Yes, Fs is actually a little lower using Mms, Cms, though it's all academic since your drivers will measure differently, hence my suggestion to oversize the cab a bit.
Given my druthers, I'd make it 84" i.d. with a ~404.86"^2 i.d. base area, 10" dia. x 0.75" reflex vent, driver down at 42" and put any super tweeter below it.
Sims are minimally damped:
GM
Given my druthers, I'd make it 84" i.d. with a ~404.86"^2 i.d. base area, 10" dia. x 0.75" reflex vent, driver down at 42" and put any super tweeter below it.
Sims are minimally damped:
GM
Attachments
Correct. The longer path-length increases loading on the vent, i.e. better damped as noted in the lack of a 'saddle' in the ~45-135 Hz BW [slightly under-damped] and 10" dia. Vs 8" dia. vent. Ideally we want the vent area [Av] to = Sd = ~12.61" dia., but it would be long enough to require folding it, which would be a lot of extra work for a relatively minor amount of increased damping that can be done by increasing damping at the closed end.
GM
GM
Well, I've started building them. I'm making the cabinets out of 3 layers of birch plywood, haven't decided how I'm going to finish them yet. The front and rear panels are cut, The sides will be done in the next week or so. So far, I'm 6 sheets of plywood in, with 4 to go, so definitely not a lightweight enclosure. Wall thickness is 1.25 inches with the damping layers. I'll have some pics soon- as soon as the epoxy vacuum impregnation is finished. There's no point in making them, unless we make them ridiculous…
FF125WK anyone?
It must be 18-20 months ago that I build a pair Metronomes with the Tang Band 4" bamboo drivers. Have been battling leukemia during this time (rare form, incurable) but want to make another pair before I am unable to do any more building.
I had hoped to buy some FE127E drivers but waited too long and now they are gone.
I want now to use the FF125WK using the FE127E plans. I suspect the driver can stay in the same location but it is highly likely the port will need adjusting. Is there a kind soul who is able to plug the specs (attached) into their spreadsheet and post the results?
Many thanks in advance, Marinus
It must be 18-20 months ago that I build a pair Metronomes with the Tang Band 4" bamboo drivers. Have been battling leukemia during this time (rare form, incurable) but want to make another pair before I am unable to do any more building.
I had hoped to buy some FE127E drivers but waited too long and now they are gone.
I want now to use the FF125WK using the FE127E plans. I suspect the driver can stay in the same location but it is highly likely the port will need adjusting. Is there a kind soul who is able to plug the specs (attached) into their spreadsheet and post the results?
Many thanks in advance, Marinus
Attachments
Last edited:
don't fret the wait - I doubt the 125WK will disappoint - I've tried them in at least 2 enclosures, and as much as I got used to the127 (warts and all) over a period of at least 6 years, don't miss it at all
I'd imagine the number crunchers shouldn't take too long to answer the question re adjustments to enclosure design / ports, etc
and terribly sorry to hear about the health issue
I'd imagine the number crunchers shouldn't take too long to answer the question re adjustments to enclosure design / ports, etc
and terribly sorry to hear about the health issue
Thank you for the information that the FF125WK will work, that is very usefull to know. Another driver that I can still get is the FE126En but I do not think it is as suitable.
( I also had a brief moment of considering the FF105WK and even the FE108 Sigma but seeing that a number of those who build the metronome with the smaller drivers later rebuilt using larger drivers. I feel the FF125WK is a happy compromise between size and SPL levels - at least in my smaller room )
( I also had a brief moment of considering the FF105WK and even the FE108 Sigma but seeing that a number of those who build the metronome with the smaller drivers later rebuilt using larger drivers. I feel the FF125WK is a happy compromise between size and SPL levels - at least in my smaller room )
I have built Mets withFE108eSigma, F120A, and FE167e. All are very nice and I think you would be pleased with any of them.
That said, the F120A is my favorite--smoothest, best high freq and good enough low freq that I don't feel the need for a subwoofer; however, this driver doesn't sound good with direct coupled SS amps--the high freqs just die; with tubes it makes sweet, sweet music.
The FE108eS has great mids & highs, but the lows are limited enough that I like to use a sub with it.
The FE167e plays louder & sounds bigger with more authoritative bass. It gives up a bit of sound quality in the mids & highs, but is over-all quite pleasing.
I ran MJK MathCAD models of the FF125wk Met using the dimensions for the FE127e. It does work, but can be improved with a little tweaking. AFAIK there is no single, absolute solution for cabinet dimensions--there is always some wiggle room. The dimensions I settled on look OK to me, but someone else may find a slightly better solution.
I decreased the internal volume a bit, increased the length of the port, and increased Zd by 2". Changing Zd resulted in a bit less ripple in the SPL plot, but leaving Zd at 20" works OK--the ripple is then about what it is in the Mets I have built. So you can choose between higher driver placement and a little less ripple in the response.
Plotted response is for enclosure dimensions:
L= 48"
So= 2 x 2"
Sl= 7 x 5"
Zd= 22"
port: D=2", L=3"
That said, the F120A is my favorite--smoothest, best high freq and good enough low freq that I don't feel the need for a subwoofer; however, this driver doesn't sound good with direct coupled SS amps--the high freqs just die; with tubes it makes sweet, sweet music.
The FE108eS has great mids & highs, but the lows are limited enough that I like to use a sub with it.
The FE167e plays louder & sounds bigger with more authoritative bass. It gives up a bit of sound quality in the mids & highs, but is over-all quite pleasing.
I ran MJK MathCAD models of the FF125wk Met using the dimensions for the FE127e. It does work, but can be improved with a little tweaking. AFAIK there is no single, absolute solution for cabinet dimensions--there is always some wiggle room. The dimensions I settled on look OK to me, but someone else may find a slightly better solution.
I decreased the internal volume a bit, increased the length of the port, and increased Zd by 2". Changing Zd resulted in a bit less ripple in the SPL plot, but leaving Zd at 20" works OK--the ripple is then about what it is in the Mets I have built. So you can choose between higher driver placement and a little less ripple in the response.
Plotted response is for enclosure dimensions:
L= 48"
So= 2 x 2"
Sl= 7 x 5"
Zd= 22"
port: D=2", L=3"
Attachments
Jim, many thanks for these dimensions - I will go with the increased Zd.
Just to make sure that I am going to get the damping right: from reading the posts I gather you only line the back wall with 0.5" undercarpet and have some acoustic fluff above the drive if needed?
PS: How did you manage to get the F120A in there when looking at the large back?
Just to make sure that I am going to get the damping right: from reading the posts I gather you only line the back wall with 0.5" undercarpet and have some acoustic fluff above the drive if needed?
PS: How did you manage to get the F120A in there when looking at the large back?
Last edited:
Most welcome!
In the FE108eS and FE167e builds I used foam from Parts Express to line only the back. On the F120A, I put foam from just above the driver down to the bottom, then PE Acousta-Stuff fiber in the top.
The F120A was built to dimensions I calculated, not the ones in the table for the FE127e, so there was no trouble fitting the driver in. Which does bring up the point: I didn't draw out a plan for the dimensions I gave you. They look like there shouldn't be any problem with driver depth, but it might be a good idea to draw it up and check. I think you need to do that anyway, as you need to know how the 'bottom section' (arched legs) adds to the pieces.
And Now:
At the risk of being repetitious--this is a huge thread and I’m sure there must be folks coming in recently who haven’t slogged through every page...
If this is your first Met build, let me make a couple more points:
--Use foam lining on the back only. In my first Met, I mistakenly lined all four sides--which totally killed the sound.
--I use BSC on my FE108eS and FE167e Mets. The F120A doesn’t need it. IME, whether you need BSC and how much depends on the driver, your amp and your room.
--You might consider making the port baffle removable so you can make adjustments--like putting the BSC inside.
After you have about 200 hrs on the drivers, you should be able to determine if BSC would be helpful. If you want to try BSC on your FF125wk Met, my best guess is 0.6 mH inductor and 3 ohm resistor.
My approach is to start with an adjustable BSC (thanks to MJK): the inductor with an L-pad to change the resistance. Find the setting you like best, then measure the resistance. This saves buying multiple, expensive resistors, but if you aren’t making multiple builds, then the cost of the L-pads may be prohibitive.
Suggested BSC parts for use with the FF125wk:
0.60mH 18 AWG Perfect Layer Inductor 266-818
Mills 3 Ohm 12W Non-Inductive Resistor 005-3
foams I have used:
Acoustic Foam 1-1/2" x 24" x 18" UL 94 260-516
Sonic Barrier 1/2" Acoustic Foam w/PSA 18" x 24" 260-520
Keep us posted on your progress. And, as always: pictures, or it didn’t happen!
Cheers, Jim
Jim, thank you for the explanation. I've build speakers in the past and I always first go through all the documentation before asking questions. (I have gone through the whole thread and did some more searching).
Now I have come up with one more question: You've had more than just the FE127E but what is your impression on the longevity of the new foam surrounds on the newer drivers and on the FX120 / F120A? I have bad experiences in the past with foam and do not want to build something that in 5 years I (-or more likely- my family) can throw away because the foam is falling apart.
I might go for the FX120 if the surround is having a longer longevity than the FF125WK or I might see if I can still find some FE127E's. (in fact I've just written away to someone in Asia for how many they've left and shipping costs, not getting my hopes up though). The F120A is outside my pricerange but (as we say here) push comes to shove then I will go to the FE108Sigma if that is having the potential for being operable the longest.
Thanks.
Now I have come up with one more question: You've had more than just the FE127E but what is your impression on the longevity of the new foam surrounds on the newer drivers and on the FX120 / F120A? I have bad experiences in the past with foam and do not want to build something that in 5 years I (-or more likely- my family) can throw away because the foam is falling apart.
I might go for the FX120 if the surround is having a longer longevity than the FF125WK or I might see if I can still find some FE127E's. (in fact I've just written away to someone in Asia for how many they've left and shipping costs, not getting my hopes up though). The F120A is outside my pricerange but (as we say here) push comes to shove then I will go to the FE108Sigma if that is having the potential for being operable the longest.
Thanks.
I really don't know about the life span of the foam surrounds. My FE108eS are now 6 years old and the F120A are 4 years old; both seem fine.
The life span is likely affected by local air quality. When I lived in the Philadelphia area, high sulfur and ozone levels caused numerous problems: silver tarnished in a matter of days; rubber products had rather shorter than expected lives, becoming hard & brittle. Air quality in upstate New York is better, but not as good as I might like. You may be better off in NZ.
I'm not sure, but IIRC, the FX120 should do well in place of the F120A. Both drivers seem to like a little more box volume than the FE127e. However, I did run a model of the FE127e in the Met I designed for the F120A: the model looked very good. Again, this indicates to me that the Met design isn't extremely critical about precise dimensions.
Cheers, Jim
The life span is likely affected by local air quality. When I lived in the Philadelphia area, high sulfur and ozone levels caused numerous problems: silver tarnished in a matter of days; rubber products had rather shorter than expected lives, becoming hard & brittle. Air quality in upstate New York is better, but not as good as I might like. You may be better off in NZ.
I'm not sure, but IIRC, the FX120 should do well in place of the F120A. Both drivers seem to like a little more box volume than the FE127e. However, I did run a model of the FE127e in the Met I designed for the F120A: the model looked very good. Again, this indicates to me that the Met design isn't extremely critical about precise dimensions.
Cheers, Jim
Many thanks to all who chirped in about the foam.
With Dave (whose opinion I respect highly) having mentioned that the FF125WK has eclipped the older designs it now becomes a no-brainer.
Perhaps there is a way to store these drivers so that the surround does not deteriorate and then I'll buy four instead and put two in storage.
With Dave (whose opinion I respect highly) having mentioned that the FF125WK has eclipped the older designs it now becomes a no-brainer.
Perhaps there is a way to store these drivers so that the surround does not deteriorate and then I'll buy four instead and put two in storage.
Don't we know it here down under with the ozone layer disappearing over summer (in other words: the ozone hole over the antarctic growing so large over summer that it encompasses New Zealand). That's why paints get tested in our country first..... (outside of course)
PS how much ply is required for a pair?
Last edited: