Speaker idea based on Zaph ZD5, thoughts please, Zaph?

[wigginjs]

I was really intrigued with Zaph's ZD5 design, but I wanted a full-range solution so I've integrated a subwoofer cabinet using two Aurasound NS10-513-4A 10" drivers . I'm interested in critisism about anything from asthetics to real design flaws. Information:

* The face of the top cabinet is 7" and the top cabinet is 14" tall. I wanted to keep the same baffle dimensions as the original speaker for defraction purposes, but also wanted to integrate it with the lower bass cabinet. The ZD5 crossover will remain unchanged.

* The distance from the center of both woofers and the center of the mid/tweeter is about 22". The total cabinet is just over 45" tall.

* I plan to cross the top cabinet to the bottom cabinet at about 120Hz with a LR4 active crossover (something cheap, probably Behringer).

* This will be driven with a Parasound HCA-1206 6 channel amp. Each channel is about 120W@8ohm. Two pairs of channels will be bridged to provide about 350W@8ohm and crive the woofer cabinets leaving the two other channels to drive the top cabinets. The Aurasound drivers are 4ohm nominal and will be wired in series.

* Both top and bottom cabinets will have fairly extensive bracing and thick walls. This will result in about 2.3ft^3 for the bottom cabinet. This results in a Qtc=0.573.

I'd like to use an active crossover that would provide equalization for the woofer cabinet, but I've had bad experiences with PC based crossovers and all of the active digital crossovers I've read about seem to need external 6-channel volume controls or else they are very noisey. I like the sealed design for a number of reasons and would like to stick with it. Graphs shown below are of the woofer cabinet driver with 350W, they show SPL and driver excursion.

Oh, also, cabinets are shamelessly ripped from a concept design ShinOBIWAN posted.

[augerpro]

Well since you changed the baffle and went from 2way to 3way I'd say you're looking at a total redisgn of the ZD5 crossover. Not much in Zaph's design will apply to what you're doing.

[wigginjs]

Well, I realize the baffle is different because the left and right edges now angle off at 45 degrees instead of 90 for about 3.5". The actual face of the top cabinet remains unchanged however. Also, why would adding the subwoofer cabinet result in a crossover redesign for the ZD5?

[tktran303]

VENT ON
<sigh>

Why the hell doesn't this forum have a FAQ or a RTF'inM section??
VENT OFF

You are talking about a completely different speaker.

[wigginjs]

<sigh>

Why the hell doesn't this forum have a FAQ or a RTF'inM section??

Are you serious? You really feel like this idea is so ridiculous and has such basic flaws that I must not even have knowledge that would be covered in a FAQ?

* I plan to cross the top cabinet to the bottom cabinet at about 120Hz with a LR4 active crossover (something cheap, probably Behringer).

If I cross the ZD5 top cabinet to the lower subwoofer cabinet with an active crossover how does this effect the passive crossover design for the top cabinet?

[hongrn]

Either you design your own speakers and crossovers, or follow EXACTLY the ZD5 design, but asking John to redesign his stuff to accommodate your completely different box and drivers is one of his pet peeves. He can be quite caustic on that subject.

Hong

[wigginjs]

Did you guys read my post at all? I'm not asking him to redesign anything, nothing needs to be redesigned. All this is, effectively, is the ZD5 with a slightly changed cabinet, but the same face dimensions, placed on top of a subwoofer cabinet that is used as a stand.

I'm at a total loss here for what you guys think the problem with this is. I am not using a passive crossover for the subwoofer, I don't need to change Zaph's crossover design because his speaker hasn't been changed. If I put the ZD5 on a stand, move the subwoofer I designed out from under it, and described the EXACT same setup would that be more acceptable?

[tktran303]

Sorry for my rudeness.

I was under the impression that you wanted to build a slightly modified ZD5.

It's clear to me that you want to build a completely different speaker, but use John's crossover. The reason why John's ZD5 probably sounds as good as it does, is because the crossover was painstakingly optimised to yield an acoustic LR2 response, and exhibit a vertically symmetrical polar response, on that baffle, which was 7" wide with 1/2" roundovers.

Of course we can use baffles of any width we want, with 45 degree cut sides, then stack them on top of dual 10" subwoofers, crossed over at any frequency we like. But my prediction of the end results would be as good yours- ie. SHRUG.

Uness you build it and measure it (or model it with FRDC's BDS), your guess is as good as mine.

Would it sound different? YES
Could you live with the differences? PROBABLY
How different? WHO KNOWS?

John's far too nice a guy. But when you start to change a design, things start to become really unpredictable.

If you want to use a subwoofer, why not build separate stereo subwoofers, crossed over below 80Hz, and place them in the positions that result in optimal for bass reproduction in your room?

[joe carrow]

Quoting from Zaph's writup of his project,

"Strict requirements if you want this system to sound good: Countersink all drivers, scallop the rear of the woofer opening for airflow with a 1/2" chamfer bit and round over the top and sides with a minimum of a 1/2" roundover bit. A 3/4" roundover bit is even better if your router can handle it. The driver locations are important, and the cabinet width must be 7.0". Varying from any of these design elements will make this system be less than the reference standard design it is meant to be."

(emphasis mine)

Your idea of a pair of NS10 to augment the Z5 seems like a sound one, but unfortunately the cabinet design seems to need some work. It's not just diffraction, but also baffle step. As I understand, diffraction is the re-radiation of sound at edges of the cabinet, and baffle step is the transition from half space (at high frequency) to full space. This is dictated by the width of the baffle.

You're really adding a bass bin. One thing I would recommend before moving forward with this project- if you haven't already read it, read the blog entry detailing the transmission line version. I firmly believe that transmission lines can improve midrange and midbass clarity.

Feel free to use the subwoofer directly under the ZD5- just don't change the cabinet width or driver locations.

[Eton]

You have to redesign the x-over for sure.

First, If you will be using delay network it has to be added to midrange also because the lower the x-over point ( between mid and sub) the greater the phase shift.
Assuming your top box has the same internal dimensions, leaving the delay network between mid and tweeter will further make things worst between the mid and subs.
Even with the right software as in (soundeasy) the delay network + X- over is very sensitive to values and basically, at best you will be in the ball park. But it will need to be optimized or the results will be worse than not having a delay network.