Low level body/weight presence wanted: Can 12" full range deliver?

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#281
Hi VanJerry, congrats on your decision. Let us know how it all turns out. Just catching up here but earlier you had mentioned:

VanJerry said:
...What you get with a coherent, or phase-aligned sound is sonic clarity and a preservation of the source's harmonics. This gives you a keen sense of realism.
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I think if you reverse-engineer that, you'll find that it is just everyone's habit of circular audio-speak: coherent = clarity = realism = no phase shifting = harmonics = coherent again.

In physics, correct me if I'm wrong but doesn't "coherent" just mean that two or more signals of the same frequency are in a constant phase relative to each other, so you can predict how they interfere with each other? Or something like that? I can't think how that would relate to any property of an individual driver.

For example, how would we measure the "coherence factor"? Play a saxophone and see if the harmonics are in phase with the fundamental or something? And then we find, oh dear, the harmonics are arriving earlier or later than the fundamental? I honestly don't know.

Ultimately, the people I know who value "coherence" and "clarity" are the folks who stripped their systems down to the bare bones: two watts, two drivers, some wood and an input signal. That's what I did, though I don' t recommend it to others necessarily, because one person's minimalism is another person's masochism.

I certainly could be wrong about all this of course.
 
#283
Hi rjbond3rd,

I know that sounds off but actually, larger drivers like these can experience internal incoherence. Warping etc

Originally posted by Planet10
But you have to consider the driver's coherance as well. Despite being a single driver, a FR can have internal coherence issues -- in particular any FR with a whizzer is really 2 drivers with a mechanical XO.
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As well, there's Doppler caused phase modulation as the HF ride on the LF movements.


Jerry
 
#284
Glad you asked udailey,

There's 2 TL's on the menu.

GM's and Scottmoose's. But only the 2.8 BR you're using is proven.


I believe Scottmoose's is a 3.28 cu.ft. straight line TL:


Scottmoose said:
40in x 13.5in x 10.5in (HxWxD). Zdriver 16.375in. Zvent 37.5in. Vent 3in diameter x 6in long. Stuff cabinet & vent 0.5lbs ft^3 of hollow-fibre damping. Gives a quasi aperiodic damped vent alignment.
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And GM's is a 1.8 cu.ft. tapered TL:


GM said:
If we were to 'morph' (so to speak) Scott's semi-aperiodic stuffed vent BR into a reverse tapered 1/4 WL pipe (AKA TQP, TWQP, TQWT) and further accept a theoretically inaudible amount of ripple in the FR to keep the stuffing density to ~1 lb/ft^3 max (though historically folks tend to use < simmed), then we can reduce it to a ~1.8733 ft^3 adjustable floor loaded tower to help fine tune it in-room both to it and the sub system:

L = 47.75"
So = 100"^2 (the wider the baffle, the better to lower the baffle step)
SL = 50"^2 (open bottom terminus)
zdriver = 6"

You could of course work out a smaller version of Scott's damped BR based on the max stuffing density to get similar results, I just prefer to simplify wherever practical. Plus, there's just something about the perceived 'slam' of a big vent (even stuffed) that's a sizeable percentage of Sd Vs a small one.........

Since the roll off slope between F3, Fb (p) defines a TL's, BR's Qtp, the steeper it is the higher it is just like a sealed alignment's Qtc, but the XO will alter it (usually for the worst), ergo the price you pay in impulse response when shrinking cabs so much, though combined with the Rythmik's feedback control and the TL's well damped ~flat BW it will in theory seen compression horn 'fast' if you can dial it in 'close enough'.

AFA folding, you normally place the driver somewhere around seated ear height and choose a width/depth ratio, then fold it up as required. Note that if you use a 1.0:1.4142 bend width:depth ratio, then the divider board(s) winds up equidistant from all three walls in the bend. For other ratios you'll either need to scale it out as I do or use a CAD system to calc it.
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The tapered line approach offers the smallest possible enclosure and is very good at taming the unwanted upper harmonics. I believe it's supposed to have slightly less output than the straight line.

Both sizes are OK though of course smaller is WAV better.

And slightly more output is not going to make much difference - the 12 is probably louder than I'll ever need so I can afford to keep it down a bit.

So, the main difference I'm aware of is that Scott's will go a fair bit lower.

I'm not sure if GM's will go a tad lower if it were twice as big but aside from that I'm open to anyone who might see how to choose between these.


My sub has a variable slope between 12 dB and 24 dB. So I would prefer something with 12dB I would think. And with the AN 12 I'm not worried about authority and extension, however I do want to optimize impulse/transient quality and possibly lessen driver flex if that's possible.


-Jerry
 
#286
VanJerry said:
...larger drivers like these can experience internal incoherence. Warping etc... As well, there's Doppler caused phase modulation as the HF ride on the LF movements.
Click to expand...

I don't doubt there are many "microscopic" phenomena at work, as the cone can't be in all places simultaneously -- it has to move to get where it needs to be, and that takes time and maybe that does cause the cone to go "out of shape" -- presumably that's why the cone is flexible.

But how would one measure the effects of these (seemingly esoteric) distortions? Would we notice if they went away? I'm not doubting them, I'm just curious if this is worth pursuing (via driver tweaks?) Obviously it's not worth treating something that won't have an audible benefit.
 
#287
GM said:


Greets!

Right, though again my brace/'foot' went all the way to the top to 'kill three birds with one stone' (I hate to do any more woodworking than absolutely necessary).

Well, we've relieved it of the majority of the high excursion BW, so don't need much acoustic efficiency, especially with such a low mass corner (2*Fs/Qts = ~149.3 Hz which will be lower in use), i.e. the cab's BW is < an octave wide.

That said, until the cab is at least as big as its Vas, bigger is better (BIB) rules for the most part, so in a side by side comparison the larger one will in theory sound slightly more 'full'/'relaxed', though impulse response actually degrades a bit due to the cab not controlling the driver quite as much (weaker air spring) and why I gave you the smallest practical version for a ~80 Hz XO point. Personally, the former outweighs the latter until it becomes audibly under-damped, but as always YMMV.

Anyway, doubling the two areas at the same length makes whatever the smaller one's width, depth dims 1.4142x larger = ~4.066 ft^3.

GM
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Awfully sorry there GM,

I'm afraid I pulled another sleepless night trying to get this show on the road.

Can you help me in my stupor on which is former outweighing which latter?


And there's another advantage here I missed: this relieves the majority of the high excursion BW which is vital to Doppler and probably internal coherence.


Jerry
 
#288
rjbond3rd said:


I don't doubt there are many "microscopic" phenomena at work, as the cone can't be in all places simultaneously -- it has to move to get where it needs to be, and that takes time and maybe that does cause the cone to go "out of shape" -- presumably that's why the cone is flexible.

But how would one measure the effects of these (seemingly esoteric) distortions? Would we notice if they went away? I'm not doubting them, I'm just curious if this is worth pursuing (via driver tweaks?) Obviously it's not worth treating something that won't have an audible benefit.
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Hi rjbond3rd,

The designer must utilize cone materials which will not flex nor distort during heavy bass and long excursions. I have found aluminum or magnesium as the ideal woofer diaphragm, as both are thin and non-resonant metals....Paper, soft plastic, and Kevlar woofers have “soft” cones that will add up to 34% distortion caused by cone flexing, which generates “warped” sound waves. It is easy to measure the Young’s Modulus, which is the ratio of rigidity to weight, and thin metals measure (and sound) best. Note that midrange and tweeters DO NOT SOUND GOOD when made of metal, so this is not a “blanket” recommendation.

- Albert Von Schweikert
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I can't find the rest of my notes but imagine the output of that interacting with the whizzer output.

I'm sure Dave can describe it a little more fully than the bit of his statement I quoted earlier.
 
#290
VanJerry said:

Can you help me in my stupor on which is former outweighing which latter?

And there's another advantage here I missed: this relieves the majority of the high excursion BW which is vital to Doppler and probably internal coherence.


Jerry
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Until the cab is audibly too big sounding ('bloated', i.e. under-damped), I prefer bigger since it yields a more relaxed, 'live' sound, but the difference will be subtle and most obvious with singers like Julie London, at least to me.

Even the Babb Lorelei didn't suffer from any perceived Doppler effects, so no way the AN12 would even if tuned to Fs in a huge cab due to the mechanical XO to its whizzer to decouple it from the highs, though it does relieve it of most of its amplitude modulation distortion (AMD) which is sometimes misconstrued as frequency modulation distortion (AKA intermodulation distortion (FMD, IMD)) due to Doppler effects.

AMD is what 'muddies' up a wide BW driver due to diaphragm bending waves not being uniform in its TL BW, screwing up the harmonic structure. Even high zoot FR drivers aren't immune, a high resolution impedance plot shows Lowthers to have many low amplitude impedance spikes to show where there's a phase shift, but because they are low amplitude we don't mind.

GM
 
#292
rjbond3rd said:
Hi VanJerry, well on the bright side, at 34% distortion, the proverbial glass is still about 2/3rds full. Good luck on your build!
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Thank you for your good wishes, rjbond3rd. 🙂

On the extent of any distortion. If what Uriah is enjoying is at 34% it'd go to show it's just a number compared to listening...

But. Uh - No. Suspecting, by all accounts that this kind of worst case distortion was hardly the case with the AN is exactly why I asked udailey about intelligibility and about realism. Because Dave of Planet10 was kind enough to be concerned about something close to this very thing on my behalf I think I crunched enough research to come up with an effective and fairly practical question to evaluate the issue.

I know Uriah is but one AN 12 owner's response - but as a doctor would put it - he represents a legitimate "universe of 1."

Uriah takes obvious great pains not to be overreaching in his opinions so whatever large cone "stuff" is present I expect it'd be well short of a problem to me. (And that's not to put pressure on Uriah - I took a few other parallel routes to investigate this and other issues, including grilling David at Commonsense with emails.)

That's not to say that with his years of hearing some of the best mids and highs available to us that if Planet10 were listening to Uriah's Super 12 he would be as forgiving. But, on the other hand - according to Uriah, Dave might be surprised. And I happen to place stock that the choice of the Cast 12 would go a long way towards further relieving Dave of at least some of his concerns.

So I'd like to take this opportunity to assure everyone that I haven't glossed over anything. That wouldn't be fair to the AN Cast 12. - On the contrary, I am choosing it because it is not only the closest choice for my peculiar single driver (HT) needs as I see them, but that actually, in choosing the AN 12 most of the expected downsides of going large cone single driver simply don't appear to be there to a degree that would concern me. I feel pretty secure.

In short, I think I'm well past 3/4 full and the drops aren't slowing down.



-Jerry
 
#295
AFAIK, aperiodic just means without period. The only way to genuinely achieve it is with a horn, but you can get ~close enough with a max-flat impedance aligned cab, which was & is the primary object of the heavily stuffed, so called 'classic', non-resonant TL. However, the term has also been appropriated to refer to a flattened out, underdamped box alignment, where you use a resistive vent to lower the Q at Fb.
 
#296
quote:

Note that midrange and tweeters DO NOT SOUND GOOD when made of metal, so this is not a “blanket” recommendation.

- Albert Von Schweikert

There's probably up to a billion+ folks around the world that would disagree with him as stated since alum. domes have been the high SQ material of choice for cinema mids/HF horn systems since their inception, not to mention some high SQ dome tweeters along the way, so I take exception to his 'blanket' statement.

GM
 
#300
GM said:
quote:
"Note that midrange and tweeters DO NOT SOUND GOOD when made of metal, so this is not a “blanket” recommendation. "- Albert Von Schweikert

There's probably up to a billion+ folks around the world that would disagree with him as stated since alum. domes have been the high SQ material of choice for cinema mids/HF horn systems since their inception, not to mention some high SQ dome tweeters along the way, so I take exception to his 'blanket' statement.

GM
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...Dang, I knew I should have cut that part out rather than allow it to be thrown for you to catch - I was trying to grab something to explain what Dave of Planet10 would have been vastly better equipped to do.
 
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