Attn: GM Not really an MLTL and not really a BR home for a 167e

[loninappleton]

Hello to all. The winter was occupied with a variety of distractions. But as soon as I can open a window I think about speaker building again. I want to try my hand at a small fonken for thr FE127e.

But the large cabinet GM gave for my 167e got to be too much for me to move esp. with the port on the bottom.

All this brings me to the present subject:

The MLTL box is cut down to 11 1/4 (w) x 11 in (d) and now 23 3/4 high all inside dimensions.

The FE 167e is close to center 9 1/2 down from top.

Could someone run these dims through the calculations for closed box and ported? The original design which was 3 ft long was made from standard shelf material of glued up butcher block style boards from the hardware store.

Please say if I should just seal it up or install a port. The port used for the larger box was 4 in PVC about 2 in long.

My inspiration for making this change was Bob Brines stand mounted MLTL speaker for the 167e. The dimensions won't be the same. It's for temporary use.

WinISD gives a vent length of 0.102m diameter and 0.276m. length for the 167e. As I recall, I entered the data into WinISD myself from the data sheet. I'll have to use a meter to inches converter for this to make sense. And then find a length of PVC for it.

Or not if sealed is a recommendation.

Please advise on getting this quick fix together. At least I can move this one without rupturing something.

[loninappleton]

A quick trip to the meter/inch conversion program gave 4" nominal diameter (4.01574)

and 10.8661 inches for length! That's almost as deep as the box.

[doorman]

As an aside, have you considered the 167 floorstanders al la P-10?
I've recently done a pair, they're breaking in now.
I've had and heard the 167's in several different enclosures, these are very satisfying, and a fun build too!
Best, Don

[rjbond3rd]

Hi Lon! Long time no see. I had been wondering where you were.

1. Your cab will in fact be an MLTL because of the "tall" dimension. It just won't be tuned as low as it was before, and it sounds like it now has a smaller box volume than GM worked out.

2. WinISD will definitely tell you the response of sealed vs. ported, and give you the port length. This is one of those cases where WinISD can do the job (except for BSC), so you're already half-way there.

3. Otherwise, since the box is built, and the only variable is port length, why not get various lengths of PVC and tune the box manually? It's fun to do -- once, anyway! I would use the free Marchand test-tone (function) generator here: Marchand Electronics: Sound card Function Generator, Real Time Analyzer, Audio Oscillator, Calculator, free download

A short length will tune the box high, a longer length lowers the tuning. You have to use low SPL obviously. I'd start with no port, then experiment with different lengths and stuffing. It's easy to find the resonant frequency for a given length of PVC (the cone will have minimum excursion, the port will sort of howl and the box will vibrate),. Of course, you'd have to just use your ears as to what ultimately yields a flat response, but this is how I'd tune a box on a desert island.

[rjbond3rd]

Lon, use a PVC 90-degree elbow if you want 10" length, or just use two ports.

[PeteMcK]

In WINISD if you click on the units name beside the field you're looking at, it will convert from metric to colonial units....

FWIW, Winisd gives me 1.25" port length for a 2" dia port, tuning 51Hz

[loninappleton]

Thanks to all those who responded so far.

Pete McK,

I trust anybody's calculations more than mine. If WinISD is reporting this more normal port dimension all the better. I doubt if a 10 inch port is needed for my purposes and esp volume levels which are low.

RjBond,

I have used the Marchand when first building for the 167e. It appears that port diameter may not be what WinISD gave me. It's been a long time since I put in the 167e specs. So if someone can check me out on that, all the better.

As to a floor stander, for now I want to get away from things that are hard to move.

After I get this in between box assembled again, my attention will be on a fonken for Fe127 to use more or less as a radio speaker for audio streams on computer. I listen to most of my news that way.

I have not touched my tools much because I still have the same incredible shop limitations as always.

[loninappleton]

I rummaged through the parts box today and came up with enough 2 in ID PVC to get a port put in this build. Also whacking together a top for the build. The walls are lines with
1/2 in polyfil of the sheet sort found in the fabric store. For the older MLTL, the top back wall and one side are covered. I do not know how rear port placement will change what is needed there.

I've always wanted to experiment with fiberglass 1 in but haven't used that since it came in one of my kits from Speakerlab in the late 70's.

I spent most of the time when making this one on learning to use a router for the circle cuts and filing out the chamfers for the driver (around the t-nuts) by hand. That part of the build finished nicely. So other tweaks can be done now.

Any suggestions on interior treatments for top bottom and/or all sides? I still have removable top and bottom for this one.