Stentorians' little brother.... maybe

[Tomato]

Hello all, I have been an avid reader of this forum for long time and really appreciate the community that has been developed here allowing questions and more importantly pictures to be posted .
This is more "Theory Crafting" and questions than build.
For a while now I have been wanting to build Curt's Stentorians for a center channel for my HT but due to driver availability the Aura 6" (to my knowledge) is only found on ebay at $50 per driver or more. Needless to say that is way out of my price range. Still needing a center channel, a Overnight Sensation MTM came to the rescue which I had great joy building and listening to which gets better and better by the day.
In the back of my mind I still could not get the Stentorians out of my head. I dont know why but I think they would be perfect for my situation. With limited space the TV would need to physically rest upon the speaker and with a long center channel that would be possible. Right now the Overnight is above the TV way above ear height.
Looking for the Aura drivers I found a 5.25" Aura with similar properties but my little knowledge about designing crossovers, I am pretty sure that you cant use the regular design for the smaller driver and it might even need to be designed for in wall use because of the location of the TV. I am more familiar with actual box design so that wouldnt be so bad. For $3.60 a driver it seems like a great alternative to the original. Would this be worth persuing or should not even go down the great long path. Essentially it would be a new speaker all together. To be honest I have tried to read many websites going through the steps of designing a crossover but between school, work, and family its next to impossible for me to devote enought time to such a task right now. It might be possible to build it for an active system but that alone adds cost into the equation that I am trying to keep down as much as possible.
Sorry for the long rant and if I may seemed scatter brained (one of the reasons I cannot figure out how to design a crossover ) but any imput or direction you can point me in would be most appreciated and thank you in advance.

Stephen

[---k---]

I can see the appeal of the Stens. That many drivers is always fun.

The typical response is going to be different drivers different speakers. blah blah blah. I haven't looked at the driver parameters between the two, so I don't know how accurate your "similar properties" is. But if true, I say go for it. I took a at the crossover http://speakerdesignworks.com/NS6project_4.html . It isn't that complicated of a crossover. For a $3 / driver, it might be worth taking a flyer on and trying out. Model the box for the new driver, buy some extra resistors and caps, and play around a little. I bet you can find something that will work for you. It might not be the perfectly optimized best solution, but I don't think even Curt's original crossover was designed to do that. The smart crossover guys here can probably give you some pointers on what to try.

[Tomato]

After doing a lot of research about crossovers, I have stumbled upon some YouTube videos that some newer people may find these useful.
Basic high and low pass filters

http://www.youtube.com/watch?v=OBM5T5_kgdI&list=PLzqS33DOPhJlDWrIiIqu5cn05-Udu0kAU

Basic inductors

http://www.youtube.com/watch?v=NgwXkUt3XxQ&list=SPC0303DF928C9F4F0

He (Afrotech) goes into how to design a circuit using a program called LTSpice. So I used that to create the "Stock" Stentorian crossover.


I know it looks like a mess, what is happening is that I am measuring the signal for all three speaker groups.
The blue and green solid lines that are intertwined are the woofers. The red solid line is the tweeter. It looks like they are crossed over about 1500Hz - 2100Hz ish range (and I could be totally wrong, but most of this is going to be theory anyways). If you have any questions about the components in the picture feel free to ask but it should be pretty straight forward. I.E. the eight 8Ohm resisters are the Aura drivers and the far far right 4Ohm is the tweeter.

[Tomato]

The picture of the signal across the crossover might not be exact and I am ok with that. I just needed a good starting point for the new drivers.
Here is frequency response graph of the discontinued 6in Aura driver.

Its fairly flat all the way to 4kHz which I find not to shabby.

Here is the frequency response graph of the 5.25in Aura driver.


It barely makes it to about 1.8kHz before going a little crazy. Is this worth pursuing because I am sure there a plenty of other drivers out there that would be more suitable. Well for about $3 why not! It will be fun

So with the given information (very basic at best), we know that we should drop the frequency crossover for the tweeter to about 1-1.5kHz.
Looking at the tweeter response

Its probably not a good idea to go below 1.5kHz at all.
So the plan
1. Design a crossover with about 1.5kHz frequency tweeter pickup range
2. Design a new enclosure for the new woofers.

[JonMarsh]

I hate t say this, but look at that response plot- this tweeter just isn't meant to cross low! With a 1500 Hz crossover, there would be hardly any attenuation of the signal input- and that will be one mighty unhappy tweeter!

[Tomato]

Cool, thank you for the input. I have been staring at the crossover and Curt's measurements of a finished speaker and although it wont be perfect I have a feeling the original crossover would work for this as well. I guess you could spend $80 on a tweeter that would go lower but that would defeat the whole idea. Maybe I am a bit too much in over my head but I must journey on Maybe this journey will help someone as well.

So step one is complete : design a crossover! lol

step two: design a new enclosure

[Tomato]

So this is what I have come up with. Still keeping to the same idea but slightly smaller. Not knowing what Q Curt was using I just modeled a very rough idea that I felt would work best. This is a very rough picture but you get an idea what is going on.



This would give almost 14 liters per pair of drivers and a Q of .88

The problem with these drivers is that they fall fairly fast around 100hz but that is to be expected from this silly driver. :lol: Not asking for miracles. But for the price and for what I am asking of it, it should do fine (crosses fingers)