Infrasonic Messages: 17 Registered: March 2010 Location: Clovis, CA
Chancellor
Bad news. I got my speakers today and read on the back that they are 4648a-8's and not 4648a's which means I have six 16ohm drivers instead of six 8ohm drivers like I had thought I ordered.
Now what do I do, Wayne? I want to tear my hair out.
Wayne Parham Messages: 18686 Registered: January 2001
Illuminati (33rd Degree)
Calculating the values for the woofer circuit is easier than it is for the tweeter circuit, because the tweeter circuit has the added complexity of R1/R2 proportions. The tweeter circuit has to balance not only voltage sensitivity matching but also filter Q and the conjugation of mass rolloff. We've worked out values for 16Ω tweeter circuits here on the forum, but it wasn't scaled like the woofer circuit can be.
Basically, for the woofer circuit, you can just double the inductance and resiatnce values and halve the capacitance values when using a 16Ω woofer. One more thing though, the 2226J is 3dB lower at the same voltage level, so if you're using an 8Ω tweeter, you'll need to set the tweeter circuit (R1/R2) values 3dB lower than you would when using a 2226H woofer.
Wayne Parham Messages: 18686 Registered: January 2001
Illuminati (33rd Degree)
The more you deviate, the less I can say with certainty how it will act. You can do an MTM, I'm sure, but it's a different animal. The MTM approach has the same goals, but the distance between midwoofers of this size seems prohibitively large to me. At any rate, you'll have to do the analysis and design work to know what you have.
As for the crossover, yes, you'll have to build it yourself. We sell the unpopulated PCB and you can solder the parts on it.
Infrasonic Messages: 17 Registered: March 2010 Location: Clovis, CA
Chancellor
Cool. To be honest, I want to nip this thing in the bud and get things finalized. I really just want to order your crossover for my project instead of building one or going active.
I am thinking of trying this out as an MTM with your crossover. It's a lil' different and sounds interesting. I know you haven't tested this out fully but do you think there is any reason why it would sound bad and unlistenable? For me going this way is the best solution, I think.
I'd like to add..
I really appreciate all the assitance you have provided to me, Wayne. I also appreciate the patience you show us. I know there are many of us that come around asking all sorts of questions and expect you to know it all. You're doing a great service to the community. Thank you.
Wayne Parham Messages: 18686 Registered: January 2001
Illuminati (33rd Degree)
Personally, I think the 2.5-way will probably work better than an MTM for a loudspeaker like this. Remember that the "M" in "MTM" stands for midrange, and it is best done with small drivers, keeping the driver spacing tight. You can understand how a 1" dome tweeter flanked by a couple 6" midranges can all be packed into a foot or 15" of vertical spacing. With crossover in the right frequency range, the vertical nulls can be pretty far apart. That's the goal.
If your midwoofers are large, they can't possibly be clustered close together. A couple 12" or 15" midwoofers can't be less than a foot apart, even without the tweeter. Then add to that the height of the horn, and you have a lot of vertical spacing. I just don't see that working well. Better to go with the DI-matched two-way approach, or maybe a 2.5-way with the bottom woofer crossed-in around the Schroeder frequency.
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