The "Minion" 8" B&C + DNA-205/EOS-8 bookshelf/surround design

Discussion in 'Legacy Speaker Designs' started by Matt Grant, Nov 19, 2012.

  1. Are you looking to build a DIY sub or buy one? Budget? Size limits?
  2. DIY, 350 to 500 bucks, the smaller the better, would need a dual voltage or amp as Im in Australia(come to the US often), quality over quantity is what i like, thanks
  3. Woofer:

    Plate amp:

    Port tube:

    That is about $450, should leave you enough to build yourself a 3cuft (85L) net internal enclosure which is fairly compact for the output that combo will give (you want something that will keep up with the mains). In room you should see extension to the mid-low 20's. The low knee rolloff is a smooth slope (like a sealed sub would be) which I feel helps the bass sound tighter and more well rounded.

    If you need help planning out an enclosure that will fit everything and be the correct volume let me know.

  4. This one OK?

    I guess the tricky bit will be getting the Amp around/inbetween the box bracing

    I will be in contact with Erich and start the order process ;D
  5. Actually fitting the port tube in there may present an even greater challenge. Too bad that 4cuft ported flat pack won't fit a 15".
    The 15" RS HF would be a better choice if the port will not fit in the 3cuft, but you loose about a dB above 40hz and about 5dB at 25hz.

  6. Start planning mtg!

    For my benefit, why do you think PE advertises their 3cu ft for this driver, you'd think they would know it's not really big enough?
  7. Well I ran into a slight snag with the single 4" port in that I could not get both the woofer and port to fit on the same face. So this revision uses two of the 3" precision port tubes at full length. It looks pretty similar to the 4cuft ported model for the 12" woofers except this one is about 3.3cuft net after subtracting for bracing, driver, etc...
    18"w x 22" h x 22"d external, 3/4" material thickness, double thick front baffle.

    The box PE sells works great with the 15" HO if left sealed, you just can't port it.
    BTW look closely at the pictures of it and the 3.0cuft here on DIY soundgroup, notice anything? ;)

    Attached Files:

  8. They look the same, price is different?
    Would slot ports work? Just to make it look a little similar to the Minions

    Edit: is it easy to put the amp in your one?
  9. Here is a slot port version, I changed the depth a little just because I like sub boxes to be a little deeper then they are high.

    One that shows the insides has possible position of plate amp. Don't forget to add bracing too, I hate trying to draw those in sketch-up.

    Attached Files:

  10. Sorry, are you saying put the HF in the 3cuft box unported, or in the ported 4cuft or unported 4cuft? I've been doing lots of reading over the last few days, and I think the HF will be a better fit for me, re music. I could get the 4cuft box and make my own front baffle if need be.

    I'll start a new thread so as not to high jack this one.

    Here tis,
  11. Yeah the HF is better in sealed enclosures as its native response will extend down further (lower F3 then the HO in the same enclosure). For a ported enclosure the HF likes them on the larger side (6cuft+), while the HO works in more manageable sizes
  12. giverago, did you ever get the minidsp running with the alpha 8s ? I too am using a minidsp 2x8 w/ the 4x10 plugin with the alpha 8 Minion and the .6ft^3 boxes. Just getting started. I use REW program/UMIK mic auto eq for the bass and horn EQ. Loaded the biquads into the 2x8 running the speakers in a bi-amp system. Individually checked each speaker’s frequency response, level, polarity and time phase with biquads enabled, and all looked OK. Played some music and the sound seemed harsh, something that would fatigue me real quick. Moved the xover around from 1200-2400, 12-48 db/oct. Added 1/2 -1 lb accustuff to each speaker. Nothing seemed to help. Giverago how did your system/setup end up sounding? Could you post the minidsp file?

    Please do not think I am saying this harshness is the speakers fault. I have not tried the xover that came with the speakers. Until I build and install the xover that came with the speaker these comments on the sound are about my crappy tuning. I have had such good luck with the above set up method I thought I would give it a try first. This is the first waveguide/pro woofer I worked with, maybe it is a little different to get set up correctly. I do hear the dynamics and imaging these speakers will offer if I can calm them down.

    One other thing, I do have a lot of port air noise. Anyone find a cure for this?

  13. If you want here are active settings that mirror the passive version,

    3rd order BW @ 1050Hz
    1800Hz, 4dB, Q=2
    2800Hz, -10dB, Q=2

    Gain -11dB,
    3rd order BW @ 2500Hz,
    1700Hz, 1dB, Q=4,
    2000Hz, 11dB, Q=2,
    3000Hz, -7dB, Q=0.5
    6000Hz, -3.5dB Q=0.5

    As for the port noise I was worried someone might have that issue. Are you using them fullrange? It should not be as bad if used with a highpass around 80hz but those smaller ports Erich found which fit quite nice can only let so much air through. Only option I see is to modify the cabinet for a full width slot port like I used with my test enclosure. I'll have to go back and measure what that was.
  14. Mtg90, thanks! I will plug these in and see what this does. The woofer xover freq, is the 1050hz correct? I get a -11db for both speakers at 1620hz. Seems like a large dip but the woofer does have a peek in this region. I dont have a 3rd order on the minidsp, 2nd LR or 4th LR. I'll have to work around this.

    As for the port noise. I was running full range. I am building a Dayton UM12-22 sub so these will most likely be x-overed at 80hz. I'm not sure I could mod the box with a full size port with it all glued together. I'll have to think about this.... On second thought it might not be that hard, hummm.

  15. Yes 1050Hz, Not Linkwitz Riley (LR) filters, use Butterworth, BW 18dB/oct is what it will say in the minidsp drop down box for filter settings. Don't forget to plug in those parametric EQ settings for each driver too.
  16. Oh crap,I didn't see all the other filters on the drop box! There are so many! :eek:

    What was the size of the full width port? I think i'll move over to it.

    Thanks again, Brad
  17. The port should be 1" high by 6" long, so cut the internal port panel 5.25" long (+ 0.75 for baffle = 6"). You may be able to use the bottom cabinet brace to your advantage leaving it intact and cutting two separate pieces to fit between it and the walls and be able to inset them through the woofer cutout. After they get glued in you could then flush trim the openings to that full size.

    Only question I have is how far up is the top edge of the current port cutout, the above may need a little adjustment if it's over 1.5" from the bottom of the cabinet (1" from bottom panel).
  18. Ok, been doing a lot of tuning on the speakers. I seem to be getting a lot better sound, think "not so harsh", when I bring the xover down low and going steep. 1100-1200hz, 48db/oct. Question, can the 205 handle the power frequency that low? Also, I so thought the harshness was from the 205 but now looks to be the B&C. Has anyone seen cone breakup on the B&C in the 1500-2200 range? The graph does show something starting at about 1500hz. My guess now is this is cone breakup. I have a feeling this is the harshness I hear.


    Attached Files:

  19. 1100-1200hz may be a little low for the DNA-205 when run at higher volume levels. I dug up two of my measurements for the 8PS21 and both show peaks from cone breakup starting above 2.5k. The one with higher resolution was taken outdoors and has not smoothing or gating but the resonance from the port is clearly visible and the dip and then peak from 800-1000hz, the other was taken indoors with the port closed but due to the amount of "room noise" in that measurement I had to use heavy smoothing to get a clear picture.

    Attached Files:

  20. Here are my measurements of the BC 8". I’m testing indoors with the speaker in front middle of a 16x25 room, 18' ceiling, heavy carpet. Speaker off the ground 4’. Mike, UMIK, 6”, 12” and 24” in front center of speaker. MTG do you think the dip at 1.8k is “resonance from the port”. If so would this not be a peak? I am thinking whatever is going on at this 1.8k-2.0k frequency is what I think sounds harsh. This might be why when I set the xover below this frequency the harshness is reduced.

    Graph 1 is Left speaker and Right speaker w/ 1/48 smoothing to see determine if both speakers are test the same. As can be seen both speaker test real close to each other.

    Graph 2 the speaker was tested at 6”, 12” and 24”. If the dip at 1800hz was port resonance would these measurements look so close?

    Graph 3 is speaker at 6” no filtering. Next Post

    Attached Files:

  21. Speaker test no filter, 6"

    Attached Files:

  22. Pict of room/speaker test

    Attached Files:

  23. I have a somewhat similar dip on my measurement even with the port sealed. The port resonance with the slot ports included is around 1700hz, it may be doing something there the only way to confirm is to try and plug up the ports with something and measure again. A port resonance can show up as a dip, a peak or both a dip and peak in the response.
    Did you use a notch filter with the higher crossover point? What could be your problem is the low pass of the higher crossover point is not enough to bury the cone breakup to the point that it no longer sounds harsh while lowering the crossover to 1100-1200hz does.
  24. Any specific stuffing/dampening recommendations for these? I was thinking about getting some acousta-stuf and ultra touch denim insulation. What do you use Matt?
  25. For medium sized boxes (like this one) and larger I use the ultra touch denim myself. I try to leave plenty of room around the back of the woofer and keep a clear path to and around the ports, I then line everything else.

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