 22, 2006 >My Alnico woofer cloth surrounds also pass light. I checked>the porosity by trying to breath air thru the surround and>determined there is little or none. That's all that's>important regarding maintaining a good AS seal. I suggest you>check yours before trying to seal them so light doesn't pass>thru.The speakers don't pass the "depress cone return time" test, so they appear to be very leaky. I just assumed it was the suspension because it looked so porous, but will investigate further as it could be something else.Thanks,Rod Link to comment Share on other sites More sharing options...
ninohernes Posted August 22, 2006 Report Share Posted August 22, 2006 At 10 watts input (fairly>loud at that continuous-input level), the harmonic distortion>at 40 Hz was approximately 3% or less for each version,>excellent performance by any standard -- back then or by>current standards.>>--Tom TysonTell me about it!!I was looking at the AR-2 specs, and at 15 watts the produced 100.1 dB-SPL!! That is loud, like rock concert loud! When I do large scale sound reinforcemnt for rock concerts and such I have to meter my SPL output so as not to get in trouble with the law (noise laws) and I must stay below 100 dB-SPL! It is very impressive that a home audio loudspeaker can produce 100.1 dB-SPL and stay below 10% THD at 40 Hz, and 15% at 30 Hz!! I don't suggest listening this loud as it is dangerous to your hearing, but it really shows how well these woofers perform.Off topic note:If you regularly attend loud live shows (like rock or pop concerts) PLEASE wear hearing protection! Even I do. After I get the mix tidy, I wear -15 or -20 dB fitted plugs. Hearing damage is not reversable, please preserve your hearing so that you can enjoy music for many years to come. Link to comment Share on other sites More sharing options...
Pete B Posted August 23, 2006 Author Report Share Posted August 23, 2006 >Pete, >>You mentioned that you were measuring through the xover. What>procedure did you use to determine Qts?I used Laud's T&S measurement routine which is based on input impedance. It does take the series resistance of the woofer inductor into account which is good. However, the woofer network also introduces some small error into the Fc measurement. Measures a bit lower than actual.Pete B. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.