small desktop 3 way?

[WernerM]

Wow that phase looks really good!

[Wolf]

I mean the power response on the main sum graph. GREEN line. That's your accumulative off-axis summed responses.

As for the acoustic phase summation, normally I see them like a relay race. The mid and woofer meet and shift around their xover transistion, and the mid and tweeter meet and shift around their xover transition; meanwhile running together for a limited period. This may be why your response has a bit of a hill in the middle.

But what do I know anyway....
Wolf

[donradick]

Thanks Marc - man, I'm just a monkey with a mouse, looking for good nulls at this point.
Maybe one day I'll be able to work at a higher level.

Wow that phase looks really good!

[donradick]

Wolf - one of these days a big lightbulb will light up for me!
Here's the Power Response. Is it too bumpy?

I mean the power response on the main sum graph. GREEN line. That's your accumulative off-axis summed responses.

As for the acoustic phase summation, normally I see them like a relay race. The mid and woofer meet and shift around their xover transistion, and the mid and tweeter meet and shift around their xover transition; meanwhile running together for a limited period. This may be why your response has a bit of a hill in the middle.

But what do I know anyway....
Wolf

[Wolf]

The top-octave rolls off a bit fast for my liking, but the overall is decent without peaks above the nom FR.
Being that it is 'flat', you may want to tilt the FR down a smidge.
Later,
Wolf

[donradick]

Thanks again - now that you mention it, that is a bit strange for the tweeter top octave.
Any ideas why the power response would roll off so much if the on axis FR is pretty flat?
The tweeter is mounted pretty close to the box corner. Maybe that's the problem.

I'll play with the sim and see if I can find any clues, and also lower the mid and tweeter levels a bit.

regards,

The top-octave rolls off a bit fast for my liking, but the overall is decent without peaks above the nom FR.
Being that it is 'flat', you may want to tilt the FR down a smidge.
Later,
Wolf

[rpb]

Thanks again - now that you mention it, that is a bit strange for the tweeter top octave.
Any ideas why the power response would roll off so much if the on axis FR is pretty flat?
The tweeter is mounted pretty close to the box corner. Maybe that's the problem.

I'll play with the sim and see if I can find any clues, and also lower the mid and tweeter levels a bit.

regards,

Try this notch. It should flatten out the top end. This is what I use on my vifa.

2 uf cap, 3.3 ohm resistor, and a .10 mH coil.

[rpb]

This x-over is probably not cost effective, but gave me lots of practice. How's that impedance going to work with an amp rated for 4 ohms? OK? I put a notch down low which might be a bad idea. I don't know.

[Wolf]

I spec a minima of 3.3 ohms for a 4 ohm nominal if at all possible, and in a limited bandwidth with low imp-phase angle.
I was told long ago most are okay with this.

Later,
Wolf

[rpb]

This x-over uses 23 parts. A little excessive, but for a 3-way, not too bad.

[donradick]

Thanks RPB, I've decided to regroup on the sim. For the posted sim, I measured in box, extracted minimum phase, and imported that into PCD, and figured
that with the on wall placement and smoothing the humps that BSC would work out "magically" - well, not so much in practice. The lower mids
to midrange balance is good, but I need to turn them up a lot to get some bass out - meaning I need more BSC. So I just imported the inbox measurements into
Response Modeler, added the box response and dialed in 2-3 dB of BSC (and extracted min phase, of course). That's the basis of my new PCD sim.
Does that sound correct?

[rpb]

Thanks RPB, I've decided to regroup on the sim. For the posted sim, I measured in box, extracted minimum phase, and imported that into PCD, and figured
that with the on wall placement and smoothing the humps that BSC would work out "magically" - well, not so much in practice. The lower mids
to midrange balance is good, but I need to turn them up a lot to get some bass out - meaning I need more BSC. So I just imported the inbox measurements into
Response Modeler, added the box response and dialed in 2-3 dB of BSC (and extracted min phase, of course). That's the basis of my new PCD sim.
Does that sound correct?

You lost me. I just use measurements and trial and error for my stuff, so the details of putting the files together for PCD is a little foreign to me. With PCD, I'm just changing the x-over parts, just like I would with trial and error.

Are you saying that the midrange and tweeter are too loud for the bass? Are you listening to music, or just measuring?

[donradick]

Listening to music at this time. The measurements were done at 1 meter, and in retrospect, I should have also done close miked woofer
measurements and spliced them together. Lower mids (RS150) and upper mids (TB W3) seem balanced, but the real bass seems a bit low.
I know the RS150 can play nice bass in a 15 liter box, so it must be BSC.

[rpb]

Listening to music at this time. The measurements were done at 1 meter, and in retrospect, I should have also done close miked woofer
measurements and spliced them together. Lower mids (RS150) and upper mids (TB W3) seem balanced, but the real bass seems a bit low.
I know the RS150 can play nice bass in a 15 liter box, so it must be BSC.

Did you double checked to make sure the woofers are moving the same way? I use a 1.5 volt battery.

It's easy to change a x-over if you need more bass.

[billcurrier]

Just abit to share. I had a couple of 5" three ways planned using the Carver/Peerless 4 ohm driver that both PE and Madisound had on close out years ago. I was always impressed with the bass on the 5" but mids always sound shallow and the efficiency was good. I completed one of the three ways this weekend using a Fostex 3" full range as a mid (another Madisound close out) and the Dayton txetile neo 3/4" tweet (I bought quite a few when you could get four or more for $4 something). Dave Thomas designed the crossover and this upcoming week we are having a get together in Dallas since Dave will be mvoing from Texas to Tennessee. I hope to get some third parties critical listening on them. I think your RS150 will go lower, I am at 57 Hz as the F3 and I think that is pretty accurate. The second variant will use a HiVi 2.5" full range that Madisound had on close out as the mid. Just sharing. I have an 10.5 liter cabinet with the mid taking about a iter in a PVC isolation tube.

[WernerM]

Don, did you ever figure out anything with this, or is it on the back burner for now?

[donradick]

Don, did you ever figure out anything with this, or is it on the back burner for now?

Back burner for sure.
I've often read how difficult 3-ways are (com'on dudes, keep it clean now!)
I had lots of trouble dialing in the mid crossover - learned that component changes on the LP at 3Khz
also affect the HP response at 400 Hz (wow!). But I finally got that sounding and looking pretty good,
only to find a +2 -2 dB swing around 600-1000 that seems to be related to the mid enclosure (3 inch PVC)
So it's on the back burner for now - eventually I'll go at it again with several enclosure shapes and sizes to
see if I can smooth out those ripples.

Humbling and challenging for sure.
Even more respect for you jumping in and nailing your first design with the 3 way towers.

[WernerM]

LOL, I wouldn't exactly say it is nailed. It is as good (or better) as anything I have heard at BB on the showroom floor, but there are some issues that I don't like. However, much the same as you discovered, I believe they are attributed to the enclosure, not the crossover. Also I think there are efficiency issues in the midrange as I hear distortion at higher volumes. But, again, this may be because of a less than ideal enclosure design for the mid (standing waves) for all I know, or it may be the source as I don't hear it on everything, just certain things at that volume.

[donradick]

LOL, I wouldn't exactly say it is nailed. It is as good (or better) as anything I have heard at BB on the showroom floor, but there are some issues that I don't like. However, much the same as you discovered, I believe they are attributed to the enclosure, not the crossover. Also I think there are efficiency issues in the midrange as I hear distortion at higher volumes. But, again, this may be because of a less than ideal enclosure design for the mid (standing waves) for all I know, or it may be the source as I don't hear it on everything, just certain things at that volume.

What's the status on your measurement rig?
Typically if you hear "something", if the FR doesn't show problems, then you mght find distortion (or even a CSD ring)

[WernerM]

What's the status on your measurement rig?
Typically if you hear "something", if the FR doesn't show problems, then you mght find distortion (or even a CSD ring)

Yeah I guess I need to take measurements and post them in my thread...

I think ultimately though, I am going to scrap the design, and try an OB using the TC9 as the tweeter, the GRS 8" as a mid, and 2 GRS 12" that someone so nicely gave me to cover the bottom end. That will have to wait until I am done with the DCR Maurbacs though.