The Metronome

[sherpa]

Well i guess that's my first job. i actually lined all 4 sides but i made the bottom removable for access and the ability to change port dimensions easily. It'll be easy to remove the lining on all except the back. Thanks Jim I'll report back when i get that done.

 

[Steve Cresswell]

I would concur with everything Jim says.
My FF225WK Mets are lined top to bottom on the back only.
The top third of the cab is lightly stuffed with Dacron fibre with a
plastic mesh above the driver to prevent the stuffing migrating down the
line.

Bass is phenomenal with the cabs set up like this.
Also Mets are specifically designed to operate near walls, so bringing them out into a room
will cause bass lightness and a mid-forward sound unless BSC is used.

Hope that helps

Steve

 

[sherpa]

That helps a bunch. I'll be removing the lining from the fronts and sides this weekend. Also putting them closer to the wall then i'll play with the stuffing in the top third.
Thank You
Paul

 

[Jim Shearer]

Paul,

I was on my other computer where I have the BSC Excel sheet. Estimated values for BSC:

for 2 dB: 1.7 ohms & 0.5 mH
for 3 dB: 2.7 ohms & 0.7 mH
for 4 dB: 3.8 ohms & 1.1 mH

My best guess would be 2.7 ohms & 0.7 mH, which is in line with what I have on my FE167e Mets.

Keep us posted!

Cheers, Jim

 

[jay53]

Steve,

I was about to order FE206n and Ft17 to build a pair of Metronome Speakers - My first DIY Project. Having chanced upon your posts recommending FF225WK instead, I will now switch to that. Meanwhile if you can share the BSC values or any other information that may be useful, it will be much appreciated.

Jay

 

[Steve Cresswell]

Steve,

I was about to order FE206n and Ft17 to build a pair of Metronome Speakers - My first DIY Project. Having chanced upon your posts recommending FF225WK instead, I will now switch to that. Meanwhile if you can share the BSC values or any other information that may be useful, it will be much appreciated.

Jay

Ok Jay

The cabinet is simply the one in the tables for the FE207. To make the 225 work at its best in this cabinet,
the port dimensions must be changed from 3 x 3 inch (76 x 76 mm) to a 3 inch x 1.5 inch tube (76 x 38mm)

I do not have BSC on my Mets, IMO they don't need it, not with the FF225WK anyhow.

Crossover cap is 0.33uF to the FT17H horn tweeter.

Steve

 

[jay53]

Steve,

Many thanks!

The Drivers are on the way to me.

Jay

 

[hajj]

Concerning the simulation made by Jim for the ff165wk, I had a hunch that the ripple was caused by the Z driver being equal to 1/2 L, so i went and remodeled it using Bob Brines' measurements of the ff165wk, and altered the parameters provided by Jim Shearer for the enclosure using the following:

L= 55 inches
Zdriver= 30 inches
So= 1x5 inches
Sl= 10x9 inches
Rport= 1.5 inches (diameter= 3)
Lport= 2.5 inches
Stuffing density was kept standard at 0.25

And this is the result I got.
I seems to look better than Jim's simulation upfront, by I have a feeling that there's something terribly wrong that i did not account for.
So if anyone could shed some light, please go ahead.
Regards
Nick

 

[Jim Shearer]

That looks nice! Less ripple & F3 is a bit lower.

I had hoped that Scott might comment earlier, as he is much better at this than I am.

One thing that stands out for me is that the Met design is reasonably robust/tolerant. Small changes in dimensions don't result in disastrous loss of performance.

Cheers, Jim

 

[Lefty78]

On the issue if TQWT:
Would the B&W Emphasis be considered an inverted and folded metronome?
It appears to be a tapered cone with a port in the mouth.
Trying to understand the terminology and see how it can be translated into a very aesthetically pleasing design.

 

[GM]

Hmm, it does appear to be a flared vent, offset driver, TL of sorts, but the driver filter chamber makes it more of a funky BLH than the Metronome's simple vented pipe horn.

GM

 

[chrisb]

Hmm, it does appear to be a flared vent, offset driver, TL of sorts, but the driver filter chamber makes it more of a funky BLH than the Metronome's simple vented pipe horn.

GM

some of those funkier B&W designs kinda make ya wonder whether a group of them drank the bong water after the staff Christmas party

 

[vinylkid58]

some of those funkier B&W designs kinda make ya wonder whether a group of them drank the bong water after the staff Christmas party

With a bit of acid thrown in for good measure.

jeff

 

[NotWisely]

i [sadly unemployed for the moment] managed to score a sheet of nice birch from a buddy's cabinet shop scrap bin.

i had to have a pair of these. the only drivers i had handy were the Tang Band w4-1052sdf

i know the enclosure is not optimal for this driver, but i could not wait and ripped a pair out using the 4" recommended design.

they sound amazing...mostly. i have no bsc but a little EQ in foobar and they are really pleasing to me.

my real issue comes from a strange harmonic vibration at the top of the enclosure...a buzzing sound. not really sure how to correct this without destroying the enclosure to dampen that area more or add bracing. any ideas? the resonance occurs in the upper range of some male vocals.

and yes i will re-stain them. wife is deciding on that soon. please forgive my noobish construction and crappy camera phone.

 

[hajj]

ff165wk construction

So, after running all the sims over and over again for the ff165wk, I had mustered enough courage to actually build the enclosure (or to be more precise, have the enclosure built by a professional carpenter).
Below are some pics of the build during dry fitting just to get a peak at what it'll look like.
I ended up redesigning the feet, giving them a more "modern" look that'll better go with my listening room.
The enclosures are made out of 18mm marine plywood, CNC cut down to 1/10mm precision.
As you can see on the leg closeup, I made a design mistakes and did not account for the plywood thickness when drawing the side panels, which left me with a step from front panel to side panel at the leg level.... well you live and learn.
Paint should be done by tuesday, will post more pics then...
Regards
Nick

P.S: sorry for the bad pic quality, but there's only so much one can do with a crappy phone camera...

 

[hajj]

Here they are, finished and singing...

I ended up lining the inside of the back panel with acoustic foam from top to bottom, and am now in the process of voicing them by adjusting the stuffing in the upper part of the line (above the driver).

So far, they image like no speaker I've ever heard before!
Another thing is that they definitely need a BSC filter, but i'll do that once i'm finished with the break in (30 hours down, another hundred hours or so to go...) and once i get my measurement rig up and running

The ff165wk are very smooth drivers compared to the usual full ranger i'm used to and i can't say they're lacking in the upper registers....
I'm a happy happy metronome owner.

Thanks Dave, Scott and Steve...

back to my music

 

[Steve Cresswell]

Glad you like them!

Those asymmetric base arches look cool

Steve

 

[hajj]

Thanks,
I wanted something that would be easier to do and does not require a router, so this design was the best fit, the cool factor was just a lucky coincidence

Glad you like them!

Those asymmetric base arches look cool

Steve

 

[Corvus corax]

I've read through most of this thread with great interest- Back in the 320-ish post, there were some numbers posted for a 15 inch coax driver that is somewhat similar to a pair of woofers I have on hand- the Faital 15PR400- similar Fs at 35 Hz, but different Qts, at .30. I was going to throw them into a standard reflex enclosure, but that's boring- I think these would be great in a ML-QQWT. They aren't full range woofers, but with good response to 4K, they will reach well up to my paper horns…

Can anyone help with a set of numbers for these?

Actually, just checked back- it was post 206… For a PAudio BM15CX38. I could just try and drop these in…

 

[GM]

It would be a bit undersized to my way of thinking and need a 3" long vent for a similar response, so consider a ~432.76"^2 base area, ~1.5" long vent and driver down ~39.88".

GM