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ZOD Audio M.A.U.L. Test Results and Discussion

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Alright time for the wrap up.

 

Here are the final HR inputs to simulate the system. Let me state right off that as usual the sensitivity measured is about 3dB higher than the HR sim. Been seeing this for years on virtually everything I've measured. That's another subject for another day. Note that this data is fudged a little to match the measured data. I'll explain where and why shortly.

 

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The data that is fudged a little is as follows

 

Le = Doubled to 0.9 from 0.45. Helps match the mid-band FR shape and roll off above 100Hz a bit better.

Ap = Vent area 730cm actual / Simmed at 612cm in order to match the measured vent resonance and tuning

Lpt = Length of port tube is 103.4cm actual, 122cm effective length for tuning(Loads against back wall on purpose) / Sim requires 101cm to match measured vent resonance and tuning.

 

System internal size is just under 880L or 31cuft

External volume at 47x47x30 is  1086L or 38.35cu ft

 

That all said here is how the normalized response shapes compare and the measured versus simulated impedance.

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Overall it is quite close in shape with the low corner and response notches and peaks all in approximately the correct places.

We see a sharp notch at 138Hz. This is the vent length resonance. The peaks at 146Hz and 200Hz and the notch at 183Hz are all related to the Horn dimensions, driver loading into it and driver placement. The one artifact that we do see on both the measured impedance and response that do not show up in the sims is a blip or notch at 112Hz. What could this be? internal dimension related cabinet resonance? Vent resonance? Panel vibration?

 

Remember the problems with the drivers being asymmetrically loaded into the horn path and how this caused issues with the performance that resulted in scrapping a number of designs? Let's have another look at that. In the following graph there are 4 traces. The black is the measured response of the real cab. Blue is the response in the HR simulation. We've already looked at these. The other 2 traces are each pair of drivers simulated by their respective loading into the system. The red trace on the graph is the set of driver loaded all of the way back into the beginning of the horn path. This is what we want and started out looking at when designing the cab. The green trace is the second set of drivers that load further along the horn path much closer to the mouth. Well looky there! There's a big ole notch right where we see the response blip in the real measurement (black trace). The response issue at 112Hz is related to a cancellation due to the placement of the second set of drivers in the horn path. Unfortunately HR cannot fully simulate things like this without breaking it into multiple simulations. I've also attached the sims used for the two sets of drivers below. In case anyone want to see for themselves in HR.

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Now that that is all out of the way here are a bunch of screens from the Solidworks assembly model so everyone can finally see what I've been running on about.

 

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I feel like I just read a Doctorate Dissertation on horn-loaded sub design. Thanks for sharing your thought processes, experimentation, and different options. Very cool to read. Thanks.

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Sorry it's a book. Next post will be tomorrow probably and that'll wrap it up with some pics and models.

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I thought it was long and informative, an overall enjoyable read. Thanks for taking the time to write it up. I enjoyed the learning journey you took us on and let us know you didn't just design final result from the beginning. So yes it's long but I'm personally glad for once to NOT get the Cliff Notes version. Thanks Josh!

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Ah ha! Was hoping you'd post more pictures but didn't expect you to post the innards much at all. Thought it was a secret. ;)

 

Well... I gotta say, it IS dense as fuck but not nearly as complicated of layout as I imagined. Definitely a complicated build with all sorts of bracing and such but... almost looks like something I could attempt where-as EVERY horn I've ever seen I'm like, "eh..eff that. I couldn't build that." This...maybe. But of course you had to put not one, not two, not three but FOUR g-damn'd RF T3's in there. Pretty much guaranteeing that nobody will ever have one of these. :P

 

I mean... all the tight-wad DIY'ers most of us are.

 

Ugh. :P

 

Awesome stuff, Josh. :)

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Yep. There's really not much to these types of cabs. It's basically a modified 6th order. Lot of people way over thinking it. Actually these types of cabs look nice with the vented section tuned higher to like 25 or 30Hz. No reason at all you'd have to use so many drivers or such expensive ones. In fact I'm already almost done designing a smaller one using two pro drivers tuned to that range. Looks like it should beat out a TH the same size.

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"Here are the final HR inputs to simulate the system. Let me state right off that as usual the sensitivity measured is about 3dB higher than the HR sim. Been seeing this for years on virtually everything I've measured. That's another subject for another day."

 

I thought a lot about this lately. The thing is we measure our speakers with RMS voltage but in fact the SPL is given by the diaphragm acceleration,which in turn is given by the instantaneous power so we should measure in fact with peak voltage instead IMHO. There we could get these numbers on sensitivity but then remains the problem of Max output and when I measure the excursion at the proper voltage, I get bigger numbers than xmax would suggest, so in reality the explanation stands only until you push things to the limit.

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Yep. There's really not much to these types of cabs. It's basically a modified 6th order. Lot of people way over thinking it. Actually these types of cabs look nice with the vented section tuned higher to like 25 or 30Hz. No reason at all you'd have to use so many drivers or such expensive ones. In fact I'm already almost done designing a smaller one using two pro drivers tuned to that range. Looks like it should beat out a TH the same size.

 

I might be one of the ones that is over-thinking it. ;)

 

Prototype 1 was a fail, but I didn't fail to learn. 

 

Same story as always for me though - when I have time, there is no money, when I have money, there is no time. So, I am buying drivers and materials when I have money, designs and builds will come once things slow down.

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Yep. There's really not much to these types of cabs. It's basically a modified 6th order. Lot of people way over thinking it. Actually these types of cabs look nice with the vented section tuned higher to like 25 or 30Hz. No reason at all you'd have to use so many drivers or such expensive ones. In fact I'm already almost done designing a smaller one using two pro drivers tuned to that range. Looks like it should beat out a TH the same size.

That could be really cool, hope it works out to your satisfaction.

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Amazing.

 

But....how long before your mind starts the "this shit is weak" refrain nagging at you to design something more capable (if there is such a thing)?  

 

JSS 

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Amazing.

 

But....how long before your mind starts the "this shit is weak" refrain nagging at you to design something more capable (if there is such a thing)?  

 

JSS 

 

This design has a solution for that.  The port is big enough for him to stick his head inside it.  Problem solved.Edi

 

Edit:  Oh wait, I thought it was just about more bass.  ;)  I bet that port does develop some crazy SPL.

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I can't be the only one amazed at how simple this is! I saw "Horn" on the description and tried to imagine the 4th dimensional hyperspace fold you worked out, and it's not much more than a bandpass. A bit anticlimatic  :lol:

 

Really showcases the brutal power of these RFs. Distortion is unreal. Great build quality and optimization for size and performance! I love it.

 

I also look forward to the extra 3dB of sensitivity thread! Looks like it's going to be another good one!

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I can't be the only one amazed at how simple this is! I saw "Horn" on the description and tried to imagine the 4th dimensional hyperspace fold you worked out, and it's not much more than a bandpass. A bit anticlimatic  :lol:

 

I also look forward to the extra 3dB of sensitivity thread! Looks like it's going to be another good one!

 

Haha it sort of is anticlimactic. Everyone assumed horn, or compound horn with a much bigger horn section and a much smaller vented one.

 

What I need is more sources of trusted sensitivity measurements for systems that can be simulated well for comparison. I know that the Danley bass systems have been said to have an extra 2 to 3dB of sensitivity that is unable to be accounted for in a simulation, similar to what I've been observing for years. Actually if you think about this, depending on how that extra couple of dB SPL is generated it may also account for the unrealistic displacement amounts required from some drivers to produce the SPL levels recorded.

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This design has a solution for that.  The port is big enough for him to stick his head inside it.  Problem solved.Edi

 

Edit:  Oh wait, I thought it was just about more bass.  ;)  I bet that port does develop some crazy SPL.

 

So what you're saying is I should start doing videos of these levitating things in the port, breaking floors and hair tricks with random girls?

 

 

Amazing.

 

But....how long before your mind starts the "this shit is weak" refrain nagging at you to design something more capable (if there is such a thing)?  

 

JSS 

 

I doubt that is going to happen in this case. The pair has the headroom of >4 GH's with a little deeper extension and better behavior overall. I've done only some very rough preliminary listening to one cab and it wasn't integrated at all. The fun part is coming up. I get to put them into position and start integrating them with the AE TD15M's. After that I can finally start listening/feeling? what they can do. One of my favorite things about it is I can hook up basically any amp to one and I don't have to worry about cooking drivers or bottoming things out ever.

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Likely, the most capable single sub at this point...

 

Josh, we (I) need to get the SPL/Liter graphs worked out (I'll add that feature into dbv2). How does this stack up against sealed cabs in that regard?
 

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You should get a second sp2-12k and wire each driver to its own channel.  :D  :D  :D  

 

So I should run both K20's on it and re-test? I may be able to break something then. Screw it I'll just get one of those PKN 3-Phase-40K's and give it the whole thing.

 

You know the sad thing...If I really did strap another K20 on one, It would gain 3dB of headroom at maximum. Hardly worth it. At some point you just run out of amp and it's not feasible to use more power. That's part of the reason for multiple super heavy duty drivers. Reduce any thermal or displacement related compression or conversion loss to minimal amounts thus making the most effective use of the available amplifier. Beyond that you have to start increasing the size of the enclosure to gain efficiency. On that note...

 

 

Josh, we (I) need to get the SPL/Liter graphs worked out (I'll add that feature into dbv2). How does this stack up against sealed cabs in that regard?

 

I haven't done the conversion on this guy yet but sealed subs pretty much rule this and specifically the passive (DIY) ones with the biggest displacement and powered with the big amplifier. It's a bit of an unfair comparison and I'm not sure how to level the field. I'm pretty sure I could get one of the most powerful 12" subs on the market and stuff it into a cab that will barely fit the motor and it will rule this. However the question becomes is that practical or valid? It might tell you that this is the most output dense system but if you have 8X the space available are you really going to use 8 of the same driver and 8 amplifiers? I think not. We definitely need to be able to separate the powered/closed loop systems from the passive/big amp stuff because of things like this. In fact I'm wondering about using this data only for active/closed loop systems. I'm open to ideas.

 

Now all I need is to get 2 M-Force modules to power the M.A.U.L.'s

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At the very least, we can have output density be a factor of system type or even just sealed vs all else.

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