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-   -   Advice please for 2-way build with Alpairs (http://www.diyaudio.com/forums/markaudio/156730-advice-please-2-way-build-alpairs.html)

gmg733 14th December 2009 04:28 AM

Advice please for 2-way build with Alpairs
 
All,

Greetings! I'm looking to build some two-ways for a home theater and have been looking at the MA Alpair 6 for the mid-high duties. Then, MA went off and made the Alpair 7. So here is my dilema. I'm wanting to cross the Alpairs and the mid-woofer over around 300-500Hz. Looking at the freq graphs for the Alpair 6 & 7, the 6 seems to have a more consistent level frequency response from 20 to 20kHz than the 7 with less peaks and valleys. And the 6 seems to be a bit more efficient in the mid-band frequency range. I have read a lot of good things in regards to the 7, but is the 6 a better fit for my application? Yes I know either would do just fine, but there seems to be a lot of improvement in the 7 over the 6 and if I'm going to spend the money I might as well get the 7 if it is that much better. I think I read somewhere the freq chart for the 7 is not smoothed. Is this true? Just looking for some opinion. I know Mark is really likes the sound of the 7. I'm not a pro at all things audio, but I'm learning. I like the idea of a solid performing full range with a separate woofer.

Thanks in advance. I'm looking forward to my project which should be happening soon.

Greg

Scottmoose 14th December 2009 03:09 PM

Hi Greg,

I (and Mark) have mentioned this before elsewhere (no reflection), but WRT the graphs, you're not comparing like-with-like. The Alpair 6 data sheet was made at a time when Mark, under advice, had applied a modest amount of smoothing to the graphs. Same went for the Alpair 10 and original CHR70 for that matter. 99.99% of manufacturers do the same thing. However, I know Mark, given his engineering background, was never comfortable with that, so the published manufacturers plots for the latest units (CHP70, new CHR70, Alpair 12, Alpair 7 & EL70 made for CSS) have reverted back to something closer to the raw data. Were you to apply the same standards to both units, the basic response balance would look very similar. They're not designed for a perfectly flat balance BTW; take a look at the general trend & you'll see how it's been shaped. That's deliberate; a lift in the lower mids to help correct for step-loss, a dip in the sibilance band (boon if you like female vocals), gentle lift above that to ensure things have a nice sense of air & detail, & a gentle roll-off above this to keep the HF smooth & allow extended listening periods without fatigue. Very British.

Depends on the rest of your system & what you're going to be doing with it TBH. Me, I'd go with the A7; the A6 is a lovely little unit with a magical midrange, but I like the extra efficiency of the slightly bigger driver (these things being relative of course) and it all but matches the current A6 through the midband -benefits of the new suspension & multiformed cone.

chazdrumzalot 14th December 2009 08:43 PM

I have been thinking of doing this exact same thing for a while but I'll substituting the CHR70 for cost-effectiveness. Out of curiosity, Greg, what do you plan to use as the woofer in this application?

gmg733 15th December 2009 01:53 AM

Scottmoose,

Thanks for the info, that must be what I read earlier.

Chazdrumzalot,

I'm waiting on the arrival of the new Exodus Audio Anarchy 6.5" woofer. It can be seen here and there are some links to YouTube videos. Kevin is a great guy with a great product. He runs Exodus Audio/DIY Cable, but I think Dan Wiggins consults for Exodus products. I have a Maelstrom-X 18" sub today and it is nice. What I like about the Anarchy is the XLB^2 motor design and quite frankly Kevin is thinking of selling these for $40 a piece.

Anarchy is coming soon.....

Another great mid-woofer would be the CSS SDX-7. A lot of people rave about it and it is also a great product. I think Dan Wiggins might help Bob out as well. Can say for sure. Anyhow, you might want to consider that.

I am a value person and I find greater value in CSS, Exodus, Mark Audio and etc. When companies get big, they are too worried about marketing budgets and all the profit motive crap. These guys are doing it because they are passionate about it and they want to make a good product. My .02.

I hope this helps. I am experimenting with round enclosures at the moment, fiberglass made. I'm doing some reading on omnipoles as well to see if they might make a play in my set up. I'm doing a lot of research but I am getting to the point of buying. I'm tying up some loose ends in regards to series vs. parallel x-over and etc.

Thanks!

Greg

Jozua 15th December 2009 06:53 AM

Scott

I am in the process of ordering a Alpair 7. What do you consider the optimum box for this driver. I am a newbie at using FR drivers and I am hoping for excellent detail from this driver

I was tempted by the Alpair 12 but in the absence of a proven box design I have decided to hold back. It is still a toss between the latest Tangband 8 and the Alpair 12 for me. So the Alpair 7 will be my "test run" in metal cones.


Regards.

Jozua

Scottmoose 15th December 2009 12:59 PM

There are proven box designs for the A12, such as the Pencil I did. I gather from Mark that a pianist friend of his loved them. However.

There's no such thing as optimum TBH; what you will prefer depends on circumstance (rest of system, esp. the amplifier; room, material to be played; personal preferences in terms of presentation; size considerations; aesthetic considerations etc.).

WRT other matters, Dan Wiggins did do some work for Bob of CSS a while back; the FR125 and the predecessor to the SDX7 all use or used his XBL^2 motor design. It's far from being a panacea, but it's another string to the bow, as it were. The SDX7 is an interesting unit from the POV that it's very much a (compact) woofer rather than a midbass -it's best up to ~500Hz, making it ideal for mating to wide-band drivers, if you want more dynamic range without having an XO slap-bang in the middle of our critical hearing BW like most modern multiways (which isn't the best of ideas IMNSHO).

Good luck with the omnis; they're largely a matter of luck as you're listening to the room rather than the speaker, but if you like that sort of sound & the room is suitable, I reckon you'll be a happy camper. You could try a semi-omni or an FR bipole if a full omnidirectional doesn't suit.

gmg733 15th December 2009 07:53 PM

... if you want more dynamic range without having an XO slap-bang in the middle of our critical hearing BW like most modern multiways (which isn't the best of ideas IMNSHO

Exactly why I'm doing this Woof-FR hybrid. I think I'll be pleasantly pleased at the end of the day. And I'll have world class sound without the world class budget. :)

Thanks for the input. The more I read and thinking about the omnipole, the more it doesn't fit my application.

chazdrumzalot 15th December 2009 08:37 PM

That exodus woofer is very interesting indeed. The price is certainly right. I was looking at the Dayton RS225 8" woofer for a few reasons: the higher sensitivity may alleviate the need for BSC if crossed appropriately, and it seems to perform well in either small sealed enclosures or large vented. But this Exodus has the advantage of a smoother FR which probably permits a simpler crossover, and 2 drivers in a small tower would provide the low end gain necessary to eliminate BSC. What to do, what to do!

Scottmoose 16th December 2009 12:33 AM

Were both response graphs taken exactly the same way, using the same methods, equipment, and applied smoothing? I wouldn't bet on it, in which case, don't rely too heavily on comparing published FR graphs.


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