Transmission line box?

[customsuburb]

I have a generic 8inch sub that is just sitting around and I thought i would attempt to make a transmission line box for it. Shold i try making a folded horn or just a regular transmission line? It would be going into a car so it can be fregirator sized... It would also be receiving its rated power whatever I put it in (70 watts continuous).

Also I searched but I couldn't really find a formula or way to decide on how to design the box. It would be helpful to have .

[Nuuk]

I built a pair of subs using 8 inch drivers and the results are excellent. You can read all about them here .

I'm not sure if you would get one in a car without taking up a lot of the boot (trunk) space!

[Skramstad]

Formula for short transmission line:
Length = quarter wavelength of fs
Start area of line = 2*Sd
End area of line = Sd
If your crossover point is high, you should use some stuffing/insulation inside the line and make the line a little bit shorter.

Folded horns for car use: works very well if you have enough free space, but sounds awful in a small trunk. That is my subjective point of wiev, but you should try it out anyway cause it may give you a good time:)

Nice project Nuuk!

I'm soon finished with a pair of TL boxes for the Fane Crescendo 15MB. This is the first TL boxes of mine, so I look forward to hear the results in a few days.

[BillFitzmaurice]

You might be able to use my AutoTuba design, but the driver requirements are fairly restrictive. I'd have to know the T/s specs to know if it would work for you.

[customsuburb]

Would a folded horn be a better choice. I'm thinking of buying a JL 8inch W0 woofer or a inexpensive peerless (I would probobly try the woofer I have right now and buy one of the two I mentioned if I didnt like it). Also what is the formula or way to figure out how to make a folded horn box?

So far From what I understand a transmission line box can play low but not that much louder then a regular sealed or ported box and, a folded horn box can play extremely loud with minimal power (sounds like a better goal to me). Please correct me if I'm wrong on this.

Thanks for the help from everyone so far

[Skramstad]

A horn should be more efficient than a TL box, and have better transient response. But you have to follow the guidelines of physics during the design. A basshorn should never be shorter than two meters (around 40 Hz cutoff), four meter or longer horns should be considered. In most cases a properly designed horn is to big for the room or car. Then a TL box can be a good choice.

[customsuburb]

So if I wanted to make a horn with a 40 hz cutoff frequency it would automatically be 2 meters long about, or is there more to it?

I was searching and found this website on horns: http://melhuish.org/audio/horndesign.html

I did all of the calculations but I'm confused on how to put it all togethor (how to use those calculations to make the actual dimensions).

Sorry for asking all of these questions but I really want to make either a Folded horn or TL enclosure. Thanks

[BillFitzmaurice]

Yes, you need 2 meters, but there's a lot more to it than just that. A horn is probably not the best idea for one's first foray into speaker design. I built quite a few Altec, Jensen and Klipsch clones before I learned enough about the beasts to roll my own.

[Skramstad]

Like BillFitzmaurice says, there is a little bit more to it than 2 meters, but if you download McBeans hornresponse analysis program http://www.users.bigpond.com/dmcbean/ everything should come easily after a few days testing.
Remember to check the help text each time you meet a problem.

Still there is a problem to transform your calculations into actual dimensions if you're not familiar with a CAD program. McBean revolves the horn curve around one axis, so you will always make a radial horn. There is not a big problem to transform a radial basshorn to an easier to build format, but it is much easier with a CAD program.

I can run a calculation if you give me this information:
1. What are the Small & Thiele parameters on the driver you're going to use?
2. How low do you want your horn to play?

[customsuburb]

1. What are the Small & Thiele parameters on the driver you're going to use?
2. How low do you want your horn to play?

I think I would like to use a JL W0-8. FS 31.9 hz, Qes .447, Qts .426, Qms 9.029, Vas 1.02 sq feet (28.9 litres), Xmax (one way) 6.8, SPL 85, SD 33.8 inch sq. , RE 3.30 Ohms, nominal impdence 4 ohms, power handling continuous 75,

driver displacement .023 litres ft 3.

35 hertz is probobly the lowest bass I would play through it.

I did do some of the calculations (tuned to 40 hz I think):

Throat Area .247 (m2)

Compression chamber .34 (m2 I think...) I used another formula and got .50 instead.

L1= 3.26875 (inches)
L2= 4.225 (inches again)
I couldn't figure out what AT was in this calculation: LT= At/box height

I tryed another formula to get the slant angle but again i Don't know if its even close... 1.67 * woofers SD= 56 degrees.

If you have time could you also run calculations on this dayton driver also? I would also like it to play to 35 or 38 hz (unless the box is going to fridgerator sized for that low of a frequency). Here are the parameters for it Specifications:

*Power Handling: 80 watts RMS/120 watts max *VCdia: 1.5" *Le: 1.2 mH *Impedance: 8 ohms per coil *Re: 3.00 ohms *Frequency range: 30-2,000 Hz *Fs: 28 Hz *SPL: 89.0 dB 2.83V/1m *Vas: 1.40 cu. ft. *Qms: 3.40 *Qes: .47 *Qts: .41 *Xmax: 6 mm *Dimensions: Overall Diameter: 8-1/2", Cutout Diameter: 7-1/8", Mounting Depth: 4-1/4".

http://www.partsexpress.com/pe/showd...number=295-480 (there is a PDF on this page with more parameters if needed).


I used this thread on the sounddomain forum : http://forum.sounddomain.com/ubb/ult...1;t=070826;p=3

and this website on horns for compression chamber and throat area: http://melhuish.org/audio/horndesign.html

So am I even close on any of these? lol

Thank you very much