New Dealer again

[Bwcad1]

holy mother of long post that i wont ever read!

[Jonathan]

"I don't see what you are referring to, truthfully.

Take a look at it's DUMAX measurements:
http://www.adireaudio.com/Files/DUMAX/BrahmaDumax.pdf
The nice thing about DUMAX (and Klippel) is that they measure the sub... not so much dynamically (as Klippel can), but across excursion, and in both directions.

If you look at the KMS curve (suspension stiffness), you'll see that the suspension has a very linear suspension, right out virtually as far as the sub's linear excursion capabilities - and very nearly to the sub's mechanical Xmech limits - where it then stiffens dramatically."

Problem is that a Klippel analyzer and DUMAX cannot take true dynamic nature of a driver into account, it can't tell you anything about bumps, rubs, buzzes, lead slap, etc. The KMS is good, but not symmetrical. Neither is the BL curve. It's hard to get this one right, but still not ideal either way.

"And the cone assembly is very rigid paper - which has basically the best stiffness to mass ratios, as well as the greatest self-damping characteristics."

Paper is far from the best stiffness to mass ratio. Aluminum, magnesium, titanium, and numerous different fiber based offerings like carbon fiber, fiberglass, kevlar, etc. surpass it. Paper itself is stiffer than polyprophelyne and APX cones, but not a lot more. But you have to consider proprietary composites will be all over the place anyway, not really fair to generalize. I would like to know how you can justify the benefits of low mass when your 12" sub cone has an mmd of 224g . Especially saying subs like an ID-Max are about 80g lighter than that and have nearly 100 sq-cm more cone area. W7 is also substantially better in that regard. For that reason, Brahmas are hellaciously inefficient and you run into resonances a long time before other offerings would. Hence, it sounds like crap above 60hz.

"Based on what you are describing however, all these things are what should lead you TO a design like the Brahma, and AWAY from an overhung architecture."

W7 is flatter in BL than a Brahma and has a more linear suspension, especially in the 12W7 and 13W7 variants. Even the 10W7 puts up a flatter BL up to its limits (which admittedly aren't as high as a Brahma, but the 10W7 isn't the flagship of the W7 line either). Adires site clearly shows that as well (wonder why they picked the 10W7 to compare to, hmm... ) The Brahma has dips in BL right past dead center all the way up to around 15mm of excursion. I don't know about you, but I listen at that point a whole lot more than at x-max.

Really I don't see your point here, you can't generalize overhung any more than you can XBL^2. Both of them can be good or suck, just depends on the engineer. The W7 and Brahma sound very similar to one another, but I prefer the W7s performance overall. Just a better engineered subwoofer overall, much more attention to every critical detail and in build quality.


"..what you are describing are the traditional downsides of a LGLC overhung subwoofer.
And XBL^2 (and DDD as well!) have coil lengths that are smaller - significantly smaller. Granted, not so small that we're in underhung territory, but small enough to be comparable to subs having at least a full order of magnitude lower excursion - and those subs still wouldn't have the distortion reduction of a flat BL curve - those subs would in many ways suffer MORE from intermodulation distortion, because the intermodulation of BL would come on sooner."

I wasn't comparing motor topologies, I was comparing long coil vs short coil designs, whatever topology they may be. Like I said before I listed all these things, motor topologies have helped combat a lot of the negative side effects of high output subs. They just haven't removed them completely.

"Sounds to me like you just need to take a step back from the IDmax's and W7's on the market."

I'll take a W7 over a Brahma any day of the week. ID Max, too, especially for a ported or AP application. ID Max is what I'm currently running because it's very flexible, efficient, and doesn't sound like ass above 60 hz And yes, I've dealt with all of them in many different applications.

[geolemon]

Problem is that a Klippel analyzer and DUMAX cannot take true dynamic nature of a driver into account, it can't tell you anything about bumps, rubs, buzzes, lead slap, etc. The KMS is good, but not symmetrical. Neither is the BL curve. It's hard to get this one right, but still not ideal either way.

Not to get ahead of a quote later down - but the W7 is hardly symmetrical. It actually shows a significantly different BL curve shape in the rearward direction than in the forward direction.
I'll give you that it's a well-executed overhung design - but really the suspension is what makes that subwoofer remarkable.
And at it's price point, unfortunately not very high on the value scale.

I've always been a long-time JL supporter, believe me - these aren't brand criticisms (I've run JL XR's in my Civic for the past 4 years, had JL 10W6's for 10 years in there, up until last year in fact, and my business partner has JL slash amps and a 10W7 that he at one point in time had in JL's own "HO" stock enclosure). Manville Smith gave me the royal treatment at JL's booth at CES two years ago - a 20 minute demo in the greatest SQ vehicle I've ever heard - their mini, running 5.1.

Adire HAD the 12W7 DUMAX results up there as well - I didnt' scan their site much, but I'd bet they are still on there. If not, I have them somewhere around here...

Paper is far from the best stiffness to mass ratio. Aluminum, magnesium, titanium, and numerous different fiber based offerings like carbon fiber, fiberglass, kevlar, etc. surpass it.

Best stiffness to mass ratio having the greatest inherent damping characteristics.
There's a reason it's the most popular. The other cones you mention ring like bells, and even carbon fiber doesn't offer the damping characteristics, although better than metal.

It WAS things like cone resonances you were complaining about, I thought?

I would like to know how you can justify the benefits of low mass when your 12" sub cone has an mmd of 224g ]
I wouldn't justify the benefits of low mass - mass is a tool that you can use to control Fs, as a designer.
The only downside to mass is efficiency really (if low Fs is one of your goals).
(and the W7 is no wonder of efficiency itself - the long coil-to-gap ratio really I'm sure are what primarily contribute to this - only a fraction of the energized coils are actually working in the magnetic field at a time
It doesn't affect transient response or accuracy - the things that you were complaining about... hence why I posted.

I was commenting on the benefit of things like inductance... which DOES increase transient response. XBL^2 allows you to use a smaller, lower inductance coil, to acheive the same excursion capabilities.

Especially saying subs like an ID-Max are about 80g lighter than that and have nearly 100 sq-cm more cone area.

Lighter - what's the benefit? Higher efficiency? What else? (not transient response )

Also, ID's claims of "more cone area" are nearly fully bogus.
In reality, you have to take about 1/2 the surround area into account when calculating Sd, because anything that is moving is going to stimulate the air into sound - it's moving right along with the cone.
It isn't as if the "cone stops HERE, and there's no sound coming off the suspension next door!"
The entire suspension moves, it's just that there's more displacement on the inside of the surround (since it's reaching higher excursion levels) compared to the outside of the surround (since it's reaching lower excursion levels). Factoring in 1/2 the surround as cone area is the most common way to generalize it in.

Bottom line is - the IDmax uses a narrow suspension, so it has more CONE area - and then a very skinny surround. Factor that in, it works out to no net gain in actual displacing cone area. It's marketing.

I didn't realize you owned an IDmax - we used that as one of our benchmark subs a while back.
And we observed a SHOCKING amount of suspension distortion at high excursion levels with that sub, and it's "tall" surround.
I can now understand some of these generalizations you are making about "high excursion subs", considering your point of reference!

It's decently clean, it's high-throw, it's as loud as two IDQ's of the same size... it's not even that bad a value, but I definitely agree with your observations - I wasn't ever terribly impressed with it, for what that's worth.

W7 is also substantially better in that regard. For that reason, Brahmas are hellaciously inefficient and you run into resonances a long time before other offerings would. Hence, it sounds like crap above 60hz.

I've got a ton of experiences with those, and XXX's (at least when they shared cone units - I haven't played with the dish-cone ones - that's my 10" XXX on this page: http://www.betteraudio.com/geolemon/DLC ), and I've never heard these resonances. Worst I've seen was some lead slapping - and that was (for professional reasons) because I tracked one down from someone who was complaining about their 1st gen Brahma doing that, and got my hands on it so I could see what was going on.
That was an anomoly, a defect, not inherent in the product.

W7 is flatter in BL than a Brahma and has a more linear suspension, especially in the 12W7 and 13W7 variants. Even the 10W7 puts up a flatter BL up to its limits (which admittedly aren't as high as a Brahma, but the 10W7 isn't the flagship of the W7 line either). Adires site clearly shows that as well (wonder why they picked the 10W7 to compare to, hmm... ) The Brahma has dips in BL right past dead center all the way up to around 15mm of excursion. I don't know about you, but I listen at that point a whole lot more than at x-max.

W7 is definitely not flatter than the Brahma, in any size.
Even with it's "XBL^2-like-trick" with the pole drilling, it's as flat as a typical underhung driver - but not like the Brahma. At the far, far extremes of it's excursion, it rolls off gentler, but not where the sub is linear.
As I said before - really, it's the suspension on the W7 that is remarkable - and that's really more a shame than a value... to have a suspension capable of SO much linear throw - and then have a motor attached to it that, while well engineered, limits the sub to about 28mm of linear throw- that suspension and basket could probably handle DOUBLE that. :happy055:

...but, unlike XBL^2 (not to sound like a broken record ), overhung motors AREN'T scalable, if an increase in Xmax limit is desired, it gets increasingly difficult.

Really I don't see your point here, you can't generalize overhung any more than you can XBL^2. Both of them can be good or suck, just depends on the engineer. The W7 and Brahma sound very similar to one another, but I prefer the W7s performance overall. Just a better engineered subwoofer overall, much more attention to every critical detail and in build quality.

I'll give you a superior build quality - it's the Mercedes of the subwoofer world. The flagship product that everyone has their targets set on.
But the Brahma outperforms it in many ways - overall clarity, accuracy mainly. The difference is even audible.

Like I said before - many people don't prefer the sound, because they are used to distortions being present - it's always existed. Subs have always been overhung (and even the few underhung drivers - they were so because of the SQ improvement - in part because of their flatter BL ), even 'trained ears' were trained on THAT architecture. It didn't get any better than that, because it couldn't... SQ drivers traded excursion for clarity in the form of shorter, lower inductance coils, and efficiency for clarity in the form of copper caps and shorting rings. That was the old "reference standard"

It's simply less impressive, per dB level, the first time you hear the sound without those additional distortions present... less violent.

I wasn't comparing motor topologies, I was comparing long coil vs short coil designs, whatever topology they may be. Like I said before I listed all these things, motor topologies have helped combat a lot of the negative side effects of high output subs. They just haven't removed them completely.

Technology helps improve everything!
I remember when I bought my trio of 10W6's when THEY first came out (12 years ago now?)... I owned "the" flagship sub on the market, back in the day.
Small box capabilities - that was new! Ultra High excursion - we're talking a whopping 13 or 14mm here! And a suspension that could well out-stroke the linear Xmax... a lot like the W7 can today.

I'll take a W7 over a Brahma any day of the week. ID Max, too, especially for a ported or AP application. ID Max is what I'm currently running because it's very flexible, efficient, and doesn't sound like ass above 60 hz And yes, I've dealt with all of them in many different applications.

I'd never criticize someone for their personal preference.
In many ways, I'd pick a W7 over a Brahma myself, particularly if cost was not a factor in the decision.
My main point was that I felt it odd that the things you were boasting about - the "weaknesses of high-excursion subs" - are really in many ways advantages (operating in a more linear manner, regardless of your excursion level, for one).
And the other weaknesses you were mentioning - transient response, inductance - are issues that are addressed with subs like the Brahma... or more fundamentally, addressed because of the XBL^2 topology.
And that it was odd that you'd be blaming a thick, heavy paper cone for either transient response issues (mass isn't a factor), or for resonances (it's one of the best choices for it's self damping characteristics).
It just didn't seem to jive with reality, actual application, in those ways... not that there aren't exceptions that could (can't they always? ) be cited.

That's really all - just read these last few lines here - I could have saved myself a lot of typing..

[Jonathan]

"I didn't realize you owned an IDmax - we used that as one of our benchmark subs a while back.
And we observed a SHOCKING amount of suspension distortion at high excursion levels with that sub, and it's "tall" surround.
I can now understand some of these generalizations you are making about "high excursion subs", considering your point of reference!"

Plus the mechanical noise from the surround dimpling. Which is why I said I'd prefer it ported, or AP if I weren't concerned about volume level I got it mainly for a SQ aspect at low levels, in which a Brahma won't give me any advantages at the levels I listen at. Had I intended to blast a sub 125+db most of the time, I'd choose a Brahma, Dub7, or others. But well designed ported enclosures tend to negate the benefits of all that x-max, at least if you aren't intending to do SPL competition.

"It's decently clean, it's high-throw, it's as loud as two IDQ's of the same size... it's not even that bad a value, but I definitely agree with your observations - I wasn't ever terribly impressed with it, for what that's worth."

Keep in mind my post was more a general overview than the specifics of these subs. ID Max isn't going to impress on DUMAX testing. Low volume SQ, though, it does a good job.

Really, though, lets say you set up your system power to allow a Brahma to reach full x-max at 20hz. This can hit 140s in the right application, but we'll say 135 because we know a Brahma is capable of this. Let's take it down to 123db, 12db down, which is still pretty loud, the excursion is going to reduce by around 8x (sticking to theory). So 3.5mm at 20hz, 1/4 that at 40hz, and so forth. Not a lot of excursion, and many overhungs can match it at that level. Remember we're talking SQ here :) Not that XBL^2 isn't incredible in it's ability to keep a flat BL, but you have to consider your application and whether you really need it.

XBL^2 has inherent advantages that surpass many motor topologies overall. For SQ reasons I'd really prefer a good underhung design, but it would be insanely expensive if it were built like any of these subwoofers. I'm not really downing XBL^2 a bit, but the examples using that topology (Brahma, Extremis midwoofer, XXX, etc.) IMO don't realize the capabilities of this motor as well as they potentially could.

"Like I said before - many people don't prefer the sound, because they are used to distortions being present - it's always existed. Subs have always been overhung (and even the few underhung drivers - they were so because of the SQ improvement - in part because of their flatter BL ), even 'trained ears' were trained on THAT architecture."

I know the sound, it's drier, more mellow. At least at ear ripping levels it is, which I'm really not all that worried about. We all heard it with the underhung topology anyway, underhung is flattest of all, just not cost effective since it doesn't integrate flux efficiently. Main benefit to XBL^2 is that it can be implemented for low cost compared to more exotic designs like the W7 architecture, underhung, and JBLs DDD technology.

"Adire HAD the 12W7 DUMAX results up there as well - I didnt' scan their site much, but I'd bet they are still on there. If not, I have them somewhere around here..."

The 10W7 is on there, not 12W7. And on the dumax, it's still a flatter BL curve than a Brahma. I doubt Adire did the favor of smoothing it for them. The most impressive shown on there IMO is the Audiomobile MASS 12. Benefits of an underhung design, tends to have flatter BL than all of them.

"Best stiffness to mass ratio having the greatest inherent damping characteristics.
There's a reason it's the most popular. The other cones you mention ring like bells, and even carbon fiber doesn't offer the damping characteristics, although better than metal."

True when you take damping into account. I guess if you were really concerned, you could do the magnesium number and make a notch filter for the sub :)

"Lighter - what's the benefit? Higher efficiency? What else? (not transient response )

Also, ID's claims of "more cone area" are nearly fully bogus."

No, not transient response. Any heavier cone is going to experience resonances before a lighter competitor, and it doesn't give you a lot of flexibility in design. Really, though, while the cone isn't the only contributor to SPL, I was putting it there because regardless of the added area, it's still considerably lighter than the cone of a Brahma. Mmd doesn't take the surround into account .

"And that it was odd that you'd be blaming a thick, heavy paper cone for either transient response issues (mass isn't a factor), or for resonances (it's one of the best choices for it's self damping characteristics)."

Not blaming it for transient response, only resonance. Regardless of self damping, you still can't eliminate a resonance. For transparency and clarity, I'd prefer a metal cone assuming it were designed to have a single peak and would be controllable by a notch filter (SEAS Excels, Lotus offerings). While it isn't completely inaudible, at least you don't experience numerous resonances throughout audible range like you would with a paper, poly, or other cone. Of course this isn't the best idea for a subwoofer, but you get my point :) Plus, I think the DUMAX and Klippel fans wouldn't care to see the waterfall plot of a subwoofer. Non-linear distortion tends to dominate SQ at low levels more so than linear distortion.

[Bwcad1]

thats it! lol your both out of your damn mind!

[Jonathan]

You SPL guys have it easy

[William from NOLA]

You SPL guys have it easy

Yea really! Just one frequency to worry about! lol

[geolemon]

Really, though, lets say you set up your system power to allow a Brahma to reach full x-max at 20hz. This can hit 140s in the right application, but we'll say 135 because we know a Brahma is capable of this. Let's take it down to 123db, 12db down, which is still pretty loud, the excursion is going to reduce by around 8x (sticking to theory). So 3.5mm at 20hz, 1/4 that at 40hz, and so forth. Not a lot of excursion, and many overhungs can match it at that level. Remember we're talking SQ here :) Not that XBL^2 isn't incredible in it's ability to keep a flat BL, but you have to consider your application and whether you really need it.

Flat BL is going to help you out in SQ, at any excursion level. Elimination of intermodulation distortion - because there is no modulation of BL!
And none at 20mm means none at 15mm... at 10mm... at 5mm. ]XBL^2 has inherent advantages that surpass many motor topologies overall. For SQ reasons I'd really prefer a good underhung design, but it would be insanely expensive if it were built like any of these subwoofers.

Not so much expensive - well, it would be - but I think there are other physical limitations that are even more prohibitive:
Underhung subs by nature are big, heavy beasts.
They require a massively thick top plate - because the excursion is dictated basically by the distance between where the voice coil windings end (when held "at rest" at the center of the gap) and where they would reach the end of that top plate when in motion.

To increase excursion, you must increase top plate thickness - and pole piece length - and since the top plate and T-yoke are the heaviest components on the sub, you are increasing the mass of the sub dramatically.
You could use a machined top plate, so that it increased in height only inside the sub (TC sounds has done this for years), but then you have to start worrying about another issue...

...the flow of magnetic flux.
It's bad enough having a tremendously thick top plate, because the magnetic flux available will dissipate across that increased gap width, resulting in a weaker magnetic field as measured at any single point in that gap... and it's difficult to increase the magnetic energy to compensate for it... stacking magnets only increases magnetic energy around 10% per each you add - you need to increase the surface area of the magnet, meaning larger diameter (read: heavier, and more expensive) magnets, as well as larger diameter top plate and back plate... and you can only go as large as the cutout for the sub, ultimatelly... ruh, roh...

Not to mention, with a machined top plate, you have to worry about creating "elbows", or joints where magnetic flux is artificially constrained. The pole piece / backplate joint is always an issue on almost every sub - the most flux-flow resistive element in the circuit. With the machined top plate, you can create the same sort of situation - and less flux isn't the goal!

underhung is flattest of all, just not cost effective since it doesn't integrate flux efficiently. Main benefit to XBL^2 is that it can be implemented for low cost compared to more exotic designs like the W7 architecture, underhung, and JBLs DDD technology.

It's not the flattest. Dual gap technologies are... and since XBL^2 is scalable beyond dual-gap in theory, theoretically XBL^2 would be the flattest.

Yes, underhung has a gentler BL curve shape than overhung, but it's not perfectly flat - where XBL^2 and DDD truly are. W7 gets close, thanks to it's XBL^2-esque pole-piece cross drilling - slightly changing the density of flux in that area of the motor, a mild version of what XBL^2 does more effectively - inherently.

Since we're speaking in generalizations, look at the conceptual comparison at the top of this tech paper on XBL^2:
http://www.adireaudio.com/Files/XBL2TechPaper.pdf
You see in the comparison, that all subs have been "normalized" to all "be 15mm Xmax subs", to be fair.
You see that out to about 10mm in either direction, that the underhung design is the closest match to the XBL^2 architecture in terms of BL linearity, but once that short coil even gets near either edge of the magnetic gap, since the magnetic field becomes increasingly weaker, BL does roll off - just like with an overhung sub, even LGLC overhung designs like the W7.

The 10W7 is on there, not 12W7. And on the dumax, it's still a flatter BL curve than a Brahma. I doubt Adire did the favor of smoothing it for them. The most impressive shown on there IMO is the Audiomobile MASS 12. Benefits of an underhung design, tends to have flatter BL than all of them.

It used to be, I have it somewhere, unfortunately not on hand at the moment... I'll have to remember to look for it when I can.
The 10W7 isn't flatter - you can even see with the 10W7 that the BL curve has a different shape on the in-stroke, compared to the out-stroke. And the ripples in the 10W7's BL curve are every bit as prominent as the Brahma - and look, we're taking about a fraction of 1 BL value here... totally ignorable in either case (you had mentioned it previously as a concern).

Also take into account the differences in the scale of both the X-axis (excursion) and Y-axis (BL). This somewhat magnifies the ripples that you see, compared to the more compressed W7 plot.

Ultimately, you are talking about two subs with a flat BL and the same excursion level... the Brahma is simply more symmetrical in stroke, with it's more direct implementation. The W7 uses a similar approach - not technically two gaps, but setting up the magnetic flux in the same way by cross-drilling the pole vent... different technology? Not really.

No, not transient response. Any heavier cone is going to experience resonances before a lighter competitor, and it doesn't give you a lot of flexibility in design. A heavier cone would tend to experience resonances later than a lighter competitor, because it will inherently have greater damping properties - pushing those resonances down to a lower frequency, as well.

Not much different than sheetmetal on a car - thin sheetmetal rings, buzzes when tapped or rubbed.
Then, you cover that sheetmetal with heavy Dynamat.
Now, it no longer rings and buzzes.
A heavy cone isn't much different.

[Bwcad1]

yea us spl guys have it easy!!! mmm hmmm!

[Jonathan]

"It's not the flattest. Dual gap technologies are... and since XBL^2 is scalable beyond dual-gap in theory, theoretically XBL^2 would be the flattest. "

I've never ever seen a dead flat XBL^2 motored anything. Not theory, I mean in a true speaker application, such as comparing the Brahma with the Audiomobile MASS 12 (underhung) I was referring to above. Brahma has a longer stroke, but BL isn't as flat or symmetrical until you get close to 15mm each way or so. Depends on your definition of flat, though, whether at the absolute limits or right past center. I'd prefer the latter with my intended use, but I'm not a bass junkie.

"Flat BL is going to help you out in SQ, at any excursion level. Elimination of intermodulation distortion - because there is no modulation of BL!
And none at 20mm means none at 15mm... at 10mm... at 5mm. "

Not arguing that, but there are other topologies that give a flat BL to a certain point. Namely underhung.

"Yes, underhung has a gentler BL curve shape than overhung, but it's not perfectly flat - where XBL^2 and DDD truly are."

Show me a perfectly flat XBL^2 or DDD driver and I'll take a picture of myself in a tutu and post it as my avatar. It doesn't exist.

"You see that out to about 10mm in either direction, that the underhung design is the closest match to the XBL^2 architecture in terms of BL linearity, but once that short coil even gets near either edge of the magnetic gap, since the magnetic field becomes increasingly weaker, BL does roll off - just like with an overhung sub, even LGLC overhung designs like the W7."

W7 is a completely different beast from a typical LGLC design. Can't generalize them, as you can't generalize XBL^2. W7 stays flat to its limits then experiences the dramatic BL rolloff that XBL^2 does past its limits.

"The 10W7 isn't flatter - you can even see with the 10W7 that the BL curve has a different shape on the in-stroke, compared to the out-stroke."

As does a Brahma.

"A heavier cone would tend to experience resonances later than a lighter competitor, because it will inherently have greater damping properties - pushing those resonances down to a lower frequency, as well."

That's the problem.

BTW, I'm really enjoying this. Don't take it like I'm angrily arguing with you or anything, just sharing opinions