DIY Cheap Three-Way Speaker with 15" Woofer

Discussion in 'Speakers' started by purr1n, Dec 11, 2022.

  1. purr1n

    purr1n Desire for betterer is endless.

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    Because a few people asked...

    [​IMG]
    [​IMG]

    You guys already know many of the reasons behind a speaker this like. Before pressing GO, please be reminded that such speakers will likely not suit modern audiophile tastes. In fact, they are likely to offend modern audiophile sensibilities because they use non-coated paper drivers used in the mids and lows. I like paper drivers because they hit fast. Nothing is for free however. Paper drivers decay slower than plastic, metal, exotic material drivers.

    The ideas behind this were low distortion/high-SPL, high-efficiency, a lively immediate fast punchy sound, the ability to put them against a wall and not in the middle of the room (to avoid wives and children thinking you are the loser kind of audiophile at age 55 and leaving you). The downsides are lack of ultimate bass extension (37Hz -3db), ain't small, and what was just said above: poor decay characteristics.

    The restrictions I put upon myself: be as cheap a possible. It's easy making a good sounding speaker using very expensive parts. This is called spending money to solve a problem. It's challenging making a speaker to cost. Did I succeed with what I sought out as my vision? Absolutely and even more. This project exceeded my expectations. I was further convinced I had reached my goals when I saw Tony (from Schiit California) cranking up Tool at 105db+ and when Evan (from Schiit Texas) asking me if he could permanently borrow them.

    The drivers chosen for this job are as follows:
    • Eminence Kappa 15LFA 15” Woofer, retail price $130
    • Eminence Beta 6A 6.5” Midrange, retail price $65*
    • Dayton Audio RST28F-4 1.25” 4-Ohm Fabric Dome Tweeter, retail price $37
    *A better midrange would have be the Faital 6PR122, but this part at $157 belows the "cheap" aspect out of the water. FWIW, I did initially built the speaker with this midrange.

    The Dayton was the only tweeter that had the voltage sensitivity requirements required so I wouldn't have to pad down the woofer. It does this by cheating with 4-ohm impedance and 1.25" dome. The bigger dome will have poorer dispersion characteristics. Tradeoffs ya know.

    The design goal for the crossover network was to use a minimum of parts. Lively sound means using a minimum of crossover parts. I've since had some ideas to improved on the xover - more later. This approach is very different from that of say GR Research, which is to make everything perfectly flat on-axis, or to appeal to the ASR objectivists. There will be imperfect frequency response. Note that is is possible to flatten the frequency response to perfection with the use of more xover parts, but this is not what I wanted to do here. I feel that more xover parts results in a deader sound. Again, tradeoffs. It's is still good enough that one doesn't need to put their head into vice.

    The entire package uses x4 inductors, x4 caps, and x1 resistor per speaker. Here is a rough frequency-response taken in-room with the speaker a mere 4" from the back wall. The microphone is aligned at the level between the tweeter and midrange cone. The midrange is where is the intended listening height (think low couch or sofa). Note that this measurement was without the resistor to pad down the tweeter.

    [​IMG]

    The cabinet is 7.5 cu.f ft. Ports were x2 4" diameter. Port frequency was set to highish 38Hz. I could have gotten deeper bass extension with a lower port frequency, but neither my wife nor I did liked the results. The bass just ended up sounding drier and less punchy. Sometimes it's best to follow ears than box theory or pure measurements. We can see the room I put the speaker in has room modes at 70Hz and 110Hz along with a null at 85Hz. These things cannot be avoided in a room. They exist even in fully acoustically treated mix stages with low ceilings. If you are super worried about them, these effects can be reduced a bit by moving the speaker about a foot from the back wall or moving them to a room with cathedral ceilings.

    Will post xover stuff next.
     
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    Last edited: Dec 11, 2022
  2. purr1n

    purr1n Desire for betterer is endless.

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    All crossover parts were purchased from Parts Express.

    x2 Jantzen 6.8mH 16 AWG P-core DCR = 0.30-ohms
    x1 ERSE 1.1mH 18 AWG
    x1 ERSE 0.22mH 18 AWG
    x2 Audyn (Red) 33uF 400V Poly Foil caps
    x1 Audyn (Red) 3.3uF 400V
    x1 Audyn (Red) 12uF 400V

    x1 1.0-ohm 10W wirewound resistor (could use a better GR-Research approved part here).


    Code:
    
    Woofer
    
    -----6.8 mH--------------     (+)
                        |
                       33uF
                        |
    
    
    Midrange
    
    -----1.1mH------------------33uF----------------    (-)
                        |                     |
                       3.3uF                6.8mH
                        |                     |
    
    
    Tweeter
    
    ----12uF------------------1Ω------     (+)
                        |
                       0.22mH
                        |
    
    
    Notes:
    • Can probably get away with slightly higher DCR part in the woofer section
    • Can get away with much less expensive electrolytic cap in the woofer section
    • Can use a better cap than Audyn red in the tweeter section.
    • Can probably stick a zobel in the woofer section to make the xover slope more effective (it has to fight against rising impedance) to prevent even less woofer bleed in (tighter more modern sound), but this will require a redo of the other parts.
    • Move tweeter and midrange closer together
    • The midrange is offset behind the tweeter, thus moving the sweet spot down to where one's ears are at with a low couch. It's probably best to align midrange and tweeter on the same plane. Play with the location of mid/tweeter up and down for the correct vertical sweet spot.
     
    Last edited: Dec 11, 2022
  3. purr1n

    purr1n Desire for betterer is endless.

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    The above won't get you totally there. The effortless bass and thunderous physicality, yes...
    The Sansui E138 or JBL 4333 types use horn loaded compression drivers in the mids and highs. The Dayton tweeters can pull off that tactility, but the biggest missing piece will be the replace the 6" paper mid with a suitable 1" compression driver. You'll then get the estat speed with dynamic physicality of the E138.

    Maybe I should get together with @CEE TEE at Nitsch to bring back those old school blue baffle JBLs.
     
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    Last edited: Dec 11, 2022
  4. Abhishek Chowdhary

    Abhishek Chowdhary Friend

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    IME, while large drivers generally do scale and have this capability to pick smallest of bass dynamics, the liveliness and vibrancy are much to do with speaker as a whole. Many of the older 15" Tannoys have sounded rather restricted.

    The lens on some of the JBL models also is an effective component. Removing it makes the treble a bit too direct but does gain clarity. With the lens in place that 1" driver sounds like a much larger unit
    Recently borrowed an old Pioneer with those small flat woofers and lens thing on the tweeter. Looks very cheaply built, yet it annihilated my Omega Grande 6. Omegas did sound richer yet uninvolving. The lifelessness has been a major complaint with so many speakers.

    While we were demoing the EC138, switched to a large floostander with Acuton White shell like drivers, said to be very expensive. While couldn't fault the acuton build in terms of FR, it was all there . Yet it couldn't extract the ambient information. Was quite blunt vs the JBLs
     
  5. JK47

    JK47 Friend

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    I spy with my little eye a vertical USB-C port on the MB… Anxious to compare with my Modius E.
     
  6. philipmorgan

    philipmorgan Member of the month

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    @purr1n: Did you build a little sealed sub-enclosure for the midrange?

    ---

    It occurs to me: Eminence and Dayton should get a freaking golden schlong for continuing to make good stuff at decent prices. I know the schlong award is product-specific, but still. I admire theses companies for not going to the dark side even thought they probably could have.
     
  7. purr1n

    purr1n Desire for betterer is endless.

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    Absolutely not!

    Part of the reason was to test whether it a separate mid cab made difference since the JBL 4698 I now use as instrument cab actually does have a sealed mid cabinet. I shoved a cut up pillow behind the mid instead. The other reason is that I wanted the mid driver venting into a large of volume as possible to minimize any damping for snappy attack transients. Large cabs let us get away with less damping compared to small cabs. This was a chosen design approach / philosophy, for better and worse. Small cabs seem to require heroic bracing and massive internal damping materials - think Magico. Again, it's about tradeoffs.
     
    Last edited: Dec 12, 2022
  8. androxylo

    androxylo Acquaintance

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    You forgot to tell how this f** b**ch sounds...
     
  9. androxylo

    androxylo Acquaintance

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    I have no clue - but I have a stupid idea - is it easier to build a compact 2-way with cutoff around 50 Hz and then a separate single subwoofer in a large box for 30-50 Hz, also power it from a separate amp. This won't be more expensive because you will end up with only one low freq driver and box. And it is sooo much easier to build a 2-way...
     
  10. ultrabike

    ultrabike Measurbator - Admin

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    Has been a long time since I posted, but this old thread is awesome.

    Not for the apparent objectives of this build, which includes high sensitivity. The midrange was selected for it's sensitivity: 94dB 2.83V/1m. So the build is likely not configured for the driver to go down to 80 Hz. Likely the large woofer covers frequency areas that are important for sound stage.

    Reading through the thread, it appears that the mid-woofer is not sealed and vents to the larger cabinet which I believe will result in a natural roll off of the lower frequency that the 15" woofer will pick up. This is something I didn't think about before, but likely would work great in larger cabinets like this one.

    Of note, the crossover only has one resistor (and a 1 ohm in series at that with the tweeter). This is very impressive.

    A 2.1 approach would cover very different design goals.
     
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    Last edited: Oct 2, 2024
  11. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    because I can build anything, but can't read/understand much... can someone please do a quick sketch of the above crossover into a format like this?:
    [​IMG]
    For whatever reason, I just can't grasp the original schematic (again... I'm not smart)
     
  12. purr1n

    purr1n Desire for betterer is endless.

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    It's design goals:
    1. A compact 2-way with a small woofer won't have the efficiency of a 15" woofer. Most subwoofer drivers also tend to suck at efficiency, unless one used 15" JBL / Selenium / B&C types (think BIG Cinema subs)
    2. I wanted a "throwback" sound. Think your dad's (or grandpa's) old stereo from the 70s. Think Boogie Nights Buck trying to sell the TK421*
    3. High SPL. 50-500Hz sounds a lot better (low distortion) from a 15" woofer than from a 6" woofer. It's something that needs to be experienced. https://www.superbestaudiofriends.o...-big-woofer-club-why-big-woofers-matter.9725/ (I think the thread eventually descended into stupidity)
    4. There is a certain beauty to the sound with a dedicated mid. It's different two-ways for sure.
    Yes, two ways easier to design.

    *Two guys from Computer Audiophile who heard them hated them. These are not a modern sound with metal / composite drivers. Nor do they cost $55,000 (which It think is the going rate of speakers for the average Computer Audiophile dude). I think they said it reminded them of their dad's speakers. I was thinking "exactly". A guy from the Schiit factory in Corpus loved them, so he snagged them.

    One of the Schiit guys at the show was cranking Tool at 100db. This is how they are supposed to be used. Also cinema applications at spec volume levels. It's rock on or Optimus Prime exploding stuff. Punch, dynamics, heft, tactility. The highs even have this way to reaching out and hitting you. Paper drivers, so again, not clean, slower decay, compared to modern drivers. Some dome because I hate metal or hard tweeters (even though do they some things really well). Personally, I thought girl with small band stuff worked great. Sarah Bareilles Manhattan (live) - really enjoyed that.
     
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    Last edited: Oct 3, 2024
  13. purr1n

    purr1n Desire for betterer is endless.

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    One thing the cab maker screwed up on was too large a distance between tweeter and mid. The result is that the ideal vertical listening position would be on low couch or slightly slumping on a regular couch. Turns out it's perfect for me. However if one wants to build this, determine the listening height and put mids and tweeter as close together as possible with the height right between them.

    The tweeter XO circuit, with the 1-ohm resistor before the tweeter, this raises the overall impedance, so smaller cap value. needed. Really conscious of keeping components to a minimum and cheap.
     
    Last edited: Oct 3, 2024
  14. Thad E Ginathom

    Thad E Ginathom Friend

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    fig beech is a very expensive veneer! with a very special sound. Sort of... slightly sweet and syrupy.

    Like your dad's speakers. Well, my dad wasn't into music, and the only thing he had was a radiogram, which I appropriated. But later in life, sure I knew other dads with systems I'd love to this day.
     
  15. purr1n

    purr1n Desire for betterer is endless.

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    upload_2024-10-3_16-23-8.png
    note inverted polarity with mid
     
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  16. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    That's what confused me so much originally and I decided I just had to ask... THANK YOU
     
  17. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    @purr1n, curious on the port length you ended up with. I used a couple online calculators to make sure I got one long enough (I plan to cut to find the length I like best), but using a 38Hz frequency the 3 online calculators I tried gave three completely difference answers. One gave me under 4" long, one was 59" long (??) and the third was over 200" long (!!!).

    Obviously the last 2 aren't correct, but now I'm not sure where to start... (I want to put these in my shop... the 4" from the wall but still sounds good when loud is a main selling point)
     
  18. uncola

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