new project based on audio nirvana 12in drivers

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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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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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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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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.
 
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.
 
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.
 
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).
 
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.
 
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.
 
The drivers come with a transparent plastic protector that is molded to their shape. I simply place these on the top drivers when I'm not playing them.

The size of the cabinet was strictly a matter of listening preference. Believe it or not, I started with a cube of 24x24x24. But I found the bass a bit lost, and not as tight as I currently have. I ended up cutting them and making them the current size, but you could be right. Some people use them as open baffle (infinitely large).

I find the current bass to my liking and not cramped at all. At some point I will post measurements.
 
I think what Horst is suggesting is that you roll the top driver off above about 2KHz. (Horst?)

If you look at the measurements of the AN10in on the site he links to, you'll see the massive rise in response (~10db) starting at ~650Hz and reaching a plateau at ~2KHz. If the 12in driver is anything like that, then you'll have a similar imbalance. However, if you use a 2nd driver up to about 2KHz, and roll it off above that, you'll have boosted the sensitivity below this, and help balance the SPLs out a bit.
 
They are anything but dark. Quite the contrary, they are very lively.

As for the statement: "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", it is true that the volume called for is higher than 2L, and in my case the volume is around 1.5L, but I find that the additional driver on top helps with bass production, since some of its higher frequencies are away from the listener, reducing the need for a larger cabinet.

If you take a look at the current high end active infinity and B&O (not that I'm comparing with them!), you'll see that the way they get all that bass from a small cabinet is by using lots of watts for the woofers. Here we are acoustically achieving the same effect. The bass is tight and flat to as low as I can hear.

One point that you have to realize is that these are relatively cheap to make, producing some of the best sounds I have heard.
 
Hello,

thanks for help.
a driver ends by invers montage around 1-2 kHz,

if you look the graphs and the box size of the test,
and if it is by the 12" equal, a 6 db at 500 Hz for
the invers driver will help best, IMO.

invers bad look:
make it to a design like
my Posaune, Saxophon,
or a heavy flowerpot, magnetfield fixed by a piece
of metal glued under the Flowerpot, try different sizes.
 

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How interesting, I like the fact that you made your top driver almost the same depth as your main driver. That must help with creating a more pin-point 3d source of sound.

I do have a question though, referring to a real instrument like a violin, doesn't it throw all frequencies in all direction? If you're missing the top half of the spectrum, wouldn't that detract from the 3 dimensionality? For example, in a concert hall, the deflectors on the ceiling are usually designed to disperse a wide spectrum, not just the mid/lows.
 
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