crossover experts please help

[back]

this is the bass section of my speaker crossover.

http://www.infinity-classics.de/mode..._crossover.jpg

i want to drive the woofer active but the two voice coils

don`t work prallel.

i don`t fully understand how it works but i think

that if i remove all components from the 4 ohm coil and keep

in place the 2 ohm coil parts and feed it with <200hz 4th order crossed over

signal it will work.

i found the 200hz at the speaker`s specs.

i can make some tweaking but i want to know that miimum impedance

won`t go crazy and i end up with a fried amp.

what you guys think?

george.

[speaker dave]

This is a little messy because of the Watkins woofer configuration. That was an Infinity exclusive that gave some bass extension via a secondary voice coil driven in a narrow bandpass mode.

Here is some information on the Watkins woofer: http://www.davidsaudio.com/Infinity_...ummary0001.pdf

I think your best bet is to keep the Watkins part as is and keep the woofer inputs strapped together as your circuit diagram shows, then you should remove some of the low pass filtering of the non-Watkins part.

The 2 ohm coil is the Watkins part. Leave all of its network in front. For the 4 ohm connection I would start with just removing the 6mH and 100uf low pass. Your external active filtering will replace it. That woofer is also driven by a bandpass/lowpass section, but I would be tempted to leave those parts, as they are likely integral to the bass shaping inherent in the system (I'm of two minds about the 280uf, try it in and out).

If you can measure the acoustic output, then you can experiment some more. In general you won't be loading the amplifier excessively unless you do something that creates a voltage peak and attendant impedance dip.

Good Luck,

David

[tinitus]

isn't there a switch on speaker back ?

you might be able to see what components are switched on/off with 2ohm
its definately the 4ohm you want to use

but with active, you shouldn't need any part of the passive filter
ought to work connecting directly to woofer 4ohm terminal

[speaker dave]

It may work with the 4 ohm coil only, but why give up the Watkins feature? It flattens and extends the response. It also flattens the LF impedance.

Removing it will increase the active filtering requirements.

David S.

[DrDyna]

Originally Posted by speaker dave

It may work with the 4 ohm coil only, but why give up the Watkins feature? It flattens and extends the response. It also flattens the LF impedance.

Removing it will increase the active filtering requirements.

David S.

Is the active low pass filter frequency close enough to the watkins crossover point to cause issues?

If it isn't, I'd just treat the two coils as one driver, wire them together with the watkins device in place between the 2 ohm coil and the 4 ohm one, then active crossover as you would.

Edit: Clarity.

[back]

just to give a litle help from what i have read so far about watkins configuration.

the components at the 2 ohm coil make a bandpass filter which allows it to work

at around 30hz where the impedance rise and it lowers.

the result is constant impedance 2.8-3.3ohm from 27hz and up.to 20khz.

there is no resonance peak.

i disconencted the 2 ohm coil and the deep bass disapeared so the watkins part works

grear and i want to keep it as is.

on the other hand i want to improve control at the 50-200hz range where only

the 4 ohm coil works and i think that all the components

at this one make a 4th order low pass filter and could be replaced

by an active one.

i hope i don`t miss something.

[back]

looking at it again i think i must keep and the 265uf because it`s a high pass

at the 4 ohm, coil.

[cats squirrel]

its a high pass, which means it will cut the bass, also!!

[DrDyna]

Originally Posted by cats squirrel

its a high pass, which means it will cut the bass, also!!

Yes, the 4 ohm coil is in a bandpass.