Lowering the crossover point.

Thanks GM, I never thought about considering the outside of the box as an issue. I guess my idea of a spherical concrete orb sub is not a great idea? :)

Quote:

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Originally Posted by aditya

Yes GM, the BL data particularly seems to be in what unit, W/M ?

'n' is also pretty close.

Actually these readings were taken at around the same time when Thiele's papers were published in the AES journals, and I am sure but not able to recollect now, that these measurements were taken either by Thiele himself or somebody pretty well known in the industry. I am still searching for the source where I had found it.

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My notes are gone, but I want to say weber/meter, but I find no such conversion nor newton/amp for that matter.

'n' ? what's this?

It was a Prof. Ashley and I got them from the late Bill Eckle via the local Altec distributor way before the WWW became available to the masses and is still available on his website in memorium: ASHLEY

GM

Quote:

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Originally Posted by VolvoHeretic

Thanks GM, I never thought about considering the outside of the box as an issue. I guess my idea of a spherical concrete orb sub is not a great idea?

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You're welcome!

This is a whole different 'kettle of fish'! 'Sound is Round', so if sound is radiating around a sphere, there are no eigenmodes in its size pass-band and even these are radiating away at such a steep angle, they dissipate very quickly, so little chance of comb filtering with the driver's output.

The driver of course is flat, relatively speaking, so it will have these strong eigenmodes if some sort of deflection or damping ring isn't used like is seen on some 'FR' drivers.

Harry Olson's early measurements shows how various shapes affect dispersion:

GM

edit: Hmm, looks like the forum rescaled them to uselessness. Do I need to post them elsewhere or did I miss something in uploading them?

Cool! Thanks!

GM

Quote:

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Originally Posted by GM

My notes are gone, but I want to say weber/meter, but I find no such conversion nor newton/amp for that matter.

'n' ? what's this?

It was a Prof. Ashley and I got them from the late Bill Eckle via the local Altec distributor way before the WWW became available to the masses and is still available on his website in memorium: ASHLEY

GM

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Yes....weber/meter it is, used to be used earlier. 'Newton-per-Amp' is the same as 'Tesla-meter'. But I had just plugged a standard value to try the driver out, and finally found a value which had made the sim-ing work.

By 'n' I meant 'eta', for efficiency.;)

Another 'yes' for you as usual, for the info about the source of the t/s parameters. Many thanks.

Regards
Aditya

Quote:

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Originally Posted by aditya

Put the piston dia at 12.58 inch. And repeat the Vas measurements with different weights, and note the results. Choose weights to shift Fs between 15% to 40%, and note the changes in the readings. It takes some effort to get the correct data for Vas.

Also take a 'in-box' impedance reading. This will help.

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Yeah when measuring the VAS piston area (cone/dust cap) will always be in cubic inches.So when trying to figure the correct data to enter you are essentially trying to figure the total piston area in cubic inches.. And adding the correct weight does take some effort..

VAS methods

1. Added Mass
2.Known Box

Measuring Loudspeaker Driver Parameters

Quote:

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Originally Posted by Altec Best

Yeah when measuring the VAS piston area (cone/dust cap) will always be in cubic inches.So when trying to figure the correct data to enter you are essentially trying to figure the total piston area in cubic inches.. And adding the correct weight does take some effort..

VAS methods

1. Added Mass
2.Known Box

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Hi AB,

I think it is a typo....area in cubic inches ?

Probabely you were talking about the "Known box" method, where the space (cubic inches) in the spkr front is also added to the known volume box in consideration.

Actually Cradeldorf is doing it in the open-air fashion... for the time being probabely.

CD,
you can put the cursor on the graph at the frequency you want, and this little box will pop up showing the the precise impedance at that frequency.