Hi all,
I have enjoyed my Audio Nirvana 8" Alnicos for several years now, and have made various improvements to my setup along the way.
I have them in the Mk2 Monitor boxes specified by Dave at Commonsense Audio. they are 60 Litres cabinets, with a 9cm vent.
One piece of advice from members here was to move my subwoofer to the corner rather than have it in the middle. This has helped a lot.
I have also purchased a Dayton mic and done tests on the system and reduced peaks and lifted some troughs in the frequency response. This has also helped a lot.
But my underlying thought at the moment is, rather than fighting the drivers with equalization, the actual cabinets they are in are likely not optimal for the drivers.
They are high Qts (0.8) and high VAS (89Ltrs) (http://www.commonsenseaudio.com/an8alnicospecs.jpg
Modeling them in WinISD was illuminating. The vent is basically tuned to 60Hz and in the cabinet size I have, creates a massive peak at around 90hz, and is -3db at 50hz and drops like a stone after that. Thank God I have a subwoofer.
They also have a rather uneven output in the high-mid to treble area, and that requires a lot of EQ entries to sort out.
All that to say, I also heard from some others that high Qts drivers do not fare well in vented cabinets, and sealed is the way to go. Modeling a sealed box for the drivers requires around 160Ltrs for a balanced bass curve (-4db at 40Hz).
Or in a completely different direction, I've read that high Qts drivers suit OBs.
However when I modeled the driver in an OB there was very little output below 400Hz.
So, if you all were me, how would you approach maximising the effectiveness of these drivers? Would you put them in large sealed boxes, design some sort of Open Baffle with bass support, put them in Karlsonators? If Karlsonators, would the stock 8" driver version work, or would I need specialised dimensions?
Thanks all for your time and valuable input.
I have enjoyed my Audio Nirvana 8" Alnicos for several years now, and have made various improvements to my setup along the way.
I have them in the Mk2 Monitor boxes specified by Dave at Commonsense Audio. they are 60 Litres cabinets, with a 9cm vent.
One piece of advice from members here was to move my subwoofer to the corner rather than have it in the middle. This has helped a lot.
I have also purchased a Dayton mic and done tests on the system and reduced peaks and lifted some troughs in the frequency response. This has also helped a lot.
But my underlying thought at the moment is, rather than fighting the drivers with equalization, the actual cabinets they are in are likely not optimal for the drivers.
They are high Qts (0.8) and high VAS (89Ltrs) (http://www.commonsenseaudio.com/an8alnicospecs.jpg
Modeling them in WinISD was illuminating. The vent is basically tuned to 60Hz and in the cabinet size I have, creates a massive peak at around 90hz, and is -3db at 50hz and drops like a stone after that. Thank God I have a subwoofer.
They also have a rather uneven output in the high-mid to treble area, and that requires a lot of EQ entries to sort out.
All that to say, I also heard from some others that high Qts drivers do not fare well in vented cabinets, and sealed is the way to go. Modeling a sealed box for the drivers requires around 160Ltrs for a balanced bass curve (-4db at 40Hz).
Or in a completely different direction, I've read that high Qts drivers suit OBs.
However when I modeled the driver in an OB there was very little output below 400Hz.
So, if you all were me, how would you approach maximising the effectiveness of these drivers? Would you put them in large sealed boxes, design some sort of Open Baffle with bass support, put them in Karlsonators? If Karlsonators, would the stock 8" driver version work, or would I need specialised dimensions?
Thanks all for your time and valuable input.
I think larger sealed boxes would be good.
Monitor MkII' (24T x 11.25W x 13.5D inches or 610 x 286 x 343 mm)
These are external dimensions. Assuming the panels are 20mm thick, and the port & driver take up a couple of litres, the cabinets will only be ~40 litres internal, which is pretty wee for that driver.
Lightbit's suggestion is free and seems like a good start.
If you stuff the port, and the 90Hz hump persists, you'll know that problem has a cause elsewhere.
Another simple test is extending the baffle, since the stock box has the driver centred in a fairly small front panel. Try taping a 'wing' of cardboard to one side of the box, and see if that makes the response smoother.
Monitor MkII' (24T x 11.25W x 13.5D inches or 610 x 286 x 343 mm)
These are external dimensions. Assuming the panels are 20mm thick, and the port & driver take up a couple of litres, the cabinets will only be ~40 litres internal, which is pretty wee for that driver.
Lightbit's suggestion is free and seems like a good start.
If you stuff the port, and the 90Hz hump persists, you'll know that problem has a cause elsewhere.
Another simple test is extending the baffle, since the stock box has the driver centred in a fairly small front panel. Try taping a 'wing' of cardboard to one side of the box, and see if that makes the response smoother.
Thanks guys,
I'll try stuffing it initially and see if there's an improvement.
My gut feeling is that it requires an entirely different cabinet though.
Hollowboy with the wing, do you mean a rectangle shape that extends past the side of the driver?
Also, about my username, no, sadly it's just a username I created 18 years ago and has stuck with me ever since!
I'll try stuffing it initially and see if there's an improvement.
My gut feeling is that it requires an entirely different cabinet though.
Hollowboy with the wing, do you mean a rectangle shape that extends past the side of the driver?
Also, about my username, no, sadly it's just a username I created 18 years ago and has stuck with me ever since!
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Hi pico, the Nelson Pass SLOB looks amazing, but is likely way too big for my current living room. 
Bigun, I also have a pair of 15 Ferrites. They've been sitting in their boxes for almost a year now. I am dying to build something for them, but they necessitate a cabinet or baffle simply too large for my living room at the moment. It makes me want to move house! In the next house I will be sure to build them. I am leaning towards 60cm open baffles for them with sealed sub support, but the idea of very large sealed cabinets is very tempting as well. They must have amazing dynamics in that configuration!
In regards to the treatment you have your drivers, do you have a photo or a link to a page where someone is discussing that treatment in further detail? I'm interested in trying it out myself. Thanks!
Bigun, I also have a pair of 15 Ferrites. They've been sitting in their boxes for almost a year now. I am dying to build something for them, but they necessitate a cabinet or baffle simply too large for my living room at the moment. It makes me want to move house! In the next house I will be sure to build them. I am leaning towards 60cm open baffles for them with sealed sub support, but the idea of very large sealed cabinets is very tempting as well. They must have amazing dynamics in that configuration!
In regards to the treatment you have your drivers, do you have a photo or a link to a page where someone is discussing that treatment in further detail? I'm interested in trying it out myself. Thanks!
Hi Mkane, are those 15" subs? The setup looks amazing. I can't tell exactly, but are they open baffles? How do they sound? I can imagine they'd be pretty darn good!
From what I can tell though, the alnicos are very different in their design to the ferrites, in that the ferrites usually have medium to low Qts (0.4 to 0.2), whereas the alnicos have quite high Qts (0.8+). This means they likely need differently configured boxes.
From what I can tell though, the alnicos are very different in their design to the ferrites, in that the ferrites usually have medium to low Qts (0.4 to 0.2), whereas the alnicos have quite high Qts (0.8+). This means they likely need differently configured boxes.
Attachments
you could take a chance with a Karlson 12 - keep the cutoout for a 12 - use an adapter ring and front mount the Nirvana on the ring
K12 Version 1 - Fall 1954
http://i.imgur.com/ZMGQve3.png
K12 Verion 2 - (guessing ~1956 - it was published in the July 1958 issue of Popular Mechanics)
https://public.bn1301.livefilestore...3Zr/transductor-bo.jpg?psid=1&rdrts=175321044
K12 version 3 kit from 1960's - approximate inside dimensions (I think all K12 were built with the same outside dims) - I would open the rear shelf gap up quite a bit - its easy to tighten the gap by stacking one a piece or two
http://i.imgur.com/1pSgd4r.png
Then there's the so called "Dutch K12" with relatively huge horizontal slots for the vent
http://home.planet.nl/~ulfman/images/Plans/new12in.gif
both original K12 and "Dutch" version have been used with the Phillips 9710M - wonder why Nirvana went for a weaker motor than the old Phillips? Also, I have stamped frame AN8 with ferrite magnet and their free air resonance crept up from ~42Hz to the mid 60's - rasing qts . Someone said to use turpentine on the surround to loosen things again.
a Karlsonator 8 seems to be tuned to around 41Hz - xrk971 could sim that with your Nirvana - perhaps he can also sim the effect of lossy damping materials and find a scaling which works better than a stock Karlsonator 8
For X to do the Karlsonator simulation, you want to put the AN's parameters in a form as below
Def_Driver EV12L|Vas=82.9 Mmd=29.92g
Sd=503.3cm2
fs=55
Mms=37
Qms=4.37
Qes=0.245
Re=5.2
BL=16.34
Le=1mH
K12 Version 1 - Fall 1954
http://i.imgur.com/ZMGQve3.png
K12 Verion 2 - (guessing ~1956 - it was published in the July 1958 issue of Popular Mechanics)
https://public.bn1301.livefilestore...3Zr/transductor-bo.jpg?psid=1&rdrts=175321044
K12 version 3 kit from 1960's - approximate inside dimensions (I think all K12 were built with the same outside dims) - I would open the rear shelf gap up quite a bit - its easy to tighten the gap by stacking one a piece or two
http://i.imgur.com/1pSgd4r.png
Then there's the so called "Dutch K12" with relatively huge horizontal slots for the vent
http://home.planet.nl/~ulfman/images/Plans/new12in.gif
both original K12 and "Dutch" version have been used with the Phillips 9710M - wonder why Nirvana went for a weaker motor than the old Phillips? Also, I have stamped frame AN8 with ferrite magnet and their free air resonance crept up from ~42Hz to the mid 60's - rasing qts . Someone said to use turpentine on the surround to loosen things again.
a Karlsonator 8 seems to be tuned to around 41Hz - xrk971 could sim that with your Nirvana - perhaps he can also sim the effect of lossy damping materials and find a scaling which works better than a stock Karlsonator 8
For X to do the Karlsonator simulation, you want to put the AN's parameters in a form as below
Def_Driver EV12L|Vas=82.9 Mmd=29.92g
Sd=503.3cm2
fs=55
Mms=37
Qms=4.37
Qes=0.245
Re=5.2
BL=16.34
Le=1mH
Last edited:
Thanks Planet10 and Freddi. Yeah I thought when I started measuring these things that they would want a sealed box, open baffle or Karlsonator like setup for them to work to their strengths, and if sealed, they would need very large boxes - probably too large for my living room, unless made to be extremely tall.
With getting X to do measurements, I didn't realise it needed to be in a form. Sorry about that!
Unfortunately, given the official measurements from CommonSenseAudio, I can't seem to find where Le or Mmd are... Does anyone know a way to calculate them? I can't seem to find a way searching Google.
Also, to get Sd, I have calculated using "equivalent diaphragm radius, 77mm", so (7.7 x 7.7 x pie) = 186cm2. I hope that's correct.
Def_Driver AN8Alnico|Vas=89.6 Mmd=?
Sd=186.3cm2
fs=41.712
Mms=9.97g
Qms=4.588
Qes=0.992
Re=7.2
BL=4.356
Le=?
With getting X to do measurements, I didn't realise it needed to be in a form. Sorry about that!
Unfortunately, given the official measurements from CommonSenseAudio, I can't seem to find where Le or Mmd are... Does anyone know a way to calculate them? I can't seem to find a way searching Google.
Also, to get Sd, I have calculated using "equivalent diaphragm radius, 77mm", so (7.7 x 7.7 x pie) = 186cm2. I hope that's correct.
Def_Driver AN8Alnico|Vas=89.6 Mmd=?
Sd=186.3cm2
fs=41.712
Mms=9.97g
Qms=4.588
Qes=0.992
Re=7.2
BL=4.356
Le=?
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