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Crazy PA Coaxials for Hifi

Chr1

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Using several pairs of Tannoy V12/T12s. Have attached the manual for the earlier i12/T12 model which use identical drivers as it has some measurements. Think they were about $1000 each new, circa 2000. They use the same HF driver as the DMT12/15/215s and some of the current very expensive hifi models. Read various posts on pro-audio forums that the current HP version has a different and inferior HF driver. I paid £350 for one pair and £250 for my second, both in great condition second hand. So a viable budget option for those who like big SPLs and/or small amps. I am using them with three subs. They sound good to me with MathAudio RoomEQ, and I doubt very much I could afford anything better that is capable of high volumes currently.
 

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Prana Ferox

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I'm not sure if these are still available but the 15" in particular looks spectacular:

I have a pair of the 12"s in a box waiting for me to have wood shop access to build the cabinets. Erich says a reorder is not impossible but highly unlikely, due to the costs going up on... everything. Then again the 12's and 15's sold at closeout seem to be very highly regarded by his customers.

General question, why not use a smaller coaxial (5" or so) with a large bass driver under 300hz or so, similar to the Sigberg one in prototype at the moment.

This is not a bad idea and it's fundamentally what the bigger KEFs do.

And you pretty much have to do it with the bigger coax's as well. Generally the LF driver motor trades xMax for efficiency (to keep up with the CD) so even with a big driver you run into excursion limits quickly on the low end. And large excursion on the LF driver acting as the horn leads to IMD anyway so it's not really a road you want to go down.

You then run into the following issues:
- Excursion and IMD become a problem high-frequency enough that the usual 80hz handoff to subs won't save you. You may really need a midbass driver and crossover above Helmholtz. That's a hassle trying to do passively and it reduces the value of using the coax as a point source.
- Because your CD and (now midrange) driver are so efficient you may need multiples of those midbass drivers to keep up, which makes your box even bigger and more expensive. (Again, see the nicer KEFs.)
 
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voodooless

voodooless

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I have a pair of the 12"s in a box waiting for me to Generally the LF driver motor trades xMax for efficiency (to keep up with the CD) so even with a big driver you run into excursion limits quickly on the low end.
Really many of these have > 6mm Xmax and low enough fs to have some serious output for home conditions.
And large excursion on the LF driver acting as the horn leads to IMD anyway so it's not really a road you want to go down.

You then run into the following issues:
- Excursion and IMD become a problem high-frequency enough that the usual 80hz handoff to subs won't save you.
.1mm Xmax will get a 15” woofer as loud at 200 Hz as a 5” driver at 600… that is even without bass reflex, which will lower excursions by about half. That really isn’t that bad. Obviously it’s a trade-off, but so is adding another “way” to the design. When I’m behind a PC again I’ll make some better comparison.
- Because your CD and (now midrange) driver are so efficient you may need multiples of those midbass drivers to keep up, which makes your box even bigger and more expensive. (Again, see the nicer KEFs.)
For PA, probably, for home HiFi, it will probably be enough, especially if you’re planning to use additional sub’s anyway.
 

gy-k

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Of course they're not "time aligned", like the ones from Genelec, Kef, etc. which are most likely are. ..and a cross section drawing reveals the horn profile in the ones without a horn.
 

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gy-k

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The 10" and 12" ones from BMS have a pretty smooth FR. Also their 44mm voice coil compression drivers are specced for a low crossover frequencies, based on that they should work well for a 1kHz crossover.

I was curious how a passive crossover would look like for the 10", gave it a try in Vituix, a naive attempt with not a small number of parts, based on the FR in the data sheet, plus the delay from the mechanical offset for the HF. This was a while ago. Feel free to test the theory :cool:
 

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Prana Ferox

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Really many of these have > 6mm Xmax and low enough fs to have some serious output for home conditions.

.1mm Xmax will get a 15” woofer as loud at 200 Hz as a 5” driver at 600… that is even without bass reflex, which will lower excursions by about half. That really isn’t that bad. Obviously it’s a trade-off, but so is adding another “way” to the design. When I’m behind a PC again I’ll make some better comparison.

For PA, probably, for home HiFi, it will probably be enough, especially if you’re planning to use additional sub’s anyway.

It all depends on what you want to get out of them. There are people who use 15" coax's with CDs for nearfield speakers. There are people who run them open baffle and are clearly satisfied with the power handling. There are people who put them as LCRs behind an AT screen and dump power to them that would melt a dome tweeter to hot slag.

You can look through threads like the KEF R3 thread with people freaking out about the extremely precise positioning of the trim ring, and interpret that to how they would appreciate CD FR behavior when the horn in front of it is moving 6mm back and forth.
 

AwesomeSauce2015

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You can look through threads like the KEF R3 thread with people freaking out about the extremely precise positioning of the trim ring, and interpret that to how they would appreciate CD FR behavior when the horn in front of it is moving 6mm back and forth.
Probably not too dissimilar to this:

If you start at the beginning it shows what happens as they discover this thread.
(lol) :p
 
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voodooless

voodooless

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It all depends on what you want to get out of them.
Absolutely! It’s all just different compromises. You’ll just need to figure out the right one for your goals.
 

tomtoo

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Absolutely! It’s all just different compromises. You’ll just need to figure out the right one for your goals.

I want a good FR, good dispersion and enough power. That i can see, between the speakers, Lemmy, reborn live, in all his glory grining devilish to me and saying: You idiot, in a minute is the police at your place, and your neighbours will hate you forever

:)
 
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voodooless

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Regarding IMD, here is the original LS50 (which I also own) tested by Archimago:


LS50%2B-%2BIMD%2BPanel%2B60-90dB.png


That's 0.16% IMD at 90 dB. Pretty good actually. Obviously, it's only 300 Hz, so let's dive in. Since I don't have the TSP of the LS50 driver, I used the one of the Q100, which should be close enough. I also used the earlier used 15HX500, made them both equal SPL at 300 Hz, The KEF driver needs 2.9W, the Faital needs 0.2 W ;) Here's the excursion of both with same SPL of 90 dB @ 300 Hz. Ref is KEF, Green is Faital:

1657527151622.png

That is already a pretty big difference. If we assume roughly the same IMD at similar excursion, we'll also see that the IMD for the bigger woofer should be quite well until below 40 Hz.
 

Severian

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I'm not sure if these are still available but the 15" in particular looks spectacular:
I built a pair of these as my daily driver speakers, paired with 15" subs using the modified Eminence LAB15 woofers that DIYSG was selling for a while.

They are absolutely phenomenal speakers. They are refined enough to use as hi-fi speakers in a small room, but I've also used them outdoors as PA speakers.
 
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voodooless

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puppet

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Seems to me that the best coaxial mounting would be behind the baffle with the woofer hole terminated as smoothly as possible .. much like a good horn would be. Should go a long way to smoothing the upper frequency responses whatever the sized coaxial.
 
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voodooless

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Seems to me that the best coaxial mounting would be behind the baffle with the woofer hole terminated as smoothly as possible .. much like a good horn would be. Should go a long way to smoothing the upper frequency responses whatever the sized coaxial.
Or recessed onto a secondary baffle. A 3D printed ring to make the baffle transition smoother could also make big difference, something like KEF does.
 

KSTR

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Great thread that I've seem to have missed so far...
I'm a sucker for large powerful coaxials for more that 10yrs now. Have been using:
  • Tannoy DC3836 from CPA 15 (15" paper cone, 60° coverage HF) : Stunning driver but beaming quite a bit at HF.
  • Beyma 15XA38Nd (15" 4in VC paper cone, 2.85" CD into 2" truncated diffraction horn stub for wide HF dispersion) : A driver that puzzles me. It is clearly a compromised design and it does not measure well but it sounds just damn great. King of headroom :-]
  • Tannoy DC3139 from System 1200 (12" polyprop cone, 90° coverage HF) : Better coverage but I could never get the upper mids fully right on those.
All of them can do fullrange (for me at least, at moderate levels) but will benefit from subs (I've used 18" OB and BR as subs, at times).
Especially the paper cone 15-inchers give me lots of of perceived texture and resolution in the bass and lower mids plus a sense of effortlessness in the HF that I don't find in, say, a typical small 2-way or 3-way (plus sub).
It might well be just a specific coloration (deviation from the source) that I happen to prefer...
 
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voodooless

voodooless

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@KSTR, go any measurements on those, on and off-axis?
 

Clavius

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These have been measured using Klippel in an anechoic chamber, working on the passive crossover now. I believe the section through the BMS driver came from me, it was sent to me by a BMS engineer in order to establish the time delay required for the cd and published on DIY Audio. (I can tell because of the red line drawn for the treble path..)
Pic of baffle is of proof of concept unit. The curvature is an extension of the cone/wg. They’re tricky beasts to wrestle into submission though. Like most coax they will not play nice on axis, we optimize at 10-20 degrees.
EE155E7F-8A46-4FB3-9AFE-69DEB939B056.jpeg
 

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Clavius

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As you can see from the attached the VCad simulation based on the 0-90 degree measurements in the chamber, the CD is in need of some intense therapy.
I had to use all 15 biquads in the available Hypex filters in the simulator. We are using FIR filters irl but I’m thinking a few of you guys like @gy-k can relate to the VCad tool. Finding the acoustic center of the cd and applying the correct timing offset is key here and VCad is perfect for this!
 

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