[S Clark]

Well here they are- although listening response sometimes were surprising considering the graphs.
Starting with Candace and Shelby's 6 1/2" paper and AV123 dome 2 way.  Without a doubt the best built box, just too wide causing a loss of imaging.  The girls worked hard on the project, just had a design flaw. Just a bit more work on the tweeter and this flattens out nicely.  Overall, a very nice project- especially considering that they go from ground zero to completed project in around 4 months.




Next Adam's MMTMM.  Adam is from a different high school and didn't have as much access to the Clio.  His project would have worked better as a MTM (which is what I thought he was going to build).  These were Parts Express 5 1/2" buyouts that we knew nothing about.  His choice of tweeter (the PE "silkie") was probably a mistake and should have used something more efficient.  Interestingly, it actually sounded pretty  decent in selected ranges.
 


Next is Ryan's 8" two way.  This came off pretty well.  I had warned him against trying to make an 8" woofer carry too much of the midrange load.  He crossed a Morel MTD20 tweeter fairly low and got a very respectable result.  +/- 3 dB over most of the range. It was pretty responsive and definitely had a solid bass.  Overall, I'd have to say that he achieved his goals.


I'll post the best and some of the others later today.

As always, thanks to all that made this possible.

Scott

PS  the rest of the graphs are in my gallery now.  I'll post them here later.

[S Clark]

oops- double post

[S Clark]

OK, this project was by far the most ambitious. Dillan used 9 Madisound Foster 5 1/2" drivers in what was to be an open baffle line array.  He decided to make it a variation on a 3 way with 5 drivers doing bass duty, and 4 doing midrange duty.  The tweeter was the GR-Research T-6 dome with a 96 dB sensitivity.  Quickly, he ran into phase problems and worked and worked to tame them as best he could.  The adjustable wings on the baffle surprisingly had little affect on the FR curves.  Although fast and articulate, it still needs crossover work and probably a subwoofer.  High marks to him for attempting a project that was waaaayyyy beyond the requirements.


In addition to an ambitious project, it looked really good!  The cloth cover has adjustable baffle extensions attached with piano hinges.


And the FR curve...

Part of our problem was my lack of experience in measuring line array type speakers.  Even the pros argue about how to do it right. This design was extremely critical to microphone placement.

[HAL]

Scott,
For refernece, was the line array measurement made on tweeter center axis?  How far away was the mic? 

[S Clark]

Danny shot this curve with the mic at 1m at tweeter level.  We got it a bit smoother at closer to listening distance, around 9 ft if I remember correctly.  Again, it was shot at tweeter level.

[bpape]

Interesting stuff - thanks for sharing.  Looks like some pretty ambitious projects. 

Is it just me or does Adam's curve look like the xover point is showing a problem with phase? 

Bryan

[S Clark]

Here is one of the ugly.  These guys didn't use the Clio unit ahead of time, mounted the Neo 8 sideways, and just needed more help in general.


And this one was without a doubt the best of the bunch.  Danny Richie, Gary Dodd, and I all agreed that it was an absolutely top notch job.  Gary commented that it sounded like one of the AV123 bookshelf speakers--- before I told him that the woofer was the M130 and the tweeter was donated by AV123.  These guys are really good  .  Anyway, this project did everything well.  What was the kids secret?  He took really good notes when we went to GR-Research for a field trip and Danny was showing them X-over basics.

[S Clark]

Interesting stuff - thanks for sharing.  Looks like some pretty ambitious projects. 

Is it just me or does Adam's curve look like the xover point is showing a problem with phase? 

Bryan

Well, it does look like a phase problem, but reversing the tweeter did not improve things.  Adam was the only kid working on the project without a physics background.  Being from a different school, he jumped on the project just because he wanted to.  I met with him several times to offer suggestions, but in the end he went in his own direction.  My suggestion was to go with a MTM instead of an MMTMM. 

[Vapor Audio]

Interesting stuff - thanks for sharing.  Looks like some pretty ambitious projects. 

Is it just me or does Adam's curve look like the xover point is showing a problem with phase? 

Bryan

Well, it does look like a phase problem, but reversing the tweeter did not improve things.  Adam was the only kid working on the project without a physics background.  Being from a different school, he jumped on the project just because he wanted to.  I met with him several times to offer suggestions, but in the end he went in his own direction.  My suggestion was to go with a MTM instead of an MMTMM. 

Or to make the top and bottom woofers do baffle step, .5 woofers ...

Pretty cool stuff though, and great work you're doing!

[S Clark]

OK, this project was by far the most ambitious. Dillan used 9 Madisound Foster 5 1/2" drivers in what was to be an open baffle line array. 





And the  originalFR curve...

At the end of the school year Danny had made an offer to help with the crossover for this project.  We finally got up to Iowa Park, TX yesterday and Danny spent hours and hours working on this speaker.  If you will look at the above picture, you will see 9 Madisound 5 1/2 " Foster ($3) woofers mounted in an open baffle line array with the GR-Research T-6 tweeter picked for its efficiency.  It turned out that much of the problems Dillan encountered on the high end were due to not recessing the tweeter..  We cut a ring of NoRes damping material and put it around the tweeter- the result was staggering!  Compare the original treble response to that posted below.  The majority of the difference was due to diffraction effects. 
We kept getting a dip at around 1400 Hz that we just couldn't work with and finally gave up and went to lunch.  Upon return, Danny hypothesized that the U frame was creating a resonance.  With the addition of a 6 ft strip of fiberglass insulation, the dip disappeared and we got the FR curve below. As we often say in TX, Danny had made a silk purse out of a sow's ear. 
We sat down to listen to several cuts, and on a Vienna Tang song, I noticed that the piano just wasn't quite right- Danny agreed. He changed a tweeter resistor from 3 Ohms to 2.5 ohms ( I was thinking we should raise the value- shows why he is the pro and not me). Bingo   I wouldn't have believed that 1/2 ohm would make such a difference in voicing, but the difference was night and day. 
The arrangement ended up being a 3 way, with two groups of four series woofers in parallel for bass one midrange, and the tweeter.  Efficience at around 93-94 db and the lowest impedance just under 5 ohms, but the crucial bass impedance much higher.  The woofers never even came close to struggling on even the lowest and loudest passages.  The result was a very clear, unstrained set of open baffle speakers that outperform any system found in the local big box stores.  Since these are not designed to really get down low, I loaned Dillan an extra sub that I had in the garage and told him that a topnotch sub was his project for next year. 
Thanks Danny.  You are as incredibly talented as you are generous.