OB 2-way Alpha 15A with 27TDFC? etc

[grantnsw]

Still interested in a 2-way Open Baffle, with 15 inch woofers.

Eminence Alpha 15A with a Seas 27TDFC or even an old SS D3806?
Is this possible?

Could these tweeters work that low to effectively crossover?
With an active or passive crossover?

I looked at Pano's Manzanita's which look great but the SLS
breakup scares me off. But, I could be very wrong there indeed!

Also looked at an FE103E/Alpha 15A very well documented
project, but it seems a tad untested with real drivers?

I know nothing about active xo's except from reading Rod Elliot!
My goal, if possible, is to build OB speakers with above drivers
and match them with cheap prebuilt gainclone style LM4890
bi-amps.

OK, I'm still a novice, but still trying! Thanks a lot! Grant

As usual , if you can help me out ...WOW..thanks heaps!

[MJK]

Originally posted by grantnsw
Still interested in a 2-way Open Baffle, with 15 inch woofers.

Eminence Alpha 15A with a Seas 27TDFC or even an old SS D3806?
Is this possible?

I would recommend crossing from the Alpha 15A woofers to a midrange or full range driver at about 200 Hz using a second order filter. This allows you to use the hump that naturally occurs in a dipole's response as part of the crossover and avoid having it enter into the SPL response if you crossover higher.

Also looked at an FE103E/Alpha 15A very well documented
project, but it seems a tad untested with real drivers?

I am not sure what you mean, there are quite a few versions of this design built and discussed on forums using the FE-103E and a few other full small range drivers. One excellent alternate full range driver is the Alpair 6. There are several version of this style oif OB design shown in my gallery, you can e-mail the builders directly for more information and their impressons. It is very modest priced and yet still a simple high performance OB design.

[gainphile]

In one of my experiements I tried Alpha 15 with a normal tweeter crossed at 1.5kHz actively. It did not work well and while the sound is impressive at first, it become tiring after longer listening. It was my test before trying to clone physics CS2 - which then subsequently abandoned.

The Alpha should be used under about 300Hz from memory.

MJK's design is the simplest, documented, and tested I've seen so far.

[grantnsw]

Hi gentlemen thanks for your comments,
Martin
Thanks for info on crossing to mid or full range. The full range option seems preferable as I find 3way systems uber complicated. I wonder if a TangBand W4-1337SA would work with the Alphas?...it seems to go very low with a flat respone and tameable breakup. Not sure if its sensitivy would be within your guideline for the Alpha. I'll check later.

I was very tempted by the FE103E until I read a couple of unflattering opinions about it, one chap said it sounded funny even after 100 hours break-in. I will email the guys in your gallery 'asaigac' ! Thanks for putting me on your mailing list and I can't wait to read your 'actice-xo 2way OB' treatise when completed.

Gainphile, are the Alpha's availible in Oz please? I only found 1 site that stocks Eminence, but not that model. I found Major Music in Sydney who stock the FE103E for $75. Do you know of any other suppliers please

[gainphile]

The Alphas are very difficult to get in OZ. I was lucky to get 4 of them from sgr audio when they were importing stuff. I've sold them since changing my mind about cloning the physics CS2.

[grantnsw]

Hi Martin and Andi,
Assuming I could buy 2 Alpha 15A's, then these:

http://www.tb-speaker.com/detail/1230_04/w8-1808.htm

TangBands Qts= 0.44 might be better than the Fostex? Maybe they just need a little shelving beyond 1kHz?

btw, any near equivalents to the Alpha's in Au please?
thanks, Grant

[grantnsw]

oops, I meant shelving beyond 1kHz if used full range

[badman]

The low Qms gives me pause. Any significant edge damping on a driver like this would tend to distort the paper cone during significant excursions, I'd think.

[MJK]

Grant,

The Qts of the full range driver is not as important as the SPL/W/m. To match well with the Alpha 15A, assuming a passive crossover, you really want a driver with an SPL of 88 - 90 dB/W/m. The driver you have referenced is a little to efficient so you will need to pad it down a few dB. If you run it straight, I am afraid that the results will be a weak light bass response and a harsh and shouty midrange. You might consider the Alpair 6 which is a good match and should be readily available on your side fo the world.

If you are using an active crossover, and can independently adjust the volume levels, then you can ignore everything I just typed and pick almost any full range driver.

[grantnsw]

badman,
Unfortunately I've lost my Dickerson handbook so I've long forgotten the implications of varying Qms.
Increased distortion is of course not wanted, so I'll have to read up on it again, but otherwise the TBand
looks like a good driver 'on paper'...maybe? thanks (whizzer cones take me back to my teens, haha)

Martin,
Yes I was thinking of padding the TB if it is suitable, and maybe even reducing the response beyond 2k
in a 2way.

I googled and Alpair 6 are here at $218pair. Only 4 ohms and 15watts, enough power?
(Evidently Zaph has reviewed it, but I couldn't find it).

FE103E local $75each, Qms 2.87, the 'on paper' response to me looks better matched to the Alphas,
SPL-wise than the Alpairs?

Been reading a bit on Behringer DEQ/DCX 2496's, but most of it is way over my head. And it seems that
nearly all the chipamps etc need to be upgraded for hifi sound. Various threads on upgrades.

Rod Elliot has this: http://sound.westhost.com/project09.htm

will this work instead of the Behringer? It even looks tunable (to 200Hz?) and maybe even wire-wrap instead
of soldering. Then all I need is a small-ish 50W? amp for the full-range, I guess. He uses output gain buffers,
so that would allow independent volume adjustment for the high and low pass filters as you say, I think?
My questions probably seem laughable to you experts, but hey, things take longer to figure out when ur older!
haha

So, Martin, you can see why I'm eagerly awiting your new article! thanks, Grant