Jump to content
The Classic Speaker Pages Discussion Forums

valkyrie

Members
  • Content Count

    37
  • Joined

  • Last visited

Community Reputation

0 Neutral

About valkyrie

  • Rank
    Member

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. The Hi-Vi fits perfectly - which is why so many people use it. I was asking about the Midwest drivers NOT the ABTech (which I think no longer exist) or the Hi-Vi. From what I have read the Hi-Vi is a good mechanical fit but not so much of a sonic match - requiring extra parts in the network to tame it for use in the AR speaker systems. Even then some have complained of it being a bit "bright" - running hotter than the OEM tweeters.
  2. Frank - I differ with you in regards the sonic limitations and ability of the original AR tweeters - AR-3 era devices. Those were fine drivers - very wide dispersion and well extended past the human audio spectrum. They were prone to burning up when they were fed either too much power OR were fed defective power from the limited amps of the era. In normal use those drivers work well. The later model ADD tweeters were superb units - ferro-fluid cooled, extended and again very dispersive. EQ devices can only affect the on-axis sound - the dispersive field - the "sound power" is NOT affected by any EQ. Thus EQ doesn't really work at all. See Floyd Toole for more information on this topic. As for MC carts? Really? You seem to like a rising high end. I don't care for MC - they are all AT LEAST 10 dB NOISIER than an equivalent MM cart, all track very poorly, they have problems with very low compliance and they require an extra 20 dB of amplification - amplifiers boost noise as well as signal. MC to myself is more about being "fashionable" than it is anything else.
  3. Frank Marsi - I suggest that you are confusing the Hi-Vi tweeter with this particular model. The Hi-Vi does need some trim parts in its network to render it usable with the AR speaker systems. Thus far I have no information - but THANKS DavidR for your review of same. Thanks Mez for your insight about the face plate being plastic. I think the magnet and voice coil are identical to the originals.
  4. Went to this site; https://www.simplyspeakers.com/acoustic-research-replacement-tweeter-12000840.html And these folks have IN STOCK replacement 3/4" tweeters - domes - for the AR-9 family ($79 per unit - very competitive with the old units offered on the 'bay). Also they carry IN STOCK the 8" mid-bass coupler for the AR-9, as well as the 1/5" dome midrange driver. Given that the drivers in my AR-9 must be getting "tired" I have to wonder if these drivers are actually OEM style replacements. Or are they merely Chinese "knock offs" - similar shape, correct mounting plate but bearing no particular sonic equivalence to the original domes? Does anybody have any experience with these drivers? Anybody measured their F/R? Inquiring minds want to know. Thanks.
  5. All I know about film caps is that they differ by orders of magnitude in price. You can buy a 24 uF cap for $6 or $600 - guess which one I bought? I do "believe" that Mundorf makes an exceptional capacitor. Based on actual use and the reports of others. But - and it is a big butt - I am not sure which cap I used in the UMR series feed. It may have been a Jantzen, it may have been a Solen. It was film - and that is what I was told to seek out. I did NOT use a bypass. I do plan on going back into the speaker - which means humping its 132 pounds up on my work bench - always a joy!!! I lean it against the bench and then lift the bottom up. Ugh!!!! So tell me about this "Clarity CSA". Is it an electrolytic bipolar? Or is it film? The fellow who first determined the problem with the UMR series cap - I think it was AR_Surround - felt that the Mundorf electrolytic bipolar provided the smoothest response - with a film bypass. Since it is not too expensive that is the direction I am headed. Good luck with your endeavors - when I recapped my Mighty Nine it became a completely different speaker - quite delightful. Sounds superb - better bass than a $60,000 Wilson (Strauss "Thus Spake Zarathustra" has a genuine low C organ tone - 32 Hz and the Wilson bass drivers jumped the gap on that note) - great clarity and superb dynamics. To my ears a truly wonderful speaker. You are fortunate to have such a speaker. I am never going to part with mine.
  6. One other comment. When I rebuilt the crossover of the Mighty Nine I replaced all caps with decent (Erse, Jantzen, et cetera) film caps. MISTAKE. The upper midrange driver does NOT like having a film cap (24 uF) in its series feed. I think AR_Surround was the fellow who first unraveled this mystery. Placing a film cap in that circuit caused harshness, bite, congealing and grit in the playback of music. While I haven't gone into the speaker to install the suggested Mundorf electrolytic I can say that the performance I have now is EXACTLY as AR_Surround noted - gritty, harsh and filled with hash at about 7 to 8 KHz. I expect that installing the recommended Mundorf cap will fix that problem. Also - see if you can replace the attenuator bank slide switches with toggle switches similar to what the AR-91 employs. Much better switch. The slide switches are hunks of crap - they collect dust and grit and tend to fail.
  7. Concerning the bass portion of the AR-9 crossover. I suggest removing the 2500 uF cap - but NOT the 470 uF cap shunt to ground. The 470 is a critical part of the 200 Hz low pass filter. The 2500 uF cap was placed there to raise the impedance at resonance - otherwise the two 12" woofers are effectively in parallel with an impedance of about 2.8 ohms. An amp killer - particularly in the world of 1979. So if you do remove the 2500 uF cap make sure you have a modern solid state amp - no tubes need apply - that can handle low impedance loads. I have found two amps that are comfortable with that load; Odyssey Audio Khartagos and Pass XS150.5. I am relatively certain that ANY Pass amp in his XS or XA models would work well with that kind of load. There may well be other solid state amps that can handle such a load - but DO NOT try to drive the modified Nine with any "vintage" receiver - the result will be smoke, possibly flames and a dead receiver. Nor try to use an H/T receiver - those things are at best rather flimsy in terms of actual power capability. I have noted on my Pass amp, which has a bias meter on front that when I play heavy bass tracks that the needle swings in time with the music. This means that the amp is coming out of pure Class A (about 16 watts maximum) and entering class A/B territory (300 watts into a 4 ohm load - actually about 10% more is typical Pass amp performance). The bias is really increasing. But the amp handles it with aplomb. I have measured results of this modification - F/R plots - and posted them somewhere on the CSP - I think my results were moved to the "tweaks and modifications" section of the CSP. I angered a few of the purists and know-it-all types by suggesting the modification. How dare a mere peasant such as myself suggest such heresy as modifying the work of AR? The response of the enlightened and insightful ones was to bury my comments and measurements in a part of the forum rarely traveled. Oh well - males being males. Competition and all that. The sonic results of the modification? Much tighter, deeper and tauter bass response. As I recall the modification resulted in about a 10 Hz increase in usable bass down to about 25 Hz and a subjective sense of more bass across the band from about 80 Hz on down. Try it. You may well enjoy the response. One other thing to check for - the 8" midbass coupler is in a "can" so it can employ air suspension. That can was mounted to the front baffle of the Nine with a glue that has hardened and cracked over the intervening 38 years. You should remount that can, which is made of thick cardboard and a thin piece of plywood on the rear, to the front baffle. I used RTV as my glue and installed a brace between the rear of the can and the rear of the speaker. Screwed in at both ends. Keep that "can" airtight and get the original performance of the critical driver.
  8. I have heard a LOT of modern gear - I go to RMAF - and hear many items - both expensive and "budget". Of course "budget" in this era is actually ridiculously priced. Though at any audio show one does not hear much that is < $3,000 - for anything. I digress. Considering the sonic quality ALONE of what you get with a well chosen "vintage" system compared to what you get with some "modern" gear the prospective buyer is actually getting a much better deal for his/her dollar. The draw back of vintage stuff is that it may break or deteriorate even faster. The stuff is 40 to 50 years old. I put together a set of AR-91s, ($600) and a Marantz 2252 ($350) - so for $950 I had an excellent system. Try to match that with ANY modern gear. Cannot do it. The last modern rig I assembled was a set of Pioneer PS-22 two ways, a Yammy receiver and the total cost was about $800 - and it cannot touch the Marantz/AR rig - in tone, bass range, musicality or dynamics. Not even close.
  9. The low C on a pipe organ is 32 Hz. Most speakers, including a $50,000 Wilson Audio behemoth, will NOT handle a low C. In fact I have found that the great majority of speakers rated as -3dB at 35 Hz have actually folded their sonic tents around 50 Hz and quietly gone home. In addition with symphonic music there is an effect that I refer to as "hall lift", wherein the cavernous space in which the music is played seems to underscore the music with a low frequency quality. Very low. Then there is electronic music - see Zach Hemsey recordings for more information. Regardless - it is my stereo, I tune and play it THE WAY I ENJOY IT - and what you "think" is "right" is of no possible concern to myself. If you want to leave in a tribute to ineffective engineering and semiconductor capability from 1979, e.g. the 2500 uF cap? Then please be my guest. Your tunes - hear them as you wish. This is a forum for the expression and discussion of ideas - not a political indoctrination center wherein we all must follow the "one and true path". I got rid of that silly cap - good riddance. YMMV.
  10. Holl - the chief designer of the AR-9 clearly stated that the addition of the 2500 uF cap in the LF crossover was to allow a sufficient impedance at resonance so that the combination of TWO 12" woofers would not be a threat to the amplifiers of the time - circa 1979. What happens is that the big cap allows the reactive capacitance to form an effective DC resistance that adds to that of the 2 woofers in parallel - which is < 2 ohms. Somewhere on this forum are some notes from Holl that describe his engineering perspective on using the two woofers in the AR-9. He clearly AND UNEQUIVOCALLY STATES THAT THE PURPOSE OF THE LARGE CAP IS TO ALLOW SOME PROTECTION TO AMPLIFIERS BY PROVIDING MORE RESISTANCE. Modern high quality amplifiers - solid state that is - can easily handle a 2 ohm load without incurring any damage. Pass amps and Odyssey Audio amps have no problem with a < 2 ohm load. I am sure there are other amps equally capable - but the two listed I know for sure have no problem with such a load. The gain? Better low end response - your system will have more power in the 25 Hz region, and more power in everything above that range up to about 60 Hz. Above that there is not an noticeable difference. Find my earlier posts on this issue which include before and after F/R plots. I think those posts were moved to some obscure portion of the forum - perhaps the "modification" listings - because the "powers that be" did not like my approach. From their perspective any modification of the sacrosanct original AR configuration is a grievous sin that must be punished with all haste. How dare that some simple peasant such as myself, clearly not a member of the rarefied cognoscenti, dare to modify any AR for any reason. These folks will also tell you to not change the wire in the internal loom - even though it is a pile of decrepit junk. Change the wire - the factory wire was grossly under specified. Use a lower gauge - say 14 - and double runs on the woofer feeds. Solder all your connections - even to the drivers. Do NOT use the junky spade clips from AR - they were there merely to facilitate production. Make sure your LMR "can" is still attached to the cabinet face - they factory used a crummy glue which has long since hardened, cracked and come loose. That is critical to good sound from the Mighty Nine. AR designed and built wonderful speakers - they can be improved. Even after 40+ years.
  11. The LF crossover board is removable - the HF section is not. Best to do the HF board "in place". Read AR-Pro's comments in regards the type of capacitor that should be used in the UMR and tweeter crossover. I have found that those capacitors should NOT be film - but instead a Mundorf NPE - the film caps seem to cause a quality of shrillness and gritty sound to recordings of instruments such as massed violins hitting high notes. Glue your new caps in place with silicon sealer - works better than the original glue. You might want to reorient your coils on the LF board so that they are at right angles to each other - thus reducing cross coupling between the coils - except for the one inductor which is a stacked unit. Also - if you have a high quality modern amplifier there is NO NEED TO USE THE 2500 uF cap in the LF crossover. That is was put in place by Holl to prevent the really low impedance of two AR 12" woofers in parallel, < 2 ohms, from causing a typical 1979 style amp to blow up from attempting to source too much current. Modern amplifiers - NOT RECEIVERS - can easily handle a < 2 ohm load. Pass amps will do so, as will product from Odyssey Audio. No doubt there are other solid state amps that can handle such low load impedance. I have used both those amps with an AR-9 that did not have the 2500 uF cap in place and had no problems at all. I have an article on this forum - carefully moved from this section by the "powers that be" - that show an F/R plot of the before and after results of not using the 2500 uF cap - you will get more lower bass without that cap in circuit.
  12. As noted - people buy old, old, old AR speakers because they sound so good - even now 30 to 40 years after they were manufactured. Darn good sounding speaker to my ears.
  13. THE BEST all around AR speaker? Of course that has to be the AR-91. Think of an AR-3 that was truly improved - better midrange and treble. Smooth, still somewhat smallish - can be used on a "STURDY" bookshelf. Deep bass. Best general purpose speaker they ever built. Of course the absolute best AR? That has to be the Mighty Nine - puts all others into the shade. Including the LST.
  14. Ra.ra - thank you for your help. And the link!!! AR_Pro - I plan on using the "holes" that the slide switches currently (no pun intended) occupy on the Nine attenuation control panel. Not sure - I may have to do some mods to get the switches mounted correctly - airtight and all. I just like the feel of the switches on the 91 - and feel that the switches on the 9s are - at best - somewhat cheesy. I guess AR was trying to save a few bucks in production. I do want to save the original sand cast resistors on the 9 - why remake the wheel? I will post pictures when I am done. Thanks guys for your timely and helpful reply!!!
×
×
  • Create New...