Will a Linkwitz transform...transform the driver?

[AllenB]

Horn parameters more significant than driver parameters....that may be the salient point.

Could the LT be used to allow a smaller vented box to be used? Noting that the vented box is 4th order, could I take a transfer curve of the desired and actual responses and shave this off, retaining the desired transient response or better?

[Shaun]

I think you should not restrict yourself to "Linkwitz Transform", as this describes a very specific application. "Equalisation" is probably more suitable, as it is more generic, not being limited to a specific filter type.

Keep in mind that below the port resonance the driver quickly runs out of excursion, so any boost applied here must be chosen judiciously.

Check out this article. Active Equalization of Loudspeakers. It uses SoundEasy loudspeaker design programme but the discussion is, I believe, relevant to what you seem to be contemplating.

[AllenB]

OK, reading that now. First thoughts though are that I expect a LT, when it undoes a rolloff, to also undo the phase response.

[Shaun]

It certainly affects the phase response, yes. "Undo" is not really what it does. I guess one can say that it provides a complimentary compensation (i.e., equalisation) but, again, only over a limited range.

[richie00boy]

It transforms the phase response to what the chosen Q represents. Regarding your idea on the vented box, you may be able to achieve something but it will be difficult to work out and usually shrinking the box size in a vented design means you end up with a port too big to fit inside the box without some serious woodworking skills.

[kipman725]

phase response shouldn't matter apart from at crossover points or if so extreme a large group delay results. The only way I know of for correcting group delay is by delaying the signal to the other speakers by an equal amount using a computer/dsp.

[Shaun]

No. Group delay is a function of the phase reponse. Read this .

[speaker dave]

Originally Posted by kipman725

ESP - The Linkwitz Transform Circuit

it's just an EQ curve which is the inverse of a closed box speakers roll off so allows the speaker to operate with flat frequancy response at lower frequancys. It does nothing to the actual speaker just changes the input to the speaker.

This was the right answer to the original question. the Linkwitz circuit (or the KEF Kube) does nothing to change the parameters of the woofer, it is just a precise method of "undoing" the combined (woofer and box) response you have, and replacing it with a desired response. You haven't changed the parameters of the woofer and placing that woofer in a new box will get you a different response that the EQ will no longer suit.

If I recall correctly, horn drivers need to be low mass for bandwidth and high Bl. You can still use a "wrong" woofer and equalize the result, but the needed EQ won't have anything to do with what EQ worked for the sealed box.

Here is a question for the real experts out there: lets say we use negative output impedance to lower the effective Q of the woofer. Would that transfer from box to box? Can we add external network components to simulate higher mass? Will that transfer from box to box?

David

[bjorno]

Originally Posted by speaker dave

..Here is a question for the real experts out there: lets say we use negative output impedance to lower the effective Q of the woofer. Would that transfer from box to box?..

Hi David,

Yes it would.

Can we add external network components to simulate higher mass? Will that transfer from box to box?

Yes but how effective depends on the driver in use among other aspects. See:

ACE-bass amplifier design

and

Enclosure for high Q driver

b

[speaker dave]

Originally Posted by bjorno

Hi David,

Yes it would.



Yes but how effective depends on the driver in use among other aspects. See:

ACE-bass amplifier design

and

Enclosure for high Q driver

b

Ah, yes, ACE Bass. I had forgotten about that. A clever way to "transform" the woofer.

Note that at the woofer terminals, the acoustical response of a woofer to an electrical input doesn't change. Still, the amplifier/woofer combinations do make the woofer appear to have different parameters and react accordingly when placed in different cabinets.

Regards,
David