A question for you Techies!

[Swerv]

Ok. In my upcomming review I would like to compare the air displacement from the sub of the ultras with the 5.1s

given the fact its an 8 inch driver and it has a 60 percent longer voicecoil does this translate to slightly more excursion from the cone? Or just greater power handleing?

Say I wanted to state the displacement PER stroke of the dual 8 inch promedia woofers in L.

How would I calculate the maximum air displacement per stroke(one way of the X-MAX Or would it be both in and out combined???)

Anyone that can clear this up will help me greatly, thanks!

[Swerv]

I'd also like to add another question. Someone stated to me that the surface area of 2x 3 inch drivers is the same as a 6 inch driver. I was under the impression that this comparison is wrong and that it would actually be less than that of a 6inch driver, could someone clarify this too?

Thanks in advance

[noobzilla]

I can't answer your first question, but your second one is do-able with middle school math. Area = (pi)(r^2), so the combined area of 2 3" drivers is 14.14 square inches. One 6" driver is equal to 24.27 square inches. Basically, it takes 4 small circles to cover the area of one circle that's twice the size.

EDIT: Wow, my pi symbol didn't turn out exactly as it should have. I replaced it with the word.

[Swerv]

Thanks for clearing that up, I was able to get the answer myself with a bit of searching, rather embarassing that I didnt remember, but I had to be sure!

thanks

[fabulousfrankie]

To get the dispacement(Vd) in liters you need to take the surface area of the driver(Sd) measured in cm^2 and multiply it by the peak to peak linear excursion measured in cm. This will give you an answer in cm^3, since 1000cm^3=1L just divide what ever you get by 1000 and you'll have your answer in L.

For example here's the woofer I have in my HT, the Stryke AV-15.

Sd - 802cm^2

One way Xmax - 23mm=2.3cm

Sd x Xmax x 2(because we need peak to peak)

802 x 2.3 x 2=3689.2cm^3

3689.2/1000 = 3.6892L

Since Klipsch doesn't sell their drivers seperately the T/S parameters aren't readily available, maybe a call or email to tech support. The Sd of an 8" driver is usually around 220cm^2 so if you can find just the Xmax you can at least get close.

[Dustin B]

I'd be utterly amazed if Klipsch told anyone who asked what any of the T/S parameters of the drivers in the Promedia speaker series (or any of their series for that matter) are.

Frankie's estimate of 220cm^2 for the 8" driver's SD is very reasonable.

Estimates at Xmax will be complete shots in the dark. But I'd guess the P-P Xmax of a driver in a promedia sub at absolute most to be 20mm. More than likely less than 16mm. So the original 6" version would have had a Vd around 0.25L and the new ultra one to be in the 0.5 - 0.75 L range.

With enclosures as small as the Promedia sub enclosures, and slot ports I'd guesstimate the tuning point to be in the high 30hz low 40hz range.

So as far as multimedia computers speakers go, quite impressive. As far as home audio / home theater goes, well do I really have to say it

[Swerv]

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On 10/18/2003 11:29:15 AM fabulousfrankie wrote:

For example here's the woofer I have in my HT, the Stryke AV-15.

Sd - 802cm^2

One way Xmax - 23mm=2.3cm

Sd x Xmax x 2(because we need peak to peak)

802 x 2.3 x 2=3689.2cm^3

----------------

How would one come up with a Guestimate of the promedia subs xmax, by looking at the thickness of the surround?, is it physically impossible without the numbers from the driver company??

So for the promedias it would be what the previous poster said:

say it was 20mm total both ways , 220 cm^2 SD,

so you get 2x220= 440/1000 = 0.440 L X the two drivers in the sub

= 0.8L

So the total air displacement per stroke(from the 2 drivers) would be this, Is that a reasonable number or would you guys think it has much less than 20 mm both ways. I'd like to know how you guys come up with this guess.

Even though I guess thats not bad compared to alot of the multimedia competition...

Thanks again guys

[Swerv]

Edit I just measured the actual driver diameter seems to be about 7.25 inches or 180mm

so we get : 90mm x 90mm x 3.14 or 254.34cm^2

at 20mm peak to peak we get 1.017 L combined from both drivers, does this sound right or does it sound like way to much?

[Dustin B]

Drivers Sd isn't just the area of the circle made by the driver. There are some funky formulas that take into account the shape of the cone and the surround. An 8" driver designed for use as a mid from Adire has an Sd of 231cm^2 and P-P Xmax of 11.2mm (rather long for a driver of this type). So a driver meant for bass duty will have a larger surround resulting in a smaller Sd, and given the price point I'd really be surpised if the Xmax was more than 16mm.

No way to guesstimate Xmax just from measuring the driver. If you could take it appart and see how long the voice coil and pole pieces are then you could know the mechanical travel limits, but depending on the driver design Xmax can be very close to this or much less. You can get most of the T/S parameters of the driver if you have a voltmeter and some know how, but Xmax requires some specialized measuring equipment to get an accurate number.

I'll stick by saying my best guess is upper bound for possible total Vd of the Promedia Ultra sub would be 0.75L.

[fabulousfrankie]

There's no way to really tell the Xmax unless it's given. I also doubt if they'll give any info out but you can always try. At least try to see if you can get just the Xmax(make sure you find out if it's p-p or one way).