I have made limited number of structural pieces out of a sandwich of foam core and double wall cardboard and foam core. It was super strong and stiff. Should be a good material for the XKi Beta 8Cx. It will be super portable and light. The final material with 3 layers ended up at 0.625in thick. If I used liquid nails to glue sheets together it would have some constrained layer damping (CLD) action going on too.
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I would not put them side by side but along the axis of the aperture. I will have to recalculate the box but to first guess, double the volume and double the vent cross sectional area. Probably close enough to say make it 14in high and vent 1in high, wire the drivers in parallel and get +6dB sensitivity. If you have T/S params on the woofer I can model a XKi box for you for a triple threat.
Hi X,
Here are the woofer params: Fs = 43 Hz, Qts = 0.42 and Vas = 0.32 ft3.
For the FE85 box with doubled up vertical drivers: good to go with 14 inch high with 1 inch vent? I assume width, depth and vent length remain the same as your sketch for 1 driver?
Cheers!
The full T/S params please also need: Re, Le, Sd, Mms, Bl, Qms, Qes.
You can make box deeper and not as tall, but tall enough to hold two drivers. I would guess 10 in to 12in tall may still work -depending on taste.
Re = 5.2 , Sd = 130 cm2, Qms = 16.17, Qes = 0.43. I don't have Le, Mms or Bl
Thanks for the guidance on sizing.
Cheers!
hey X - hopefully besides fullrange and coaxial implementations, we also can get some compact PA/DJ boxes. Are K-couplers based upon K15's aspect the king of kickbins or can some of the proposed XKi aspect enclosures work as well or better? (Delta10A and Kappa12A should be good value for little K work)
my old K10 is punchy with Delta10A and a K-tube would generally be preferred to a horn or CD waveguide although the latter will work and have better protection than an exposed slotted pipe waveguide. If things are planned out, an internally mounted K-tube with compression driver can be mounted per Karlson's 1965 X15 system. The current K10's being built by TheJessMan are scaled from K15 so must use the K-tube on top.
a "K10" size K-coupler next to an original K15
my old K10 is punchy with Delta10A and a K-tube would generally be preferred to a horn or CD waveguide although the latter will work and have better protection than an exposed slotted pipe waveguide. If things are planned out, an internally mounted K-tube with compression driver can be mounted per Karlson's 1965 X15 system. The current K10's being built by TheJessMan are scaled from K15 so must use the K-tube on top.
a "K10" size K-coupler next to an original K15
An externally hosted image should be here but it was not working when we last tested it.
It should work well with pro audio woofers. I ran a sim with a Faital Pro 12HP1030 and that thing rocked at 120dB max SPL. Let me run some sims some Delta's and Kappa's. Basically if you have a driver designed for pro woofer duties in a vented alignment, it can be made to work. Generally, the 6th order bandpass will allow higher SPL levels than a plain bass reflex. The impulse response on the XKi is very uniform over the polar 90 deg cone angle. That makes for convincing drum renditions.
I have never played with K tube but will try once the PRV 280ti gets in. I am a bit skeptical of it can work as well as a good conical or Tractrix horn though.
I have never played with K tube but will try once the PRV 280ti gets in. I am a bit skeptical of it can work as well as a good conical or Tractrix horn though.
The K-tube may surprise you.
I was also skeptical. Nearly all of the midrange K-tube and klam type experiments I had attempted were frankly pretty horrendous, and my expectations were low. After making a little 6.5" long K-tube out of rolled up paper and glue, and bolting it to a PSD2002 driver, I was really pretty shocked. It had super open, clean and uncolored sound, with response as smooth as a baby's butt. For home use at least, it blew the H290 horn out of the water.
That PRV has slightly wonky response in the factory curve, but it still may work.
I was also skeptical. Nearly all of the midrange K-tube and klam type experiments I had attempted were frankly pretty horrendous, and my expectations were low. After making a little 6.5" long K-tube out of rolled up paper and glue, and bolting it to a PSD2002 driver, I was really pretty shocked. It had super open, clean and uncolored sound, with response as smooth as a baby's butt. For home use at least, it blew the H290 horn out of the water.
That PRV has slightly wonky response in the factory curve, but it still may work.
the K-tube due to size and length constants may not work as well as a horn or CD waveguide down below a certain point - but it well may "sound better" and at the very least provide a practical 2-way K-solution. The K-tube due to size and directivity characteristics will usually need no EQ to shape - part of its the lack of gain on the bottom, part probably a collapsing pattern at high Fs. Try elevating your tube about 20-30 degrees above horizontal. The tube can be mounted in regular aspect Ks right above the woofer or wideband. Transylvania's little "The Tube" is a keeper imo and easy to mimic with pvc, or paper. I don't think the negative taper towards the tip is needed but Zintz and whomever else were involved in the design felt that went with Karlson's use of tapering cross sectional area.
I've not used the PRV on a K-tube as my PRV are the screw-on only version. The Transylvania product works well with B&C DE25 and sounds good enough for my purposes with P-Audio's modest BMD440 compression driver. I do like the D280Ti PRV very much on coaxial.
one thing noted - when IG81 and myself had a short unslotted length in addition to the 5.3" long basic tube, a narrow notch - maybe around 1K2 (? - been a while) appeared - not sure if that would happen with all compression drivers or not. You can make a 5.3" long tube slotted full length with 1/8" initial slot width for comparisons. It would be interesting to test tubes like Faerber uses which are very long to poke through their stone midhorn. Faerbar appears to slot about half the length. I'm not sure of the diamter but guess 1.4" (?)
I've not used the PRV on a K-tube as my PRV are the screw-on only version. The Transylvania product works well with B&C DE25 and sounds good enough for my purposes with P-Audio's modest BMD440 compression driver. I do like the D280Ti PRV very much on coaxial.
one thing noted - when IG81 and myself had a short unslotted length in addition to the 5.3" long basic tube, a narrow notch - maybe around 1K2 (? - been a while) appeared - not sure if that would happen with all compression drivers or not. You can make a 5.3" long tube slotted full length with 1/8" initial slot width for comparisons. It would be interesting to test tubes like Faerber uses which are very long to poke through their stone midhorn. Faerbar appears to slot about half the length. I'm not sure of the diamter but guess 1.4" (?)
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My tube had a 5.5" slotted section, and a 1" unslotted section. I did not get a notch. IIRC the whole thing was +/- 1.5db over its BW. FWIW. I think it meshed particularly well with the PSD2002, since that driver has a bit of rise near its cutoff a 1.2kHz, and the tube doesn't have much (if any) gain there compared to a horn.
Nice 3d drawing! Yes, the 6th order bandpass with a K aperture improves the max SPL by helping to control cone excursion so it will get louder than a bass reflex. It produces more bass that is directed to the front than a simple round bass reflex or slot port so in a way it is more efficient. The amount of bass is really the same but it will sound "bigger" than an equivalent MLTL or bass reflex box.
Add a layer of felt or open cell acoustic foam to the bottom and back behind the driver and add a small ball (uncompressed 6in dia) of polyyfill in the main chamber to help reduce the back reflections from coming through the driver and causing cancellation dips.
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Interesting to finally see some off-axis measurements! And some measurements!What's the deal with a Karlson aperture in front of the driver? Won't that mess up the polar dispersion? That's a great question, and no. The aperture actually improves the uniformity of the polar response compared to the bare faced driver:
The conventional visdom is that it's best to get a slit or hole accoustic lens as close to the driver as possible, to get the resonance far up.
But maybe the slant of the karlson slot helps in that regard, more than close proximity?
It would be interesting with a comparison to a regular slot lens, like the lemon, double Karlson slot or the straight slot.
One has to be better than the other.
layer of felt to backside of O or on frontside of X?
Attachments
X - we are trying to stop the back cone emission from reflecting off the box Nd coming back to the cone.
On the inside of the K aperture panel, it may sound better with felt lining it. Some people prefer without. YMMV.
Some absorptive felt lining on the inside of the K aperture may smooth out some of those bumps in the 1.5khz range.
Thing is I've never been happy with lenses of rigid material. No matter how much I pad them on the driver facing side they always have a tinge of cupped hands.
The only thing that works for me is material that absorb high frequencies like a thick felt plate or foam that will let lower frequencies pass.
Maybe it would be an idea to not have the slot do double duty as big vent in a BVR and HF lens?
Maybe separate the two functions?
The only thing that works for me is material that absorb high frequencies like a thick felt plate or foam that will let lower frequencies pass.
Maybe it would be an idea to not have the slot do double duty as big vent in a BVR and HF lens?
Maybe separate the two functions?
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