Inductor in series with Woofer Upgrade

I'm also considering replacing the 10mH inductors in series with the woofers in my ML ReQuests. I suspect they are over 1 ohm DC resistance. I have my eye on the Jantzen 10mH 14 AWG C-Coil Toroidal Inductors are available on Amazon that have about 0.1 ohms DC resistance.

Making this change should produce a little more volume from the woofer, tighten the grip of the amp on the woofer, change the total Q of the sealed box alignment for less ringing and hopefully improve the sound and definition available from the woofer. But I'm concerned that the design of the resistor/inductor/capacitor filter that is in parallel with the woofer would be thrown off by this change. Has anyone tried this? Any recommendations/thoughts? Thanks!

There actually are woofer tuning alignments that do better (more bass) with some series resistance.

Inductor resistance as part of bass alignment

I've read that adding resistance in series with the woofer can be used to get deeper bass (lower the f3 frequency) but it seems to me this comes at the expense of some dB loss and some impairment of the transient response.

To me leaving the stock inductor in place seems comparable to using 250 feet of 20 gauge wire as speaker cable. But if the f3 would go up to 45 hz as a result of my proposed inductor upgrade, it may be a poor decision.

I've heard the improvement in bass transient response from bypassing series inductors entirely using active crossovers and bi-amping on other non-ML speakers. I'm hoping that going to very low resistance inductors would be low expense way to get much of that benefit and improve the blend between the woofers and panels on my ReQuests.

There is no reason why you couldn't use a lower resistance inductor. It will change the operation of the crossover but that's what you want, ain't it? If you don't like the result you can experiment with various amounts of series resistance with the inductor and even match the original one. Personally I would go for slightly lower resistance (30-50% of the original value) foil coil as a starting point.

Notch Filter Impact

I'm concerned that the existing woofer crossover CLR filter is designed to remove a resonance in the existing design that would change if low resistance inductors were installed. The resonance would probably change so the filter design should too. But I don't have the expertise to design these filters.

Maybe a drastic reduction in series resistance would so drastically improve the transient response that the resonance would be sufficiently damped that no filter would be needed at all. I presume that those who use active crossovers and bi-amp are counting on that.

I guess I'll just go ahead, order the parts and give it a try.

Inductor swap & resonance filter bypass

last night I replaced the stock (1.4 ohm) 10mh inductor with a 0.1 ohm model. I figure this would throw off the tuning of the resonance filter, so I disconnected the filter. I sealed the cabinet back up and played a little music.

Sorry to say that although the bass quanity went up, the bass quality did not. I'm going to try reconnecting the resonance filter. Hope it sound good. I don't have the know how to re-design this filter to account foe the new low DC resistance inductor.

Seems to me anyone who attempts to bypass the crossover entirely and bi-amp will also be disconecting the resonance filter and will get much the same result as I did with a 0.105 ohm inductor.

Can you diagram the whole XO, so we can see what you're doing?

I am curious to see what you have read regarding the f3 also known as the resonant frequency.

Everything I have learned regarding speaker and box building suggests that the f3 is a result of physical components. IE: the speaker and the box. It is my understanding that the only way to change the f3 is to change either the speaker or the box. The electrical components make no change to the f3. There are ways to change response output via crossovers, but the f3 is still the same

Anyway, maybe I need some more education?

Dominick

f3 is the -3dB (half power) frequency, related (in a large formula) to fc, the closed box resonance frequency, in turn related to fs, the driver free-air resonance frequency.

Here's an online calculator 'new Qts with series inductor.'

This site is probably the best collection of speaker-related online calculators overall.

I would advise him against buying Jantzen inductors. I am saying this from my personal experience. I had purchased them about six months ago. In the beginning everything went well. But after six months I started getting problems. Finally I took them to “Expotus components”, their dealers in UK, to repair it. They tried their level best but were unsuccessful.