I was checking the wiki on bracing and Planet10 website. I just do not understand something. Do the vertical braces with holes actually touch and hold/brace the driver's magnet?
I find it difficult to believe they actually touch the magnet. If, I assume, one cannot glue the brace to the magnet, this would be a source if unwanted vibration and noise.
Antonio
I find it difficult to believe they actually touch the magnet. If, I assume, one cannot glue the brace to the magnet, this would be a source if unwanted vibration and noise.
Antonio
GM said:
Actually, my question in the previous post comes from reading the above comment by GM. So, does mass loading/bracing the driver means actually supporting/touching it with the brace? If this is the case, I would be grateful if someone could show some photographs with examples. Thanks
Antonio
Colin said:
Greets!
I'm not familiar with KEF's mounting scheme, but if you look at the audio pioneer's cost no object, as optimum an electro-mechanical designs as they knew how to design based on known physics you'll see that drivers were isolated from the baffles, yet highly coupled to them in that the driver was mounted in a separate cradle that pressed the driver (mass loaded) against a thick, rigid baffle via a thick gasket, i.e., no screw mounting and I assume why rear mounting drivers stayed the norm for decades as the 'bean counters' had the engineers cost cut these designs for mass marketing.
Obviously, mass loading drivers mounted from the front don't benefit as much because the driver is still coupled via its mounting hardware, but they at least act as a high impedance decoupler of sorts, so still well worth the extra construction hassle, especially for wide BW driver mounting. Adding mass via heavy metal mounting rings such as Fostex's brass units is another option, though not as effective as applying clamping pressure, so combining the two seems a good choice, but don't recall ever trying it, so as always YMMV.
GM
A Sanchez said:
Yeah, it would be kind of hard to mass load it otherwise.
Here's HJ's simple, but effective adjustable device: http://melhuish.org/audio/images/press-screw.gif
An elaborate woodworking one for a very heavy driver, it clamps around the motor: http://www.6moons.com/audioreviews/altec/header.gif
I don't know if Dave's is dimensioned to pre-load the driver or you have to use shims. Regardless, some sort of gasket should be used if there's any chance of movement, which in theory there shouldn't be.
GM
A Sanchez said:
yes
If you get the tolerances right you have a reduction in noise & vibration. The brace rigidly couples the driver to the mass of the box (intead of depending solely on a baffle weakened by the big hole cut out of it. With the driver more tightly coupled to the mass of the box, the unwanted energy output of the driver is avaeraged over a larger mass, giving a lower energy density. This allows for greater effectiveness of the inherent damping of the box material and with a lower energy density any box resonancesare much less likely to be excited,
If the driver is rattling against the holey brace then you haven't got the tolerances tight enuff. Easily patched up with some neoprene gasket tape (but not as effective as something solid)
dave
GM vs Jim Griffin's MLTL
I am about to build a MLTL for my Jordans. I want to keep the front baffle the same as Jim's design because I already have the crossovers with built in BSC that were designed for the 7.5" baffle. Jim's design is more narrow and deep with a slightly smaller area and volume:
JG's = 6" x 4.875" (29.25 sq.in.)
JG's = 1404 cu.in.
GM's = 6.97" x 4.31" (30 sq.in.).
GM's = 1442 cu.in.
I plan on including a vertical brace behind the driver. Since this will consume some of the volume, should I increase the depth of the enclosure?
I am about to build a MLTL for my Jordans. I want to keep the front baffle the same as Jim's design because I already have the crossovers with built in BSC that were designed for the 7.5" baffle. Jim's design is more narrow and deep with a slightly smaller area and volume:
JG's = 6" x 4.875" (29.25 sq.in.)
JG's = 1404 cu.in.
GM's = 6.97" x 4.31" (30 sq.in.).
GM's = 1442 cu.in.
I plan on including a vertical brace behind the driver. Since this will consume some of the volume, should I increase the depth of the enclosure?
Re: GM vs Jim Griffin's MLTL
I am doing something similar with my GM 31 MLTL. I kept JG baffle size (7.5') in order to be able to use his xover if I add the G2si. However I worked the numbers myself considering a 7.5' baffle size using 3/4 plywood= 6" x 5" which gives a 30 sq.in. CSA, exactly like GM's original but 7.5 x 6.5 external. People insist so much about not changing the CSA that I prefered to go this way.
I remeber that Jim mentioned that he kept the original CSA but it seems that he in fact did not.
I wonder how much a change of .75 sq.in CSA could change the end result.
Antonio
bluegti said:
I am doing something similar with my GM 31 MLTL. I kept JG baffle size (7.5') in order to be able to use his xover if I add the G2si. However I worked the numbers myself considering a 7.5' baffle size using 3/4 plywood= 6" x 5" which gives a 30 sq.in. CSA, exactly like GM's original but 7.5 x 6.5 external. People insist so much about not changing the CSA that I prefered to go this way.
I remeber that Jim mentioned that he kept the original CSA but it seems that he in fact did not.
I wonder how much a change of .75 sq.in CSA could change the end result.
Antonio
You theoretically want to keep the net Vb to within +/- 5% for the sim to be ~accurate, but the reality is that between our falling hearing acuity down low and the room's effect cab alignment, maintaining the baffle width for a given XO design is far more important than whether the cab is otherwise 'spot on' dimensionally.
That said, it's always best IMO to make it too big, especially if using other than measured specs of your drivers since it's a lot easier to shrink a cab to find the best tuning for the app than feeling the need to enlarge it.
GM
That said, it's always best IMO to make it too big, especially if using other than measured specs of your drivers since it's a lot easier to shrink a cab to find the best tuning for the app than feeling the need to enlarge it.
GM
JG's volume is within 5% of GM's (1404 / 1442 ~= 97%) so based upon GM's comment they are pretty much equivalent.
I'm going to increase the depth by 1/8" so the internal dimensions will be 6" x 5". Imagine that, just what Antonio is using. That makes the volume 1440 - almost identical to GM's specified volume. Then if I lose a little from the brace, I will probably fall somewhere between JG's and GM's.
I'm going to increase the depth by 1/8" so the internal dimensions will be 6" x 5". Imagine that, just what Antonio is using. That makes the volume 1440 - almost identical to GM's specified volume. Then if I lose a little from the brace, I will probably fall somewhere between JG's and GM's.
On MLTL 48 stuffing, again
Hi,
I am new in this forum and in diy audio; I just built a small bass reflex FE103E for learning.
I intend to build now the MLTL 48 Jordan speakers. I read in this forum that a suggested stuffing is fiberglass. However, at least in Italy, there are a lot of discussions about the danger to the health of this material and that it should be avoided, at least in vented cabinet enclosures.
Do you think that it could be replaced by polyurethane foam, which I can easily find here?
Thank you for this great forum
northernsky
Hi,
I am new in this forum and in diy audio; I just built a small bass reflex FE103E for learning.
I intend to build now the MLTL 48 Jordan speakers. I read in this forum that a suggested stuffing is fiberglass. However, at least in Italy, there are a lot of discussions about the danger to the health of this material and that it should be avoided, at least in vented cabinet enclosures.
Do you think that it could be replaced by polyurethane foam, which I can easily find here?
Thank you for this great forum
northernsky
Hi all,
I am about to build the MLTL. This will be my first speaker project and I wanted to use the cheaper FE126x rather than the jordans - first project and all that! I intend building it as per the layout on the jordan site, using birch ply.
So I was going to get the various bits and pieces from madisound. I have 3 questions (no doubt more to follow!):
1. Is the polyester wadding that they sell OK for this design or should I spring for the acousta-stuf wadding?
2. For the jordans they seem to recommend an inductor/resistor in parallel - do I need to do this for the fostex as well? If so, what values of inductor and resistor?
3. Is there any benefit in laminating 2 layers of 18mm together for the front of the cabinet for added stiffness?
Fran
I am about to build the MLTL. This will be my first speaker project and I wanted to use the cheaper FE126x rather than the jordans - first project and all that! I intend building it as per the layout on the jordan site, using birch ply.
So I was going to get the various bits and pieces from madisound. I have 3 questions (no doubt more to follow!):
1. Is the polyester wadding that they sell OK for this design or should I spring for the acousta-stuf wadding?
2. For the jordans they seem to recommend an inductor/resistor in parallel - do I need to do this for the fostex as well? If so, what values of inductor and resistor?
3. Is there any benefit in laminating 2 layers of 18mm together for the front of the cabinet for added stiffness?
Fran
you might want to check on Planet 10's site for an enclosure for the Fostex. I'm more of a "build someone else's design" sort so I can't say for sure, but what I've picked up around here is that most enclosures require a tweak in dimensions for different drivers. I would be surprised if the Jordan and Fostex MLTL's are the same.
Now to answer your questions:
Many people use polyester wadding. I imagine there is some difference, but probably not HUGE.
The inductor and resistor is for Baffle Step Correction (BSC). This is calculated based upon a number of things (size of baffle, driver specs). The Jordan's and Fostex are very different drivers so I'm sure these are different - just don't know what they are.
From what I've gathered from Dave of Planet 10, a holey brace behind the driver coupling it to the back of the enclosure is probably more beneficial than a double-thick front baffle. Actually, the fostex driver's need room to "breath" so having a double thick baffle will make that even harder.
Now to answer your questions:
Many people use polyester wadding. I imagine there is some difference, but probably not HUGE.
The inductor and resistor is for Baffle Step Correction (BSC). This is calculated based upon a number of things (size of baffle, driver specs). The Jordan's and Fostex are very different drivers so I'm sure these are different - just don't know what they are.
From what I've gathered from Dave of Planet 10, a holey brace behind the driver coupling it to the back of the enclosure is probably more beneficial than a double-thick front baffle. Actually, the fostex driver's need room to "breath" so having a double thick baffle will make that even harder.
OK,
thanks for that. The plan I was going to use is this one:
MLTL 48
Its the 48" high one from the jordan site.
Should I make the brace to run vertically or horizontally and should it sit tight against the back of the driver or no?
How would I go about working out what inductor/resistor combo would be needed. Right now I'm trying to get together an order from maidsound so want to get all that kind of stuff in one order.
Many thanks,
Fran
thanks for that. The plan I was going to use is this one:
MLTL 48
Its the 48" high one from the jordan site.
Should I make the brace to run vertically or horizontally and should it sit tight against the back of the driver or no?
How would I go about working out what inductor/resistor combo would be needed. Right now I'm trying to get together an order from maidsound so want to get all that kind of stuff in one order.
Many thanks,
Fran
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