Dayton CX150-8 Coaxial Project

[4thtry]

Are you talking about a ground plane type measurement with the loudspeaker and microphone placed near the ground? Or would this be a measurement with the loudspeaker placed up very high on some type of open frame platform? I have been thinking about constructing something like this in my back yard, but it needs to be safe and easy to construct and tear down when I get done.

[jhollander]

Bill, I raise the tweeter/ mic position up to about 7 feet on a tower speaker. That got the woofer about 3 feet off the ground where I have no noticeable reflections down to about 200 hz. Again if you are getting the match right in the Blender this would not be required. I used a small rolling painters scaffold similar to this https://www.menards.com/main/paint/l...4436076611.htm

[xmax]

A dip at 8k is strictly the tweeter section of the speaker. The mid response is too far down to have any effect at 8k. In other words, there's nothing you can, or need to do about it.

The dip at 5k is likely the tweeter as well. I'd suggest measuring the off axis of the mid and tweeter separately, and see which one is dipping.

Coax drivers will always suffer these types of peaks and dips, it has to do with cancelations from the tweeter mounted in a much
less than perfect moving "waveguide" the mid cone. Although the trade-offs can be favorable.

[xmax]

Sometimes I will put the mic like 1/4" away from the cab right between the mid and woofer for an arbitrary
measurement to see how the 2 drivers sum together with the chosen xover slopes.

[Wolf]

Sometimes I will put the mic like 1/4" away from the cab right between the mid and woofer for an arbitrary
measurement to see how the 2 drivers sum together with the chosen xover slopes.

I can see placing it between at a distance to see how they correlate, but at 1/4" and between you're going to have 75 degree off-axis responses (or thereabouts) to where the measurement really isn't worth much. I can also see 1/4" on individual driver centers being okay as that is the nearfield response measurement for each unit.

I'm sorry, but what you are suggesting does not make much sense.
Later,
Wolf

[xmax]

Arbitrary is the key word and I should have mentioned it works best with low crossover points, I guess I have never
tried it above 300hz. It also can be used to look at the port and woofer summed output. give a try sometime...

[4thtry]

A dip at 8k is strictly the tweeter section of the speaker. The mid response is too far down to have any effect at 8k. In other words, there's nothing you can, or need to do about it.

The dip at 5k is likely the tweeter as well. I'd suggest measuring the off axis of the mid and tweeter separately, and see which one is dipping.

I measured the off axis of the mid and tweeter separately and have attached them below. I am not really sure which one is dipping. To my eyes, it almost looks like I have insufficient crossover overlap between the mid and tweeter, which is causing a hole to form off axis in the 3 to 5kHz region. As I turned the speaker for each measurement, the microphone distance increased a little bit, so I compensated for this by adding a little SPL to the off axis curves when I loaded them back into OmniMic.

[wogg]

It looks to me like the tweeter alone is dipping hard at the 5 and 8k points in your 15 degree measurement. I think that may be a byproduct of the coax mount and transition between tweeter diaphragm and woofer cone. If I'm right, there's not too much you can do, there are tradeoffs to get that time aligned point source.

How's it sound to your ears? Also, hoping these are at MWAF next year. I'd like to hear them!

[xmax]

It looks to me like the tweeter alone is dipping hard at the 5 and 8k points in your 15 degree measurement. I think that may be a byproduct of the coax mount and transition between tweeter diaphragm and woofer cone. If I'm right, there's not too much you can do, there are tradeoffs to get that time aligned point source.

How's it sound to your ears? Also, hoping these are at MWAF next year. I'd like to hear them!

Yes exactly as stated above. I would make a simple LR2 at around 2K or use a active filter,
for both the mid and tweet and measure them at low level (because the tweet will not behave well)
It's a good starting point for any design.

[4thtry]

It looks to me like the tweeter alone is dipping hard at the 5 and 8k points in your 15 degree measurement. I think that may be a byproduct of the coax mount and transition between tweeter diaphragm and woofer cone. If I'm right, there's not too much you can do, there are tradeoffs to get that time aligned point source.

How's it sound to your ears? Also, hoping these are at MWAF next year. I'd like to hear them!

You are probably correct as to what is going on here. In terms of sound quality, when I stand or sit about 8 feet in front of the speaker, the overall tonal balance seems to be fine with my latest crossover L-PAD adjustments. Based on my blended NF+FF FRD's, which are very close to John's blended files, I am applying roughly 4-5dB of BSC. If I apply the full 6dB of BSC, they sound a little dark and bass heavy in my room. But the full BSC may sound just fine in a larger room.

If I get up and do a "walk around" as the music plays, I can definitely hear the off-axis response fall off in the 3-6khz region. And if I stand directly behind the speakers, the high frequencies appear to fall off significantly. If I place a different speaker, using a standard 1 inch dome tweeter, in the same position, the high frequencies do not fall off to the same degree, either off axis or behind the speaker.

Yes, I plan to bring these to MWAF and enter them in the "Dayton only" category.

[4thtry]

Yes exactly as stated above. I would make a simple LR2 at around 2K or use a active filter,
for both the mid and tweet and measure them at low level (because the tweet will not behave well)
It's a good starting point for any design.

I currently have the crossover set at approx. 4kHz @ 12dB/octave. Fs for this tweeter is approx. 2k, so I thought it best to keep the xover point at least one octave higher than this. Also, moving the xover down to 2k might overdrive this tweeter. The spec sheet lists the usable frequency range as 3500-20K.

[4thtry]

Bill, I raise the tweeter/ mic position up to about 7 feet on a tower speaker. That got the woofer about 3 feet off the ground where I have no noticeable reflections down to about 200 hz. Again if you are getting the match right in the Blender this would not be required. I used a small rolling painters scaffold similar to this https://www.menards.com/main/paint/l...4436076611.htm

Thanks, John. Yea, that would work well. Easy to set up and tear down after measurements!

[xmax]

I currently have the crossover set at approx. 4kHz @ 12dB/octave. Fs for this tweeter is approx. 2k, so I thought it best to keep the xover point at least one octave higher than this. Also, moving the xover down to 2k might overdrive this tweeter. The spec sheet lists the usable frequency range as 3500-20K.

That's why I stated low level, but 4K is fine, I would consider 3rd or 4th order for that tweeter. In other words I also start with a very simple filter (in this case more like 4K) without any baffle step comp, eq, zobels, notches etc and get a measurement of the drivers in the box individually to see what you are dealing with.

[4thtry]

Crossover boards are almost done and ready to install. Here is the final schematic, with the tweeter & mid padded down to the tune of about 4-5dB BSC.

[jhollander]

Bill where did the 15 watt resistors come from?