A Sensitive Speaker

Discussion in 'DIY' started by ultrabike, Mar 1, 2019.

  1. ultrabike

    ultrabike Measurbator - Admin

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    I was not sure where to put this since I have no current intention to build this. But you never know. If anything, it serves as a way to document in case I change my mind.

    Lately there has been a lot of talk about big and sensitive speaker builds. This because it is felt that these speakers are more linear and have much higher dynamic range than smaller less sensitive ones. I believe there is some truth to this. But for me the picture was incomplete.

    So I decided to design a large speaker with relatively high sensitivity.

    Right of the bat I found that it is hard to find even "pro" woofers with more than 101 dB sensitivity. Here is a list from Eminence which includes 18" monsters:

    https://www.parts-express.com/pedocs/buyer-guides/eminence-loudspeaker-selection-guide.pdf

    However, it is not hard to find a silk dome tweeter half-assed horn loaded that will reach 98 to 99 dB sensitivity for next to no $:

    https://www.parts-express.com/peerl...dymium-tweeter-with-waveguide-4-ohm--264-1390

    In general, I've found that tweeters exhibit much higher sensitivity than woofers, even w/o consideration for baffle step.

    Anyhow. I also feel two way full range speakers fall behind in the mid-range, and so I decided to design a 3-way. This is what I felt seemed like a nice mid:

    https://www.parts-express.com/emine...-sealed-back-midrange-speaker-driver--290-661

    It's got the sensitivity, and is sealed, which means there is no need for a mid-range dedicated internal box.

    Here is where it gets interesting. For the low frequencies I found this for little $:

    https://www.parts-express.com/goldwood-gw-1258-12-pro-woofer--290-382

    The Goldwood is not only an inexpensive 12" PA. It may be able to cover sub-bass with high sensitivity. There is a catch, and I'll talk about it later as we go along.
     
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  2. ultrabike

    ultrabike Measurbator - Admin

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    So here is the Goldwood + Eminence + Peerless design:

    1) 2x ports 3" diameter each, and 2" long in a 200 liter box for 33 Hz F3.

    Port.PNG

    2) Box design below is 17" (W) X 45" (H) X 20" (D) using 0.75" MDF. Baffle step calculated and to be added to crossover design.

    Box.PNG

    3) Tweeter 3rd order cross over and composite response connected in positive polarity with mid 95 to 96 dB sensitivity:

    XoverTweeter.PNG

    4) Mid range 2nd order HP and LP with a notch filter for the lower mid range region which exhibits some resonance due to HP filter.

    XoverMidrange.PNG

    5) Woofer 3rd order LPF

    XoverWoofer.PNG

    Cross over points are 350 Hz and 4500 Hz, and a relatively flat response from 33 Hz to 17 kHz. Sensitivity is around 96 to 98 dB.

    Impedance is a bit on the low side, but perhaps doable:

    Impedance.PNG


    Here is the catch: The Goldwood woofer xmax is 2 mm. And at high SPL (120 something dB) this is the expected excursion:

    Excursion.PNG

    At 200 Hz we run out of xmax. So 12" of nice sensitivity or not, this is not going to be very linear when pushed hard. The cheap 12" PA woofer is going to run out of gas.

    For a home application, this limitation may not be problematic. But this design will probably not qualify for high power PA applications.

    Furthermore, the 2 mm xmax limitation may mean this woofer is not all that linear (reduced operating region). This is why this costs $43.
     
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    Last edited: Mar 2, 2019
  3. ultrabike

    ultrabike Measurbator - Admin

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    A much better woofer for this is the $230 Eminence Kappalite 3015LF-4:

    https://www.parts-express.com/emine...4-high-power-neo-15-subwoofer-4-ohm--290-4520

    This 15" woofer can push a lot more air linearly, not only because it has 3" more of diameter. It has a 10 mm xmax.

    Here is the port design, using recommendations from Eminence (https://www.parts-express.com/pedoc...palite-3015lf-4-enclosure-recommendations.pdf):

    1) Port using 183 liter box using 4x ports with 4" diamter and 10" long. F3 is 35 Hz, and F10 is a healthy 29 Hz.

    Port.PNG

    2) Here is the modeled excursion which agrees well with Eminence numbers, and agrees well with the suggestion to implement a sharp 35 Hz high pass to protect the woofer (10 mm excursion is exceeded below 35 Hz at max SPL around 120 something dB shown above in modeled port response) :

    Excursion.PNG

    3) For completeness here is the cabinet design at 19" (W) X 42" (H) X 18" (D) using 0.75" MDF:

    Box.PNG

    4) Here are the cross overs with mid range and tweeter connected in negative polarity relative to the woofer (sensitivity of the combined response is also about 96 to 98 dB SPL):

    XoverTweeter.PNG

    XoverMidrange.PNG

    XoverWoofer.PNG

    Not much different from the Goldwood design.

    5) Impedance:

    Impedance.PNG

    In both designs (Goldwood and Eminence) the tweeter is the one that drops to about 2 ohms, and may be a difficult load for high Z amplifiers. Using a different tweeter could be used if this is a problem.
     
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    Last edited: Mar 2, 2019
  4. Zampotech

    Zampotech Friend

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    Pay attention to the products of the Siberian factory "NOEMA"

    http://noema.ru/catalog/55


    [​IMG]

    [​IMG]


    They produce professional speakers for cinemas. On one speaker it is possible to make an acoustic system in the form of a shield. The speakers have high sensitivity and almost cover the entire sound range.
     
  5. ultrabike

    ultrabike Measurbator - Admin

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    Haven't looked at those.

    Note that part of the story here is that, based on what I'm seeing, woofer size maters.

    But xmax also seems to mater.

    It means you can push the high sensitivity design to higher SPL with out running out of excursion at high SPL (particularly in the bass area): A true PA speaker with a healthy linear operating region.

    It also goes to show what you are paying for. I've heard a lot of "are you comparing this cheap speaker with that expensive one?" bullshit. That is fucking noise. Folks are much better served when given clear reasons why a particular speaker costs more than others, other than "it's more expensive so it most be better".

    I have no room for these though. If anyone wants to make these designs are reality, you are more than welcome to do so.
     
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    Last edited: Mar 2, 2019
  6. Zampotech

    Zampotech Friend

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    Yes, the speakers are large. Their size is up to 14 inches.

    The speaker system will also be very large.

    My friend made a speaker system in the form of a horn on this speaker. The sound is amazing, but the dimensions are very large. But his amplifier 2A3 appeared the volume and bass.
     
    Last edited: Mar 2, 2019
  7. ultrabike

    ultrabike Measurbator - Admin

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    BTW, the small speaker I designed will run out of xmax before the modeled max 110 dB SPL:

    Excursion.PNG

    But note the operating range of this speaker is from 70 Hz and up. At 110 dB SPL, excursion peaks at 100 Hz @ 20 mm. My guess is that probably the small speaker cannot do more than 97 dB SPL before running out of range:

    110 dB - 20*log10(20mm/4.6mm) = 97 dB.

    For the Goldwood design above, following the same wild ass guess this is probably the max we may expect:

    124 - 10*log10(18mm/2mm) = 105 dB.

    The Eminence Kappalite can do 124 dB w/o problem in its operating range.

    The Goldwood and the Eminence designs will require a ton less power to drive (about a good 20 dB less).
     
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  8. ultrabike

    ultrabike Measurbator - Admin

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    Yup. As mentioned above, I expect these 200 liter behemoths to be about 20 or more dB easier to drive than small home theater monitors and micro monitors.

    Regular speaker towers may go up to 90 dB or so sensitivity. So these will be about 8 to 10 dB easier.

    Note full horn loaded tweeter and mids may give you > 110 dB sensitivity. But even 18" woofers don't usually go that high. Unless I'm mistaken, one would need like 3 or 4 of those to catch up to the horn.

    4x 18" drivers is a clear sign of mid life crisis.
     
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  9. Poleepkwa

    Poleepkwa Friend

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    @ultrabike I am still waiting for the "UltraB" Coax design. 15" incher. Make it happen!
     
  10. ultrabike

    ultrabike Measurbator - Admin

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    LOL!

    I'll see what I can do.
     
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  11. ultrabike

    ultrabike Measurbator - Admin

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    Anyhow guys. Hope you guys find these posts interesting. I certainly learned a bit going through this.
     
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  12. dmckean44

    dmckean44 In a Sherwood S6040CP relationship

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    Horn loading a single driver will get you better results anyway.
     
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  13. Poleepkwa

    Poleepkwa Friend

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    It is always fun to see what you come up with.
    OT, do you have any suggestions that would be good DIY speakers for Dolby Atmos surround purposes?
    I assume the requirements would be about 6”, small profile and easy too mount on the roof. A wide and smooth dispersion would probably also be a benefit.
     
    Last edited: Mar 2, 2019
  14. atomicbob

    atomicbob dScope Yoda

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    Here is my favorite 18 inch sub:
    https://bagend.com/product/el-18a-2/

    A quad of these driven by Crown I-Tech 5000 moves buildings. Literally. Scares the hell out of the inexperienced cubicle denizens when the acoustic lab lights off a really big simulation.
     
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  15. ultrabike

    ultrabike Measurbator - Admin

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    I honestly haven't thought much about forward/up firing speakers for surround. I'm happy with 5.1.

    For satellites, I will make small speakers like the ones I made before, but with a different profile to lie as flat as possible against the wall and with a -15 degree tilt down (to mount a bit high). The woofer is the same ND91-4 3.5" driver for dispersion, 70 Hz coverage (will cross to 80 Hz but like some headroom), and matching to the fronts.
     
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  16. Priidik

    Priidik MOT: Estelon

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    Both woofers have high-ish Fs.

    Here, imo, even better Eminence option: omega-pro-18a
    Low Qts, low Fs, high VAS, small mms for size. Your intended box is anyways huge already, why not get a 18''?
    Compromise with very light cones like these tends to be some breakup in bass.
    Precision Devices make also light coned speakers that don't show much breakup down low in impedance graph.
    I don't know about their availability in States, though.

    What ever I have simulated, over 95dB/W/m eff full range speaker means 150L - 200L box and 18'' woofer.
    Eventually it's about the volume of air being moved, given same size box with same Fs driver the low bass quantity is very similar among them. It's being produced in large bulk by the port anyways. Getting extension by increasing driver Qts probably compromises quality.
     
  17. Poleepkwa

    Poleepkwa Friend

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    No tilt needed according to Dolby Atmos recommendation. That simplifies building and mounting quite a bit. This is in regard to height speakers mounted on the roof and not attached upwards firing ones.
     
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  18. ultrabike

    ultrabike Measurbator - Admin

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    A driver with higher Qts is not compromised in quality. It is just a different driver that can do a better job at some things and worse job at others.

    The Kappalite 3015LF-4 can do sub-bass better than the Omega-Pro-18A from what I'm looking at.

    Here are the simulations for Omega-Pro-18A using recommended enclosure:

    Port.PNG

    Looks similar to the Kappalite, but it runs out of xmax sooner in the subbass region sooner:
    Excursion.PNG

    The Kappalite seems also a bit more smooth to me.

    But both should work fine in a 200 or so liter enclosure. I just fail to see why I should pick the Omega over the Kappalite for the project described here based on specs and simulations, as opposed to Qts on it's own.
     
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  19. ultrabike

    ultrabike Measurbator - Admin

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    Yes. Like the good 'ol Klipshorn (which BTW uses a 15" driver). 105 dB of spec'ed sensitivity on that one. Funny coincidence it uses the same crossover cut offs as the designs in this thread.
     
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  20. dmckean44

    dmckean44 In a Sherwood S6040CP relationship

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    It gets harder to design horn loaded 3-ways because it's hard to find mid-horns that will behave well below 850hz so you need to find woofers that will perform adequately from 35hz to 1100hz.
     
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