kkc
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Posts posted by kkc
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On 12/9/2020 at 11:53 PM, DeSelbyofDalkey said:
I installed the Midwest Speakers tweeters in my AR90s. They are very, very good—at least as good as the original AR tweeters: Wider, smoother response than the originals from my pair. They do not use the AR tweeter plastic bezel, so dispersion is wider than original. I contacted Midwest Speaker and they said that using the original tweeter plate on top of their tweeter is fine as long as it is not screwed in too tightly. I tried it and the AR plate does see to focus the treble a bit more, but until I get a second bezel I cannot know about the effect on two.
The Midwest Speakers tweeter is slightly more efficient (more sound per watt) than the original. It somewhat upset the balance of the entire speaker. Not terribly, but noticeably so. The -3db switch reduced output slightly more than I wanted, so I will probably try installing a 1 ohm 22w resistor to see if it helps match the tweeter to the rest of the speaker better. I can live without it, but I want to try.
For the price, the Midwest Speaker are still excellent options. They are very well made and are straight drop-in replacements.
Thanks for the feedback on performance. I was wondering if I should experiment or use drop-ins with my blown tweets and aging UMRs...! Still ummin...and aaaahin...!
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On 4/21/2021 at 11:55 PM, Stimpy said:
When you refurbed your 9s, did that include a recap? If not, defective capacitors can definitely cause static distortion. I've recapped ARs that exhibited distortion before a recap, and everything was completely clean afterwards.
On 4/24/2021 at 4:00 AM, DavidR said:What Stimpy said above.
Those old caps begin acting more like a resistor than a capacitor. I thought my AR90s tweeters had dried ferrofluid as they were very dull. New caps corrected the muted sound.
Yes, I completely overhauled the XO a few years back. I am sure that the XOs are fine. More details here: AR9 refurb. I also have a pair of AR94si and I refurbished these as well. More details here: AR94si refurb. In the AR94si, the tweeters were dried out and sounding scratchy. In my AR9, they are blown (tested with a multimeter). Additonally the UMRs sound a bit scratchy. I suspect that this is because after around 50 years the ferrofluid has dried out.
Since both the tweeter and the UMR are closed, these should be the easiest to replace with drop-in improved drivers. I don't feel like paying usd500 + shipping to Europe for the AR tweeters and UMRs.
Now here's whats interesting regarding the AR94si tweter upgrade to Dayton DC28F-8. The impedances of the old AR94 should be 4 to 6 Ohm (I have seen both numbers) and the Daytons are at 8 Ohms. The sensitivity is 87 or 90 (again seen both numbers and remember 3db = doubling of volume!) vs 89 db (Daytons). Finally power handling is 125w vs 50w (Daytons).
So despite quite significant differences, the tweeters really work well with the other two drivers....! -
Just a quick update.... i had promised to look into testing the ADI-2 DAC with some headphones and the result was NOT good. I tried some sony and sennheiser noise cancelling phones as well as some $30 over the ear phones and all sounded awful and underpowered. I called the company and they said I had to use very high sensitivity headphones and as I don't have a pair of such phones, I can't do the test that is necesdsary. Sorry folks...!
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On 7/8/2020 at 10:25 PM, ar_pro said:
The ADI-2 DAC looks like a terrific piece of equipment, with an extraordinary number of useful features.
This is a little off-topic, but have you tried it with headphones yet?
Hmmm... so i tried yesterday and discovered a problem. On three headphones, the max volumes were rather low. Have contacted the company and awaiting suggestions. Will post updates.
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8 hours ago, DavidR said:
Has anyone heard from 71 since his promising results?
Not here and not on AK. Gone missing. I have 2 tweeters for him.
Thank you DavidR and seventy1... the tweeter dissection / oil change post is brilliant.
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18 hours ago, Aadams said:
You sure your problem is not the DAC?
Hello Aadams, no the DAC is very revealing and the net effect has been to improve the sound in all areas by a huge amount. Perhaps I did not explain clearly. The speakers sound very good. I am just looking for that extra clarity. I have already done a lot of work on these speakers (see the link below). Now after 10 years, I wonder what more I can do to improve the sound. In any case, I know the XO connections need de-rustingand this time I would also like to solder the connections.
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Hello Everyone,
It's been just over 10 years and I have been really enjoying my refurbished AR9s. I recently added a DAC (RME ADI-2 DAC FS) and I can't believe the improvement in sound. If anyone is considering adding a DAC, I would definitely recommend.
One downside however is that the DAC also shows up distortions in the drivers and consequently, I am now thinking of either renewing the ferrofluid in the tweeters and the UMR (I dont hear the tweeter at all (could be age...!) and the UMR can sound a but scratchy at times) or replacing with modern dropin equivilants.
Having replaced my tweeters in my AR94Si with cheap Daytons (https://www.parts-express.com/dayton-audio-dc28f-8-1-1-8-silk-dome-tweeter--275-070) I was really amazed at how liquid, open and warm the sound was. There is something to be said for the tighter modern tolerances, designs & materials.
My preference is to upgrade the tweeter and UMR. I can't find any information on possible upgrades for the UMR except for this: https://www.simplyspeakers.com/acoustic-research-replacement-midrange-12100103.html.
And for the tweeters, I see there are two options https://www.simplyspeakers.com/acoustic-research-replacement-tweeter-12000840.html and https://www.midwestspeakerrepair.com/shop/home-audio/mw-audio-mt-4121-75-inch-dome-tweeter/.
None of these replacements excite me and the prices seem a bit on the high side. Does anyone have experience of these or other replacements or of replenishing the ferrofluid?
Thanks in advance...!
kkc
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I think it's time we have a pinned topic for the "Restoring the AR-3a" document developed by six of our esteemed members - Roy Champagne, Ken Kantor, Minh Luong, John O'Hanlon, Bret Thiel, and Tom Tyson. The document is available here:
http://www.classicspeakerpages.net/library...ring_the_ar-3a/
Per John's suggestion, I have put a counter on this page (available when I run statistics) so we can see how popular this document becomes.
If you have feedback on the document and how it has impacted your restoration project, please reply to this thread.
Mark
Excellent document, please do not remove even if page count is low.
AR9: refurb or replace tweeter and UMR
in Acoustic Research
Posted
Update:
So having tested the UMR, they are fine and I connected them back into the AR9 speakers. The tweeters on the other hand were both shot.
I have now installed Tymphany Peerless XT25BG60-04 costing about 25USD each. These are Scandinavian designed
, made in China 
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One needs to add a wood collar to the hole for the tweeter as the flange diameter is less than on the original AR tweeters.
How did I choose these?
I matched the power (80w rms) and the impedance (8 ohms). I was unable to find tweeters that were low sensitivity, but figured that this parameter is the easiest to manage by increasing resistance as modern tweeters are about 3db to 6db louder for the same power input.
I then looked at the frequency charts of Daytons and Peerless tweeters. On axis for almost all tweeters is really excellent. Off axis is where the differences start to emerge. But almost all the charts were quite similar. Oddly enough the much mor eexpensive tweeters (Scanspeak etc) had charts which were quite different (mountain top vs. flat). I was looking for a flat response between 7k and 15k. Above 15KHz, it's kanda hard to hear much.
How do they sound?
They are much louder, so I have to use the XO resistor switches to max resistance (position 3), with teh UMR and LMR set to no resistance. Thereafter, they sound really nice. To give you some idea, I can hear singers breathing in to collect their breath as they sing. Watching movies, you can hear faint sounds coming from other rooms within the movie. On the lowest volumes, you can easily hear the UMR and the tweeter, less so the LMR and not at all the woofers (should give you an idea of what I mean by lowest volume setting).
These tweeters are quite directional and also have almost a horn like effect similar to the UMR. If you toe in at about 45°, you have superb effortless imaging, but the sound stage also feels a bit closed. If you do not toe in, the sound is spacious but with some loss in imaging resolution. The ideal is somewhere inbetween, probably also by decreasing resistance to the mid level position (position 2) to compensate for off-axis drop.
Overall, the sound is amazing. There is beautiful rich tonality of voices which complements the UMRs. It's as though the singer is in your living room! And there are also rich sweet highs (cymbals, flute, synth etc). At times however depending on the music, sound can be compressed. When this happens, the natural reaction is to reduce volume. Not sure what is going on here. I'll let the tweeters bed in and see if things change.
Not sure about fatigue yet as I have not had the chance for extended listening.
Overall, I am really happy. I expect that as the tweeters bed in they should improve in sound quality.
Still blows my mind that 50 year old speakers can easily best speakers costing 20k and above!
Interesting observation:
As the frequency range goes quite low, I plugged these tweeters in to the UMR XO. Well, I must say, I was very surprised at how they handled the lower frequency ranges. They sounded very good. It would be interesting, had I the time, to experiment a bit more.
Other tweeters I looked at (on paper only):
XT25SC50-04, NE25VTS-04, XT25TG30-04, SB26CDC-C000-4, RST28F-4.
I would have bought the Dayton RST28F-4, but these were not in stock. I used a similar Dayton in my AR94si and was amazed at the sound. However I feel that the Peerless is much better at vocals, so in retrospect, I am glad I bought the Peerless.
I have attached a comparison of the freq response charts. The orange box shows the response between 7k and 14k.
AR9 Tweeter Replacement Comparisons.pdf