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Yes. I have not forgotten this question, and I've actually been looking for the answer to this. Dan Wiggins explained this in the Adire Audio "Woofer Speed" white paper. Here it is - summarized:

Mass isn't the problem - inductance is. So if you want faster transient response, ignore that moving mass parameter that some manufacturers push - look at the inductance! And if they don't list the inductance, ask yourself why - is there something they don't want to show? Inductance is the key to driver transient response - ask for it when transient response comes up!​

Additionally - measuring the same cabinet with and without a series inductor showed me that while the inductor "does what was intended" in flattening the response, it does so by cutting everything down to a level that is lower than the low point in the passband response already.

Adding a series inductor cuts transient response.

Adding a resistance cuts efficiency.

I'd rather avoid the downsides to this approach, it is better to design a different cabinet or use a different driver.

Use a line-level crossover.... you avoid putting anything in series with the driver and you have MUCH more design flexibility.


Kevin Haskins
Exodus Audio
 

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This was more in reference to the practice of adding a series inductor to smooth the ripples in a tapped horn passband, as was done in the example in the first post of this thread. I just couldn't remember the exact source that said why that was a bad idea, turns out that it was the Wiggins paper on woofer speed.

I agree that active crossovers eliminate a lot of problems. They only really create one - the need for lots of amps (and the space to put them!).
 

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This was more in reference to the practice of adding a series inductor to smooth the ripples in a tapped horn passband, as was done in the example in the first post of this thread. I just couldn't remember the exact source that said why that was a bad idea, turns out that it was the Wiggins paper on woofer speed.

I agree that active crossovers eliminate a lot of problems. They only really create one - the need for lots of amps (and the space to put them!).
I'd take Wiggins paper with a grain of salt. It is true of course but it isn't necessarily relevant to sound quality.

You need an amp to drive a sub anyway.... so may as well use an active line-level network. ;-)

Kevin Haskins
Exodus Audio
 

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Discussion Starter #165
that would be nice, but considering all the work buddy did with this project... it's quite obvious that this driver isnt meant to be used in a th.
I dunno what you base that on; it came out not far from the modelled when measured. It's not an optimum solution, but far from unworkable and better than many, unless you want to provide a set of specs to Eminence and stump up the required amount for a minimum order (25 drivers IIRC).
 

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Discussion Starter #166
Adding a series inductor cuts transient response.

Adding a resistance cuts efficiency.

I'd rather avoid the downsides to this approach, it is better to design a different cabinet or use a different driver.
I missed this earlier; transient response is a higher frequency range issue than for a sub. If the inductor is sized correctly it will not allow the driver to slew insufficiently for it to meet it's upper BW requirement, in this case 60hz or so. The added resistance of 0.25Ω of the ERSE inductor I used in the early posts will lower efficiency a fraction of a dB, and as power is cheap, and the design is excursion, not power limited it's fairly moot.
 
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