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My RS180 MTM Design

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  • bullittstang
    replied
    Re: My RS180 MTM Design

    I disagree slightly in that I've used the SB26STCN and have crossed as low as 1600-Hz, currently crossing at 1800-Hz and 2nd and 3rd order distortion is very low and at almost 95-db it doesn't show any signs of distress. I really like this little tweeter and it's easy to work with too. Also Jeff used in his Sopranos and mentioned he is crossing at 1750'ish as well and noticed no issues. To get the same look as the RS, you could use the SB26STAC which gives you a lower FS, but similar flat response and easy to work with. Just my $0.02.

    Leave a comment:


  • PWR RYD
    replied
    Re: My RS180 MTM Design

    That SB tweeter is fantastic and one of my favorites. But I wouldnt push it any lower than 2kHz. I think the RS180 needs a tweeter that can cross lower like the RS28 can.

    Leave a comment:


  • Mike220
    replied
    Re: My RS180 MTM Design

    I have 4 of the shielded woofers I've been wanting to build these but am missing the aluminum shielded rs28A's. I really don't want another build with the RS28's as im coming up to my 3rd of 4th one with rs28's (its a great woofer im just tired of using it) but these woofers seem kind of fickle with the high levels of cone break up. Any other builds that use these or a potentially equal tweeter that can be used? Perhaps a sb acoustics tweeter like the SB26stnc or something else. Anyone have another tweeter suggestion?

    Leave a comment:


  • Chris Roemer
    replied
    Re: My RS180 MTM Design

    All of these port observations of yours seem valid to me.

    Leave a comment:


  • kraigo
    replied
    Re: My RS180 MTM Design

    FWIW, when I get these done, the first album I'll be playing through them is XTC's "English Settlement". Well done in terms of production, but my #1 Desert Island album for most of my life.

    Leave a comment:


  • kraigo
    replied
    Re: My RS180 MTM Design

    OK, one more rookie question: Someone in some thread or another posted that this (http://www.parts-express.com/speaker...lared--260-480) is an appropriate port for this cab, but my modelling in WinISD show that as not even being close to right to getting a 1ft^3 box tuned to 40 Hz. A single 3" port somewhere between 9.5" and 9.75" looks to work ("9.66" according to WinISD), but now I'm second guessing my school-of-hard-knocks speaker skills. If anyone can give me a confirmation, I'd appreciate it. That port gives (by my work) about a 53.5 Hz tuning.

    Added: Or someone could just tell me what the appropriate dimensions are (bonus points for why)! :-)

    If it helps, enter the following text into Notepad, save it as a .WSD file and load that into WinISD.

    >>
    [Driver]
    Brand=Dayton
    Model=RS180-8
    Manufacturer=Dayton
    ProvidedBy=kraigo
    DateAdded=20150807
    DateModified=20150807
    Qts=0.31154861916003
    Znom=8
    Fs=35.54549813519
    Pe=0
    SPL=86.268920766928
    Re=6.4
    Le=0
    fLe=0
    KLe=0
    BL=7.82
    Xmax=0.006
    Cms=0.00112
    Qms=1.22
    Qes=0.41839257817385
    Rms=3.27685838851422
    Mms=0.0179
    Sd=0.01247
    Vas=0.02470560978984
    Dia=0
    Vd=0.00007482
    no=0.0025789727626
    Dd=0.12600514720775
    EBP=84.9572865043019
    numVC=1
    Hc=0
    Hg=0
    SPLmax=0
    SPLmaxLF=78.0447656770847
    USPL=87.2428497375749
    alfaVC=0
    Rt=0
    Ct=0
    gamma=436.871508379888
    Rme=9.5550625
    Mpow=3.09112641281459
    Mcost=0
    Gloss=0.03276728653333
    VCCon=1
    c=343.684120962152
    roo=1.20095217714683
    Thick=0
    Depth=0
    MagDepth=0
    Magnet=0
    Basket=0
    Outer=0
    Vcd=0
    DVol=0
    ParState=ECNCENNNEENEECCCEECCNCCENNNCCNNNCCCCNCNNN NNNNNNCC
    <<

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  • Jeff B.
    replied
    Re: My RS180 MTM Design

    Originally posted by PWR RYD View Post
    Looks like Jeff and I were posting at the same time. I'm sure he has more experience with these drivers than me so go with his recs.
    Actually, it was a test that Paul Carmody did that showed the two identical except in the are of Fs where the difference in their Q's showed up.

    Leave a comment:


  • PWR RYD
    replied
    Re: My RS180 MTM Design

    Looks like Jeff and I were posting at the same time. I'm sure he has more experience with these drivers than me so go with his recs.

    Leave a comment:


  • PWR RYD
    replied
    Re: My RS180 MTM Design

    Yes the shielded version of the RS28A was more sensitive than the currently available unshielded version. I have both and the shielded are 91 and the unshielded are only 89. My RS28F-4 are 89.2. Not saying your project is undoable, just something to consider. Hopefully others here can add personal experience and insight.

    Leave a comment:


  • Jeff B.
    replied
    Re: My RS180 MTM Design

    Originally posted by kraigo View Post
    Thanks for your reply. The sensitivity of the RS28F-4 is pretty much the same as the sensitivity of the RS28A-4. Was the shielded RS28AS-4 more sensitive? Since the parallel RS180-8's and the RS28x-4 are both four ohms, shouldn't the RS180's combine to add 3dB over a single RS180? You get no boost for going from eight ohms to four ohms, the combined RS180's can be thought of as having a sensitivity of 90 dB as does the RS28F-4. Is my math or understanding wonky?

    As far as the crossover, I'm mostly wondering if those caps are what people tend to use. The cost of the crossover components is almost $100, which I'm willing to pay and is cheaper (due to low component count) than almost any other crossover you'll come across for the MTM's that use this configuration. OTOH, if I'm way over spec-ing things or I've made a rookie mistake, I really want to know before I put out the dosh.

    Thanks again for the reply and any help you guys can give me.

    KO
    Your component list is fine, and probably in line with what others use.

    A parallel pair of 8 ohm drivers increases sensitivity by 6 dB. We give most of this back in the form of baffle step compensation though.

    I believe as advertised the shielded version is listed as more sensitive, but, and I'm going by memory here, but I believe this is correct, when actually tested head to head both versions of the RS28a were the really the same sensitivity.

    Leave a comment:


  • kraigo
    replied
    Re: My RS180 MTM Design

    Thanks for your reply. The sensitivity of the RS28F-4 is pretty much the same as the sensitivity of the RS28A-4. Was the shielded RS28AS-4 more sensitive? Since the parallel RS180-8's and the RS28x-4 are both four ohms, shouldn't the RS180's combine to add 3dB over a single RS180? You get no boost for going from eight ohms to four ohms, the combined RS180's can be thought of as having a sensitivity of 90 dB as does the RS28F-4. Is my math or understanding wonky?

    As far as the crossover, I'm mostly wondering if those caps are what people tend to use. The cost of the crossover components is almost $100, which I'm willing to pay and is cheaper (due to low component count) than almost any other crossover you'll come across for the MTM's that use this configuration. OTOH, if I'm way over spec-ing things or I've made a rookie mistake, I really want to know before I put out the dosh.

    Thanks again for the reply and any help you guys can give me.

    KO

    Leave a comment:


  • PWR RYD
    replied
    Re: My RS180 MTM Design

    My only concern would be the difference in sensitivity between the RS28F and the original shielded version RS28AS that Jeff used. I don't remember Jeff needing any padding on his tweeter. The F version may not be able to keep up with the two RS180's in parallel.

    Leave a comment:


  • kraigo
    replied
    Re: My RS180 MTM Design

    OK, I am building a pair of these and since it might be helpful to future readers, here's what I have for the crossover parts

    20uF - http://www.parts-express.com/dayton-...citor--027-252
    10uF - http://www.parts-express.com/dayton-...citor--027-244
    50uF - http://www.parts-express.com/50uf-10...citor--027-354
    ***Note that going with an NPE cuts about $30 (37.5%) off the total cost of the crossover and that Jeff said he used an NPE in the initial post

    1.2mH - http://www.parts-express.com/jantzen...-coil--255-254
    0.025mH - http://www.parts-express.com/jantzen...-coil--255-198
    0.25mH - http://www.parts-express.com/jantzen...-coil--255-214

    Since I'm using an RS28F-4, Mike Price is talking about a Zobel to tame the high end in this thread:
    http://techtalk.parts-express.com/sh...25#post1749425

    It adds $4.34 to the cost of the crossover:
    2.5uF - http://www.parts-express.com/dayton-...citor--027-218
    1 ohm - http://www.parts-express.com/dayton-...esistor--004-1

    Please correct me if I've made any stupid mistakes. I haven't bought these yet.

    Thanks in advance.

    KO

    Leave a comment:


  • Jesse055
    replied
    Re: My RS180 MTM Design

    Since I'm using the one RS 180-4 instead of the 2 parallel rs180-8 I will need to pad the tweeters down 3 db. What resistor values will I need to hit the 3 db?

    Leave a comment:


  • Jesse055
    replied
    Re: My RS180 MTM Design

    Originally posted by Jeff B. View Post
    It does. The program doesn't run in Excel 2013 or in Excel 2010 if it's a 64 bit application. It runs fine in 2010 32 bit and all earlier versions down to '97.

    Jeff
    Got the parts in and am ready to do this with the rs28f and one 180-4. I need 3 db of padding on the tweeter. This rest of the values on e original circuit will stay the same? Is at correct.

    Leave a comment:

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