[tonmeister]

Hi all, first post here.

I´m in the process of gathering the parts for a pretty low compromise Open baffle project.

It will be a computer based active crossover 3 ways. Highs from 900 up will be covered by a Geddes 12´waveguide with a DE250 compression driver. Mids (120-200 to 900) will be a single TD12M and for lows I picked 4 Alpha 15A per channel. Couldn´t resist going to 4 for the price and I have a dedicated space so no WAF concerns for me, thank you.

I plan to do a similar type of structure for the Alphas as the subwoofer structure shown with the Emerald Physics CS2 here: http://www.6moons.com/industryfeatures/secondcoming/secondcoming.html

The structure that I refer to is the one where 2 alphas are facing foward and 2 back.

Have you guys tried doing something similar? Any hints to how much distance would be optimal between baffles? Lastly, and more importantly: how would you wire it up regarding driver phase?

I would appreciate your input here. Thanks for your time,

Naxo

[gainphile2]

Hi Tonmeister, there was an attempt to clone the CS2 sometimes ago in one of the thread here. I didnt' think anyone got a positive result.

My personal experience the Alpha beams too much to be crossed very high at 1kHz. But others even experienced some positive running them full range ! 

[tonmeister]

Hi,

Thanks for your response.

Well I don´t plan on running the Alphas much higher than 120Hz-150Hz (it depends on how low could I bring the TD12M on the open baffle) and even then they will be rolled off using a very steep curve with a digital crossover. I think they are the drivers for the job.

Naxo

[gainphile2]

Tonmeister, my experience with Alpha is they are very-very excellent from 320Hz below. There is a bump at about 400Hz and calculating beaming freq. using 1/2*speed od sound/diameter gives around 300Hz too.

On OB I tried to even  lower the freq. response using linkwitz transform so it gives -6 at 20Hz and they were really great.

[tonmeister]

Cool,

What I´m really interested is to know if I should wire the rear firing woofers in phase or out of phase with the front firing woofers...

I believe I should wire them in phase but i just want some help from the members here...

Thanks!!!

Naxo

[AJinFLA]

http://www.htguide.com/forum/showthread.php4?t=24902&highlight=quadrupole

[Angaria]

Naxo - are you using an active XO or one provided by Geddes? 

Always been curious about a waveguide OB combo... your results will be interesting.

[gainphile2]

Cool,

What I´m really interested is to know if I should wire the rear firing woofers in phase or out of phase with the front firing woofers...

I believe I should wire them in phase but i just want some help from the members here...

Thanks!!!

Naxo

Hi Naxo, if the target is dipole radiation, then the "air" needs to move in the same direction, which means the woofers would be out of phase.

[tonmeister]

Hi all,

Thanks for all of the help!! I found this specially educating regarding my concerns: http://www.linkwitzlab.com/models.htm#B1

I feel now inclined to do a vertical array with all alpha 15A drivers facing foward on a separate baffle, next to the baffle with the TD12M and waveguide...

Angaria, I´m planning to do active computer crossover. I will be using most of the 8 analog DA channels on my MOTU 896 firewire soundcard. Software will probably be Foobar as source then Console (a VST host ) on which I will be running a 8 channel convolution VST plugin (voxengo pristine space) with crossover, driver linearization and room correction (if necessary) files generated with Acourate.

Pretty cool on paper but this setup is so flexible that I fear I will be opening a can of worms if I´m not careful enough.

Take care!!

Naxo