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Pete B

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About Pete B

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    Connecticut, NE USA
  • Interests
    Interest in Audio for over 30 years, got started early
    Electrical Engineer (see my web site link)

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  1. Found it, see Figure 6 in this document: http://www.troelsgravesen.dk/BOOKSHELF-1/RoyAllison.pdf Figure 6 does not look very good unless you are using it as a subwoofer, note the much better response in Figure 9. Also note that infinite walls are assumed since the paper is about how the cone/box radiator interacts with reflections from the wall boundaries - think of the walls as acoustical mirrors. Room cavity resonance modes are not treated and are a different subject. Stumbled onto this interesting paper also: http://www.mariobon.com/Articoli_storici_AES/Toole/Loudspeakers_and_Rooms_Working_Together_Toole.pdf
  2. Allison's AES paper covered many different locations. There is also a program Best Place that should answer your question. http://www.classicspeakerpages.net/IP.Board/index.php?/topic/5186-allison-effect-and-bestplace-program/ Here is some discussion of Allison's AES work: http://techtalk.parts-express.com/forum/tech-talk-forum/25007-boundary-effects-on-loudspeaker-power-and-frequency-response Not sure if you can find them online in .pdf format, you can pay for them from the AES: The Influence of Room Boundaries on Loudspeaker Power Output Although it is well known that nearby boundaries affect the radiation angle (and thereby the power output) of small acoustic sources, loudspeaker systems generally have not been designed with due regard for these effects. Conventional loudspeakers oriented in typical use positions in living rooms exhibit variations of the order of 5 to 12 dB in low-frequency power output. The problem is examined quantitatively and some practical measures for improvement are suggested. Author: Allison, Roy F. Affiliation: Allison Acoustics Inc., Wayland, MA AES Convention: 48 (May 1974) Paper Number: 951 Permalink Publication Date: May 1, 1974 You can search for all of Allison's papers at the AES site: http://www.aes.org/e-lib/online/search.cfm The green AES "Speaker Anthology" includes 3 of Allison's papers: http://www.aes.org/publications/anthologies/downloads/jaes_loudspeaker-anthology-1.pdf
  3. Pete B

    200003 12 "woofer needs spyder

    I would say that your woofer was overdriven such that it smashed into the backplate and then went forward to hang on the top of the pole piece. I had one do the same thing but it was not charred. Here is a Small Advent woofer that I repaired, where the small amount of former that hits the back plate when overdriven folded inward so that it hit the pole piece. I folded it in the other direction up toward the windings where there it is then closer to the center of the gap. The first picture in this thread: http://audiokarma.org/forums/index.php?threads/small-advent-woofer-repair-some-measurements.819443/
  4. Pete B

    200003 12 "woofer needs spyder

    The former is straight - no bend or curve. On the other hand I do bend them in the direction of the coils when I do a repair like this. You are obviously capable of a very detailed repair, I would purchase the correct magnet wire and wind a new VC on aluminum. I've done it before for other woofers and it is easier than you might think. I use high temp epoxy to hold down the windings - lately I've used slow drying JB Weld since it is very high temp and available locally. Small sheets of thin aluminum are available at hobby stores in different thicknesses, not sure what the original was or the wire gauge.
  5. Pete B

    200003 12 "woofer needs spyder

    I give you credit for trying to fix that woofer! But the coils have moved up on the former probably as a result of being bashed into the back plate; there should only be about 1/16" or less of metal former "behind" the windings. That coil has gotten so hot that the wire insulation is charred. I had a few woofers that were charred like that and then eventually shorted, probably when the windings contacted each other. You really need a new voice coil but I'm not sure where to get the correct one these days. I would not use a non-metalic type because it really helps the thermal performance/power handling of the woofer. I posted pictures of a 200003 woofer voice coil with very minor damage here in the past but they were lost during one of the site updates. I'll try to find the files. Here are a few old threads about this woofer: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1408-ar-11-woofer-200003-measurement-refoam-repair/ http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1147-evolution-of-and-replacements-for-the-ar-1112-woofer/ I just found this thread that I had not noticed before: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/679-differences-in-the-ar-12-inch-woofer/
  6. Pete B

    Dynaco A25 vsDynaco A25 XL loudspeakers

    epinions site is dead, here is Horswisper's review from the wayback machine: Dynaco A-25XLs were a later version of the famous Dynaco A-25 loudspeaker. The XLs came out in 1975 or 1976, six or seven years after the original, and were said to be 3db more efficient than the original. They were also said to be a bit more extended in the high end, and to be able to handle more power overall. Visually, they resemble original Dynaco A-25s, with similar dimensions, real walnut veneered cabinets, and creme colored grilles, but the front edges are skinnier than those on original A-25s, meaning that someone who has had the originals can tell the newer speakers from the originals at a glance. Functionally, A-25XLs differ from the originals in that the tweeter level knob on the back has only three positions, not the five positions of original A-25s. Internally, the A-25XL woofer looks almost identical to the original, but it is more efficient, matching the efficiency of the newer, smaller tweeter. I am told that the crossover is also different from the original, but I didn't open these up. Dynaco A-25XLs measure just under 11.5" wide x 20" tall x 10" deep and weigh about 21 lbs each, one pound more than the original. Retail price in 1976 was about $180/pair, $20 more than original A-25s. Today, a pair of A-25XLs commands from $125 to $250 on eBay, depending on condition. I have refinished (and listened to) something like 50 pairs of Dynaco A-25s, as well as several pairs of A-10s and A-35s, but I somehow managed never to hear a pair of A-25XLs until recently, when I refinished a pair that was fully functional but aesthetically challenged. This review is of that pair of speakers. Set-up and Listening. Set up of Dynaco A-25XLs is a breeze, as the speakers are relatively light, compact, and easy to move about. Speaker wire attachment is by standard-spaced banana plugs (or bare wire if you prefer). I placed the XLs atop my Cambridge Soundworks Towers for some listening, and on 20" stands placed about 24" away from the wall for more critical listening. The sound of the A-25XLs was interesting, and notably different from that of the original A-25s. The extreme highs had more sparkle, and bass was if anything a touch tighter. The soundstage was also notably deep, with backing instruments presented well behind the plane of the speakers. But the A-25XLs didn't sound louder for the same setting on the volume control, as I had expected. As I listened to my usual assortment of music (Keith Jarrett Trio, Diana Krall, Gordon Lightfoot), my impression was that the midrange of the A-25XLs was recessed, probably leading to the sense of image depth mentioned above. Piano sounded both full and sparkly, but the upper midrange that gives piano its presence was missing. Same with male vocals: there was ample heft, and sibilants came through, but the clarity I'm used to was not there. Of course, I didn't get to measure the speakers, but my impression was that there was a broad valley in the midrange, sort of like an exaggerated "BBC dip." An audiophile friend who came to listen with me agreed: he thought the speakers lacked the midrange clarity of the original A-25s. However, their owner has since emailed me and said he is quite satisfied with their sound, so they will certainly appeal to some. I should say that the Dynaco A-25XLs did not sound bad to me--in fact, I was really impressed with the depth of their soundstage and their high frequency extension. And I would take them over many under-$200/pair speakers I hear today. But they didn't sound as good to me as regular Dynaco A-25s, KLH 6s, Acoustic Research AR-2axs, and several other comparably priced (today) vintage speakers. Conclusions. The A-25XLs were an interesting listen. When I first fired them up, I was impressed with the depth of the image, but then quickly noticed the "hole" in the midrange. I settled in and was able to enjoy them for awhile, but ultimately found myself glad to return to the regular Dynaco A-25s I had on hand for comparison. I should mention that it's possible that "capacitor drift" was responsible for the recessed midrange of these speakers. If crossover capacitors change in value as they age, they can make a speaker sound bright (see my review of the KLH 17s) or recessed, depending on which way they drift. This is the only pair of Dynaco A-25XLs I've heard, and I did not venture inside the speaker cabinets. In conclusion, the pair of A-25XLs I heard were good, but there are other speakers from the same era that I like better. A link to my review of original Dynaco A-25s can be found by Googling Dynaco A-25 Horswispr. The system used in this review consisted of the following: NAD 521BEE CD player, AR ES-1 turntable with Shure M97xE cartridge, conrad-johnson MF-80 power amplifier, NAD 1020 preamplifier, and an M&K V-2B subwoofer
  7. Pete B

    I Have AR-5's

    I always use high temp epoxy for that joint since most speakers I work on have metalic voice coil formers and there will be a LOT of heat there. I most recently used slow drying JB Weld since it is very high temp and strong glue, HD didn't have anyother high temp type of epoxy. I would use the old glue line as a guide for the height and the torn tab for rotation and shim the VC. Apply the epoxy with a toothpick or chopstick, or something similar working it into the joint then turn the woofer magnet up to try so that if it flows it does not go into the gap. I also suggest Aleene's Tacky Glue for the surrounds
  8. Bump for after the holidays and PRICE DROP!
  9. Yes, still available. Mostly dust and seems that from past cleaning the color is not perfectly uniform, there are no chips or dings in the cabinets. The bottoms have some discoloration were poster tack was used on smaller stands. I have original boxes but the QM10 did not include a manual at that time. Feel free to PM me if you are interested. I also have: Gloss Black #2 - A pair in gloss black from about the same time frame where they were http://www.classicspeakerpages.net/IP.Board/index.php?/topic/10188-fs-799-guru-qm10-speakers-2-gloss-black-new-open-box-blems-ct/ early production of the black paint and had a small amount of peeling that I had a friend touch up - his repair was not perfect but they look fine from 5 ft away. I was told by the importer that these were never played due to the paint issue. I tested them with music for an hour and they sound fine. Gloss Black #1 - A much later production gloss black pair that I opened from new for pictures and it is clear that they corrected any issues with the paint - they look fantastic. The QM10 s have all film caps in the crossover so should never need a recap.
  10. Bump for the holidays, open to offers.
  11. Bump for the holidays, open to offers.
  12. Bump for the holidays, open to offers.
  13. Pete B

    Restoring Powered Advents

    Thanks, are you doing the work yourself?