Is this is a homework question?

I will give you a hint, the parallel LC filter will act like two series-connected variable resistors whose values vary with frequency. Since they are placed directly across the speaker B110 the output resistance of the circuit will vary with frequency (which will alter the overall frequency response of the speaker)

The formula's are simply the X_C and X_L formulas for impedance.

Hello Jack Of All Trades,

This is not homework! I am 58 years old and graduated with a degree in Computer Science.

I am designing a two-way monitor. One goal is to have the flatest frequency response possible. I think what you said was this is a type of notch filter. Why would different sized drivers (same manufacturer), in different air spaces, be using the same values?

Lee

Jack of all trades, or anyone.....

can you please reply to mrjacobanderson1981@gmail.com . I have been trying to find a way to power dc car audio with a genorater powering 120v ac amplifiers. They will be powering two 15" phoenix gold subwoofer 650watt rms each 4ohm DVC. And another amplifier to power two 3ways mids/tweets 150watt max 4ohm SVC.

That is being installed in a uhall style boxvan, its a e350 ford econoline 5.8 v8 1ton with a 16x8x8 box. this will be my toy hauler for atvs. but I want a high spl level system to fill volume since this will be played in the sand dunes.

My first avenue, I bought 1600watt rms subs amp and a 850watt rms amp. But they are car audio amps, and powered off the cars 12v system and the alternators 85amp max output is about 300 amps off. I tried calling around for altornater help but I would need an insaine about of alternators to supply my amperage at engines idle since thats when I would be playing the loud music.

So I want a generator 120v ac powering 120v ac concert style amplifiers. One sub amp one mids amp, Im also told Ill need a power conditioner downstream from the genorater. Also a small mixer to plug in ipod computer cdplayer ect... to feed the tunes to the amplifiers. I already bought the 15" car subs and would like to use them with the 120v amplifier, and the subs are 650watt but this is car so id assume thats 650wattsRMS/12vDC=54.1amp and if I used 12vAC is the math as simple as switching the 12vDC for 120vAC and the amperage being 5.4amps??? or is there complications in the ac source powering dc speakers?

Questions.

what watts genorater would i need for 2000watt RMS of speakers.

can I power any (home or car 120vAC or 12vDC) speaker as long as i follow ohm rules from the amplifier minimums (dont go lower decimal number ohms then amp spec for)

You know Jack... I forgot to thank you.

The "hint" you gave me was valuable all on its own! It would help me to discuss this further.

Lee

Since this is a KEF design, I will presume that this is a speaker crossover network. Going from left to right and presumably from amplifier to speaker: The first L/C pair is your 12db/Oct low pass filter network. The next network is what's called a Zobel network. (I may have misspelled that.) It is an RLC notch filter. (R=inductor resistance very important) It should be added when one chooses to allow frequencies to be permitted in or near the speaker and cabinet's resonant frequency. At the resonant frequency a speaker will be considerably more efficient in coupling the electrical energy into the air. Since this boost in efficiency of the driver itself cannot be changed, the crossover is made less efficient for these frequencies.

Hi Redfred,

Thanks. I thought that a Zobel network was always 1 capacitor and 1 resistor (not a coil)... am I wrong?

Thanks,

Lee

To be 100% accurate a Zobel network is an image impedance matching network. Wikipedia has a very good but confusing for speaker implementation description at http://en.wikipedia.org/wiki/Zobel_network

A better example and explanation how a Zobel network is used in this speaker can be found at http://users.ece.gatech.edu/~mleach/ece4445/downloads/zobel.pdf

You will notice the matching network in the middle contains an inductor, resistor, and capacitor in series. I'm certain that the "parasitic" resistance of the KEF inductor is not an insignificant hundredths of an ohm. The gauge of the wire was selected to intentionally provide this series resistance.

It just dawned on me, the Zobel network of just a capacitor and resistor will be much more frequently found on tweeters and mid range drivers where the desired lowest frequency just touch the driver's resonant frequency. So the cross over network will stop lower frequencies. This is a Zobel on a woofer that frequencies lower than the resonance are still desired.

Hello Fred and Jack,

I will not be able to respond further until July 5th or 6th (long trip back to the US).

So... for now... thank you all very much.

Lee

With due respect to the other good answers you've had, the circuit could only be meaningfully analysed with details of the impedance of the driver - "nominal impedance 8Ω" or whatever doesn't really help.

I came across this many years ago (in the 60's/70's) when the B110 was state-of-the-art. I built a couple of infinite-baffle cabs using 1½" cast concrete (with weldmesh reinforcement) - weighed about 60lbs each. Fitted them with 10" circular drivers, pending getting the full low-down on the B110s & integrating them with my "Ultimate System" (which is still on the drawing board ).

Sadly, I never did get the full info for the B110s, and had to abandon the cabs in a rapid enforced house move about 3 years ago .

I know this is unhelpful waffle, but the point I'm getting round to is that I have looked into it, and the full characteristics of the LC circuit shown can't really be analysed without including the load impedance (and a few Rs). KEF don't appear to publish any figures .

Good luck.

John,

When it comes to woofers, the back pressure that a cabinet generates can and will change the effective impedance of the speaker. So a "free space" impedance curve will only give a designer a starting point. To properly match a driver and cabinet, one should frequency sweep and test the impedance of the speaker assembled in the cabinet. Because the cabinet changes this curve, a few driver manufacturers will not publish impedance curves for their woofers.