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Old 9th October 2007, 05:50 PM   #1
Jamh is offline Jamh  United States
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Default New project based on audio nirvana 12in drivers

Hi everyone,

I wanted to share a new project based on the audio nirvana 12in full range drivers. This is my 8th pair of high end speakers that I have built and I am very pleased with their sound, comparable to (better than?) my 15in Altec coax project for a fraction of the cost.

At the heart of the project is the new audio nirvanas designed by David Hicks at www.commonsenseaudio.com, and built in China. He uses better tolerances than fostex drivers with a heftier magnet and of course being 12in they go much deeper in a largish cabinet.

Originally I wanted to build shahinian-like models, but with small full-range drivers instead of the multi-drivers. The idea was to simplify the cross-overs as much as possible. This morphed into using simply two drivers without any crossovers at all with one mounted on top of the speaker and one in the traditional way. I wanted to use a parabolic disperser to achieve the omni flavor. However after building the cabinets and experimenting a bit, the final solution was even simpler.

Here is a picture of the finished speaker.
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Old 9th October 2007, 05:53 PM   #2
Jamh is offline Jamh  United States
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The dimensions are shown below.

The cabinets are made of 3/4in birch plywood, reinforced with drywall, which is glued and screwed to the inside of the cabinet. They walls are braced with wooden rods that go from side to side (middle). For damping, high density foam (used for beds) line the inside.
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Old 9th October 2007, 05:56 PM   #3
Jamh is offline Jamh  United States
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The drivers are single wired in parallel. At first, I installed a switch that would turn the top driver on and off, in order to A/B the difference, and perhaps use the switch for different kinds of music. But as I preferred the dual drivers in every instance, I ended up removing the switch and save whatever they introduced.
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Old 9th October 2007, 06:07 PM   #4
Jamh is offline Jamh  United States
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The difference in sound between the single and dual drivers is the sense of space. Subjectively it is like listening to music in a cramped space, vs. a large open one. You would think the placement of the drivers would introduce time delays and muddy the sound stage, but in fact they expand it vertically so the sound has more 3 dimensionality, just like real instruments in a real concert hall.

The 7 1/4in port produces tight and good bass. I heard low notes that I hadn't paid attention to before (in Eno's Apollo for example). The second driver must reinforce this.

For the relatively low cost of the drivers, I couldn't recommend them more. Check them out if you can.
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Old 9th October 2007, 06:12 PM   #5
Jamh is offline Jamh  United States
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The exterior construction is two tone, coco bolo Formica is used where the drivers are, and on the sides of the base, and they received two coats of glossy polyurethane. The rest of the cabinet is left natural and mat. The only place that I had to worry about cutting the plywood at 45 degrees and biscuit join them was at the front of the base. The rest of the cabinets were simply glued and screwed together, with the Formica covering the screwed parts.
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Old 9th October 2007, 07:31 PM   #6
Jamh is offline Jamh  United States
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Default new project based on audio nirvana 12in drivers

Oops, I posted this on the "speaker" forum instead of here. Please take a look:

new project based on audio nirvana 12in drivers
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Old 9th October 2007, 09:13 PM   #7
hm is offline hm  Europe
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Hello,
do you knpw the test of the 10"
it might explain what happens by
the second driver in your construction.
http://www.audio-club.de/text.php?id=145&s=read

If you take the top driver invers change the pols,
you might get lower K2 and the driver is omnidirectional
and goes out ~1-2 kHz soft, no dust in the voice coil !

more is also not listenable in your
construction at the listening place
because of the directivity.

Please make measurements and check
if only 500 Hz 6dB for the top driver is
enough, löök the graphs of the test.

10" should be enough for normal listener.

interesting.
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Old 9th October 2007, 09:23 PM   #8
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Since the drivers have phase plugs, are you concerned with dust getting down into the voice coil on the top driver?

Just curious, why the configuration you chose, and not a traditional bipole?

What is the tuning on this cabinet? It seems a tad small for one of these drivers, let alone two, as the Vas/Qts specs are pretty high (reciting this from memory, so if I'm mistaken, my apologies).
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Old 9th October 2007, 09:31 PM   #9
Jamh is offline Jamh  United States
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I'm sorry, I didn't quite follow.

I understood that you recommend inverting the polarity of the top driver. I did consider that and after some conversations with David (the driver designer) I got the recommendation that it will not be better, however, I think it's worth trying. I will let you know.

I'm afraid I didn't understand what you wanted me to measure. The site you mentioned is in german.
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Old 9th October 2007, 09:40 PM   #10
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Aha! Nice work indeed -the old Wharfdale & Castle Acoustic approach (Howard, Harlech etc.). I like this layout a lot actually, though I prefer it with speakers that have dust-caps as noted before. Gives a very spacious sound & drives the vertical mode of the room rather nicely.

Not sure about DD's claims for the AN units -a trifle of PR there methinks. The magnet's larger because it needs to be for the same motor-power as Fostex units have. As for the tigher tolerances, I'll believe that when I see it. However, hats off to AN for the 10in & 12in drivers -nice to see units of that size in production again at last.
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