Audio Nirvana Super 8 and 6B4G Amplifier

[AlejandroR]

Fists of all HELLO !! this is my first post here.
I own a 3.5 Watts 6B4G single-end amplifier and I have just bought a pair of Audio Nirvana Super 8 full range drivers. I was thinking in building tha Audio Nirvana 1.3 (the plans are included in the price of the drivers) before finding this forum.

Does anyone has ideas for a cabinet for the Audio Nirvana Super 8.

The small footprint is a must since I need a high WAF to avoid problems

Thanks
Alejandro

 

[hm]

welcome,
look these:
http://www.hm-moreart.de/70.htm

 

[vinylkid58]

Hi Alejandro,

The Super 8 is one of a few full range drivers that work in the Onken Excel calculator. The box volume would be ~70 litres for an f3 of 45Hz, with a vent length of ~31 cm (6 vents).
I have no personal experience with this driver other than trying the TS numbers in the spreadsheet. Might be worth a try in this type of enclosure.

Jeff

 

[AlejandroR]

Onken Plans

I have downloaded the Onken calculator. How can I find how an Onken box looks like ?
I have found some photos in internet (with the sides vents) but I need something to help me building one. I realy don`t have experience in speakers building. this is my first try.

Retgards
Alejandro

 

[vinylkid58]

Google "petite onken" and you should get this site:
ndaviden.club.fr/plancaisse/plancaisse.html - 12k (google will translate to english). There are plans for Onkens on this site.
Dave (Planet_10) also has a couple of Onken plans on his site. The FR125 Mini-O and the Fonken (Fostex FE127E).
Use the vent length, driver size and height from floor, box volume, and the golden ratio to determine box shape. A box for your Super 8 could have dims like: 25cm wide x 38cm deep x 74cm tall (for approx. 70L volume). This would be a nice tall slender box, but the shape could be different.
I have heard Dave's Fonkens and think they are wonderful. Must be heard to be appreciated. This is going to be my next project BTW.

Jeff

 

[AlejandroR]

Planet 10

Planet 10 Site looks very interesting. I will take a look on all designs.

The french site has also a lot of plans.

Regards
Alejandro

 

[jamikl]

I am interested in these too vinylkid58. I went to commonsense audio but could not find any TS parameters. The links etc if there, on the photos or headings didn't work. Could you please give the TS parameters if you still have them.
jamikl

 

[vinylkid58]

Here is the link to the page that shows the Audio Nirvana vs Fostex comparisons plus TS:
http://www.commonsenseaudio.com/comparison.html

Jeff

 

[jamikl]

Thanks for that jeff. Got there on your link.
Mike

 

[Pano]

AN8 in Onken?

The Super 8 is one of a few full range drivers that work in the Onken Excel calculator. The box volume would be ~70 litres for an f3 of 45Hz, with a vent length of ~31 cm (6 vents).

Hey Jeff, I was interested to read this, as the AN8 has been recommended and I love the Onken box.

But I can't get your numbers in the Onken spreadsheet without putting 4 ohms in series! Do you remember how you did it? Without the series resistance, the box is small (36L) and the F3 high.

To be honest, the Onken spreadsheet gives me fits. The ONLY driver I can get to model close to correctly is the Altec 416, the driver used in the full size Onken box published in the Audiophile Review. I can't even get the 416 to model right - to match the Onken box published for it.

Too bad, as the AN Super8 in a 70L Onken could be a fun project.

 

[vinylkid58]

Re: AN8 in Onken?

But I can't get your numbers in the Onken spreadsheet without putting 4 ohms in series! Do you remember how you did it? Without the series resistance, the box is small (36L) and the F3 high.

Too bad, as the AN Super8 in a 70L Onken could be a fun project.

That's exactly what I did (Rg=4 ohms). Sorry to get your hopes up. I guess with an extra 4 ohms, amp loading becomes an issue. Did I miss anything else?

Jeff

 

[Pano]

Thanks Jeff,
So you had to cheat, too? I don't think that 4 ohm series resistor is going to sound very good. Big loss in efficiency, too.

FWIW, the case volumes calculated with the Onken spreadsheet never seem to come out to match the volumes of established designs. Maybe a little formula tweaking is in order?

 

[vinylkid58]

FWIW, the case volumes calculated with the Onken spreadsheet never seem to come out to match the volumes of established designs. Maybe a little formula tweaking is in order?

When n=5.7, you can check volumes, vent length, Fb in WinISD. Numbers come out pretty close for most drivers. This is the only other way I have at present to double check numbers.
Maybe MJK has a better worksheet for Onkens?

Jeff

 

[kevinkr]

Actually in most cases you won't be using a four ohm resistor as that term in the calculator represents the sum of all of the dc resistances (except the VC) + amplifier source impedance and most SE amplifiers have a source impedance plus dcr >2 ohms. You do need this however and don't forget to include the cross-over inductor and speaker cable dcr in the total.

Onkens are quite sensitive to source impedance.

Something close to 4 ohms might be required with a mondo inductor (low dcr) and a solid state amplifier.

This resistor controls damping factor in conjunction with the driver qts, allows you to trade box size, efficiency and extension. Larger R results in lower F3 at the expense of efficiency and a larger box. GM can explain this much better than me. You might want to take a look at the Onken thread with my system in it here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=78407&highlight=

A 4 ohm resistor with an 8 ohm driver would cost you a little more than 3dB in efficiency, a fair trade off for the additional extension I think.

I designed for a target R of 3 ohms which is close the right value for my amplifier and cross-over design. In my case an additional resistor is only necessary when I use an amplifier with low output impedance which I am not known to do...

I encourage you to try the Onken approach with this driver, I think you'll find it worthwhile. Using a full range driver in an Onken enclosure will require some judicious use of acoustical glass, lambs wool, whatever to attenuate high frequencies in the back wave - you don't want them exiting through the ports.

See if you can find the 1950's vintage Jensen speaker project book (Onken is same as build in Ultraflex) on eBay as this will give you useful tips on its construction. Someone in Germany sells high quality copies.