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[Elliot Thompson]

Art Welter wrote on Sat, 06 December 2008 03:56

Elliot, You said: "Especially, those that are capable in achieving 500 - 300 Hz full-space" Don't know what you were going for, but 200 Hz bandwidth was probably not it..

I wasn't going for anything. My comments you quoted was based on how large of a horn is needed to provide the frequency and SPL using a compression driver when going down to 5 - 300 Hertz at full space.

http://www.lansingheritage.org/images/jbl/catalogs/1971-pro/ page10.jpg

If the horn's mouth is not big enough to play the desired frequency at a high sound pressure level, it won't do it. That is why you need multiple horns grouped together to create one big horn if you are aiming for high SPL bass ranging from 40 Hz - down.

Best Regards,

Best Regards,

[Tim McCulloch]

Hi Elliot-

Art was referring to the typo in your post (500 - 300).

Have fun, good luck.

Tim Mc

[Elliot Thompson]

Tim McCulloch wrote on Sat, 06 December 2008 20:49

Hi Elliot- Art was referring to the typo in your post (500 - 300). Have fun, good luck. Tim Mc

Thanks Tim.

Best Regards,

[Art Welter]

 "My comments you quoted was based on how large of a horn is needed to provide the frequency and SPL using a compression driver when going down to 5 - 300 Hertz at full space."

5, 500, whatever it takes...

[Peter Morris]

General comments

- Your design looks fundamentally fine.

- I would use a lower compression ratio so there is less stress on the cone.  The 3:1 you have used is getting up there for “standard” cone materials and designs.

- You don’t need all of those fancy curves for low frequency horns.

- I would select a different driver eg. 18sound 18WL1400, RCF LF18X400, B&C (what ever the equivalent is)

- In most situations the speaker would be used on the ground so I would use 1/2 space loading ( pi) when I model it.

- If you are only going to build 2 of these boxes I would build some good double 18 reflex cabs instead. If it was only 4 cabinets I would shorten the horn to about 8 feet.

- Use a lot of bracing – there is not enough in the LAB.

[Jared Scott]

Peter Morris wrote on Sun, 07 December 2008 23:16

General comments - Your design looks fundamentally fine. - I would use a lower compression ratio so there is less stress on the cone.  The 3:1 you have used is getting up there for “standard” cone materials and designs. - You don’t need all of those fancy curves for low frequency horns. - I would select a different driver eg. 18sound 18WL1400, RCF LF18X400, B&C (what ever the equivalent is) - In most situations the speaker would be used on the ground so I would use 1/2 space loading ( pi) when I model it. - If you are only going to build 2 of these boxes I would build some good double 18 reflex cabs instead. If it was only 4 cabinets I would shorten the horn to about 8 feet. - Use a lot of bracing – there is not enough in the LAB.

I am currently re-doing the design with a different more horn friendly design.

The complex curves are gone.  The horn bends are still smooth curves, but those will be simple to build.

It is designed as half space loading, pi is quarter space loading.

If I ever actually build it (as stated before, this is more gears toward a learning expreience than actual build project), I plan on building 8 of them.

[Jared Scott]

Ok, lets see if I'm making progress:

This one measures 45x45x18" external dimentions
It was modeled with this driver: http://pasub.com/PASUB390.pdf

I understand that this driver is not available yet, just experimenting.

Horn numbers


Cross section view


3-D View


1, 2, 4, and 8 cabinets at 2.83 volts


1, 2, 4, and 8 cabinets at program power

[Johan Diettrich]

Tho this is unknown territory for me, a 2:1 compression ratio seems high for a driver with 40 mm linear excursion capability.

Group delay figures from Hornresp are difficult interpretted, exporting as an AkAbak script gives easier digestible gd figures.

Those corner deflextors aren't strictly nessecary for sub usage.

Best regards Johan

[Peter Morris]

"It is designed as half space loading, pi is quarter space loading." ...oops brain fart you are correct.

I would have a look at what happens if you shorten the horn a bit. You may gain more useful output than you loose in LF extension.


FWIW have a look at these links.

http://www.billfitzmaurice.com/T48.html

http://billfitzmaurice.net/phpBB3/viewforum.php?f=12&sid =34588dfcfa53949660a2d51ad54170e1

http://billfitzmaurice.net/phpBB3/viewtopic.php?f=12&t=4 293

http://billfitzmaurice.net/phpBB3/viewtopic.php?f=1&t=71 63