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DCS205-4 vs RS225-8, + and -'s

edited December 2019 in DIY

Does a woofer with a phase plug really add any value to a 3-way design?  Seems like a potential for leaking (even more so in a sealed design?), and per comparable radii reduces Sd (ok, not by much but…).  I understand proffered advantages (phase plugs) in a 2-way, however looking for input on woofer selection in 3-way.  Thx.

And, am I nuts for preferring a paper/Kevlar cone over aluminum?

DCS205-4 vs RS225-8

Comments

  • edited December 2019
    The advantage obtained by a plug is an improved motor by effectively extending the pole piece. An extended pole piece allows for greater BL symmetry. There's a side effect of removing the dust cap, which apart from a small reduction in Sd means that there won't be any air compressed between the cone and the pole piece, so the motor no longer needs to be vented. The lack of vent and extended pole provides a larger thermal mass for voice coil cooling. Often higher end speakers with dust caps will have vented motors, as well as holes in the cone behind the dust cap to prevent any air compression.

    Any air leakage you think you have around the voice coil and through the gap between the plug is inconsequential, and only aids to cool the voice coil. Besides, higher cabinet pressures are obtained in a ported cabinet, not sealed.

    The old Dayton Classic is probably a good choice for the bottom end of a 3-way speaker, apart from the visual appearance of course. It'll take the bass abuse much better than the RS225 I think, if you like to get carried away with the volume knob.
    tajanes
    I'm not deaf, I'm just not listening.
  • I built a small 3 way with an RS225 on the bottom. Granted I don't push it hard, but jeez is that woofer effing great.
    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • What about the sd215? 
  • In a head to head rs225 vs sd215; what does each bring to the table?  
  • dcibel – thanks for the info re pole piece vs venting designs / BL symmetry...

    I’ll need to do a bit more noodling; as at first glance the 'higher pressure in a ported vs sealed box' seems a bit counter intuitive, as a sealed design yields a smaller volume box than a ported design, so for the same cone movement…  

  • Physics is wacky stuff.
    rjj45
    I'm not deaf, I'm just not listening.
  • Kornbread said:
    In a head to head rs225 vs sd215; what does each bring to the table?  
    225 is low distortion, higher xmax, better BL/MMS ratio....
    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • Hermnn von…and hence the lower excursion at / near fb (vs most sealed designs)

  • Kornbread said:
    In a head to head rs225 vs sd215; what does each bring to the table?  
    The biggest and really only downside to the RS225 is it can bottom out if you plan to abuse it. Normal levels it’s just fine. I have had an RS225 as the bottom of a 3 way (w/ a scan 10F and Fountek Neo1.0) for some time now on a 100wpc integrated and have never bottomed it. I’ve heard enough stories though to know it to be a possibility. If PE would have done a bumped back plate on those or a suspension that ends softly just before bottoming those woofers would be about perfect for their price point.
    rjj45
  • I recently finished a subwoofer project with my son that uses the SD215.  It produces surprisingly good bass for a $29 eight inch driver.  However it has the cheapest frame of any driver I have ever used.  Thin, flimsy, stamped steel frame with only 5 mounting holes.  You have to tighten the mounting screws with great care or you will warp the frame and it will look terrible.
  • Sorry @tajanes   to take this discussion further off track.  Just my $.02, food for discussion, cannon fodder, errant ramblings ...

    I agree 100%, the metal basket of the sd215 is cheap, very flimsy, and easily distorts just by mounting it.
     
    1mm difference in xmax, according to published specs. and some are saying the rs225 has less xmax than specified.  The rs has a slight +5.1cm² sd advantage and we know the sd215, as has the rs225, has been successfully implemented in a 2-way.

    Did I read somewhere it is more difficult for us to hear distortion the further away it gets from our most sensitive region (1-8k?)?  When used as the bottom of a 3-way is the higher distortion of the sd215 mitigated?  In general, how important is distortion in a woofer used for lower frequencies? 
     
    Guess I am one of those scourges of the neighborhood who likes to feel their music and, on occasion, finds the limits of a quad of rs225p.  They do not bottom gracefully.  Using the same amplification and probably what most would consider way above normal listening levels, I have never heard an sd215 bottom.  Surely they must but they do it without the loud machine gun 'blat' of the rs225p.  If the rs only bottomed as gracefully I could sit back and enjoy the music without sitting on the edge of the couch awaiting that one whack in a song that sends them over the edge and me towards the volume control. 

    Just my ramblings.                          
  • I've often wondered why development of the RS woofers did not include proper soft parts or a bumped back plate. I've also wondered why on the 8" and up they maintained the phase plug when a cap on the pole piece would suffice and allow the motor to breathe out the back plate. 

    The RS are great drivers, but Dayton left some performance on the table that would not have added any cost to them. 

    While I am on a Dayton mini-rant, the DA/DS/DSA/SD drivers all use the same shitty frame. Dayton did address the performance issues of the DS with the DSA line, at least on the 6.5" models that I used, but that frame... When you consider that cast frames are not a roadblock to affordable drivers, you have to wonder what drove Dayton's decision to use a shit frame. 

    Dayton is interesting, I see their product line and say to myself: "Self, isn't that a weird lineup?" Periodically, a forum will go on a "what I wish to see from Dayton" thread, and there will be mention of poly cone RS, high sensitivity midrange drivers, etc - and they introduce that CE stuff lol. 

    Oh well. 

    The DCS subwoofers are great drivers.
    I have a signature.
  • edited December 2019
    OK, how about an 8 inch Esoteric Series?
    I have used their 7 inch ES180TiA-8 in a two-way, but would like an 8 for a 3-way, with its 3in vc, its low Fs,... and maybe a tab bit more Xmax
  • Kornbread said:
    Did I read somewhere it is more difficult for us to hear distortion the further away it gets from our most sensitive region (1-8k?)?  When used as the bottom of a 3-way is the higher distortion of the sd215 mitigated?  In general, how important is distortion in a woofer used for lower frequencies? 

    Maybe "less obvious" to hear, but not inaudible. I would argue that the people that make the statement that bass distortion is inaudible simply haven't heard distortion free bass from a speaker. Not that I can blame them, most speakers produce considerable distortion below 100Hz vs the rest of the spectrum, but there's a few that do pretty well below 100Hz, and let me tell you, it's an audible difference. You start to realize just how much of that deep bass you're used to hearing is actually 2nd and 3rd harmonics.
    I'm not deaf, I'm just not listening.
  • The SD215 is pretty low HD below 100 Hz.
  • tajanes said:
    OK, how about an 8 inch Esoteric Series?
    I have used their 7 inch ES180TiA-8 in a two-way, but would like an 8 for a 3-way, with its 3in vc, its low Fs,... and maybe a tab bit more Xmax
    How about a 10" or 12" woofer? If the intended frequency range is only to about 300Hz, why limit yourself to smaller drivers? Some 4 ohm subwoofers have decent enough sensitivity @2.83V to be used in a passive 3-way design.

    I'm not deaf, I'm just not listening.
  • edited December 2019
    Back to to an old "sponge worthy" favorite.
    While I agree totally w dcibel, and have a RS270 3 way in the queue, the MCM  8 inch is super tasty:
    https://www.newark.com/mcm-audio-select/55-5670/8-die-cast-woofer-8-ohm-rubbber/dp/95Y2936?ost=55-5670&dym=555670&ddkey=https%3Aen-US%2FElement14_US%2Fsearch

    And to continue the PE rant, I'd expect to see "SAVE ONE DAY ONLY - $.13 on this driver!!!!"


    tajanes
    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • edited December 2019

    dcibel,

    My current open back set-up uses dual 12 BR70 beyma's… I’m considering having a bit smaller pair of elephants in the room…  

    Looking again at a 3-way for what a mid can offer to the voice range (and keep the mid/tw crossover out of the 1-5kHz region).  Could use a sub for lowest octave, so thinking an 8in can get towards 40Hz – 60Hz range.

  • rjj45
    just placed the order for a pair of the MCM's, thx for the recommendation
    rjj45
  • Hope you found the 20% off coupon; save2020
  • dcibel said:
    Kornbread said:
    Did I read somewhere it is more difficult for us to hear distortion the further away it gets from our most sensitive region (1-8k?)?  When used as the bottom of a 3-way is the higher distortion of the sd215 mitigated?  In general, how important is distortion in a woofer used for lower frequencies? 

    Maybe "less obvious" to hear, but not inaudible. I would argue that the people that make the statement that bass distortion is inaudible simply haven't heard distortion free bass from a speaker. Not that I can blame them, most speakers produce considerable distortion below 100Hz vs the rest of the spectrum, but there's a few that do pretty well below 100Hz, and let me tell you, it's an audible difference. You start to realize just how much of that deep bass you're used to hearing is actually 2nd and 3rd harmonics.

    Most of the tests are testing specifically for the audibility of distortion which has to be pretty high to pick out on its own as distortion. However, when compared to something that has a lack thereof, there are definitely audible differences even if one doesn't sound particularly like distortion. 
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