Pete B
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Posts posted by Pete B
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This would be my pick for a quality unit at a reasonable price, no idea if the dimensions fit,
or if crossover mods would be required:
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They are the worst!
How are you doing Roy, have not seen you since that Frankenfest years back?
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The difference between the 16/16/3 and 16/8/3 crossovers only matters, with regard to the caps,
in the "Extended" switch position. The speaker is too bright even when set to "Normal", so the 8uF
cap is better because it makes "Extended" less harsh sounding.
I've said this many times, the tiny Red Dot inductors in the 16/16/3 crossover tended to burn out,
there was a service bulletin about testing them. I suggest replacing them with 18 or 20 ga air core.
Also, Rockwood resistors tend to fail and I always replace them when rebuilding.
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You'd be surprised to find what people have sitting on their shelves. I'd try a wanted to buy here
and at PE Tech Talk and AudioKarma.
Pete B.
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Do you have OLA's or NLA's? I'd guess OLA's and I would not knock out the crossovers.
You probably burnt up the red dot inductors if your speakers have them.
The woofers might make sound but are you sure that they didn't bottom and bend a voice coil former
or damage anything else?
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It means that if you operated them at the max rated temp, and the max ripple current then
they will last at least 2000 hrs. As used in a speaker they'll last as long as most electrolytics.
No other issues wiring them in series.
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I said, years ago, that I'd try to find a good solution for the 2500uF cap, it should be
(very) low ESR. I'd probably use a pair of back to back polarized snap-in caps because
they are designed for very low ESR. Consider that these are in series with the large
inductor and there will be a point of diminishing returns.
Right now I'm looking at 5000uF 100V, Mouser #661-ESMQ101D502MA40S putting them
back to back drops the value in half.
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Removing that cap and coil does not lower the impedance, it allows the system to peak higher
at resonance (harder to drive because it is more reactive), and lowers the output at resonance.
The only advantage is not having to replace that large 2500uF NPE cap.
I explain it here, and Tom Tyson agrees:
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Correct
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I called Ulster yesterday to ask about thread count at about 5:30 PM, a lady answered and
very abruptly said what's your name I'll call you back. Gave it a 50/50 that she'd call back.
She called this morning and I asked her about thread count, she finally said that the
Y0400NT036 36" wide material was in fact closer to 25 TPI, and that
Y0400NT060 60" wide material was around 20 TPI
She also said that the 36" wide material was slightly lighter in color than the 60" wide.
So you can get 20 or 25 TPI depending on what you need, of course call to confirm that
the thread counts have not changed.
I might order 1 yard of the 60" wide material to see if I like it more than the IL041 from
fabric-store.com.
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On 2/1/2022 at 7:16 PM, genek said:
I ordered a yard of my best pick from Ulster Linen. It arrived this week and if I can figure out what I did with my staplegun (which I haven't seen since before we packed up to move to Portland eight years ago!) I have a spare pair of 3a frame boards I can mount it to.
It's undyed, unbleached natural flax linen. We figured out a while back that it's 20ct. Here's what the loose yardage looks like.
I also ordered this linen (Y0400NT036) from Ulster, it arrived today and I count 24-25 TPI not 20, not sure if
it varies from batch to batch since they do not quote a number for TPI, or what might have caused the change.
I like a more coarse and open weave so I'll only use this with speakers I'm certain had a higher thread count.
Perhaps Dyna A-25 s.
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On 5/28/2021 at 6:11 PM, genek said:
The 2ax's I bought new in 1975 had a finer grill cloth than most of the earlier ARs I've seen, including the early 6s I used to have.
Here's a scan of some AR fabric, year unknown, and a ruler. My old eyes aren't up to counting the threads, but if anyone else wants to give it a shot...
I count about 24 maybe 25 TPI, thanks for the picture. I don't like the look of such a high TPI but it is what it is.
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I took a closer look at the Ulster medium weight natural and it looks from the
pictures to be very close to Advent cloth color, but the thread count is too high,
and the typical AR cloth looks even better. I ordered one yard to see it in person
and to count the TPI.
Edit: This arrived and I count the TPI at 25 which is far too high for Advent grills.
It is fairly open weave but not as good as the 18 TPI Irish Linen from 123Stitch,
or the 19 TPI (IL041 Oatmeal) from Fabric Store.com.
I did two grills many years ago with the Irish linen from 123Stitch and have them
here to compare. The other fabrics are not mounted but the Irish linen looks best
then, the 19 TPI, and lastly the 25 TPI from Ulster.
Ulster does not provide TPI for many of their fabrics so it is difficult to determine
which material is best.
One more note on the IL041 19TPI is that the threads are very fine making it a very
open weave. I will probably use this for all my speaker restorations that call for a
white/natural fabric. It is the best I've found so far.
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I found Horswispr's review on the Wayback machine, hope you don't mind:
Pros: smooth, warmish sound; attractive real walnut veneer; excellent with choral music; relatively inexpensive
Cons: a bit thick in the lower midrange on some music; fairly large footprint
Marantz Imperial 6s are sleepers among loudspeakers from the 1970s. They are large, ported two-ways that didn’t sell as well as the three-way Marantz Imperial 7, but are now thought to be much better speakers than the 7s. The Imperial 6’s tragic flaw was that they were tonally neutral and didn’t stand out in a showroom full of speakers crying out via boomy bass and lower treble peaks to be taken home. There’s some interesting information on the internet about the Imperial 6 and Imperial 7, and some comparisons conducted by Marantz’s designers between their Imperial 6 and the best-selling Large Advent Loudspeaker. Google “Marantz Imperial 6 Large Advent” and Patrick Hart’s article “Loudspeakers: When is Good Enough, Enough?” will show up.
A pair of Imperial 6s recently showed up at my house for refinishing, so of course I had to give them a listen. Each Imperial 6 is approximately 25 ½” tall x 14 ¼” wide x 11 ½” deep and weighs about the same as a KLH 6, or about 32 lbs. The Imperial 6s are basic ‘70s boxes, resembling KLH 6s and AR-2axs in overall appearance. The cabinets are finished in real walnut veneer that appears to be comparable in quality to that used by Acoustic Research, KLH and Advent during the same era. The pair in my possession has no grilles, but I beleive I read somewhere that the original Imperial 6 came with dark tan cloth grilles. Some Marantz speakers (possibly including the Imperial 7) came with gaudy foam grilles that tend to rot over time. I think the Imperial 6s look quite nice naked.
The Imperial 6s are a two-way ported design featuring a 10” treated cloth-surround paper-cone woofer and a “phenolic ring” cone tweeter (you can read about the tweeter on the Parts Express website; part # 270-252). The large port is beneath the woofer, toward the left side of the front baffle. According to the above-mentioned Patrick Hart article, the Imperial 6s were the first loudspeaker designed for Marantz by Dawson Hadley, probably with guidance from his mentor at Marantz, Bart Locanthi. The Imperial 6s were said to have a frequency response of 60hz to 17,000hz.+/- 1.5 db, which is pretty darned smooth for a relatively inexpensive loudspeaker. They were made in the United States.
Hook-up and listening.
The Imperial 6s in my possession had little flat screws like those on Dynaco A-10s for speaker wire attachment, and they worked fine, though they’re close enough together that you have to be careful not to let stray strands of wire touch the wrong terminal. I hooked them up and placed them on my 20” speaker stands about 2 1/2 feet from the rear wall and separated by about 7 feet.
We listened first to Gary Burton’s Like Minds CD, an excellent jazz recording featuring Burton on vibes, Pat Metheny on guitar, Chick Corea on piano, Roy Haynes on drums, and Dave Holland on bass. I was immediately struck by how large and effortless the music sounded. Cymbals were natural and not overly sibilant or splashy, and the bass was surprisingly tight and punchy. Compared to the recently reviewed KLH 5’s, sound “came out” of the Imperial 6s more, but it was not more aggressive, nor was it more strained. There was some lower-midrange thickness through the Imperial 6s, which my audiophile friend said made the sound a bit “busy,” but I thought it added a bit of a sense of authority to the presentation. I was reminded of the A/D/S 810, which I also thought had a bit of a lower midrange hump, though the Imperial 6s may be a tad brighter than the 810s.
On Alison Krauss’s Paper Airplane CD, the sound was again really smooth. I thought Krauss’s voice was presented beautifully, with little or no CD edge, and a very expansive soundstage surrounded her. Guitars sounded realistic, mandolin and banjo had bite without being thrust forward in the sound stage, and bass was surprisingly tight. Most importantly, I found the presentation emotionally involving.
But it was Cantate Domino, a Proprius “audiophile” recording of organ and chorus, that really won me over with the Marantz Imperial 6s. I don’t think I’ve ever heard massed chorus sound more relaxed. And the air of the church was presented more convincingly than I can remember hearing. When I switched to my KLH 6s, one of my familiar vintage reference speakers, the sound was similar, but both solo vocals and massed chorus sounded just a bit “edgier,” and the air of the church was not as noticeable. On this recording, I definitely preferred the Marantz speakers.
On an EMI Classics recording of Arthur Rubinstein playing Chopin Nocturnes, the Imperial 6s were not as focused as were my “Customs” (Dynaco A-25s with Dayton soft dome tweeters) or the previously reviewed KLH 5s. Same with Keith Jarrett’s Standards Live, with Gary Peacock on bass and Jack DeJohnette on drums: The piano in both recordings lost a little of its attack, and the image of the instrument was a bit diffuse. I came away with the impression that the Marantz Imperial 6s are not at their best with piano music, though I hadn’t noticed any issues with Corea’s piano on the Gary Burton CD. And to confuse things further, the piano sounds fine on Stan Getz’s Serenity CD, which I’m listening to as I write.
With a friend’s CD recording of Holst’s The Planets, the Marantz Imperial 6s were really back in their element. The scale and depth of the music were both well-presented, and the soundstage was three-dimensional and placed mostly behind the plane of the speakers, meaning that orchestral climaxes were enjoyable and not thrust into the listener’s face.
With Greg Brown’s The Poet Game CD, the Marantz Imperial 6s surprised me. I expected Brown’s gravelly voice to sound full but a bit diffuse. Instead, it was crystal clear and dead center, but with less heft than I expected. It was satisfying, but in a different way than I had anticipated.
Conclusions.
I admit that I am surprised by how much I enjoyed listening to the Marantz Imperial 6s. They come from an era when mid-fi loudspeaker designers still cared about sound quality, and were torn between what’s right and what sells. The Imperial 6s were designed right, and it shows. I consider them to be fully competitive with the better known classics of their day, including KLH 6s, Acoustic Research AR-2axs, and Large Advents. Which you like best will be a matter of personal taste, as well as the music you are listening to.
It’s worth noting that all of the speakers mentioned in the previous paragraph are acoustic suspension designs, while the Marantz Imperial 6 is a ported design. In theory, the bass of a comparably sized acoustic suspension speaker should extend deeper (and efficiency should be lower), but I found the bass of the Imperial 6s to be quite good on the Proprius organ and chorus recording. Perhaps they give up something in the bottom octave, but I didn’t notice it. As expected, the Imperial 6s were more efficient than the other speakers, and generated a higher SPL for the same volume control setting than the KLH 6s, Dynaco A-25s or my “Custom” A-25s with Dayton soft dome tweeters. Their high efficiency makes the Marantz Imperial 6s especially well-suited for modestly powered tube amplifiers, like my 17 watt per channel Fisher X-100B.
In my system, Marantz Imperial 6s had a really surprising combination of smoothness, soundstage depth, and, on some music, an almost Klipsch Heresy-like presence and immediacy. They may not be pin-point imaging champions (though they surprised me on the Greg Brown CD), and they may not at their best with solo piano (though their performance with piano seemed to vary with the recording). But they are really good with choral and orchestral music, and I thought they did a nice job with female (and male) vocals as well.
Retail price of the Marantz Imperial 6 was $129 each in the early 1970s, but today you could probably find a pair for well under $200. My guess is that cosmetically challenged pairs could be found for well under $100. Because they didn’t sell well in their day, they are probably rarer than Dynaco A-25s, Acoustic Research AR-2axs, or Large Advents. But if you see a pair out there in working condition, I recommend you give them a listen. I may just add this pair to my permanent collection.
Associated equipment used in the writing of this review: NAD 521BEE CD player; Kenwood KT-7300 tuner; AR ES-1 turntable with Shure M97xE cartridge; NAD 1020 preamplifier; Fisher X-100B tube integrated amplifier; Dynaco A-25 loudspeakers; Dynaco A-25 loudspeakers with Dayton soft dome tweeters; KLH Model 6 loudspeakers; DCM Time Window loudspeakers; M&K V-2B subwoofer. -
Back in 2016, you wrote:
2-9-16
Back in 2014, when I first hooked up my newly re-foamed AR-9s, I had plenty (6) PL400s to try the ‘bi-amp’ configuration.
Having never heard AR-9s in my home before, I was very excited that I could actually ‘bi-amp’, something I had read about often but never tried before. I didn’t get the pleasure I was seeking because one of the aging amps failed in a few days, then another failed, then another. Consequently, I have given up until I get those old amps rebuilt, which will probably happen later this year. But, I did a few days of listening.
Obvious to me, I did not receive the effect I was expecting while the amp was running just before it gave out. What I did notice first off was that the speakers were not properly set up in the room as the speakers were sitting one third in the room when they should have been against the front wall for best bass output and balance.
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I mentioned that you were having problems bi-amping AR-9 s, your name didn't
come up until it hit me that you two might have talked. I'm very curious to learn
about what went wrong bi-amping, probably needs a zobel.
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@frankmarsi I went to a CT Audio Society meeting today and met Ed Blackwood today. We
had a very long talk about power amp design and Phase Linear. Ed is very well known for mods
and repairs of Phase Linear amps. He is very knowledgeable and has a passion for power
amp design. He moved from the West coast to CT so he's closer now.
This is his webpage on the Wayback machine, he is still in business but not keeping up the web page:
https://web.archive.org/web/20080924133620/hometown.aol.com/phasetek
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Interesting, do you know how the measurement was taken?
The Mmd looks high, since this is supposed to be similar to the later ceramic version where
we've seen the AR design drawings that spec Mmd at roughly 70g. I've actually removed
the cone and voice coil and weighed it on a scale with a reading close to that.
I got a very high Mmd when using the delta mass method that I always use.
When I finally tried the delta volume method I got reasonable numbers.
Here's the old thread:
https://community.classicspeakerpages.net/topic/1408-ar-11-woofer-200003-measurement-refoam-repair/
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The KLH, obviously also a design by Kloss, has a half roll cloth edge treated
with probably the same goop that AR used on their cloth edges. Good description
is in the literature. It even looks a bit like the LA woofer.
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You say grille cloth, but do you mean to say the grille frame including the cloth?
This is important because the tweeter protrudes from the baffle board and the
grille frame is needed to provide a smooth baffle for it. The notch without is most
likely diffraction from not having the grille frame.
This has been noted for a very long time that OLAs require the grille for proper
operation.
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Thank you for these measurements.
These mids have a sealed box HP electro-acoustical response that is only slightly off
from a Butterworth (B2) alignment. Fs or really Fc is the -3dB frequency and the Qts is
.66 to .69 with .707 being Butterworth.
I've said this before but might as well repeat it here, a Linkwitz-Riley 4th order alignment
has been called Butterworth squared because the 4th order response is the cascade of
two B2 HP filters with the same Fc. If the crossover is B2 (Q=.707) with F3 about equal
to the Fc of the drivers then it would be a Linkwitz-Riley crossover. This could be by
coincidental or one group knew of the other's work.
What is clear is that AR moved the Fc of the mids to roughly match the crossover point
and that is a good thing.
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Ah, very good!
Here's the old thread where I measured them, it was in 2005:
https://community.classicspeakerpages.net/topic/1408-ar-11-woofer-200003-measurement-refoam-repair/
There was another that showed the bent former but I'm having trouble finding it, I think it was deleted.
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Nice work, what did you use to release the spider glue around the outside if you don't mind my asking?
Also, it looks like you released the glue for the dust cap, did you use the same solvent ... or something else?
I did a similar repair on an AR-11 woofer and found a black anodized voice coil - that was a long time
ago maybe 2007 and I'll see if I can find the thread.
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I have a pair of "franken 3-way" Large Advents that have the round magnet Jensen woofer.
No idea where the person got the woofers, both have the 10-990-536 number on them but
one has a date code of 285 85 28 for the 28th week of 1985 and the other 220 82 43 for
the 43 week of 1982 the later one has an extended center pole piece by about 1/8" the
other is flush with the top of the top plate. Seems that the extended pole piece is a
refinement to the design. I don't recall ever seeing an extended pole piece on any other
large advent woofer.
Seas 25TV EW Theile Small parameters - Qts & VAS values way off
in Dynaco
Posted
Qe and Qm scale linearly with Fs, so part of the error can be accounted for due to the Fs difference.
Consider that a base set of measurements do not require the delta mass or compliance second
measurement. Fs and the Qs are included in that and Fs simply requires an accurate generator
which should be easy with a digital source. You could check for distortion in your gear, do you
have an oscilloscope to have a look. You could try to confirm Fs by the old way of using a high
impedance source and just measuring the voltage peak with a voltmeter. I'd say that this is the
first step.
The Q values can have error due to resistance in your test leads or calibration error. If your system
can measure impedance try an 8 ohm resistor and see if there is error across frequency.