Arctic Ice (a speaker design)

Discussion in 'Archived Threads 2001-2004' started by Abdul Jalib, Aug 21, 2002.

  1. Abdul Jalib

    Abdul Jalib Stunt Coordinator

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    Here is my design, submitted for your critique...
    Arctic Ice
    [​IMG]
    You are looking at front and side views. The black section on top is ribbon, the circle in the middle is the woofer, the baffle is acrylic, and the black box at bottom is the amplifier (not actually part of the speaker.)
    Arctic Ice are dipole speakers through and through, with 16" of dipolar ribbon for crystal clear highs and mids and a 12" dipolar woofer for bass. The ribbons are dual 4x8" push-pull planar Neodymium panels with award-winning sound. The special low noise woofer is mounted on a flat open baffle made from 1" thick transparent acrylic. The triangular shape offers a more smooth frequency response compared to circular or square designs. The relatively small size of the baffle is designed to avoid the problems with resonance of higher frequencies within its operating range. The flat baffle design is not subjected to the forces that boxes must endure, and acrylic is very resistant to resonance for this application.
    Monopoles have their fans, but the advantage of dipolar bass is more focused sound waves and less wall reflections, making for crisp and pure bass. The ribbons have excellent imaging, with the dipole adding a little envelopment to the sound.
    With a 24 db/octave Linkwitz-Riley crossover at 166 Hz, the phase is consistent throughout, aiding by a slight tilting of the baffle. This 2-way design is not a compromise. The wide range of the ribbon section, 166 Hz to 20 kHz (-3 dB), makes it possible to cover the lower range of 166 Hz down to nearly 20 Hz with just a single woofer.
    [​IMG]
    Biamping is not only the best way to drive Arctic Ice... it's the only way! This is an active crossover design, positioning the crossover before the amplification for the best possible sound. The pre-outs connect to the crossover, and the low pass output of the crossover is subjected to equalization. Bass equalization is always a good idea to compensate for room response, but with dipolar woofers equalization is a necessity to compensate for their inherent -6 dB per octave roll off. With equalization, the response curve will be flat down to nearly 20 Hz.
    The amplification for high and low needs to be done by two separate amp channels. The two amp channels could be left and right channels of the same stereo amp (vertical bi-amping), or all the highs could be on one multi-channel amp and all the lows on another multi-channel amp (horizontal bi-amping), or each channel of amplication could be provided by a monoblock. Because the woofers have dual voice coils, you can even go for a 3-channel amp, using one channel for each voice coil, which is probably a good idea for more SPL. For monoblock or vertical-biamping, the amp(s) can be placed on the foot of each speaker. This provides physical stability to each speaker, and you can show off your tasteful choice of amplifier through the transparent acrylic.
    Arctic Ice is designed to be used for every speaker in your home theater and run full range. No dedicated subwoofer is necessary. A single Arctic Ice speaker does not pump out anywhere near the SPL of a subwoofer, but put together 5, 6, or 7 Arctic Ice speakers run full range for your home theater and that will be some bass! A center channel version has the ribbon pannel mounted horizontally so that you can mount it underneath or on top of your TV. (For shielding, um, a big slate of lead?)
    Specifications:
    Frequency response: ~20 hz to ~20kHz (-3 dB) (maybe a bit less)
    Dimensions: irregular, 37x24x16" (HxWxD), 1" thick baffle
    Weight: 25 lbs (?)
    Price:
    $85 Monsoon MM-702 (two Sonigistix planar panels, cheaper direct)
    $145 Adire DPL12 12" dipolar woofer
    $30 Marchand XM1-A 24 db/octave L-R crossover @ 166 Hz
    $12 OPA1234 Op-Amp upgrades
    $90 Marchand WM8-A BASSIS bass equalizer
    $100 Acrylic slab
    $1 wood tie from Home Depot (to join planar panels)
    $10 miscellaneous (solder, wire, etc.)
    ------
    $473 each, $946 per pair
    For the whole set of speakers, you'll also need a power supply (e.g., Marchand PS10 for $50) to power the crossovers and equalizers, and it would be nice to have a big box with 7 RCA inputs and 14 RCA outputs to house the crossovers and equalizers. Whatever amplifier you choose needs to accept unbalanced input (RCA), because that's what the XM1 outputs.
    Another concept...
    Arctic Narwhal
    [​IMG]
    The Narwhal uses a whale of a subwoofer as its woofer, but I haven't finished designing it.
     
  2. Jack Gilvey

    Jack Gilvey Producer

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    Looks neat, but I think bass will be quite limited given the tiny size of the baffle (the 6dB/oct. rolloff will likely begin well over 100Hz). You'd need so much eq the woofer might be bottoming before reaching useful levels. Even with 5 of them, you might only get to the SPL of a single vented DPL12, and maybe not even that since they're spread about the room.
     
  3. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    $85 Monsoon MM-702 (two Sonigistix planar panels, cheaper direct)

    Correct me if I'm wrong but are you planning on using PC speakers in your design?
     
  4. Robin Smith

    Robin Smith Stunt Coordinator

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    It seems like that is what the design calls for...
    The Monsoon's spec'ed are 4 X 8 inch dipole radiating planar transducers. In the Monsoon package they are amped by a "49 Wmax, 35 Wrms" amplifier.
    I own the Monsoon MM-2000 4 speaker + sub set, which is Monsoon's top of the line computer speakers (and are driven by a 60W amp) and they do kick major ass (with a 100W subwoofer featuring a 6.5 driver and two 6.5" PRs!)
    However, they kick ass as a PC speaker. I would fear they would not suffice for HT use. Plus, given their size, they tend to be very directional, which would not bode well for a larger home theater where you generally sit further from the speakers than you would in a PC environment.
    What led you to select these speakers in particular? Have you tested them in the larger scale HT environment to have confidence they'll work.
    I am no speaker designer or expert, and I admire your ability to get as far as you have with the design process cos I could never do it. I am simply asking some curious questions.
    Monsoon themselves do not even use these planar transducers in their home theatre system speakers:
    http://www.monsoonaudio.com/ht_demo_fpf1600.htm
    Thanks
    Robin Smith
     
  5. Abdul Jalib

    Abdul Jalib Stunt Coordinator

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    I used Brian Steele's spreadsheet to design the size. The BASSIS bass EQ can supposedly provide a 25 dB boost (no lower than 15 Hz), plus it can dampen by a few dB too. This gives me about 30 dB of potential EQ, which is enough offset five octaves of -6 dB/octave drop. It actually drops off at a -12 dB/octave rate towards the end, so that's why I'm still not sure I can make it to 20 Hz. I'm also unsure of how much of this potential gain I can get without some form of distortion. Looking at the spreadsheet results, I feared I might have to go twice as big to make it to 20 dB, but there are so many uncertainties that I decided I will just have to do some prototypes and see what happens.
    One thing I'm confused about is the effective diameter of a triangle for dipole baffle use. Is the effective diameter the largest circle that will fit entirely within the triangle? If so, that's pretty small. Or is the diameter the length of a line from one end to the other of the triangle passing through the center of the woofer? That's considerably bigger. My hope is that the three "fins" provided by the triangle will boost the deep bass response to partially offset the -6 dB drain.
    Definitions for those unfamiliar with dipoles:
    Fp = Frequency at which the response peaks
    Fe = Frequency at which response is equal to infinite baffle
    Above Fp, the response tends to become chaotic as resonances take hold. Above Fe, the frequency response rises to a peak of +6 dB at Fp. Below Fe, the frequency rolls off at -6 dB per octave.
    Brian Steele's site above has a chart of baffle size, Fp, and Fe. One line has Diameter=0.57m, Fp=600 Hz, Fe=200 Hz. I was shooting for a hair smaller than 0.57 m diameter, so that Fp would be safely at two octaves above the crossover of 166 Hz. My other goal was to get close to 20 Hz for the unequalized -30 dB point under the crossover, assuming I can get a net of 30 dB equalization from the BASSIS.
    For overall SPL, the dipole 12" woofer just has to keep up with the two ribbon panels. I'm hoping that with an intense infusion of power into each of the voice coils of the woofer I can get the SPL up to decent levels. I plan to have 7 speakers. I agree that even if each can do 1/7th the job of a good subwoofer, then it's still not clear that it will be good enough. If the bass management splits the LFE evenly, then there will be some cancellation, and if the bass management uses only the mains for LFE then that won't be enough. Maybe a subwoofer will be required, but it would still be nice to have near full range speakers.
    The Adire website lists a spec of "Pmax: 650W per IEC 268-5" for the DPL12. IEC 268-5 is a pink noise standard, I gather. So how much power can I safely feed each of the 8 ohm voice coils?
     
  6. Abdul Jalib

    Abdul Jalib Stunt Coordinator

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    For its award winning RM40 speakers, VMPS uses Sonigistix planar ribbon panels that are extremely similar to the the Monsoon computer multimedia panels. For a full discussion see the thread Dual planars for $108 shipped on AVSForum, or do some searches on Harmonic Discord or maybe a picture of a Monsoon panel over a VMPS panel will convince you. The RM40 uses 4 of these ribbon panels, but the highly regarded RM1 and RM2 use just two ribbon panels, and the highly regarded 626R monitor uses just one ribbon panel. The VMPS website says:
     
  7. ThomasW

    ThomasW Cinematographer

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    1)The planars need a baffle or the front and rear waves will cancel

    2)The planars lack adequate high frequency output, they roll off above 10Khz. The VMPS designs that are using this planar are augmenting it with supertweeters.

    3)The planars can't be operated safely alone down to 166Hz. The VMPS designs that use this XO point are augmenting the planar's output with a cone driver at 500Hz

    4)The vertical dispersion of the design will be limited to a height of 16"

    5)The single 12" won't have adequate output

    6)Attempting to use 25db of bass boost is folly

    7)A triangle isn't the proper shape for a dipole baffle it will only boost a single frequency.

    8)A single Marchand PS 10 isn't adequate to power the number of devices you list.

    9)Lead isn't an effective shield against a magetic field, it is however effective against X-rays.

    Let us know when you buy the planars direct. The best pricing I found was $15 ea in lots of 1000pcs
     
  8. Abdul Jalib

    Abdul Jalib Stunt Coordinator

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  9. Bill Fagal

    Bill Fagal Stunt Coordinator

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    Ease up fellas!

    Abdul, I think folks have been applying the acid test to your design instead of the principles of the constructive critique.

    I, for one, think you've got some good speaker feng shuei going here, so be not discouraged. In fact, my next diy stereo pair will almost certainly be dipoles.

    I'm not extremely familliar with the drivers you spec, but I'd say you're designing with good principles in mind. You're already using the dipole spreadsheet, so you've got a useful tool.

    On the bass end of things, just remember that when designing dipole bass you should plan for at least 4x more displacement potential than an equivalent sealed/vented alignment. It might be prudent to go with 6 or even 8x because you're having to compensate not only for the dipole cancellation effect, but also the steep attenuation of the reverberant field (remember that figure-eight polar response?)

    Also remember that a driver's displacement scales with power (or EQ) only to a point where the suspension compliance curve angles up (Xsus) and the BL curve drops off (Xmag) and compression says hello. That point can come pretty quick with a lot of drivers. Also, a dipole bass driver will reach Xmax at low power levels, sometimes rediculously low.

    All this is to say, don't plan on meeting your dipole bass EQ demands primarily with power. Plan on mucho raw displacement. In my own design, I'm looking at 4 x 15" per channel for bass down to the mid thirties, and that may be only sufficient. And I suspect I'll be able to overdrive them with no more than 100W per channel.

    Happy designing!

    Bill
     
  10. ThomasW

    ThomasW Cinematographer

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  11. Dennis XYZ

    Dennis XYZ Stunt Coordinator

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  12. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    I'll critique the artistic design..

    My initial impression is "guitar" because of the long neck and triangular base with single driver. I tend to like loudspeakers with a design that doesn't remind of an every day object.

    The triangular shape at the bottom has angles that causes an imbalance in my impression. In other words, I feel more comfortable looking at a square or circle than I do a triangle. The single thin planar at the top of the boxy Narwhal definitly does not work for me as a design.

    The colors work well, modern, yet doesn't scream out. The baffle-less profile for the speaker is also interesting but I fear the room/placement will have a lot do with how these sound.

    BTW, I'm not attacking your design, but simply stating how I feel towards it.
     

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