Tc Sounds To The Rescue!

Is he comparing Nousaine's measurements based on the B10 vs. the eD12A?
I haven't given much thought about what the SPL/THD/Vd tells us yet...

As to the original person's question, I think either of the drivers he mentioned
are good long-throw subs that would match or exceed his expectations of getting
loud, and having really good SQ.

From what I understand, if all the specs we see are to be trusted, and linear output
of the drivers is determined by the BL/Kms curve flatness.... then both the eD and
Adire drivers are very flat. The eD driver has a purported parabolic BL curve,
while the XBL has a very flat curve, until it reaches its limits and cuts off quite
sharply. But it's been said we can't hear the distortion difference until the
BL is ~71% of the max - so technically by the numbers, we won't hear the
difference until excursion reaches that limit on both drivers.


edit: Just to add to that - I've heard the XBL comparison in their full range
driver and neither speaker was driven to anywhere near their excursion limits
and the difference was like night and day - the XBL was better by FAR. So what
does that mean about the BL curves and their shapes? Is 71% too conservative
of a measure to base the distortion audibility limit?

 

Bear in mind also that BL illinearities, and therefore distortions, comprise almost 80% of all audible distortion .

 

But the B12's DUMAX shows slight ripples in the BL curve.... I don't know if it's just
representative of the particular driver they measured, but wouldn't that be more
audible than a slow parabolic rolloff in the curve?

 

If you pay attention to how slight those variances are, I think it is apparent that the illinearities should not be audible. Seriously, they are about 1/2 NA per dip at the greatest point. With an measured linear BL averaging over 10NA, 1/2 NA dips are less than 5%. Far below audible thresholds at the subwoofer frequency range.

 

Check out the most recent AudioXpress magazine. In in, there's an article on the Hageman subwoofer design. The author designs - and builds - a sub around the Audiomobile MASS 2010 (TC Sounds' top end SQ design, with copper sleeving in the top plate and inside the magnet, and an underhung design to provide as much linearity as possible).

The author also drops a Brahma 10 in the same box (that was designed for the 2010), and measured the THD at 91 dB SPL for each driver. What he found was that down low - 40 Hz and down - the Brahma had up to 3.5 times LESS distortion than the 2010. Proof that it works, independent of either build house.

Also check out the measurements of the Sadhara subwoofer in Home Theater magazine. Ground plane measurements of THD versus SPL versus frequency. The Sadhara - with a single 12" driver with an XBL^2 motor - not only had 3-10 times LESS distortion down deep than any other unit measured in the test, it has THD at 100 dB SPL equal to or lower to the SVS B4+ (which uses 4 long throw TC Sounds 12" drivers, and was measured by Dr. John Johnson).

In comparative measurement after measurement, THD is found to be considerably lower with the XBL^2 motor versus a standard parabolic curve. This isn't just "Brahma/Adire" versus everyone - the research of Dr. Earl Geddes, Dr. Wolfgang Klippel, Dr. Floyd Toole, Mr. David Clark, and on and on confirm it. Flatter BL means lower THD, period.

If flat BL was such a non-issue, then why is TC Sounds trying to create it with their variable winding voice coil? Seems the build house even implicitly admits that a flat BL is superior...

Dan Wiggins
Adire Audio

 

dan, i was talking to kyle, and i kinda came up with the notion that i do not believe the graph that tc sounds published...but the other thing i was thinking, was that there's not any good way to make suspension stiffness flat enough to match the 'flat' Bl, but wouldnt that mean that the motor had the ability to put full motor strength into the suspension limits.

for the normal person, who drivers their speakers to the very limits, i would think that it would be slamming the suspension limits will full motor force?

sorry if these thoughts are not clear, im trying to multitask. any comments are appreciated.

eric

 

Nismo...
That's what makes excursion-considering measurement technology (like DUMAX or Klippel) cool!

It measures not only BL curves, and how flat they are, and what excursions BL starts to drop off..
But it also measures suspension Kms curves, how flat they are, and what excursions the suspension starts to stiffen up... and how quickly. B)

It's a design factor...
If you have a motor that's flat to 30mm in either direction, you wouldn't couple it to a suspension that was only flat to 15mm in either direction.
And there are other considerations... such as the basket, where it places the spider relative to the cone, where it places the spider landing relative to the top plate, and how much throw that affords.
If you compare the standard 4-leg Venezuelan or 12-spoke baskets to something like JL's W7 basket, or the Eclipse Ti basket, it's easy to see that the W7 (or Ti) affords the cone way more excursion capability.
You've got to match them up based on what you are shooting for.

 

its good to see that eventhough I have not bought a woofer in 2 years that the brahma or its design is still what every woofer designer wants to create wether they admit it or no :robot: t....

 

my only point is, from how it appears to me (the uber guru of speakers :stupid: ) its just gonna make it easier for stupid people (ie the average user) to destroy them. you know the whole "build a better mousetrap..." thing, right?

im asking because im still trying to learn all this stuff

eric :bye:

 

I think it'll make it harder for people to destroy them, actually...
(If we are talking about the same thing)

The farther out you push the limits, the fewer people will reach them. That's a good thing... because even if "stupid people" (your words, not mine! ) run their amps full-clip and can't distinguish distortion from music.. they still need that much MORE power to actually reach them... and with the limits farther out there, probably need a botched enclosure, also.

Picture a basketball court in the NBA.
Imagine if the basketball hoop was set to only 9' as a standard height.
EVERYONE would be dunking, without hardly jumping even.
With the hoop set to 10' tall, still lots of these big guys dunk, but they have to have the right opportunity.
If the hoop was set to 11' tall, fewer guys would be dunking.
If the hoop was set to 12' tall, even for the big NBA guys, it would really be something to dunk the ball...
If the hoop were 13', you'd almost never see a dunk.
If the hoop were 14'....
You get my point. B)

 

dis what happen when you got trapped gas!

:blowup:

 

just be on the lookout for something new and different from TC sounds in the near future :baby:

 

Cools.... I can't wait to see what they're up to next!

 

Hey Marshall .

What's up cutie :huh: .

Fellas, Marshall is a Bro, treat him with the utmost respect...





















NOT!!!
Dude, what are you doin'? Good to see you stopin at my home turf. I hope we can expect to see you around more often B)

 

B) wutup homie ....

you got some cool smilies here...i like..haha...

i'll stop in often...i saw this place about 3 or 4 weeks ago..didn't know it had been open so long....

anybody goin to vegas?

 

Something I've asked a million times but never gets answered is at what level (volume)/level of excursion, does one have to have their sub playing to "hear" the effects of BL illinearities? I know that a driver with more linear displacement has less distortion at any given level of output. I also know that the effects of BL illinearities can be heard at extreme output levels...but, at what point do they audibly begin? I don't care much if distortion becomes audible when my driver hits 25 mm one way because I (and most people) rarely, if ever, listen to music at these output levels. Now if BL illinearities are detectable to the human ear at, say, 5 mm of excursion, then maybe you guys have a point. Otherwise, it's just distortion that takes a $500,000 dumax machine to detect.

:ss: