Flex Your PCD Mettle:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

I haven't read this whole thread or the AK one either. I did see Fastbike's standard Econowaves in old Radio Shack cabs, and I liked that project. I just procured a pair of remarkably nice Pioneer cabs from the 70s. About 1.7 cu. ft., 3/4" particle board, they even have a brace and carpet padding inside. I will be ordering parts shortly.

I have a question for the experienced Econowavers. Do you leave these on the floor, or raise them up a bit, and tilt them back perhaps on stands?

I will post a few construction pics soon.

It depends on how you mount the woofer; behind a thick baffle, and the whole forward lobe position changes. You can take the files from any of the threads, plug in the acoustic offsets, and then run the min phase versions of the response files, and sim any axis you want. It was really interesting to see how well Zilch's data, fed into PCD, predicted what he was measuring. It worked so well, that it brought up a correction to the way PCD was calculating off axis behavior.

And in most cases, due to the depth of the waveguide, it puts the tweeter acoustic center behind the woofer. The example I posted above would be for a stand mount version, pointing straight ahead, but you sacrifice group delay at the crossover point, since the tweeter is actually 180 degrees out, for an in-phase summation at the crossover point, on that particular axis. It would be great to use a 15" woofer with such a deep guide, or figure some way to move the 12" woofer back, to better line up with the tweeter, so that you don't have to compensate for so much acoustic offset.

[djg]

Re: Flex Your PCD Mettle:

I haven't read this whole thread or the AK one either. I did see Fastbike's standard Econowaves in old Radio Shack cabs, and I liked that project. I just procured a pair of remarkably nice Pioneer cabs from the 70s. About 1.7 cu. ft., 3/4" particle board, they even have a brace and carpet padding inside. I will be ordering parts shortly.

I have a question for the experienced Econowavers. Do you leave these on the floor, or raise them up a bit, and tilt them back perhaps on stands?

I will post a few construction pics soon.

[Zvuchniak]

Re: Flex Your PCD Mettle:

Only when you want to make a system with the listening axis straight ahead, and the woofer mounted that far forward of the tweeter.

That FRD and ZMA files are from econowave delite so we are talking about the design that is already done. Measurement provided by Zilch.

So it is not the question of what i want. It is more about what should we do in case that you can't change the speaker cabinet. What you see is what you get

[Pete Schumacher]

Re: Flex Your PCD Mettle:

If i just reverse + and - on the tweeter polarity button will it work fine ?

Thanks in advance Pete

Only when you want to make a system with the listening axis straight ahead, and the woofer mounted that far forward of the tweeter.

For calculating acoustic offset, you leave the tweeter polarity positive, just like you did. That calculation is about a perfect a match as you could have hoped for.

In order to do the crossover I did, for a listening axis in between the woofer and tweeter, you need to reverse the tweeter polarity to get good summation at the crossover point for 4th order slopes.

If you start moving the woofer back toward the tweeter, you will find that it will revert back to positive polarity when acoustic centers are lined up.

[Zvuchniak]

Re: Flex Your PCD Mettle:

I just had this exact same If you go to the end where important updates are mentioned, he notes the change to polarity that's reflected in the pop-up. It's all handled in the equations behind the calculations. The sign of the offset is set in the background.

And I've corrected the polarity of the tweeter wiring in my previous post. The large offset of the woofer ahead of the tweeter requires the tweeter to be reverse polarity and sum like it did in the sim.

If i just reverse + and - on the tweeter polarity button will it work fine ?

Thanks in advance Pete

[Pete Schumacher]

Re: Flex Your PCD Mettle:

I just had this exact same conversation with Jeff.

That part of the instruction page needs an update, and I think you can actually make it yourself.

If you go to the end where important updates are mentioned, he notes the change to polarity that's reflected in the pop-up. It's all handled in the equations behind the calculations. The sign of the offset is set in the background.

And I've corrected the polarity of the tweeter wiring in my previous post. The large offset of the woofer ahead of the tweeter requires the tweeter to be reverse polarity and sum like it did in the sim.

All of this can be modified, by mounting the woofer to the back side of a 1.5" thick baffle with big roundovers or chamfers, pushing the woofer back closer to the tweeter acoustic center.

This is one reason why a stand mount Econowave might not be the best option. Leave it on the floor with the tweeter above the woofer, and the relative acoustic offset changes to your benefit at the listening position. Everything depends on your target listening axis, and you can actually pick that based on the acoustic offset you have measured from the position you did.

[Zvuchniak]

Re: Flex Your PCD Mettle:

Now, if negative value on Z axis means that acoustic center is closer to the listener (subtratcs distance), and positive value means that acoustic center is farther from the listener (adds distance), can we conclude that acoustic center of Deltalite is 11cm farther from the B&C DE250-8 despite the waveguide physical depth ?

In that case, midbass mounting on the back side of the front pannel would be unwanted because of adding more distance unnecessarily. The next image shows that acoustic offset is frequency dependent (taken from Loudspeaker Design Cookbook):

[Zvuchniak]

Re: Flex Your PCD Mettle:

Actually, the tweeter is further behind the woofer, since the woofer offset is positive. Click on the Driver Z Offset cell, and a pop up will explain the polarity.

But the instructions page in PCD says this:

For the Z-Offset; farther back, like with a woofer's voice coil is a positive value, since it is added to the listening distance. A negative value here would be subtracted to indicate that the driver's acoustic center is closer to the listening point.

Woofers Y offset is -0,133 and for tweeter is 0,133 as can be seen on the image:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Hey guys. I have some questions (maby dumb ones) so please shut me up when you think that i'm babbling :D

I've been playing with PCD some more. Zilch (thanks again big guy) gave measurements details for Delite as .FRD and .ZMA for it in this post:

http://techtalk.parts-express.com/sh...&postcount=136

I tryed to find the acoustic offsets for Deltalite and B&C DE250-8 in PCD using guide in PDF from Jeff Bagby (to who i dont know how to thank enough for everything he did for DIY community).

My question is this... Since Deltalite II 2512 is aproximetly same depth and size like Kappalite 3012 i entered same distance (-0.065m) at Z axis in PCD but came up with nothing. Then i tried to find it myself like the guide said and this is with what i came up with:

.FRD and .ZMA imported in PCD and then adjusted measuring distance (47") and vertical offsets (10.5"):

http://img13.imageshack.us/img13/408...maimported.jpg

This is acoustic offset at Z axis that gave me identical response:

http://img403.imageshack.us/img403/9...tersdeadon.jpg

Could this be true or am i doing something wrong here ? Acoustic offset which shows that Deltalites acoustic center is 11cm (4.33") behind (further from the listener) from the QSC B&C DE250-8 ? Physically the diference is almost the same like with Deluxe.

Set your woofer Y offset to -.133. It's below the mic, and without the sign, you have it coincident with the tweeter. Won't make any difference to the acoustic offset calculation though.

Actually, the tweeter is further behind the woofer, since the woofer offset is positive. Click on the Driver Z Offset cell, and a pop up will explain the polarity.

To get that 2-way right, you have to invert the tweeter polarity.

I just ran a sim.

Woofer: 3mH series, shunt 15uF, series .5mH to woofer +

Tweeter: 5 Ohm in series with 6.8uF, shunt .3mH in series with 4 Ohm, series 15uF to tweeter -, and 6.2 Ohm across tweeter terminals.

Gives a nice response to start tweaking.

[Zvuchniak]

Re: Flex Your PCD Mettle:

Hey guys. I have some questions (maby dumb ones) so please shut me up when you think that i'm babbling :D

I've been playing with PCD some more. Zilch (thanks again big guy) gave measurements details for Delite as .FRD and .ZMA for it in this post:

http://techtalk.parts-express.com/sh...&postcount=136

I tryed to find the acoustic offsets for Deltalite and B&C DE250-8 in PCD using guide in PDF from Jeff Bagby (to who i dont know how to thank enough for everything he did for DIY community).

My question is this... Since Deltalite II 2512 is aproximetly same depth and size like Kappalite 3012 i entered same distance (-0.065m) at Z axis in PCD but came up with nothing. Then i tried to find it myself like the guide said and this is with what i came up with:

.FRD and .ZMA imported in PCD and then adjusted measuring distance (47") and vertical offsets (10.5"):

http://img13.imageshack.us/img13/408...maimported.jpg

This is acoustic offset at Z axis that gave me identical response:

http://img403.imageshack.us/img403/9...tersdeadon.jpg

Could this be true or am i doing something wrong here ? Acoustic offset which shows that Deltalites acoustic center is 11cm (4.33") behind (further from the listener) from the QSC B&C DE250-8 ? Physically the diference is almost the same like with Deluxe.

[greywarden]

Re: Flex Your PCD Mettle:

Yeah but it's long been my contention that you need a 1.4" CD or larger to play to 700hz nicely and now the +10hz content suffers on both FR and directivity still leaning towards a three way only now with a super tweeter of sorts. Not a bad thing, but still a 3way. Better to fatten up the bottom IMO.

They make a 1", 1.4" and 2" version, I don't recall there being much of a difference between them...

[JoshK]

[fastbike1]

Re: Flex Your PCD Mettle:

Sizing depends on your woofer choice, the F3 you want and the waveguide you've chosen. Easy enough to figure out.

Anyone use the knock down birch cabinets to build an econowave build? I am just wondering if the sizes work.

[JoshK]

Re: Flex Your PCD Mettle:

Anyone use the knock down birch cabinets to build an econowave build? I am just wondering if the sizes work.

[edlafontaine]

Re: Flex Your PCD Mettle:

Does anyone know anyone near Wilmington, NC that is a Pro Audio DIY hobbyist/expert?

He's not in Wilmington...a little further up-country, I believe. Michael Mardis, aka Pano @ diyaudio

http://www.diyaudio.com/forums/members/pano.html