Designing a dipole in a sealed enclosure

[ttan98]

I like to design a dipole with 2 full range drivers(each driver has 4ohm) mounted back to back and wired them in series and out of phase. Both of the drivers are mounted on a sealed enclosure. I think that would make the setup a dipole instead of a bipole.

If I have only a single driver on a sealed enclosure the capacity is about 4litre to give me a -3dB of about 90Hz. If I increase to 2 drivers do I double the capacity or still remain at 4litre to give me the same bass roll off.

Anyone who has experience in this area please response.

[madtecchy]

will you be using your dipoles with a sub woofer??

[ttan98]

Originally Posted by madtecchy

will you be using your dipoles with a sub woofer??

Yes

[CLS]

In such case, the air in the box is not compressed/stretched as the cone motion as in normal sealed boxes. Some air flow would be there among the baskets... etc, locally. The volume may have some effect in being a load (as mass) on the cones, thus changing the fs of the system somewhat. But it's never the way like a normal sealed box.

The frequency response is still dominated by the system Q and dipole loss.

[planet10]

Originally Posted by ttan98

If I have only a single driver on a sealed enclosure the capacity is about 4litre to give me a -3dB of about 90Hz. If I increase to 2 drivers do I double the capacity or still remain at 4litre to give me the same bass roll off.

If you wire as a bipole you will get the same bass. If you wire as a dipole (with or without separate cabs) you will get no bass.

dave

[Pan]

Originally Posted by planet10

If you wire as a bipole you will get the same bass. If you wire as a dipole (with or without separate cabs) you will get no bass.

dave

If the same volume is used for two drivers instead of one the response will change. The response will be as if each driver was mounted in 2 litres.


/Peter

[planet10]

Originally Posted by Pan

If the same volume is used for two drivers instead of one the response will change. The response will be as if each driver was mounted in 2 litres.

2 liters per driver or 4, because the drivers are wired out of phase there will be no bass.

dave

[Pan]

Dave, if you put one or two drivers in the same box volume you will get different results, both in frequency response and various kinds of distortion.

If you wire the drivers in opposite polarity you get a dipole bass.

Saying that you get the same bass in case one and no bass in case two is simply wrong.


/Peter

[Keriwena]

Peter, consider how big a speaker would have to be for a dipole effect.

Even an 8 litre cabinet will be a point source at low frequencies. The air won't know there are two drivers if you wire them out of phase, it'll just think you're using a very thick cone. Thus, the effect will be nearly the same as one driver in free air - no bass.

Otherwise, yes, if you use two drivers you need to double the size of the box because you have twice the cone area and that doubles the Vas.

[Patrick Bateman]

Originally Posted by ttan98

I like to design a dipole with 2 full range drivers(each driver has 4ohm) mounted back to back and wired them in series and out of phase. Both of the drivers are mounted on a sealed enclosure. I think that would make the setup a dipole instead of a bipole.

If I have only a single driver on a sealed enclosure the capacity is about 4litre to give me a -3dB of about 90Hz. If I increase to 2 drivers do I double the capacity or still remain at 4litre to give me the same bass roll off.

Anyone who has experience in this area please response.

If you skip the box you'll get more efficiency at certain frequencies, since there will be points in the frequency spectrum where the radiation from the rear of the cone will sum in phase with the radiation from the front of the cone. Check out "The Edge" from Tolvan. (Google it)