Dave/Scott
The 168 sigma driver has a depth of 4". My crude maths suggest this won't fit the dimms listed in the table as Si 10" by 6'' and So 2.5" by 1".
For the side panel I need to loose 5" and at the half way point for the driver the depth will be 6" - (5"/2) = 3.5".
There won't be much room to sit the driver either which has a diameter of 7.5", and I need to loose 7.5" in the taper, so at the mid point I will have 10" - (7.5"/2) = 6.25"
Are my maths flawed, would a supra baffle be the way to go? Does it looks a very tight fit for the driver to "breathe"?
Cheers
The 168 sigma driver has a depth of 4". My crude maths suggest this won't fit the dimms listed in the table as Si 10" by 6'' and So 2.5" by 1".
For the side panel I need to loose 5" and at the half way point for the driver the depth will be 6" - (5"/2) = 3.5".
There won't be much room to sit the driver either which has a diameter of 7.5", and I need to loose 7.5" in the taper, so at the mid point I will have 10" - (7.5"/2) = 6.25"
Are my maths flawed, would a supra baffle be the way to go? Does it looks a very tight fit for the driver to "breathe"?
Cheers
Scottmoose said:
A supraBaffle is recommended, and as much to give a little less restriction in the line as to help push baffle-step down.
In the case of the existing suggested dims it is a case of just fits... you could change the base dimensions to 12x5 and get a bit more sideways room.
dave
Attachments
How's that for a tight fit? 
FWIW, for those of you guys who aren't sure about baffle-step, and want a quick ROT to determine the point at which it occurs, take it as 11,600 / width of the baffle at driver-height in cm. Alternatively, if you're like me (God forbid ) & prefer working with the Imperial system, then 4560 / width of the baffle at driver height in inches. Tapered baffles affect this slightly, but it's a useful guide. If you have a technical turn of mind & want to explore the subject in greater detail, Dave has loads of further information on this subject (& numerous others) on one of his sites: http://www.t-linespeakers.org/tech/bafflestep/intro-bds.html
FWIW, for those of you guys who aren't sure about baffle-step, and want a quick ROT to determine the point at which it occurs, take it as 11,600 / width of the baffle at driver-height in cm. Alternatively, if you're like me (God forbid
) & prefer working with the Imperial system, then 4560 / width of the baffle at driver height in inches. Tapered baffles affect this slightly, but it's a useful guide. If you have a technical turn of mind & want to explore the subject in greater detail, Dave has loads of further information on this subject (& numerous others) on one of his sites: http://www.t-linespeakers.org/tech/bafflestep/intro-bds.html
Scott,
Speaking of baffle step, that and/or edge diffraction work strangely with these. I have very sharp 90deg edges on mine with no supra-baffle, and they sound fairly balanced even out in the room. I taped some 34mm thick pieces with 45deg bevelled front and rear edges to the sides at driver level, expecting a fuller sound. Instead I got a much much more uptilted response. "Unlistenable" as Dave would say, not subtle at all.
This is one of the things on my long list of things I want to explore further with measurements. Either edge diffraction effects can be quite directional, making 90deg edges favorable at times. OR such narrow cabs can push baffle step up to such a high frequency that it becomes less of an issue. OR there's a problem with 45deg bevels with such a narrow cab and the pressures are high enough that the secondary diffraction at the 2nd 45deg bend to the side becomes problematic.
Speaking of baffle step, that and/or edge diffraction work strangely with these. I have very sharp 90deg edges on mine with no supra-baffle, and they sound fairly balanced even out in the room. I taped some 34mm thick pieces with 45deg bevelled front and rear edges to the sides at driver level, expecting a fuller sound. Instead I got a much much more uptilted response. "Unlistenable" as Dave would say, not subtle at all.
This is one of the things on my long list of things I want to explore further with measurements. Either edge diffraction effects can be quite directional, making 90deg edges favorable at times. OR such narrow cabs can push baffle step up to such a high frequency that it becomes less of an issue. OR there's a problem with 45deg bevels with such a narrow cab and the pressures are high enough that the secondary diffraction at the 2nd 45deg bend to the side becomes problematic.
Now that I find fascinating. Confirms the sort of effect different shapes can have on step-response & diffraction. We went max-flat on most of these in an effort to avoid needing circuits, it appears with some success, according to most builders thus far. So clearly the baffle shape & the angles are also playing a role here too. I remember TC postulating that his oblete spheroid baffles helped create the large soundstage his speakers were justly famous for -I wonder if the shape of the Metronome has a similar effect, albeit for somewhat different reasons?
I've heard Steve's original 108ESgima cabinets several times now, and each time I've been astounded at their imaging -with a live Loreena McKennitt CD Steve & I could literally walk around the soundstage, left-right, front-back, and plenty in the vertical domain too. I'll be very interested in your measurements when you are able to test them.
Regards
Scott
I've heard Steve's original 108ESgima cabinets several times now, and each time I've been astounded at their imaging -with a live Loreena McKennitt CD Steve & I could literally walk around the soundstage, left-right, front-back, and plenty in the vertical domain too. I'll be very interested in your measurements when you are able to test them.
Regards
Scott
planet10 said:
Ok, so I've been following this for awhile, and reading theory, etc.
Is there any good reason you couldn't fold this in half to save on height? For me, WAF is strongly influenced in a negative direction by the height of the speakers...
I call it, the metrofold, based on the original drawing simply because that one had dimensions. Chop a metronome in half, put the top half upside-down in front, do a roundover on top (or 2x 45 degrees for ease), tweak the line length, and voila, a half height metronome!
Am I missing something obvious?
*edit*
or chop it off higher, and fold it behind, just to save on headspace?
Attachments
klocwerk said:
Works with the original, with the rest that have the driver off-set at 50% you'd have to get a bit creative.... In the original you also have a driver that is 15-17" off the ground depending on how you fiddle it.
Mileva is essentially a folded variation (althou the taper is only 1st order instead of 2nd order to dramatically ease the woodwork)
dave
Having recently completed a pair in cardboard and packing tape, my wife's reaction was something along the lines of "They look really cool too".
While they are somewhat tall, they are narrow in width and depth and do not have the overpowering look that a backhorn or a regular 2 way floorstander has. At least not if you are using small drivers.
And don't laugh at the cardboard, it works, it got me started, they sound pretty good and it cost almost nothing. I only had to buy one item to build them, a roll of packing tape. Everything else I had on hand. No midnight trips to Home Depot.
My favorite tuning of the Metronome with 108's
One thing that hasn't been discussed, an a primary reason I don't have a lot of faith in modelling this enclosure is how the driver creates a big blockage related to the airspace above. This is especially true using the FE108's. It seems that it would create something similar to a double BR effect, at least for a portion of the drivers' rear output.
My little 108's put out a surprising amount of bass in this simple handsome cab, and the reason I bring this up is the tuning I settled on with placement out 2-3ft from the wall with no BSC, includes a little polyfill in the bottom vent, a little polyfill above the driver, and a piece of fairly 3/8" rigid foam (similar to cork in rigidity and resistance to compression) wedged in behind the driver. The piece of foam is a about 4" wider than the interior width, so it wedges in covering much of both sides and the back. The primary intent was to reduce reflections back to the cone, but between it and the large magnet, there's not a lot of open CSA at the driver and it helped bring bass tuning in line as long as I don't get them too close to the wall where they get boomy.
One thing that hasn't been discussed, an a primary reason I don't have a lot of faith in modelling this enclosure is how the driver creates a big blockage related to the airspace above. This is especially true using the FE108's. It seems that it would create something similar to a double BR effect, at least for a portion of the drivers' rear output.
My little 108's put out a surprising amount of bass in this simple handsome cab, and the reason I bring this up is the tuning I settled on with placement out 2-3ft from the wall with no BSC, includes a little polyfill in the bottom vent, a little polyfill above the driver, and a piece of fairly 3/8" rigid foam (similar to cork in rigidity and resistance to compression) wedged in behind the driver. The piece of foam is a about 4" wider than the interior width, so it wedges in covering much of both sides and the back. The primary intent was to reduce reflections back to the cone, but between it and the large magnet, there's not a lot of open CSA at the driver and it helped bring bass tuning in line as long as I don't get them too close to the wall where they get boomy.
Hi John
Mine rest on a carpeted floor and are placed about 3 inches from the rear wall with curtains behind them. There is a lot of absorbtion in the vicinity. They are toed in by about 10 degrees and don't sound boomy. The cabinets are lined with rubber carpet underlayment of the kind that has a rippled surface and have no other acoustic treatment in them
I built a pair of 108EZ cabs for a female friend of mine but with a slight change to the top CSA which on hers is 2 X 3 inches internally instead of 1 X 3. This was done because she thought they looked "too pointy" at the top, not for any engineering reason. The taper rate is going to be therefore a bit less and there is a bit more room for the air at the top to get past the driver.
It turns out that these cabinets sound slightly better than the originals and are very even from top down to bass cutoff. Again they can be pushed right up to her rear wall without boom.
The reason ours don't boom close to walls might simply be down to the fact that some of us Brits like filling our rooms with carpets, rugs and soft furnishings.
Dave has mentioned that he wants to experiment with aspect ratios and the free area behind the driver might be something to play about with. Thanks for the information.
Steve.
Mine rest on a carpeted floor and are placed about 3 inches from the rear wall with curtains behind them. There is a lot of absorbtion in the vicinity. They are toed in by about 10 degrees and don't sound boomy. The cabinets are lined with rubber carpet underlayment of the kind that has a rippled surface and have no other acoustic treatment in them
I built a pair of 108EZ cabs for a female friend of mine but with a slight change to the top CSA which on hers is 2 X 3 inches internally instead of 1 X 3. This was done because she thought they looked "too pointy" at the top, not for any engineering reason. The taper rate is going to be therefore a bit less and there is a bit more room for the air at the top to get past the driver.
It turns out that these cabinets sound slightly better than the originals and are very even from top down to bass cutoff. Again they can be pushed right up to her rear wall without boom.
The reason ours don't boom close to walls might simply be down to the fact that some of us Brits like filling our rooms with carpets, rugs and soft furnishings.
Dave has mentioned that he wants to experiment with aspect ratios and the free area behind the driver might be something to play about with. Thanks for the information.
Steve.
Driver position in a line varies according to a combination of factors -length, taper, tuning frequency, motor strength etc. So you have to be very careful in taking one position as a blanket 'way to go' unfortunately. That said, you'll note that the vast majority of the ML Metronomes Dave & came up with (including the one for the 168ESigma) use 0.5 line length.
For people with a historical bent, the traditional idea was to put the driver at 1/3 acoustic length of a line (1/3 physical length also being commonly used). The formula used for setting driver position in expanding lines (what was called a Voigt Pipe, inaccurately as it happens, but that's for another day) was:
D = L / 2 + square root of So / Sl
Where D= zdriver, L=line length, So=CSA of the pointed end & Sl=CSA of the wide end. The other way of doing it was taking Sl=2.5Sd, with St (the line CSA where the driver would be positioned) =Sd, and So = whatever CSA you get from the selected line length & the taper the above gave you. It sort of worked, on occasion, but not very often, and their only real use now is for SWAGing an alignment if you've got a driver, but no information about it, and no access to any of the other, more detailed traditional nomographs.
Sorry for going off topic, but it's interesting. Well, I think it is anyway.
For people with a historical bent, the traditional idea was to put the driver at 1/3 acoustic length of a line (1/3 physical length also being commonly used). The formula
D = L / 2 + square root of So / Sl
Where D= zdriver, L=line length, So=CSA of the pointed end & Sl=CSA of the wide end. The other way of doing it was taking Sl=2.5Sd, with St (the line CSA where the driver would be positioned) =Sd, and So = whatever CSA you get from the selected line length & the taper the above gave you. It sort of worked, on occasion, but not very often, and their only real use now is for SWAGing an alignment if you've got a driver, but no information about it, and no access to any of the other, more detailed traditional nomographs.
Sorry for going off topic, but it's interesting. Well, I think it is anyway.
Steve,
I didn't mean anything derogatory. They are easily tuned to taste, within certain obvious limits, and I wanted to be able to get mine as far from the wall as possible without absolutely requiring a sub. Against the wall also put mine close to the corners, and since my walls are concrete, placement has maximum effect. Fully lined with damping mine would probably be quite happy at the wall.
I didn't mean anything derogatory. They are easily tuned to taste, within certain obvious limits, and I wanted to be able to get mine as far from the wall as possible without absolutely requiring a sub. Against the wall also put mine close to the corners, and since my walls are concrete, placement has maximum effect. Fully lined with damping mine would probably be quite happy at the wall.
I doubt Steve took it that way John -he's not the type to take offense.
The boominess could well be partially my fault, because I deliberately set most of the ML Metronome's Dave & I have done to a ~max flat alignment, partially to give a base-line for people to make their own adjustments, and partly in an attempt to provide sufficient gain to obviate the necessity for a BSC circuit when placed near a wall. Sometimes successful, others less so. Part of the joys of DIY, as I reckon we both know. Easier to adjust than the latest boutique speaker though...
The boominess could well be partially my fault, because I deliberately set most of the ML Metronome's Dave & I have done to a ~max flat alignment, partially to give a base-line for people to make their own adjustments, and partly in an attempt to provide sufficient gain to obviate the necessity for a BSC circuit when placed near a wall. Sometimes successful, others less so. Part of the joys of DIY, as I reckon we both know.
Easier to adjust than the latest boutique speaker though...