Some day when I'm in a bigger room, I'll probably try a full dipole.Baffle
You should gain some improvement from both drivers on the same baffle. Just try cardboard for a quick experiment. Tweeter slightly off center, but right on the edge of the mid (not touching).
You'll need something to support the weight of the mid like a small wood frame and duct tape with the cardboard right on the floor but tilted back. Size of 30" x 31" works very well. Heard a Fostex on one - quite good sounding.
Give you an idea of the best size to shoot for, too.
Tim
You should gain some improvement from both drivers on the same baffle. Just try cardboard for a quick experiment. Tweeter slightly off center, but right on the edge of the mid (not touching).
You'll need something to support the weight of the mid like a small wood frame and duct tape with the cardboard right on the floor but tilted back. Size of 30" x 31" works very well. Heard a Fostex on one - quite good sounding.
Give you an idea of the best size to shoot for, too.
Tim
>Reduced efficiency would be bad. I don't know what the effect of increased Q would be for an open baffle with a tube amp behind it.
=====
This driver already has a highish Q, so driving it with a OPT pushes it audibly higher, though how much depends on its actual output resistance. If too much, then the baffle width can be adjusted to roll it off, assuming it's not so high that even the bare driver isn't too wide.
=====
>When you say 'where', you mean the location on the cone surface, right? Do you glue the rings on? Or do they just sit on the surface of the cone? Or behind the cone?
====
Correct. For ones that require damping near/at the surround, I mount in over the driver. For the center of the driver I suspend it over the driver using wood dowels or brass rods.
At minimum, wide BW drivers need to have their basket legs and motor damped.
====
>The low end XO will be active. I'm planning 4th order L-R at 500Hz or so.
====
I meant the mid/HF XO.
====
>Hmm, a fullrange would allow me to use the FT17H as a supertweeter like it's meant to be used. The Fostex fullrangers are quite a bit more expensive though...
====
'Penny wise and pound foolish' to my way of thinking since a bunch of good quality XO parts isn't cheap, then of course there's the sonic impact of them.......
GM
=====
This driver already has a highish Q, so driving it with a OPT pushes it audibly higher, though how much depends on its actual output resistance. If too much, then the baffle width can be adjusted to roll it off, assuming it's not so high that even the bare driver isn't too wide.
=====
>When you say 'where', you mean the location on the cone surface, right? Do you glue the rings on? Or do they just sit on the surface of the cone? Or behind the cone?
====
Correct. For ones that require damping near/at the surround, I mount in over the driver. For the center of the driver I suspend it over the driver using wood dowels or brass rods.
At minimum, wide BW drivers need to have their basket legs and motor damped.
====
>The low end XO will be active. I'm planning 4th order L-R at 500Hz or so.
====
I meant the mid/HF XO.
====
>Hmm, a fullrange would allow me to use the FT17H as a supertweeter like it's meant to be used. The Fostex fullrangers are quite a bit more expensive though...
====
'Penny wise and pound foolish' to my way of thinking since a bunch of good quality XO parts isn't cheap, then of course there's the sonic impact of them.......
GM
Here's what I'm listening to now (just one channel, the other box is being veneered):
Pretty similar in concept to what 5th Element has built. Putting the drivers on a baffle certainly helped, things sound a lot cleaner now.
Any advice about driver positioning? I'll try the tweeter directly above the midrange too, but that'll put it above my listening height. Also, if I offset the drivers horizontally, do people usually keep the tweeters on the outside or the inside? The outside seems to make sense, the tweeter should be further away to get the path lengths closer to each other, but maybe there are other considerations?
An externally hosted image should be here but it was not working when we last tested it.
Pretty similar in concept to what 5th Element has built. Putting the drivers on a baffle certainly helped, things sound a lot cleaner now.
Any advice about driver positioning? I'll try the tweeter directly above the midrange too, but that'll put it above my listening height. Also, if I offset the drivers horizontally, do people usually keep the tweeters on the outside or the inside? The outside seems to make sense, the tweeter should be further away to get the path lengths closer to each other, but maybe there are other considerations?
Baffle
That's the ticket.
I would definately keep the tweeters to the inside and offset as you have them.
The roll-off will be determined from the shortest dimension from woofer around the edge of the baffle, so on the outboard side it looks to be only a few inches. I would try adding cardboard "wings" angling backward maybe 10" on either side. Wavelength at 500 Hz is about 2.25 ft, so you will need half that from woofer to baffle edge, even if folded back around a corner, or 13.5" total. Too long and you may get some reflection off the inside surface though. Any coloration, try fabric such as felt inside.
Tim
That's the ticket.
I would definately keep the tweeters to the inside and offset as you have them.
The roll-off will be determined from the shortest dimension from woofer around the edge of the baffle, so on the outboard side it looks to be only a few inches. I would try adding cardboard "wings" angling backward maybe 10" on either side. Wavelength at 500 Hz is about 2.25 ft, so you will need half that from woofer to baffle edge, even if folded back around a corner, or 13.5" total. Too long and you may get some reflection off the inside surface though. Any coloration, try fabric such as felt inside.
Tim
Baffle
From the viewpoint of an ideal placement, there is much written about using formula to determine location and thus reduce diffraction, the Golden Rule most common.
Frankly, I not sure which is best or that I can clearly hear a big difference, but I have seen the measurements and there does seem to be something to it. You might flip the baffle over and try it upside down, tweeter inside. This would mean left and right sides swapped and then inverted, mid on top.
The other matter is the phase difference from time alignment (front to back) of the all units. The tweeter output will arrive first, followed by mid, with the woofer and sub way back. Some people seem more sensitive to phase differences, and time alignment is important. I can say that those systems which I have heard that were time aligned to some extent, sounded better. I think it virtually impossible to keep alignment constant through the full spectrum, but it can be improved.
Try moving the sub cabs slightly closer, start with a foot closer than the bass cabs/OB, which corresponds to ~80 milliseconds.
Tim
From the viewpoint of an ideal placement, there is much written about using formula to determine location and thus reduce diffraction, the Golden Rule most common.
Frankly, I not sure which is best or that I can clearly hear a big difference, but I have seen the measurements and there does seem to be something to it. You might flip the baffle over and try it upside down, tweeter inside. This would mean left and right sides swapped and then inverted, mid on top.
The other matter is the phase difference from time alignment (front to back) of the all units. The tweeter output will arrive first, followed by mid, with the woofer and sub way back. Some people seem more sensitive to phase differences, and time alignment is important. I can say that those systems which I have heard that were time aligned to some extent, sounded better. I think it virtually impossible to keep alignment constant through the full spectrum, but it can be improved.
Try moving the sub cabs slightly closer, start with a foot closer than the bass cabs/OB, which corresponds to ~80 milliseconds.
Tim
That tweeter is on the outside now, it's the left channel speaker. I'll try flipping the baffle around and put it on the inside, I'll also try the tweeter under the woofer, and wings. I'm all for time alignment, but I'm not sure how much effort I want to put into it. I have the midrange - tweeter offset entered into my SW crossover model. For the others, even at 500Hz, the wavelength is about 2' like you said, so I'm not sure how much I should worry about a few inches. And at 60Hz (the woofer - sub crossover), even more so. Anyway, I can experiment with adjusting those delays electronically relatively easily, since I'll have active crossovers at those points. The Linkwitz Labs website has a lot of information on such circuits. All of that falls under my long-term tweaking and fine tuning plans.
Alignment
Time alignment is pretty complex and best done with an active xover and a built-in delay feature, if you have one or wish to build it.
Problem is the delay varies with each driver and with frequency, so setting the tweeter back 2" or something only works for a very narrow band of a few hertz. I have done a few experiments and can detect some improvement with varying physical offset, but the real answer is driver and freq dependent, and must be done with the crossover.
The room is also a factor. With the tweeter inside, try toeing the speakers heavily inward so they are actually firing at a space 12" in front of your nose. You will hear more direct vs reflected sound, and the tweeters are rotated back a bit (in time). With OB it won't quite be the same, but it will take some of the room out of the equation.
Tim
Time alignment is pretty complex and best done with an active xover and a built-in delay feature, if you have one or wish to build it.
Problem is the delay varies with each driver and with frequency, so setting the tweeter back 2" or something only works for a very narrow band of a few hertz. I have done a few experiments and can detect some improvement with varying physical offset, but the real answer is driver and freq dependent, and must be done with the crossover.
The room is also a factor. With the tweeter inside, try toeing the speakers heavily inward so they are actually firing at a space 12" in front of your nose. You will hear more direct vs reflected sound, and the tweeters are rotated back a bit (in time). With OB it won't quite be the same, but it will take some of the room out of the equation.
Tim
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.