Hi
I'm to build a pair of SFW woofer (I have 4 of them laying about) based HT towers. The overall system design is dictated by the drivers I happen to have on hand, and amplification available to me.
I've been thinking and reading up on the forum, and the consensus seems to be that towers are BAD. However I do not want the bulk and spread of a separate sub, so I've been thinking of dumping all my surplus into a pair of nice boxes.
Speaking of which, I had a completely 'non-paralleled walls' design in mind. One where no wall is parallel to each other, and use of internal dividers that chop the tower into little boxes adhering to the double/multiple rules.
Unfortunately I have no clue where to start, as I do not have access to design and measurement tools, or the driver parameters. I normally work by rule of thumb: Biting my thumbnails off and hoping it will work. I use approximate volume measurements, and to make matters really simple, do not port the boxes - sealed cabs with lots of stuffing.
I have also been thinking of a 'Cone' design with the front and back walls parallel, and the other two angled, narrow at the front but widening toward the back.
What are the relative merits and demerits of such a design, and how do the two above? I will obviously not be able to unparallel the top and bottom walls - The poor thing has to stand.
Right now I have a nice unpressed 12" paper cone woofer and a 5 1/2 inch whizzer cone woofer that seems to top off at about 8 KHz, and a really good Philips 1" Silk dome tweeter that can take about 20 WRMS and goes all the way up to 30 KHz or so. All of this will be actively crossed over and amplified. For the time being I could look at a biamp arrangement but will evolve into full blown actively amped system.
I will be using crossovers from Marchand Electronics, at 133 HZ for the 12", and 6 KHZ for the mid/bass unit. I have lots of amps. An HK PM 665 100 WRMS/ch. for the bass, a homegrown STK 4191 4-ch. amp (which is now to move into a new home with new transformers and on a proper PCB - P2P is too messy for so many pins for the mid/high channels. Options are available - a 30 w/ch. TDA 2030a bridge amp, a 60-wattx4 NEC receiver, and I can also whip up a nice TDA 7294 bridge amp in case of emergency.
I'm to build a pair of SFW woofer (I have 4 of them laying about) based HT towers. The overall system design is dictated by the drivers I happen to have on hand, and amplification available to me.
I've been thinking and reading up on the forum, and the consensus seems to be that towers are BAD. However I do not want the bulk and spread of a separate sub, so I've been thinking of dumping all my surplus into a pair of nice boxes.
Speaking of which, I had a completely 'non-paralleled walls' design in mind. One where no wall is parallel to each other, and use of internal dividers that chop the tower into little boxes adhering to the double/multiple rules.
Unfortunately I have no clue where to start, as I do not have access to design and measurement tools, or the driver parameters. I normally work by rule of thumb: Biting my thumbnails off and hoping it will work. I use approximate volume measurements, and to make matters really simple, do not port the boxes - sealed cabs with lots of stuffing.
I have also been thinking of a 'Cone' design with the front and back walls parallel, and the other two angled, narrow at the front but widening toward the back.
What are the relative merits and demerits of such a design, and how do the two above? I will obviously not be able to unparallel the top and bottom walls - The poor thing has to stand.
Right now I have a nice unpressed 12" paper cone woofer and a 5 1/2 inch whizzer cone woofer that seems to top off at about 8 KHz, and a really good Philips 1" Silk dome tweeter that can take about 20 WRMS and goes all the way up to 30 KHz or so. All of this will be actively crossed over and amplified. For the time being I could look at a biamp arrangement but will evolve into full blown actively amped system.
I will be using crossovers from Marchand Electronics, at 133 HZ for the 12", and 6 KHZ for the mid/bass unit. I have lots of amps. An HK PM 665 100 WRMS/ch. for the bass, a homegrown STK 4191 4-ch. amp (which is now to move into a new home with new transformers and on a proper PCB - P2P is too messy for so many pins for the mid/high channels. Options are available - a 30 w/ch. TDA 2030a bridge amp, a 60-wattx4 NEC receiver, and I can also whip up a nice TDA 7294 bridge amp in case of emergency.
Lots of info - unclear questions....
I'll have a go at the "cone" cabinet design question:
Possible disadvantages with your cabinet design are:
*They may look a little strange (most non-parallel side wall boxes taper in rather than out toward the back) but hey, you may revolutionise cabinet aesthetics!
*Its a lot harder to make walls that join each other on angles, depending on what sort of equipment you have.
*If you are going sealed and fully stuffed, then having non-parallel walls is probably not so important, but still beneficial of course.
You can unparallel the top and bottom easily by putting baffles inside the unit, but given the fairly small areas of the top and bottom this may not be worth while.
Assuming that you are having a separate mid enclosure, then it may be a lot easier to have some non-parallel walls in this, as the mid is where you will have problems with standing waves.
For design software you can get Boxcad or Winisd for free on the net. However if you are going sealed, then the equations are pretty simple and you can calculate recommended volumes using a calculator or spreadsheet. Its worth buying a good book (eg The loudspeaker design cookbook) to get you going, as its hard work getting the whole picture off the net.
Mick
I'll have a go at the "cone" cabinet design question:
Possible disadvantages with your cabinet design are:
*They may look a little strange (most non-parallel side wall boxes taper in rather than out toward the back) but hey, you may revolutionise cabinet aesthetics!
*Its a lot harder to make walls that join each other on angles, depending on what sort of equipment you have.
*If you are going sealed and fully stuffed, then having non-parallel walls is probably not so important, but still beneficial of course.
You can unparallel the top and bottom easily by putting baffles inside the unit, but given the fairly small areas of the top and bottom this may not be worth while.
Assuming that you are having a separate mid enclosure, then it may be a lot easier to have some non-parallel walls in this, as the mid is where you will have problems with standing waves.
For design software you can get Boxcad or Winisd for free on the net. However if you are going sealed, then the equations are pretty simple and you can calculate recommended volumes using a calculator or spreadsheet. Its worth buying a good book (eg The loudspeaker design cookbook) to get you going, as its hard work getting the whole picture off the net.
Mick
I agree with sangram. You will need a separate mid enclosure to prevent the bass impacting on your mid-bass unit.
There isn't any point then in having the bass enclosure with non-parallel sides if you're crossing over at 130Hz but this would be advantageous for the mid enclosure which would be inside the box and therefore out of sight. Don't forget to take the mid enclosure's outer dimensions into account and allow for this when you calculate the volume required for the bass. I would be inclined to go for sealed boxes for the 12" paper coned woofer and the 5.5" mid-woofer unit. This also makes the calculations easier.
Don't over stuff the boxes as this may give a dead sound to the speakers, particularly the mid unit. Using an enclosure with non-parallel sides will result in less need for stuffing anyway.
You should be fine with the active crossovers at 130Hz and 6kHz.
I would also endorse sangram's recommendation that you buy "The Loudspeaker Design Cookbook". There are plenty of other aspects of speaker design that you can start to take into account. You've already considered minimizing the internal standing waves. There are also the issues of front baffle diffraction and cabinet panel resonances/bracing that you might want to look into. Having said that, just bunging everything into boxes as outlined should produce a pair of very nice speakers.
If your budget runs to it try coating all of the drive units with C37 lacquer. This may be considered controversial in some circles (particularly those who have never tried it) but I've found it to be an excellent way of bringing the separate drivers into a synergistic relationship, especially with 3-way speakers.
Incidentally, you don't, but for those who wish to "unparallel" the top and bottom whilst retaining a cabinet that can stand up (and hold plants on top) consider using wedges on the inside.
Have fun and keep posting.
Steve
There isn't any point then in having the bass enclosure with non-parallel sides if you're crossing over at 130Hz but this would be advantageous for the mid enclosure which would be inside the box and therefore out of sight. Don't forget to take the mid enclosure's outer dimensions into account and allow for this when you calculate the volume required for the bass. I would be inclined to go for sealed boxes for the 12" paper coned woofer and the 5.5" mid-woofer unit. This also makes the calculations easier.
Don't over stuff the boxes as this may give a dead sound to the speakers, particularly the mid unit. Using an enclosure with non-parallel sides will result in less need for stuffing anyway.
You should be fine with the active crossovers at 130Hz and 6kHz.
I would also endorse sangram's recommendation that you buy "The Loudspeaker Design Cookbook". There are plenty of other aspects of speaker design that you can start to take into account. You've already considered minimizing the internal standing waves. There are also the issues of front baffle diffraction and cabinet panel resonances/bracing that you might want to look into. Having said that, just bunging everything into boxes as outlined should produce a pair of very nice speakers.
If your budget runs to it try coating all of the drive units with C37 lacquer. This may be considered controversial in some circles (particularly those who have never tried it) but I've found it to be an excellent way of bringing the separate drivers into a synergistic relationship, especially with 3-way speakers.
Incidentally, you don't, but for those who wish to "unparallel" the top and bottom whilst retaining a cabinet that can stand up (and hold plants on top) consider using wedges on the inside.
Have fun and keep posting.
Steve
I made a whole bunch of wedges out of homosote (the 4'x8' board that is made of ground up newspapers-often used for sound control and bulletin boards) Then I stacked them to make wide wedges. I then glued them to the inside of the cabinet behind the drivers. Since I cut them sloppily, they have a rough surfaces and each triagle sticks out differently, which should help diffract/ absorb resonances. They are also quite dead, so should damp the panels they are glued onto.
I used Liquid nails for glue-nice and gooey.
I used Liquid nails for glue-nice and gooey.
here's mine
here's a spiffy cardboard mockup of the speaker that dave (planet10) is making for me.
it's going to be wall-mounted - that's why the tweeter is on the bottom (never mind the goofy tweeter enclosure, i'm going to make something nicer, egg-shaped). the walls are non-parallel such that the back is wider than the front, and the front wall is angled in. this allows for wall-mounting without having to worry too much about toe-in. hopefully 'bafflestep' will be minimal.
not that it will matter that much in my living room which is adjacent to the street with all its noise.
here's a spiffy cardboard mockup of the speaker that dave (planet10) is making for me.
it's going to be wall-mounted - that's why the tweeter is on the bottom (never mind the goofy tweeter enclosure, i'm going to make something nicer, egg-shaped). the walls are non-parallel such that the back is wider than the front, and the front wall is angled in. this allows for wall-mounting without having to worry too much about toe-in. hopefully 'bafflestep' will be minimal.
not that it will matter that much in my living room which is adjacent to the street with all its noise.
Attachments
7V said:
Actually, I meant to say kanga (not that I disagree with sangram
)It get's a bit confusing when you post as all the messages are listed backwards.
Steve
PS: I think you knew what I meant
PPS: Your homosote sounds interesting, variac. Where do you get it?
around here we can get homasote at a 'big box' builder's supply store like home depot or lowe's.
perhaps someone else knows where to find it in your neck of the woods.
/andrew - only knows what you can buy at heathrow.
perhaps someone else knows where to find it in your neck of the woods.
/andrew - only knows what you can buy at heathrow.
Wow, thanks.
That's a lot of Answers - sorry for the complex and long query. Thank to all those who replied.
I have one last question - strength. Is a box like this likely to require more bracing and stiffening than paralleled walls?
Here's the takeout I got then -
1. Constructional difficulties (I'm not gonna build 'em myself. I'm 5'7" and 50 kilos - at the age of 30. I'd probably die of exhaustion).
2. Not important for bass enclosure.
3. Aesthetical issues - one of cabinet design - this is a little tough to work around, but we shall see.
4. Parallel walls not an issue with sealed speaker - benefits in the case of a sealed bass box being obviously negligible.
5. Damping to be experimented with.
7V: I can't use C37 lacquer. Not available around here. Anyway I will be have to have a separate enclosure for the mid - the tower will be split into two boxes internally using baffles, to be able to overcome some of the issues with the basic shape of an HT tower - and to give the mid some room to breathe as it has to cover from about 150 Hz onwards - not all that easy....
faustian bargin: Nice design. Something like that, but more oddly-shaped - sort of a crooked witch's house is more like what I had in mind - not a single wall parallel to the other. Let's see... something like the drawing below - excuse the shabby lines, they've been done in MSPaint in my office PC - not the nice finished image I will finally be giving to the designer. I like the idea of using a cardboard mockup. I wil borrow the idea from you, if you don't mind.
mrfeedback - I think trapezoid still has parallel walls? The idea sounds good though - maybe some experimenting is called for.
That's a lot of Answers - sorry for the complex and long query. Thank to all those who replied.
I have one last question - strength. Is a box like this likely to require more bracing and stiffening than paralleled walls?
Here's the takeout I got then -
1. Constructional difficulties (I'm not gonna build 'em myself. I'm 5'7" and 50 kilos - at the age of 30. I'd probably die of exhaustion).
2. Not important for bass enclosure.
3. Aesthetical issues - one of cabinet design - this is a little tough to work around, but we shall see.
4. Parallel walls not an issue with sealed speaker - benefits in the case of a sealed bass box being obviously negligible.
5. Damping to be experimented with.
7V: I can't use C37 lacquer. Not available around here. Anyway I will be have to have a separate enclosure for the mid - the tower will be split into two boxes internally using baffles, to be able to overcome some of the issues with the basic shape of an HT tower - and to give the mid some room to breathe as it has to cover from about 150 Hz onwards - not all that easy....
faustian bargin: Nice design. Something like that, but more oddly-shaped - sort of a crooked witch's house is more like what I had in mind - not a single wall parallel to the other. Let's see... something like the drawing below - excuse the shabby lines, they've been done in MSPaint in my office PC - not the nice finished image I will finally be giving to the designer. I like the idea of using a cardboard mockup. I wil borrow the idea from you, if you don't mind.
mrfeedback - I think trapezoid still has parallel walls? The idea sounds good though - maybe some experimenting is called for.
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Many Different box Shapes And Sounds..
Hi Sangram,
The trapezoid box is used very much nowadays for full-range PA cabinets.
The front and rear panels, are parallel, and the side panels are narrowing from front to rear.
The top and bottonm panels are flat and parallel.
This setup works better than a rectangular prism box ime.
Another box shape is a sealed tall narrow cabinet (square or trapezoid section), and this works well for nice bass both bass augmentation and transient response, provides that the box is lined corrctly - ask me for this.
A perfectly cubic bow works well too, provided that the damping is correctly done.
All non-parallel sides is not a requirement, and adds very much to the construction cost and difficulty.
For flat wall mounting, a wide thin tall box, like a shirt box (remember those ?) has another good sound too.
Eric / - Just trying to save you trouble.
Hi Sangram,
The trapezoid box is used very much nowadays for full-range PA cabinets.
The front and rear panels, are parallel, and the side panels are narrowing from front to rear.
The top and bottonm panels are flat and parallel.
This setup works better than a rectangular prism box ime.
Another box shape is a sealed tall narrow cabinet (square or trapezoid section), and this works well for nice bass both bass augmentation and transient response, provides that the box is lined corrctly - ask me for this.
A perfectly cubic bow works well too, provided that the damping is correctly done.
All non-parallel sides is not a requirement, and adds very much to the construction cost and difficulty.
For flat wall mounting, a wide thin tall box, like a shirt box (remember those ?) has another good sound too.
Eric / - Just trying to save you trouble.
Re: Many Different box Shapes And Sounds..
🙂
I showed the rough design to my carpenter. He refused to do it.
Oh, well, He said he could do trapezoid, though - so I guess I'll be looking at that way.
Thanks for the informative post and the design possibilies. To someone like me, you have no idea how much it helps.
I just thought that a perfect cube is the worst possible design WRT standing waves? Correct me if I am wrong... But then most subwoofers I see are cubes so there's something there, can you detail out a little more why?
My local bookstore does not carry the cookbook, but can order it for me - about $70, AFAIK - more than the material cost of this pair of speakers but I guess it's a good buy - will take about three weeks.
The sealed, narrow long cabinet design would be similar to most HT towers (with the exception of sealed, everybody does put a port in), if I understand correctly? It will have a square cross-section mostly?
These speakers (12") had a shirt box shaped enclosure for their first home. Don't remember what it sounded like - I didn't listen to them for about six years.... It was not wall mounted, though. I remember they didn't sound too good - I wasn't very good at this then and made a lot of mistakes like running 40 ft of speaker cable using flat speaker wire in 22 AWG or something - but I diggress.
Thanks for all the info...
mrfeedback said:
🙂
I showed the rough design to my carpenter. He refused to do it.
Oh, well, He said he could do trapezoid, though - so I guess I'll be looking at that way.
Thanks for the informative post and the design possibilies. To someone like me, you have no idea how much it helps.
I just thought that a perfect cube is the worst possible design WRT standing waves? Correct me if I am wrong... But then most subwoofers I see are cubes so there's something there, can you detail out a little more why?
My local bookstore does not carry the cookbook, but can order it for me - about $70, AFAIK - more than the material cost of this pair of speakers but I guess it's a good buy - will take about three weeks.
The sealed, narrow long cabinet design would be similar to most HT towers (with the exception of sealed, everybody does put a port in), if I understand correctly? It will have a square cross-section mostly?
These speakers (12") had a shirt box shaped enclosure for their first home. Don't remember what it sounded like - I didn't listen to them for about six years.... It was not wall mounted, though. I remember they didn't sound too good - I wasn't very good at this then and made a lot of mistakes like running 40 ft of speaker cable using flat speaker wire in 22 AWG or something - but I diggress.
Thanks for all the info...
Re: Re: Many Different box Shapes And Sounds..
The reason that cubes work for subwoofers is that the frequency of the cube's standing waves is above the operational range of the subwoofer. This is the reason that I previously advised that having a non-parallel shape is not necessary for your bass cabinet (below 130Hz) only for the mid-bass part of the cabinet.
There are plenty of mail order outlets on the Internet. For example, Parts Express sell it for $31.95.
Steve
sangram said:
The reason that cubes work for subwoofers is that the frequency of the cube's standing waves is above the operational range of the subwoofer. This is the reason that I previously advised that having a non-parallel shape is not necessary for your bass cabinet (below 130Hz) only for the mid-bass part of the cabinet.
sangram said:
There are plenty of mail order outlets on the Internet. For example, Parts Express sell it for $31.95.
Steve
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