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

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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.

An externally hosted image should be here but it was not working when we last tested it.



An externally hosted image should be here but it was not working when we last tested it.



An externally hosted image should be here but it was not working when we last tested it.
 
<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?
 
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?
 
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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?
 
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.
 
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.
 
In my experience with largish diameter roundovers, the effective baffle width is the flat face plus one roundover radius. That is, the measured baffle step of my 10.5" wide boxes with 1.25" roundovers matched almost perfectly "The Edge" modeled response of a baffle 9.25" wide. (get The Edge" free at www.tolvan.com)

I haven't tested boxes with 45 degree chamfers, but I'd suspect that they are also effectively a bit wider than the flat face of the baffle. As mentioned, this will probably make the ZD-5 baffle step start a bit high, causing a bump in the response.

You could use a db or two of shelving high pass or low Q notch filter in the active XO to take some or all of the early baffle step and then a shelving low pass to put it back in at the right spot. You might not need the second part, depending on where you cross to the NS10s.

It looks like you could take the NS10s up to 2-300 Hz which would let you boost their level to take care of baffle step and allow higher output from the top end. Or put one section of the low pass at the bottom of the baffle step and the other(s) at the intended XO frequency.

As far as phase correction goes, IMHO you don't need to adjust the top end. The mid and tweeter relationship will be unaffected by the active crossover. You will need to adjust the phase of the ZD5 portion relative to the woofers for optimum performance.

Another option would be to taper the top of the bass bins to mate with the 7" wider baffle of the ZD5. I don't think it would be as visually appealing as what you've drawn, though.
 
"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."

I'm familiar with this area of the article. I attempted to make the transition of the ZD5 cabinet to the bass bin as asthetic as possible while changing the important cabinet dimensions as little as possible. I understand that the BSC and defraction aspects of the crossover design now no longer exactly match the cabinet that it used. I looked at it as a trade-off and my justification was this (really, think about it). How much of a difference will this make in the audible sound of the speaker? I think the answer is "not much". The cabinet dimensions are close so the corrections can't be completely off. I know without a fair amount of softare calculations it's not possible to know what the exact measured response will look like, but you have a fair amount of that whenever you build speakers because everyone puts them in different rooms! I don't know about you guys, but I haven't spent a lot of time or money treating my listening room (also known as "the den"). Anyway, I percieved that it wouldn't make a huge impact on the overall sound, maybe I'm very wrong here.

You will need to adjust the phase of the ZD5 portion relative to the woofers for optimum performance.

Agreed. I realized that going into this. The active crossover I have from Behringer has a "delay' setting. I've never used it and I'm not sure if this is even what I'm looking for. The response of the subwoofer portion of this speaker really needs equalization as well because it drops off (modeled, anechoic) about 17dB@20Hz. I'm guessing this to be about 7dB in room. Also, obviously equalizing room modes would be nice. I was hoping for some interesting suggestions regarding this aspect, the only thing I could come up with way "use a PCXO" or "use a DCX2496", but I covered the reasons why I think those are a bad idea in the original post.


This idea has taken a lot of flack so far, some of it I feel is a little exagerated or in some cases just wrong, but I APPRECIATE IT. This is exactly what I wanted when I made this post. Please keep posting your opinions, even if the are negative about my idea, even if I continue to openly disagree with them.
 
Delay and phase correction are almost the same thing. The idea is to avoid as much as possible any sharp discontinuities in the system phase curve.

If you don't mind a bit of soldering, you could go with an analog active crossover. With a little help from www.linkwitzlab.com it's not too difficult to get it right, assuming that you have appropriate measurement gear. SL will help there, too. Linkwitz has boards available, and I will be running another group buy of active filter boards soon, as demand is still strong.
 
BobEllis said:

It looks like you could take the NS10s up to 2-300 Hz which would let you boost their level to take care of baffle step and allow higher output from the top end. Or put one section of the low pass at the bottom of the baffle step and the other(s) at the intended XO frequency.


I think that's the best way to go. Afterall, do you plan on highpassing the woofer of the ZD5? If so you are going to have to redesign the XO and go 3way. I don't know why you wouldn't, considering your using a sub. If you can get that sub crossed high enough you won't need as much BSC and that means free sensitivity. And a damn fine mid not having to pull bass duty and muck up the sound.

I know you want to keep it simple and basically tack on sub to the ZD5 but that BS is probably gonna be alot more noticeable then you think. If you want to go that route I'd make a separate sub and stick it in the corner. It all comes down to the fact that your spending some big money on very nice drivers, don't you want the best sound out of them? If you don't think you'll notice the difference then why not use cheaper drivers?

Btw it's a cool idea. I like it. We just want to see you do it right. And don't let some here get to you.
 
So, let me see if I have all this. A list of problems follows:

Problem 1: Changing the ZD5 cabinets will change their baffle step.
Solution 1a: Change the passive filter to accomodate this, but it would require calculation and then probably trial and error.
Solution 1b: I could raise the crossover frequency and avoid this problem all together, but would that also mean REMOVING the BSC portion of the ZD5 crossover? Wouldn't this cause entirely new problems?

If I can simply raise the crossover frequency (Bob?) I would definitely choose 1b.


Problem 2: The lower portion of the cabinet will not be in phase with the top portion.
Solution 2: I can use the "delay" setting on my Behringer active crossover or build an active crossver that has phase correction built in.

How audible of a problem is this exactly? I would definitely attempt to correct it with the delay setting if that would work.



Is this an accurate list of problems? Are there more? Will the solutions proposed work? Comments welcome, thanks again.
 
It won't be as simple as raising the crossover frequency. based on his baffle width, Zaph is probably applying baffle step compensation starting around 750 Hz, with 6 db of boost by 375. This is built into the XO, there isn't one component to take out to eliminate it.

If you built a zaph size box to sit on top of a woofer box you could then cross over as high as 375 Hz without worrying about baffle step. With your proposed enclosure, the baffle step will start too high and will cause an audible anomaly in frequency response unless you correct it.

What you could do to use your enclosure design is counter the rise just as you would if using a driver with a rise in response. Since you know (approximately 6 db rise from 750-375 hz) what the deviation is, you apply a shelving high pass filter that will reduce the drive to the mid at the same rate as the built in baffle step increases it. Then you apply the appropriate BSC ahead of the mid-woofer crossover (because it will overlap the crossover, both drivers need it. If you cannot do it this way with a behringer, both should get the baffle step in their chains).

The idea in raising the crossover frequency is to reduce the excursion demands on the midrange. The less it has to move the cleaner it will be.

for 2 either solution proposed will work.

Audibility depends on you and the crossover frequency. With higher frequency crossovers phase differences tend to be more audible. Is it worth correcting? definitely. It costs you nothing but time with a Behringer so why leave that last bit of improvement on the table? The key will be accurate measurement, as it will be with baffle step correction.
 
m0tion said:


The LR4 active crossover I planned on using would be 24dB/oct slopes as a low pass for the subwoofer portion and a high-pass for the ZD5 portion, but I wouldn't be altering the crossover of the woofer in the ZD5 specifically. I'm kind of confused by what you are asking.


I meant highpassing in the context of making a new 3way XO and making the ZD5 woofer the mid. I didn't realize the Behr would be running the ZD5 and sub. I thought it was just for the sub.

Your idea would work well enough if you weren't changing the baffle. Have you considered just building a couple standalone subs and using the Behr to cross the ZD5 with sub at 60-80 Hz? I know it's not as impressive as the cabinets you want to build, but it'd be a hell of alot easier to do. But you won't gain any sensitivity, if this is important to you.

Otherwise try Bob's idea with the shelving high pass. If you could make some measurements in the baffle of your design you could find out exactly where the BF is starting and it's magnitude and use the shelving HP accordingly. Could work OK.
 
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

if you run digital with the behringer, noise level is probably lower than you hear yourself breathing :)


I'd go with an active crossover in your case just for the ease of it. The cost of the component parts for the crossover could be use toward the dcx2496.
 
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