Carlspeak
-
Posts
2,183 -
Joined
-
Last visited
Content Type
Profiles
Forums
Events
Posts posted by Carlspeak
-
-
Their specs look impressive. Are they still available at retail?
-
Hi there
I've been waiting for one main members opinion of speaker crossover caps.
He has been involved in several classic speaker designs during his life.
I value his input as, having been there, done that.
The main man is of course is the well known and respected, Ken Kantor.
Ken may too busy with large projects and his life enjoyments but his comments would be extremely valuable to everyone here.
He has faced cost in designs and surely he will have some interesting feedback if he has time to write here.
Vern:
Ken had his say on the subject of caps quite some time ago. Download this article he wrote and enjoy...
www.kenkantor.com/publications/audio_fetishes/fetish_part_02.pdf
-
I've got measurement on freshly refoamed 12100032 from an AR9. Any interest?
-
Nice Carl. Were these from mine?
Yes!
-
Boston Acoustics type (fillited) foams were used.
Values below are avg. of two separate woofer tests following fresh refoam with no breakin.
Fs=16.8 hz
Qts=.025
Le=0.78 mH
Vas=7.5 Cu. Ft
Mms=70 grams
Sens.=87 dB
BL=9.25
Although smaller in size (frame OD 10") the properties above resemble those of the AR3 series 11" woofer. The Cizek woofer even had a foam ring around the cone's surface about 2 inches up from the dust cap.
-
Something I was surprised you didn't already have is a serial number to build-year table for the different models of speakers. AR, KLH, and any others that use sequential numbering. This would be a great resource to include here and would probably bring in a large number of google hits in.
Thanks for what you have here already - this is a great resource!
This seems, on the face of it, to be a closely guarded secret. OTOH, there probably isn't a clear, well defined list all of the historians can agree on?.
-
I see you have an auto-spam blocker code word type in block in your registration area. With this in place and yet all the spams we've gotten lately, there must be a bunch of spammer as* holes out there taking the time to manually get registered.
Man, what losers....
-
Try using the advanced search function and enter soundminded's handle along with your search words. IIRC, he described it in very general terms. He's a pretty secretive guy you know....
-
Carl,
I've conversed with Tom and John, and have been been looking over the data we used for the AR-3a restoration document cabinet stuffing recommendations. The average amount of original stuffing found in all AR-3a cabinets with cloth surround woofers was around 30 oz, ranging from 28oz to 32oz. The statement regarding using this amount of stuffing for the cloth surround woofer was based on what was found to be in the original cabinets for the purposes of authenticity, *and possible unmeasured differences in upper bass and midrange response between the two types types of woofers*. In other words it was safer to state the original specification for cabinets equipped with cloth surround woofers. It was *not* based on our measurements. If it had been, and fc and Q were our only considerations, we would have recommended 20oz across the board, as our measurements agree with yours. In fact, I found fc remained within specification at amounts less than 20oz as well as over 32oz with most of the 3a woofers I measured.
Roy
I may be nitpicking here, but based on what you've written above, the first paragraph in sect. 4.3 still could use a minor revision or two in order to avoid confusion on the part of someone (like myself) using the document as a guide for their restoration. No were else in that section does it state clearly how much FG to use other than the first paragraph.
For example, if I read that my early Alnico-woofer speaker 'requires' 28-30 oz. of yellow FG, that's what I will use and, based on my earlier post and your concurrence, that is not the case.
If, instead, I read my early-Alnico woofer *required* or *used* 28-30 oz. of FG, then it would be clearer to me that's what the specification WAS ( i.e., in the past).
Thus, my suggestion is to change the word 'requires' to 'required' or, 'used' in the two sentences that describe stuffing amounts in Alnico and ceramic woofer speakers. Additionally, a sentence could be added stating clearly how much fiberglass should be used when re-stuffing. I'll leave that up to the document's authors to decide how much or give a range as you described was feasible based on your experience. I'm not saying 28-30 oz. of modern, fluffy FG won't work although it would be a tight fit. I just feel it's overkill and may provide excessive damping.
Roy, your other comment regarding the raising of Q in foam surround woofer speakers was interesting. I wonder why. Could it be perhaps the overall bass response with the ceramic woofers was not quite a good as the Alnico woofers and raising Q was a way to make up for that?
-
Page. 21 of the document states that 28 oz. "is required" for alnico magnet speakers and 20 oz. is the norm for ceramic magnet speakers. I believe this text was put into the document based on a series of stuffing measurements taken over time by one or more of the authors. Restorations I have completed with Alnico magnet woofers has shown that 28 oz. may not be required and perhaps the text of the document needs to be revised.
I recently completed restoration of an AR3 and a AR3a. Both had Alnico woofers and # 7 coils and both had rock wool stuffing. I re stuffed each with 20 oz. of OCFG obtainable from standard R-13 wall insulation and measured Fc. One speaker got 41 hz and the other 35 hz. The woofers had Fs of 16 and 19 hz. I have seen this same result once before. The 35 hz. Fc speaker had a measured Q of 0.78. The 41 hz. speaker measured 0.64. On average, this particular pair of speakers was a very respectable 0.71 with Alnico magnet woofers, #7 coils and 20 oz. of FG.
In June if last year I saw a similar result (http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2080&st=20). See post #31.
The good news here is the reduction in FG weight did not raise Q significantly - making the speaker sound like a boom box.
It's becoming evident to me that the difference in stuffing weight may be attributable not to the change in woofer type and series inductor coil but, instead to the inherent density difference between rock wool and the yellow fluffy FG AR used and modern, OC pink FG. Perhaps it took 28 oz. of rock wool to accomplish the same cabinet size enhancement effect that only 20 oz. of a more fluffy FG (my OCFG included) obtained.
if I can get the same box target resonant frequency (Fc of 40-42 hz) with 20 oz. of FG with an Alnico woofer as 28 (or so) oz. of rock wool, was the switch to 20 oz of fluffier FG around the same time as the switch to ceramic woofers just coincidence? I also question the connection is between inductor changes and stuffing with the AR3a # 7 to the # 9. The ceramic woofer had about the same Fs target (high teens) as the Alnico one. Same Fs & same cabinet volume but different density of stuffing for the same results all seem to point to mere coincidence with the timing of the woofer change. I'm just speculating here, but the bottom line is 20 or so oz. of modern, fluffy fiberglass will work just fine with older Alnico woofers and #7 inductor coils.
-
I've got a hard copy of the 10/24/2006 KLH Model Summary list. It's 3 pgs. long. It goes up to model 200, a clock radio.
Is this of any value to anybody?
-
I found a great UK brochure called "AR UK BXi & LSi Brochure" under the AR library->Special Sections->AR International->Brochures with marketing info on the UK versions of the AR product line at the time. While the version I have does differ cosmetically from the AR9LSi picture in the brochure, they discussed the 10" downward firing driver and the "special, foam-damped bass contour chamber". The design prevents bass cancellations due to rear wall and floor reflections, filling any dip in the 12" unit's response due to the floor or wall reflection. I will assume the foam should be replaced with some type of acoustic dampening foam material to match original configuration.
Still would appreciate any recommendations on replacing the "computer grade" crossover caps. I figure I can reach at least one lead on all the capacitors and snip it, then attach new caps in on the top surface of the PCB. It would be good to hear others experience with the reliability of caps from the mid-90s ARs. I know the older version were certainly almost guaranteed bad after 30 years.
The 'computer grade' caps you refer to, I suspect, are the Compulytic brand. They are of very good quality and don't drift much based on my measurements. I do recomment replacing the midrange and tweeter caps with modern film types. Let your budget be your guide to choosing which ones to get. Personal favorites are Sonicap and Jantzen for more critical applications.
I often wonder if old time woodworkers who venerred these and other vintage AR, Adven, KLH and other cabs visit these forums. It sure would be nice for them to see their handiwork revitalized like the work you have done.
-
Yes I really do like the sound of the Clarity caps, we used the SA range in my fives and I've never doubted myself about spending the extra money, I don't have the golden ears either but they do sound great and I always wonder what the difference would be if I used the SA grade in the Macs or the AR3a's where we used Solens,Daytons and Auricaps. I will say that we rebuilt a second pair of AR3a's for my youngest sons studio for a second reference pair and used the ClarityCap PX's throughout and the sound was very average at best my other AR3a's we used Daytons with Auricaps for the tweeters and they sound much better throughout the full range, I don't know if this helps, hopefully so.....
Yes, it does help. Check out this link - if you haven't already.
http://www.classicspeakerpages.net/IP.Boar...?showtopic=5828
Judging from the high number of downloads, I'd say my efforts to put together that document weren't in vain.......
-
Finished!
I revived this thread today because I wanted you (Kent) to tell me if the Clarity Cap upgrade sound was any better, same or worse than the Dayton recap job you also showed here.
Can you recall if you did any listening tests to compare the two?
-
I have some Original Large Advents I am putting together. Does anyone know what the spec would be on that cloth? Did it change any when the NLAs came out?
There would seem to be 3 challenges to replacing the grill cloth:
1) finding something that has no acoustical impact
2) getting the right density of cloth (tpi) and material
3) having backing material
I would guess correctly taking care of 2) would then result in 1) being satisfactory.
I don't have the exact specs for the OLA clothing, but I do know they used a very open outer linen cloth which necessitated the black backing cloth which, IMO, served to hide the drivers mounted behind it. In my previous post, the aluded to the NLA cloth, which I believe was very similar to the OLA in function.
The density of the cloth is a function of it's TPI and open area dictated by the thread size of the warps and weft threads. I have found >40% open area is quite good and thread counts in the 18 to 35 range are also good with fabric weights in the 4 to 6 OSY range.
-
Well ... my memory did not serve me at all. Let's try that again: "... found it to increase from 0.75 to about 1."
sorry, neurons rot like foam.
John
Thanks for the correction John (and thanks for the PM). That's more in line with my findings (see post #12).
-
Thanks John for joining in the discussion.
Now, where's my bamboo fiber analysis?!
-
Second topic: I was looking at some of your threads at AK and other threads here and saw the inductor #4, inductor #5 issue. I'll have to check to see what I have but this adds another complication for those wanting to duplicate this. I wonder if that was a conscious re-voicing or to compensate for a woofer change.
Anyone?
David
I do know AR eventually changed from fabric to foam surrounds (I just refoamed a pair). I hope John O'Hanlon chimes in here soon. He has a good knowledge of the 4x. There is an old thread here in the AR area regarding 'speaker box stuffing study' where John listed recommended stuffing amounts (not density) for the #4 and #5 coil versions. His moniker is 'johnieo' if you do a search.
-
Almost forgot...
Carl had asked for a nearfield woofer curve. I don't have an impedance curve but it looks like roughly a Q of 1 or so at 65 - 70Hz. The woofer and network inductance tends to obscure the exact Q.
Thanks Dave for the woofer curve. It's pretty much like what I've obtained. Also, nice work on fine tuning the xover. When you get it tweaked after your listening tests I hope someone else who can take measurements (Zilch? you there?) tries your new xover to confirm the effect. I don't have a 4x. Otherwise I'd give it a shot.
-
This shows the individual curves again plotted with the combined response of the whole system.
Again you can see where the individual curves overlapped excessivley the summed response shows the midrange peak.
David
Dave:
Have you tried NF measurements on the woofer? I've generally found with a number of AR4x's there is a hump in the response typical of a high AS box Q which I've measured in the 1 to 1.5 range. IMO, it was put there by design to give those little guys a bass boost which many restorer's seem to like.
-
I built one of P. Basel's BSC designs and tested it on a NLA. The parts are listed on post #103 in this thread. After first finding I had the inputs and outputs reversed with no descernable effect, I consulted with Pete and found I had them backwards. Upon switching them around, Pete's claimed effect presented itself in spades. See attached resp. plots showing without BSC (blue line) and with (red line) the BSC connected to my Insignia receiver's preamp out to amp input connections.
Consider this an independent validation of Pete's BSC design.
-
I posted a note somewhere here at CSP or on another forum that I've gotton 2 pairs of Allison 4 eight inch woofers to work on that were so encrusted with dust and lint I thought at first they had been treated with floc. However, Howard Ferstner assured me those (in-cabinet) up-facing woofers were not flocked when new, but instead had a sticky coating put on them during manufacture.
Nice to see some life in this otherwise quite forum as of late. Summer doldrums I guess.
-
Hellllppp Meeeee..... Somebody Helllppp Meeeeee.....
-k
I think that was Jeff Goldblum's line in the remake. I liked the first one with Vincent Price when I saw it as a teenager. Not as gory except how he ended his misery by crushing his flyhead in a giant indusrial hydraulic press.
-
I have a funny story to share. I recently coated a pair of older style AR3 woofers with Roy's new formulation. The next morning I went down to my shop and discovered a fly had become stuck to the cloth surround on one of them. Feeling sorry for the littly guy, I took a popsicle stick and gently nudged it free of the goo.
Lookls like I may have uncovered another use for Roy's new fabric surround sealant - fly paper!
Effect of film dielectric on capacitor ESR
in Mods, Tweaks, and Upgrades to the Classics
Posted
Detail performance tests were run on four ERSE capacitors to look at the effect of dielectric on ESR. Two 2.0 uF and two 3.9 (4.0) caps were tested. Each group had a polypropylene dielectric (Pulse-X brand with black color & gold printing) and a Polyester dielectric (yellow color with black printing).
What I found with these two levels of capacitance was a significant difference in ESR between the dielectrics in the 100 to 10000 hz range with PET generally trending higher in the freq. range evaluated. Below is a plot of the data obtained with a WT2.
IMO, the polyester ESR performance approaches that of an electrolytic. This may be of some value to those recapping that don't want to alter the voicing of the speaker or, where a slightly reduced response is needed in a particular frequency range.
The link below gives a good explanation of why ESR is different between the dielectrics.
http://www.cartage.org.lb/en/themes/sciences/physics/electromagnetism/electrostatics/Capacitors/Applications/PhysicalConsiderations/PhysicalConsiderations.htm
pp vs pet cap tests.pdf