Emspeaker LB12: 12 inch full range , 98db, 16 ohm, qts:0.2
no xover, no tweeter ( good for 15khz, enough:yes)
www.emspeaker.fr/
You can use it in an bass reflex and get to 40hz (+-3db).
or open-baffle ( that is what I have )+ sub.
Hihg spl with very good transient; very involving sound.
no xover, no tweeter ( good for 15khz, enough:yes)
www.emspeaker.fr/
You can use it in an bass reflex and get to 40hz (+-3db).
or open-baffle ( that is what I have )+ sub.
Hihg spl with very good transient; very involving sound.
planet10 said:
I'm sorry Dave, lowering the Q of too small a box? I'm not following. My current understanding of aperiodic is that it's an option I'd want to use if I want to have a speaker Q (Qtc) as you say, closer to 0.6 - which would be great - but I'd like to reduce the normally resultant Vb = 447 liters.
And I did originally want to use it except I thought I couldn't. Can you please confirm or refute the following:
While there'd be no problem using aperiodic with smaller full range drivers like the FR125 that however large cone full rangers need a certain critical back pressure lost going from sealed to aperiodic for the cone to successfully output high frequencies. That is, the AN 12 would not qualify for aperiodic. I'm referring to this I posted earlier in #69 of this thread quoting ScottG:
By the way, on the topic of transients, from this post of yours a few years ago, would these be the viable alternatives to sealed I was asking about? TL's and Voigt pipes?
Scottmoose said:
Ahh!
This has great appeal Scottmoose. But if you are surprised it is a measure of my newbiehood for I did find it a very interesting solution earlier in my research but dropped it thinking it wouldn't gibe with the single driver experience. Now I wonder if I didn't look into it deeply enough...
I really could use your correction if there is something I have misunderstood, but these are the 2 reasons that I didn't pursue the idea:
1. What draws me, and what I understand about the full range single driver experience at the moment (and I probably should use language like this more often) - you know, avoiding the effect of crossovers, the preference for emanations from but one driver in space... Well, I was concerned how much or whether the introduction of cross-overs (?) and a second physical driver even if only present to 500, or even 400 or 300 would disrupt the point of it all for me.
I've been made aware of the rationale that a crossover isn't so much a bad thing - doesn't effect the directness or liveness of the presentation - as long as it is out of the ear's zone of critical hearing for such things. And of course I was already prepared to make one exception by my use of a subwoofer albeit crossed out of the way much lower. But I simply don't know how pure to the original ethos I must remain for this first project which was about single full range drivers. I could use subjective guidance. Really, I serve no abstractionist ideal - only the sensual.
2. Of the research I've done I was impressed - whether naively or not - there was something unique - whatever it's shortcomings - to the large full range driver experience in particular. And it happened that some of these characteristics fit my rudimentary understanding of how I could achieve a sense of effortless weight and presence and low level detail - both in music and HT. And at both low volumes and otherwise.
However... if it does not impact the soul of the full range single driver experience what you say does offer what seems like a strong and exciting solution for things like enclosure size, low level weight and the ability to serve certain aspects of HT. And it opens a world of design options, including of course, driver selection.
Such as your suggestion of the 15" and 8". That would be something! I would think it would solve the issue of effortless weight at low volumes and provide appropriate tactile presence for HT.
Tell me, Scottmoose, I assume you mean sealing the low Q 15"? Because I can see them both being sealed too...
The approach even allows the possibility of a compromise with my current course - a kind of enclosed version (because I do not have the distance from back walls for OB) of Bvan's very interesting post about his Hawthorne Duo mentioned in post #24 only using the AN Cast 10" perhaps sealed, with a sealed 12" or 15" woofer.
What do you think?
Making it aperiodic lowers the Q , but stuffing can lower the Q even more, and it has the benefit of reducing the impedence peak at resonance more than aperiodic.
Aperiodic has a way of sucking the snap/life out of bass transients, at least IME. OVER-stuffing a sealed box can do this too.
Read Vance Dickasons Loudspeaker Design Cookbook, and check out the chapter on stuffing sealed cabinets. It is quite impressive what can be done with fibreglass or foam. They are far and away the best stuffing materials for a sealed cabinet (that he tested).
Stuffing a cabinet can reduce the impedence peak at resonance by more than half ! ! This makes the amp's job easier , as it has a more linear load to drive, and helps tighten up the bass by allowing the amp to load more power into the driver at resonance, which helps control the resonance.
Stuffing a cabinet can reduce the Qtc by .3 (or more) ! ! !
So your 101 Litre .88 Qtc could be as low as .58 Qtc when stuffed . With differing amounts/densities of stuffing, you can tune the cabinet for a target Q.
Sealed cab's can be tuned. This isn't done with a port as in a BR, but with cabinet volume and stuffing materials. The Qtc , frequency of resonance , and rolloff can all be manipulated.
A stuffed cabinet behaves differently than a non-stuffed, with regards to rolloff and frequency of resonance.
A Sealed cabinet with Q of .7 will have a lower F3 than a Sealed/Stuffed cabinet with a Q of .7 , but the Sealed/Stuffed cabinet will be smaller, have the benefit of reduced impedence peak at resonance , and reduction of cabinet resonance.
I highly recomend the Loudspeaker Design Cookbook. It's quite informative.
.....................................Blake
Aperiodic has a way of sucking the snap/life out of bass transients, at least IME. OVER-stuffing a sealed box can do this too.
Read Vance Dickasons Loudspeaker Design Cookbook, and check out the chapter on stuffing sealed cabinets. It is quite impressive what can be done with fibreglass or foam. They are far and away the best stuffing materials for a sealed cabinet (that he tested).
Stuffing a cabinet can reduce the impedence peak at resonance by more than half ! ! This makes the amp's job easier , as it has a more linear load to drive, and helps tighten up the bass by allowing the amp to load more power into the driver at resonance, which helps control the resonance.
Stuffing a cabinet can reduce the Qtc by .3 (or more) ! ! !
So your 101 Litre .88 Qtc could be as low as .58 Qtc when stuffed . With differing amounts/densities of stuffing, you can tune the cabinet for a target Q.
Sealed cab's can be tuned. This isn't done with a port as in a BR, but with cabinet volume and stuffing materials. The Qtc , frequency of resonance , and rolloff can all be manipulated.
A stuffed cabinet behaves differently than a non-stuffed, with regards to rolloff and frequency of resonance.
A Sealed cabinet with Q of .7 will have a lower F3 than a Sealed/Stuffed cabinet with a Q of .7 , but the Sealed/Stuffed cabinet will be smaller, have the benefit of reduced impedence peak at resonance , and reduction of cabinet resonance.
I highly recomend the Loudspeaker Design Cookbook. It's quite informative.
.....................................Blake
Nihilist said:
Something fishy going on there. How are you (and Dickason) defining an aperiodic box?
A properly designed aperiodic box already has incorporated as much stuffing as possible without sucking the life out of the music. So there is no way stuffing alone can produce a better result.
Further, one of the things that defines an aperiodic box is that the resonance peak is decreased (ie aperiodic = without period = without resonance peak)
As well a properly done aperiodic enclosure will decrease the 1st derivative of the impedance curve over a sealed box.
In theory stuffing can give an apparent increase in box size of up to30%, in practise 20% is a more reasonable figure.
without context that is a completely meaningless statement. To figure out what stuffing can do, model your sealed box and then increase box volume by 20%.
with stuffing his 101 litre box could be considered 121 litres and the Q will be 0.8<Q<0.88.
Those are all related. The roll-off in the end is 2nd order. How quick it gets there and with how much ripple is defined by the Q. Adding stuffing adjusts the apparent volume.
That is a very suspect statement.
dave
As you seem to favour the idea of a large 12in driver, here's one way of using the AN 12in CF in a smaller (these things being relative) box.
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. The vent would need some form of grill at either end to keep the damping material in place. Basically, this is what those Seas vents are; just larger & tuned for a specific box / driver. Just cross to a pair of subs to support the LF.
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. The vent would need some form of grill at either end to keep the damping material in place. Basically, this is what those Seas vents are; just larger & tuned for a specific box / driver. Just cross to a pair of subs to support the LF.
Attachments
Scottmoose said:
ScanSpeak (used to be DynaAudio) actually. Putting one of those in a box and calling the box aperiodic is like taking your box, cutting a 3" hole in it and calling it a bass reflex. They probably do a disservice to real aperiodic boxes everywhere.
An externally hosted image should be here but it was not working when we last tested it.
dave
Thanks for the correction. 
I knew it began with 'S'... ;^)
Yeah, I'm not quite sure how that's supposed to work. As you say, it's a bit like offering a single plastic tube of fixed diameter & length & saying 'there you go: a bass reflex vent. For all cabinets.'
Well, I suppose it is. In the same way that one could place a pea shooter beside a 13.5in naval gun & say that it too, is a device that fires a projectile.
You know what I think's happened? All the workers from British Leyland in the mid 1970s (I use the word 'workers' in the broadest possible terms here as they spent most of their time on strike or drinking tea, & only very occasionally gluing cheap bits of plastic & even cheaper pieces of metal together & then sticking improbable names on them. Like the attached 'Princess.' Mmmm. Nice.), when they got fed up, moved to Scandinavia & have passed their slightly 'relaxed' approach over to the resident driver manufacturers. You know the kind of thing: 'There, that'll do, that's alright; it's better than my house' (insert Birmingham accent here).
That last is not entirely true, or serious. But tragically, large parts are.
I knew it began with 'S'... ;^)Yeah, I'm not quite sure how that's supposed to work. As you say, it's a bit like offering a single plastic tube of fixed diameter & length & saying 'there you go: a bass reflex vent. For all cabinets.'
Well, I suppose it is. In the same way that one could place a pea shooter beside a 13.5in naval gun & say that it too, is a device that fires a projectile.
You know what I think's happened? All the workers from British Leyland in the mid 1970s (I use the word 'workers' in the broadest possible terms here as they spent most of their time on strike or drinking tea, & only very occasionally gluing cheap bits of plastic & even cheaper pieces of metal together & then sticking improbable names on them. Like the attached 'Princess.' Mmmm. Nice.), when they got fed up, moved to Scandinavia & have passed their slightly 'relaxed' approach over to the resident driver manufacturers. You know the kind of thing: 'There, that'll do, that's alright; it's better than my house' (insert Birmingham accent here).
That last is not entirely true, or serious. But tragically, large parts are.
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Wrong. I'm talking about those pathetic excuses for aperiodic vents, which they appear to be claiming are universally applicable & for which they should therefore hang their heads in shame. If that's their slipshot approach to vents, it doesn't bode well for future drivers. Not that I like their existing ones much anyway come to that.
The approach used in the Loudspeaker Design Cookbook was as Dynaudio recommended , and using Dynaudio Vents.
Approximately 50% fill was used, leaving the area between the driver and the vent free of damping matertial , and positioning the vent on the back wall of the enclosure at the opposite end from the woofer.
Perhaps with 100% fill it would have fared better ?
As it stands , it fared pretty well, but not as good as the 100% fibreglass or foam filled testboxes (regardless of fill density used).
While it may be a more generic approach than you would like, there is instruction for using multiple vents for cabinets/drivers of larger sizes. It's not just "stick one of these in your cabinet and it's aperiodic" .
RE; Sealed boxes
"A properly designed aperiodic box already has incorporated as much stuffing as possible without sucking the life out of the music. So there is no way stuffing alone can produce a better result."
Ahh, but a sealed stuffed enclosure has no vent, therefore it has more linear airspring/internal box pressure. Couldn't this be advantageous ?
According to the Cookbook's (Dickason's) seemingly well controlled testing, the rolloff changed with regards to stuffing used. It is not a textbook 12db per octave. You can see this just with a change of Qtc.
Also, perhaps due to differing air spring/volume , the Fc and F3 are measurably different comparing a sealed or sealed/stuffed cabinet.
Also, according to his testing, the Q can be lowered much more by stuffing than if you were to add the theoretical 20-30% more box volume. As I said, this resulted in a different (higher) Fc and F3 than if you had increased box volume, but if you weren't looking for extension , but more for articulation, then it would seem to be the way to go.
With 100% fill of fibreglass at a density of 2lbs/cu.ft. Z goes from empty box : 38.96 ohms to 15.8 ohms.
Resonance shifts from 84.54hz to 79.37hz and Qtc goes from 1.22 to .88
Combinations of stuffing of 4lb/1lb (50/50)density yielded even further results, with Z going to 14.67 , Fc going to 75.86 and Qtc going down to.75.
Surprised you don't have that book, it seems to be a pretty common read amongst diyers , although noone I've talked to seems to have paid much attention to his findings.
Edited for grammar/content
....................................Blake
Approximately 50% fill was used, leaving the area between the driver and the vent free of damping matertial , and positioning the vent on the back wall of the enclosure at the opposite end from the woofer.
Perhaps with 100% fill it would have fared better ?
As it stands , it fared pretty well, but not as good as the 100% fibreglass or foam filled testboxes (regardless of fill density used).
While it may be a more generic approach than you would like, there is instruction for using multiple vents for cabinets/drivers of larger sizes. It's not just "stick one of these in your cabinet and it's aperiodic" .
RE; Sealed boxes
"A properly designed aperiodic box already has incorporated as much stuffing as possible without sucking the life out of the music. So there is no way stuffing alone can produce a better result."
Ahh, but a sealed stuffed enclosure has no vent, therefore it has more linear airspring/internal box pressure. Couldn't this be advantageous ?
According to the Cookbook's (Dickason's) seemingly well controlled testing, the rolloff changed with regards to stuffing used. It is not a textbook 12db per octave. You can see this just with a change of Qtc.
Also, perhaps due to differing air spring/volume , the Fc and F3 are measurably different comparing a sealed or sealed/stuffed cabinet.
Also, according to his testing, the Q can be lowered much more by stuffing than if you were to add the theoretical 20-30% more box volume. As I said, this resulted in a different (higher) Fc and F3 than if you had increased box volume, but if you weren't looking for extension , but more for articulation, then it would seem to be the way to go.
With 100% fill of fibreglass at a density of 2lbs/cu.ft. Z goes from empty box : 38.96 ohms to 15.8 ohms.
Resonance shifts from 84.54hz to 79.37hz and Qtc goes from 1.22 to .88
Combinations of stuffing of 4lb/1lb (50/50)density yielded even further results, with Z going to 14.67 , Fc going to 75.86 and Qtc going down to.75.
Surprised you don't have that book, it seems to be a pretty common read amongst diyers , although noone I've talked to seems to have paid much attention to his findings.
Edited for grammar/content
....................................Blake
Scott, -- I wasn't picking at you....
I've always been under the impression that Seas, Scanspeak and Skaaning were concidered good quality, if not among the very best ( still not counting 4-digit price tags, if that's even a quality mark).
BTW - the "vents" were solely a Dynaudio fix from the early / mid 80s, when Seas and Scanspeak were still one company. They departed in the late 80s, I think, and Skaaning left SS sometime around 2000 to form his own company.
FWIW - I never got around to try those vents, -- as Dynaudio marketed them as a major "fix all" problems, in terms of impulse response.........
I've always been under the impression that Seas, Scanspeak and Skaaning were concidered good quality, if not among the very best ( still not counting 4-digit price tags, if that's even a quality mark).
BTW - the "vents" were solely a Dynaudio fix from the early / mid 80s, when Seas and Scanspeak were still one company. They departed in the late 80s, I think, and Skaaning left SS sometime around 2000 to form his own company.
FWIW - I never got around to try those vents, -- as Dynaudio marketed them as a major "fix all" problems, in terms of impulse response.........
Nihilist said:
Semantics really; it doesn't alter the fact that it's generic & therefore far from optimal, except probably in a couple of coincidental cases where it happens to be spot on to requirements of volume & driver.
"For enclosure volumes up to 1.75 cu. ft., one vent is required. Up to 2.75 cu. ft., two are needed, and for volumes of more than 2.75 cu. ft., three vents are required"
That's a bit like, oh, Audi saying 'Right. The A4 weighs 1 ton, the A6 1.5 tons & the A8 2 tons so we'll stick them on 15in, 16in & 17in wheels respectively. That'll do.' (Mind you, I'm convinced that's exactly what Audi did do since the death of the Quattro & the introduction of the last model RS6 which marked the point when they suddenly remembered what handling is about).
Dickason's book is on my shelf. It's over-rated IMO. A decent book, but no more than that. The TL section for e.g. is rubbish.
Over-stuffing a box to compensate for insufficient Vb is dangerous as you're increasingly likely to suck the life / dynamic / transient response out of it in the process, even if the numbers / graph looks nice. Same goes for TLs (as in TLs, not resonant QW lines) as it happens. Better to go for a larger box with lighter damping than over-damp a smaller cab. IMHO of course.
AuroraB said:Scott, -- I wasn't picking at you....
I know mate -taken in the spirit it was intended. My sardonic humour occasionally gets the better of me, as I dare say you've noticed.
Generally IMHO they are very fine quality, within their own particular remit. Unfortunately, what they emphasise has never really been to my taste (despite being Norweigian by direct ancestry [both my parents]). YMMV as always of course. They remind me of a VW Golf. Superb engineering, but devoid of passion.
Mmm. IIRC, I remember them first coming out, or an early version at least. Like you, I regard anything marketed as a panacea, or at least as universally applicable, with a jaundiced eye. Would that life were so simple.
FWIW, it was Goodmans who first marketed something on these lines, during the 1960s. However, they were intended for a specific range of drivers & cabinets, which at least gave a trifle more direction. Rumour has it, they worked rather well in those conditions; whether anyone tried it with anything else of course, I wouldn't like to say. What's the betting someone tried it with Wharfdales at some point? Although they had their own rather unusual take on such things too.
Nihilist said:
I've found that any damping right behind the driver -- and certainly as one gets anywhere near those densities ....
Scottmoose said:
The context of the "q drops by 0.3" is right where i'd expect it -- a box that is far too small to start with.
No. I prefer the driver to be mechanically well damped...
I've owned the 1st & 3rd Editions and have the 5th edition on the shelf. A good basic primer, a bit shallow and certainly not without its biases.
dave
AuroraB said:
And now with ScanSpeak/Vifa/Peerless sucked up by corporate america and significant production moved to China, that leaves SEAS... at least they seem to be getting a bit more adventuresome... be nice to see a recreation of the 2" cone tweeter that was most often seen with the Peerless name on it.
dave
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