Ricci's Skhorn Subwoofer & Files

[Jesal]

Thanks Josh for this design, I was going to build a couple of Othorns but SKHorn looks more build friendly.

I'm making one SKHorn now with a plan of standing it up (mouth firing up or down).

How much space do I need between the mouth and floor?

 

[Ricci]

Im not real sure. Never tried it. Id guess at 3 or 4 inches minimum if driving it hard. If you try let us know how it works out.

[Jesal]

Thank you. Sure, will let you know.

It's just for home use, thinking of standing it up like a huge console drawer.

Make it wife friendly  

 

[awlambert]

Hi all, I'm going to build four of these but the CNC router I have access to is set up for 4x8 sheets and the operator is asking me to bring him a .dxf laid out on 4x8. Has anyone converted the layout? I'm a total newb in the CNC realm so I apologize if this is a stupid question.. Any help os greatly appreciated.

Thank you

 

Adam

[Ricci]

My advice would be to pay the operator to setup a cut program off of the print. It's not hard. He should no how to do that. Barring that perhaps someone will help you out. 

[awlambert]

Thanks! I found a guy who is doing exactly that now. I'm happy to post the files here once its all done if that's cool...

[radulescu_paul_mircea]

What do you guys think of the idea of making this a cardioid sub. With 2 21" IPal on the front and one 21ID on the back to be able to use a 2 channel 2 ohms stable (ish) amp, like a clone , on each sub ? It would need to be 50% lager, practically to just go deeper and make a fold that works exactly like the front . 

I know the enclosure will vibrate more and it would be a bit hard to match the tuning for the port, but I think the hardest part is to get that horn right and to be able to find a good folding. It would probably need different hatches also

But I need that configuration and I bet it would be awesome!

Off course, it could be easier to build 3 SKHorns and stack them with one backwards but the place I would be using these is a bit wide and I need to spread them to have a better coverage.

[radulescu_paul_mircea]

I've just ordered 2 21Id drivers, so I'll probably build these. They'll have 2 21Ipal on the front in series and one 21ID on the back . I'll use a Powersoft K10 on the front drivers and a FP14K clone on the ones on the back, one on each channel . Processing will be a DBX driverack. 

It will be very helpful to get some direct comparisons between the 18Sound and B&C drivers, I'll also get to play with some mammoths, because they'll get very large

[chrapladm]

What are Mammoths?

[Ricci]

On ‎5‎/‎10‎/‎2018 at 3:33 PM, awlambert said:

Thanks! I found a guy who is doing exactly that now. I'm happy to post the files here once its all done if that's cool...

Great. Sounds like it'll work out for you.

[Ricci]

17 hours ago, radulescu_paul_mircea said:

I've just ordered 2 21Id drivers, so I'll probably build these. They'll have 2 21Ipal on the front in series and one 21ID on the back . I'll use a Powersoft K10 on the front drivers and a FP14K clone on the ones on the back, one on each channel . Processing will be a DBX driverack. 

It will be very helpful to get some direct comparisons between the 18Sound and B&C drivers, I'll also get to play with some mammoths, because they'll get very large

 I'd probably just design a separate cabinet module or an identical 3rd Skhorn sub to be placed in the arrays to keep weight and size down. If the situation lends itself to it and you don't need a cardoid pattern so much, you can leave the extra size and weight at home. I don't like it all being built into the same cab even though it can greatly simplify the setup. YMMV

[radulescu_paul_mircea]

The drivers are already here! The 21ID is so small and light compared to the 21Ipal.the cone is much softer,  also, the coil is way smaller, with a much thinner wire and it gets hot more quickly. Probably twice as fast. 

The driver gets very noisy after about 3.5 cm excursion pk-pk , in comparison the B&C can travel about 5 cm before any strong noise . We clearly have a winner here, but that was not what I wanted to do.

@Ricci you are right, the setup is a bit stupid proof, it's easier to get it right and to avoid any tempering with the setup. 

The decision is not final and it's pretty hard to get the fold good enough to match the phase and response of the front part. I also wanted to put the port and the horn in the center to get the acoustic path as close as possible vertically and horizontally

[Ricci]

Good luck with whatever you end up deciding to do Paul. Share a bit when you can. 

[radulescu_paul_mircea]

Already ordered some wood, in fact a lot, I needed to order more to get the best price and I also need it for my other projects.

 I thought a lot of what you said and the sub would weight too much to be practical. So I decided to go modular. The idea is to make two SKHorns , but the depth will be 40" and the width 28", and port tuning will be a little higher , at 34 hz approximately, Just to get the best deep end I can, but also to match the top end a bit.

The back enclosure will be an Ss15 based design, where I try to match the phase as well as I can, but I need the best efficiency  to be centered around 50 Hz  if I can, because I will make an end-fire configuration with that center frequency and the response of the front enclosure will have a high shelving in the back of it, so the frequency response for not need to match . 

The two enclosures will be installed back to back with screws buried on the sides . I wanted to use an electromagnet like the ones for doors , but that would complicate things a bit and unfortunately I'm a bit short on time

I ended up with end-fire instead of gradient configuration after I did a very cool experiment. I put the RTA I'm REW on infinite averaging for a  5 hours set only with the music they are playing and the conclusion was that the energy is centered at 52 hz with a difference of 6 dB compared to the 40-110 hz band. So if I can get the attenuation of -15-20 dB at 52 hz in the very far field, over 100 meters distance in the back of the speakers, compared to a normal setup, it will be extremely helpful.

I've already got my drivers, the difference between the B&C and the 21ID is night and day, power handling, excursion, shear mass, thermal inertia etc. But they are both extremely well.made drivers, with different applications for the same approach.

The plan is to build these speakers for use in this application and to use them for comparing my own designs which will be build in the next month.

I'll post some pictures when I'll start building

 

[Ricci]

Agreed on the ID 18sound drivers vs the IPAL B&C's. I have the 21nlw9601 and a 21ID and they are identical outwardly. Only the sticker visually indicates a difference. I believe the 18Sounds simply use a heavier 4 layer coil to get more force on theirs vs the 9601 series, whereas the B&C drivers seem to have entirely different and beefier motors and coils.

[radulescu_paul_mircea]

These are the modifications i made to this design, it is based on my sketches. I changed all the bracing, it was easier to make all of them with constant width because of the bigger width. The much bigger back chamber will surely increase the efficiency and power under 45 hz, I didn't feel the need to improve the horn on this one, it is good enough with just 20 cm extra length and an S1 correction. the material is already being cut

 

Edited May 23, 2018 by radulescu_paul_mircea
added braces in drawing

[Ricci]

External dimensions?

[radulescu_paul_mircea]

4 hours ago, Ricci said:

External dimensions?

140*100*70 cm .

[radulescu_paul_mircea]

Each driver on one FP14000 clone chanel, CEA2010 burst, calibrated mic, 4 meters, added 6dB for 2 m equivalent. Where you see a question mark, the amp turned itself off for protection. the closest buildig was at about 10 meters behind the sub.

Bph221

25-124.1dB

31,5-135,1 dB

40-141,1 dB

50-144 dB?

80-145.3 dB?

90-144.9 dB?

100-144,2dB ?

[Ricci]

Looks like mission accomplished to me. Response shape is good. 30Hz is absolutely hammered.

The 21Ipal will take a beating and those impedance mins pull a lot of current. Not surprised the amp gives up first. I ran the K20 bridged into the 2 ohm load which is in no way recommended. It operates decently but same as the FP amp it does not like the huge current dump required and protects out.

[radulescu_paul_mircea]

His 3 brothers are on their way, I'll have 2 with 21Ipal and 2 with 21ID but with slightly modified bracings. This one didn't behave as I wanted it to and there was a strong vibration on the large panels so I need to add 3 more pieces of wood from one side to the other. Another problem is the weight, at 165 kg, it is pretty hard to manage.

After all , I will not build the back ones for cardioid configuration, I'll use them as they are.

These are the test enclosures, to learn and to try things. They will be for comparing my new designs and to see what kind of improvements I can manage to squeeze , if I go bigger but I'll keep the dimensions constraint to 140*140*70/75 cm...

[StainlessSteve]

That box is 34.6 cubic feet, or 16 cubic feet larger than the original, and the "passive all vents open" results show 125.6dB at two meters at 25hz. I would expect there would be more output capability with a bigger amp, but if not, there's not an improvement in terms of output per liter per any frequency.

[radulescu_paul_mircea]

After adding two more braces from one side to the other, I did another round d of bursts.

4 meters, added 6 dB for 2 meters equivalent.

25-126.7 dB

30-136.7 dB

31,5-  137.3 db

40-141,4 dB?

50-144.2 dB?

80-146.4dB?

90-144.9 dB?

100-144,2dB ?

The sensitivity at 30 Hz is 99.8 dB at 4 meters at 2.83 V. Just a dB higher than the original. 

[radulescu_paul_mircea]

This is the final measurement before painting and adding some damping materials

 

 

[radulescu_paul_mircea]

So after all, the CEA-2010 from REW is showing the peak pressure level of the frequency tested, not a mean, so one one shouldn't add another 3 dB to get a peak.