[openback]

Greetings.

Can someone please direct me to some successful design using 2 Alpha 15 for OB projects with passive crossover design.  I did a lot of searching but could not really see anything that has instruction for a completed design that includes drivers used, crossovers schematics, etc...  Thanks in advance.

[ecir38]

Don't think there are any documented projects with two alpha'a that use a passive network.
One day down the road I would like to build one with the Fostex FE167E's that i have to get a little more effiency.

If your room isn't that big, one alpha in this config would do the job.
http://www.quarter-wave.com/OBs/OB_Design.pdf
I built it with the FE87E with the publish xo. They are the best speakers I have built yet. 

BR

[ecir38]

This project started to go passive but ended up active, it's a good read.
http://www.audiocircle.com/index.php?topic=53821.0

BR

[openback]

Thanks BR for the link.  I am well awared of the one alpha 15 and fostex project from Martin; Though I am using low power tube amp and at 90db efficient it wont do it for me.  Thanks again.

[MJK]

Copied from another thread. I have not built this version .... yet, but based on my experience using a Lowther PM2A and a pair of Eminence Alpha 15A's it should be an excellent performer.

Each channel is a Lowther PM6A, PM6C, or DX2 full range driver with two Eminence Alpha 15A woofers wired in parallel. I might be tempted to later add an Aurum Cantus G2Si for the very top if needed.  A baffle 2' x 4' baffle will yield an excellent system that will produce ~96 dB/W/m and be -3dB at 40 Hz. I have all of the parts but have not had the time to actually follow through and build this system.


Active Crossover Settings

Low Pass - 200 Hz 2nd order Linkwitz-Riley
Hig Pass - 400 Hz 2nd order Linkwitz-Riley


Passive Crossover Sizing (classic 2nd order circuit configuration)

Zobel circuit across the woofers
  Mills 4 ohm resistor
  Solen 30 uF

Low Pass
  ERSE 14 ga Super Q 4.7 mH in series with the drivers
  Solen 130 uF in parallel with the drivers

High Pass
  Solen 27 uF in series with the drivers
  ERSE 14 ga Super Q 5.6 mH in parallel with the drivers


http://www.erseaudio.com/Products/14-AWG-1-63mm
http://www.partsexpress.com/solen-metallized-polypropylene-capacitors.cfm


These would be my starting crossover values and I would tweak them by ear.

Hope that helps,

Martin
 

[openback]

Many thanks Martin.  I may have to try that when I can find a nice pair of Lowther.  The combo sounds like a winner.  Thanks again MJK.

[freddyi]

hi MJK - would your passive highpass starting values be pretty close for 206E?  Best, Freddy

[MJK]

Freddy,

I doubt it. You would have to recalculate the crossover frequency based on the FE-206E's Thiele / Small parameters and how it responded mounted in the baffle. Then if the Re was different from the Lowther's that would also influence the crossover component values.

Sorry,

Martin

[freddyi]

thanks for the reply Martin - might the lowpass alone with Alpha be ballpark to embark empirically with 206 on top and would 206 be a good choice from the getgo?  Freddy

[MJK]

Freddy,

My guess is that a FE-206E would work well if the crossover was designed for the driver. I don't have any of these drivers so I really can't offer more then an opinion.

Martin

[freddyi]

yeah - 206 + 2-Alpha 15 (or GW1858) should be feasible for a low cost system on a narrow baffle.  Is anyone making a longer stroke dedicated open baffle alternative to Alpha 15? (probably dreaming) - seems like Q could be kept up reasonably high, double xmax with Gamma- Delta size motor (~40-53oz slug) Take care,  Freddy