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Thread: Tube Friendly 2 Way Designs

  1. #1
    Senior Member JoMoCo's Avatar
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    Tube Friendly 2 Way Designs

    Hi, I would like to build an efficient, high resolution, 2 way able to be driven by relatively low powered (8 to 24 watt 300B etc.) tube amps. Simple, passive crossover if possible. I love the sound of these amps and want to get speakers that work with their old school mojo.

    I stumbled into a pair of 375 type drivers labeled "Jim Lansing by Ampex" attached to rather large metal horns labeled Ampex D-6870.
    Locally, there is someone recommending a TL bass cab with alnico 2215H speaks he has for sale (are they efficent enough for this app?). I am open for input for designs that fit this general criteria and am willing to either use the 375's or something more appropiate if called for. I also have some 2235's waiting for either this, or another project in the future.

    Thanks & Fire away!

  2. #2
    Senior Member jeenie67's Avatar
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    Hi, I have Altec 14's and 15's...very close to what you might want...check em out online and copy? 12" woofr and HF horn. Need a few watts to tick off the neighbors! I have tubes too and Crowns, and Carver(stored away)

  3. #3
    Senior Member louped garouv's Avatar
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    I would see what you can get out of the 375s and 2235s before buying more stuff...

    you may (or may not) want to add a tweeter with a passive crossover to help with the 375's upper limit duties

    have fun!

  4. #4
    Senior Member BMWCCA's Avatar
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    Quote Originally Posted by JoMoCo View Post
    I also have some 2235's waiting for either this, or another project in the future.
    They'll sound fine.




    And then you'll want lots more power!

  5. #5
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    Be careful here.

    If you must have tubes, then you absolutely need a high sensativity rating speaker. Most Altecs VOTT 2-way systems will fit the bill but most JBLs will NOT.

    You need a sensativity rating of 98 or so db at 1 watt, from three feet.

  6. #6
    Senior Member JoMoCo's Avatar
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    Speaker Sensitivity / Impedance Targets

    My target would be for the complete system including crossover & speakers to be able reach 93dB 1w/1m approx., give or take 4dB with a reasonable impedance curve. Interestingly, so called "tube watts" / or more correctly speaker driving ability, for the 300B output tube, output transformer & power supplies, is more negatively affected by large phase shifts & low (below 4 ohms) impedance dips than purely lower sensitivity output. Now what are sometimes called "flea powered tube amps", those under 4watts, need the super high sensitivity speakers to really sing...

    Assuming a reasonably smooth impedance curve...From a 6moons article - "A good rule of thumb for watt/dB combinations is 4w/93dB where every 3dB decrease in speaker sensitivity requires double the power wattage from the amp. Hence, 8w/90dB, 16w/87B, 32w/84dB and so on."

    Remember some speakers / crossovers are easier to drive than others and the whole circuit from output transformer/device to cabling to speaker network to drivers need to be synergistic....YMMV

  7. #7
    Senior Member LE15-Thumper's Avatar
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    TL ???

    By TL do you mean transmission line ? Because they are generally not that efficient. Seems an 030 or 001 or S1 would be a good choice.
    Just my 2 cents
    LE15-Thumper
    "Give me JBL, or give me death"

  8. #8
    Senior Member Tom Brennan's Avatar
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    I wouldn't believe those screwballs at 6Moons if they said night was dark and day was light. 4 watts with a 94db sensitivity system (as would be the base sensitivity of a system using the 2215) isn't gonna give very satisfying dynamics, in theory you'd run out of gas at only 100db. That's pretty loud but momentary dynamic peaks can call on more than that if.

    On the other hand most audiophiles settle for poor dynamics anyway and fixate on other sonic attributes. But IF you want good dynamics with 94db speakers you'll need some power.

  9. #9
    Member iain42's Avatar
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    Quote Originally Posted by Tom Brennan View Post
    I wouldn't believe those screwballs at 6Moons if they said night was dark and day was light.
    The recent Sarajan 300B article on 6moons gave me nightmares

  10. #10
    Senior Member JoMoCo's Avatar
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    Transmission Line

    The bass cab mentioned in the first post, from the pic sent, looks like a scaled down variant of the "scoop" style cab. I know the LE15 / 2215 xmax is less than newer ferrite 15" and benefit more from rear horn loaded cabs to gain bandwidth and output from the cab design...

    "Transmission line" is a type of specialized enclosure topology, in which when correctly designed, sound from the back of the bass speaker passes along a longer path within speaker enclosure and emerges from the open end of the path "in-phase" with the sound radiated from the front of the driver, enhancing the output level at low frequencies.

  11. #11
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    It's all relative,

    Depends how much volume you really want/need for your apllication.

    With 30 watts of push pull tube power I can power pretty much any speaker I own in my setting
    to volumes louder then I "need".

    On speakers of 90-93 db sens 8wpc does more then I need, 95-100 5wpc is enough for me here,
    less then 5watts it's over 100db sens.

    At the present I'm running 2225's to 2118, to 2404 at about 97db sens, the little SEP EL84 amp
    isn't even sweating at all to give an incredible amount of volume.

    Also ran the 2225 to a waveguide an comp setup 2-way with nice results, the other setup that
    does better bass is an HPM-100 woofer to a waveguide and compression driver at about 93-94.

    Impedance plays bigger part as mentioned, non complicated xovers, even lower sens speakers
    can be driven with relitively small amps when they are bookshelves using smaller drivers.

  12. #12
    Senior Member Beowulf57's Avatar
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    Horn-loaded design possibility

    Or you could play around with this type of design: http://audioheritage.org/vbulletin/s......sensitivity 102-103dB/watt @ 1 metre.

  13. #13
    Senior Member JBLRaiser's Avatar
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    To me, it depends on the music.

    If I'm listening to Eva Cassidy, a few watts will do. For Pink Floyds' Comfortably Numb, a few hundred watts will do.

  14. #14
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    I think you need to be looking at 95 db sensitivity or you will find yourself sift clipping those types of amps.

    The E145 and a suitable horn like the 2397 and 2441 driver might be interesting.

    If you can afford it look at the new GPA drivers. There are some members who use that type of driver with tubes amps.

    Ian

  15. #15
    Senior Member JoMoCo's Avatar
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    JBL / Altec / 12" high efficiency midbass driver

    Any recommendation for a vintage or modern 12" that would compare or surpass the Altec 414 in the midbass keeping in mind the 2way configuration?

    "One advantage of the 12" Altec/GPA driver is a cabinet volume one-half of what a 416 or 515 15" driver require. Don't expect deep bass - that's the job for separate subwoofers, not a high-efficiency midbass driver."

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