Seas A26 kit

Discussion in 'Speakers' started by murphythecat, Dec 12, 2018.

  1. purr1n

    purr1n Finding his inner redneck

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    The Klipsch Forte is a horn speaker. It uses horns on the mids and highs, not mere waveguides. Compression drivers actually need horns, with the skinny neck, flare, and all. It's an acoustic transformer.

    Bass horns require big size to be effective at low frequencies. Therefore not used often or practical, unless in BLH, and even then, not much below 80Hz in most implementations.

    Waveguides are typically the little makeshift horns "lite" used with small dynamic drivers, i.e. tweeters. The small JBL self-powered monitors use waveguides. They don't have a longish neck and flare to mount to a compression driver with a tiny exit of 1-2".

    Let's not redefine horn / compression drivers as waveguide / compression drivers.
     
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  2. purr1n

    purr1n Finding his inner redneck

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    Constant directivity (CD) refers to the horn flare. Many modern JBL pro horns are CD. There are exponential, tractrix, multi-cell, etc. Klipsch uses tractrix. The old Altecs are multi-cell. JBL M2 horns are some proprietary design that bend space and time.

    There is debate about which flare sounds beat. Much of this could be chalked up to implementation, frequency response, etc. Personally I dislike CD horn flares in a home.

    Horns will not roll-off in their operating range / intended dispersion area. The key is operating range, hence why both a mid and high horn are needed for even power/polar response up to near 20kHz.
     
  3. Poleepkwa

    Poleepkwa Friend

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    Exception to the rule? I would guess he is more interested in room friendly designs.
     
    Last edited: Jan 21, 2019
  4. murphythecat

    murphythecat Friend

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    I really do value Troel, but as Marv said, his designs are quite LOW eff. if I am to build a big 3 way, id try to be around 95 db/w so it can at least be driven with a PP 15 wpc tube amp

    My drivers are already selected, the Omega pro 15 woofer, Audax pr170mo mid and a ribbon up top, possibly the hivi rt2ha or maybe a simple dome im not sure
     
  5. Poleepkwa

    Poleepkwa Friend

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    These kinda threads are the highlights for me here on SBAF. A lot of knowledge here, keep it up.

    Would coaxials be classified as constant directivity speakers?
     
  6. OJneg

    OJneg The Most Insufferable

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    No. You can look at the polar responses to tell.
     
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  7. OJneg

    OJneg The Most Insufferable

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    Is there an actual technical distinction between these two outside of size? They seem to operate on the same acoustic principles regardless. Kinda like saying a air coil isn't an inductor if there's no ferrite core, no?
     
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  8. Priidik

    Priidik Friend

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    Waveguide is like 'horn lite'. It's doing the 'transformation' at low frequencies, for example helping tweeter play louder at around 1 kHz.
    Waveguide can also be useful for removing difractions --> smoothing the edges. Some pro monitors are like that, to overcome time alignment geometry caused boundaries.
     
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  9. Cspirou

    Cspirou They call me Sparky

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    He's avoided big woofers but lately he's been doing some >12" woofer builds. I'm counting 8 projects with big woofers and 5 of those were very recent. The Fusion is probably the one most of us mortals would attempt since it's a classic 3-way box.
     
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  10. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    They can be made to be constant directivity. Genelec does that. Overall coaxial is very hard to get right, havent encountered a single diy driver which would satisfy my needs. Genny does it right, so does just about every Andrew Jones design at KEF, TAD and Elac.

    P.S. I recommend checking out Earl Geddes work on directivity and horny compression drivers.
     
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  11. purr1n

    purr1n Finding his inner redneck

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    Horns have throat (skinny part) and mouth. Compression drivers range from 1" to 4" with openings less than 2". The Altec 511B has a 1" throat and is mated with 1.4" compression drivers.

    The horn works like how humans make sound. It's an acoustic transformer and why tiny 1.4" drivers without much excursion can produce high SPL with low distortion. This is stuff you can't do with a 1.25" or even 2" dome tweeter
     
  12. OJneg

    OJneg The Most Insufferable

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    Seems that most any tweeter with a sloped aluminum plate around it could be said to be a waveguide. You could even say the baffle itself behaves as a waveguide, sometimes to negative effect.

    Still not sure when a waveguide becomes a horn....
     
  13. OJneg

    OJneg The Most Insufferable

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    waveguide or horn.jpg
     
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  14. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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  15. purr1n

    purr1n Finding his inner redneck

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    Pretty much.
     
  16. skem

    skem Friend

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    I had looked at this: 15” woofer with horn > 650Hz. I suppose some may say this is pushing both drivers out of their comfort zone. Decay waterfall is what turned me off. I’m curious what you speaker builders think, though.

    http://www.humblehomemadehifi.com/Calpamos.html
     
  17. OJneg

    OJneg The Most Insufferable

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    With capable drivers and 2nd order filters... no problem at all
     
  18. purr1n

    purr1n Finding his inner redneck

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    With 15" drivers, we are good to 900Hz before off-axis roll-off. Most 15" drivers stay flat to 1kHz.

    I believe the Faital compression driver is a 3" diaphragm with a 2" opening. The ones I used on the Altec horns were 1.4" diaphragm into a 1" opening and I crossed them over at 560Hz.

    Compression drivers / horns are incredibly efficient and designed to be used in larger venues. In a home environment, we can get away with "pushing" them more.
     
  19. purr1n

    purr1n Finding his inner redneck

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    As far as waterfall plots, anything below the mids is going to be dominated by the room, unless we have an anechoic chamber and a speaker suspension rig.

    Larger drivers and paper drivers do take longer to decay as there is more energy to dissipate. Lower crossover is better, but as with all things, we try to find the right compromise.

    A kick-ass approach would be woofer, low-mids, and horn highs. JBL used to make stuff like this. 18" woofer + 8" low-mids + horn highs. Unfortunately, the pro-audio mid-range cone drivers are now a thing of the past. Mating a big woofer to just a CD / horn without a mid in the middle is easier and less parts, but the integration isn't as good.
     
    Last edited: Jan 21, 2019
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  20. skem

    skem Friend

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    Super useful response, Marv. Thank you!

    A follow up, then, would be a question about the trade-offs between 2 vs. 3 or more drivers.

    Here’s what I imagine for an answer, but I’d value SBAF’s thoughts. I presume the more crossovers you have, (1) the closer to ruler-flat one can get, but often one can already get close enough with just two drivers and good design; and (2) the less cone-breakup and related distortion from each driver because each operates closer to their sweet spot—but counterbalancing these benefits: (3) you get more phase distortion from more crossover points that might undercut the coherency of the sound at lower frequencies; (4) you may need high-order cross-overs that have more passive components coloring the sound; (5) you have more radiators and thus more spatial incoherence in the sound reducing imaging, and relatedly (6) greater room sensitivity because of more tonally-uneven reflections.

    On conjecture (3) & (4), Linkwitz claimed that phase distortion from a 24dB/octave crossover was inaudible. I question his test method, however.

    Why? I’m familiar with the sound of full-range drivers like the old Walsh F, which, while very limited in bandwidth, also produce wonderfully coherent sound with fantastic stage. Conversely, the array-of-many-small drivers design always lacked imaging unless I was standing 30+ feet away where the angular separation between drivers becomes close enough to be essentially a point source.

    Any of these conjectures seem correct to you? Any other trade-offs I’m missing?
     

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