Dayton CX150-8 Coaxial Project

[jhollander]

Bill, my comment was with respect to creating a Open Baffle midrange. I ran the sim with a narrow open baffle and it looks like a tweeter to mid xo of 2K Hz and a woofer to mid xo of 500 Hz. You could do a thick flat baffle plus a woofer enclosure to simplify construction. Here's a drawing.

[6thplanet]

I think it needs a rounded top, not the same radius as the driver, something more like twice the radius. Another cool feature would be to angle the top of the woofer box like your "90.08" line in the frontal view of that dimensional pic.

[ani_101]

You can make a removable back cap/box for the mid, that will be within the rules for InDIYana, and remove the box and a XO change for the OB.

[ani_101]

John, how does the directivity work with regards to baffle width?

[Kevin K.]

Bill, my comment was with respect to creating a Open Baffle midrange. I ran the sim with a narrow open baffle and it looks like a tweeter to mid xo of 2K Hz and a woofer to mid xo of 500 Hz. You could do a thick flat baffle plus a woofer enclosure to simplify construction. Here's a drawing.

John, the tweeter on this Coax has an Fs of 1940hz. You think it would be ok to cross at 2K?

[4thtry]

I broke the drivers in for 3 hours with a 25Hz sine wave, about 1/4" peak to peak. Then I let them sit for a couple days. I warmed them back up a little by playing some low level music through the 5.25 inch drivers for about 10 minutes to simulate actual use. For the larger 10 inch woofers, I applied a 25Hz sine wave at a low level for 5 minutes to simulate actual use. To calculate VAS, I used the DATS V2 added mass method, using 40.4 grams for the 5.25 inch drivers and 78.3 grams for the 10 inch drivers. The tweeters were measured cold with no break-in or added mass.


CX150-8 Tweeters:
A B
Re 5.772 6.108 ohms
Fs 1884Hz 1884Hz
Qts 1.875 2.757
Qes 6.338 9.126
Qms 2.662 3.951
Le 0.02859mH 0.03001mH

CX150-8 mid/woofers:
A B
Re 6.206 ohms 6.178 ohms
Fs 62.58Hz 61.24Hz
Qts 0.4474 0.4138
Qes 0.4952 0.4542
Qms 4.638 4.653
Le 0.4444mH 0.4572mH
Mms 12.35 grams 12.33 grams
VAS 0.2176 cu ft 0.2277 cu ft
SPL 86.74 1w/1m 87.03 1w/1m

RS270P-8 woofers:
A B
Re 7.367 ohms 7.603 ohms
Fs 21.53Hz 22.88Hz
Qts 0.3097 0.3183
Qes 0.421 0.4269
Qms 1.171 1.252
Le 0.2979 0.3242
Mms 70.18 grams 66.06 grams
VAS 4.06 cu ft 3.821 cu ft
SPL 86.25 1w/1m 86.72 1w/1m

Alignments:

In WinISD, the RS270P-8 woofer produces a flat vented alignment with an F3/6/10 of 32/27/23Hz using a 3 inch ID vent, 12 inches long, in a 1.69 cu ft box. This tunes the 10" woofer to 28Hz.

In a sealed 0.25 cu ft box, the CX150-8 has an F3/6/10 of 110/76/55 and a Qtc of 0.603, which should be just fine using a 400Hz or so xover. SPL simulations at various power levels in WinISD indicate that both drivers should be able to play at up to 100dB or more before exceeding Xmax.

My plan is to line the inside of the 1.69 cu ft box with 1 inch of fiberglass on all walls. And I am going to install a large removable panel on the back so that I can remove the entire bass reflex port assembly. This way I can install and adjust a short 6 inch long trap stub on the port. The 1st port resonance of 558Hz is probably inaudible, but one thing that I discovered when working on the Plumbers Delight speakers is that, regardless of tuning, the trap also acts as a general low pass filter, which helps to reduce the amount of internal box midrange energy from leaking out of the port.

Bill

[4thtry]

Bill,
that's going to look pretty cool I think. How do you print out something like that full size? Staples, or go to a surveyor or something like that? Good idea. I end up transferring my computer drawings to full size newspaper print, but it's not as accurate as a full-size printout.

I usually do a full-scale mock-up in cardboard for more curvy cabinets or those with lots of angles to make sure it looks right full size. I've had my sketches look good as sketches but not so good in the flesh until I adjusted a few dimensions. Man, you're not letting the dust settle are you?

Also, I'm pretty sure I landed 4 or 6 of those same terminal cups for like a buck or so each at the tent sale? Yeah, I had to buy them too!

TomZ

Thanks Tom,

I just printed two full scale drawings this afternoon at my local Fed Ex. Used a wide body 36" HP inkjet in black & white draft mode. Color is expensive, but black & white draft mode is very cheap. Less than 10 bucks for two full scale prints. I intend to tape these prints to the top of a 3/4" 24x48 handy panel and then very slowly (and carefully) cut along the curved line with my hand held jig saw. Should work. I created the drawings full scale in photoshop and then saved them out to a full scale PDF drawing. I have yet to double check the dimensions on the prints, but they should be exact.

[4thtry]

Bill, my comment was with respect to creating a Open Baffle midrange. I ran the sim with a narrow open baffle and it looks like a tweeter to mid xo of 2K Hz and a woofer to mid xo of 500 Hz. You could do a thick flat baffle plus a woofer enclosure to simplify construction. Here's a drawing.

Thanks for the clarification, John. So you are talking about the directivity pattern with respect to frequency set up by the open baffle dimensions. But as Kevin pointed out, the 2k crossover is too low. I am looking at a minimum of 3.5K at 12dB/octave.

[4thtry]

I think it needs a rounded top, not the same radius as the driver, something more like twice the radius. Another cool feature would be to angle the top of the woofer box like your "90.08" line in the frontal view of that dimensional pic.

On my first draft, I was going to round the top, just as you suggest. But then I stopped, and 2nd guessed myself. The asymmetry of the odd shaped top creates tension and causes the viewer to look twice. It also helps to spread out the baffle step a little (but this could also be achieved by offsetting the driver within a rounded top).

Not sure I understand your 2nd suggestion about the 90.08 line

[4thtry]

You can make a removable back cap/box for the mid, that will be within the rules for InDIYana, and remove the box and a XO change for the OB.

Thanks Ani. I will keep this in mind should I go in the OB direction. Right now I am leaning toward a simple sealed box for the mid.

[ugly woofer]

Hey Bill just a thought, it may be a lot easier to wrap the curves with 1/8" mdf, I know its more layer which equals more work, but it's an option should the 1/4" hdf give you grief, and you may find that it doesn't have to be as thick as you might think, because of the tension in the curves.

[4thtry]

Hey Bill just a thought, it may be a lot easier to wrap the curves with 1/8" mdf, I know its more layer which equals more work, but it's an option should the 1/4" hdf give you grief, and you may find that it doesn't have to be as thick as you might think, because of the tension in the curves.

Thanks for the tip. I'll keep this in mind when I head out to my local lumber yards. In my area, I have seen 1/4" HDF and 3/16" HDF. And one place has 3/16" HDF finished smooth on one side and rough on the other. Can't remember seeing 1/8" MDF in my area, but will check around.

[4thtry]

Looking like a fun build Bill! Javad

Lots of fun! And now it is time to search for lumber!

[ugly woofer]

Menards has 1/8 mdf if you have one nearby.

[jhollander]

John, how does the directivity work with regards to baffle width?

Ani above the first dipole null the summation of the front and back waves creates a petal shaped horizontal polar response. In other words dips off axis. It would be a design goal to cross the tweeter at or below the first dipole null so the off axis response is not as lumpy.