Obsession with a 3-way

[AndrewM]

Ok, so the title sounds a little risque....

Anyways, I was sitting and thinking the other day about my current project (the Aria 7 TLR kit), and it's possibilities for moving to a 3-way setup. Of course that's well beyond my means of experience to make that work out well, and usually when I see somebody talking about doing a 3-way speaker that it could be easier to go active with the woofer. But that of course adds expense to the whole setup if you need more amplifiers to do it, plus the actual x-over to do it. Although to do it passive I'd either have to pad down the tweeter and 7" drivers (pretty much not a great idea), or I'd have to get multiple woofers to get up to that 94-95db sensitivity (which would basically negate the cost of getting an active x-over).

So I'm now in a situation where I have an extra 2-channels of amplification (was thinking of going to an EX/ES setup, but room doesn't really allow it). And I was just going through the Marchland site and checking out the costs of the active x-overs (not to bad).

So how hard is it to do a 3-way if you are going to go active on the woofer? Is it as simple as hooking it all up and then matching up the volume levels? Would a generic active x-over like the Marchland units (XM9 I was looking at) with 24db/octave slopes work well?

Andrew

[JonMarsh]

Andrew, it could be as simple as going with a crossover like the Marchand and a second amplifier; the Marchand would give you some freedom in playing with the crossover point. With 24 dB/octave slopes, you'll get out of the range of contributions of your woofer pretty quickly, but it does still impose some limits- such as the desirability of at least an octave to two of clean overlap between your Aria's and the woofer. Many so called "subs" tend to fall apart much over 150 Hz; some don't even make it clean that high. This is one of the biggest causes of integration problems. The Shiva is about as "extreme" a sub driver as I've seen that will handle a crossover as high as 150 Hz or so without getting into major trouble. But that's pretty much it's limit.

Drivers' like the Focal and Eton 11's, 12's, and 13's are much better behaved in the upper range, with more lattitude, but they don't have the brute Xmax for near subsonic effects. For music, that's not really much of a liability, in my opinion.

The other thing to consider is how are the Aria's voiced with regards to baffle step compensation? This has an impact on how close you will or won't locate them to adjacent boundaries. If designed for minimum wall interaction, they'll have close to a full 6 dB of baffle step compensation, which lowers the effective nominal efficiency. If they're located out into the room and they sound too thin, then they probably have a lesser amount of baffle step. I've never looked at their crossover or tried to simulate it, but I suppose that would be the easy way to find out.

The advantage of compensating baffle step for a location farther out from the walls, is that you still get boundary lift, but it doesn't start until a much lower frequency. So, if your speaker starts to roll off gently below 40 Hz, but you have it located in the room so that boundary lift kicks in about then, you can subjectively extend the room response smoothly without "boom" or muddiness. This consideration applies for adding a woofer to the Aria's, also.

Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[AndrewM]

Well, my biggest reason for doing this is because the power handling of the Aria 7 setup in the box I'm building goes WAY down after the 80Hz x-over, so I'm concerned about overdriving the speakers when listening to music in direct mode, a good transient could cause some mechanical noise (especially the way my girlfriend listens to music loud).

So this is how this idea came up. I figured I'd drop a 10" to 12" driver in there, seal up the 7" drivers and I'd be good to the low/mid 30Hz range.

As to the Aria 7 x-over, it's the model of simplicity http://www.zalytron.com/Schematics/990704_a.jpg it's nothing like the new x-overs Joe D did for the new Aria 6 models. So I don't think there is any baffle step compensation in them or anything of that nature. I am building the current enclosures though so I can get at the x-overs easily on the outside of the box so I can tweak them when that time comes (because I doubt they are truly optimized).

Andrew