Help - New HU w/ higher pre-out required turning UP amp sensitivity

[99v70r]

Hello, I have a completely aftermarket system (outlined below) and after replacing my head unit with a model that has 4V pre-out instead of 2V pre-out, I was getting very little volume out of the speakers and had to turn UP the amp's input sensitivity.

My expectation was that I would be able to turn DOWN the amp's input sensitivity with a higher pre-out voltage from the head unit. In fact, the amp has a labeled input sensitivity with 5V at the lowest setting and 0.1V at the highest setting - and I assume it should match the head-unit's rated pre-out (a 2V head unit would result in the amp's input sensitivity being set to roughly 2V).

Old setup:

HU: Kenwood DMX47S
4 channel amp: Kenwood KAC-M1814
Speakers: Kenwood KFC-D161 (Each speaker is on it's own channel at 4 ohms.)

New setup:

HU: Kenwood DMX7709S
4 channel amp: Kenwood KAC-M1814
Speakers: Kenwood KFC-D161 (Each speaker is on it's own channel at 4 ohms.)

With the old head unit, I had the input sensitivity on the amp set to 1.8V. With the new head unit, the speakers are much quieter at this same setting. I used a multimeter to tune the input sensitivity (reading output voltage from the amp to the speakers) and had to set the input sensitivity to 0.3V to get the correct output from the amp!

Am I misunderstanding something, or is the head unit outputting far less voltage than advertised?

Thank you

Edit:

I've been doing some research and it looks like 4V is the MAXIMUM output. The pre-out voltage will vary depending on volume and frequency. The only explanation I could find for needing to increase the sensitivity is the voltage curve (related to volume) must be difference between the head units.

I was able to get the head unit to output 4V by setting the volume to max and playing a frequency around 10k hz.

Local tuners suggested tuning by ear and going from there. I'm leaving the 4 channel amp at 0.3V sensitivity, and plan to increase the "Bass level" on the head unit (which increases the voltage to the sub pre-out) so that I can reduce the sensitivity at the subwoofer and prevent distortion there, at least.

[BEJinFbk]

Looks like it's all Kenwood - Have you contacted their tech support?