At your risk.
Not a easy task.
Objective measurements would have to be done, warble tone SPL measurements etc.
But even then we know the frequency response of our brain sound perception depends on sound intensity.
Sound intensity depends on how close we are to speakers. How sensitive they are. How powerful is the amplifier...
The quality of the amplifier depends on how few components are used.
A one transistor amplifier can sound great but it won't be possibly be very high power output.
But this may not be a bad thing as Linoleum Auratone 5C type monitoring speakers are meant to be near field. Nevertheless even a low power amp of high quality gives excellent results on music ambience heard around many room.
A problem is that if power is tried to be increased the direct current though the speaker, deflects the speaker and possibly decreasing the compliance ie the low resonant frequency.
Other problem is efficiency or electrical impedance matching. A 2N3055 may better match with a 70Ω speaker and a higher that 12V supply? Perhaps trying also another transistor such as 2N3053?
Although + or - 3dB flat frequency response has been achieved with the linoleum Pleiades Auratone 5C type speaker (with the Tesla 5in drive unit) from 100Hz to 15KHz what to do for optional 50Hz-100Hz flatness?
Pleiades (resistor,capacitor) filters are being tried at the input of the 2N3055 amplifier for reducing everything else so that response becomes 50Hz-15KHz. But then efficiency will go down. The filter interacts with the changing input impedance of the amplifier by a different setting of volume control. The human brain changes its frequency response the lower the sound pressure level...Interactive monkey system.
Anyway at the moment 9.9V are supplying the 2N3055 single transistor power amplifier. The bias resistor from supply to base is 17KΩ. With 17KΩ the double bass notes on O Grande Amor - Jobim could be clearly heard compared with 10KΩ, possibly due to change of reasonant frequency of drive unit as mentioned above. The configuration is emmiter follower. But music electrical signal is applied directly to emitter and base without a coupling capacitor. A Pleiades filter of (90Ω,12.2μF) is used to boost low bass. The Sony Walkman with its 150Ω bridged line out output impedance feeds the filter in parallel and then there is a series volume control resistor to transistor base. Just 250mV DC voltage across 4Ω speaker from the quiescent class A (electrons flowing all the time) current of the 2N3055 transistor.
The sound is clear and beautiful, unloud.
Next day addition: another nice setting is (90Ω,12.5μF) for input Pleiades gentle bass boost shelving filter, 1.7kΩ bias resistor, Vb=13V, therefore 500mV across speaker voice coil. Nicer bass sound, seems speaker less stressed from less DC current, less power output, even better sound quality. Now listening to Frozen - Madonna at pristine sound quality.
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