FS: Concentric-6 Coaxial Drivers!

Discussion in 'Classified Section' started by Matt Grant, Jan 27, 2021.

  1. #1 Matt Grant, Jan 27, 2021
    Last edited: Jan 21, 2024
    Update January 2024:
    --All Sold!--

    Concentric-6 coaxial driver - $120 + shipping (I will throw in the bare crossover PCB)

    Additional options:
    Fully assembled crossover for the Concentric-6 - $60 (built to order).
    CNC cut MDF Baffles - $10 each (multiple size options)

    • 11.75" H x 8" W - Standard baffle size, driver centered on baffle.
    • 16" H x 8.5" W - Baffle for larger ported cabinet, driver 5.5" down from top, cutout for 2.5" flared port below (Parts Express #260-478). Sized to fit the Denovo 0.56 cubic foot flatpack enclosure.
    • 13" H x 8" W - Driver center placed 5.2" down from top, can be modified for use in the angled cabinet examples I built.

    I was recently doing some cleaning/reorganizing and remembered I had a bunch of these drivers that I had gotten from Erich. Unlike the Concentric-8's these never made it into kit form but they are really excellent sounding 6.5" coaxials. Much better sounding and measuring then any of the Volts, I am saving several of these for myself because I really haven't found anything in the 6.5" range that match them.






    HF driver is a 1.75" titanium compression driver with copper cap on the pole.
    Woofer T/S Specs:
    * Piston Diameter = 134.6 mm
    * f(s)= 85.46 Hz
    * R(e)= 5.20 Ohms
    * Z(max)= 56.26 Ohms
    * Q(ms)= 7.551
    * Q(es)= 0.768
    * Q(ts)= 0.697
    * V(as)= 5.519 liters (0.195 cubic feet)
    * L(e)= 0.45 mH
    * n(0)= 0.43 %
    * SPL= 88.41 1W/1m
    * M(ms)= 17.87 grams
    * C(ms)= 0.19 mm/N
    * BL= 8.06
    Could be used sealed in a 0.25-0.5cuft box for an f3 of ~90-100hz.
    Or can be used ported 0.35cuft tuned to 70hz (f3 ~ 60hz)- 0.5cuft tuned to 60hz (f3 ~ 50hz).

    I had previously built four of these for a member on AVS forum several years back in sealed angled boxes for surrounds:


    Angled 6in Coax box.png

    Crossover Schematic:
    Concentric-6 Crossover Schematic.png
    Crossover parts list:

    Concentric-6 crossover.jpg

    Frequency response 0-90 degrees off axis:
    0-90 degrees off axis.png

    Attached Files:

    Brinkman likes this.
  2. Those look familiar!! I’m still using them as surrounds. How would they work as LCR? Rearranging my family room soon, was going to go with in wall speakers but I don’t think they’ll work. The wall I want to mount my tv is shared with the laundry room. I’m afraid of hitting water lines, electric etc... Not sure if these would be a food LCR option or if I should look at HT-6 or 8’s? Maybe could mount those to the wall for LCR?
  3. These could be used for LCR especially in a family room setup where the single 6.5" can usually give more then enough output for normal people. They would probably be best used in ported enclosures for LCR to extend the bass response and minimize cone excursion, though that does increase the required enclosure size a little.

    I'll have to double check the driver depth to see what could be done to make something shallow for wall mounting.
  4. So then the answer really is no ;)
  5. #5 Matt Grant, Feb 23, 2021
    Last edited: Apr 19, 2021
  6. I am interested in 4 Concentric-6 with baffles.
  7. Would these blend well with the ht8?
  8. They would likely work ok with the HT8, no worse then the volts which many people use together with the HT series with good results.
  9. Do you have any baffles left?
  10. #10 Matt Grant, Feb 28, 2021
    Last edited: Apr 19, 2021
  11. I’ll take two with black baffles and two PCB’s.
  12. I don't have the PCB's yet as I am waiting until I verify the crossover values but will post here when they are available.

    I'll send you a PM for payment details.
  13. I now have the PCBs for these and in case you missed it I posted the crossover information as well as the measured frequency response at the end of the original post.
    Brinkman likes this.
  14. Matt. I received the PCBs today. Thank you.

    Question: what do you think of using a top-mounted variovent with these drivers? I’m replacing my four sealed-box volt-6 surrounds with these and wanted to do something a little different.
  15. It could be interesting to try, through the f3 on these is already quite high when sealed and using the aperiodic vent to decrease the Qts would increase it further to some degree.
  16. That was a concern; trading LF extension for transient response. A little googling wasn’t too enlightening as to how much LF surround speakers typically see. I never noticed much bass from my Volt-6 surrounds with the exception of the pod-racing sequence from The Phantom Menace and even then the mix was more midrange and HF. I don’t think I’m listening at reference levels, lol.
  17. Would these fit in the slanted and ported enclosures that come with the Volt-6 kits? Are they 8-ohm and high efficiency, similar to the Volts, so that they can be powered by a typical AVR?
  18. They would work in the slanted Volt-6 flatpacks but obviously the stock Volt-6 baffle isn't compatible with this driver. It should also be used sealed in that enclosure.

    They are 8 ohm and efficiency is decent (~90dB @ 2.83v) so a normal AVR should have no issue driving them.
  19. #19 Charles Collins, Mar 30, 2021
    Last edited: Mar 30, 2021
    I definitely want four, with assembled crossovers and16” x 8.5” mdf baffles that would fit the Denovo 0.56 cubic foot enclosures that Parts Express stocks 300-7064 (which I could order from them). I just need to figure out the proper port size for that enclosure. Please PM me if this is something you can do. Thanks Matt.
  20. I've previously cut some baffles designed to fit that box for another member, it was designed to use the 2.5" flared port that PE sells, the port should be cut to 5" which should give a tuning a little below 65hz and an f3 in the mid-low 50's. Let me know if that works for you?

    16x8.5 baffle.png
  21. Matt, thanks that looks perfect. I tried to reply to your PM but it wouldn’t accept it. Please do send an invoice for everything. Thanks.

    Edit: I finally got the PM to work.
  22. I am interested in a couple of these with the black baffles and crossover parts if possible!
  23. #23 Matt Grant, Sep 6, 2023
    Last edited: Nov 1, 2023

    Discovered eight more of the drivers at Erich's Shop on a recent visit. Same price on those $120 each + shipping.

    I still have some crossover PCBs and will include those for $5 each if wanted.

    I can also cut baffles like shown in my last post on this thread for $10 each.
    taloyd likes this.
  24. Just curious, but do you have any advice on how you built the covers for these? They look absolutely so clean and would love to do something similar for some other DIY speakers.
  25. It's a simple MDF frame with a small round-over. The trick for a clean look is using adhesive transfer tape on the back of the frame to hold the grill fabric in a stretched state before stapling.

    I have some photos of the grill assembly on my slipstream build near at the end of that page.

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