Next - box construction..
1. Why the volume? This was a matter of keeping the volume as small as possible - yet conversly not to small (..strange I know), AND provide a response from 50 Hz to 20 Hz that would effectivly be "flat" given an average domestic setting (..open up a door though and you'll likely loose some "gain" around the 18-25 Hz range). Of course there is no real "average domestic setting" - so its a guess, but it is based on my experience and the experience of others (..modes accepted of course).
It was also a matter of looking at impeadance. Impeadance gives you an intuitive look into several aspects of performance including phase, group delay, velocity/turbulance, and distortion (non-linear and linear). In this case I was particularly looking for as much "resistive" passband as possible from 50 Hz to 20 Hz (while still maintaing the gain and size already mentioned). This tells me a LOT about how current is or is not controling the driver's motion (as opposed to back emf near a resonance), and in turn this tells me a lot about non-linear distortion. With respect to the "not to small" volume - this is a matter having enough volume that internal pressure doesn't screw-up the linear decay character too badly (..and this is why Scan Speak went to great lengths to use as little "stuffing" as possible in your tweeter and still keep reflections and pressure off of the rear of the diaphram). This is one area where a non-aligned bass-reflex displays a superior character over a small volume normal sealed design (..and its why wilson audio still uses this technique for the "watt" - though they would likely be better off with an aperiodic vent).
2. We desire a low friction internal cabinet. Stuffing, IF using any at all, must be **VERY** carefully controlled with respect to placement in box. Though perhaps Martin Colloms didn't realize it when he originally suggested it - he mentioned that you should keep stuffing well away from cabinet walls. The reason of course is air-flow resistance or "drag". You want that cone motion to be as unimpeaded as possible mechanically (except of course for its own mechanical "suspension" behaviour). This of course coincides with box volume and internal pressurization. Now this is normally of greatest importance from 500 Hz to 5kHz, BUT it is almost as important at the lowest freq.s as well - especially considering that most of the recording at very low freq.s is either direct sound sideband decay, OR in-direct ambiant decay from room boundries (real or virtual) - a.k.a. "hall sound". (Of course along with this "theme" are also things like lower mass drivers with high force.) I suppose then that the best material from purely a "friction" standpoint then would be a polished ultra high density plastic skin on the internal walls, but it isn't just about friction..
3. We desire a low reflection internal cabinet. Unfortunetly this is almost diametrically opposed to # 2 from a construction viewpoint. Here we have problems from any reflective surface, including the driver's frame. The higher the driver's mass for a given surface area - the less problem (..but also the less able it is to produce ambiant decay). This is where I like the space shuttle stuff - i.e. the silicone borscilate additive, (that I provided a link to), to a lossy absorptive paint like latex primer (..note: the cheaper the latex primer the better). This is actually a broad-band absoptive material - unlike most materials. It however is no where near as good as a long fiber "batting" - and this is where you might want to experiment with some batting well away from walls and the driver. These resrictions then suggest that the stuffing (if used) should be placed behind the magnet (but not close to it). Of course the silicone borscilate paint (on walls) doesn't just reduce reflections..
4. We desire a dampened cabinet. That same space shuttle derived paint (applied thickly) reduces sound transmission from the internal cabint to the walls, and also from the walls to the internal cabinet (..the little ceramic "beads" are after all vacuums at their center). Additionally, it marginally reduces (dampenes) vibration of the cabinet walls themselves. However, MUCH more attention needs to be "paid" here. The worst offense here is NOT cabinet walls contributing to the overall spl. No, the real offender is vibration transmitted back to the frame of the driver. (..and this adds all manner of distortion - yes, measurable distortion.) This however is not meant to "downplay" the importance of supressing spl contribution (particularly high level modes) from the cabinet walls, instead it is mentioned so that we can place the greater emphasis where it is needed. Of course this doesn't mean that the method of dampening need not be complimentary to both problems (..and in fact other problems as well). So then..
The standard thick wall braced construction does substantially reduce sound transmission from the cabinet walls - BUT it doesn't do much at all for vibration reaching the driver's frame. We could use a multi-sectioned mult-material laminated approach (i.e. constrained layer) - but d@mn, thats a LOT of work and I'm personally FAR to lazy to have tried something like that (..and besides it doesn't help out a great deal with another problem I'll suggest latter). So then lets "break-down" how the constrained layer is most effective to our two problems. One, the layers with multi-materials are converting vibration into heat. Two, the connection between internal transmission and driver mounting are seperated by several layers - i.e. sound hits the internal panel and then it must make its way to the outer "skin" layer that is conneceted to the driver's frame. OK then, at a minimum we need 2 "skins" - i.e. one internal wall(s) and one external wall(s) or basically a box within a box. We also want a lossy material in-between the two to convert vibration into heat. Furthermore we would like a fair bit of distance between the two walls to make-up for our lack of multi-layers.
So then - box within box construction and a LOT of lossy material in-between the 2 boxes. What material? The same stuff you snuff-out that nasty habit of yours - ultra fine sand. (..And don't use anything but that super fine white sand.) The amount of space? An inch to an inch and a half for the bottom partition. 4 inches every where else (..yes, that much - do NOT reduce this, I've tried several versions - particularly to reduce the top, and it is a *bad* idea), you could however increase this. Now this does pose a few problems the first time I tried it:
A. Depending on the shape of the box and the thickness of the panels this "bulges" the panels outward (and inward as the case may be).
B. Then you have the problem of the driver and port and sand leaking out (..and frankly my powers of description will be the biggest "obstacle" here).
Some assembly (required) and materials, and a LOT of planning..
Well one of the strange things here is that it is better to use panels that are less thick rather than more thick - think 3/4 inch (or as close to it "metrically" as possible). Consider that it is usually cheaper, weighs less, and takes up less space (than the full inch variety) - unfortunetly it also is less structurally rigid and could "bulge" to the point of busting (depending on the quality of wood or mdf). Thats OK though, will will use some "bracing" here but it won't be conventional bracing - in fact it will be a LOT easier than conventional bracing (..though perhaps more "tedious"). Think frankenstien's monster - specifically via the use of numerous "bolts" coupling the 2 boxes together on every panel BUT the bottom panels. This raises a design point here - the bottom panel will be our "fill" panel (i.e. it will be the panel we have acces to to fill the air-space). I'll get back to this in a moment. Anyway, the bolts can either have the head on the outside of the cabinet with the nut on the inside (or the converse) - I'd ***strongly*** suggest them on the outside. You'll need multiple bolts that:
A. Span the 4 inch distance + the amount required for the panels.
B. Have a head and a very thin LARGE diameter steel washer and LARGE diameter compliant (paper) washer that when combined and tightened down is no more than 2/3rds the thickness of the 3/4 inch wall. (i.e. we are countersinking the bolt and washers here so that it doesn't extend beyond the surface of the panel.)
C. Have threads that span their entire length (at least for the "top" panel bolts)
I personally just browse my local hardware store with a tape measure and picked up about 40 (in combination) of what looked best. I think the large washer's were at least an inch in diameter. Then went over a few isles and found a forstner bit for my hand-held drill that matched/slightly exceeded the diameter of the large washers. (..I already had the bits for the bolt's diameter). Of course it wasn't just the bolt and those two washers.. In order, this was the connection (for all box panels but the bottom 2):
Side panels:
A. Bolt Head, B. Steel washer, C. Paper washer, E. Exterior panel, F. Air space (to be filled with sand), G. Interior panel, H. **Felt** washer, I. Steel washer, J. "Tightning" cut-washer, K. Nut. L. Bolt end.
Top panel:
A. Bolt Head, B. Steel washer, C. Paper washer, D. Exterior panel, E. Felt washer, F. Steel washer, G. "Tightening" cut-washer, H. Nut, I. Air space (to be filled with sand), J. Nut, K. "Tightening" cut-washer, L. Steel washer, M. **Felt** washer, N. Interior panel, O. **Felt** washer, P. Steel washer, Q. "Tightening" cut-washer, R. Nut, S. Bolt end.
The reason for the difference here is that the top panel will need the extra nuts and washers to set the interior panel 4 inches away from the exterior panel.
1. Why the volume? This was a matter of keeping the volume as small as possible - yet conversly not to small (..strange I know), AND provide a response from 50 Hz to 20 Hz that would effectivly be "flat" given an average domestic setting (..open up a door though and you'll likely loose some "gain" around the 18-25 Hz range). Of course there is no real "average domestic setting" - so its a guess, but it is based on my experience and the experience of others (..modes accepted of course).
It was also a matter of looking at impeadance. Impeadance gives you an intuitive look into several aspects of performance including phase, group delay, velocity/turbulance, and distortion (non-linear and linear). In this case I was particularly looking for as much "resistive" passband as possible from 50 Hz to 20 Hz (while still maintaing the gain and size already mentioned). This tells me a LOT about how current is or is not controling the driver's motion (as opposed to back emf near a resonance), and in turn this tells me a lot about non-linear distortion. With respect to the "not to small" volume - this is a matter having enough volume that internal pressure doesn't screw-up the linear decay character too badly (..and this is why Scan Speak went to great lengths to use as little "stuffing" as possible in your tweeter and still keep reflections and pressure off of the rear of the diaphram). This is one area where a non-aligned bass-reflex displays a superior character over a small volume normal sealed design (..and its why wilson audio still uses this technique for the "watt" - though they would likely be better off with an aperiodic vent).
2. We desire a low friction internal cabinet. Stuffing, IF using any at all, must be **VERY** carefully controlled with respect to placement in box. Though perhaps Martin Colloms didn't realize it when he originally suggested it - he mentioned that you should keep stuffing well away from cabinet walls. The reason of course is air-flow resistance or "drag". You want that cone motion to be as unimpeaded as possible mechanically (except of course for its own mechanical "suspension" behaviour). This of course coincides with box volume and internal pressurization. Now this is normally of greatest importance from 500 Hz to 5kHz, BUT it is almost as important at the lowest freq.s as well - especially considering that most of the recording at very low freq.s is either direct sound sideband decay, OR in-direct ambiant decay from room boundries (real or virtual) - a.k.a. "hall sound". (Of course along with this "theme" are also things like lower mass drivers with high force.) I suppose then that the best material from purely a "friction" standpoint then would be a polished ultra high density plastic skin on the internal walls, but it isn't just about friction..
3. We desire a low reflection internal cabinet. Unfortunetly this is almost diametrically opposed to # 2 from a construction viewpoint. Here we have problems from any reflective surface, including the driver's frame. The higher the driver's mass for a given surface area - the less problem (..but also the less able it is to produce ambiant decay). This is where I like the space shuttle stuff - i.e. the silicone borscilate additive, (that I provided a link to), to a lossy absorptive paint like latex primer (..note: the cheaper the latex primer the better). This is actually a broad-band absoptive material - unlike most materials. It however is no where near as good as a long fiber "batting" - and this is where you might want to experiment with some batting well away from walls and the driver. These resrictions then suggest that the stuffing (if used) should be placed behind the magnet (but not close to it). Of course the silicone borscilate paint (on walls) doesn't just reduce reflections..
4. We desire a dampened cabinet. That same space shuttle derived paint (applied thickly) reduces sound transmission from the internal cabint to the walls, and also from the walls to the internal cabinet (..the little ceramic "beads" are after all vacuums at their center). Additionally, it marginally reduces (dampenes) vibration of the cabinet walls themselves. However, MUCH more attention needs to be "paid" here. The worst offense here is NOT cabinet walls contributing to the overall spl. No, the real offender is vibration transmitted back to the frame of the driver. (..and this adds all manner of distortion - yes, measurable distortion.) This however is not meant to "downplay" the importance of supressing spl contribution (particularly high level modes) from the cabinet walls, instead it is mentioned so that we can place the greater emphasis where it is needed. Of course this doesn't mean that the method of dampening need not be complimentary to both problems (..and in fact other problems as well). So then..
The standard thick wall braced construction does substantially reduce sound transmission from the cabinet walls - BUT it doesn't do much at all for vibration reaching the driver's frame. We could use a multi-sectioned mult-material laminated approach (i.e. constrained layer) - but d@mn, thats a LOT of work and I'm personally FAR to lazy to have tried something like that (..and besides it doesn't help out a great deal with another problem I'll suggest latter). So then lets "break-down" how the constrained layer is most effective to our two problems. One, the layers with multi-materials are converting vibration into heat. Two, the connection between internal transmission and driver mounting are seperated by several layers - i.e. sound hits the internal panel and then it must make its way to the outer "skin" layer that is conneceted to the driver's frame. OK then, at a minimum we need 2 "skins" - i.e. one internal wall(s) and one external wall(s) or basically a box within a box. We also want a lossy material in-between the two to convert vibration into heat. Furthermore we would like a fair bit of distance between the two walls to make-up for our lack of multi-layers.
So then - box within box construction and a LOT of lossy material in-between the 2 boxes. What material? The same stuff you snuff-out that nasty habit of yours - ultra fine sand. (..And don't use anything but that super fine white sand.) The amount of space? An inch to an inch and a half for the bottom partition. 4 inches every where else (..yes, that much - do NOT reduce this, I've tried several versions - particularly to reduce the top, and it is a *bad* idea), you could however increase this. Now this does pose a few problems the first time I tried it:
A. Depending on the shape of the box and the thickness of the panels this "bulges" the panels outward (and inward as the case may be).
B. Then you have the problem of the driver and port and sand leaking out (..and frankly my powers of description will be the biggest "obstacle" here).
Some assembly (required) and materials, and a LOT of planning..
Well one of the strange things here is that it is better to use panels that are less thick rather than more thick - think 3/4 inch (or as close to it "metrically" as possible). Consider that it is usually cheaper, weighs less, and takes up less space (than the full inch variety) - unfortunetly it also is less structurally rigid and could "bulge" to the point of busting (depending on the quality of wood or mdf). Thats OK though, will will use some "bracing" here but it won't be conventional bracing - in fact it will be a LOT easier than conventional bracing (..though perhaps more "tedious"). Think frankenstien's monster - specifically via the use of numerous "bolts" coupling the 2 boxes together on every panel BUT the bottom panels. This raises a design point here - the bottom panel will be our "fill" panel (i.e. it will be the panel we have acces to to fill the air-space). I'll get back to this in a moment. Anyway, the bolts can either have the head on the outside of the cabinet with the nut on the inside (or the converse) - I'd ***strongly*** suggest them on the outside. You'll need multiple bolts that:
A. Span the 4 inch distance + the amount required for the panels.
B. Have a head and a very thin LARGE diameter steel washer and LARGE diameter compliant (paper) washer that when combined and tightened down is no more than 2/3rds the thickness of the 3/4 inch wall. (i.e. we are countersinking the bolt and washers here so that it doesn't extend beyond the surface of the panel.)
C. Have threads that span their entire length (at least for the "top" panel bolts)
I personally just browse my local hardware store with a tape measure and picked up about 40 (in combination) of what looked best. I think the large washer's were at least an inch in diameter. Then went over a few isles and found a forstner bit for my hand-held drill that matched/slightly exceeded the diameter of the large washers. (..I already had the bits for the bolt's diameter). Of course it wasn't just the bolt and those two washers.. In order, this was the connection (for all box panels but the bottom 2):
Side panels:
A. Bolt Head, B. Steel washer, C. Paper washer, E. Exterior panel, F. Air space (to be filled with sand), G. Interior panel, H. **Felt** washer, I. Steel washer, J. "Tightning" cut-washer, K. Nut. L. Bolt end.
Top panel:
A. Bolt Head, B. Steel washer, C. Paper washer, D. Exterior panel, E. Felt washer, F. Steel washer, G. "Tightening" cut-washer, H. Nut, I. Air space (to be filled with sand), J. Nut, K. "Tightening" cut-washer, L. Steel washer, M. **Felt** washer, N. Interior panel, O. **Felt** washer, P. Steel washer, Q. "Tightening" cut-washer, R. Nut, S. Bolt end.
The reason for the difference here is that the top panel will need the extra nuts and washers to set the interior panel 4 inches away from the exterior panel.
*****The next thing then is figuring out panel sizes and getting them panel ripped at the hardware store (..while watching and measuring of course).) The panel "pairs" from one box to the next will **nominally** have a 4 inch difference on 3 sides, *BUT* - you have to factor in exactly how you will join the boxes together. In otherwords you will likely connect the boxes with overlaping panels (..rather than using a compound cut to the edges that keeps them the same size). If you use the "overlapping" method most panels will be slightly different in size. Additionally you will need to account for lengths and joint methods to the bottom panels as well. Keep this in mind when determining each panel size - othewise you'll screw everything up.***** (i.e. measure 100 times, have a drawing with dimensions when you enter the hardware store to purchase and cut the panels, THEN have them cut while overseeing/measuring and marking each panel as its cut.) (..and yes, I screwed this up the first time.) Of course you probably have a good table saw, so the cutting will be up to you.
Next it gets a little "tricky" with respect to assembly (..though not difficult). The problem here is exactly how will you "line-up" your bolt holes and counter sink recesses? You could plan the thing out with a cad program, or do the low tech approach that I did - "tracing" paper. (..and it doesn't have to be actual tracing paper - just something you can see through fairly well with a black felt marker (..heck if your cutting it then you don't even have to see through it - you could use poster board).) The paper route then:
Get, (or create with cheap printer paper and scotch tape), 2 pieces of paper for each double wall panel (5 panels ='s 10 pieces). Each piece of paper will be the size of each coresponding panel. Mark them to make sure you know which panel is which, AND what is top and what is bottom. With the appropriate panel pair of papers, place the smaller one on top of the larger one and *temp.* corner tape them to each other so that **nominally**, (see the panel cut section above), 4 inches is bordered on **3** sides (..you won't need to worry about the bottom). Somewhat randomly mark where you want to place the bolt holes and make sure some of the ink "bleeds" through to the bottom paper, OR use an exacto knife and cut the holes (..with a cutting board underneath of course). The placement of the holes isn't critical - just make sure they are not to close to each other or the sides of the panel, *don't* make them uniform (i.e. in a row every 6 inches), AND make 5-7 holes (..up to you). Next un-tape the two sheets and then tape the two sheets to their respective wood panels and drill the bolt holes. (Do this for every panel pair.) Then use the forstner bit and be very carefull about the depth of the countersinking you do to the panels (..in particular I think for the exterior panel I did a little and then tested with the bolt and washers, rinse&repeat until the bolt was flush). (Do this for every panel pair) If you have acces to a drill press with arm-extension then you are a lucky b@stard and you can set the depth - alternativly there are those cheap "plunge" depth guides that could be used for hand-held drills. Its all tedious, but its also very easy to do (..and I don't remember taking very long to actually do it).
(*****Note that IF you decide to place the woofer on a side panel this would be the time to mark it out on the paper and then cut/drill it for the appropriate panel pair along with any baffle mounting holes for the exterior panel - something I'll go into latter.*****)
Make sure to keep the papers in case you decide you like the result and want to make another.
The next step is to cut the biscut joints or drill the peg holes for joining **ALL** the panels together (i.e. all 6 panels for each, interior and exterior, box). Alternativly you can "cheap-out" and here and latter uses wood screws to assemble the boxes. (..probably not a good idea with soft mdf and edges.)
Next it gets a little "tricky" with respect to assembly (..though not difficult). The problem here is exactly how will you "line-up" your bolt holes and counter sink recesses? You could plan the thing out with a cad program, or do the low tech approach that I did - "tracing" paper. (..and it doesn't have to be actual tracing paper - just something you can see through fairly well with a black felt marker (..heck if your cutting it then you don't even have to see through it - you could use poster board).) The paper route then:
Get, (or create with cheap printer paper and scotch tape), 2 pieces of paper for each double wall panel (5 panels ='s 10 pieces). Each piece of paper will be the size of each coresponding panel. Mark them to make sure you know which panel is which, AND what is top and what is bottom. With the appropriate panel pair of papers, place the smaller one on top of the larger one and *temp.* corner tape them to each other so that **nominally**, (see the panel cut section above), 4 inches is bordered on **3** sides (..you won't need to worry about the bottom). Somewhat randomly mark where you want to place the bolt holes and make sure some of the ink "bleeds" through to the bottom paper, OR use an exacto knife and cut the holes (..with a cutting board underneath of course). The placement of the holes isn't critical - just make sure they are not to close to each other or the sides of the panel, *don't* make them uniform (i.e. in a row every 6 inches), AND make 5-7 holes (..up to you). Next un-tape the two sheets and then tape the two sheets to their respective wood panels and drill the bolt holes. (Do this for every panel pair.) Then use the forstner bit and be very carefull about the depth of the countersinking you do to the panels (..in particular I think for the exterior panel I did a little and then tested with the bolt and washers, rinse&repeat until the bolt was flush). (Do this for every panel pair) If you have acces to a drill press with arm-extension then you are a lucky b@stard and you can set the depth - alternativly there are those cheap "plunge" depth guides that could be used for hand-held drills. Its all tedious, but its also very easy to do (..and I don't remember taking very long to actually do it).
(*****Note that IF you decide to place the woofer on a side panel this would be the time to mark it out on the paper and then cut/drill it for the appropriate panel pair along with any baffle mounting holes for the exterior panel - something I'll go into latter.*****)
Make sure to keep the papers in case you decide you like the result and want to make another.
The next step is to cut the biscut joints or drill the peg holes for joining **ALL** the panels together (i.e. all 6 panels for each, interior and exterior, box). Alternativly you can "cheap-out" and here and latter uses wood screws to assemble the boxes. (..probably not a good idea with soft mdf and edges.)
On to "some" assembly..
Initial assembly is also very easy and moderatly quick - AS LONG AS YOU PROCEED IN THE CORRECT SEQUENCE.
1. Connect ALL the bolts to the *top* **exterior** panel using the nut combination on each side of the panel as directed in the sequence above.
2. Screw the next nuts (including all washers) so that you have the top of that (combination) a little higher than 4 inches from the exterior top. (..giving a little extra length here for when the nut is tightened and reduced to 4 inches of space.) Do this for ALL the bolts here. (..measure them all.)
3. Place the *top* **interior** panel "on" the bolts and slide it down until it rests on the nut (combination).
4. Next screw down the final nut (combination) to the interior top panel. Do this for ALL the bolts here.
5. Tighten # 2 and # 4 (all the bolts), so that the height from one panel to the next leaves 4 inches of air space. (..you will need a standard wrench here, as opposed to a ratchet, for the "air-space" tightening. Take your time, get it done correctly.)
6. Assemble all 4 **interior** side panels to the interior top panel, making sure each panel is correct to your schematics. If biscuit/peg joined with glue and clamps - then wait for the glue to dry.
7. Assemble all 4 **exterior** side panels to the exterior top panel (..etc.)
You should now have 2 open boxes - one inside another with 4 inches of air-space on all sides except obviously the open end. The open end of the exterior box should have 1 and 1/2 inches of length extending beyond the interior open box. (Note: the 3/4 "height of the bottom interior panel will not decrease the space by 3/4 inches because the bottom exterior panel will also extend 3/4 inches.) IF the driver is going to be placed in a side panel then the holes should be seen and they should line-up correctly.
Initial assembly is also very easy and moderatly quick - AS LONG AS YOU PROCEED IN THE CORRECT SEQUENCE.
1. Connect ALL the bolts to the *top* **exterior** panel using the nut combination on each side of the panel as directed in the sequence above.
2. Screw the next nuts (including all washers) so that you have the top of that (combination) a little higher than 4 inches from the exterior top. (..giving a little extra length here for when the nut is tightened and reduced to 4 inches of space.) Do this for ALL the bolts here. (..measure them all.)
3. Place the *top* **interior** panel "on" the bolts and slide it down until it rests on the nut (combination).
4. Next screw down the final nut (combination) to the interior top panel. Do this for ALL the bolts here.
5. Tighten # 2 and # 4 (all the bolts), so that the height from one panel to the next leaves 4 inches of air space. (..you will need a standard wrench here, as opposed to a ratchet, for the "air-space" tightening. Take your time, get it done correctly.)
6. Assemble all 4 **interior** side panels to the interior top panel, making sure each panel is correct to your schematics. If biscuit/peg joined with glue and clamps - then wait for the glue to dry.
7. Assemble all 4 **exterior** side panels to the exterior top panel (..etc.)
You should now have 2 open boxes - one inside another with 4 inches of air-space on all sides except obviously the open end. The open end of the exterior box should have 1 and 1/2 inches of length extending beyond the interior open box. (Note: the 3/4 "height of the bottom interior panel will not decrease the space by 3/4 inches because the bottom exterior panel will also extend 3/4 inches.) IF the driver is going to be placed in a side panel then the holes should be seen and they should line-up correctly.
Now we move onto the choice for driver placement, box shape, baffle, and "skinning"..
The driver can be placed downward firing OR on a side panel.. I'd *strongly* suggest a side panel for several reasons:
1. IF you have it downward firing you increase the spl in the upper part of our passband by +3db, which is pretty much the opposite of whats required. Still, there isn't any thing wrong with that if you can correct for it.
2. It will raise the sub up even higher with the cement baffle (3 inches).
3. The physical sensation of nearfield air compression is an odd thing - it is felt the most when the driver is directly aimed at the listener and the passband is from 30 Hz to 200 Hz. The 30 to 60 Hz region is typically termed "slam", and the region above is termed "punch". I think its likely you will want the "slam" character as much as possible and so I'm suggesting that you have the driver "aimed" (with in +/- 80 degrees) at you and as such it should be side panel mounted. Of course a fair bit of this "slam" character is allocated to the port - but it really needs to be downward firing.
4. Most importantly, the downward firing driver will disturb the additonal air mass of our porting scheme.
None of this is to say you can't have it downward firing, but I'll continue on with the premis that it will be side mounted. If however you decide differently you should still be able to "gleen" what required to make the adjustment.
Next you need to consider the box shape and driver in relation to it..
You have already mentioned that the box will be a rectangle - which is good because its easier to construct, but you need to how you will place this subwoofer in the room - particularly in relation to yourself and boundries. For instance we don't want the driver up near the wall. Additionally, IF possible we want the driver with in the +/- 80 degrees from you for a greater tactile sensation. Furthermore it would also be advantageous for the driver to have more air-space around it - so its better if the driver is placed on one of the "wider" side panels. Of course the "wider" side panel doesn't need to be much wider - the shape could be more cube-like if you wished (..and a more cube-like structure could more effectivly be "skinned" to achieve a particular esthetic with an additional cosmetic case/cover).
With regard to room placement there are 3 basic "good" locations that will provide the "focused compression" mentioned above, while being away from room boundries:
1. In between the perceives either forward firing on side firing toward the center of the room.
2. As a side-table next to your listening position with the driver aimed toward you.
3. As a rear end-table behind your listening position with the driver aimed toward you.
Any of these 3 locations could be paired with another identical sub. In the case of #'s 1 & 3 the subs would be fairly close to each other, and in the case of # 2 they would be further apart.
Room-mode wise (with 2 mono subs) the BEST placement would almost certainly be # 2. (something like a giant pair of headphones, but esthetically like side tables.)
Another thing to think about with 2 subs is the esthetic in pairing and the ease of construction. To make truely identical subs that can be positioned in-opposite to each other requires that the *driver* be centered on its panel. Alternativly, you could just use a "grill" screen that was proportional, BUT that severely limits how you can "skin" the outside of the basic box. While the port isn't an esthetic concern - you can easily rotate the bottom panels 180 degrees, (front-to-back switched to back-to-front), provided it is centered on the short width of the panel (..if the driver is on the wider panel).
The driver can be placed downward firing OR on a side panel.. I'd *strongly* suggest a side panel for several reasons:
1. IF you have it downward firing you increase the spl in the upper part of our passband by +3db, which is pretty much the opposite of whats required. Still, there isn't any thing wrong with that if you can correct for it.
2. It will raise the sub up even higher with the cement baffle (3 inches).
3. The physical sensation of nearfield air compression is an odd thing - it is felt the most when the driver is directly aimed at the listener and the passband is from 30 Hz to 200 Hz. The 30 to 60 Hz region is typically termed "slam", and the region above is termed "punch". I think its likely you will want the "slam" character as much as possible and so I'm suggesting that you have the driver "aimed" (with in +/- 80 degrees) at you and as such it should be side panel mounted. Of course a fair bit of this "slam" character is allocated to the port - but it really needs to be downward firing.
4. Most importantly, the downward firing driver will disturb the additonal air mass of our porting scheme.
None of this is to say you can't have it downward firing, but I'll continue on with the premis that it will be side mounted. If however you decide differently you should still be able to "gleen" what required to make the adjustment.
Next you need to consider the box shape and driver in relation to it..
You have already mentioned that the box will be a rectangle - which is good because its easier to construct, but you need to how you will place this subwoofer in the room - particularly in relation to yourself and boundries. For instance we don't want the driver up near the wall. Additionally, IF possible we want the driver with in the +/- 80 degrees from you for a greater tactile sensation. Furthermore it would also be advantageous for the driver to have more air-space around it - so its better if the driver is placed on one of the "wider" side panels. Of course the "wider" side panel doesn't need to be much wider - the shape could be more cube-like if you wished (..and a more cube-like structure could more effectivly be "skinned" to achieve a particular esthetic with an additional cosmetic case/cover).
With regard to room placement there are 3 basic "good" locations that will provide the "focused compression" mentioned above, while being away from room boundries:
1. In between the perceives either forward firing on side firing toward the center of the room.
2. As a side-table next to your listening position with the driver aimed toward you.
3. As a rear end-table behind your listening position with the driver aimed toward you.
Any of these 3 locations could be paired with another identical sub. In the case of #'s 1 & 3 the subs would be fairly close to each other, and in the case of # 2 they would be further apart.
Room-mode wise (with 2 mono subs) the BEST placement would almost certainly be # 2. (something like a giant pair of headphones, but esthetically like side tables.)
Another thing to think about with 2 subs is the esthetic in pairing and the ease of construction. To make truely identical subs that can be positioned in-opposite to each other requires that the *driver* be centered on its panel. Alternativly, you could just use a "grill" screen that was proportional, BUT that severely limits how you can "skin" the outside of the basic box. While the port isn't an esthetic concern - you can easily rotate the bottom panels 180 degrees, (front-to-back switched to back-to-front), provided it is centered on the short width of the panel (..if the driver is on the wider panel).
Next we need to look at the cement baffle, and "skinning" in relation to it..
1. What will the dimensions be?
2. Will it span the entire side panel?
3. How will it be connected to the box?
4. Will it form the barrier/driver cavity between exterior and interior panels (i.e. so sand doesn't pour into the rear of the driver and box interior)?
5. Will any additonal panel material be used to surround it if it does not span the entire panel?
I'll take the easiest of the bunch here first, (and the most pertinant for "finishing" the initial assmebly as mentioned above), - # 3? The baffle should also be connected to the box via bolts - but not exactly as we connected the interior panels to the exterior panels. Here we specifically do NOT want to connect (directly at least) to the interior panel. Effectivly we want the driver/frame induced vibration carried away from the frame via a the dense cement baffle, then "drained" to a lossier material like the mdf exterior panel, then dampend further via the sand pushed up against the mdf. (i.e. truely "massive" construction.) Functionally it would be like this:
A. Bolt head, B. Steel washer, C. Paper washer, D. Cement baffle, E. Exterior panel, F. Steel washer, G. "Tightening" cut-washer, H. Nut, I. Bolt end
Additonally, we need more bolts for the surface area this time - AND they can be uniform in placement (i.e. in "rows"). The larger the cement baffle, the more bolts. Bolts heads should be flush with the baffle as per the exterior panels. At a minimum I'd suggest 8 (depending on baffle size). Of course the length of the bolts will be pretty short this time.
*****Because were are "side" panel mounting the driver this means that we need to have a template with the bolt holes draw/cut for the exterior panel - BEFORE we start cutting the exterior panel. We also need to make sure that the free-hand bolt positions of the Interior/Exterior mounts do NOT overlap the holes for the Baffle/Exterior panel. Once you have a template sheet that has both holes "types" where they need to be, AND the driver's hole, only then can you tape it to the exterior panel and drill it.*****
Once the baffle has been "formed" and the exterior panel cut and mounted - the attachment to the exterior panel will take about a minute per bolt. (In fact with the exception of the top panel bolt connection - bolt assembly is *VERY* fast.)
Anyway, with regard to baffle size and "skinning" the enclosure - the less cement baffle you have the easier it will be to place on a compound angle "skin" near the driver if desired.. On the other hand the smaller the cement baffle - the less effective it will be sonically. Another thing to consider here is ease of construction, perhaps the easiest baffle would the largest -i.e. the 3 inch thick baffle spanning the entire surface area of the exterior side panel. This is up to you, but obviously you need to decide before construction. IF you do have it spanning the entire surface area of the side panel *remember* - the bottom exterior panel will add to the effective height by 3/4 inches over the exterior side panel. So in fact the baffle will be larger than the exterior side panel by 3/4 inches in height. It may also be an additional 3/4 inches in height IF the exterior panel is connected to the top panel like it is to the bottom. Additonally, you also need to factor in bolt hole positions with respect to these possible 3/4 inch variations - again this is one of those planning things.
Finally, I'd suggest forming your cement baffle so that it does in fact form the barrier/driver cavity between exterior and interior panels.
1. What will the dimensions be?
2. Will it span the entire side panel?
3. How will it be connected to the box?
4. Will it form the barrier/driver cavity between exterior and interior panels (i.e. so sand doesn't pour into the rear of the driver and box interior)?
5. Will any additonal panel material be used to surround it if it does not span the entire panel?
I'll take the easiest of the bunch here first, (and the most pertinant for "finishing" the initial assmebly as mentioned above), - # 3? The baffle should also be connected to the box via bolts - but not exactly as we connected the interior panels to the exterior panels. Here we specifically do NOT want to connect (directly at least) to the interior panel. Effectivly we want the driver/frame induced vibration carried away from the frame via a the dense cement baffle, then "drained" to a lossier material like the mdf exterior panel, then dampend further via the sand pushed up against the mdf. (i.e. truely "massive" construction.) Functionally it would be like this:
A. Bolt head, B. Steel washer, C. Paper washer, D. Cement baffle, E. Exterior panel, F. Steel washer, G. "Tightening" cut-washer, H. Nut, I. Bolt end
Additonally, we need more bolts for the surface area this time - AND they can be uniform in placement (i.e. in "rows"). The larger the cement baffle, the more bolts. Bolts heads should be flush with the baffle as per the exterior panels. At a minimum I'd suggest 8 (depending on baffle size). Of course the length of the bolts will be pretty short this time.
*****Because were are "side" panel mounting the driver this means that we need to have a template with the bolt holes draw/cut for the exterior panel - BEFORE we start cutting the exterior panel. We also need to make sure that the free-hand bolt positions of the Interior/Exterior mounts do NOT overlap the holes for the Baffle/Exterior panel. Once you have a template sheet that has both holes "types" where they need to be, AND the driver's hole, only then can you tape it to the exterior panel and drill it.*****
Once the baffle has been "formed" and the exterior panel cut and mounted - the attachment to the exterior panel will take about a minute per bolt. (In fact with the exception of the top panel bolt connection - bolt assembly is *VERY* fast.)
Anyway, with regard to baffle size and "skinning" the enclosure - the less cement baffle you have the easier it will be to place on a compound angle "skin" near the driver if desired.. On the other hand the smaller the cement baffle - the less effective it will be sonically. Another thing to consider here is ease of construction, perhaps the easiest baffle would the largest -i.e. the 3 inch thick baffle spanning the entire surface area of the exterior side panel. This is up to you, but obviously you need to decide before construction. IF you do have it spanning the entire surface area of the side panel *remember* - the bottom exterior panel will add to the effective height by 3/4 inches over the exterior side panel. So in fact the baffle will be larger than the exterior side panel by 3/4 inches in height. It may also be an additional 3/4 inches in height IF the exterior panel is connected to the top panel like it is to the bottom. Additonally, you also need to factor in bolt hole positions with respect to these possible 3/4 inch variations - again this is one of those planning things.
Finally, I'd suggest forming your cement baffle so that it does in fact form the barrier/driver cavity between exterior and interior panels.
This last section focuses on the bottom panels and final assembly..
The bottom panels are **really** simple, both in ease of construction and assembly. The interior bottom panel will need a hole the size of the exterior of the interior port. It will also need some sort of connection method on the interior side with external pipe. The panel will be placed directly on top of the interior open box like a lid or a plate. The exterior panel will have the same size hole for the interior port and will have a connection method at the bottom (outside) the exterior bottom panel. (..the connection needs to be flush to not create any air disturbances.) Again, the exterior panel will also be placed like a lid or plate directly on the exterior open box. Functionally it will be like this:
A. Exterior pipe wrapped around interior port, B. Exterior pipe stops at the "floor" of the interior box and is connected to that "floor", C. Interior port pushes through the hole in the interior bottom panel, D. Interior port is surrounded by sand for 1 and 1/2 inches, E. Interior port pushes through the hole in the exterior bottom panel, F. Interior port is connected to the bottom exterior panel via flush mounting with the panel.
In addition the bottom 2 panels will need a small hole for the electrical connection. Or for the exterior panel, if you want a junction terminal for the wires on the bottom of the exterior panel - then make sure it is flush with the cabinet and sealed with silicone caulk. Furthermore keep the junction as far away from the port as possible.
Two other things with respect to the bottom panel:
1. the spikes will need to be interfaced to this panel - I strongly recomend the spikes with the pointy end up touching the bottom panel via a fairly large surface area metal disk (thats flush with the panel surface), The disk should be something like the large steel washers except without the holes and a bit larger. This will give the support required for the tremendous weight so that the spike doesn't "sink" into the cabinet.
2. the bottom panel should be painted/finshed before being placed on the cabinet.
The assmbly would look like this:
Previous initial assembly (abreviated version with "sealing"):
(Note that the cabinet is being built upside down - the top on the floor and building up to the bottom of the cabinet. Additionally it is presumed that the platform is completed including painted/finished with the spikes inserted where appropriate.)
1. Connect top panels together
2. Connect interior side panels together
3. Seal around interior panel joints with silicone caulk
4. Connect baffle to one exterior panel
5. Connect exterior panels together (with friends help for the baffle connected panel)
6. Seal around exterior panel joints with silicone caulk
7. Seal around interior panel and baffle ("extension") with silicone caulk
continuing on..
8. Connect wire to driver
9. Connect driver to baffle and feed wire through to interior
10. Connect exterior pipe and interior port assembly to interior bottom panel
11. Paint interior open box, magnet and frame (at least 5 coats) with double "strength" nasa paint. (use paint brush.)
11. Seal pipe/port assembly to panel on both sides of interior bottom panel with silicone caulk
12. Paint interior bottom panel (interior side only) and connected pipe/port assembly exterior as in # 11.
13. Manuever interior bottom panel into position and feed wire through it.
14. Seal the wire feed hole in # 13 with silicone caulk
15. Connect the bottom interior panel to the interior open box - to complete a "closed" interior box.
16. Seal the panel in # 15 with silicone caulk at the joints.
17. Pour into the box ultra-fine white sand until flush with the exterior open box
18. Manuever painted/finished bottom exterior panel over exterior open box and feed port and wire through it (..or connect wire to terminal)
19. Seal wire with silicone caulk if you didn't use a terminal
20. Connect port to bottom exterior panel
21. Seal port to bottom of exterior panel with silicone caulk
22. Connect bottom exterior panel to exterior open box - to complete a closed exterior box.
23. Seal the panel in # 22 with silicone caulk at the joints
24. Get friends to help you flip the box over and place on spikes of platform
25. Place "skin" painted/finished cover over box.**
(**now of course you could have alternatly filled in the bolt depressions that are all over the exterior of the box with a filling compound and then painted the box - a viable (if less flexible) alternative to the "skin" approach.)
The bottom panels are **really** simple, both in ease of construction and assembly. The interior bottom panel will need a hole the size of the exterior of the interior port. It will also need some sort of connection method on the interior side with external pipe. The panel will be placed directly on top of the interior open box like a lid or a plate. The exterior panel will have the same size hole for the interior port and will have a connection method at the bottom (outside) the exterior bottom panel. (..the connection needs to be flush to not create any air disturbances.) Again, the exterior panel will also be placed like a lid or plate directly on the exterior open box. Functionally it will be like this:
A. Exterior pipe wrapped around interior port, B. Exterior pipe stops at the "floor" of the interior box and is connected to that "floor", C. Interior port pushes through the hole in the interior bottom panel, D. Interior port is surrounded by sand for 1 and 1/2 inches, E. Interior port pushes through the hole in the exterior bottom panel, F. Interior port is connected to the bottom exterior panel via flush mounting with the panel.
In addition the bottom 2 panels will need a small hole for the electrical connection. Or for the exterior panel, if you want a junction terminal for the wires on the bottom of the exterior panel - then make sure it is flush with the cabinet and sealed with silicone caulk. Furthermore keep the junction as far away from the port as possible.
Two other things with respect to the bottom panel:
1. the spikes will need to be interfaced to this panel - I strongly recomend the spikes with the pointy end up touching the bottom panel via a fairly large surface area metal disk (thats flush with the panel surface), The disk should be something like the large steel washers except without the holes and a bit larger. This will give the support required for the tremendous weight so that the spike doesn't "sink" into the cabinet.
2. the bottom panel should be painted/finshed before being placed on the cabinet.
The assmbly would look like this:
Previous initial assembly (abreviated version with "sealing"):
(Note that the cabinet is being built upside down - the top on the floor and building up to the bottom of the cabinet. Additionally it is presumed that the platform is completed including painted/finished with the spikes inserted where appropriate.)
1. Connect top panels together
2. Connect interior side panels together
3. Seal around interior panel joints with silicone caulk
4. Connect baffle to one exterior panel
5. Connect exterior panels together (with friends help for the baffle connected panel)
6. Seal around exterior panel joints with silicone caulk
7. Seal around interior panel and baffle ("extension") with silicone caulk
continuing on..
8. Connect wire to driver
9. Connect driver to baffle and feed wire through to interior
10. Connect exterior pipe and interior port assembly to interior bottom panel
11. Paint interior open box, magnet and frame (at least 5 coats) with double "strength" nasa paint. (use paint brush.)
11. Seal pipe/port assembly to panel on both sides of interior bottom panel with silicone caulk
12. Paint interior bottom panel (interior side only) and connected pipe/port assembly exterior as in # 11.
13. Manuever interior bottom panel into position and feed wire through it.
14. Seal the wire feed hole in # 13 with silicone caulk
15. Connect the bottom interior panel to the interior open box - to complete a "closed" interior box.
16. Seal the panel in # 15 with silicone caulk at the joints.
17. Pour into the box ultra-fine white sand until flush with the exterior open box
18. Manuever painted/finished bottom exterior panel over exterior open box and feed port and wire through it (..or connect wire to terminal)
19. Seal wire with silicone caulk if you didn't use a terminal
20. Connect port to bottom exterior panel
21. Seal port to bottom of exterior panel with silicone caulk
22. Connect bottom exterior panel to exterior open box - to complete a closed exterior box.
23. Seal the panel in # 22 with silicone caulk at the joints
24. Get friends to help you flip the box over and place on spikes of platform
25. Place "skin" painted/finished cover over box.**
(**now of course you could have alternatly filled in the bolt depressions that are all over the exterior of the box with a filling compound and then painted the box - a viable (if less flexible) alternative to the "skin" approach.)
Conclusion and final thoughts:
The planning and assembly process is part of the reason why this series of posts is so long. The other reason is because the final form is still quite variable (..and I wanted to point out variations and reasons for or against them).
So then..
Despite the lenth of these posts, the box is extremely easy to fabricate and assemble - EXCEPT for the cement baffle (and that isn't terribly difficult either). The real time waster is not either, but rather the plannning process - i.e. making sure you are getting all the cuts and holes correct, and making sure assembly is in the correct order.
Consider that the box itself is composed of only 12 pieces of mdf. Thats not a lot of cuts, (especially if you have someone else do them). Moreover there is nothing "fancy" about the cuts - no compound angles or angles of any kind, just some simple rectangles.
There are holes to drill - but with the templates that will take only a few minutes for all the panels.
There are also some forstner-bit depth "cuts" to do (on the exterior panels) - but again not much more than a few minutes total.
Making the form for the cement baffle will be more time consuming than the above, but it should prove no more complicated than making some interior cabinet bracing. Again, PLANNING the form will prove more time consuming than actually making it. The cement pour itself is nothing more than mix, pour, scree with flat edge trowle, let dry, remove form.
Assembly? - VERY easy except for the the shear weight when connecting the baffle.. and placing the cabinet on the platform.
In any event..
If you have questions on the design (basic or complex) ask away and hopefully I'll respond quickly (..I'm sure I've left out a lot of things here despite the length). I've done most of this previously with a modification of a loudspeaker I thought was good - but it originally had a poor enclosure and porting. (..and yes, it makes a *BIG* difference.) I have not done this type of enclosure yet with a subwoofer.
The planning and assembly process is part of the reason why this series of posts is so long. The other reason is because the final form is still quite variable (..and I wanted to point out variations and reasons for or against them).
So then..
Despite the lenth of these posts, the box is extremely easy to fabricate and assemble - EXCEPT for the cement baffle (and that isn't terribly difficult either). The real time waster is not either, but rather the plannning process - i.e. making sure you are getting all the cuts and holes correct, and making sure assembly is in the correct order.
Consider that the box itself is composed of only 12 pieces of mdf. Thats not a lot of cuts, (especially if you have someone else do them). Moreover there is nothing "fancy" about the cuts - no compound angles or angles of any kind, just some simple rectangles.
There are holes to drill - but with the templates that will take only a few minutes for all the panels.
There are also some forstner-bit depth "cuts" to do (on the exterior panels) - but again not much more than a few minutes total.
Making the form for the cement baffle will be more time consuming than the above, but it should prove no more complicated than making some interior cabinet bracing. Again, PLANNING the form will prove more time consuming than actually making it. The cement pour itself is nothing more than mix, pour, scree with flat edge trowle, let dry, remove form.
Assembly? - VERY easy except for the the shear weight when connecting the baffle.. and placing the cabinet on the platform.
In any event..
If you have questions on the design (basic or complex) ask away and hopefully I'll respond quickly (..I'm sure I've left out a lot of things here despite the length). I've done most of this previously with a modification of a loudspeaker I thought was good - but it originally had a poor enclosure and porting. (..and yes, it makes a *BIG* difference.) I have not done this type of enclosure yet with a subwoofer.
About time Scott 😀
Is that all you've wrote, you've certainly left a lot to the imagination.
Seriously though, spot on! I'd send you a six pack of lager if I didn't think the blokes at US customs would drink it.
I'll have a good read and no doubt you can clarify things that I'm hazy on or would maybe have to compromise.
Is that all you've wrote, you've certainly left a lot to the imagination.
Seriously though, spot on! I'd send you a six pack of lager if I didn't think the blokes at US customs would drink it.
I'll have a good read and no doubt you can clarify things that I'm hazy on or would maybe have to compromise.
ShinOBIWAN said:
😀
Funny - I was thinking the VERY same thing!
(..grumble, grumble - there is a saturday evening I won't get back.. 😉 )
Scott
Very interesting. However a picture is worth a thousand words! 🙂
I've been trying to find my calculations for the PD2150 to show that I was correct, however I can't, so I'll just admit defeat and put it down to my dodgy memory.
Very interesting. However a picture is worth a thousand words! 🙂
I've been trying to find my calculations for the PD2150 to show that I was correct, however I can't, so I'll just admit defeat and put it down to my dodgy memory.
pinkmouse said:Scott
Very interesting. However a picture is worth a thousand words! 🙂
I've been trying to find my calculations for the PD2150 to show that I was correct, however I can't, so I'll just admit defeat and put it down to my dodgy memory.
I can't draw and I've got no digital camera (well not one that works anyway). 🙄
I suppose I could try with MS paint or some such..
I'm impressed but a little confused about the driver side baffles. How is the driver mounted to the cement? Flushed? How is the sand not pouring on the driver or into the interior box? I'm missing that step but otherwise think your tutorial was great. email if you'd like to alexcd@gmail.com
ShinOBIWAN said:
You know you like large 🙂
I normally don't recommend cheap drivers for projects,
but ... cheap drivers can be quality drivers at a lower cost.
My NSB project showed me what really happens when you
use 49 cent buyout 4" midwoofers in an array vs. standalone.
In an array, performance increases alot. Never underestimate
the power of an array.
However a picture is worth a thousand words!
Edited for accuracy
However a picture is worth a million words!
Edited for accuracy
However a picture is worth a million words!
alexcd said:
After reading it over again I was, shall we say, "less than impressed". 😉 But I wasn't aiming for perfection, so I'm not bummed.
I did try to be more specific with those areas that were critcal though (particularly the order of assembly), so I wasn't entirely dissatisfied with that.
Most of the cement/concrete baffle build information is considerably further back in this thread.
You can mount the drivers with screws to the cement baffle. In fact, IF you use pure cement then you can just use a screw made for it without fear of hitting aggregate. Unfortunetly though it isn't good for unscrewing and rescrewing without some other material like a plastic filler used for the thread holes in the cement. (i.e. its usually better to drill a hole, fill it with plastic filler, let the plastic dry, then drill the screw into the plastic "hole" to secure the frame to the baffle.)
Flush mount the driver - meaning in the cement form you will need to account for the driver's frame connection depth. (i.e. its a negative "impression" here so you add a base "ring" the same thickness and diameter as the drivers frame.)
From a non-mold "possitive" perspective:
For the cavity space you should essentially have a cylinder of cement that rises from the cement baffle - all of it a monolithic structure (i.e. one single piece of cement). (..physically imagine a platter carrying a cup: the platter is the baffle and the cup is the cylinder. The cup is otherwise empty, but has the driver "face"-down in the bottom of the cup with the magnet near the top of the cup.)
The interior of the cylinder is exposed to the interior of the "interior" box, and houses the driver. (i..e. the cup top and opening - opens to the interior of the interior box.)
The exterior "open end" of the cylinder is flush against the exterior of the interior box. It isn't connected via bolts or screws, but it is pushed up against the outside of the interior box rather well, AND you will use some silicone caulk essentially as a gasket here (..by "greasing" down the top edge of the cylinder). (..back to the cup and platter example: here the top "open end" of the cup has the silicone caulk applied to its "lip" edge and that edge is effectivly pushed against the outside of the interior box panel.)
Any of that make sense?
BTW, I tried to do some positive and negative impressions (to show the cement mold) with MS paint - but it turned out pretty bad.
NOTE: I called the "Tightening" washers "cut" - washers. That was a literal description, however the common name is called a LOCK washer (..and there are other washers actually called "cut" washers).
Sorry if this is redundant, but I don't recall you showing pictures of the type of binding posts you used on your speakers. I'm curious!
m0tion said:
I used Neutrik Speakon connectors from the STX range at the speaker end and locking banana's at the other:
Binding posts would have worked just as well but I thought these looked a little tidier. They also worked out a lot cheaper than decent binding posts from likes of Cardas or WBT.
Scott,
Still working through the design based on what you've proposed.
The drivers arrived today and look serious - will post a couple of pics tommorow. I've also ordered a Hypex UcD700ST and the matching PS from BMM Electronics and that should be with sometime next week. I'm also having a custom 2000VA transformer with dual 63v windings and 13-0-13v/16v aux windings done by Airlink here in the UK which should also be with me sometime next week. So the bits are starting to come together, though I suspect the box will take considerably longer 😉
Still working through the design based on what you've proposed.
The drivers arrived today and look serious - will post a couple of pics tommorow. I've also ordered a Hypex UcD700ST and the matching PS from BMM Electronics and that should be with sometime next week. I'm also having a custom 2000VA transformer with dual 63v windings and 13-0-13v/16v aux windings done by Airlink here in the UK which should also be with me sometime next week. So the bits are starting to come together, though I suspect the box will take considerably longer 😉
ShinOBIWAN said:
I think you could easily wrap your own secondary windings. I made my own from a 60VCT 1500VA transformer from Hammond by wrapping speaker wire (2 conductors = twice as easy) around the core 18 times. I ended up with +15.00,0,-14.99 Aux windings and no degredation of the 60VCT taps. You may want to use an extra winding for your extra volt. It's really easy to do.
Thanks for the tip Alex,
Airlink only charged me a few quid extra over the cost of a standard 2000VA transformer with dual secondaries.
Airlink only charged me a few quid extra over the cost of a standard 2000VA transformer with dual secondaries.
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