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Calvin 6th February 2007 08:42 PM


well I could easily measure the difference :D and even more...its clearly audible imo in that way that with the linesource You can walk through the room and You have the impression of a more constant loudness. Especially when You aproach the source (nearfield conditions) the difference becomes very obvious, because the linesource doesn´t get louder but it is indeed getting softer. Of course won´t You measure the complete theoretical +3dB, but the difference is there.

As Brian already pointed out, it is relatively easy possible to get linesource conditions for the bass. Its just a matter of the height of the speaker and the floor-ceiling-distance.

I had for example the problem of very serious roommodes in vertical direction that made listening nearly impossible. The typical small dipole bass wouldn´t help here even when it was already better suited to the room than other basses. The solution came when I built the bass-tower. It very obviously excites the vertical modes far less.
And while the bass is not beaming like the higher freqs, You can clearly hear and measure the dipolar distribution character.
And I must say I´m most happy that this ´antiphase sound is causing a lot of trouble´ :D :D :D ...I´m spending now too much time in front of them listening and just having one goosebump after the other :-)


@MJ.....Are these personal assumptions or do you have any experience with well built dipol basses? ;)

MJ Dijkstra 7th February 2007 12:04 AM


Originally posted by Calvin

@MJ.....Are these personal assumptions or do you have any experience with well built dipol basses? ;)


Nice one!

I just wanted to make clear that the theories describing the propagation of sound are based on a theoretical model which has nothing to do with domestic conditions. Of course my style of writing is a bit incisive, provoking some discussion here, so don't take it personal.

I have built around four pairs of full range dipole esls. 1,85 to 2,0 meter high. So not from floor to ceiling (almost none of the esls I've seen are from floor to ceiling, except some 240 cm high ESLs build by Fikier which doesn't fit in his new house with its lower ceiling). The response of one of the largest ESL was measured and showed a suck-out between 100 and 200 Hz roughly. I have listened for many years to this speakers. They had their obvious strengths but the suck-out was annoying; most of all after switching from headphones to the ESLs which I frequently did. Some of the warm Fender sounds simply dissapeared in case of the ESLs. I have seen similar behaviour in the measurements of large Final1.2 ESLs.

Calvin 7th February 2007 09:33 AM


don´t worry MJ....a bit of provocation livens up an otherwise boring thread sometimes. I like that ;)

The suckout prob is really a matter of any open baffle. With my hybrid I have to correct just slightly for this effect by letting the HP-filter have a bit more gain, but without correction it sounds a bit thin (together with the ´wings´ beeing ~45cm wide the cancellation starts at ~600Hz).
The folded shapes for the woofers behave differently as You can see from the measurements below.
Thats what I like about this system. You don´t need to equalize very much, thereby conserving a large dynamic headroom for the panel and the dipole sub fills up the rest of the spectrum nicely to the lower freqs. Sonically I can´t hear any transition artifacts between bass and panel. It sounds like a fullranger ESL, but without the tendency of thinning and with considerably greater efficiency and dynamics. And the size of the system isn´t that different to a big FR-ESL. either ;)


MJ Dijkstra 7th February 2007 01:31 PM

Hi Calvin,

Sounds interesting!
What's the lowest frequency you get with the dynamic dipole?
What power do you need at that frequency?
Don't you have some problems (suckout) when placed closed to the backwall?

Best regards, MartinJan

Calvin 7th February 2007 07:52 PM


the 6.5" drivers I use have an free air Fs of ~42Hz that sinks after build-in down to 35Hz. I need a slight bass boost that I realize with a subsonic filter in the active crossover. With the parameters of this boost You can fudge a bit with the lower cutoff freq, but You can reach 30Hz without equalizing and stressing the drivers too much.
I drive them with a 100W amp and wire the 8 drivers per side to give >8 Ohms since the amp is rather an 8Ohm design. The amp is nearly able to drive the speakers to full excursion and efficiency of the system fits nicely to the second amp driving the ESL. Still I intend to build some more powerful D-amps in nearer future to have more reserves (clipping etc).

I didn´t test placing the towers close to the backwall, since they should stay in close proximity to the panels and I wouldn´t place those close to a wall anyway.


Zombie 9th February 2007 07:35 AM

Save yrself trouble these:

You won't be dissapointed...

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