Karma-8 EOS-8 version

Discussion in 'DIY Speakers and Subwoofers' started by Matt Grant, Mar 16, 2013.

  1. How do you guys think these speakers would match up to the Cheap Thrills for use as surrounds and possibly height channels with the 'Thrills as L-C-R? Would the voicing be similar?
  2. Probably close enough that you would not notice with the playback of regular material.
  3. Thanks for the quick reply, Matt. If I elect to go with a ported design using the DIY .6 ft^3 flatpack, what port dimensions would you recommend?

    My intended application will be as surrounds in a small home theater with 3 Cheap Thrills as L-C-R and ultimately a subwoofer or two, probably crossed around 80Hz.

    When I model this speaker in WinISDpro, i come up with a 2" tall slot port as a reasonable (to a real noob like me) tradeoff between box volume and port air velocity, but from the pictures it looks like you used 1.5-1.75". What's got me a little sideways are the following:
    1. Should I include a subwoofer highpass filter function in the box model (say, a 4th order Butterworth)
    2. How much should I worry about port resonance within the woofer pass band
    3. I don't know the extent of my ignorance... :p
  4. If you are crossing over to a sub model with a highpass filter. IIRC most avr's use a 2nd order highpass on the speakers and a 4th order lowpass on the sub.

    I can't remember the exact size I made the port in that enclosure but when modeling a 1" high by 5" long slot port (~70hz) keeps thing well under control with a highpass at 80hz and up to 200w input power

    The port resonance is still within the passband but you will be hard pressed to get it moved out without air speeds going through the roof or moving tuning too high. I feel the noise created from an undersized port is more objectionable then the issues from the port resonance when dealing with it at these frequencies.
  5. Thanks for the guidance!

  6. Is your crossover point around 2K? (The Celestion could go up to 3K)
    If it is 2K, how are you using a first order with a 1.5uf on a 8ohm driver to achieve it? My xover calculators on the web say it aint possible.
    (I assume the 6R and 7R are padding down the driver.)

    Does the EOS8 loading make such a difference?
    What the heck am I missing?!
  7. The online calculators assume a flat frequency response and impedance while the FR and impedance of most loudspeaker drivers are not quite as ideal.

    The native FR of the DNA-150 in the EOS-8 has a peak right around 2.5k and slowly tapers above that down 10dB by 20k. The impedance also peaks right about 2.2k. these two things let you use a much smaller cap then you would think possible based off of the online calculators. The rolloff from the small cap basically counteracts native rising response as frequency decreases towards 2k. The impedance peak also plays a roll providing some extra boost right above 2k, it also causes the transfer function to drop very quickly below just that point allowing the single cap too act like a higher order circuit through the crossover region. The l-pad is primarily for padding but it also allows a little adjustment of taper in HF response. It really works out well in the end using far fewer parts then I would have thought possible.

    I suggest playing around with Jeff Bagby's Passive Crossover Designer. A lot can be learned about crossover circuits, why and how certain things are done that don't make sense when you plug in only impedance, crossover frequency and slope into online calculators.
    I can send you some FRD and ZMA files if you want but I also believe it includes a couple sample response and impedance files too.
  8. I've just started to play with Jeff Bagby's Passive Crossover Designer.

    Please send me FRD, ZMA and anything else that can help understand this DNA 150 driver on the EOS 8.
    I have a pair of the mini ellipticals now. They sound pretty good.

  9. I added the files in a zip folder and attached here.

    Attached Files:

  10. I am considering using this design for side and rear surrounds in a small room to mate with my Cheap Thrills as L-C-R. The listening position is ~7-12 feet from the speakers. I plan to mount these speakers at the intersection of the wall and the ceiling above the listening position for the side surrounds and 2-feet behind the listening position for the rear surrounds. The closer distance is when the listener is sitting below the speaker, ~3 feet from the wall and the longer distance represents the opposite channel. The room is ~ 10 feet wide at the listening position.

    Here is the proposed enclosure (pardon my crude Sketchup picture):

    What are the issues in using this design with the enclosure and placement described?

    Is there a better way to accomplish this in such a limited space?

    Thanks in advance for your replies (I also posted this question over at AVS Forums).

    Edit 12-16-13
    I've decided that a small coaxial speaker, the 10" Eminence coaxial woofer with the DNA 150 Compression Driver, the V-10 Volt, is the answer to the last question above.

    Attached Files:

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