15 litre box stuffed should give a "Q" of 0.85
F3 of about 48Hz
Of course I'm going to say that 2 woofers is better, I nearly always do
F3 of about 48Hz
Of course I'm going to say that 2 woofers is better, I nearly always do
TheSeekerr:
That's the path I was intending to take, though I'd probably use a 8", or two 🙂
I'm intrigued about your system.... do share the results..
regards
Meraj
That's the path I was intending to take, though I'd probably use a 8", or two 🙂
I'm intrigued about your system.... do share the results..
regards
Meraj
merajsalek said:
You obviously have a larger desk than I do - if I put speakers with baffles big enough to hold 8" drivers on my desk, I'd have about enough room left over for a single A4 page.
This problen needs a different solution, put a sub box on the floor under your desk and you can have all the bass you want, send the rest of the signal to the smaller speakers, the computer desk I'm sitting at has a pair of Cerwin Vega 124's on the floor under it.
If I'd known of this problem I would have offered you a couple of small 8inch J***** that "may" have worked in a small sealed box given your ability with electronics to do the crossover and the transform circuit,
If I'd known of this problem I would have offered you a couple of small 8inch J***** that "may" have worked in a small sealed box given your ability with electronics to do the crossover and the transform circuit,
Sorry mates,
I obviously misunderstood...
I was talking about what Ted just suggested - a separate, under the desk, subwoofer....my desk space is just as small and I've got GAF to consider as well....that's why I'm planning to go coaxial... I put that in my older post..
http://www.diyaudio.com/forums/showthread.php?postid=1638880#post1638880
My choices are either sealed or a dipole sub....but i have a loooong way to go in terms of knowledge before I can pull it off..
I obviously misunderstood...
I was talking about what Ted just suggested - a separate, under the desk, subwoofer....my desk space is just as small and I've got GAF to consider as well....that's why I'm planning to go coaxial... I put that in my older post..
http://www.diyaudio.com/forums/showthread.php?postid=1638880#post1638880
My choices are either sealed or a dipole sub....but i have a loooong way to go in terms of knowledge before I can pull it off..
Hi Ted,
I'm afraid that wouldn't have worked in my situation. I thought about it for ages, but there's simply not enough room under the desk.....it's got drawers to the floor that take up most of the room underneath it, and the remainder is taken up by a rubbish bin and my legs. Yes, a sub could probably fit where the bin is, but since the desk is primarily for the purpose of doing work on, the bin is rather necessary.
That said, another alternative does exist....moving my current system from my bedroom down to my electronics worktable, which would give substantially more room. Actually, I might clear off that table and do that today.
Incase you hadn't worked it out, I haven't yet moved out of home (I'm only 18), so these limitations are firm but temporary, since I'll probably move out within a year or two.
Hi, merajsalek,
The solution I was proposing was a "very nearfield" compromise solution, very much like a pair of miniature Aethers. The solution Ted has suggested, a proper woofer in a small sealed box and linkwitz transformed, can be done very well, provided that it is crossed low. The solution I was proposing had the "woofer" close to the midrange, thus minimising localisation effects and allowing it to be crossed fairly high.
I would suggest reading through http://sound.westhost.com/project73.htm , which describes a PC "Hi-Fi" system using a Linkwitz Transformed 8" and a pair of small 3" satellites. The same scheme could easily be adapted to using dipole satellites, but you may run into problems around the crossover point if you're using small baffles, since they roll off after about 250-300hz, and you'd probably want to cross over to the sub no higher than 150hz. Of course, adding wings, making the baffle bigger, active dipole equalisation and whatnot can all solve that particular problem.
Chris
I'm afraid that wouldn't have worked in my situation. I thought about it for ages, but there's simply not enough room under the desk.....it's got drawers to the floor that take up most of the room underneath it, and the remainder is taken up by a rubbish bin and my legs. Yes, a sub could probably fit where the bin is, but since the desk is primarily for the purpose of doing work on, the bin is rather necessary.
That said, another alternative does exist....moving my current system from my bedroom down to my electronics worktable, which would give substantially more room. Actually, I might clear off that table and do that today.
Incase you hadn't worked it out, I haven't yet moved out of home (I'm only 18), so these limitations are firm but temporary, since I'll probably move out within a year or two.
Hi, merajsalek,
The solution I was proposing was a "very nearfield" compromise solution, very much like a pair of miniature Aethers. The solution Ted has suggested, a proper woofer in a small sealed box and linkwitz transformed, can be done very well, provided that it is crossed low. The solution I was proposing had the "woofer" close to the midrange, thus minimising localisation effects and allowing it to be crossed fairly high.
I would suggest reading through http://sound.westhost.com/project73.htm , which describes a PC "Hi-Fi" system using a Linkwitz Transformed 8" and a pair of small 3" satellites. The same scheme could easily be adapted to using dipole satellites, but you may run into problems around the crossover point if you're using small baffles, since they roll off after about 250-300hz, and you'd probably want to cross over to the sub no higher than 150hz. Of course, adding wings, making the baffle bigger, active dipole equalisation and whatnot can all solve that particular problem.
Chris
Chris;
You beat me to it, that was going to be my next post, remember you can fit a sub almost anywhere provided the sound is OK, under the bed even, but for nearfeild listening you small "Eathers" would probably be a good solution.
You beat me to it, that was going to be my next post, remember you can fit a sub almost anywhere provided the sound is OK, under the bed even, but for nearfeild listening you small "Eathers" would probably be a good solution.
Chris,
I've seen that ESP project and it was one of the main inspirations for my solution...mine would be "very nearfield" too
So far, i've got this:
Electronics (not overly relevant other than the XO/EQ):
USB tube DAC> active OB EQ> active LR4 (150Hz perhaps)> transform> gainclones
Speaker
Sats: Passive XO (LR1 would be nice - I understand very little of passive XO tho :-( ) > Winged baffle, a la Linkwitz PMT1> side stuffing
Sub: At the moment it looks like a sealed one....
I've seen that ESP project and it was one of the main inspirations for my solution...mine would be "very nearfield" too
So far, i've got this:
Electronics (not overly relevant other than the XO/EQ):
USB tube DAC> active OB EQ> active LR4 (150Hz perhaps)> transform> gainclones
Speaker
Sats: Passive XO (LR1 would be nice - I understand very little of passive XO tho :-( ) > Winged baffle, a la Linkwitz PMT1> side stuffing
Sub: At the moment it looks like a sealed one....
merajsalek: Take any advice I give with the appropriate amount of salt, given that my knowledge is based on a lot of theory and almost no practice. That said:
A sealed sub is the most forgiving, sounds better than ported (IMHO) (at the cost of frequency extension), and if you wanted, you could use something like the Marchand WM8 "BASSIS" module, which is basically a variable Linkwitz Transform, which would allow you to whack almost any driver in any box, use WinISD to calculate the Fs and system Q, and then tweak the "Adjusted Fs" knob as far as you can before the drivers limitations become apparent.
If you haven't dropped the cash on access to MJK's models pages yet, I highly recommend them, so you can model some midranges on baffle and see what comes out. With active 6dB/octave EQ with poles at 300hz and 10hz, you shouldn't have any trouble reaching 150hz to cross active LR4. Even power handling shouldn't be a big concern....since one octave below 300hz is 150hz, and an LR4 would be 6dB down at that point, you should find that your EQ doesn't actually add more than about 5dB at any frequency.
Erm.....there's no such thing as an LR1 crossover, since LR's are, by nature, cascaded 2nd order filters. I think you meant 1st order Butterworth. I too know very little about passive crossovers, but since the box design plays almost no role at those frequencies, you may be able to yoink that part whole from an established design.
Ted:
Almost anything would be an upgrade from the ported bookshelf speakers I'm using currently.....if I can work out a design that will reach 80z or so, that'd be low enough to cross to a sub under the bed, although phase issues worry me with putting a sub behind the listening position. I don't really want to pour a whole heap of money into a compromise solution, though, so I'll put off doing a sub until I can do it properly. (The drivers I was looking at using for that are the JBL GT5-12's....car audio drivers, but the ones I've seen have been very well built, and JBL's specifications are fairly honest).
(does it show that I've been thinking about all this for a while? 😛)
A sealed sub is the most forgiving, sounds better than ported (IMHO) (at the cost of frequency extension), and if you wanted, you could use something like the Marchand WM8 "BASSIS" module, which is basically a variable Linkwitz Transform, which would allow you to whack almost any driver in any box, use WinISD to calculate the Fs and system Q, and then tweak the "Adjusted Fs" knob as far as you can before the drivers limitations become apparent.
If you haven't dropped the cash on access to MJK's models pages yet, I highly recommend them, so you can model some midranges on baffle and see what comes out. With active 6dB/octave EQ with poles at 300hz and 10hz, you shouldn't have any trouble reaching 150hz to cross active LR4. Even power handling shouldn't be a big concern....since one octave below 300hz is 150hz, and an LR4 would be 6dB down at that point, you should find that your EQ doesn't actually add more than about 5dB at any frequency.
Erm.....there's no such thing as an LR1 crossover, since LR's are, by nature, cascaded 2nd order filters. I think you meant 1st order Butterworth. I too know very little about passive crossovers, but since the box design plays almost no role at those frequencies, you may be able to yoink that part whole from an established design.
Ted:
Almost anything would be an upgrade from the ported bookshelf speakers I'm using currently.....if I can work out a design that will reach 80z or so, that'd be low enough to cross to a sub under the bed, although phase issues worry me with putting a sub behind the listening position. I don't really want to pour a whole heap of money into a compromise solution, though, so I'll put off doing a sub until I can do it properly. (The drivers I was looking at using for that are the JBL GT5-12's....car audio drivers, but the ones I've seen have been very well built, and JBL's specifications are fairly honest).
(does it show that I've been thinking about all this for a while? 😛)
Sealed sub is what I have in mind, prefer to use Rod Elliot's approach for the Transform.
Not sure about 'MJK's models pages', pls enlighten
Yup, a 1st order 6dB/oct is what i had in mind... 😀
Not sure about 'MJK's models pages', pls enlighten
Yup, a 1st order 6dB/oct is what i had in mind... 😀
http://www.quarter-wave.com/Models/MathCad_Models.html
Excellent tools for modelling the performance of a driver in OB, U frame, H frame. Only thing it won't model at the moment is our electrical equalisation, which is a little bit annoying - hopefully, since he's planning to build an active system himself, he'll add capacity for dipole equalisations and linkwitz transforms at some point.
$25US for access to any model and updates for a year, with a gentlemen's agreement that you'll stop using them or re-pay the fee after a year.
I paid just before the dollar went through the floor, but it's climbing back a little....
Looking at the frequency response of that Vifa, the tweeter looks to roll of quite high, about 9dB an octave from 6khz.....I don't have the tools to model the suggested crossover to see what it's supposed to do, but I'm having trouble seeing how it could work. I guess you could build it and find out! At any rate, I don't think you're going to find it possible to do a 1st order acoustic rolloff, since it's already steeper than that, and the woofers response takes a dive at about 2k....not very far, but it's pretty ugly nonetheless.
Excellent tools for modelling the performance of a driver in OB, U frame, H frame. Only thing it won't model at the moment is our electrical equalisation, which is a little bit annoying - hopefully, since he's planning to build an active system himself, he'll add capacity for dipole equalisations and linkwitz transforms at some point.
$25US for access to any model and updates for a year, with a gentlemen's agreement that you'll stop using them or re-pay the fee after a year.
I paid just before the dollar went through the floor, but it's climbing back a little....
Looking at the frequency response of that Vifa, the tweeter looks to roll of quite high, about 9dB an octave from 6khz.....I don't have the tools to model the suggested crossover to see what it's supposed to do, but I'm having trouble seeing how it could work. I guess you could build it and find out! At any rate, I don't think you're going to find it possible to do a 1st order acoustic rolloff, since it's already steeper than that, and the woofers response takes a dive at about 2k....not very far, but it's pretty ugly nonetheless.
Could this help?
Graham Maynard's thread 'T'-bass drive for OB LF drivers - http://www.diyaudio.com/forums/showthread.php?s=&postid=1646500
Graham Maynard's thread 'T'-bass drive for OB LF drivers - http://www.diyaudio.com/forums/showthread.php?s=&postid=1646500
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