Cornu spiral clone

[jetlag]

Hi
There is a Cornu clone thread in the diyaudio forum and that has been a big inspiration behind my build. I wanted to start this build because it looked simple and fun to do.
I will have to take back the "simple" clause though. Getting the spiral on the ply was an eye-opener as to how tough it can get later on.

Will be using 3" Peerless drivers for this one. Plan to do one Speaker at a time.

Yet to decide on the material for the spiral..choice is between Cardboard and Foam board. Any suggestions?

I am attaching a couple of fotos to begin with. More as the build progresses.

All plans are available in the diyaudio forum.

Later
Peace
Jetlag

 

[jetlag]

The Spiral, well, almost..

After a couple of failed attempts and after laying hands on the right material, here is the spiral. It was tough to do this. Took me nearly 5 hours for this...

The foam board is 8mm and was very fluffy initially. Sticking it to the board has made it pretty stiff. Hope to finish the remaining portion soon.

A couple of pics....





Later
Peace
Jetlag

 

[Hiten]

Looking good. A novel design idea. Also read good reviews on diyAudio.
regards

 

[jetlag]

Shrill output

Tried a dry run by placing the top board and mounting the speaker. Very poor bass and shrill output :sad:. I suspect that there are leaks in the channel and probably the channel depth is more.

Plan to get rid of leaks and may be reduce channel depth. The next step, IMO, should be to fix the top board and test. Any suggestions??

Later
Peace
Jagdish

 

[jetlag]

Something positive

The best thing about DIY is that it strengthens your belief in yourself. After a skeptical beginning, the project went through and the result is amazing. The kind of output this speaker generates is to be heard to be believed. The bass that this 3-incher produces is simply great. The drivers are hardly burnt-in and I am sure that it can only get better with time. This is one project that every DIY enthusiast should undertake. It costs peanuts to execute.

Cant wait to finish the second speaker.

Now comes the finishing part. I am looking for some ideas here. Thanks.

Some pics






Later
Peace
Jetlag

 

[gvenu]

Goog job Jaggu!!!
Venu

 

[hemantwaghe]

what is the hite material .???packing foam? can we use thermocole? there is runner belts - can we use that?

 

[darshanjoshi]

Once both the speakers are ready, can we audition the same?
If possible bring them to Mumbai Meet.

 

[jetlag]

@Hemantwaghe
The white material is foam board, commercially available as "Hitlon" in Mumbai. Usually available with those who make mattresses. Very light and available in varied thickness.
As regards thermocole, how will you get the curvature of the cornu? and would it support the final weight. Thermocole is pretty brittle that way. Various materials have been used to build this and you can try if you are sure.

@Darshanjoshi
When and where is the Mumbai meet? Bringing it is not a problem. Hope to get the build done by this week. Keeping fingers crossed.

Later
Peace
jetlag

 

[jetlag]

Some progress on Speaker 2...



Slightly different approach on this speaker..

Later
Peace
Jagdish

 

[denom]

Hi Jagdish,

Link to Mumbai Meet 2013
http://www.hifivision.com/av-lounge/35226-shoot-out-navi-mumbai-mumbai-meet-2013-a.html

Do join us with your creations!

 

[hemantwaghe]

Re: Some progress on Speaker 2...

View attachment 9277

Slightly different approach on this speaker..

Later
Peace
Jagdish

I think I have this material - but too thick to bend.

also this material is porus so it will not affect sound?

BTW you generated the? how?ese curves on some software? how? will you please chare the file?

also what is the height of the strip?

There are thick rubber belts I am planning to use these . Dunno what it is called- i think these belts are used in V belt applications

 

[trittya]

Hi Hemant Bhau and OP Jetlag
Methinx an optimally chosen v-belt ought to do fine. Thanks for the idea.
Just take care that you go for a belt thats both thick & broad enough. Also, it must be plain, designed for plain pulleys, not grooved ones. Just make sure it doesn't flex sideways.
Try to find a non-rubber belt with max tarpaulin-like content. These are used to drive heavy-duty (non-unitary) water pumps & the like.
All the best for your build. Do keep us posted.
HTH
Cheerio

 

[jetlag]

Update..

Some pics







Later
Peace
Jetlag

 

[jetlag]

@Hemant
I think you have a thicker material. Mine is 7mm thick and very flexible. The channel height is 3". I am using the plans redrawn by Dave of Planet 10 hifi.
They are available in diyaudio. Let me see if I can post them.
All I did was to get the plan printed to scale and then transfered that on to the ply using carbon paper.

Later
Peace
Jetlag

 

[trittya]

Hemant et al
Another material worthy of consideration is GREEN fiberglass sheet used for awnings etc.
Can be cut into strips of suitable size, is very durable, relatively acoustically inert and optimally flexible/rigid. Can be thinly coated for optimal SQ by way of damping.
Cheerio, ALL.

 

[jetlag]

Done!

Hi
Completed the Speakers. Initial observations..
Very good reproduction, bass is tight and really amazing considering the size of the drivers. Bass is height dependent. Almost zero bass at Ground level. I have now placed them at a height of ~1.5M. Will do some more experimenting.
The next part is to give the final finish..probably by this weekend.

And
Denom, Hemant and Darshan...Sorry guys. I cannot make it to the meet. I am out of Mumbai from 30th and will be returning on 10th AN. Will miss the meet:sad:. Really wanted to meet you all and put this thing to test.

Later
Peace
Jetlag

 

[Sumanta]

This is superb dear Jetlag.

With good paint or graphics they will look super cool in rooms.
Bravo.
how did you get the idea of using this PUF kind of material. This idea alone is equally amazing like the idea of Cornu spiral.

I am thinking this idea can be used even as back loaded horn cabinet as well.
How good are high frequency responces?

Above all, thanks a lot for sharing it.

 

[denom]

Re: Done!

Hi
Completed the Speakers. Initial observations..
Very good reproduction, bass is tight and really amazing considering the size of the drivers. Bass is height dependent. Almost zero bass at Ground level. I have now placed them at a height of ~1.5M. Will do some more experimenting.
The next part is to give the final finish..probably by this weekend.

And
Denom, Hemant and Darshan...Sorry guys. I cannot make it to the meet. I am out of Mumbai from 30th and will be returning on 10th AN. Will miss the meet:sad:. Really wanted to meet you all and put this thing to test.

Later
Peace
Jetlag

Thanks for the updates & sad that you cannot make it for the meet.
Nevertheless, we will catch up for a listening session @ your place once you are ready to have us over.

 

[jetlag]

>Sumanta
Thanks for your kind words. Still working on the finish. Will post images at the earliest. The speakers sound sweet. I plan to test it with another amp and will post my impressions soon.
>Denom
Sure, let us meet at my place. Just give me some time to get finish and get organized. May be other interested FM's can join too.:thumbsup:

Later
Peace
Jetlag