Audax AP210Z0's

[billw]

I got a pair of these, rather on impulse, at the tail end of the recent sale at PE. I also bought a pair of Dayton's shielded silk domes to go with them. Now I have to figure out what exactly I am going to do with them! I am hoping some of the more experienced builders out there could give opinions on a couple of questions.

These woofers look generally smooth but have a resonance with about a 3db peak at 2k.This would be right around crossover.Would it be alright to roll the woofer off a little early to compensate, or would I need to do something like a notch filter? Would it be worth lowering the crossover to 1.8k ? I am thinking of a 2nd order L-R with a Zoebel on the woofer.

For the enclosures, 1.8 cubic ft. towers tuned to 37 Hz gives me F3 of about 40 Hz.

Any comments would be greatly appreciated.

Bill Whittaker

[curt_c]

Bill,

I’d cross fairly high order and as low as possible. If you have crossover software, try adding a cap in parallel with the woofer series inductor. This circuit will provide performance similar to an elliptic filter, and used with a zobel, will probably result in a 4th order acoustic trnasfer function. The peak at 1.5K will likely give it a higher Q, more like a BW rather than a LR. IMO, the ragged response above 1.5K is the onset of cone resonance, and the faster it is pushed down into the stop band, the better. Assuming a flat baffle, a 3rd order BW may work well with the tweeter. I’d shoot for 1.8K, but the only way to see how it all fits together will be to model it in software.

C

[billw]

> Bill,

> I’d cross fairly high order and as low as
> possible. If you have crossover software,
> try adding a cap in parallel with the woofer
> series inductor. This circuit will provide
> performance similar to an elliptic filter,
> and used with a zobel, will probably result
> in a 4th order acoustic trnasfer function.
> The peak at 1.5K will likely give it a
> higher Q, more like a BW rather than a LR.
> IMO, the ragged response above 1.5K is the
> onset of cone resonance, and the faster it
> is pushed down into the stop band, the
> better. Assuming a flat baffle, a 3rd order
> BW may work well with the tweeter. I’d shoot
> for 1.8K, but the only way to see how it all
> fits together will be to model it in
> software.

> C
Thanks for the prompt reply.I was hoping something simple in the way of crossover would do,but you can't fight physics.Theres no particular schedule on this project so I think I'll take the time to investigate modeling software.
Bill

[curt_c]

Provided Link: http://www.pvconsultants.com/audio/crossover/pcd.htm


> Thanks for the prompt reply.I was hoping
> something simple in the way of crossover
> would do,but you can't fight physics.Theres
> no particular schedule on this project so I
> think I'll take the time to investigate
> modeling software.

Check out Jeff Bagby's PCD over at the FRD consortium. Everything you need is over there and its free as well. They are great guys for sharing their expertise!

C

[billw]

> Check out Jeff Bagby's PCD over at the FRD
> consortium. Everything you need is over
> there and its free as well. They are great
> guys for sharing their expertise!

> C
Looks good.Unfortunatly everything in my house right now is running Linux.I'll have to see if my son still has a Windows partition on one of his boxes.
Bill

[shawn_a]

I had my eye on those Audax woofers for awhile and I also bought them on DOTD. From what I modeled in the PCD, you and I are on the same page. The Zobel seemed to be the key in getting things to work out properly. It's really funny to me that what I'm seeing with what I have (2nd order electrical with Zobel) is in step with what Curt was saying. It approximates a third order Butterworth target at 1800 Hz. It appears that I've killed off the hump at 1.5 kHz adequately as it's not there anymore.

Where we differ is in the tweeter. I'm using the Morel MDT-20 with a 3rd order electrical with a 2Ω resistor before the HP circuit. It's response approximates a 3rd order Butterworth target where I have it crossed over. The net x-over frequency is right around 2 kHz when it's all said and done. There is a slight dip centered around 2 kHz that starts at 1.5 kHz.

Now this will mostly likely change with the Silkie but I think you are on the right track. I do recommend if you can, get the FRD consortium tools and have at it. Be aware though, I tested both of the Audax I have on the woofer tester and they measured quite a bit higher in the Fs department. I am seeing values of 44.6 Hz and 44.0 Hz for Fs and a Vas of 45.7 liters and 44.5 liters as well. The good news is the two units I have measured very closely to one another in all aspects. I'm not complaining at all when the measurements are this tight but I do wish the Fs was as low as the published specs. More good news is that your planned cabinet is still looking very good at 1.8 ft^3 tuned to 43 Hz. This yields an F3 of 40 Hz and an F10 of 31 Hz. Not too shabby in my book. Just take it easy on the power and all should be well. Good luck.

shawn

[shawn_a]

I just can't help myself from tinkering with things here. I tried out the Silkie and things look promising. Same basic topology as the Morel but I just played with the values a wee bit on both the HP and the LP. They still approximate a 3rd order BW on both circuits fairly well so I think you have a project to do now . If you wish, e-mail me and I will send you what I came up with. Second order electrical on the LP with a Zobel albeit with a slighty larger cap than was calculated (21 uF calculated which I increased to 25 uF.) Third order electrical on the HP with the same 2Ω resistor before the circuit. It looks good enough to be a nice starting place for some additional tweaking to your personal taste.

shawn

[tron]

> I just can't help myself from tinkering with
> things here. I tried out the Silkie and
> things look promising. Same basic topology
> as the Morel but I just played with the
> values a wee bit on both the HP and the LP.
> They still approximate a 3rd order BW on
> both circuits fairly well so I think you
> have a project to do now . If you wish,
> e-mail me and I will send you what I came up
> with. Second order electrical on the LP with
> a Zobel albeit with a slighty larger cap
> than was calculated (21 uF calculated which
> I increased to 25 uF.) Third order
> electrical on the HP with the same 2Ù
> resistor before the circuit. It looks good
> enough to be a nice starting place for some
> additional tweaking to your personal taste.

> shawn

I am glad someone else is working on these too. I too have the Audax/Silky. I have messed around a little and I like what I have found so far but would like some suggestions!!!!! I will try the zobel too. I think that is part of the solution. I am also having some sens. issues with the silky. I think it needs a little more spl to keep up with the Audax.......again I am still working on it!!!!! I will watch the posting and I will post if I come up with something.

tron