Flex Your PCD Mettle:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

I'm back to working up the models for the 15" Kappalite 3015, QSC WG, and B&C DE250. I measured the responses of each driver in the cabinet (w/ TrueRTA) and am working on the FRD and ZMA files in Jeff B's Response Modeler before dumping them to PCD.

A couple of questions come up while working on the woofer curves:

Does smoothing matter? Measured at 1/24 octave - looks better at 1/6 (or less).

Impedance # 1 - I can't measure impedance and Jeff B says to use the modeled impedance (see http://techtalk.parts-express.com/sh...1&postcount=57) rather than doing the curve trace. My model is missing the spike at the resonance frequency. Is that normal or did I miss something? ooops - ran wrong model - now two spikes using T/S parameters. OK?

Impedance # 2 - At what point (frequency) does it make sense to "model the upper frequency rise in the Response Modeler to overlay the traced impedance at higher frequencies". See post referenced in # 1 above.

Baffle diffraction and baffle step compensation - There seems to be little or no discussion in this thread on this topic. Is it addressed in the crossover design without discussion or it more or less ignored as inconsequential in eWave design philosophy?

Relative volume of FR curves - Is the efficiency difference between LF and HF curves "fixed" in PCD by assuming an L-pad resistance? Not sure if the question makes sense...

I think I've done all I can on the woofer curve...on to the HF stuff.

BSC is definitely accounted for in these efforts. PCD models are based on measured data, on the baffle.

[augerpro]

Re: Flex Your PCD Mettle:

I've seen BSC in your crossover Pete, but not always in Zilch's versions. Maybe Zilch went without BSC because it sounded ok in his room? Anyway you can see if there is BSC or not in the transfer functions. There will be a steady downward slope from 100hz-1000hz, if not it is basically flat until around just below 1000hz or so where the LP start to show up. It is also worth noting that actual baffle step is probably only half the reason to add BSC, the other being the fairly high roll off of pro drivers.

[Brian Steele]

Re: EconoWave SR

Just curious - why did you go with a rear-mount arrangement for the PA310?

BTW - the quoted Le spec for that driver is a bit high. My WT3 clocks it at 0.37 mH instead of 1.53 mH. I'm also measuring a lower Fs (39 Hz, compared to the published 44.4 Hz) and a few other minor differences in t/s parameters.

My tests suggest that this driver doesn't like going very low, but that's understandable, given it's a pro audio 12" driver.

[Zilch]

Re: EconoWave SR

Just curious - why did you go with a rear-mount arrangement for the PA310?

Mostly because the QSC is a deep waveguide, offsetting the acoustic center of its compression driver rearward with respect to that of most woofers. We have to "correct" for that in the filters in order to steer the forward axis into the desired listening window, and to the extent that we're able to assist in accomplishing that with this mounting expedient, crossover complexity may be minimized. A good example is Pete's 5-component rendition for EconoWave Deluxe....

[Zilch]

Re: Flex Your PCD Mettle:

I've seen BSC in your crossover Pete, but not always in Zilch's versions. Maybe Zilch went without BSC because it sounded ok in his room? Anyway you can see if there is BSC or not in the transfer functions. There will be a steady downward slope from 100hz-1000hz, if not it is basically flat until around just below 1000hz or so where the LP start to show up. It is also worth noting that actual baffle step is probably only half the reason to add BSC, the other being the fairly high roll off of pro drivers.

Here's SR Compact, which I'm just now working up to post. Do we consider this as incorporating BSC thus far?



Higher efficiency and pro woofers also often have rising response. Compensate for that in leveling them, as well, and we find their efficiency taking a substantial hit in the course of actually building with them.... :(

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Here's SR Compact, which I'm just now working up to post. Do we consider this as incorporating BSC thus far?



Higher efficiency and pro woofers also often have rising response. Compensate for that in leveling them, as well, and we find their efficiency taking a substantial hit in the course of actually building with them.... :(

All the more reason to run them with a sub!!!

[Zilch]

Round #5.1 - EconoWave SR Compact

Dayton PA310-8 and Selenium D220Ti on the new Dayton H6512 waveguide:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=270-318

Cab is smaller (1.4 cuft.) than the Dayton KD trapezoid kit, but it could go in those, also, becoming a 100% Parts Express project:




Raw driver responses (files next post):




First attempt:




Nearfield bass response, closed box. Distortion's kinda meaningless at this 1/4" measurement distance and -25 dB SPL that requires, but it dresses up the plot:




A peek at the horizontal directivity; this cab has 1.5" overhangs in 1" closer proximity to the woofer and waveguide. It's 15" W x 22.19" H, i.e., 1" smaller all around than PE's KD kit, with deeper overhangs:

[Zilch]

Re: Flex Your PCD Mettle:

Provenance:

http://www.audioheritage.org/vbulletin/showthread.php?18577-New-Stage-Monitors-Finished&highlight=

C/C distance 10.5", woofer piston diameter 10", mic distance 44", L-pad included at 1:00.

The files:

[Brian Steele]

Re: Round #5.1 - EconoWave SR Compact

First attempt:

VERY NICE! I might just build this (my TH, based on the same PA310, can fill in from 40 Hz to 100 Hz easily). X-over details? Can the horn be mounted vertically instead of horizontally? The cabinet is likely to be used lying on its side, rather than vertically.

[Skywave-Rider]

Re: Flex Your PCD Mettle:

Zilch,
Are the cabs a johnaec kit? Homebrew?

At first look I thought you were putting a 15" woofer in the PE KDTs.

What's your assessment of the 30º horizontal directivity at 2k? (60º total.)

[Zilch]

Re: Round #5.1 - EconoWave SR Compact

VERY NICE! I might just build this (my TH, based on the same PA310, can fill in from 40 Hz to 100 Hz easily). X-over details? Can the horn be mounted vertically instead of horizontally? The cabinet is likely to be used lying on its side, rather than vertically.

I'll post the crossover details once anyone who wants to try a sim has had opportunity to do that and post their design results here, a couple of days to a week, maybe, depending upon interest.

I've never built one vertically like you suggest, but it's unlikely that will work, as the interference nulls would severely limit the usable beamwidth in that orientation.... :(

[Brian Steele]

Re: Round #5.1 - EconoWave SR Compact

I'll post the crossover details once anyone who wants to try a sim has had opportunity to do that and post their design results here, a couple of days to a week, maybe, depending upon interest.

Thanks Zilch - looking forward to it. BTW, did you measure the t/s params of the PA310? If so, what results did you see? I'm particularly interested in Le...

[Zilch]

Re: Flex Your PCD Mettle:

Zilch,
Are the cabs a johnaec kit? Homebrew?

Thanks for all the comments, guys! Hopefully, I'll get to the second pair before long...

John

He never did. I received all of the projects he and I worked on together by bequest, and may offer a flatpack kit in his name.

What's your assessment of the 30º horizontal directivity at 2k? (60º total.)

I'll provide a more comprehensive analysis of the directivity once I get that together, but here's another couple of peeks:






I believe it's another example of something we learned earlier in this thread -- while waveguides do not sufficiently illuminate off-axis as to generate significant anomalies in the direct response, edge discontinuities do affect directivity and power response. The picture may be different with the perfed metal grille in place.

BTW, did you measure the t/s params of the PA310? If so, what results did you see? I'm particularly interested in Le...

No, but I can do that....

[Skywave-Rider]

Re: Flex Your PCD Mettle:

He never did. I received all of the projects he and I worked on together by bequest, and may offer a flatpack kit in his name.

That's a great idea. I bet he'd be happy to see that happen.

Compact is the way to go for the small musical combo traveling in diminutive vehicles.

I believe it's another example of what we learned earlier in this thread -- while waveguides do not sufficiently illuminate off-axis as to generate significant anomalies in the direct response, edge discontinuities do affect directivity and power response....

Looking forward to seeing how this works out.

[Zilch]

Re: Flex Your PCD Mettle:

Compact is the way to go for the small musical combo traveling in diminutive vehicles.

I'd certainly be using neo woofers in any complete product; the originals are beastly heavy with 2206H's in them.

[We know how to do that, now.... ]