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Old 17th September 2013, 04:47 AM   #1
howardg is offline howardg  United States
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Default Howard's FF85wKeN

I am really enjoying my planet10 treated FF85wk pair, that are still being run in. Been about 5 days, playing most of the time. They are mounted in 15 liter cabs, with a 2"x .75" (preexisting) cutout as the port. They seem to be making more bass, and also doing a good job of suggesting the bass that probably isn't really there. Maybe because of how they reproduce the harmonics? In a way I hate to roll them off into a woofer, because of the "integrity" they seem to possess alone. But I also know that I will dig really hearing the low notes.
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Old 17th September 2013, 04:55 AM   #2
howardg is offline howardg  United States
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Default DREAMING AGAIN

The FF85wk has a QTS that is about right for a TL, no?

Cool project to use TL's to extend the little FF85's and use a TL sub to fill in below 100hz. Maybe use a 2.1 plate amp(with active x-over) and a tube preamp.
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Old 17th September 2013, 05:06 AM   #3
howardg is offline howardg  United States
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Default BUT MAYBE NOT

But looking here, I burst my own bubble:
.The Subwoofer DIY page v1.1 - Transmission Line Systems

Quote:
Usually, only drivers which have low Qts (0.25 - 0.4) , Qes (0.3 - 0.4) and Fs values are suitable for transmission line systems
The FS at something like 115hz, is not low. And the QTS at .55 is outside the range quoted above too.

Oh well.
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Old 17th September 2013, 08:23 AM   #4
howardg is offline howardg  United States
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Default ON THE OTHER HAND

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xrk971, FROM HIS ACCIDENTAL MLTL THREAD
Quote:

One thing that I am still trying to figure out is what rule of thumb to use to set the length? Right now, it is one of practical considerations as you usually don't want it too long. But at the same time, you want to keep it shorter than the quarter wave length of the fb.

So give a driver with a certain fs, sometimes it is possible to push its tuning to a factor of 2x below its fs. Take the TC9FD for example with an fs of 120 Hz. Because it is a high Qts driver, I can get down to 50 Hz, which is crazy. I know there is probably quite a bit of harmonic distortion here and the purists will poo poo this. But, for me, just getting to hear some nice bass around there with my wimpy 3.5 in driver is cool enough.

I have heard of rule of thumbs of not pushing your tuning below 75% of the fs. If I were to follow that for the TC9FD, I would have ended up at 90 Hz - not very spectacular or impressive at all. Anyhow, I think it has a lot to do with the Qts. I think this is where a program like WinISD is handy as it will let you see how ugly the BR curve looks like when you tune below the recommended frequency. The power of the MJK simulation is that you can actually predict how flat the final response in the MLTL will look, whereas with my AMLTL method - you are just hoping. So far the hope has panned out and produced several nice sounding designs.
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Old 17th September 2013, 10:16 PM   #5
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Default Stop dreaming. Get the best. Go BIB.

Quote:
Originally Posted by howardg View Post
The FF85wk has a QTS that is about right for a TL, no?
Your itty bitty driver will work very well in a BIB (Bigger is Better), a design from the late Terry Cain. It is a very forgiving design, with a lower than Fs useful output.

It does not do magic but it delivers
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Old 18th September 2013, 12:43 AM   #6
howardg is offline howardg  United States
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Hi ghpicard


Quote:
Your itty bitty driver will work very well in a BIB (Bigger is Better), a design from the late Terry Cain. It is a very forgiving design, with a lower than Fs useful output.
This is the second time recently that a BIB lover has pointed me toward bigger and better things. I believe that last time it was xrk971, but I am not having much luck remembering the context/driver in question.

I read a bit about the BIB, and I got the impression that various designers would re-size it to fit the size and other parameters of their drivers.

Could you refer me to a page that shows a picture, and gives me some idea how big one would be for a 3" driver?
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Old 18th September 2013, 04:31 AM   #7
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Quote:
Originally Posted by howardg View Post
Hi ghpicard

This is the second time recently that a BIB lover has pointed me toward bigger and better things. I believe that last time it was xrk971, but I am not having much luck remembering the context/driver in question.

I read a bit about the BIB, and I got the impression that various designers would re-size it to fit the size and other parameters of their drivers.

Could you refer me to a page that shows a picture, and gives me some idea how big one would be for a 3" driver?
Hey Howard
I have checked the BIB calculation spreadsheet (you can find it in the BIB's own thread)

http://www.diyaudio.com/forums/attachments/full-range/309366d1351690303-fostex-fe206e-bib-bib_166_gm_v2.xls.zip

and with a non-folded, floor loaded design (this is a slender cabinet with a rectangular front and triangle shaped sides, with the opening, the base of the triangle, firing to the floor, separated ~ 10 cm from it) it should be around 158 cm high (the cabinet itself is 148.70 cm plus the separation) with the driver about 32 cm from the top (point) of the enclosure.

In that spreadsheet you only plug-in the Fr, Vas and Qts of the driver to use and voila! you have the dimensions of the BIB. Be careful with the spreadsheet before cutting wood and all...
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Old 18th September 2013, 07:03 AM   #8
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Working to get as much bass as possible is usually paid for higher up. If you plan a woofer...

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Old 18th September 2013, 08:55 AM   #9
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The FF85wk does not do bass. You can force it to produce some. You can force a lot of tiny drivers to produce some. You will pay, as Dave says, a very heavy price for it in rocketing harmonic distortion. Just because it's possible to get LF from a tiny driver with a high Fo & miniscule linear travel does not make it a good idea. If you were planning on crossing to a driver designed to produce LF, do so. You'll get far better results.
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Old 18th September 2013, 01:25 PM   #10
sreten is offline sreten  United Kingdom
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http://www.quarter-wave.com/Horns/BL...gn_Article.pdf

Hi,

There is a lot of good things I could say about the above article.

What surprises me is that DIY'ers are not all over it like a rash.

However I'll note it produces bass below driver Fs and produces
more bass SPL than any simple box approach. As it reduces and
controls bass excursion it will also play louder then normal.
It also avoids the honky midrange of many other designs.

What's not to like ?

rgds, sreten.
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Last edited by sreten; 18th September 2013 at 01:28 PM.
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