Adire Tempest or SVS Ultra......?

[Manuel Delaflor]

ears

You need to know that the Tempest driver we are talking about is a 15 inch one.

Do the math.

[TheEAR]

15 inch driver! Oh I am impressed,not really.

How much air can it move,and remain linear(low THD).

TheEAR(s) Now theears

[Dustin B]

Damn Manuel for pointing me to this thread.

The Tempest has an Sd of 779cm^2. It has a linear p-p Xmax of 32.8mm. Which gives a linear Vd of 2.55L.

The Brahma 12" has an Sd 436cm^2 and a linear p-p Xmax of 54.6mm. Which gives a linear Vd of 2.38L.

Now even if the TV12 driver has an Sd of 475cm^2 it will take 53.8mm of p-p Xmax to match a Tempest. And with the surround required for that excursion I highly doubt the Sd of the TV12 is that high. So it will more than likely take in excess of 60mm p-p Xmax to start passing a Tempest Vd wise. Are you saying a TV12 being a smaller motor has enough Xmax to have more than 2.55L of Vd Tom (any 12" driver that can move that much air is freakn impressive though)? Is linear Vd not the biggest factor of SPL at a particular THD level down in the last octave (assuming a appropriately sized, properly tuned and sufficiently ported enclosure)?

The biggest problem Dan is having now with his new XBL^2 topology is finding a surround that will stay linear with the extreme linear excursion an XBL^2 motor is capable of. Dan has stated he could go out to >60mm one way Xmax with XBL^2 if he could find a surround that could do it. There have been serveral reports from shows where XBL^2 was demonstrated. Two drivers, one with, one without. The difference in the sound between the two was reported as very obvious.

In a month or two Adire will be releasing a new 15" driver with XBL^2 that will have over 5L of Vd and other specs much more appropriate for home use (unlike the Brahma series). Price on this driver will hopefully be in the $300USD range. Problem is it is impossible to port it properly in a suitable enclosure size, so you'll have to add another $200 for a pair of 18" PRs (barely enought) and another small chunk for a kilowatt of power to get it to it's limits.

I suggest you give this link a read theEARs, especially the pdf files linked to at the bottom of the page this link leads too.

http://www.adireaudio.com/tech_papers/xbl2_motors.htm

This message has been edited by Dustin B on 08-03-2002 at 02:10 AM

[TheEAR]

Thanks Dustin,this is interesting news.I will be looking forward to this new Adire driver.

Brahma drivers are no slouches but a driver with over 5L of displacement!

Serious subwoofing

Adire has a nice few sub amps on their site,the Hypex 500W(8 Ohms)job is quite impressive(the name is bogus...Hypex?!but the amp looks promising).

TheEAR(s) Now theears

[TVodhanel]

Predicting subwoofer performance based on Vd is like predicting a drag race outcome based only on engine displacement. All things being equal(which they never are)the larger engine will USUALLY win...but in hot rods--like subwoofers---there's quite a few subtle(and not so subtle) variables that will affect performance. Some people look at a 500 cu-in caddy engine on paper and think "my god, there is no way a little 327 cu-in vette could ever win that race..."

TV

[Dustin B]

You've made these car comparisons many times Tom. But cars and subs are different. I understand why a smaller engine in a vette could take a larger engine in a caddy. Weight, tires, suspension, turbos (gotta love the 1987 Honda F1 engine, over 1000hp from a 1.5L V6; twin 58psi turbos!!) etc.

Another good example would be the SCCA T1 class. Mustang vs NSX. The Mustang is heavier, has a lot more power, can accelerate faster and can go faster in a straight line than the NSX. But the NSX is lighter, can wait longer to brake into corners and can take those corners at a higher speed (plus Cunnigham is a kick *** driver). End result the NSX wins a lot of races.

I'd like to learn what these sublties in a sub are. Changing specs as you approach max excursion as described in the XBL^2 paper? Port compression (but the large enclosures a Tempest requires are easier to port addequitly)? Does the small distance between driver and base plate on the SVS subs do something neat? Something else my intermediate knowledge level hasn't even seen yet?

This message has been edited by Dustin B on 08-03-2002 at 11:25 AM

[TVodhanel]

>>>You've made these car comparisons many times Tom. But cars and subs are different. I understand why a smaller engine in a vette could take a larger engine in a caddy. Weight, tires, suspension, turbos...<<<

Exactly, And each of those factors you quoted regarding cars has an equal parallel in subwoofer performance.

>>>I'd like to learn what these sublties in a sub are<<<

Then you'll have to spend some time away from the keyboard and start building a couple subwoofers. You obviously have a PC, so you can DL some free RTA software,use your RS SPL meter, and measure each design under controlled conditions(I recommend ground planing at 2 meters). With a minimal investment (Around $400-500 for a couple good drivers and some wood and sonotubing,ect),a handheld jigsaw...all you will have to do is put in the effort needed to aquire the knowledge you seek.

Fives years ago(and a couple thousand hours worth of testing) I thought it was all about Vd too, once I measured a few dozen example of the superior *Vd* getting its *** kicked I began to realize the automotive displacement example is a perfect analogy ( I also have a blown,N2o Rat powered pro streeter in my garage,so I already knew a little about horsepower)

The first unit(20-39cs~ $379 passive) we sent Tom Nousaine(2 years ago) clocked in at 109.5dB/25hz extension. According to its *Vd* there is no way it should have performed to that level(to date...only the 18" Servos from Velodyne have matched that output and extension combination)

I get emails all the time froms guys that think bass is "cool",they have the latest shareware simulation software loaded and they saw me on the internet and want to know how I got started,blah,blah,blah...

It's all good until we get to the part were they will actually have to get off their ***,away from the keyboard...and put a little effort into building a few test enclosures. Then when I mention they'll probably need to spend a lot of time measuring and remeasuring each unit as they try each *tweak*...all of a sudden they tend to stop replying to my emails

Woofin' is like anything else in life---there ain't no free rides.

TV

[Dustin B]

Well, it will be a few years before I can start playing like that (if ever) as I have no intention of making a career out of building subs. HT is just a hobby for me.

Would you at least mention what these different tweaks I'd have to experiment with would be? I'm gonna make a career out of programming, I was hopeful you'd share some of your knowledge with a hobbiest though. As I have time for the keyboard, but not the time or money to do my own testing at this time.

[TVodhanel]

I had no intention of a career in the A/V industry either. I've spent most of the last 4-5 summers measuring subwoofers and the first two years of that was driven simply by the thirst for more understanding of what was really going on performance wise. I guess it all depends on how thirsty someone really is.

It is easy to get massive clean output >30hz from a decent 15" driver in a decent enclosure. Try sending it to Tom Nousaine for a real evaluation and see what the clean output at 20hz along with the FR

TV

[Manuel Delaflor]

Tom

The question here is how to evaluate the "clean" performance of our DIY sonosubs. I understand there are more factors than just the air displacement. But I wonder if we can do several distortion tests, or whatever else is important, to verify that the subs we can make can REALLY match the good comercial subs that we can find in the market (obviously, Im referring to yours).