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DIY FB1i anyone?

defo WG , wilmslow audio do them for £45 ea. The full no is VIFA M17 WG 09 08.
OK some more info. The top of the transmission line ends 4 and 1/4" from the inside face of top panel and it is 4 and 7/8" from the inside face of the front baffle (Measured to the front top corner of the transmission line)
 
The Panel for the base of the speaker is 5/8" thick and the lower part of the transmission line is as follows. Height above the inside of the base 4 and 1/4" , this is the bit that exits out of the "port". The lower end of the transmission line is also 4" from the inside of the rear panel.
all panels except the base are defo 3/4" thick , including the panel that makes up the line.
 
Dick Bowman said:
Can't really see the point in DIY copying. Surely more to be had in getting to understand underlying principles and construction techniques, then trying something original.

As for commercial duplicates where we can only judge the outsides...
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There was a time the ProAc Response 2.5 was the most copied commercial design in the world. However, I don't think many got close to the original's performance. That said, copying an existing design is a great way to learn about DIY loudspeakers.

James
 
Zener, Good man!

We have confirmed the correct midbass and have enough data to know we can get close to duplicating the enclosure. I'll get to work on drawing up cabinet plans soon. I intend to have a panel list also.

Next problem is to solve the crossover. I can buy a FB1i (not sure about FB1+) xo but they want £82 for one. If its not possible to find schematics this might be the only option. If anyone else is interested would they mind chipping in to cover the cost. Once we have one we can draw up a schematic and source the same components to make up as many as we want.

http://www.technosound.co.uk/nav.php?pageid=SpeakerSpares#PMC

(The same company claim to have the 'i' version tweeters, but £102 each is mad)
 
Heres the preliminary 'cut and paste' for the FB1'i'. Tomorrow I'll start adding the dimensions given by Zener and begin roughing out other dimensions. Eventually I'll pass it on to my freind the CAD expert to be re-drawn from scratch. This will ensure the dims are correct and enable a drawing to made of each individual panel.

l_df48e7da387ef04d4ec70e30453dcc9e.jpg
 
A couple of ideas, which you can ignore if they aren't useful - its your project after all.

From skimming the Mike King documents, one of the key things in making/tuning a transmission line is the cross sectional area of the line. If you want or need to change say the panel thickness, increase the depth of the box so as to preserve the free area.

The air flow likes to go smoothly round corners. If you look at some of Troel's designs or some of Eekel's, they put curved sections in where the line doubles back on itself. Without going that far, you could add some stiffness and smooth the flow a bit by putting some triangular section fillets (cut from some triangular section beading or similar) in the front and back top corners, and in the bottom back corner. You could also round the edges on the top of the inner vertical bit of wood.
 
Re. smoothing airflow - whenever modifying high performance turbo engines I always pay very close attention to same, it is worth the effort. I always found it easiest to think of water flowing through the space, instead of air, and that there are little fish in the water. You need to design it such that the fish are disturbed as little as possible as they flow through the space.

Richard
 
PigletsDad said:
A couple of ideas, which you can ignore if they aren't useful - its your project after all.

From skimming the Mike King documents, one of the key things in making/tuning a transmission line is the cross sectional area of the line. If you want or need to change say the panel thickness, increase the depth of the box so as to preserve the free area.

The air flow likes to go smoothly round corners. If you look at some of Troel's designs or some of Eekel's, they put curved sections in where the line doubles back on itself. Without going that far, you could add some stiffness and smooth the flow a bit by putting some triangular section fillets (cut from some triangular section beading or similar) in the front and back top corners, and in the bottom back corner. You could also round the edges on the top of the inner vertical bit of wood.
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Good point to raise. Its tempting to try and improve the FB1 I do agree. My only consideration is that PMC have spent years developing the design of their speakers and I feel that deviating from the design might kill the the PMC'ness (if you know what I mean).

However, you raise a valid point so It's worth considering. Would adding corners reduce the effective area of the line and negate other alterations to the enclosure?

Dowser, nice analogy. How about Glass peakers with fish inside!!!! (Joke):D
 
mikesnowdon said:
GWould adding corners reduce the effective area of the line and negate other alterations to the enclosure?
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I think it should be OK if the corner fillets are small enough so that the cross section is never smaller than in the adjoining straight bits of the line. If the baseline of the fillets is less than half the line width, I think this is guaranteed.

In practice, I think the improvement might be biggest for the one near the mouth (bottom back corner), as the air velocity is highest there.

Also, the top front corner is pretty constrained by the tweeter cutout, so you probably can't do a lot there.
 
a quick look around at pricing - you're looking at about 170-180 ish for the drivers (not delivered), prob 50 or so for the crossover parts depending on what caps you go for, then there's the wood, foam, spikes and any tools you need to buy. Certainly an investment! I know the challenge is the main thing, but it's not something to take on lightly given there's no guarantees. (ever the pessimist me, just ask my mates)
 
Having looked at this design on Troels's website am I right that the FBI is actually a TQWT variant rather than a traditional T Line?
 
Hi, Pigletsdad

Hand plane and coping saw 5 min job, it dosn't have to scream to cut wood.;)

Pete
 
mikesnowdon said:
Having looked at this design on Troels's website am I right that the FBI is actually a TQWT variant rather than a traditional T Line?
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Mike King points out that there is a whole family of related designs, all based on long pipes that are tuned to resonate at or near the driver resonance, but with differing tapers. A TQWT is thin at the closed end, in fact tapers to a point, and widens to a maximum size at the open end. The FB1 looks like it is wider at the closed end, and gets slightly smaller towards the port, so I think it more or less belongs in the T-line side of the house.

From a certain point of view a reflex cabinet can be thought of as an extreme member of the same family, where the pipe length is no longer what sets the resonance, but rather the box volume and port inertance.
 
PigletsDad said:
A site with some useful background on transmission line speakers (and related designs) is Martin King's - http://www.quarter-wave.com/.

I realise that you are primarily trying to clone an existing design, rather than do a new one from scratch, but some of his material, or one of his spreadsheets, may help tweak the design for the differences (if any) between the driver that PMC use and the Vifa M17WG-09-08.
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I strongly support PigletsDad here. Even if you copy (or try to copy) an existing design, the 25$ Martin King asks for a mathcad model are a bargain. It could save you a lot of time optimizing your design, especially for the damping material.

I certainly was extremely happy with the results I got, using the P17WJ and D26TG: http://www.diyaudio.com/forums/showthread.php?s=&threadid=85736
 
mikesnowdon said:
Heres the preliminary 'cut and paste' for the FB1'i'. Tomorrow I'll start adding the dimensions given by Zener and begin roughing out other dimensions. Eventually I'll pass it on to my freind the CAD expert to be re-drawn from scratch. This will ensure the dims are correct and enable a drawing to made of each individual panel.

l_df48e7da387ef04d4ec70e30453dcc9e.jpg
Click to expand...

Sorry I havent done this yet. The new arrival to our family and busy shedule have kept me rather busy. I'll try and get started this week and hope to at least have Zener's data included so I can confirm If I've duplicated his measurements correctly.

By the way, I won a pair of Vifa M17WH-09-08, placed bid before this thread began, pissed that theyre not the right drivers! Still, it will be fun to play with them so Im going to try them in my TDL's and see how they perform. Wilmslow audio reccomend the M17WG's as a direct replacement for the RTL2 midbass, without the need to tweak the crossover......?

Hope you all had a nice weekend. :)
 
00940 said:
I strongly support PigletsDad here. Even if you copy (or try to copy) an existing design, the 25$ Martin King asks for a mathcad model are a bargain. It could save you a lot of time optimizing your design, especially for the damping material.

I certainly was extremely happy with the results I got, using the P17WJ and D26TG: http://www.diyaudio.com/forums/showthread.php?s=&threadid=85736
Click to expand...

Id like him to take a look at this, how do I contact him?
 
mikesnowdon said:
Id like him to take a look at this, how do I contact him?
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I don't think you do, he has downloadable software (Mathcad workbooks) that he sells that contain all his formulas and design tools.

Also, he has published lots of documents with useful stuff, and these are available without charge.
 
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