bjmsam
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Posts posted by bjmsam
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On 11/29/2022 at 2:57 AM, Pete B said:
I read Don Keele's review of the T1030 when in was published in Audio in 1991 starting on page 81 in the .pdf here:
That review states, "Crossover Frequencies: 400 Hz and 3 kHz."
This summary states, "crossover points 250 Hz and 2,500 Hz."Which is correct?
On 11/29/2022 at 2:57 AM, Pete B said:Figure 8 in the test report shows that the system resonance (Fc) is at about 40 Hz and that the impedance dips to 3.4 ohms around 100Hz indicating that the bass section is 4 ohms even though the system is rated as 8 ohms.
Thanks for the schematic! The upper section and lower section appear to be independent (like the AR9's crossover); would the upper section behave differently with the lower section removed? Do the two sections work together like parallel resistors?
Req=R1×R2 / (R1+R2)
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Welcome to the forum! Anyone logged in should be able to download the copy attached to this post (click the black arrow at right to view):
On 12/5/2022 at 2:13 PM, genek said:The library link to the document is down. Here's a PDF.
The forum index includes this link:
QuoteFor sale / Wanted
Speakers for sale and wanted.
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On 12/7/2022 at 7:42 AM, sWilly said:
Thanks for the link. Looks like a cool project. I decided on the Mundorf E-cap's since the Solens (PartsExpress) seem to get mixed reviews. Glad to hear they worked out for you, though!
That's a fine choice. To be clear, I used M.D.L. NPEs for both my AR9C and my AR-3a projects, not Solens.
On 3/1/2022 at 8:04 AM, bjmsam said:I asked about use of NPE caps for shunts in the Capacitor upgrade in crossover - Is it audible? thread on ASR and the first reply includes, "Shunt vs. in-series doesn't have much impact as they are all effectively in the signal path" and "if you are recapping an old speaker, please be aware that the crossover designer may be expecting some series resistance to exist across some of the caps and there could be a negative impact if the replacement caps have no ESR even if they are better caps." Earlier in the thread, someone else stated, "Whenever I replaced electrolytics capacitors to film, speakers became overly bright, after some time I have to put back the original caps." 🤔
If your AR-3a speakers sound dull with new NPE caps, then rebuilding the 50+ year old tweeters (an option missing from page 11) might be more prudent than altering the xover with MKP (PP) caps to run them "hot" (see page 16).
On 3/8/2022 at 5:05 PM, bjmsam said:Well, considering the shallow depth of my enclosure, the original AR design around NPE caps, and the analysis posted in such threads as Capacitor upgrade in crossover - Is it audible? ("according to these measurements a film capacitor does not make a better sound when used in the crossover compared to an electrolytic capacitor") and Cap Value Accuracy ("At this point my opinion on using new npe's has improved considerably, and I no longer believe the "high" measurement results to be one of questionable npe quality. I strongly suspect better npe's last much longer than they are given credit for in speaker forums."), I opted to see how the speaker measures and sounds with smaller NPEs before pursuing MKPs (easy enough to replace, so nothing but a few dollars to lose). All of the parts arrived today and I began laying out sections of the network. Exciting!
*** WARNING! Images of crossovers with NPEs rather than MKPs below! Viewer discretion is advised! ***
Example tolerance:
The goal of my AR-3a recap was to restore / maintain performance and protect drivers by ensuring that the xover operates as originally designed. When it comes to upgrading sound quality, I strive to prioritize investments that objectively make a measurable improvement, and in my experience, room treatment tends to offer the most significant return. Good luck!
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8 hours ago, sWilly said:
I'm restoring a 1968 pair of AR-3a's now and had many of the same questions. It looks like you went with modestly priced electrolytic capacitors. Are you happy with the results. Trying to decide between those and the more expensive Daytons or Jantzens right now.
Yes, I did (more info here), and yes, I am!
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On 12/4/2022 at 9:44 PM, tysontom said:
Wow, another extremely impressive setup! I love that center channel, too! I did a similar "live-end-dead-end" treatment to a listening room a few years ago, and it worked really well. Are you using a projector screen setup? What all are you using in this setup? Very nice! Tom Tyson
Thanks! The AR9 pair is driven by an Adcom GFA-585 while the "AR9C" center speaker is equivalent to the top section of an AR9 mounted flush in the treated front wall behind a 120" acoustically transparent screen driven by the bridged channel of an Adcom GFA-2535 crossed over at 200Hz. A Denon AVR-X4000 configured for 7.0 surround (no need for separate subs!) also feeds Definitive Technology in-ceiling sides and KSI in-ceiling rears. Though some room challenges remain to be addressed, the setup measures extremely well and sounds fantastic.
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Great story. Thank you!
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It seems realistic to expect people to become enthusiasts about products that best achieve the primary objective(s). Relatively few today are enthusiastic about cylinder players or tube radios because every alternative performs better and is more convenient. During the classic speaker era, performance was valued most, and those products still deliver, but are not particularly convenient. During whatever era this is, it seems convenience is valued most, often at the expense of performance. LPs are a curious exception from the perspectives of both performance (IMHO) and convenience (adding that distortion electronically is easier).
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That is wild. Nicely done! How far out of spec were the original BA caps you replaced?
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I spotted this on eBay and don't know if it is authentic but figure someone might be interested or have insight to offer.
Emile Berliner Award presented to Edgar Villchur acoustic research founder 1974
QuoteThe Emile Berliner award presented to Edgar Villchur 1974.Award is for outstanding contribution to the world of sound,Edgar was the founder of Acoustic Research.Emile Berliner maker of the microphone gramophone disc record.Trophy plaque base 21 x 4 1/2,face is 17 1/4 x 5 1/4,heavy shipping by zip code actuall cost.Own a piece of sound history connected to two innovators.
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11 hours ago, AR surround said:
AR9 fronts, AR91 center, AR90 surrounds, Boston A70 rears, four Boston A60 in the ceiling plus a Boston A40 as the top, and NO subwoofers
Wow! Have you posted details and photos of this setup anywhere? That
vintage"classic speaker" approach surely rivals high-end "modern" designs.My seven channel HT employs AR9 as front left/right and my custom "AR9C" as center with DefTech UIW BP/A sides and KSI 8081-CSD rears; I have imagined including my AR90 pair and other AR (3a, 3a-Improved, 94) and BA (T830 and A60) pairs so am interested in your experience.
What I can't imagine is being satisfied with earbuds, "mono bluetooth speakers and Sound Bars..." 😞
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On 9/15/2019 at 6:02 PM, wsill said:
If anyone has built or know where to source some dense foam or felt let me know. I'd like to have some of that padding to work with that the Wilson's have on the front.
In case you're still looking, I found something close:
On 3/11/2022 at 5:41 PM, bjmsam said:For the acoustic blanket I used 1/2" thick F26N wool felt with adhesive backing, which seems like a very good alternative (more here).
It's available in different thicknesses.
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On 4/13/2021 at 8:19 PM, Rat44 said:
Lack of bass is very noticeable.
Its still there but sounds kinda 'lacking' is the only way I can describe it.
I have an old Pioneer SG 9800 12 band graphic equalizer.
Or would that be the wrong way to go about it?
Sometimes a room will not work well regardless of speaker or placement. For the MLP, equalization (preferably more granular than 12 bands, such as a PEQ or Audyssey, Dirac, MiniDSP, etc.) may help attenuate peaks but cannot eliminate nulls as those frequencies cancel regardless of amplitude. Using something like REW to simulate and measure the room would be most revealing (I am happy to help if you live nearby - can't tell from your profile). Guessing is expensive; I certainly would not divest from the AR9 before confirming that an alternative sounds better!
On 4/14/2021 at 2:05 AM, ar_pro said:Any chance that you could sketch a room layout with dimensions, furnishings & your listening spot?
On 4/15/2021 at 8:09 PM, Rat44 said:The room is 13 1/2 ft by 14 ft.
Speakers are on the short wall.
Other important aspects include height, construction, and any acoustic treatment to relieve bass pressure, which can be overwhelming. Example:
- In my home theater (much larger than your room and treated, though far from perfect), my AR9 sound a bit better than my AR90.
- In my game room (slightly larger than your room with little treatment), my AR90 sound a bit better than my AR9.
- In my living room (about the size of my home theater with no treatment) where WAF is more important, my AR-3a sound better in some parts of the room than in others.
Anecdote: I drove to Long Island to buy my AR9 from the original owner about 15 years ago. I auditioned them in the untreated living room of his tiny cape-style house and was disappointed by the lack of bass. They had been recapped, all four woofers had significant extension, and he had "audiophile equipment" (fancy turntable, glowing tube amp, "articulate" (i.e.- overly bright) replacement speakers, etc.), so I figured the room was highly modal. Upon returning home, I placed them against the wall, connected them to my GFA-585, and was rewarded with terrific sound.
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Thank you for your service and significant sacrifice. I hope you recover soon and continue cultivating your son's interest. I chimed in on your thread. 😉
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On 3/26/2022 at 7:52 PM, Brad1234 said:
Nice job! I have always wondered if the smaller, cheaper caps produce the same, or even better, sound than expensive ones? I recapped the exact same model with the pricey metalized foil polypropylene caps (Jantzen) close to $200 and have been happy with it, but it was a big expense. My AR's are currently my favorite speaker, close behind are my JBL L100s. When I tested my old AR 3a brick caps, they were crazy off, I got 325 uF for the 150, so they were shot. I also doped my woofer surrounds and dust cap with the same Vintage AR sealant I bought back in Dec. made them look shiny and beautiful!
Thanks! Being happy is all that matters. 😉 Your speakers look great! My woofer surrounds (and dust caps) were bone dry and felt like fragile paper. Now they feel much more robust, and the cone returns much more slowly after being displaced. One coat seemed adequate.
Any difference in sound is too subtle for me to hear. Here is a graph of the woofer section measured on-axis in my room before and after sealing:
Since a 100Hz HPF was inadvertently engaged on the AVR channel used for the measurements I posted earlier comparing before/after capacitor replacement (inconsequential but annoying), here is a final graph of measurements on-axis in my room with everything done and dialed in:
The speakers are well aligned and not responsible for deviations from the red AR tech data trace as acoustic treatment of my room remains a work in progress... 🤔
Thanks again for the outstanding guide and support!
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As in my center channel project thread:
*** WARNING! Images of crossovers with NPEs rather than MKPs below! Viewer discretion is advised! ***
The new capacitor measurements for left and right were virtually identical so those below from one or the other are representative. High readings are typical as discussed in the Cap Value Accuracy thread. According to someone who posted a review of my Proster LCR meter, it measures capacitance using a 300Hz triangular 200mV pk to pk voltage waveform. I have found no such information on my TC1, which reads the same as the BM4070 for the larger caps, though for the small caps, it reads lower individually but higher when in parallel. Vloss sure looks better...
2.7μF + 3.3μF capacitors:
50μF capacitor:
150μF capacitor:
Reassembly:
Measurements and Impressions
Before vs. after graph below. Again, the green and orange traces are RMS averages of measurements on axis aimed between tweeter and midrange at 0.5m and 1.0m from the same position in my room. All pots now work but I did my best to position them the same as before for consistency. Digitized and SPL aligned at 400Hz for reference are the two curves posted in the AR-3a response curve thread.
*Edit 2022-03-29: A 100Hz HPF was inadvertently engaged on the AVR channel used for these measurements hence the lack of bass extension.
Any difference is too subtle for me to hear - they sound terrific! All that's left to do is apply cloth surround woofer sealant, which is on the way now that Vintage-AR has returned from vacation. I will measure before and after (with the AVR's HPF disabled this time) to see if there is a difference in output.
This has been a fun project and I am very pleased with the outcome!
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Here is 06064:
6μF capacitor:
50μF capacitor:
150μF capacitor:
The potentiometer that I was unable to adjust:
After DeoxIT and emory cloth:
The other pot looked (and mostly worked) fine so a little DeoxIT was all it needed.
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"Before" graph below. The green and orange traces are RMS averages of measurements on axis aimed between tweeter and midrange at 0.5m and 1.0m from the same position in my room. One of the pots on S/N 06064 works only near its maximum setting, so I set the other three the same for consistency. Both speakers are as they came from AR in the late 1960s except the pots in S/N 06052 and the midrange driver in S/N 06064 were replaced in the late 1980s. Digitized and SPL aligned at 400Hz for reference are the two curves posted in the AR-3a response curve thread.
*Edit 2022-03-29: A 100Hz HPF was inadvertently engaged on the AVR channel used for these measurements hence the lack of bass extension.
Has anyone already modeled the AR-3a crossover in XSim?
If not, are the FRD and ZMA files available for all three drivers? -
15 hours ago, RoyC said:
Well, you could have told me that before I licked the foil!
But per the Old "Block" Caps thread, you did inhale! 😉
According to the Early Capacitor Manufacturing History thread, AR discontinued use of PCB caps several years before the AR-3a was introduced (but beware of early serial-numbered AR-3 speakers made through the mid-1960s). The wax-paper-impregnated caps that replaced them had an even lower ESR, and both were orders of magnitude less than that of NPE caps. These statements by @johnieo are most relevant to the questions I posed earlier (note that he inadvertently reversed the crossover frequency change, which decreased rather than increased).
QuoteThese [NPE] ESR values are so high that it is obvious to me the speaker designer of the 1970s had to include that resistance in the calculation of the crossover frequency, and thus the legitimate concern when they are replaced with low ESR polypros.
Quote--AR-3a: we observe that the ESR of paraffin caps was much lower than for NPEs and that the crossover frequency WAS affected--it increased from 525 Hz to 575 Hz from early to late models.
He and @r_laski also provided some very interesting cap descriptions, measurements, observations, and recommendations here.
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Thank you! Very interesting. So AR replaced those wax-paper-impregnated caps with NPE caps of equivalent capacitance (but presumably different Equivalent Series Resistance, Dissipation Factor, Dielectric Absorption, charge migration, etc.) with no other changes to the crossover network than one inductor that most likely was to accommodate a different woofer driver?
I do not have a way to measure caps like @Carlspeak did in the HERE'S WHY YOU SHOULD REPLACE THOSE OLD 3A CAPACITORS thread as I have only an LCR tester (and a TC1 tester that does not always show ESR) but will use REW with a calibrated UMIK-1 microphone to measure speaker output (in my room) before and after as @genek requested in that thread.
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Thank you! I agree and am thankful to have had the privilege of literally growing up with this pair. After 54 years of continuous use, they still sound terrific and are most deserving of my attention. CSP is a treasure!
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Echoing feedback posted over the past fifteen years, the guide is terrific and most appreciated! I am preparing to dig into my pair which Dad bought new in the late 60s (serial numbers 06052 and 06064). I am comfortable with NPEs (recently employed with success in my center channel project)...
On 10/15/2009 at 10:53 AM, JKent said:The originals were non-polarized electrolytics and therefore cheap NPEs should work just fine
On 2/6/2022 at 11:00 PM, RoyC said:Ken Kantor's opinion was to simply use electrolytic capacitors if you want the best representation of the original sound.
The fact of the matter is that modern electrolytic capacitors behave more like AR's original AR-3a caps (all iterations) with respect to ESR.
...but what are the early caps, exactly? The guide seems somewhat ambiguous on this point:
QuoteThe early crossover used a physically large, dual 150/50-μF woofer/mid-range capacitor and a separate 6-μF hi-range capacitor. The later crossover used individual non-polarized electrolytic capacitors encapsulated in aluminum cans.
On 10/19/2009 at 7:22 PM, Tekker said:I have the original block caps and I don't believe they're electrolytics.
Also, the guide states:
QuoteVery early cabinets used a 1.88-mH AR #7 woofer inductor, but that was changed to a 2.85-mH AR-#9 coil to correct a slight “bump” in the speaker’s upper woofer range power output.
Since my woofers have cloth surrounds, the #7 inductor should not be replaced with a #9 coil, correct?
On 2/9/2011 at 3:21 AM, RoyC said:-Cloth surround woofers and very early foam surround 3a woofers were at the lower end of the 18 hz+/- 15% fs specification, and the later, foam surround versions were at the higher end.
-There are response differences between the two types of woofers, which is the most likely reason for the change from #7 (1.88mh) to #9 (2.85mh) woofer inductor.
Sure glad I saw this - thank you! Perhaps the guide should be updated for those not poring over every post?
On 9/23/2020 at 4:46 AM, roundcubenine said:The AR-3a guide mentions using Permatex High Tack Gasket Sealant to reseal the fabric woofers, but I heard some complaints about this stuff, so I just bit the bullet and ordered the good stuff from Vintage-AR on eBay. It's about double the cost, but a lot cheaper than ruined woofers!
On 9/23/2020 at 2:57 PM, JKent said:Good call! That recommendation to use Permatex slipped into the Guide before it was thoroughly tested over time and it turns out the stuff eventually gets stiff and ruins the surround. RoyC, an author of the Guide cooked up the stuff sold by Vintage AR and it's authentic to the original goo.
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The first graph compares the response predicted by XSim for the AR spec crossover (red) and my crossover (green) to the response of my center speaker C (purple) as measured by an Audyssey microphone positioned on-axis aimed between tweeter and UMR from 1.0M, 2.0M, and 3.0M (RMS average). The screen was not in place, Audyssey was off, and a GFA-585 was used for C (swapped with R temporarily).
The second graph compares the response of C alone (purple) vs. C with L+R handling frequencies below 200Hz (green) vs. R alone (red) as measured by a calibrated UMIK-1 positioned on-axis aimed between tweeter and UMR from 1.0M and 1.5M (RMS average). The screen was in place, Audyssey was off, and a GFA-2535 was used in bridged mode for C.
The third graph compares C with Audyssey off (purple) vs. C with Audyssey on DEQ off (orange) as measured by a calibrated UMIK-1 positioned at three locations left, right, and center of the MLP (RMS average). XSim traces are included at the top for reference. The screen was in place and a GFA-2535 was used in bridged mode for C. The orange trace approximates what I hear when listening to content.
Observations:
- The SS AR-12000840 Acoustic Research Genuine .75" Dome Tweeter seems uneven (but so is that section of the crossover, presumably to match the original 200029 driver - the AR9 R on-axis (red) trace in second graph looks flat); it would be interesting to see how the MW Audio MT-4121: .75 inch Dome AR Copy Tweeter measures in comparison.
- The MW Audio MM-2044: Acoustic Research Copy Midrange UMR seems to perform well, and arguably is most important.
- The AR 200027 original driver LMR is not performing to the spec below, which seems unrealistic.
From the library:
I had overlooked Note 11 during assembly so just now stuffed the LMR enclosure with Roxul AFB to see if it would smooth and extend its frequency response but noted little difference between with wadding (light purple) and without wadding (purple). Included for reference is the AR curve (red) digitized from the AR graph above and the crossover response predicted by XSim seen earlier.
What I am measuring is consistent with what XSim predicts for the AR spec crossover (and my crossover is very close, at least when ignoring unknown ESR and DCR values). Even ignoring my room challenges (note similar boost above and suck-out below 300Hz in my AR-3a curve), I really don't see how an AR spec LMR driver (which I am using) could roll off so low or steep without a change to the crossover. Adding the woofer section of the network to XSim did not change the curve significantly above 200Hz. I simulated some straightforward changes to my crossover that might help (comparison below) but probably won't bother since the HPF in my AVR seamlessly routes those frequencies elsewhere (green AR9 C on-axis sub 200 trace in second graph) and all of the speakers working together as a system sound well integrated. I am very pleased!
On 10/19/2017 at 12:43 PM, Stimpy said:I 'think' it will be fun.
It sure was! Thanks again for the inspiration and input.
Ar9 Restoration
in Acoustic Research
Posted
Wow! What a transformation. An epic journey for sure. Congratulations!
How did you remedy the mold on the woofer cones?