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jr@mac

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jr@mac
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JasonP
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  • Steak!



    Most of this pile, along with a mess of smoked/shredded chicken, will be making the trip to Grinnell with me this Friday.

    If ya'll are interested, that is. I could probably pick up some buns and a variety of sauces when I get to town. 
    JasonPD1PP1NPWRRYDkennykR-Carpenter
  • DakotaDIY 2017

    Sponsors are starting to pile on - going to be a lot of happy campers I am guessing :)
    Nicholas_23kennykPWRRYD4thtry
  • Linux based HTPC with multi-channel DSP/crossover

    So this thread: http://techtalk.parts-express.com/forum/tech-talk-forum/1273819-on-the-way-to-active-with-ecasound

    And also this thread: http://techtalk.parts-express.com/forum/tech-talk-forum/67951-new-the-active-crossover-designer-for-ecasound-ladspa-acd-l

    Have got me thinking what to do with an IBM desktop I dragged home this last summer. It has an Intel Core i3 (not sure which version) and I installed 4gb of RAM, a 120gb SSD, a GeForce 210 (fanless), and will be dropping an Asus Xonar DS with upgraded OpAmp into it. 

    It currently has Linux Mint installed on it - to my great joy it natively runs Netflix on Chrome. That has been my biggest complaint about making "the switch" to Linux for my HTPC. As much as hacking a system is enjoyable to me on several levels, I find it annoying to have to hack for mundane purposes such as watching "Frasier" (or to give perspective to the Apple people - to do anything but read email or use a copy of MS Office with reduced functionality). 

    Soooo.... now that I can watch Netflix on Linux, and now that I can stand on the shoulders of giants and implement a pretty kickass DSP on that same Linux box, I have determined what my winter project is going to be :)

    For amplification, I plan on starting with a simple four channel setup using the amplifier section in my Onkyo 809. It is a pretty beefy amplifier section into two channels, somewhat less so on four channels, and like most AVR out there gets pretty tepid in five channel and above. The key, however, is that it does offer seven channels of full range amplification and dual subwoofer outputs so it is pretty flexible as far as all that goes. The video output is toast, so I can no longer take advantage of the incredible video processing but I can use the HTPC to come close. 

    So yeah... winter project lineup:

    1. Max Fidelity/Seas TFFC build with wife. She is going to glue the flat pack up, cut the driver and port holes, finish the cabinet however she wants, and I will hold her hand through the measurement and crossover design process. 

    2. Viawave/Wavecor monitor build. These are going to be my personal monitors in the nerdery, to replace the Vifa/Audax build I did a while ago in honor of the late, great Lou Coraggio.

    In addition to the passive crossover we will be designing for the MF/Seas build, it will serve as the guinea pig for the active system, which will eventually live in our bedroom. 
    JasonPD1PP1N
  • Dayton Audio DSA175-8

    OK, these guys arrive yesterday and I had some time this morning before work to take a look. For starters, the cone is very attractive. The dustcap is aluminum - which I was pleasantly surprised at. I was expecting the same cheap looking treated fabric style that appears on the DA series. Minimal glue squeeze out between dustcap and cone, too. 

    The motor is large, but... the only voice coil venting is the vent out the backside. It is about 12mm in diameter, and while I would like to see a roundover on the vent (along with under dustcap or underspider venting) it is what it is. 

    One serious drawback to this driver is the frame. It is extremely flimsy - that cardboard gasket they provide under the mounting lip isn't meant to do us any favors as a sealing agent - it keeps screws from destroying the cheapass frame. It is ~0.8mm thickness. In constrast to that, a buyout 4" I have sitting on the desk (because I like how it looks with it's old fashioned dimpled poly cone and greenish looking surround) is 1.0mm. And sorry, Dayton - i know it will be buried in a cabinet, but the orange peeled finish on the frame along with an obvious touch-up job just further drives home how cheap these frames really are. I mean, these frames are cheaper than a buyout driver from Orevox that used to retail on their website for $14/pr./Rant

    Since there is no way to peer at the motor internals without wrecking it, I cannot say for sure what type of shorting ring it is - is it copper? Is it aluminum? Is it even effective one iota? Impedance curves imply it has minimal effect. 

    Sample 1:
    Thiele-Small parameters:

    Fs  = 39.47 Hz
    Re  = 5.45 ohms[dc]
    Le  = 193.29 uH
    L2  = 497.67 uH
    R2  = 12.29 ohms
    Qt  = 0.31
    Qes = 0.38
    Qms = 1.69
    Mms = 21.07 grams
    Rms = 3.082220 kg/s
    Cms = 0.000772 m/N
    Vas = 17.95 liters
    Sd= 128.68 cm^2
    Bl  = 8.605253 Tm
    ETA = 0.28 %
    Lp(2.83V/1m) = 88.18 dB

    Added Mass Method:
    Added mass = 20.00 grams
    Diameter= 12.80 cm

    Sample 2:
    Thiele-Small parameters:

    Fs  = 41.63 Hz
    Re  = 5.48 ohms[dc]
    Le  = 198.87 uH
    L2  = 503.78 uH
    R2  = 12.55 ohms
    Qt  = 0.29
    Qes = 0.36
    Qms = 1.59
    Mms = 16.73 grams
    Rms = 2.754248 kg/s
    Cms = 0.000874 m/N
    Vas = 20.32 liters
    Sd= 128.68 cm^2
    Bl  = 8.173118 Tm
    ETA = 0.39 %
    Lp(2.83V/1m) = 89.69 dB

    Added Mass Method:
    Added mass = 20.00 grams
    Diameter= 12.80 cm


    Decent enough unit-to-unit, although I have seen better from Dayton in the past. 

    Of greater concern to me is the blip in the impedance on Sample2:


    That implies a significant difference in break-up behavior unit-to-unit. I am very curious to see Craig and Ron's impedance sweeps - maybe one of mine is an outlier. They are marked, so when I take some in-box I will post the corresponding FR curves. This could be a deal breaker for me, we'll see.

    I am liking these in my 0.38 cabinets, tuned to high 40's or so. Should be bassy enough for music.

     
    So anyways, here ends this review for now. Based on build quality and unit-to-unit, so far I am rating these a solid "C".



    JasonPFace
  • Loudspeaker Design 101 via Harmon

    (Alan Erse linked this on that litterbox forum)

    They know what they are doing, and their technical writing team has assembled an easy to digest bit of very useful propaganda targeted at the DIY'er. One issue I notice is they do not suppress the woofer breakup in their optimized crossover (!)

    https://dl.dropboxusercontent.com/u/16343460/An Engineering Students Guide to Loudspeaker Design, March 31.pdf

    Anyways, nice look behind the cones on the drivers Revel uses - would be interesting to see how the SB Acoustics they use compare to the off-the-shelf models available to you and I. As-is, it appears they use drivers and construction techniques competitive with DIY'ers. I am tempted to contact them and tell them not to link to the DATS v2 as it is more headache than it is worth lol.
    JasonP