Flex Your PCD Mettle:

[badman]

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....

AFAIK he's suggested that the 30PPI (Or is it 40) reticulated is appropo- it's what I use and it works nicely. It's sold as aquarium filter foam.

[Carl_Huff]

Re: Flex Your PCD Mettle:

Is QSC still willing to sell their 152i waveguide to DIYers? I can't seem to find the part order page for it anymore on their site.

[Zilch]

Re: Flex Your PCD Mettle:

It's returning "Under construction" for me presently. If there has been a change in policy, I believe we'd be notified.

Call them to place an order, instead, perhaps.

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.

I believe Pete and I agree that Deluxe might benefit from an additional notch, as discussed earlier in this thread. I have not gone back to try this, however, but may have opportunity when swapping in the Dayton Pro woofer and Selenium driver for the next round. I suspect that it will be an optional supplement:

http://techtalk.parts-express.com/showthread.php?p=1647653#post1647653

[Texan]

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

Sorry I have been trying to keep up with this but…

You did do one like this, or you plan to do one like this, or…?
I suspect these would be a nice higher value alternative to the PA speakers I just finished.
The new woofers showed up just after I started.:rolleyes:

[Zilch]

Re: Flex Your PCD Mettle:

You did do one like this, or you plan to do one like this, or…?

I have not done one like this, but all except the woofers are standard EconoWave fare used earlier in this thread, if we accept that the waveguide is a clone of the JBL/Pyle.

Others have been wanting to know if the bolt-on Selenium D220Ti drivers can work well with the larger QSC 152i waveguide used in Deluxe, so I will try that first with the Dayton Pro 12", then swap them into cabs using the Dayton waveguide and thread-on Seleniums, verifying that combination, as well.

[Zilch]

Selenium Driver Uniformity

Are the D2500Ti-Nd drivers really equivalent to D220Ti?

How much unit-to-unit variability is there within the two types?

I had to clean two of them up, one of each type, and it looks like a couple more might benefit from similar attention.

Here on my prototype AR4x eWave crossover, pairs of different vintages at least 6 months apart:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Hey Zilch,

A buddy of mine is working up a clone of the QSC circular waveguide, same profile, but with a larger opening radius, to accommodate 28mm high sensitivity fabric dome tweeters. There's a few good 93dB+ candidates out there that would make for ideal toppers in a true budget system. Even most 91dB candidates would find plenty of woofers to match up with.

He said he was going to be getting started this week in building up the prototype. The first project he had in mind was putting it and the RS28F with an 8" woofer. I'd like to put it with a 10" myself.

Another friend is talking about major HT upgrade, and the AE TD10M paired with a waveguide loaded AirCirc 6600 came up as a possible replacement for his existing 7 channels. I heard the same tweeter in a waveguide crossed at 875Hz to an 8" mid. It was remarkable. I'm hoping this waveguide will give similar benefits of extension and effortless output.

[Zilch]

Re: Flex Your PCD Mettle:

Hi, Pete!

Whether it's conventional domes or compression drivers exciting them, waveguides have clear advantages worthy of pursuit. We have a baseline for comparison in this thread.

My experience with domes is severely limited, but two issues must be addressed:

1) The action is at the throat, and nobody has yet defined an optimum contour matching a dome's quasi-spherical wavefront that would rival the evolved performance of compression driver assemblies. Yes, the efficiency advantages at the lower frequencies are clear, but achieving wide bandwidth constant directivity remains a challenge.

2) In larger sizes, round axisymmetric waveguides increase the minimum center-to-center distance between woofer and waveguide which, in combination with the crossover frequency, determines the height of the forward vertical lobe. As we've seen here, pattern control, which is related to waveguide size, is also a factor in establishing the optimum tradeoff.

A possible answer to some of these issues is an elliptical axi-asymmetric waveguide, of which we do have an oblate spheroid example worked out by pros with far greater skills and resources than I could ever muster:

http://www.jblproservice.com/pdf/LSR6300/LSR6328P.pdf

http://www.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=568

I have provided what information I know about this particular dome-driven waveguide in another thread on this forum. It is clearly possible to succeed....

[dantheman]

Re: Flex Your PCD Mettle:

Zilch, I've heard those particular speakers several times, but always on a shelf and essentially against a wall. I'd say I didn't hear a honk, but I've never heard familiar music through them. I'd sure like to hear them on stands and away from the walls. Or better yet, just measure them up. Can you link the thread on those WGs?

Have you seen my measurements on the similar Behringer B2031P?
polar in 11.25 degree steps:

Overlaid impulses:

AVG or polar curves:

Center axis dip at 15k. $152/pair.:eek: Cheap.

Dan

[penngray]

Re: Flex Your PCD Mettle:

Hi, Pete!

Whether it's conventional domes or compression drivers driving them, waveguides have clear advantages worthy of pursuit. We have a baseline for comparison in this thread.

My experience with domes is severely limited, but two issues must be addressed:

1) The action is at the throat, and nobody has yet defined an optimum contour matching a dome's quasi-spherical wavefront that would rival the evolved performance of compression driver assemblies. Yes, the efficiency advantages at the lower frequencies are clear, but achieving wide bandwidth constant directivity remains a challenge.

2) In larger sizes, round axisymmetric waveguides increase the minimum center-to-center distance between woofer and waveguide which, in combination with the crossover frequency, determines the height of the forward vertical lobe. As we've seen here, pattern control, which is related to waveguide size, is also a factor in establishing the optimum tradeoff.

A possible answer to some of these issues is an elliptical axi-asymmetric waveguide, of which we do have an oblate spheroid example worked out by pros with far greater skills and resources than I could ever muster:

http://www.jblproservice.com/pdf/LSR6300/LSR6328P.pdf

http://www.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=568

I have provided what information I know about this particular dome-driven waveguide in another thread on this forum. It is clearly possible to succeed....

Zilch, what is JBL's part ordering site link again? I wonder if some of those LSR6328p parts are available like the tweeter/waveguide.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Hi, Pete!

Whether it's conventional domes or compression drivers driving them, waveguides have clear advantages worthy of pursuit. We have a baseline for comparison in this thread.

My experience with domes is severely limited, but two issues must be addressed:

1) The action is at the throat, and nobody has yet defined an optimum contour matching a dome's quasi-spherical wavefront that would rival the evolved performance of compression driver assemblies. Yes, the efficiency advantages at the lower frequencies are clear, but achieving wide bandwidth constant directivity remains a challenge.

2) In larger sizes, round axisymmetric waveguides increase the minimum center-to-center distance between woofer and waveguide which, in combination with the crossover frequency, determines the height of the forward vertical lobe. As we've seen here, pattern control, which is related to waveguide size, is also a factor in establishing the optimum tradeoff.

A possible answer to some of these issues is an elliptical axi-asymmetric waveguide, of which we do have an oblate spheroid example worked out by pros with far greater skills and resources than I could ever muster:

http://www.jblproservice.com/pdf/LSR6300/LSR6328P.pdf

http://www.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=568

I have provided what information I know about this particular dome-driven waveguide in another thread on this forum. It is clearly possible to succeed....

I'm sure we'll be experimenting with throat treatment, namely felt layers to bring the faceplate and waveguide together. From what others have learned matching waveguides to tweeters, there certainly is promise. Each of the other methods I've seen involves modifying the waveguide profile by shortening the depth until a correct diameter is reached. We'll be keeping the existing profile to start with and see if that improves performance or not.

[Zilch]

Re: Flex Your PCD Mettle:

Zilch, what is JBL's part ordering site link again? I wonder if some of those LSR6328p parts are available like the tweeter/waveguide.

http://www.jblproservice.com/forms/parts_order1.html

You need both driver and waveguide; the transition from round to elliptical begins with the tweeter front plate.

[Zilch]

Re: Flex Your PCD Mettle:

Have you seen my measurements on the similar Behringer B2031P?

Have we figured out which Behringer Geddes found measured so well for his directivity software demo?

What's that waveguide look like?

JBL EOS pics here:

http://techtalk.parts-express.com/showthread.php?p=1616506#post1616506

No polars in the lit, but JBL claims "within 1.5 dB" 60° x 30°. I'm betting that's the listening window average curve, not the actual directivity....

[dantheman]

Re: Flex Your PCD Mettle:

Geddes either measured the 2030A or the 2031A. My bet is the 2031A. I measured the passive version.
No way to just order this WG.

The JBL would be interesting to see measurements on.

Dan

[Zilch]

Re: Flex Your PCD Mettle:

Did you measure the verticals, Dan?

That's quite a bit of center-to-center distance there, looks like....