The Metronome

[Scottmoose]

Hopefully I'll get chance to hear a pair at some point, but I do know the drivers & the general type of load, & I know the LS3/5a well. I'd put money on the Fonkens flattening them. LS3/5a = one of the most over-rated speakers in the world. They're good for what they are, but nor are they as good as mythology suggests.

[planet10]

Originally posted by marec
Here in the UK, for many people, live music is what the BBC OB department say it is... And, what they say it is, was for a long time dependant on LS3-5As.

People in this country have been burned at the stake for lesser heresy than yours.
]

I well know where i tred. I sold the BC-1s to my friemd brand new, and have sold many and owned a couple sets of LS3/5A

dave

[marec]

I owned and liked BC1s and BC3s and to my shame sold them both to pursue some illusion of dynamic range via horns.
I am glad that i still have my 3-5As (after maybe 30 years?), but wouldn't part with my lowthers...

[gurley123]

I'm blowing the dust of this one here. I've just scanned it from the begining and I don't belive I've found out what I was looking for.

Here's what I'm after. I am looking into making a folded Metronome (monilth) ,inspired by Dave's Milvena, for a bi-polar set of Pio A11s. After reading the Met. artical, It seemed that you take the 1/4 wavelength of the Fs for the line length. Then you Multiply the Sd by 4 (8 for bi-pole) for So(?) and since I'm doing a monilith, zero out the closed end. I think that's right. I've attached a pdf of what I think is right.

Now where I get confused is how you calc the port area and length. As of yet, I do not have access to Martin's spreadsheets so I do all this on my own. Other than some vague Bigger=less damping and smaller=more, I haven't heard anything on how these are figured out. Is there an equation? They don't seem to be tuned like traditional BR ports so what's going on?

If I'm missing something completely obvious. Feel free to smack me in the head with a slide rule.

P.S. I pulled the port in my drawing from the fe127 Met. doubled the area as it seemed the most likely candidate.

[planet10]

Originally posted by gurley123
After reading the Met. artical, It seemed that you take the 1/4 wavelength of the Fs for the line length. Then you Multiply the Sd by 4 (8 for bi-pole) for So(?) and since I'm doing a monilith, zero out the closed end.

No. That is not how you do it. Somewhere i outlined the procedure for turning a Met into a Monolith... but (the short version) you start by modeling an appropriate ML-TQWT in MJK. Fold it so that the driver is at the top, then you ignore the "top" which opens up the space that leads to a point.

The length needs to be longer than 1/4 Fs because it is a TQWT and the Sd plays no role at all in the design (except for the somewhat general & coincidental relation of Sd to Vas)

dave

[gurley123]

Ok, so delussions of grandure on my part then.

So without MathCad and the MJK sheets I'm stuck? I'm guessing the math for figuring the length, volume and taper are pretty involved and might just cause an aneurysm in the untrained like me.

The problem is that I don't have the jack to layout for Mathcad right now.(a quick search showed the cheapest versions going for $129.00) Plus it would be hard to justify that purchase to the wife.

Are there any simplified equations that could get me in the ballpark?

[Scottmoose]

No.

But you don't have to buy a copy of MathCAD, unless you want to save files. Martin links to the free MathCAD explorer on this page his site: http://www.quarter-wave.com/Models/MathCad_Models.html

[planet10]

Originally posted by Scottmoose
But you don't have to buy a copy of MathCAD, unless you want to save files. Martin links to the free MathCAD explorer on this page his site: http://www.quarter-wave.com/Models/MathCad_Models.html

After that the only expense is the token amount Martin is asking for his modeling sheets.

dave

[gurley123]

I have no problems with giving Martin his dues. That's only right and proper.

I had forgotten about the MathCad explorer. Since I forget many things I thought the full version was the one for me

I'll get Martin his money and see if I can't figure this out before my BUFu's arrive.

Thanks guy's.

[gurley123]

Just a heads up guys. It looks as though MathCad Explorer is no longer supported. They now have a 30-day trial. They also have a plug-in for excel. Anyone have any experience with this?