Flex Your PCD Mettle:

[donprice]

Re: Flex Your PCD Mettle:

I could use a little help modeling a crossover for the Eminence 3015 and the QSC/DE250 combo. I started with the files from the 3012HO/QSC/DE250 combo (you guys rock!) and made these changes:

Used PCD V7
Imported FRD/ZMA files from Eminence specs sheets
Added 2" between driver centers (vertical offset)
Adjusted Z offset (-0.052m) to account for deeper driver and flush baffle
Changed crossover components based on visual curve fitting
L2 2.0 mH (0.26 ohm DCR)
C2 18 uF
C9 18 uF
L9 0.45 mH (0.046 ohm DCR)

3.3 ohm resistor in parallel w/tweeter (was this for protection?)

I think the model FR curve looks good...

Questions:

The QSC/DE250 FRD/ZMA curves were measured (by Zilch) in the PE trap cabs. I'm not using the trap cabs. Is this an issue? As I have neither waveguides nor drivers, this is the best I can do for now. More parts to be ordered soon...

The 3015 FRD/ZMA curves are from the spec sheets. I have the 3015's up and running with the standard eWave HF setup. Is it worth running FR testing to get in-situ FR curves to use? Or is what I have close enough?

Do I need to run the box model to get impedance data or anything else useful for modeling?

What else do I need to look at?

Thanks in advance!

[Zilch]

Re: Flex Your PCD Mettle:

It'd be an exceptional circumstance for inputs of manufacturer's published curves to provide as accurate a model as those from actual devices in the final (or nearly so) cabs. In one example here, I used a $150 measurement setup and the free downloadable HOLMImpulse for this, and subsequently verified the result with CLIO, which was down for upgrade at the time.

Ultimately, it becomes an interactive iterative loop between concurrent PCD and measurement windows. The measured location of the inverse null hones in the offsets, and PCD's spinners and direct-value inputs facilitate component selection. In some of the instances presented here, the correlation in this process has been stunning.

It's surely fun working with models and measurements separately, and I often put off acquiring the requisite input data long enough to build an initial intuitive attempt, but in the final analysis, the real power lies in their real-time juxtaposition....

25029/391=64.0128

[donprice]

Re: Flex Your PCD Mettle:

That was a very diplomatic way to say "measure the dang things". DE250's on order. Is there trick to measuring the response of the HF driver without blowing it? Run the sweep from 800Hz up?

[Zilch]

Re: Flex Your PCD Mettle:

A protection cap in series, like 33 uF or larger, one octave or more below your lowest frequency of interest, but above 200 Hz....

[penngray]

Re: Flex Your PCD Mettle:

If anyone has been waiting on QSC HPR-152i waveguides. It looks like QSC has them in their parts stock again. I just received an email that 6 are being shipped to me.

[Zilch]

Flex It Round #4.1 - EconoWave 4x

Hundreds of thousands of Acoustic Research's entry-level AR4x acoustic suspension speakers were manufactured over the course of a decade, which are now standard fare in thrift stores and yard sales virtually everywhere for chump change. I've never paid more than $30 a pair for these venerable vintage update candidates, some in excellent condition, acquiring several pair at substantially less, and others for free, even:




As shown above, the 8" square 90° x 50° progressive transition waveguide is a perfect match, this time using the Selenium D2500Ti compression driver, a neodymium version of D220Ti, which I believe will also fit. Here's my first attempt as designed in PCD:




Directivity measurements suggest that the stock 1/2" baffle recess is not a significant issue:

[Zilch]

Re: Flex Your PCD Mettle:

The files for PCD are attached below. Measurement distance 44", center to center between drivers 8".

[Zilch]

Sidebar on Directivity:

Before upgrading AR4x to waveguide HF, we designed a modern crossover for the stock AR4x (left in the pic above) in the Classic Speaker Pages forum, verified it in PCD, and ran measurements on the result. Toggle among the waterfall images to compare directivities of these two AR4x variants and Spitwad:

http://techtalk.parts-express.com/attachment.php?attachmentid=9657&stc=1&d=1278455717

http://techtalk.parts-express.com/attachment.php?attachmentid=9632&d=1278388458

http://techtalk.parts-express.com/attachment.php?attachmentid=9658&stc=1&d=1278455717

[Skywave-Rider]

Re: Flex Your PCD Mettle:

Wildly beamy on the AR4x with re designed x-o and stock transducers, I assume.

That's got to have crap power response.

Should I also assume the stock x-o with stock transducers looked EVEN WORSE?

Damn....

[Zilch]

Re: Flex Your PCD Mettle:

I s'pose I could rehab a pair stock for comparison, but it's sorta moot because the fundamental directivity would be the same. The redesigned crossover got it pretty flat on axis.

Here's the threads:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=5815

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=5985

PCD files for the stock drivers are in the second one, if anybody wants to work with those.

It's not uncommon for the highs to be elevated on-axis with an assumption that the listening will occur somewhat off that, where the response is flatter, but the approach falls apart with such narrow dispersion in the VHF as is evident in this instance from vintage cone tweeters. So, use modern domes, maybe? That doesn't work either because they are not mirror-imaged, and the consequences are significant, as may be seen in the polars. The waveguide cleans up all of that....

Edit: Here's the equivalent horizontal polar map with the stock drivers and the updated crossover:




Toggle:

http://techtalk.parts-express.com/attachment.php?attachmentid=9630&d=1278388354

http://techtalk.parts-express.com/attachment.php?attachmentid=9663&d=1278469380

[Zilch]

Re: Flex Your PCD Mettle:

EconoWave components in the latest PE sales flyer:

#270-318 Dayton Audio H6512 Waveguide - $13.50
#264-270 Selenium D220Ti Compression Driver - $40.80
#245-325 PA Knock-Down Trapezoid Birch Cabinet - $69.00
#295-032 Dayton Audio PA310-8 12" Pro Woofer - $74.85

That's $198.15 each less crossover, with free shipping.

I'll be posting this combination using the bolt-on version of D220Ti and QSC waveguide here next....

[Greg01]

Re: Flex Your PCD Mettle:

Zilch

My QSC waveguides finally arrived. I had forgotten I had ordered them.

I was wondering if you had tried foam in the waveguide like Brandon in the HTGuide forum thread. If you did, what were the results?

I am now geared up to try the Econowave deluxe, just curious about the foam.

[Zilch]

Re: Flex Your PCD Mettle:

How the Geddes foam theoretically works via attenuation is well documented. No one has yet demonstrated that they have found the right stuff, so thus far, Earl is the only source, and he does not sell it cheap. He stated in another forum that what Brandon used is incorrect; I have not pursued the known alternative sources as an option....

[Greg01]

Re: Flex Your PCD Mettle:

Pete & Zilch

I am hoping to throw down a friendly challenge within this challenge. I am going to build a speaker using the drivers from the Econowave Deluxe. However, as elegant and simple as the crossover for the Deluxe is, I am wondering what could be accomplished with an additional notch here or zobel there.

Please keep in mind, I am still on a budget, but wouldn't mind splurging on a few extra components. Are there any recommendations for further tweaking this crossover. However, if you don't really think this driver complement could benefit from a reasonable amount of refinement just let me know. So, show me what ya got.

[augerpro]

Re: Flex Your PCD Mettle:

How the Geddes foam theoretically works via attenuation is well documented. No one has yet demonstrated that they have found the right stuff, so thus far, Earl is the only source, and he does not sell it cheap. He stated in another forum that what Brandon used is incorrect; I have not pursued the known alternative sources as an option....

And I have had Earl's waveguides and so had both types of foam in my hands and I can tell you he is...mistaken.