Orion-like project design

[Nanook]

many here may know that I am a single driver convert, and am pretty adamant about their use as often as possible. But here I find myself digressing and reverting back to a multi-way design for a truly full range design (although not for me ).

I really like the basic design that Siegfried Linkwitz promotes on his site, the Orion. But it seems to me that the most basic incarnation might be to use a full ranger on the baffle, with a powered sealed or aperiodic sub providing the bass foundation. I figure a Xover anywhere from 60-200 Hz would be suitable and adjusted by ear.

So, after some digging around, I think I've found some interesting stuff to make it happen:

M&K 250 watt plate amp (X's 2 for a stereo pair) with crossover , M&K 12" driver.Vifa coaxial driver. (all from ApexJr.). The total cost for the project will be in the $450 range without enclosures.

The idea here is to provide a coherent sound source. The Vifas are surplus ceiling types, with a soft dome tweeter.

The subs are to be fed with 2X's Left, and 2X's Right signal. The sub enclosures shall either be sealed (as per M&K's original design) or aperiodic. I'd prefer down firing subs to emulate an omni directional bass source. I also like the small overall dimensions of the Orion (and the NaO speakers as well). As the parts have already been ordered, the design will be implemented shortly. And because I'm out of my element regarding sub-woofers and multi-ways I thought I'd ask for some help/input.

Any thoughts or opinions on the proposed project? Thanks in advance to any and all that reply

Any ideas or comments? Top end to be driven by tubes..


stew

[sreten]

Hi,

The Orion and NaO both use a narrow baffle and boost to compensate
for the baffle loss until the bass section takes over. In both cases the
boost is effectively reducing the excursion capability (one of the reasons
they both have twin drivers) and this does place highish power requirements
on the main panel amplifier.

A single 4" is going to struggle in a narrow baffle for excursion, and
need some juice to get there as well, valve watts are expensive.

Cannot find the M&K 12", there is the Eosone 12" .....

The sub amps look good with a wide range and +6dB boost facility.

I'd take a look at :

http://www.quarter-wave.com/General/OB_Design.pdf

And note the offset c/o frequencies to hit the design target.

I'm suggesting you follow the general principles but keep the bottom end sealed.

/sreten.

[Nanook]

The M&K woofs were hidden in the plate amp page, but as I've taken the last ones he had, he's taken them off of the page. Effectively the end result for the sub will be something like the sub these components were designed for, the M&K 1250 sub, but a stereo pair. There will be no problems with bass output, as 250 watts available per sub should take care of that.Information for the Sub is available on the 'net, but I'll attach something to this post....the point of the aperiodic enclosure is not to reduce size as many suggest, but to reduce the impedance peak (by up to 50% as some have suggested
M&K info at Apex Jr.



As per the Vifa Coaxs, they are quite efficient and I think (with a little help), I can implement a passive baffle step. As for the tube amps, those are already part of the plan. (please note that I am a Grant Fidelity home demonstrator, and have 1 each of the Affordable Series amps in stock for demo purposes). Please look here for details regarding the amps, or see the most current issue of Affordable$$Audio for further details.

Thanks for any and all ideas and help....

stew

[sreten]

Hi,

The vifa coax's are going to be around 86 - 87 dB/w I'd estimate.

I figure a Xover anywhere from 60-200 Hz would be suitable

How low you take them and with what baffle size (and thus baffle
loss) is critical to not compromising the effective dynamic range.
(Presumably considerable at the bass end).

e.g. a 12" wide baffle has ~ 9dB loss at 100Hz, this is a bucketful
of excursion capability to lose especially for a 4" driver. It also
decimates the apparent amplifier power and this still ignoring
the extra boost you need for the drivers open air response,
which is likely another 5dB.

As you will get an ~ 4dB baffle hump at ~ 500Hz you are looking
at around 18dB difference in capability at 100Hz and 500hz, this
is just based on the amount of power input. You have lost 9dB
permanently on the drivers maximum level at 100Hz, and anyone
familiar with 4" drivers knows maximum levels at 100Hz in boxes
is distinctly unimpressive, on a narrow baffle it will be pathetic.

/sreten.



/sreten.