Watkins woofer white paper

Discussion in 'Infinity Loudspeakers' started by geoff727, Jan 18, 2010.

  1. jimreeves

    jimreeves Poopy & Me Subscriber

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    Here are a couple pictures of one of my 9021180's during the refoam
    [​IMG]
     

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  2. totem

    totem AK Subscriber Subscriber

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    Nice to see you on AK, I was wondering if you would show up at some time.

    I found your Emails on the Watkins info interesting.
     
  3. Ken Boyd

    Ken Boyd AK Subscriber Subscriber

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    This is the model that I beleive was not manufactor by Watkins. I am not sure as to this, but this is the model that I have in my QLS-1's
     
  4. cdfac

    cdfac AK Subscriber Subscriber

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    here's one of what i'd thought was one of the original Watkins:

    [​IMG]
    [​IMG]
    [​IMG]

    and here's a brand new one just for giggles:

    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: Jan 27, 2010
  5. Ken Boyd

    Ken Boyd AK Subscriber Subscriber

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    With the foam removed and applying the 30 hz test tone didn't your cone center in the motor. If you first glue your foam onto the cone and then apply the test tone to center the voice coil I would have thought all you had to do is glue the outside of the foam where ever it fall on the basket. That is the way I thought it was suppose to be done. If the test tone centers the voice coil and you have the foam already glued to the cone where ever it centers out is where you glue the outside ring of the foam to the basket. I don't think any of my foams ended up perfectly center in the basket, they all fell somewhere off center, but when you glue the big gasket around the outside you can't tell its not perfectly centered in the basket.
     
  6. cdfac

    cdfac AK Subscriber Subscriber

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    i think that's what he did. he's just saying that when he glued the foam to the basket, it was off-center because the spider's off-center (w.r.t. the basket).
     
  7. Ken Boyd

    Ken Boyd AK Subscriber Subscriber

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    Ok the ones I was describing are the ones in the bottom pic. That sticker says Watkins DVC so I don't know why he seemed so unsure of that model when I stated the magnet was not painted black and larger than the other ones I have. The majority of the ones I have are like the first pics the smaller magnet and they are painted black. The silver ones I have don't have that sticker that says Watkins but instead just has a printed on part number the 902-1180 which is the part number that is listed on the Infinity's website for every model QLS.
     
  8. jimreeves

    jimreeves Poopy & Me Subscriber

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    Best photos I've seen of the new Watkins DD Chris, thanks for those. Just eyeballin it, it looks like the surround has a bigger roll than any others I've seen. Makes me wonder whether the voicecoil is deeper and if it excurds further. Nice to see the vent there too since the dustcap is poly.
     
    Last edited: Jan 27, 2010
  9. Army

    Army Addicted Member

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    Hi Jim
    No I don't know of anyone with a copy that has posted it yet, but we're getting some good posts and information in this thread so I made it a sticky and hope Vito or someone may post the white copy in the future. To my knowledge it isn't posted in the database either.
    Scott
     
  10. jimreeves

    jimreeves Poopy & Me Subscriber

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    I didn't explain it well. The cone/bobbin assembly was glued off-kilter in the spider, so the rim of the cone was off-kilter with the basket rim. As soon as I glued the outer surround down I had to shift the surround/cone assembly on the basket to stop the rub. Had to fiddle with it 'til the glue tacked up well in order to keep it aligned in spite of the 30hz tone.
    On the plus side the spiders seem to be in great shape, no sag whatsoever. And they're playing sweetly now.:music:

    Thanks for your efforts Army!:thmbsp:

    Jim
     
  11. Ken Boyd

    Ken Boyd AK Subscriber Subscriber

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    Back in 2007 a member of Audiokarma stated he had the white paper and said he was going to post it, I read the entire thread and I don't see where he posted it. I contacted him and left him a message to see if he still had it so he could provide it. In the post Vitopanch claimed to have it and Ken C and Army all were part of that thread requesting it, don't see where he ever provided it to them.

    Here is a pretty good PDF from Infinity providing some pretty indepth info on the DVC drive It seems like it was part of the Rennisance 90's Technical Summary. By the sounds of it the Watkins driver int eh Renaissance 90 was a really good one, Aluminum baskets and a special driver cone material better than all the others, part of the years of evolutionary inprovements?


    http://www.davidsaudio.com/Infinity_Renaissance_Technical_Summary0001.pdf
     
  12. Ken Boyd

    Ken Boyd AK Subscriber Subscriber

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    Only thing bad is that they were 10 inch drivers.
     
  13. Nikkoholic

    Nikkoholic Active Member

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    Resulting in a weak bass, if I may add.
     
  14. Ken Boyd

    Ken Boyd AK Subscriber Subscriber

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    I must say you have quite a line up of nice Infinity systems.
     
  15. Nikkoholic

    Nikkoholic Active Member

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    Thanks, right back at you! Never heard the RS1, sure would like to though.
     
  16. rustnrot

    rustnrot AK Subscriber Subscriber

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    New Loudspeaker With Extended Bass by Bill Watkins Dec. 1974

    I think this is the elusive "Bill Watkins White Paper" you all have been seeking. I was browsing this forum and ran across this thread, and sure enough, I checked and I had this hardcopy so I scanned it. Note it says "Reprinted from the December 1974 Issue of Audio, The Authoritative Magazine About High Fidelity" on the last page.

    I'm sure I must have picked it up at Watkins Stereo circa 1977 in Kingsport, TN while a friend was buying a stereo system from Bill himself that, as I recall, consisted of a Pioneer receiver and a pair of Watkins Dual Drive speakers. This was prior to his association with Infinity, but not much prior as I think he was associated with them a couple years later.

    I was attending the Univ. of Tenn. in Knoxville at the time getting an electrical engineer degree. While fascinated with Watkin's speakers, many of us went home that summer and built our own acoustic suspension speakers using Peerless drivers. I remember winding my own chokes for the crossover since you really couldn't buy them readily, not like now.

    I have higher res. copies of this that I can send to make a proper pdf of this. The uploader here has reduced the resolution to fit.
     

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  17. cdfac

    cdfac AK Subscriber Subscriber

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    great, wonderful!

    the only part that still confuses me is the choice of the LC circuit that's in series with the main coil. for the RS4.5, that's the 12.5/8mH and 300/450uF components. it's important to know what's going on here if one wants to make make the 4.5 woofers as actively crossed over as possible. rough calculations show that in biamp mode, the upper coil is rolled off at ~200Hz at 12dB/octave. it's no problem to snip out the 75uF shunt cap, but if the series LC circuit is important for the Watkins function, then you can't just omit that inductor, which will leave a 6dB/octave rolloff in the circuit. any thoughts from the EE's among us?
     
  18. bharper

    bharper tube junkie...

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    you have two seperate lc circuits there.... one is for the actual rolloff, the second is to get rid of a natural peak in the driver/cabinet. My understanding is when these are tuned correctly, that there is a fairly nice, flat impedance curve, but I also heard these were further tweaked by infiinity(read arnie), causing some nasty impedance dips.

    I had some fairly trashed walsh speakers in my 4.5's, and instead of messing with them, I put in a pair of infinity beta woofers, both wired directly to terminals on the back of the speaker without using any of the existing crossover for them. I then use an ashley xr2001 electronic crossover, and found 300hz seems to work best for me.

    I probably could use some eq on the bottom end, but as of yet have not bothered, it sounds a lot better than the old stock crossover did. the top end is much more detailed and just sounds so much better with the ashley, and I am I guess running 24db slopes. If you play the bass by itself, it really sounds bad, because when it hits the crossover point, it just stops like it hit a brick wall. With the tops driven, they blend quite well.
     
  19. kmanusa

    kmanusa AK Subscriber Subscriber

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    Impedance measurements that I made of my RS4.5s did not result in a flat impedance curve in either speaker. As I recall in a post on one of the rec.audio newsgroups years ago, Bill Watkins said that Infinity made changes to the Watkins woofer design in the 4.5 that extended the deep bass but introduced substantial impedance variations in the low frequencies.

    I made some PSPICE simulations of the 4.5 crossover substituting 2 and 4 ohm resistors for the woofer coils. The resulting impedance curve was anything but flat and looked a lot like what I measured in my speakers.
     
    Last edited: Apr 20, 2010
  20. jimreeves

    jimreeves Poopy & Me Subscriber

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    I've never heard the 4.5's but have to wonder, are the emims and emits in the 4.5's so much more efficient that two watkins were needed to increase output, or do they perform a Quad-Drive function? They seem furthest from the original watkins design than any of the others to this layman. Was Arnie noodling with these?
     
    Last edited: Apr 20, 2010

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