Flex Your PCD Mettle:

[Zilch]

Re: Flex Your PCD Mettle:

]Mine's not broken....

KLH-17 econo-wave on axis response and impulse response.

HI Carl!

Your build has me tempted to do it again using PCD. If so, I'll remeasure the originals as baseline.

[Thinking I'll try to accomplish image stabilization with asymmetric directivity waveguides in those this time. ]

The shadows know. ;)

Unless you or someone else already has it, I need to track down the post (in diyAudio, as I recall,) showing exit angles of various compression drivers.

[It's MADNESS, the variability...! :( ]

[carlspeak]

Re: Flex Your PCD Mettle:

HI Carl!

Your build has me tempted to do it again using PCD. If so, I'll remeasure the originals as baseline.

[Thinking I'll try to accomplish image stabilization with asymmetric directivity waveguides in those this time. ]



[It's MADNESS, the variability...! :( ]

I can get you those custom 17+ baffle boards for a good price! I've built yours. It's time you built mine!

[Zilch]

Fixing Directivity:

Once again exhibiting his inconsiderable woodworking acumen, the Zilchster shimmed the PE KDT cab baffle forward using 1x2 stock:




Since the baffle was out, here's the alignment with this large format compression driver:




There's still a bit of lip, about 3/8":




Did it work?

[Zilch]

Re: Flex Your PCD Mettle:

Toggle the normalized maps:

Before: http://techtalk.parts-express.com/at...6&d=1281474687

After: http://techtalk.parts-express.com/at...5&d=1281575907


Here's the minimalist look:

[donprice]

Re: Flex Your PCD Mettle:

Kappalite 3015 & QSC152i/DE250
Measured response with cabinet on back - 44" on axis, mic is 60" from floor and ceiling. Previous measurements presented were collected with grill in place to account for diffraction effects. Looking at the graphs, the grill is part of the problem with the gate values. First graph compares FR with and without grill in place - note difference in gating values. Second graph is same data except gate is adjusted to same value for both. Looks to me like the grill has little effect on the woofer. So which gate value and resulting FR curve is better to use in PCD?

Next up, DE250 grill and gating effects....very little effect as seen in the third graph.

[Zilch]

Re: Flex Your PCD Mettle:

I do not know how HOLM "decides" on where to present the gate in its initial display. I set it manually, the same for both LF and HF response, based upon where the first reflection appeared in the impulse response, in order to get the highest resolution at lower frequencies without affecting the high ones.

What matters is that the resolution not cut off until well below the anticipated crossover frequency, and that time zero be the same for all curves, i.e., at the start of the pulse, as determined by HOLM according to which option you choose....

[Skywave-Rider]

Re: Fixing Directivity:

Once again exhibiting his inconsiderable woodworking acumen, the Zilchster shimmed the PE KDT cab baffle forward using 1x2 stock:




Did it work?

There ya go.
Looks much better!
I assume the other JBL CD is equally improved.

[Zilch]

Re: Flex Your PCD Mettle:

It's the second definitive illustration of the impact of edge effects upon directivity in this thread. I don't believe I've ever seen a presentation of an empirical determination such as these previously.

Like me, it would appear that some experts need to re-evaluate their perspective on the immunity of controlled directivity waveguide designs to/from these factors.

[And not forget the woofer, either.... ;) ]

[carlspeak]

Re: Flex Your PCD Mettle:

It's the second definitive illustration of the impact of edge effects upon directivity in this thread. I don't believe I've ever seen a presentation of an empirical determination such as these previously.


[And not forget the woofer, either.... ;) ]

And that's why I added a new BB on top of the old one on my 17+ project. Just wish I could have rounded the edges more than I did.

[bruson]

Re: Flex Your PCD Mettle:

Hi all,

I ordered a QSC 152i back in May and during the delay in their shipping, I got to rethink what I needed for my space. Which is a smaller size. 10" woofer and WG.
So I decided to kind of clone the Gedlee Nathan with some inspiration from Bouska.

Drivers are the B&C DE 250 and B&C 10PS26. I liked their fairly flat FR, not that I get that when mounted.

I used the DDS ENG 1-90 from US Speaker ($120 ea). I know the differences between the round WG and the horizontal WG. Both Geddes POV and Parham's and your's here in this thread. And I chose round for better or worse.



I have only roughed in the x-over by ear.

I am looking at getting a mic, PS and cables from PE (a Dayton EMM6 mic from PE, a Behringer Xenyx 80)

I've been reading HOLMimpulse directions and found them not very clear for a non technical first time user of FR software, ME!

Is there a simple easy to use free, or not too expensive software readers could recommend? Simple and easy being the key phrase for me.

Has anybody already done testing of the B&C DE 250 on the DDS ENG 1-90 so I can use their info, or xover (Yeah, I'm lazy too)?

To show some more of my ignorance: What are the equations you use to reduce the peaks in the FR? Is there a website for plugging in the info and get good results?


If this is the wrong board for these kinds of questions which board would be better?

Thanks

[Zilch]

Re: Flex Your PCD Mettle:

You're gonna have to dig into HOLMImpulse; it'll be easier once you get it up and running. At this level, only an iterative process of measurements and sim can achieve the desired result efficiently.

As Dickason observes, the formulas for notch filters will only get you in the ball park. PCD hones them closer when combined with actual impedance and response measurements. You'll see below, it has all but nailed my spike killer....

[Zilch]

EconoWave HPB+ Data:

Raw driver responses:




Here, in PCD:




The measured result:

[Zilch]

Re: Flex Your PCD Mettle:

The files:

[Zilch]

Re: Flex Your PCD Mettle:

It's most often others who find interesting stuff in my posted plots (Skywave and EarlK, most notably), but toggle this pair:

HPA: http://techtalk.parts-express.com/at...8&d=1281236457

HPB+: http://techtalk.parts-express.com/at...6&d=1281647427

The blue curves reveal the difference between the response of the JBL 2262HPL woofer in the stock KDT cabinet, B+ being with reduced baffle edge overhangs and slightly increased cab volume resultant of moving the baffle 3/4"+ forward.

The red plots compare the raw responses of the 3" medium-format 2432H vs. the 4" large-format 2452H-SL compression drivers on the same waveguide; it's clear why the same highpass filter works for both of them, a rare occurrence, in my experience.

Not definitive, and probably not worthy of generalization, either, but ancillary fun for curve junkie speakergeeks, nonetheless....

[NEO Dan]

Re: Flex Your PCD Mettle:

It's most often others who find interesting stuff in my posted plots (Skywave and Earl K, most notably), but toggle this pair:

HPA: http://techtalk.parts-express.com/at...8&d=1281236457

HPB+: http://techtalk.parts-express.com/at...6&d=1281647427

The blue curves reveal the difference between the response of the JBL 2262HPL woofer in the stock KDT cabinet, B+ being with reduced baffle edge overhangs and slightly increased cab volume resultant of moving the baffle 3/4"+ forward.

The red plots compare the raw responses of the 3" medium-format 2432H vs. the 4" large-format 2452H-SL compression drivers on the same waveguide; it's clear why the same highpass filter works for both of them, a rare occurrence, in my experience.

Not definitive, and probably not worthy of generalization, either, but ancillary fun for curve junkie speakergeeks, nonetheless....

Indeed an interesting similarity on the compression drivers. Did you not need the spacer/adapter for both of these. I had thought it might have been problematic. Do either of these drivers have cleaner CSD than the DE250?