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View Full Version : 1/4 wave TL design help

AllDayMJ
06-13-2009, 01:20 AM
so i did all the math for a pair of 07CVR10's.. Sd=(58.7x2)=118sq.in Fs=33.2hz

1120/4=280/33.2=8.4ft long ~102"... port:10"x12"

externals are 38"x22"x13", using .5"mdf with a 2x baffle on the front..

box i got out of it is 8.75ft. long which is about 32hz

lemme know if i got any calculations wrong and i did a sketchup..will this work with the second sub so far down the line already?

line measurements are 26.5", 20.5", 37", 21.5" from front to back
http://img195.imageshack.us/img195/5751/cvr10tl.jpg

Random1010
06-13-2009, 02:14 AM
Doesn't look long enough to me

Edit: and let me guess, "That's what she said..."

80INCHES
06-13-2009, 02:37 AM
thats not a 1/4 wave box...its looks more like a spl box for 2 10's

80

Random1010
06-13-2009, 02:39 AM
x2 and I don't see 102" of line in that thing. If that is even the correct measurement. I'm too tired to work through a quarterwave right now.

Volenti
06-13-2009, 02:39 AM
I've done plenty of T-lines with the 2nd sub partly down the line, works fine (can actually smooth the response a little). It's not untill the sub is over 1/3 of the way down the line that you start having significant negative effects.

Just give the open end plenty of room to breathe in the car, these lines are particularly sensitive to loading.

 and yes it does look too short for a 32hz line though I have done similar length lines for customers and they liked em so "shrug".

AllDayMJ
06-13-2009, 11:54 PM
well the box is 38" wide and almost 2 ft deep..and i only need 8 some feet..so 6 ft both directions and almost 2 ft in both back and fowarth directions..its a quarter wave so its not a full TL..

AllDayMJ
06-14-2009, 05:25 AM
help..?

Volenti
06-14-2009, 09:04 AM
help..?

I just modeled it in my horn simulation software (which will also model TL's), your design just needs to add another 10'' to the total length of the line for a correct response.

 or, you can keep the current enclosure dimentions and taper the line instead, 12''x11.75'' at the closed end down to 12''x7.75'' at the open end, the response is practically identical either way.

AllDayMJ
06-14-2009, 06:11 PM
I just modeled it in my horn simulation software (which will also model TL's), your design just needs to add another 10'' to the total length of the line for a correct response.

 or, you can keep the current enclosure dimentions and taper the line instead, 12''x11.75'' at the closed end down to 12''x7.75'' at the open end, the response is practically identical either way.

this?

http://img19.imageshack.us/img19/6214/taperedquarterwavetl.jpg

AllDayMJ
06-15-2009, 01:07 AM
bump

Volenti
06-15-2009, 02:41 AM
The 7.75'' width is the line end, not an internal measurement, imagine the line as a straight tube that's 12'' high, the closed end where the subs are is 11.75'' wide, the open end is 7.75'' wide.

Fold this up in your enclosure space, start at the port end, make it 7.75'' wide then increase the width as you get to the closed end, your drawing is on the right track as a concept (other than the 7.75'' measurement)

DNick454
06-15-2009, 02:52 AM
Quick question... Where can you find the length needed for a transline route for a said tuning frequency. I've been really interested in trying one of these. Also, if you can't quite achieve the full quarter wave length, you just line the enclosure with polyfill to achieve the correct tuning right?

Volenti
06-15-2009, 10:59 AM
Quick question... Where can you find the length needed for a transline route for a said tuning frequency. I've been really interested in trying one of these. Also, if you can't quite achieve the full quarter wave length, you just line the enclosure with polyfill to achieve the correct tuning right?

First off, polyfill doesn't really effect T-lines like that, it will damp the line and this effects higher frequencies more than lower ones, so when you listen to the line before and after, the "after" sounds like it's going lower than the "before", when it's really just filtering out the higher frequencis more.

Not that it can't be used to good effect though, and I often partially stuff lines that have to be made "too small" to fit in the vehicle, it just won't lower the tuning frequency by any meaningfull amount. (essentially I can make a small line have a similar response to a larger line with carefull design and stuffing, but the large line will have far greater output)

Now, design, all though tapered lines are harder to fold and build, they are the most forgiving acoustically.

Try this, get the sub/s you intend to use, measure the cone area, make the start of the line (where the subs are) 1.5 x total cone area, make the total line length 70''- 80'', make the open end of the line 0.7 x line area.

That will give you a pretty balanced response with a majority of the subs on the market, especially high power/stiff suspension (spl ect) subs, anything that's normally designed to handle abuse in a ported box.

I make "cash'n'carry" enclosures based on those ratios, if you want more punch, make it shorter, if you want a lower response, make it longer, simple :)