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Edgar

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Posts posted by Edgar

    Why No Bandpass Filtering on Woofers?

    in Technical/Restorations

    Posted

    When I was with Altec-Lansing, I worked on a design project for a device that automatically adjusted the signal going to a woofer, based upon the design of the enclosure, the woofer parameters, a thermal model of the voice coil circuit, the history of power input, and the frequency content of the signal. (I wish that I could remember the name of the product.) The intent was to allow maximum output from the woofer without damaging it. This was 1995, so it's not a new idea.

    • Like 1

    Why No Bandpass Filtering on Woofers?

    in Technical/Restorations

    Posted

    14 hours ago, Peter P. said:

    So why don't more manufacturers protect their woofers electrically with bandpass filters?

    Who is to decide the parameters of that bandpass filter -- cutoff frequency, filter order, filter type? Woofer excursion varies tremendously depending upon whether it's in a sealed, vented, horn, or other type of enclosure. Within each of those designs, excursion varies with enclosure size and alignment, horn design, number of drivers, and other factors. A "one size fits all" filter simply doesn't exist.

     

    As for high frequency rolloff, that's the job of the crossover network -- not needed or wanted on the woofer.

    • Like 1

    Little Sweetie Forum amplifier project

    in Talkin' Tubes

    Posted

    24 minutes ago, Travis In Austin said:

    I agree with that premise 100%, but I don't know why. Can you help a neophyte understand why this is true?

    Every device in the signal path alters the signal in some way. The change may be small or it may be large. It may be a change in frequency or phase response, or the addition of distortion or noise, or all of the above. A large change will be obvious, and such a device will probably be noticed immediately and rejected. A small number of small changes won't matter much, but a large number of small changes adds-up to a big change. This is the theory behind placing as few devices in the signal path as possible.

     

    This applies to all devices, passive or active.

    • Like 1

    Rituals

    in Lounge

    Posted

    32 minutes ago, Racer X said:

    I've used Holy water absconded from my local Catholic church.

    Is that for playing your Black Sabbath LPs? 🙂

    • Like 1
    • Haha 1

    Little Sweetie Forum amplifier project

    in Talkin' Tubes

    Posted

    36 minutes ago, henry4841 said:

    Just some rambling thoughts this morning. If we put our heads together I bet we could design an amplifier around the EL84 tube as good if not better than the Decware Zen.

     

    If you don't mind push-pull and PC boards, the PC board used by Audio Note https://ankaudiokits.com/product-category/el84-amps/ and tubes4hifi http://www.tubes4hifi.com/ST35.htm is available as a bare board https://www.aliexpress.com/item/3256801585807617.html.

    • Like 1

    Rituals

    in Lounge

    Posted

    11 minutes ago, Racer X said:

    Oh, well it used to be wet one edge of Discwasher brush with large plastic wood handle grip, three times around the record spinning,

    And the belt-drive table never had enough torque, so we helped it along with a finger pushing on the record label.

    • Like 1

    Rituals

    in Lounge

    Posted · Edited by Edgar
    spelling

    41 minutes ago, Racer X said:

    Does music playback first thing in the morning and upon fall of darkness count ?

    Not quite the same as running the Diskwasher Discwasher brush over the platter, but it counts.

     

    EDIT: spelling

    • Like 2

    Rituals

    in Lounge

    Posted

    I miss manual transmissions, too.

     

    It's a sure sign that you're getting old -- missing the good ol' days that were never really all that good.

    • Like 2

    Rituals

    in Lounge

    Posted

    Just fired-up my ancient reel-to-reel tape deck -- wanted to see what, if anything, was on some old tapes. Threading the tape over the heads, through the pinch roller, and onto the takeup reel brought back memories of the rituals that we used to go through with R2R. Playing vinyl has similar rituals.

     

    Audio used to be participatory. Remember?

     

    Watching the reels turn is mesmerizing. 

    • Like 4

    Are Class D Amps Fatiguing ?

    in 2-Channel Home Audio

    Posted

    26 minutes ago, Racer X said:

     

    File size reasonable, easy to manage

     

    Easy to find, and free to download at that resolution

     

    All the hip new music available instantaneously as MP3

     

    MP3s sound same as CD for the pop music I favor

     

     

    No argument with that, except possibly for the file size, because storage has become so cheap.

     

    I was on the MPEG1 Audio committee in the early 1990s, and had a hand in its development. At the time, storage was limited and bandwidth was expensive. We never foresaw an age when teraBytes and gigabits per second would be available for anything less than a king's ransom, let alone at Best Buy. How times change.

     

    BTW, I was once involved in a blind listening test with MPEG Audio Layer 1 at 384 kbps and Layer 2 at 256 kbps. A track with which I was very familiar was played, sometimes original CD, sometimes MP1, sometimes MP2. My job was to determine whether the particular version being played was CD or not CD. In eleven trials, I was correct eleven times.

     

    MP3 uses better compression than MP1 or MP2, and encoding techniques have improved in the last thirty years, so I probably could not duplicate the feat. Still, it was a gratifying experience for me.

    • Like 2

    SC Estate Sale

    in Alerts!

    Posted

    12 minutes ago, PrestonTom said:

    As I recall around that time you had sketched out some ideas for making the flare rate on the Jubilee have an approximation of a tractrix expansion. Those were fun times on the forum (for the most part) when folks were kicking around interesting ideas. It was a good back and forth........

     

    Jubilee Internals.gif

    • Like 1

    SC Estate Sale

    in Alerts!

    Posted

    3 minutes ago, PrestonTom said:

    At this point I have probably said more than I should have, but this info is public and can be gleaned from various posts and threads from that time period.

     

    FWIW, I remember reading about exactly what you described in a magazine or journal at the time. Might have been Journal of the Audio Engineering Society; I simply don't remember. Maybe in a patent application?

    • Like 1

    Are Class D Amps Fatiguing ?

    in 2-Channel Home Audio

    Posted

    1 hour ago, henry4841 said:

    I have a TPA3255 board build with a linear supply I could be happy with if it were my only amp and I am mostly a class A guy. Best bass I have heard in an amplifier. 

     

    My experience has been similar. I have a couple of vintage amps (G.A.S. Son of Ampzilla and Grandson) that finally died. I discarded all of the original amplifier parts and kept only the linear power supplies; added TPA3255 boards from 3E Audio. Absolutely amazing at bass frequencies, but only adequate at higher frequencies.

    • Like 1

    Little Sweetie Forum amplifier project

    in Talkin' Tubes

    Posted

    13 minutes ago, jjptkd said:

    Vacuum tubes are old electronic components that act like transistors

     

    Sheesh. I am old enough to remember when my father bought his first transistor amp. We looked at it like it was something that came out of a ship from Mars, and were amazed that it actually produced sound despite having no tubes.

    • Like 2
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