Looking for some help with Zaph's waveguide design,

[sphynx_000]

This is a continuation of a project started on avsforum.com, (thread)
I came here hoping I would receive more info, and possibly some advice from zaph


I am building the waveguide project on zaph's site but substituting the P18RNX for the CA18RNX . I know this would normally be advised against, but I already had a pair of the polycone woofers and wanted to save a few bucks.

As I am new to speaker building I came to the forums to get some advice. A couple members at avsforum tweaked the box and crossover for me to adapt the different woofers.

Now I am just looking for advice on how the adjusted system looks. If someone has measured the P18RNX and could comment on its performance with the new crossover that would perfect.



The system adjustments are

CROSSOVER (perfectionist )
C0- 3.9 uF
L1- .7 mH
R2- .41 ohm
C3- 6.2 uF (changed from 6.8 uF)
L4- 1.75 mH (changed from 2.0 mH)
R5- 10 ohm (changed from 7.0 ohm)
C6- 16.0 uF
R7- 1.5 ohm
L10- 4.0 mH
R11- .21 ohm

CABINET
-change depth from 10.75 inches to 8.5 inches (19.5 liters to 15 liters)
-advised on trying tuning options of 85mm and 75mm (not sure of the freq.)




Basically, I am just looking for a second opinion on how the tweaked system looks before starting construction. Any help or advice for the build would be greatly appreciated.

[sphynx_000]

anyone?

[Jed]

looks like you are getting good advice over there-- too bad you can't measure it because it will never be perfect until you can do that.

[Dennis H]

Yeah, what Jed said. Zaph's original design is based on his measurements and his fine tuning by listening to the speaker with its crossover and enclosure. Change the drivers with no measurements and no listening and you're a test pilot. It'll probably sound pretty good (at least not terrible) but nobody can really help you get from okay to great without building the same thing and giving it a listen.

[sphynx_000]

I guess this is the point I am stuck at for now. Hopefully someday I will get around to purchasing some measurement equipment and learn how to fine tune a system.

But for now, I think most people would agree the system is free from obvious flaws (at least what can be seen on paper)... That being said, I will probably start the build tomorrow.

[Martyn]

If I were you I'd sell the P18 drivers, buy the CA 18 drivers, and build the speakers exactly as Zaph designed them. Like most speaker designers, he puts a tremendous amount of thought and effort into optimising his designs - why would you settle for something sub-optimal to save a few bucks?

[sphynx_000]

I should have done that right away but it is too late now. I can't imagine digging out of this hole for less than $100.

If I had more money to spend at the moment, maybe I would do it right. However I have already spent more than I have budgeted. I am going to have to work with what I have. I am kind-of pissed now that I jumped into the project like this.

[BretH]

Maybe build them with the drivers you have and look forward to either being able to measure and tweak to make it better or purchase the spec'd drivers. You'll likely be happy now and have something to look forward to as well.

[sphynx_000]

Yeah, that sounds good.

Only problem there is I am changing the cabinet too.

Hopefully later on I will learn to measure and tweak the system myself. I am confident this will eventually meet up to my expectations. For now I am just going to get the thing built. I will worry about other problems when and if they arise.