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Old 26th January 2014, 02:28 PM   #2171
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Been reading this thread and started to look at youtube clips... these guys have some excellent tips and techniques which are not speakers but may enable some people some pointers to apply to speaker builds.

House models...
Foam Board Model Making Architectural House Scale Design Part 3 - YouTube

These guys build air planes.. this Spitfire build looks great... The wood sticks may be useful for aligning layers of enclosure.

Flite Test - FT Spitfire - BUILD - YouTube

PS in the UK hobbycraft shop do 3 for 2 on a 5mm A1 sheets for £4 a sheet so 3 A1 sheets for £8 I think this is about as cheap as I could find in the UK.

Tools> http://www.youtube.com/watch?v=BefKPhQCuB8

Maybe useful for smaller speakers up to 6 inches >

http://www.ebay.co.uk/itm/WA8001-Foa...item35cfbe2e07

http://www.youtube.com/watch?v=gEZuLRp6YQ8
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Last edited by jonnoshore; 26th January 2014 at 02:37 PM.
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Old 26th January 2014, 03:31 PM   #2172
xrk971 is offline xrk971  United States
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Thanks for the link to RC planes - I always thought this stuff is light and stiff making it ideal for planes. One can attach those stick on exciter transducers to the foam wing and power it with a small class D amp so that the plane can play music (or simulated 2 stroke engine screaming noises) as it flies - these all electric planes don't have the cool sound of 2 stroke engines running on nitromethane and castor oil like the good old days of RC flying.
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Old 2nd February 2014, 09:13 AM   #2173
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The problem with foam core is that it flexes if unsupported. Flat-sided designs in foam core need a lot of bracing. This is not a problem with enclosure designs such as the Cornu or the Nautaloss, where the curved sections add rigidity. Curving a panel is difficult with wood but easy with foam core. So why not make an enclosure with an elliptical cross section, with one curved piece of foam core forming the sides and back?
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Old 3rd February 2014, 02:03 AM   #2174
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X, I decided to get back into speaker building a few weeks ago after a 25 year hiatus. After a bunch of internet searching I landed on Zaph’s site and thought I’d get a few HiVi B3Ns (I bought 4) as a way to ease back into things – small full range and cheap, so no biggie if the results weren’t good. I started with a standard sealed box of 3 liter and I must say that I was somewhat underwhelmed – sound quality was okay, but just not enough of it. Gee, they are terribly inefficient little blighters!

Luckily, I then stumbled into the foam core thread and after a full week of reading enjoyment decided to give the Cornus a go. Well, I’m so glad I did. I managed to finish them in a day and a half and the result was fantastic. I have them on the wall at my chalet and they create what can only be described as, and my apologies for being so Corny, “a wall of sound”. I’ve since matched them with a sub that I transplanted from a JVC HTIB sub, which I got from Goodwill, into a nice solid sealed Orion box (old Hungarian brand). I now have both the sound quality and quantity I was hoping for. So, thanks very much for starting and pushing this thread along.

I’ve since tried a TL foam core for the other two B3Ns using this design (file:///C:/Users/hp/Desktop/Speaker%20project/B3N%20TL/u-B3N.htm) and I must say I’m somewhat underwhelmed again. They sound “small” in comparison to the Cornus. So, a question for you please – which of your other designs would you suggest for the B3Ns? I like the “big” sound of the Cornus, but would like to try something different – I could again mate them with a sub.

Cheers!

PS I just love the concept of being able to knock together an enclosure in quick time that doesn’t require a shop full of wood-working tools. It’s a winner!
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Old 3rd February 2014, 02:32 AM   #2175
xrk971 is offline xrk971  United States
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Grandcalmar,
I am so glad the Cornu's worked out for you so well.
Those HiVi B3N's really are low efficiency drivers at 81dB. I think that is a large part of why you are underwhelmed. A good cure for that if the drivers are 8 ohms is to double them up. Good thing you have four of them as what I suggest is a mini Karlsonator with dual drivers. Doubling up an 8 ohm driver in parallel to 4 ohms will give you +6dB (4 times louder) at the same voltage. So you will have 87dB at 2.83v speakers. I will post the sims and design details in the mini Karlsonator thread: Mini Karlsonator (0.53X) with Dual TC9FD's

Basically, you will get a speaker with bass in the 90+ dB that extends to sub 50 Hz. The highs will be at about 87dB and you will have built-in baffle step compensation due to all the bass gain. It looks like a great candidate.

Cheers,
X

Last edited by xrk971; 3rd February 2014 at 02:40 AM.
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Old 3rd February 2014, 02:35 AM   #2176
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Quote:
Originally Posted by Don Hills View Post
The problem with foam core is that it flexes if unsupported. Flat-sided designs in foam core need a lot of bracing. This is not a problem with enclosure designs such as the Cornu or the Nautaloss, where the curved sections add rigidity. Curving a panel is difficult with wood but easy with foam core. So why not make an enclosure with an elliptical cross section, with one curved piece of foam core forming the sides and back?
Don, I like the concept - curving to get rigidity, but having trouble visualizing the shape. No trouble with one "one curved piece forming the sides", but how can that same piece also form the back? Are you thinking of a shape like a clam (shellfish) with flat front for the baffle?

Cheers
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Old 3rd February 2014, 02:39 AM   #2177
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Quote:
Originally Posted by xrk971 View Post
Grandcalmar,
I am so glad the Cornu's worked out for you so well.
Those HiVi B3N's really are low efficiency drivers at 81dB. I think that is a large part of why you are underwhelmed. A good cure for that if the drivers are 8 ohms is to double them up. Good thing you have four of them as what I suggest is a mini Karlsonator with dual drivers. Doubling up an 8 ohm driver in parallel to 4 ohms will give you +6dB (4 times louder) at the same voltage. So you will have 87dB at 2.83v speakers. I will post the sims and design details in the mini Karlsonator thread: Mini Karlsonator (0.53X) with Dual TC9FD's

Basically, you will get a speaker with bass in the 90+ dB that extends to sub 50 Hz. The highs will be at about 87dB and you will have built-in baffle step compensation due to all the bass gain. It looks like a great candidate.

Cheers,
X
Thanks X, I'll check the Karlsonator thread. I'm sure I'm not the only "noob" drawn to the B3Ns by Zaph's site only then to be disappointed due to their low efficiency.
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Old 3rd February 2014, 03:47 AM   #2178
xrk971 is offline xrk971  United States
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Zaph is a great designer and I imagine that if you push enough power through those speakers they will sound good . An 81 dB efficient speaker will lose several dB of sensitivity when a passive crossover is used so it is probably in the high 70's per watt. That means that you will have to be pushing them at 10 watts or more to really feel satisfying mid 80 dB's.
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Old 3rd February 2014, 04:20 AM   #2179
AZDoug is offline AZDoug  United States
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My wife said she was tired of the floor standing speakers, so could I please make a wall mounted one?

Click the image to open in full size.

http://www.esa.int/var/esa/storage/i...full_image.jpg

(really making a large pair of Cornu and a pair of 16X27FIBs right now.)

Here are a couple links showing what that huge horn is.
This Insanely Loud Sound System Simulates the Roar of a Rocket Launch

Space in Images - 2014 - 01 - Large European Acoustic Facility

Last edited by AZDoug; 3rd February 2014 at 04:23 AM.
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Old 3rd February 2014, 04:30 AM   #2180
xrk971 is offline xrk971  United States
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NASA has a bigger and better one: RATF in Ohio does 163 dB and is bigger (1800 sq ft x 57 ft tall)
Space Power Facility (SPF)

Look at how many horns there are and the size of the mouths.

Click the image to open in full size.

This is cool but what does it have to do with foam core?
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