FE127 Fonken Spacer dimensions

[captain pugwash]

I'm a bit confused by the FE127e Fonken port and spacer dimensions - the plans show 3" ports and spacers of 1 1/16", the notes suggest spacers of 1 1/32" but with an internal box height of 13" and 3 ports, shouldn't the 4 spacers be exactly 1" ?

[chrisb]

Originally Posted by captain pugwash

I'm a bit confused by the FE127e Fonken port and spacer dimensions - the plans show 3" ports and spacers of 1 1/16", the notes suggest spacers of 1 1/32" but with an internal box height of 13" and 3 ports, shouldn't the 4 spacers be exactly 1" ?

If you're working from the earliest version of the drawing, note that all panels except the baffle are indicated at 12mm (1/2") Not long after this drawing, we normalized to use of 15mm material for most enclosures, which we found sounded much better. We've also used 3/4" bamboo plywood for at least 1/2 a dozen pairs.


I'd have thought that Dave would have revised the sketch linked on his site by now, but since I've always redrawn my own to create cutting plans and CNC patterns as needed, I hadn't noticed .

Changing to thicker materials and our choice of joinery methods would obviously affect at least one dimension of all cut parts - the important thing would be to maintain the internal volume, and the height / length of port slots.

I've built dozens of pairs of this design and its numerous descendents - as a personal aesthetic, I prefer the spacers between the slots to have the same overall height as the combination of those at the end and the top/bottom panels. As noted above, these would be affected by the thickness of material used.

Using 1/2" as drawn, I'd make the middle spacers 1" each and the end 2 1/2" each. Yes, (13-(3*3))/4= 1" but that does not include the top / bottom.

[captain pugwash]

doesn't that increase the port size to approx 3 1/3" each?

[chrisb]

Originally Posted by captain pugwash

doesn't that increase the port size to approx 3 1/3" each?

Yeah, I misread the drawing (the 13" is inside the top/bottom panels), and hastily spouted off calculations based on the wrong starting point. Certainly neither the first or last time


I've been using metric for so long on enclosures that imperial always messes me up, plus the conversions on Dave's sketches aren't always accurate: 3" = 76.2mm not 75mm - I wouldn't normally worry about a single occurrence of less than .5mm, but 3 x 1.2mm = 3.6mm ( .142" , well over 1/8")



So working in metric, you have 330.2mm (13") - 228.6mm (9") = 101.6mm (4") of total spacer blocks to be divided as you like. If I revisit my calculations, that'd give 4 @ 1", or the inner 2 @ 1.25 and the end 2 @ .75".

I just happen to prefer the look of the second option.

Of course, as noted earlier, changing thickness of material would affect the dimensions of the spacers if you want a more symmetrical look.

[planet10]

Originally Posted by captain pugwash

I'm a bit confused by the FE127e Fonken port and spacer dimensions - the plans show 3" ports and spacers of 1 1/16", the notes suggest spacers of 1 1/32" but with an internal box height of 13" and 3 ports, shouldn't the 4 spacers be exactly 1" ?

It makes more sense in metric.

Email me for a URL to the more complete (but never finished) planset.

dave

[captain pugwash]

As always you've been really helpfull chaps, much appreciated - I will mail you for the plans Dave.
This will be my second pair of Fonkens, I made the first a few years back and love them, they are one of the best speakers I have ever heard at any price!!
I must have missed the port spacer discrepency first time round and cut them as per the notes. I wish you hadn't told me that the 15mm version is better than the 12mm as I've just got in the 12 ply at the the weekend!! - how much better is the 15mm version and in what way??

[chrisb]

Originally Posted by captain pugwash

As always you've been really helpfull chaps, much appreciated - I will mail you for the plans Dave.
This will be my second pair of Fonkens, I made the first a few years back and love them, they are one of the best speakers I have ever heard at any price!!
I must have missed the port spacer discrepency first time round and cut them as per the notes. I wish you hadn't told me that the 15mm version is better than the 12mm as I've just got in the 12 ply at the the weekend!! - how much better is the 15mm version and in what way??

firstly, sorry about that - 15 is much stiffer than 12, which we've found in general to be a good thing, particularly with larger enclosures (make your own joke)


on smaller designs such as the milli or micro family 12mm has worked just fine, particularly on those such as the Fonkens that include a lot of bracing

to take advantage of trade quantity pricing, I generally buy plywood in lifts of at least 20sheets at a time, and it's simpler to keep fewer thicknesses in stock, and we found the 15mm BB to be a happy medium

[planet10]

Originally Posted by captain pugwash

as I've just got in the 12 ply at the the weekend!!

Looks like i might have to bring the 12mm plan up to date and put it back into the planset.

dave

[captain pugwash]

Well, after a sleepless night I've decided to stick with the 12mm ply! but thanks for the planset Dave, some very interesting options for the future.

[NZkeith]

Hello there Folks, greetings from New Zealand... I have been following with great interest the info and comments about 'FONKEN' speaker cabinets...

Can someone please fill me in on their performance. I build speakers and valve amps as a hobby and like a bit of a challenge, especially when the design is a bit 'out there' and not to the norm...

Also I would like to use the drivers AND tweeters from a OLD pair of 'TANNOY Mercury S' speakers. The only reason for doing this is that I have these speakers in hand and the cabinets are rather 'sad' as the previous owner has let them get damp and the cabinet timber has 'blistered' and looks rather unattractive... They still sound absolutely stunning with drivers in brilliant condition.....

Any and all comments will be gladly accepted and much appreciated...

Thanks to all for all the previous help and input on this great forum...

Very best to all, keep well....

Keith Christchurch, New Zealand