funkz Posted January 3, 2010 Posted January 3, 2010 I'm looking to build a transmission line system similar to the LSK TL6, with this design. However the Vifa P17WJ drivers are no longer available and Vifa have a complete new range of woofers which have vastly different Thele specs than their old range. So there are no drop-in replacements. I have read good things about SB Acoustics and would like to do a TL system with 1 or 2 SB17NRXC35 units as they are nicely priced. Has anyone done this or have any experience with these drivers? I'm looking for a design as I'm not too experienced with designing them myself. Cheers.
Antripodean Posted January 4, 2010 Posted January 4, 2010 Unless the T/S specs for the SB match up nearly spot on then you are looking at a different design. In addition you need to know the crossover values. There are a few existing DIY designers out there with such designs. Try Troels. In addition, Zaph has been working with the SBs, normally as a BR. Otherwise try DIY audio to get some input from some great designers. Someone with Martin King's mathcad should be able to optimise the MLTL cabinet.
planet10 Posted January 5, 2010 Posted January 5, 2010 Start out by grabbing Martin King's alignment tables and start plugging numbers in (there is an accompanying spreadsheet) to get a feel. You don't want to just plug any driver into any TL. http://www.quarter-wave.com/ dave
Hifiplus Posted January 7, 2010 Posted January 7, 2010 The bass tuning would be pretty close, the SB 6" has respectable Qts & Fs. I would compare the SD (piston area) compared with the P17 - this will effect the exit & cross sectional area of the line. My other concern would be the top-end, the P17 had very smooth roll-off (poly cone), whereas this has smooth response to about 2k then a noticeable peak at 3.5k - this would may require a lower crossover point & possibly a notch filter, what is the tweeter you are using? As an alternative to the SB, have you seen the new Scanspeak discovery range? eg. http://www.madisound.com/catalog/product_info.php?cPath=45_228_256&products_id=8688 or if you want something that would be very easy to work with SEAS is always recommend. For quick comparisons I often look at Zaphaudio, this gives you a very good overview of what does what. http://www.zaphaudio.com/6.5test/ Andrew.
Paul Spencer Posted January 21, 2010 Posted January 21, 2010 funkz, My speakers which you linked are currently for sale. If I sell just the boxes then the drivers and crossover will be available. Getting drivers is one thing, being able to use them and get the best out of them is another. The crossover is the real challenge. Two of my drivers have been modified slightly. The mod gives them a flat extended response out to 8k and they don't have the strong break up that is shown on the SB Acoustics driver. I believe this is a big part of their laid back relaxed sound. With the 2.5 way crossover, the two modified drivers run as midbass drivers, while the other two unmodified drivers are woofers with a filter above 200 Hz. Essentially they provide bafflestep compensation and keep the efficiency decent.
funkz Posted January 25, 2010 Author Posted January 25, 2010 Thanks for everyone's replies, it has been helpful in deciding how to go about designing the TL. I happened to notice the other day while looking at new products on Jaycar's website, that they now sell the Vifa P17WJ-00-08 again! I thought these speakers were no longer produced by Tymphany?
Paul Spencer Posted January 25, 2010 Posted January 25, 2010 Just out of curiosity I tried running the mids without any filtering at all, and a simple high pass on the tweeter. The midrange was actually fine! It runs nice and smooth out to 8k. Most drivers you wouldn't even think about trying that with. Here's my listing: http://www.stereo.net.au/forums/showthread.php/12701-FS-Curved-custom-rosewood-TL-speaker-box-%28Melb%29?highlight=curved+speakers
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