Playing with cheap line array is fun!

[5th element]

EVEN THOUGh the distortion is probably lower in your OB LA, you do have to make sure that the level of the two speakers is exactly the same. Very small increases in dB can make one speaker sound clearer over another. Crank the fisher and see if that makes any difference. PLus the open baffle is not going to hurt here.

[BAM]

As for the dipole woofer you mentioned, one of the drivers is out of phase with the other, so the cones are actually moving in opposite directions when DC is applied. The end result is that any sort of nonlinearity in the motor and suspension structure of the woofers is cancelled out, lowering distortion further. So, that's how that works. Go to PartsExpress.com and buy the paper-cone Pioneer 15" woofers with foam surrounds. Those have a Qts of 0.7, which makes them perfect for an application like this because the suspension already provides the sound of a Qtc 0.7 (theoretically ideal) sealed box, when used in free air. Then build a version of the Phoenix dipole woofer, crossover at about 200 Hz, and you'll have your dipole bass.

[JinMTVT]

ok isee now!
so the drivers are connected 180 degree so that on the same side they both pull but one from the front and one from the rear.

i guess that they aren't using this for nothing, so the improvements should be there!

any grpahs for response of this kind of setup VS sealed or TL type enclosure?
any number on distortion levels VS enclosed type subs?

do you think that this kind of setup would work up to 500hz
with a good sub?

[rcavictim]

Originally posted by JinMTVT
ok isee now!
so the drivers are connected 180 degree so that on the same side they both pull but one from the front and one from the rear.

i guess that they aren't using this for nothing, so the improvements should be there!

any grpahs for response of this kind of setup VS sealed or TL type enclosure?
any number on distortion levels VS enclosed type subs?

do you think that this kind of setup would work up to 500hz
with a good sub?

No, I think 500 Hz is too high a crossover point for a woofer package like this where there are chambers involved that exceed 1/4 wavelength in size (~6") and the part of the driver cone that radiates these is not in line-of-sight with the listener, or time aligned with the other mid driver(s).

[FrankWW]

What I guess I was thinking about, and not clearly, is that the frequency response varies with distance - as in 'get close enough to the Fisher and it will sound like the LA'

[JinMTVT]

ok i did more linstening today ..lots of it
( hey hey,isn't the point of all our efforts to listen to music?

well, at equal volume, both loudspeaker don't sound quite the same.

one problem i have in discerning the particular sound of each system is that the Fisher does resolve stuff under 150hz pretty good, where the LA doesn't at all

was expected with the poor drivers + dipole used in the LA

Since i am far from an experienced listener, please don't take too seriously the following points ..

At first, the LA seemed alot more articulate than the fisher, in resolving complicated sounds ( trumpets, multiple voices timbres same time .. )
this effect has now lessen with each listening and the equalization in volume between both system

When doing AB with mono output ( using balance fader in software ) i can point a few differences but cannot clearly determine wich one as the best redering of the audio.

The LA is realy missing in 10KHZ+ definition , of course the Fisher uses a tweeter and a 2" mid-high drivers thus getting more resolution in that 10KHZ+ range ..

the mids seems to be better on the LA
strong and fast

Sensitivity on the LA is really high, as high as half gain+ 3/4 volume control on software = ear piercing highs!!
kinda dangerous though ..ahha



Going back to dipole operation ..

I have read ( again ) today lots of pages including Linkwitz's on dipole systems and line array ( line sources ) loudpseakers

From what i understood, open end dipole operation
( wich a sufficient front baffle size) seems to be the best way to get low distortion and high quality sound reproduction?
even when used with subs it seems to perform excellently quoting a few of the users in here.

Why aren't more commercial units using this design?

I mean, why when we think of speakers, we see an enclosure?
I guess than the box is a way to control the rear wave, but why then suddently ( since a few years i guess?? ) dipole config seems to be "a la mode" in the audio diy world?

Does it really provides a better way of reproduction musical content than conventional enclosed driver? ( assuming that equal quality drivers are used )

then, would a system as i just did for testing, but using high quality materials provide an even better solution?

quoted from Linkwitz site :

...Vertical height of the sound stage adds to its realism. I find small 2-way speakers very unsatisfactory in this respect, even when they are correctly positioned at ear level height. ...

An added advantage of tall sources is their relatively large radiating surface area, which means small excursions and, therefore, progressively lower non-linear distortion for a given maximum sound level. The low distortion aspect is even more important, than sound stage height, wide angle horizontal dispersion and uniform power response. Low distortion means increased dynamics and clarity, and the ability to play back at near live levels without listener strain. It brings the naturally occurring distortion mechanisms of the ear into play, which are necessary elements for creating an illusion of reality.
Sensitivity can be high. A line with 25 identical drivers connected in series-parallel to obtain the same combined impedance as that of a single driver, will have 14 dB higher SPL for the same voltage applied.
Stored energy is not necessarily low because of the many cabinet and driver chassis cavities.

I would encourage more investigation of line sources for use in very large venues, as for public address or entertainment speakers. For typical domestic environments they are unnecessarily large. Today, the same low distortion sound pressure levels can be obtained from far fewer drivers and without the image distortion.

This means ( if he is right, and i assume he is for now )
that more drivers = less distotion in the sound producing operation? is it because of the distributed area thus requiring less
movmement from each individual drivers to produce the same total loudness??

Then if he really meant to say that the only disagvantage to line sources are:

- image distortion
-are unnecessarily large

i guess i could live up with those 2 things pretty good


this is only my humble comments ...

[LS]

Hi,

Some side 'wings' will lower FR > an octave.
Flat Baffle Ft{F of transition from dipole to Two 2Pi Radiators}
is ~ 6780 / (Width / 2), Lambda/2 from center to edge.

"U" Baffle is ~ 6780 / (Width + Depth) {SL}
Sides ~= (W / 3) has about a +3db peak @ Ft. and
then drop -6db/oct lower.

LS

[JinMTVT]

could you rephrase that in more "simple" terms

like, non audio-tech wise terms?

[johninCR]

My friend, Dmiti has some good info on his site about OB line arrays. They can image very well, you just need a concave baffle. Check out http://www.geocities.com/dmitrynizh/labaffles.htm

JinMTVT, if you have an unlimited supply of drivers, then you can do dipole bass too with those cheap little drivers. You need to use alot of them and there's some special considerations that must be taken into account when loading below the resonant frequency (Fs) of a driver. The the case of the ones you have, the Fs is probably 80-100hz.

My next array project will be an adjustable baffle, which will go from straight to various concave degrees to suit different listening situations and of course "wings" on hinges.

Regarding wings, see Dmitri's example for adjustable wings. For yours, add a 10" piece of wood to the back or side and 5" on the other side and the sound will be much fuller, but still a little thin.

Regarding sensitivity: You get 3db more output every time you double the number of drivers. You also pick up some sensitivity going to OB because the back wave energy is put into play instead of disipating in a box.

Dipoles aren't popular for mass marketed speakers because you can't get dipole bass nearly as cheaply as you can make boxed bass.