Stimpy
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Posts posted by Stimpy
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From the close up picture of the coated cone, it looks like it was treated with Parts Express Wet Look. I've used it before, to treat stained woofers, and Wet Look has that same translucent shiny appearance. After coating, I didn't hear any negative effects from the treatment. But, I don't have test equipment to measure for differences, so I have to just trust my ears.
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David, do the finished drivers resemble the prototypes, or do they look more like standard AR drivers?
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On 8/21/2021 at 8:59 PM, NJtechguy said:
Hi All,
I'm a noob to recapping crossovers, but I am very good with a soldering iron. I have acquired my dad's old set of AR90s that I have loved since I was a kid. I refoamed the surrounds and now I realize I need to recap the crossovers.
Can you provide me with the ideal parts/values list of your recommended quality caps, etc and where I can buy them from? I've seen entire kits online but I read these are more generic parts. If I'm gonna recap these, I want to do it right and do it once. Thanks in advance!
Our AR90s have 8 capacitors. The series capacitors (directly in-line with the drivers) are 4.0 and 6.0 (for the tweeter), 24.0 (for the upper dome mid) and 80.0uF (for the lower midrange). The parallel/shunt capacitors are 8.0, 30.0, 40.0, and 350.0uF.
The 90s originally used all non polarized electrolytic capacitors. New NPEs are still available. Film capacitors can be used too. Match the uF rating as closely as possible. Voltages on the replacement capacitors can be higher, without issue.
I shop for capacitors at the following sites: Madisound, Parts Connexion, and Parts Express. All 3 companies sell the M.D.L. brand of NPE. So, it's easy to match like for like, at these sites. A good thing too, as you might not find the exact values at any one site. As such, you'll probably need to wire 2 caps in parallel, to add to the needed value, i.e. a 200uF and a 150uF, for the 350uF bass shunt.
Personally, I use polypropylene film capacitors for the series caps, and NPE for the shunt capacitors. I find this improves the sound, while helping to save money by using NPE shunts. All poly is fine, if budget allows, and all NPE is fine, in order to match the original design.
If the idea of using poly caps is interesting, check out the Humble HomeMade Capacitor Test. The site has tested and reviewed many brands of capacitors; both poly and NPE. An interesting read. Me, I used Mundorf EVO Oil caps, on my 90s, for the series caps. Axon, for the shunts. While my 90s are still a work in progress (no comments), listening tests showed the poly upgrade made a notable difference in sound. Oh, I've also used ClarityCaps, and like those too. Mundorf for transparency or ClarityCaps for warmth, depending on taste. IMO.
'Luck...!
Oh yea, Parts Express has a new capacitor chart. It shows all the available cap values and links to prices.
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The AR58S crossover was simplified, compared to the 91, with the elimination of the level switches. Otherwise, it's not a simple 6dB first order crossover. Both can sound great, if correctly designed.
Regardless, good luck with the 58S speakers, and the crossover swap. That should be fun. 😃
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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.
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The AR90 manual showed response graphs from different room positions. While not always optimal, none of the graphs looked horrid. Before I gave up on AR9s, I'd have to try every possible spot first. Plus, nothing new, in an affordable range, is going to compete with the 9s.
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12 hours ago, cd0nc said:
Was my understand they had different amounts of ferrofluid in? So you could use a 92/925 in a 90/9 but not vice versa.
Exactly correct.
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32 minutes ago, lance G said:
Stimpy, interesting to see (item 7?) that the high range driver is 200029-1. Is that not the same as the AR9/AR90 (ferrofluid ?) drivers ?
Probably not the right thing to do, but there is a potential to harvest these from 925's to keep the AR9/90's alive ?
Yes, the 925s use the same tweeters as the 9s and 90s. The 200032 mid could also be used for 9/90s, too. So while 925s could be used as donor boxes, I'd hate to do that, as the 92/925 variants are worthy as well. But, as you say, if the sacrifice is necessary "to keep the AR9/90's alive", I suppose it's a necessary evil.
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I just found the 925 drawing, and it's midrange is also 200032.
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The AR91, AR92, AR915, and AR925 could all use the same dome midrange. The 91/92 part number is 200032. The dome midrange, from an AR58S would also work, but the color of the dome trim and frame is different. The domes from AR9s and 90s shouldn't be used, as they have a higher resonance frequency.
Good luck.
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Yes, Falcon Acoustics is a great source, for capacitors, in the UK. They offer Alcap electrolytic caps, and ClarityCap and Solen poly capacitors. All good.
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I believe I see Black/Red Callins capacitors on your crossovers. Not good. They tend to drift out of spec, and leak as well. You should consider replacing them. Otherwise, Nice Job...!
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4 hours ago, Rickyboy said:
g`morning pals , this is my first post here , regarding the tweeter and mid range felt / foam , what are these made of ?? i am about to purchase a set of AR9 ,those parts were removed and since i have never seen another AR9 set before , i don`t know anything about what materials these inserts would be made of ..... i can still see the velcro round pieces on the speakers tho .....any help ?
thank you !!!
The tweeter and midrange inserts were a fairly stiff open cell foam. It was very different in feel to the felt acoustic blanket. Harder and more plastic in nature, compared to the blanket. Some use A/C filter foam, to cut inserts from, but the AR inserts were thicker and stiffer. Still, you use what you can.
Acoustically, I doubt the inserts do much. They are more for cosmetics. The acoustic blanket alone, most likely has the biggest audio impact.
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I purchased my AR90s factory direct, around 1980, through the employee purchase program. Both the UMR drivers and the tweeters had the foam inserts. All pieces still show no deterioration and are in great shape.
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I used to run my AR90s on a NAD 3140 integrated amp. With it's the ability to double power into 4 Ohms, and the NAD Soft Clipping circuit, it worked fine, for my modest needs.
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5 hours ago, Jose said:
Thank you very much Stimpy. I didn't know about the front wiring of the 4xa tweeter. Not sure if the 4xa tweeter includes the magnetic cooling fluid of the more modern 18b tweeter.
I bought the ebay tweeters you mentioned, thanks a lot for the hint. The cost for shipment ($135) to Germany and customs ($70), is quite high but ...
Even if they would have lost with time some of the original brightness I guess they will sound more like AR designed the 93 to sound than the strange ones currently mounted in the cabinets.
I will give feedback about the sound quality after refoaming, recapping and mounting the new tweeters.
The sock covering material needs also to be replaced for both speakers, and also the wood covers on top need some cosmetic treatmemt. One of the plastic basements has a broken corner, I'm thinking about replacing it with a base made of wood with same dimensions. I don't think this will influence sound.
One of the wiring connectors in the base has the clamping parts missing. I am thinking about replacing both with a better connector interface. Not sure which one, do you have any recommendarions for this interface?
Hi Jose,
I'm glad the tweeters worked out for you! But, I'm truly sorry to hear that the transaction was so expensive. It makes it difficult to be a music lover. The new AR18 tweeters should be soft and sweet in balance. Not bright at all. Though, I'd still keep your now spare Philips tweeters, in case you ever need a temporary replacement.
As to binding posts, Parts Express used to sell a drop in replacement for your speaker, with banana jacks instead of spring clips. Now, I no longer see it on their site. So, maybe check with Falcon Acoustics. They're are a UK based loudspeaker parts company. Maybe it'll be cheaper to buy through them?
Good luck.
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Here's the AR90 crossover schematic. You should be able to identify the resistors from it. Also, I like Chris's idea of cleaning the switches. It can't hurt.
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The "0" position is a straight connection, through the switches. The -3 and -6 positions engage resistors. Some of those resistors failed in my 90s, and had to be replaced. You might be having the same issue.
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I'm not sure about how easily the 4xa tweeters would be to use, as they're front wired. But, there is a new old stock pair of AR18 tweeters on eBay US. The seller advertises shipping to Germany.
Good luck.
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3 hours ago, Chris1this1 said:
Stimpy,
That is a really interesting observation about the new NPE's not sounding as good as the originals. So I was going to add a non-invasive switch to enable or disable the LSi mod, but now I'll add another switch, to switch between the series NPE's or series poly's. Both switches will be added to the connection cutout, over the input binding posts. I'll measure the values of the original caps when this work happens, and if they are still within tolerance, i'll leave the Unicons in place, and just have the pollys as switched option B.
Hi Chris,
Those switch ideas sound like a good plan. An extremely easy way to perform instant A/B comparisons. I'll definitely look forward to your impressions once implemented.
As to my NPE adventures, I tried Bennic and M.D.L. While they sounded fine, they seemed compressed in nature. It was like the speakers had lost their dynamics. Which I really disliked. As a test, and since I was already using Mundorf poly caps on my 90's, I bought ClarityCaps for the 58's. Clarity CSA's the the 4uF tweeter cap, and a 24 for the dome mid. I left the NPE's on the parallel stunts.
One of the reasons I tried the ClarityCaps, was they exhibit a higher ESR than is typical for a poly. Closer to a NPE. I figured the driver balance would stay similar to stock that way.
The ClarityCaps have been great. Warm and musical, with a wide soundstage. The Mundorf EVO Oils Ive used, are very transparent, clean and clear. They present better soundstage depth, and presence. Both brands very good, depending on the flavor you want?
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2 hours ago, DeSelbyofDalkey said:
It would have been easy to have my rebuild drag out over days and months as Stimpy is experiencing. I waited months for a solid block of free time to do it and get it done.
It was a series of events, that lead to my downfall...!
First, I wanted to move back to a 2 channel set up, to better support my soon to be completed 90's. That meant no longer using my Yamaha AVR, and hooking up separates again.
So, off I went to grab an amp from my equipment closet. I hooked it up, and hum? I try another amp, and hum again! A 3rd and final amp, and still hum. I could only assume that either my once new amps were now too vintage (like me) to use, or I was getting ground loop hum from the incoming cable.
Next, I found a recapped amp, to test the vintage theory. I picked up a Mosfet based Adcom GFA-5400. It sounded great, with an old NAD pre, which prompted a search for a new preamp, to compliment it. As such, I bought a used Schiit Saga remote controlled tube pre. If mated very well with the Adcom.
Now, my downfall. When searching CL, looking around for these new to me pieces, I spotted a pair of AR58S speakers. They'd been refoamed, and looked very presentable. Cheap as well. So off I went, grabbed the 58's, and hooked them to the Saga/Adcom combo. Epically good. And I liked the Saga so much, I picked up a used Schiit Bifrost Multibit DAC, to complete the new system.
Well, the new system has sounded particularly awesome. Good enough, that I kind'a lost interest in finishing the 90's. I'm feeling guilty now, for letting them sit this long, and the 90's are now the next project up for completion. I promise...!
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2 hours ago, lance G said:
Crikey Stimpy !
I thought you had finished them ! I was grateful for your input and help with the crossover rebuild on my AR9's. They might be due another rebuild by the time you finish those 90's !
I used to have some 90's years ago, regretted selling them, hence my eventual bucket list purchase of the 9's.
Kind regards to you.
Yes, I know. Too slow. The 90s have been refoamed, the crossovers recapped, and the cabinets stripped for refinishing. But, that's where I'm stuck. I'm good at electrical and mechanical, and not so good at furniture refinishing. I'm still doing that part. One day soon, I'll do it, as I'm getting impatient to finish. Now that I'm at that point, I know it'll get done. Thankfully.
AR90 Phase Anamoly - When it makes a difference
in Acoustic Research
Posted
I've asked before about the AR90s internal wiring, and if I should wire the woofers in phase with the upper drivers? Wired like the 9s, since my 90s never exhibited great bass performance. I'd love to know the reasoning between the 9s and 90s, and why they're wired differently?
Also, I've had the same phase issues with my 90s too, when using them for HT duty. My Yamaha RX-A3030 AVR, which uses YPAO set up software, identified phase issues with the speakers. I let the AVR correct the phase problem, and bass response greatly improved.