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Pete B

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About Pete B

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

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  1. AR9 Teledyn Big LF Caps where?

    Electrolytic caps use very thin foil so that a lot of area can be packed into a small volume, this thin foil has fairly high resistance per inch. Normal electrolytics have a single attachment point for the connection terminals. The large can caps have many attachment points in order to reduce the resistance (ESR) and inductance (ESL) caused by the foil. We should try to compute the ESR of the group of caps at the important frequency. The 2500 uF resonates at about 28 Hz and we'd like the ESR to be (much) lower than the DC resistance of the inductor or roughly equal to the original cap. The 470 uF should have low ESR around 200 Hz where it is working in the crossover. Let me see if I can find some data on large can caps from that era.
  2. I'm afraid it has happened?

    I agree Tom, the upper chamber under the dome is vented, through the three slots to the air chamber where the back of the voice coil is.
  3. I'm afraid it has happened?

    Thanks Roy, yes I also had the other one of the pair apart some time after I made those measurements and saw those features.
  4. Capacitors Redux

    I measured a Collins cap here back in 2005, it was defective before reforming it: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1411-ar-11-collins-capacitance-increase-needs-reforming/
  5. Capacitors Redux

    An old thread: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1431-capacitor-myths/ Paul S. Barton (founder of PSB) on break in: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1431-capacitor-myths/&do=findComment&comment=63255 Tom Nousaine on break in: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1431-capacitor-myths/&do=findComment&comment=63254 I had links to Ken Kantor's comments on break in but most in that thread are broken due to one of the site updates. Here are Ken Kantor's comments, there were more but the links are broken: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/749-speaker-break-in-myth-or-fact/&do=findComment&comment=52320 Wish I could edit my own threads so that I can fix the links.
  6. I'm afraid it has happened?

    I measured an AR-11 tweeter back in 2005, it would be great to know Fs and the Q's for the new tweeter. Some measurements on an AR-11 tweeter (200011-1) are given below. Measured with LAUD. The input impedance curve showed a double bump which is common with chambered tweeters, has anyone had the dome off to see if the center pole is vented into the rear? The impedance peaks were heavily damped due to the ferro fluid. The lower frequency peak at 1360 Hz was 5.26 ohms, the minimum in between at 1865 Hz was 4.65 ohms, and the upper peak at 2427 Hz was 5.30 ohms. The tweeter was 4.0 ohms in the passband at 5 kHz. Here are the basic measurements based on only the input impedance, and assuming that the upper peak is the fundamental resonance: Fs = 2427 Hz Re = 3.55 Qe = 2.76 Qm = 1.57 Qt = 1.00
  7. AR9 Teledyn Big LF Caps where?

    People, when you buy from a surplus house you might find items that age well and are a good value or you might be buying junk. These caps, besides being polarized and designed for power supplies are very old and therefore worthless. They have date codes. note the 9717L marking on the first cap it was manufactured in the 17th week of 1997, next 9031L, you can figure it out 31st week of 1990, third cap, 17th week of 1981, last one 11th week of 1991. They belong in the garbage. You can buy modern high quality caps from the major suppliers, they are usually not non-polar but they can be wired back-to-back. Caps must be tested at rated voltage (or slightly above) for leakage basic tests are not enough.
  8. AR9 Teledyn Big LF Caps where?

    People, when you buy from a surplus house you might find items that age well and are a good value or you might be buying junk. These caps, besides being polarized and designed for power supplies are very old and therefore worthless. They have date codes. note the 9717L marking on the first cap it was manufactured in the 17th week of 1997, next 9031L, you can figure it out 31st week of 1990, third cap, 17th week of 1981, last one 11th week of 1991. They belong in the garbage. You can buy modern high quality caps from the major suppliers, they are usually not non-polar but they can be wired back-to-back.
  9. Capacitors Redux

    I say always recap small value NPEs because their chemistry is such that they do not last reliably past 10 or 20 years. You need to test them at voltage, not just small signal. This is undisputed in the electronics industry, sure your equipment might work even at 30 or 40 years old but you are taking a huge risk and it is probably NOT working optimally. Military specs are to only store electrolytic caps for 10 years max. More of my thoughts on this: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/9255-smaller-advent-woofer/&do=findComment&comment=115979 And how to properly test older caps at working voltage: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/9255-smaller-advent-woofer/&do=findComment&comment=116424 Old leaky caps will pass bass into tweeters and mids, they are a risk not worth taking. Subjective tests have to be done blind.
  10. Advent refoam (again)

    It is just plain wrong. The motor has about 1/8" linear Xmax, when you offset the cone in the wrong direction you take away from what little is already there.
  11. Info on The Advent/1 re-foam.

    I am the author of this page, FYI: http://baselaudiolab.com/ADVENT_LA_XO.html This is my collection: http://audiokarma.org/forums/index.php?threads/large-advent-collection-pete-basel.699453/
  12. Info on The Advent/1 re-foam.

    The square magnet version is the correct one, the round one was manufactured by Jensen after they bought Advent and is the correct woofer for the 5002/5012. They are very similar but the magnet geometry is different. I'd get a matching woofer if you don't mind spending a few bucks. There are several goals when doing a refoam: 1. Center the voice coil in the horizontal plane, luckily if you visually center the foam on the cone and put it back on the frame where the original one was it has worked every time. 2. Center the voice coil in the vertical plane, you want the VC centered in the gap for maximum motor strength. Install the foam the same way as the old foam was done. 1/16" makes a difference. Also, measure the distance from the edge of the frame to the old foams position and put the new foam at the same "level" on the frame. 3. The dust cap radiates some midrange and changing it will alter the frequency response of the woofer in the critical midrange. Do not cut and shim, keep the original dust cap. I and many, many others use Alene's Tacky glue available at Walmart and craft stores it just works very well giving you time to adjust if needed. How I do an Advent refoam: 1. Clean off the old foam and glue - for years I did this with the tip of a flat blade screw driver but I found that the tiny wire brush on a Dremel tool works great, Gently at a slow speed. Face the woofer down on a flat work surface if you need to get to the back of the cone or work from the front if possible. 2. Put rolled up plastic shopping bags in the back between the frame and the cone to lift it up for easier access. Anything will work, crumpled up newspaper, etc. 3. Squirt some glue into a bottle cap and use a tiny paint brush or Q-tip to apply glue to the inner lip of the foam, once I go around it usually soaks in: 4. Apply another light coat. Then press it against the cone. If you want to move more slowly you can apply say 2" of the second coat press that section to the cone, another 2" press, and work your way around. Stay with it after you finish and apply pressure until it sets up - let it dry for a few hours or over night. 5. Apply glue to the outer lip one coat, then remove the plastic bags and let the cone drop now lift the edge and apply a second light coat of glue and align/press the foam according to the old glue line and/or your measurements. Try to move fast so that the glue does not fully setup. 6. Apply even pressure to the cone with your thumb and finger tips to both sides of the cone and push it in about 1/4", does it move without scraping? Rotate 90 degrees and try again, if it is not free you need to adjust the lip of the foam for better centering. Press on just one side to figure out which side needs to move in or out while the glue is still not fully dry. 7. Some drive the woofer with a very low frequency test tone to help center it but I've never had to do this with an Advent woofer.
  13. Carl Richard (Carlspeak) RIP 11-11-2017

    I think that Carl called his upgrade the Super AR-3a or something like that. Does anyone have a pair? I'd like to hear from people who bought them. He also designed the "Intimates" that were shown at RMAF by Madisound and Carl had hoped that Madisound would offer them as a kit. I'm thinking of contacting them to see if they'd like to do it in his memory. I'd also like to hear from anyone who bought or built his Intimates.
  14. KLH 5 fatal design flaw

    Do any KLH 5 listeners find that the midrange is transparent in a way similar to headphone listening? I have never heard them.
  15. I am just giving you a hard time and I want to get rid of this boat anchor. It IS KLH says it right on it.
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