Nooby-noob thread. Appreciate pointers.

[chris661]

Originally Posted by iamthefly

Thanks about the ply. its only about £60 a sheet after tax. they also do an oak veneered ply which is cheaper that i might use. Cross bracing, gotcha.

I'm confused, I've checked the infinity in 3 different sources and its usable frequency only goes down to 23Hz, is it that is just close enough or is there something I'm missing? While we're on the subject can a human being destinguish between 20Hz and 23Hz?

Cheers

All speakers have a set of parameters describing their operation, called Thiele-Small Parameters, after the chaps that figured them out.
The parameters allow simulations (via a computer program - WinISD Pro is a useful one) of any given driver in any given cabinet.

http://uk.infinitysystems.com/tl_fil...260W_PI_EN.pdf

Here they are.

Have a look on t'interweb for what they all mean.

The 23Hz cutoff frequency (quoted by the manufacturer) is irrelevant - don't worry about it. The T/S parameters are what's needed to tell you what its going to do in your cabinet.

Chris

[iamthefly]

Ahh thanks. I've ordered a book. I'll look at that software right now. I had thought I'd be able to get away without doing the graphs and such, just build a box of the recommended size (most drivers seem to say 'designed to work in enclosures 45L-70L'), shove in a driver that specifies 20Hz and be done. Ah, we'll. I'm not against learning the math and software, just hoped I wouldn't need to. However my obsessive personality has snagged on this project so I have to see it through. I won't even get to play it that often because the darn thing will wake/terrify the kids. They'll thank me when they are old enough to play X-box games through it 'pew pew'.

I've also gone off TL it'd need to be about 80m long to tune it to 20 Hz. Thats a big box. sealed or vented will need to do.

[OscarS]

This article should be of use to you, having an EE degree

Engineering is the Best: January 2008

[ßart West-VL.]

Originally Posted by OscarS

This article should be of use to you, having an EE degree

Engineering is the Best: January 2008

Thanks! I've been looking for an article with T&S explanations.
I hope to, not just knowing what it means but actually understanding it.
more!more!

[iamthefly]

Thanks, will read it through when time allows

[Einric]

Have a look at the Legend of El Pipe-O'.
It is a subwoofer design that needs a room that is "Long On Space" and is suitable for 12"+ subwoofers.
It uses the transmission line design for loading the sub.
If I had a LARGE living room you bet I'd have one.

[OscarS]

Originally Posted by ßart West-VL.

Thanks! I've been looking for an article with T&S explanations.
I hope to, not just knowing what it means but actually understanding it.
more!more!

This is also a good paper:

http://files.engineering.com/downloa...com_101027.doc

[tvrgeek]

Just a basic reality check. Good clean subwoofer for $200? Sorry. About the cheapest I would call tolerable would be maybe a Dayton RS with an O-Audio plate. By the time you are done, you probably still have $350 in it.

Every car woofer I tested had terrible levels of distortion compared to what I can live with in my home. I still like my old Peerless XLSS 12's for music. Go read what Siegfried Linkwitz has to say about subs.

[GM]

Originally Posted by chris661

GM, thanks for the comparison. I am curious, though - why would the JBL need the bigger vent?
Surely the extra 1mm of Xmax isn't enough.

If they'll both hit 20Hz, I'd take the JBL for the cast frame - not much risk of bending it while tightening screws.

You're welcome!

It's a function of Sd, Fb, Xmax: TA Speaker Topics: Vent FAQ's

Sorry, but that's about the most ridiculous criteria for choosing a driver I've ever heard.

GM

[chris661]

Originally Posted by GM

You're welcome!

It's a function of Sd, Fb, Xmax: TA Speaker Topics: Vent FAQ's

Sorry, but that's about the most ridiculous criteria for choosing a driver I've ever heard.

GM

I fail to see how my criteria is ridiculous: Two different drivers will achieve similar performance for the same price, but one has a cast frame, the other being stamped steel.
I've heard of people over-tightening drivers with stamped frames, resulting in misaligned voice coils. In order to avoid that, surely it makes sense to go for the cast frame driver?