The last few nights while at work and bored out of my mind, I have spend modeling pretty much all of them but still keep going back to the AV15-X. I really like the look of the driver, and it models pretty well.
For Push-Pull I am aiming for a look like the box Moonfly did for Prize78 but for the 15's. I was shooting for a smaller box, 130L. From my untrained eye it looks ok when I model it. I am not too restricted by size but would like to keep it smallish. The box in the drawing below is 130L and is 22.5"Wx23.5"Dx34"H. It is 20.5" cube internally. I was using 1" thick wood, but would most likely use 3/4", so those dimensions would not hold true.
I haven't drawn anything for a dual opposed yet, probably tomorrow night or over the next few hours!
IMO, 130 litres is going to be a little small for a couple of X drivers, and you will lose some low end. When you model with these drivers, I would aim for a Qtc of around .65 for best results. The AE drivers have a very strong upper bass sound, so aiming a little lower with the Q will give a better low end response without any feeling of loosing upper bass.
If 130 litres is you maximum size, then you should consider the H drivers, as these work better in a smaller cabinet.
Thanks for the advise. The only issue I see with going bigger, 170L, is the excursion hits xmax at around 20hz using the 2000w watts a Ep4000 would put out. If I drop it down to 1500w It doesn't hit xmax till 6hz. At 170L the Q would be .648. Any issues with having it at 170L and using the EP4000 in bridged mode?
A few more questions if anyone wouldn't mind answering them...
-When modeling in general, is it best to put the power in at the "peak output" of the amp?
-What should I be looking for when viewing the xmax chart?
-At what distance below xmax is considered safe at a given frequency? Ex: 3-5mm @ 10hz, 3-5mm @ 20hz, 5-8mm @ 10hz, 5-8mm @20hz, etc...
I dont have access to the laptop with WinISD on right now, so I cant check the model. From memory, a 170 litre volume will have the drivers slightly exceeding xmax at full power at the lowest frequencies, but I need to run the model again to check the specifics.
I'll reply tomorrow as soon as I get back on my other computer and answer your questions in more detail.
well although with the full 2KW the model will exceed xmax at 18hz, at 10hz its only 2 mm over and still well within xmech. This basically means there wont be much of an issue with the driver bottoming out so you still dont need to worry about your driver. Under 20hz, its very hard to hear the distortion added in by exceeding xmax anyway so even if you do exceed xmax you likely wouldnt even know.
That said, the amount of power applied by your amp is entirely dependant on the source and how you use your system. For the majority of the time you wont use anything like the full power, and we have to remember the model is based on theoretical max input power, and displays theoretical max output/cone excursion etc. As such, a mm or 2 over xmax under 18hz, and only when the system is at its absolute full power, its pretty much a none issue. Remember, xmax and xmech are different things. Xmax is the limit of measured linear travel of the driver, xmech is the physical mechanical limit of driver travel possible before it hits its end stops and risks damaging itself. Ideally, your model wants to stay within xmax, but this is entirely relative to input power vs cabinet size, so your model is a design with variables you consider, its not a true representation of a definitive real world result.
Although a 170 litre cabinet shows the driver exceed xmax, its only with full power, so keep in mind that full power is something rarely required or used.
I never got my sub to bottom out and it was one of the cleanest subs Ive ever heard, so you dont need to worry about the slight bit of excursion over xmax in the model, in reality this will simply not happen, and even if it does you probably wont notice (a few seconds of explosion at sub 20hz frequencies where your ears dont actually hear the frequency) and there is no risk to the driver. The benefits of lower Qtc out weigh the slight xmax limit exceeding at frequencies you cant really hear it happening. You will end up with a deeper sounding sub, that produces cleaner sounding bass, and as you noted, you can get those lower frequencies with slightly less power.
Add to this that something like a Behringer EP4000 is unlikely to be able to deliver a full 2KW flat out, and I would surmise your sub will never see its driver exceed xmax anyway, unless of course, your just showing off FWIW, I used an EP4000 and modelled based on 1800 watts in 180 litres. Like I say I never had any issue with distortion or over excursion. As a final note, I wouldnt worry about anything below 10hz on the graph, hardly anything has material as low as 10hz, never mind below it, unless you start running sine waves.