ESl speakers - why no cabinet?

[El Zombre]

Just curious: if one problem with ESL speakers is bass response due to cancellations from rear waves, why not build a box for the ESL speakers? Isn't that what a box is for? I'm baffled. (*rimshot* ... sorry.)

[bshaw147]

We could but the cabinet would be very large and most think it would be unattractive in any room.

[audiotony]

You would lose the advantage of the speaker being a dipole line source.

[El Zombre]

Thanks for the responses so far and forthcoming.

And what is the advantage of a dipole line source?

Thanks,
D

[audiotony]

look here for more info on advantages and disadvantages: wikipedia.org/wiki/Electrostatic_speaker

Although I never tried 'boxing in' my electrostatic speakers, I would think you will lose some transparency as well.

[bshaw147]

With any cabinet you will have resonances to deal with.

A dipole source can be good in combination with a beam splitter, you could just use the back wall corner behind the speaker. The reflected waves will combine with the front waves. This can in most cases cause destructive interferences (in the low end) but help support mids and highs.

To isolate the back from the front without the use of a cabinet try making a baffle, what you mount the cell into much much larger then the cells driven area.

happy building
bry

[El Zombre]

I guess looking into the disadvantages of a box would have answered my questions somewhat.

Thanks again, all.

[Calvin]

Hi,

ElZombre You have to distuinguish between a working principle (ESL or dynamic speaker) and the way the membrane is coupled to the surrounding air.
Basically there´s nothing to say against putting an ESL into a cabinet, since it works like a mass-spring-system, similar to the dynamic speaker! This has been done for example by Beveridge.

But while the mass of a dynamic speaker is relatively large, the mass of a ESL-diaphragm is very small. So apart from ridicoulously low membrane tension (low spring rates) the ESL would show high Fs-values. Its lower Bandwidth limit would be too high --> no bass.
The Alternative would be to lower the spring rate of the cabinet, which means more volume and larger size and leads to other practical problems.

The very thin membrane is acoustically transparent over the complete audio frequency range. So any reflection coming from within the cabinet would pass the membrane without any attanuation. A reflection-free cabinet would have to be very deep (think of the Nautilus-concept of Bowers&Wilkins). Anyway the cabinet for a ESL would have to be built different than that for a dynamic speaker and it would have to be impractically large.

Since a ESL cannot develop as much power per area of membrane unit like a dynamic speaker, its membrane area must be larger to achieve the same acoustic power. A large membrane though is clearly advantageous when it comes to the degree of coupling to the air. The ´energy-transfer´of a large membrane to air is far better than that of a small membrane. The typically small membranes of a dynamic speaker are so mismatched to the surrounding air that it needs a cabinet to beef up (match) the performance. ESL membranes can be of a size and shape that allows ideal coupling to the air. So no cabinet at all is needed with regard to this point.

A open system suffers from acoustic phase cancellation which reduces the bass level. Again the ESL counters this by large membrane area and its shape. Using dynamic speaklers you need as well large membrane areas, which is why most open baffle speakers use multiple bass drivers.
The open baffle alters the distribution character, i.e. the way sound energy is spread over the room. This leads to a different, typically very precise and ´boomless´ and natural sounding bass that suits the exceptional qualities an ESL is capable in the mid-and high-frequency range very well.

You could place the ESL in a cabinet and gain something, but you would loose on other things. So in this ´compromise-game´ most designers opt for the open system.

jauu
Calvin

[MJ Dijkstra]

Hi,


I once put a very large sewer pipe (cut across its length) behind the esl. This way, I created a small enclosure with non-parallel walls with open ends at top and bottem. Some BAF wadding was used as well. Despite being open, this killed bass. I quickly removed this enclosure. I didn't experiment any further with enclosures as they probably will become unacceptable large.
I've heard someone build a quad57 in a wall with the room behind acting as an enclosure and that would sound great.

[inertial]

Hi,

http://www.janszenloudspeaker.com/

interesting hibryd

Cheers,

Paolo