At sub frequencues, you can model the sound more as pressure than having a direction. You can orient the driver however you want, the only things that really matter is distance from front to rear of drivers and if there are throat obstructions then how big are they. Of course you have to have it forward facing or mounted in a box that forces the pressure waves to propagate in the direction you want to get desired dispersion pattern. Dipole Woofer for example has sideways woofers but opening front and back so becomes a normal dipole.
At higher frequencies though, having as side mounted driver will create a resonance. In the above mentioned example the resonance is at about 250-350 hz if I remember correctly.
Do whatever it takes to maximize the path length difference from the front of the cone and the back of the cone to your ears. A ripole or slot-loaded or W-frame (what is the difference really?) is a nice way to do this and keep the cabinet narrow. As OllBoll said, the limitation on the depth of the folds is the resonant peak that will be caused by an air mass captured in the cavity, just be sure that it is out of your passband or that you can EQ or damp it effectively.
Naturally you will want one opening facing the listening position and one facing away to make the path lengths as unequal as possible. But if that deep cabinet puts the rear opening too close to the wall you now have boundary resonance issue. And if you place your mid-high drivers right on top of this deep cabinet you have large diffraction source, affecting either the front or back wave or both.
Naturally you will want one opening facing the listening position and one facing away to make the path lengths as unequal as possible. But if that deep cabinet puts the rear opening too close to the wall you now have boundary resonance issue. And if you place your mid-high drivers right on top of this deep cabinet you have large diffraction source, affecting either the front or back wave or both.
Well it is pressure until your ear drum makes sound out of it
True
A better description would have been to mode it as a fluid or gas rather than pressure.
Thanks, yes I’ve decided that a ripole design that incorporates a baffle above for the FR Lii audio driver to be mounted is the way I’m going to go. I will use a minidsp 2x4hd to manage the Crossover/delay.
I’ve got two 12” peerless SLS drivers arriving tomorrow so I can start final stage of the design.
I still haven’t settled on how best to power the subs, I think d class is way I’ll go but where that’s a plate amp per side or a pro d class stereo power amp I’ve yet to decide. Advise happily taken.
I’ve got two 12” peerless SLS drivers arriving tomorrow so I can start final stage of the design.
I still haven’t settled on how best to power the subs, I think d class is way I’ll go but where that’s a plate amp per side or a pro d class stereo power amp I’ve yet to decide. Advise happily taken.
I'd probably look around to see what other people have used, and go from there.
If you were to start from scratch, check the operating voltage (must match original), airflow (IMO, at least half of the original, unless you're looking to run at high power for prolonged periods), and SPL rating in dB (lower is better).
Chris
If you were to start from scratch, check the operating voltage (must match original), airflow (IMO, at least half of the original, unless you're looking to run at high power for prolonged periods), and SPL rating in dB (lower is better).
Chris
Hi, following this thread because I'm considering using Ripols in a confined space. Positioning will necessitate them being placed close to a wall, 15cm probably. Is there any way to mitigate boundary resonance, like polyfill (cushion) behind speaker?
I have had that. A [Russian alnico] 15 inch driver with a slot of 18cm wide and 30 high instead of 35 cm round (1/3rd surface while Ripole is 1/9th) and a Lowther above 250Hz: why, well because I had a panel of 42cm and did not want to ruin that panel for rigidity. It worked well, great voice timbre. Too bad the whole open baffle panel, with a 15inch and a 16inch driver were too much for the interior design owner
One can have that at 90 degrees too, like said. There have been designs just like that with a steep filter at probably 150 Hz.
I don't think putting the sub against the wall and trying to damp out the resulting peaks and nulls will be feasible. Sub-bass is not easily absorbed, you would need to fill much of your room to get any significant effect!
In a small room, consider putting the dipole subwoofer at the listening position - right behind your head, or right in front of you like a little coffee table, or put a cushion on top and use it as a foot rest.
Or maybe it's best to try a monopole subwoofer. They do very well with corner or wall loading. If you room is very small, the modal region (frequencies where the room response is dominated by discrete resonant peaks and nulls) will extend quite high, maybe even higer than the sub crossover. Diople subwoofers do not have benefit in this modal region.
Thanks for your reply Tommus, the room size is 6x6x3 meter and it's my kitchen so it's best to keep the floor clear. So far I've managed to fit 60 liter speakers (Fane 12-250 tc) in between the kitchen cabinets and appliances. The speakers sound very good, but I thought they could use a bit of help in lower frequencies so I bought four Jensen RS 300 to build two compact dipole subwoofers. As the woodwork is relatively small I don't mind trying different designs.
Talking about open baffles is useless without knowing the room and the acceptable positions for the woofers.
The open baffle /dipole speaker is the oldest principle we have. Generations have listend through them.
Sometimes the wheel is reinvented, like the "Ripol" that was like making a round pancake square and calling it a new dish.
It never had any commercial significance or hurt anyone's interest, so no one raised an objection to the now expired Ripole patents.
Over the times here have been many more or less successful tries to trick the principle and improve the low response, like basket damping. From the two extremes, a simple chassis in the room to a chassis in the wall, anything was tried. As most was in pre internet times, this is all in books or magazines and long forgotten.
What has changed today are amplifier Watt, the excursion of bass chassis and the availability of frequency response modifiers like DSP, all at low cost's.
Try to build a Ripole with an 3 Watt tube amp and two +- 2mm 15" speakers from the 60th. You will not be amused in a living room.
The modified open baffle, like the Ripole or some Linkwitz constructions, to explain it very much simplified, has the idea of accelerating the air in front of the baffle. That way it will run faster than the slow rear wave and reach the listener with more energy. Later the rear wave cancels out the remains.
Interestingly, this also works the other way round, accelerating the rear wave (Dipole-Cardioid, Leo Kirchner) Quite logical if you think about it. It is all about two opposing waves not meeting, so the result at the listening place has more energy.
As I said at the start, the principle is very old. Excellent results can be had and complete fails. High power and high excursion have opened new doors. It mostly depends on the room and where you are able to place your dipole.
Remember, you will need some kind of low pass with any di- or ri-pole. Can be passive L-C or active like some Linkwitz transformation or DSP. Last is best and cheapest in the long run. If you DSP your in room measurement, you hit two targets at the same time, equalizing the dipole and your room.
These two are inseparable.
The open baffle /dipole speaker is the oldest principle we have. Generations have listend through them.
Sometimes the wheel is reinvented, like the "Ripol" that was like making a round pancake square and calling it a new dish.
It never had any commercial significance or hurt anyone's interest, so no one raised an objection to the now expired Ripole patents.
Over the times here have been many more or less successful tries to trick the principle and improve the low response, like basket damping. From the two extremes, a simple chassis in the room to a chassis in the wall, anything was tried. As most was in pre internet times, this is all in books or magazines and long forgotten.
What has changed today are amplifier Watt, the excursion of bass chassis and the availability of frequency response modifiers like DSP, all at low cost's.
Try to build a Ripole with an 3 Watt tube amp and two +- 2mm 15" speakers from the 60th. You will not be amused in a living room.
The modified open baffle, like the Ripole or some Linkwitz constructions, to explain it very much simplified, has the idea of accelerating the air in front of the baffle. That way it will run faster than the slow rear wave and reach the listener with more energy. Later the rear wave cancels out the remains.
Interestingly, this also works the other way round, accelerating the rear wave (Dipole-Cardioid, Leo Kirchner) Quite logical if you think about it. It is all about two opposing waves not meeting, so the result at the listening place has more energy.
As I said at the start, the principle is very old. Excellent results can be had and complete fails. High power and high excursion have opened new doors. It mostly depends on the room and where you are able to place your dipole.
Remember, you will need some kind of low pass with any di- or ri-pole. Can be passive L-C or active like some Linkwitz transformation or DSP. Last is best and cheapest in the long run. If you DSP your in room measurement, you hit two targets at the same time, equalizing the dipole and your room.
These two are inseparable.