# CSS SDX7 Transnission Line



## angelod307 (Oct 18, 2007)

hello. i really am interested in these drivers in a project that i want to use them in with a set of ribbon drivers. i am very interested in using the sdx7 in a transmission line cabinet. the ribbon driver is the one that swan/hifi makes under the brand dayton,carver, as well as others. the crossover could be as low as 2500 if a 18-24bd design is applied. the transmision line box though would be a first for me and i have no clue as to were one starts in modeling such a thing. 25 years plus building boxes, but never a tl. thanks for the help on this guys, angelo.


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## Mike P. (Apr 6, 2007)

Same here, built lots of sealed and ported but no TL. Hopefully someone will chime in.


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## angelod307 (Oct 18, 2007)

well, after reading a few threads, i came accross this link for a fostex 6.5 as well as the 8". maybe i will try them and see what pot luck is....although i like the first design better.

the link:

http://www.madisound.com/pdf/fostexcabs/Fostex BK16 Cabinet.pdf

http://www.madisound.com/pdf/fostexcabs/206e_encl.pdf


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## planet10 (May 27, 2007)

angelod307 said:


> ... Fostex BK16 ... 206e_encl...


The 1st was designed a long while ago for the FE166, a driver completely unlike the SDX7. The 2nd, from practical experience, is not even recommended for the FE206.

Both are horns (actually horn/QW hybrids since they have compromised mouth size). There are better enclosures for the drivers they were intended for, and using with SDX7 would indeed be pot luck. 

dave


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## planet10 (May 27, 2007)

The SDX7 is one of my favorite bass drivers. I have built a TL for these.










Because the SDX7, like the other XBL drivers i have used, is very linear right up until it hits the stops, unless you have some sort of acoustic loading on them way down low, they make a quite disturbing sound when they do run out. Hence, i ended up stuffing the TL until it was aperiodic, and then i had no issues, with well controlled bass down to 35-40 Hz.

Since then i have just been putting SDX7 into sealed enclosures with 10-17 litres per driver (min 7 litre, max 21 liter), where i get similar bass extension and no problems with bottoming out.

The other thing that will play a role here is the SDX7 top end response. Stock the driver gets rough before falling off just over 1k. With a very simple modification the roll-off becomes well controlled at about 1.1k. This mod also improves the drivers downward dynamic range.

This HF limit is going to be problematic with all but the most robust ribbon tweeters. In a 2-way i typically crossover 100-500 Hz, 100 Hz in the system pictured above, 333 Hz in Tysen to a Fostex-based FF85Ken, and i'm targeting 200-250 Hz in a system that i'm working on right now that will have 4x SDX7 XOing to a Mark Audio Alpair7eN.

dave


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## Mike P. (Apr 6, 2007)

Thanks for the input Dave, it's appreciated!


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## mdrake (Jan 31, 2008)

> Because the SDX7, like the other XBL drivers i have used, is very linear right up until it hits the stops, unless you have some sort of acoustic loading on them way down low, they make a quite disturbing sound when they do run out. Hence, i ended up stuffing the TL until it was aperiodic, and then i had no issues, with well controlled bass down to 35-40 Hz.
> 
> Since then i have just been putting SDX7 into sealed enclosures with 10-17 litres per driver (min 7 litre, max 21 liter), where i get similar bass extension and no problems with bottoming out.
> 
> ...


Great info! :T 


I have heard you can use hornresp to calculate a tl but I have not tried it. 
I use a simple method of using the SD of the driver as the line diameter and the length of the line as the 1/4 wave of the fs of the driver and then experiment from there. 

Matt


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## planet10 (May 27, 2007)

mdrake said:


> I have heard you can use hornresp to calculate a tl but I have not tried it.


Matt

You can, but it won't account for damping. Martin King's QW software is much more powerful.



> I use a simple method of using the SD of the driver as the line diameter and the length of the line as the 1/4 wave of the fs of the driver and then experiment from there.


Like this. Classic design methodology. Problem is that Sd has little to do but determine the minimum baffle width. Much better to use Martin's Design Tables (bottom half of the page).

dave


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## mdrake (Jan 31, 2008)

> Like this. Classic design methodology. Problem is that Sd has little to do but determine the minimum baffle width. Much better to use Martin's Design Tables (bottom half of the page).
> 
> dave
> 
> Read more: CSS SDX7 Transnission Line - Home Theater Forum and Systems - HomeTheaterShack.com ​


Does anyone know how to translate these tables so the normal people can use these? :scratch:
I learned hornresp but I cannot wrap my head around these tables. If we could figure out how to translate these table then question's like the original op's would be easier to answer.

Matt


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## planet10 (May 27, 2007)

There is also an excel spreadsheet there that you just plug the numbers into.

dave


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## mdrake (Jan 31, 2008)

planet10 said:


> There is also an excel spreadsheet there that you just plug the numbers into.
> 
> dave


Thanks Dave! :T I missed those at first glace. 

Building the CSS SDX7 a transmission line using the excel spread sheet should be pretty straight forward. Sounds like a fun project. :T

Matt


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## angelod307 (Oct 18, 2007)

nice job. thanks for the link. i will see what i can understand and ask about what i don't.


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## angelod307 (Oct 18, 2007)

hmm. all i have is an excel veiwer thus i can't plug in the numbers on the sheet.


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## planet10 (May 27, 2007)

The spreadsheet is simple, it should work fine in OpenOffice (neoOffice if you are on a Mac)

dave


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## Henkjan (Sep 14, 2009)

planet10 said:


> There is also an excel spreadsheet there that you just plug the numbers into.


here it is...


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## Henkjan (Sep 14, 2009)

angelod307 said:


> hmm. all i have is an excel viewer thus i can't plug in the numbers on the sheet.


and here's the OO version (a bit less sophisticated than the excel version)


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## angelod307 (Oct 18, 2007)

same problem. do not have the software for even office.


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## mdrake (Jan 31, 2008)

Open office is free and you can download it here. http://www.openoffice.org/ 

Matt


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