The SideTowers - An F6 Corundum Build

[AdamM3]

If you look at the sim, you can see the red line doesn’t drop below the black, which means it’s not a cancellation. It’s in the actual tweeter measurement, not just the system response. It looks like Bill has the woofer surface mounted so my guess would be reflection off the woofer frame causing diffraction. This would also be why it disappears off-axis.

Good point, I stand corrected.

[4thtry]

Thank you for the suggestions. Yes, I agree, this is a very serious problem, as the ear is very sensitive in this frequency range.

I tested the speaker with the crossover and the woofer completely disconnected, with only a 50uF protection cap in series with the tweeter. The dip remains the same.

So it seems that this is being caused by some type of reflection from the baffle or woofer flange. Tomorrow, I will cut up a series of foam or felt strips and stick them along the edge of the woofer flange to see if that makes a difference.

[Navy Guy]

That dip appears to coincide with a peak in the woofers response on your xover sim pic, I would have to agree with wolf.

If you look at the sim, you can see the red line doesn’t drop below the black, which means it’s not a cancellation. It’s in the actual tweeter measurement, not just the system response. It looks like Bill has the woofer surface mounted so my guess would be reflection off the woofer frame causing diffraction. This would also be why it disappears off-axis.

[AdamM3]

Here are a few measurements. Polars look good. Z curve looks like an easy load for amp. Well balanced sound as I move about the room, stand, or sit down. BSC seems about right so far, need to compare it to some other speakers before making adjustments.

Note that the tweeter's on-axis FR has a dip at 4.6kHz that completely disappears when you move slightly off-axis in either direction. Very strange. It is not caused by the protective screen or xover, as I get the same dip with or without the screen or xover installed. 4.6kHz has a half wavelength of roughly 1.5". I have a guess as to what is happening here, but will need to run a few more tests to see if I am on the right track.

That dip appears to coincide with a peak in the woofers response on your xover sim pic, I would have to agree with wolf.

[PWR RYD]

Thanks, Craig. Just trying to boost my originally score by doing something a bit different, should I take them to MWAF next year.

Based on your last several entries I would have guessed you scored perfect 10's for originality. You are definitely not afraid to buck the rectangular box theme. David Weems' "Golden Ratio" is going to spit on your grave Bill! Lol

[Wolf]

Woofer overlap causing a problem...
Wolf

[donradick]

Here are a few measurements. Polars look good. Z curve looks like an easy load for amp. Well balanced sound as I move about the room, stand, or sit down. BSC seems about right so far, need to compare it to some other speakers before making adjustments.

Note that the tweeter's on-axis FR has a dip at 4.6kHz that completely disappears when you move slightly off-axis in either direction. Very strange. It is not caused by the protective screen or xover, as I get the same dip with or without the screen or xover installed. 4.6kHz has a half wavelength of roughly 1.5". I have a guess as to what is happening here, but will need to run a few more tests to see if I am on the right track.

YIKES! That's a serious dip in a sensitive region.

[4thtry]

Here are a few measurements. Polars look good. Z curve looks like an easy load for amp. Well balanced sound as I move about the room, stand, or sit down. BSC seems about right so far, need to compare it to some other speakers before making adjustments.

Note that the tweeter's on-axis FR has a dip at 4.6kHz that completely disappears when you move slightly off-axis in either direction. Very strange. It is not caused by the protective screen or xover, as I get the same dip with or without the screen or xover installed. 4.6kHz has a half wavelength of roughly 1.5". I have a guess as to what is happening here, but will need to run a few more tests to see if I am on the right track.

[4thtry]

Those are unique.

Thanks, Craig. Just trying to boost my originally score by doing something a bit different, should I take them to MWAF next year.

[4thtry]

Are they stable on those stands, looks like a lot of overhang. Cool unique design.

Thanks, Adam. No, they are not very stable at all. I have to place them on these stands very carefully to keep them balanced. I just set them up quickly on these stands, which have a 6x9" top and a 12x12" base, just to take a few pictures. My plan is to build a new set of stands, just for these speakers, with an extended depth top and bottom platform.

[4thtry]

Nice driver combo. I vote for veneering the edges with something contrasting, and yeah it would be really difficult with the existing vinyl.

Thanks. I agree. I am looking for something cheap and easy. Either a veneer or rattle can paint job

[4thtry]

Where would you place these and how do they sound? Is it more of a rear or side speakers for a HT setup or a 2.0 setup and have them on with sides of the main wall? Very cool build with a lot of questions

Thanks. I'll hold off commenting about the sound for now. The thing is, when you build a speaker, it always sounds very good for the first few months. Then you start to hear the problems as time goes on. I do like the sound of the new Peerless corundum tweeter, but that may change as I listen more.

For placement, I have given them the full 6dB of BSC. I plan to place them well out into the room, at least 3 feet away from rear and side walls. I am not designing them to be placed at the sides of a HT setup. Well out into the room is a must. Not on the sides of the main wall either.

[4thtry]

Plus you still get some boundary low end reinforcement from the rear port! That might be genius.

Bill 4thtry , you seem to be on a mission to minimize your baffles with your totally flat and this project. At some point I see you magically fabricating a single theoretical point source

Thanks, Wogg. That is the idea. Not possible, but that is where I would like to go.

[4thtry]

Inspiring design and build as usual!
I've spent some hours in HornResp, but certainly I'm not an accomplished ML-TL modeler.
What's that "LA TL" program? Got a link?

Thanks Don. I'm not an expert ML-TL person either. I just keep punching around in the software and taking measurements until I get things working. I still have a working copy of the Leonard Audio TL program on a PC and I am hoping that it keeps working because it is fairly easy to use, once you get the hang of it. I'm still trying to figure out how to consistently adjust the models stuffing density entries against my actual stuffing densities so that my NF cone and port measurements match the modeled response curves.

[4thtry]

I think Bill is mandating room position, as you can't place them any closer to the front wall of the room.

However, I wonder what they would sound like and how they would perform in an upfiring Omni situ like Duevel's Planets.

Later,
Wolf

Since the port is out the bottom, you'd have to tip them at an angle and/or lean them against a wall to do this. Otherwise they would become a sealed enclosure and you would lose 1/2 octave of deep bass.