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DSA175 + RS28A

edited September 2016 in DIY
So my baffles arrived from Roman today, and I will be doing in-box measurements probably tomorrow after work. 

(Still have to do the magic marker thing to hide the bare MDF showing through the driver cutouts)

The DSA are really good looking drivers. I hope they perform better than their paper cone counterparts. 
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  • Is Roman doing cnc stuff for people? Even if it's just baffles I could use to farm out some work at times. 
  • He charged me eleventy beelion dollars. 
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  • A modest dispensing of sheckles for a fine piece. 
  • JR, you didn't mention sales tax. :s
    ............. could you hum a few bars.
  • Early simulations are proving to be a pain the ass. Of course, I am using doctored PE supplied FRD files and I believe their supplied FRD for the RS28 is fucked. 
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  • So between working all day yesterday, cleaning my garage (what a fucking mess that was) and yardwork and getting dragged out Friday night with some engineers from a vendor, and deciding to party it up last night, I did manage to find time to clean up the baffles Roman cut for me and get them ready for in-box. 

    Due to laziness, I am going sealed on these. I will be giving up some oomph, but in these cabinets they will do F3/6/10 of 80/60/42 in a critically damped alignment (Q of 0.52). So, I am expecting a nice, clean impulse if not thumperific good times. 

    The fit of the Dayton baffles to the Dayton cabinets is shit, and I think I broke one t-nut already. On the other hand, the gloss finish is fairly legit and they are aesthetically pleasing from a HxWxD perspective. The two drivers fill the baffle out juuuuuust right. 
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  • I really like overdamped bass. I worked on the model for my Shockwave speakers for weeks to get the right response (more bass than sealed, near-overdamped looking impulse, and <400 group delay) I'm hoping they sound half as good as the effort i put into designing them haha.
    deadhorse - leviathan - harbinger - shockwave (wip)
  • Out of curiosity, I modeled these with the addition of a 2nd order highpass centered at 80Hz. This particular design will make for a serious satellite in a home theater. It will exceed thermal limits before mechanical limits - easily hitting 105db+

    If they were designed in such a manner as to be able to take advantage of boundary reinforcement below the baffle step, there is no reason not to expect nearly 110db of output staying within mechanical limitations and barely exceeding RMS thermal ratings - and always staying under the so-called "peak power rating". 

    Modeling using peak power rating in addition to the high pass filter yields levels in excess of 110db. This would require a pretty serious amplifier to do this as we are talking close to 150 watts per channel, and it would also require a pretty serious subwoofer to hit "reference +10db" levels... Yes, that is how capable this little design could be.

    Whether the motor on the DSA is capable of playing to such a level without going to shit remains to be seen, and while it is fun to model and ponder such output levels it has to be remembered that other than a small-ish vent out of the backplate, there are literally zero other voice coil cooling or pressure relieving features on this driver. I am guessing power compression from mechanical issues will kick in prior to thermal compression. 

    Soooo.... that being said, it makes you wonder why Dayton doesn't charge us an additional $5 and include a frame similar to the ones showing up on the new drivers from MCM. Given MCM pricing, it is obvious that using such a frame isn't necessarily a serious expense, and the benefits from an aluminum frame go beyond mere rigidity and proper cooling/pressure relief. My guess is this DSA would be extremely competitive with the Reference drivers if a better frame were to be used, and my suspicion is that Dayton is maintaining the RS line as their perceived "bang for the buck" lineup by purposely engineering flaws into their lower end drivers, rather than deliberately engineer for a favorable price/performance ratio. What we end up with are a driver line like the Designer Series which appear to have all the right parts assembled in a very non-optimized manner. 

    The Le curve on the Designer Series - even these new ones with an alleged copper pole piece cap - resembles $6 drivers. The frame is as cheap of construction as I have personally seen. The lack of under-spider and under-dustcap venting and the lack of a bumped back-plate are features we see on affordable (in fact - cheaper) stamped frame drivers from Tymphany, and those features have also been showing up on cheap-ass car audio subs, so it isn't like using a stamped frame defaults to being forced to using a poorly engineered frame.

    I think the world-class Dayton quality control combined with some actual good driver engineering would go a long ways towards making them the heavy hitters they seem to want to be. Take those damn Esoteric drivers, for example. All that work into optimizing the motor and they slapped a shit cone on it, and now they are finally fixing what should have never needed fixing. 

    Sorry for the rant - I will be taking some initial measurements when I get home from work today. I also want to hook one of these up on the desk and do some sine sweeps and see if I can get the frame to ring. I expect they will benefit from some rope caulk added here and there. 
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  • So far so good...

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  • Has anyone posted distortion measurements yet?  I was never happy with the DS135s, hope the A means acceptable...

    I'm kind of liking how these model.

     John H, thanks to JP I did get that email
  • I am not at liberty, or able, to post what JR had shared with me regarding the DSA175. But I know it looked nice.
    = Howard Stark: "This is the key to the future. I'm limited by the technology of my time, but one day you'll figure this out."
  • It's coming, and soon.
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  • Can I post this ? I thought the one channel speaker I heard sounded very nice and from what JR mentioned , not much to the Xover  B)
  • This was one channel listening , as he mentioned , things could change when he gets the other speaker rigged up . Pretty damn nice though from what I heard 
  • Are the driver rebates cut way too deep or way too big?
  • PWRRYD said:
    Are the driver rebates cut way too deep or way too big?
    A little of both plus sharp edges, high contrast, and camera flash.
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  • Black magic marker will make that much less noticeable.
  • Yes, yes it will. Not permanently mounted just yet.
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  • Impulse response of sample 1:

    Impulse response of sample 2:

    I didn't zoom in on sample 2, but the odd shape of the impulse is still very apparent. Not sure what was missed in the production run to cause that, but it cleans up when a low pass is in place, and doesn't affect sensitivity or extension. Not sure I will call it a real problem as of yet.

    Sample 1 distortion (SPL accurate, 1M - so I was banging hard on it):

    Sampe 2 distortion (Same conditions):

    Close enough for me - and that spike at 4.7K or so in Sample2 is audible through the entire sine sweep - leads me to believe it is the flimsy frame. Otherwise, that weird impulse doesn't really present anywhere else. 

    Frequency Response Both Samples Overlaid:

    Again, within the pass band, virtually identical - so the weird impulse on one sample is just puzzling to me - I have never had a driver measure like that before. 

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  • It is odd and makes me question the qc of the Parts used, in particular the voice coil.
  • I would say it is far more likely due to adhesive or whatever damping material they use to suppress the breakup. 
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  • Does the 4.7K blip show up on the impedance sweep?
     John H, thanks to JP I did get that email
  • One of my two matches the blip seen on the PDF over at PE. The other does not. I posted screen grabs on the other thread I started on these. I am re-posting it here. 

    There is a difference, and it correlates with the differently measured top end of the two samples I possess. 

    I hesitate to call it a defect because it plays nice, and below 4K they are very close to identical.

    I may try and do some different testing this week to see if I can pinpoint something, but the distortion, FR, and impedance curves do not show anything obvious.

    For the record, I have seen similar disparities in metal cone drivers in the past - but this is the first time I have seen an impulse measurement do the watusi like that. 

    I will do a full physical examination of the two drivers, and maybe request PE send me a third driver to see what that performs like. With my luck, however, it too will differ and down the rabbit hole I go.
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  • Remember the oil can debacle? I wonder if there is a tiny gluing issue on the dust cap, when combined with break-up is creating a perfect storm at 4-5k?
  • That is a very good possibility.
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  • I think I'm going to give the DSA175 a try. 
     John H, thanks to JP I did get that email
  • JR, I saw over on the other forum you said you are going to use rope caulk to damp the frames.  Have you done that before?  Any concerns about it coming loose?  

    I was considering using hot glue.  A couple of sticks per driver should add some mass and damp the ringing.  Fairly cheap too.  A quick wipe down of the frame with some windex first and the hot glue will stick forever.  Just a thought.
  • That's a good idea.
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  • FWIW Inhave been using rope calk, or "permagum" as it is known for years. Never had any fall off. What is good about it is its density, and ability to absorb vibration because is viscous. 

    Silicone adheasives will have a similar effect but isn't as dense and has some major off gassing when applied, and hot glue can harden into basically plastic over time, which can shrink and fall off since it CTE is very different from the metal it attaches to and has little elasticity. 
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