Flex Your PCD Mettle:

[Zilch]

Re: Flex Your PCD Mettle:

Everybody's gotta work up their own CSP files for now; I haven't loaded this in PCD yet, myself.

Good question re: ZMA. Don't know what file extension WT2 attaches to them, actually. Assume that's what they are for now.

[Added some measurements of potential interest, above.... ]

[donprice]

Re: Flex Your PCD Mettle:

Ahhh, that was Pete that worked up the worked up the model and you did the building and measuring. Got it. Maybe Pete can hook me up with the CSP file.

Reverse engineering is much simpler when you have the plans to learn from.:D

[Pete Schumacher]

Re: Flex It, Round 2.5 - EconoWave Deluxe HO for Efficiency HOunds:

Looks like the HO has a bit of lift in the lower end compared to 600Hz. A shallower LP filter may be in order. Also, the extra sensitivity needed from the tweeter may benefit from a change in the component values. That peaking around 5KHz can be smoothed nicely by changing around the cap value and resistor L-pad.

If you have the parts laying around, try this.

Low pass:

2.5mH 15uF

High Pass:

3.9uF
2.7 Ohm series - 8 Ohm shunt.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Ahhh, that was Pete that worked up the worked up the model and you did the building and measuring. Got it. Maybe Pete can hook me up with the CSP file.

Reverse engineering is much simpler when you have the plans to learn from.:D

I attached it in my reply to zilch. ZMA extensions have been added.

[donprice]

Re: Flex Your PCD Mettle:

Thanks guys. That's a huge time saver. Now I just swap out the 3015 curves for the 3012HO curves and I almost done :D

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Thanks guys. That's a huge time saver. Now I just swap out the 3015 curves for the 3012HO curves and I almost done :D

You'll want to adjust the acoustic offset as well. The 15 likely is more closely aligned with the tweeter, so the z axis value should be reduced.

[Zilch]

Re: Flex Your PCD Mettle:

Toed 'em in to see if the cab edges might be doing the 5 kHz thing; it doesn't appear so.

HO is Cyn, LF Grn. 4.7 uF as the core HO highpass looks a bit better, Red. XO frequency went down to 1.675 kHz, but forward axis moved up to 1° +5.5° from the midpoint between woofer and waveguide:

Vertical Polar Map doesn't make it (-6 dB) to +/- 15° at this frequency:

Here's the full +/-20°:

Compare to LF crossed 125 Hz lower:

Footnote: Lower null comes down from above the XO frequency in measurements, and upper from below it, aka the "Zilch Effect." PCD vertical driver offset up is (+) and down (-), no? Because they move opposite in the PCD sims.

[No, not because I measure them upside down.... ;) ]

[Mayhem13]

Re: Flex Your PCD Mettle:

Maybe a little non-descript foam?:p

[Zilch]

Re: Flex Your PCD Mettle:

May be time to swap in a bunch of DE250s; we're talkin' 1 dB here.... :rolleyes:

[Zilch]

Re: Flex It, Round 2.5 - EconoWave Deluxe HO for Efficiency HOunds:

Looks like the HO has a bit of lift in the lower end compared to 600Hz.

Looking at the factory curves, I'm seeing HO having more of a rising response than LF, enough so that we have to give up some of the HO's efficiency for it to play as flat down to 450 Hz:

http://www.parts-express.com/pdf/290-590s.pdf

http://www.parts-express.com/pdf/290-589s.pdf

I believe I'm seeing that in comparing the vertical polars at the low end, as well. I can't measure with sufficient resolution in that region to be sure, but there are certainly indications. Where is baffle step kicking in with these 17" wide baffles, ~800 Hz, no...?

[Jeff B.]

Re: Flex Your PCD Mettle:

Footnote: Lower null comes down from above the XO frequency in measurements, and upper from below it, aka the "Zilch Effect." PCD vertical driver offset up is (+) and down (-), no? Because they move opposite in the PCD sims.

[No, not because I measure them upside down.... ;) ]

It was recently discovered that PCD's vertical axis panning is upside down. Once I was questioned on this, it was very easy to quickly confirm it. I am surprised that I missed this, but the new version matches CALSOD exactly off-axis (I thought I tested this before?). I have corrected it in my working revisions and the change will be in Ver. 7 (If I ever get around to finishing it. )

One thing that bewilders me in you graphs is the phase response. It appears to be minimum phase based on the phase response line. However, you have an in-phase crossover based on how they sum acoustically, which would preclude it from having a minimum phase summation. It almost looks like the phase has been extracted from the final summed response, but that wouldn't be correct. Your phase should be wrapping near the crossover point.

[Zilch]

Re: Flex Your PCD Mettle:

It was recently discovered that PCD's vertical axis panning is upside down. Once I was questioned on this, it was very easy to quickly confirm it. I am surprised that I missed this, but the new version matches CALSOD exactly off-axis (I thought I tested this before?). I have corrected it in my working revisions and the change will be in Ver. 7 (If I ever get around to finishing it.)

It's critical when using the measured location of the vertical null to establish/verify z-axis acoustic center locations. The only way I could get that happening was to measure and design midway between the drivers, where the differences are small.

In the meantime, will inverting the vertical offset polarity remedy the issue? I haven't tried that yet, relying instead on the measured location in all work to date.

One thing that bewilders me in you graphs is the phase response. It appears to be minimum phase based on the phase response line. However, you have an in-phase crossover based on how they sum acoustically, which would preclude it from having a minimum phase summation. It almost looks like the phase has been extracted from the final summed response, but that wouldn't be correct. Your phase should be wrapping near the crossover point.

Yes, it's system minimum phase I'm showing, not total phase, as verification that the measurement was taken on the forward axis. I'm usually also showing the inverse null with the cursor at its minimum so it can all be correlated. I suppose I could bump up the resolution of the minimum phase, but the presentations soon become too information intensive.

It's only in the past several months that I have gone so deeply into these vertical polar determinations, and one thing I concluded immediately is that it's essential to find and design on the forward axis when forward lobe is narrow. It's an iterative process trading frequency response against forward axis steering to get it optimized, and when working with waveguides and the wide center-to-center distances they impose, it's essential to be precise when designing passive crossovers for them, as the usable vertical "window" can be quite small. :o

Wayne's video on vertical nulls is instructive:

http://www.pispeakers.com/misc/Vertical_Nulls.wmv

[Zilch]

Re: Flex Your PCD Mettle:

Four DE250 drivers, #1 on a different QSC waveguide and also shown with foam bumpers. Note expanded vertical and horizontal scales:

[That ain't it.... :rolleyes: ]

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Four DE250 drivers, #1 on a different QSC waveguide and also shown with foam bumpers. Note expanded vertical and horizontal scales:

[That ain't it.... :rolleyes: ]

It's looking like there may be a benefit to mounting that waveguide on a flush baffle.

[Zilch]

Re: Flex Your PCD Mettle:

It's looking like there may be a benefit to mounting that waveguide on a flush baffle.

It's easy enough to move the baffle forward to accomplish that, as Jack earlier demonstrated.

We're at +/- 2 dB, but there's certainly no harm in doing better.

I'm trying to figure out why the 3012LF system doesn't show so prominent a peak at 4.8 kHz as the HO here....