Variable Linkwitz Transform Circuit?

Before my subwoofer amp, line level.
Essentially a standard Linkwitz Transform circuit for an Adire Tempest (Fs = 18.8Hz, Qts = 0.38, Vas = 317L) in a 4.5 cu ft enclosure for a Qtc of 0.71, except with a variable "new" Fc, so that I could adjust the amount of gain of the circuit. Then I could equalize for any room's gain for maximally flat response.
 
With that driver in a closed box room gain might be desireable. It will start it's roll off around the point where you room will start to gain (< 35 Hz).
Placed in a corner you will be very close to what would be the flattest bass reponse possible with that driver.
Qts is a little low for a closed box which will give a small peak in the bass around 30-40 Hz which can be adjusted with a band rejection filter, but that is hard to do over internet.
In theory it's easy, but needs trial and error development in reality.

Janne
 

argo

Member
2001-02-12 3:35 pm
Estonia
It would be interesting to see the variable Linkwitz transform circuit. So far I haven’t figured out how to implement this.
I also searched for variable frequency and variable Q (Bass boost) circuit with constant gain but with no great luck. So I decided to gather together the little info I had about active filters and draw such a circuit for simulation. Simulation has run good so far. There is nothing new - just standard variable hi pass filters and variable gain circuits linked together. I believe I have seen something similar in the web somewhere also. Again it’s not Linkwitz transform but lets you raise or lower the Q and/or frequencies you want to boost if this is what you are after.

Argo