Another Stereomour build

[denti alligator]

So I have the Forte IIs. Not sure how they compare with the Forte I you have, but mine sound best with the Stereomour set at 4ohms. However, I might still be missing out on something. Here’s the frequency response, though not sure sure to what degree this is altered by the Crites upgrades.

https://community.klipsch.com/index.php?/topic/170785-alk-xover-diy-for-forte-ii-schematic/

 

[Paul Joppa]

**** Passive bass boosting with Stereomour II ****

Note: This is actually cutting everything above the bass by a few dB, so you will need to increase the volume setting for the same loudness.

The simplest way to do this is with a series RC network, placed across the volume control potentiometer. Connect a 15Kohm resistor to one end of the volume pot, connect 1 0.022uF capacitor to the other end of the pot, and connect the free end of the capacitor to the free end of the resistor. Insulate that connection with heat-shrink tubing or electrical tape so it can't touch the chassis or any other nearby wires or terminals! Repeat for the other channel. This will be a tight fit.

This gives about 5-6dB boost to the bass below about 350Hz. You may want to try some different component values to get the effect you want:

Increase the capacitance to get a lower transition frequency, or decrease the capacitance to get a higher transition frequency.

Increase the resistance to get a smaller boost AND a lower transition frequency. Don't  decrease the resistance, because that will reduce the input impedance and sensitivity of the amp too much.

 

[Paul Birkeland]

For a much harder way, you could bypass the 365 ohm cathode resistor with a choke, cap, and resistor in series to bring up the gain in the midbass. 

I would start with:
https://www.mouser.com/ProductDetail/Murata-Power-Solutions/13R336C?qs=gLyyx31KZaCXYrPIar3DqA%3D%3D

https://www.mouser.com/ProductDetail/Nichicon/UDB1H6R8MHM?qs=kArNe9LFxXkiWy78BPgsnw%3D%3D

https://www.mouser.com/ProductDetail/Vishay-Dale/RN55D10R0FB14?qs=60NadEv6cQm8bIQ8le8fAg%3D%3D

Those three parts are wired in series, then tacked across each 365 ohm resistor.  Reducing the resistor value increases the effect of the filter, so putting a 100 ohm pot in there is also a reasonable choice as an experiment.  In fact you could probably find a 100 ohm stereo linear pot to just temporarily stick to the chassis, then wire this up from there. 

The L and C can be adjusted to change the shape of the filter and/or the frequency where you get the most boost. 

PJ's circuit is a lot easier to mess with though!

 

[Carbon13]

Thanks guys! PJ, is this doable with the mourquiet upgrade? That's what I currently have in place.

 

[Carbon13]

I just found this thread on redesigned crossover for forte 1s, maybe another option?

https://community.klipsch.com/index.php?/topic/106102-developing-a-network-for-the-forte/

 

[Paul Joppa]

Thanks guys! PJ, is this doable with the mourquiet upgrade? That's what I currently have in place.

Alas, it is not. I'll ping PB and see if we can come up with something.

We worked on a tone-control preamp a while back. That gave us the initial design ideas for the Moreplay preamp, but the additional stage and controls added too much cost and complexity for what we expected would be a small audience.