Hemp Cones and SQ?

[mayhem13]

Any thoughts or adjectives to describe the performance of Hemp as a cone material? Muddling over a high sensitivity 2way for HT and thought this driver http://www.parts-express.com/pe/psho...16&ctab=9#Tabs might be a good choice crossed to a 1" compression driver at 1.5khz. Any thoughts ?

[sreten]

Hi,

Very likely you would be better off with this :
http://www.zaphaudio.com/Waveguidetmm.html

If you have speaker modelling skills you could try to use the Seas
reed cone drivers (above designed before they were released.)

/sreten.


http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://www.geocities.com/woove99/Spk...esigningXO.htm

http://www.zaphaudio.com/
http://www.rjbaudio.com/projects.html
http://www.geocities.com/woove99/Spkrbldg/

[mayhem13]

Funny you should mention the WgMM, i built a pair with the RLY version sealed in 30L and i'm very happy with them. We're in the proccess of setting up a dedicated HT and i was hoping to build something new for behind the At screen. Something a bit more Dynamic. I see alot of interest in Pro drivers these days and thought i might give one a try. May go the route of the Nathan, but where's the fun in that?

[planet10]

Originally posted by mayhem13
Any thoughts or adjectives to describe the performance of Hemp as a cone material? Muddling over a high sensitivity 2way for HT and thought this driver http://www.parts-express.com/pe/psho...16&ctab=9#Tabs might be a good choice crossed to a 1" compression driver at 1.5khz. Any thoughts ?

<rant>
As far as hemp goes for a speaker cone, one should give it no more status than any other paper cone material ... why?

1/ there are literally an almost unlimited number of receipes for paper that have sufficient material from a plant with the name hemp in it, for the marketing department to call it hemp.

2/ there are over a dozen different plants with common names having the term hemp in them. Only 1 of those is "true" hemp or fibre from cannabis plants. For instance the preferred receipe for "hemp" cones in the tone tubby patent application, uses manila hemp. Manilla is a close relative to the banana plant, and no relation to cannabis. It should be noted that when this question is raised wrt the hemptone drivers (including the Omegas) no one is willing (or doesn't know -- the response from Louis himeself) to give a straight answer.

These plants all got the "hemp" added to their names because, when the US Government made cannabis hemp illegal, they needed a way to indicate substitutes as hemp was widely used in a hige number of applications (to the point where the ban on c hemp was lifted for the WW II effort)

3/ even if the cone has true hemp in it, things like the paper receipe (including fiber length, and how they were processed), the cone profile & construction, any coatings, the glue bonds, and surrounds, and how synergistic the cone is with the rest of the speaker all play significant roles.

4/ That said, c hemp (as with any of the pretenders -- they did earn the suffix because of similar properties) have the potential to make VERY good paper. But a single ingredient in the paper, with no context, tells you very little about the loudspeaker
</rant>

A musical instrument loudspeaker, in general, has to be carefully considered for repurposing for hifi -- the design goals are not the same. At least it is not a guitar speaker.

dave

[thoriated]

Looks like a nice driver. The only significant possible negative I noticed was that it was not back vented. However, it may be vented through the voice coil, but even if not, that may not be that important for the application in this case.

[planet10]

Originally posted by thoriated
The only significant possible negative I noticed was that it was not back vented.

I'd actually call that a positive... those vents can cause some nasty sonics.

dave

[thoriated]

So, would you prefer venting through the voice coil to back venting from a SQ perspective? I'm thinking of a particular driver here.

[planet10]

Originally posted by thoriated
So, would you prefer venting through the voice coil to back venting from a SQ perspective? I'm thinking of a particular driver here.

Out the sides around the spider, still behind the cone would be preferrable... the pole piece vent can cause quite an oil can resonance,

dave

[thoriated]

Thanks. Some of my favorite bass drivers, JBL K145's (alnico) with E145 recone kits are made that way (vented through the voice coil).

[mayhem13]

Any thoughts on the frequency response? Looks nice til 1.5k. Bass response also flat to 50hz with a 45hz tune in 51L.