Thanks for your input! Good to hear someones doing something similar, it seemed like such a simple yet effective idea but not having heard if it done much I was worried there were issues with sand filling. Those JBL drivers look really nice too 
Would you say that the fibreglass material is more effective than studio foams? They are both much heavier than BAF type material (which used alone hasn't proved very effective). The enclosure narrowing toward the rear will make it a requirement to have quite a long passage inside, so I can get a good fill of whatever material I use. Do you think that the curvature and random wavy cuts will help with rear wave control a lot? They are to do with diffusion rather than absorbtion, but they should reduce parallel faces and cut down on the resonances they cause?
I can leave barces when cutting the laminate layers inside the mid cab. Since I plan these to be 1-2" thick layers cut from wooden beam the braces will probably need to be "swiss cheesed" from the side too. Should be interesting anyhow
Would you say that the fibreglass material is more effective than studio foams? They are both much heavier than BAF type material (which used alone hasn't proved very effective). The enclosure narrowing toward the rear will make it a requirement to have quite a long passage inside, so I can get a good fill of whatever material I use. Do you think that the curvature and random wavy cuts will help with rear wave control a lot? They are to do with diffusion rather than absorbtion, but they should reduce parallel faces and cut down on the resonances they cause?
I can leave barces when cutting the laminate layers inside the mid cab. Since I plan these to be 1-2" thick layers cut from wooden beam the braces will probably need to be "swiss cheesed" from the side too. Should be interesting anyhow
Dunno about fibreglass as I won't use it. Irritates the hell out of my skin. Cotton waste works very well and is quite cheap. There may be toher good locally available options in the link I posted above; read the coefficients and compare.
Re: rear path length. My MT box will be an MTM. Behind the individual mid drivers there will be a slightly narrowing 'pipe'. At the rear of the enclosure it will have reflectors to direct the wave 180* to the side and top/bottom (space behind compression driver) so the total path length one way will be between 50 and 70cm or so.
Perhaps use the space behind your tweet to do something similar rather than fill the large volume with sand totally.
Re: rear path length. My MT box will be an MTM. Behind the individual mid drivers there will be a slightly narrowing 'pipe'. At the rear of the enclosure it will have reflectors to direct the wave 180* to the side and top/bottom (space behind compression driver) so the total path length one way will be between 50 and 70cm or so.
Perhaps use the space behind your tweet to do something similar rather than fill the large volume with sand totally.
The stuffed "TL" certainly works well, though that system will be replaced shortly due to the failure due to leakage of my HD3Ps 
I don't have the room for running OBs, so have never tried them in that application, but my suspicion is that they would perform admirably. The other possible solution I've considered would be a Nautilus style terminated pipe, though I haven't tried it in practice yet. Stay tuned in the next six months though.
I don't have the room for running OBs, so have never tried them in that application, but my suspicion is that they would perform admirably. The other possible solution I've considered would be a Nautilus style terminated pipe, though I haven't tried it in practice yet. Stay tuned in the next six months though.
Pinkmouse: Shame about the HD3Ps, after a look around the web it does appear that they all eventually go that way. I hope to have a good experiment with HM100’s and cabs to see which works best. Not sure if I can go fully OB due to enquiring fingers plus lack of space. I did have an idea of making it with an open rear frame so that grilles can be attached on the side/back to offer some protection, but also allow for some stuffing to absorb the rear wave. Saying this I ‘should’ be building amps and bass cabs!
Dr.EM: besides the increase in sensitivity did you notice any change in the perceived sound by using two over one HM00’s?
Dr.EM: besides the increase in sensitivity did you notice any change in the perceived sound by using two over one HM00’s?
The overall depth of this midrange box should be no more than 37cm in order to assure it doesn't overhang when placed on top of the woofer box (which I also have some new plans for ). This limits the depth of that internal enclosure to mabye 30cm. Can I get enough of a fill in there to control the rear wave do you think? Heavy, dense materials at the back should help a great deal and with the curved back and wavy sides any reflections should have to take a much longer journey to get back to the driver, hopefully being absorbed enough by this point.
The other option is as mentioned to use the space behind the tweeter. It would be much more difficult to construct and I'm not sure it'd help much but it could be done (see even worse diagram!).
Running 2 drivers made no real difference to the sound, mabye sounds a bit "bigger", due perhaps to an altered polar pattern.
). This limits the depth of that internal enclosure to mabye 30cm. Can I get enough of a fill in there to control the rear wave do you think? Heavy, dense materials at the back should help a great deal and with the curved back and wavy sides any reflections should have to take a much longer journey to get back to the driver, hopefully being absorbed enough by this point. The other option is as mentioned to use the space behind the tweeter. It would be much more difficult to construct and I'm not sure it'd help much but it could be done (see even worse diagram!).
Running 2 drivers made no real difference to the sound, mabye sounds a bit "bigger", due perhaps to an altered polar pattern.
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Dr EM you are making it too complicated. Path behind the drivers should simply be direct to the rear, with a 90* reflector to the tweet side. The a small horizontal traverse to the tweet side parallel to the rear wall with another 90* reflector that points the sound towards the rear of the tweet itself. Progressively denser fill the further away from the midbass drivers. There needs to be one internal divider between the midbass and tweet that runs most of the way to the rear (maybe 75%) and two 90* reflectors on either side in the RH and LH rear corners of the enclosure. Total 3 pieces of wood. I can't draw a pic, but think of it in terms of relectinf light (sound) with the rear of the midbasses being the light sources.
I think this is what your describing (keeping a sand fill). Haven't drawn the stuffing but imagine its there
Would the reflectors be wood or would adding a hard material like a ceramic tile help? I suppose the frequencies to be reflected are low enough not to need an especially hard reflector? Do you think this will work better than my original cabinet diagram with a straight path and curved back? This will create I longer path I guess, so potential to absorb more rear wave.
Would the reflectors be wood or would adding a hard material like a ceramic tile help? I suppose the frequencies to be reflected are low enough not to need an especially hard reflector? Do you think this will work better than my original cabinet diagram with a straight path and curved back? This will create I longer path I guess, so potential to absorb more rear wave.
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Much closer. Make the centre divider shallower, and the corner reflectors need to be deeper: sound will reflect sraight back the the driver on the LHS. Again, use the light and mirror analogy.
Don't bother with the ceramic tile, I don't think it'll do much.
Stuff the first couple of inches with polyfil and the rest with something denser as suggested before.
Don't bother with the ceramic tile, I don't think it'll do much.
Stuff the first couple of inches with polyfil and the rest with something denser as suggested before.
I got some decent sized offcuts of 12mm MDF which I may attempt to build into this internal midrange chamber using just a jigsaw and straight edge . We'll see how that goes
Will keeping the diffusion help even with your design Brett? Although the sound should be swallowed up by the absorbant material I still feel all those parallel edges won't help with resonances? In particular the (not seen on diagram) tops and bottom.
. We'll see how that goes Will keeping the diffusion help even with your design Brett? Although the sound should be swallowed up by the absorbant material I still feel all those parallel edges won't help with resonances? In particular the (not seen on diagram) tops and bottom.
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My HM100Z0's have arrived and been listening to them for a couple of days on a make shift open baffle. They work very well like this and sound cleaner and more open than my current Seas CB17RCY/P in a well constructed (sand fill walls etc.) cab. Apart from the frequency response not being as flat as it could be with a normal box design, this is def. worth a try as it so quick and simple to experiment with. When I get time (hopefully within the next week) I’ll try the damped TL to see how it compares.
and been listening to them for a couple of days on a make shift open baffle. They work very well like this and sound cleaner and more open than my current Seas CB17RCY/P in a well constructed (sand fill walls etc.) cab. Apart from the frequency response not being as flat as it could be with a normal box design, this is def. worth a try as it so quick and simple to experiment with. When I get time (hopefully within the next week) I’ll try the damped TL to see how it compares.
The open baffle is .7m from the rear wall and 0.7m from the nearest side wall and I've placed a piece of foam about 20cm behind the driver to dampen the rear wave slightly. IMHO the room seems to be making less of a difference OB. I only got 2 as was unsure of spending so much on an experiment, plus I got the general impression that stocks were v.low.
Where did you get yours from, stocks are indeed very low as far as I can tell!
I tried cutting some panels for the internal mid box as per the latest diagram. Didn't go well using the jigsaw and straight edges. I decided it'd be smart, since I needed 2 identical panels, to clamp them together and cut both at once. Thickness is only 24mm total but during cutting the first straight the blade progressively bent such that the bottom cut ended up 5mm out and not at all straight. Don't know why this should be but I kind of gave up at that point. I may need at least a circular saw?
Other than that, will my original box idea be much worse? It can be made much more easily if I can find suitable wooden beams but the "line length" if we treat this as a TL is about half (32cm). Treated as a sealed box the volume is much more appropriate. I guess the overall aim is to absorb as much as possible which is the intention of utilising the extra space in the first place, but even the shorter line should absorb most content over 400hz with suitable damping materials?
I tried cutting some panels for the internal mid box as per the latest diagram. Didn't go well using the jigsaw and straight edges. I decided it'd be smart, since I needed 2 identical panels, to clamp them together and cut both at once. Thickness is only 24mm total but during cutting the first straight the blade progressively bent such that the bottom cut ended up 5mm out and not at all straight. Don't know why this should be but I kind of gave up at that point. I may need at least a circular saw?
Other than that, will my original box idea be much worse? It can be made much more easily if I can find suitable wooden beams but the "line length" if we treat this as a TL is about half (32cm). Treated as a sealed box the volume is much more appropriate. I guess the overall aim is to absorb as much as possible which is the intention of utilising the extra space in the first place, but even the shorter line should absorb most content over 400hz with suitable damping materials?
I got mine from IPL acoustics.Dr.EM said:
I've cheated and got the bulk of my cutting done at B&Q, they can get funny about doing loads of cuts but I went a few times and spread out the amount of cuts. Then i use butt joints with a little overlap and use a router with a flush bit to finish the edge.
I guesstimated about the same for down to 300hz, although my quick and dirty cross over is at 4th order at 400hz as it doesn't seem happy below this.
I did find this which appears to be using the tappering stuffed TL method.
Going to try and get some wood cut next week to test a TL. Right off to do some more gluing on the bass cabs.
Here is what I may end up doing for the midrange. It is basically my initial idea but with the "line" coming to more of a point. Looking at the sound in terms of light again, the sound should be scattered in random directions having to take a long route through much absorbant materials before ever reaching the cone again. The diffusion will be made of more random cuts, I just copied and pasted each side for ease of drawing. Also, each layer will be different.
The shaped part is a beam (hopefully 120mm width by 1-2" thick) shaped with the jigsaw (I've done this before and it gives a good result without taking ages to make so many layers as in laminate construction). The outer is just MDF panels to keep it together and obviously top and bottom will be required. Hopefully this is non critical enough that I can use the jigsaw to cut my spare bits down (make careful use of the machined straight edges).
Out of interest, which part of the UK are you in mazdapowered?
The shaped part is a beam (hopefully 120mm width by 1-2" thick) shaped with the jigsaw (I've done this before and it gives a good result without taking ages to make so many layers as in laminate construction). The outer is just MDF panels to keep it together and obviously top and bottom will be required. Hopefully this is non critical enough that I can use the jigsaw to cut my spare bits down (make careful use of the machined straight edges).
Out of interest, which part of the UK are you in mazdapowered?
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Sorry to triple post but it's nice to see some real progress .
I got the timber and started work this afternoon. Got a suprisingly long way with it too, its quite a fast method of construction. In the photo another 2 layers are needed under the holey brace so 4 are either side (the brace is mainly there to make up overall height but probably isn't a bad idea anyhow).
Once the other 2 layers are made, a normal MDF box is constructed around all the layers; then the whole assembly sits in the larger overall box surrounded by sand
.I got the timber and started work this afternoon. Got a suprisingly long way with it too, its quite a fast method of construction. In the photo another 2 layers are needed under the holey brace so 4 are either side (the brace is mainly there to make up overall height but probably isn't a bad idea anyhow).
Once the other 2 layers are made, a normal MDF box is constructed around all the layers; then the whole assembly sits in the larger overall box surrounded by sand
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I'm in Chippenham Wilts, your quite welcome to pop round and have a listen to my work in progress. Just PM/email me.
Nice to see some good progress, I've seen similiar construction of the wavy sides, interested to see how that works out.
Are you going to give it a try before you go for the full sand fill around it, to see how it sounds?
Nice to see some good progress, I've seen similiar construction of the wavy sides, interested to see how that works out.
Are you going to give it a try before you go for the full sand fill around it, to see how it sounds?
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