Transmission Line Help

[Fradbut]

Hi All - I'm looking into making a pair of ATR 2.5 's as designed by Troels Gravesen at http://www.troelsgravesen.dk/ATR-TL.htm. Based on his cabinet dimensions can anyone recommend or suggest replacements for his drive units as a) I can't source them in the UK and b) can't afford them !! but keeping the cabinets the similar dimensions, maybe different T line lenght. I'm looking at replacing the Audiotechnology units with the Vifa XT18W009-8 's and the ribbons with the Vifa XT25TG-30-04 's. Many thanks.

[Scottmoose]

Not the way to do it. You design a cabinet for a driver, not pick a cabinet & then wonder what to put in it. What you're basically after is a new design, from scratch. So, suggestion: shortlist a couple of drivers you can afford (hope you're good at XO design) & come back to us.

Depends on what you want to achieve. What do you want to achieve? The Vifas can be used for e.g., but it will depend on how large a cabinet you can stomach & how much passband ripple you are willing to tolerate.

[Fradbut]

Oki doki Scottmoose - I'm looking at *2 Vifa XT18's for low bass & bass to mid and *1 Vifa XT25 tweeter per speaker. Sizewise, similar to the ATR 2.5 as per the link (in first post). The Vifa XT18's are similar to the Audiotechnology units described in the Troels Gravesen original recipe, I know they're different and the cabinets would need adjustment. I'm after a bigger, full, deep but clear sound. I'm using Monitor Audio BR5's, good but they strugggle with a modern compromising sound.

[Scottmoose]

Then you'll need by modern standards a rather large cabinet. Remember that a TL isn't really about large amounts of bass-gain; they're by definition damped lines, and the LF naturally follows suit.

A 4:1 taper line, of the configuration shown in the attached, should give reasonable results. Line = 62.5in long. Throat = 105in^2, terminus = 26.25in^2. Centre-point between the two midbass units = 15.625in down from the throat. Stuff 0.87lbs ft^3 throughout cabinet. If you need more LF gain, adjust the stuffing density in the last 10in of the line. The price will be an increase in response ripple, but it wont be too drastic.

[Fradbut]

Thanks mate, much appreciated, these may be too big for the lounge, maybe it's best to go for a 2.5 vented box. Again thanks for your advice.

[Scottmoose]

That is, unfortunately, the downside to TLs. They're generally rather large. Worth it, but large.

Out of interest, how large can you go?

[Fradbut]

I was looking at something like this design http://www.troelsgravesen.dk/ATR-TL.htm. which is about 70 Litres, what do you think of his design ?

[Scottmoose]

Hmm. Good question. Speaking purely in cabinet terms, Troel states the drivers used are made to his spec., so that leaves us up in the air somewhat. Wombling over to the Jantzen audio site it looks to be a JA-6012, reading between the lines on what is written there, but take that FWIW, as a guess.

Roughly following his favoured damping, it's not bad, although I'd personally like to see more pipe volume (ironically enough, around the 70 litre mark -I make existing pipe volume at ~47 litres) and a couple of other mods.

[Fradbut]

ok cheers mate thanks for your help

[Scottmoose]

Narry a problem.