I've modified your circuit so it drives an 8
hm: speaker with no problem.
The forum wouldn't let me attach the .asc file so I've enclosed it in code tags. Just paste it into a text editor such as notepad of emacs, save it as a .asc file and open it in LTSpice.
Code:
Version 4
SHEET 1 880 680
WIRE 304 -240 -336 -240
WIRE -448 -192 -592 -192
WIRE -336 -192 -336 -240
WIRE -336 -192 -448 -192
WIRE -144 -192 -336 -192
WIRE -16 -192 -144 -192
WIRE -448 -176 -448 -192
WIRE -592 -144 -592 -192
WIRE -16 -144 -16 -192
WIRE 304 -112 304 -240
WIRE -144 -96 -144 -112
WIRE -80 -96 -144 -96
WIRE -144 -32 -144 -96
WIRE -16 -32 -16 -48
WIRE -448 48 -448 -96
WIRE -368 48 -448 48
WIRE -144 48 -144 32
WIRE -144 48 -304 48
WIRE -16 64 -16 48
WIRE 48 64 -16 64
WIRE 144 64 112 64
WIRE -144 80 -144 48
WIRE -16 80 -16 64
WIRE -448 96 -448 48
WIRE -784 144 -944 144
WIRE -592 144 -592 -64
WIRE -592 144 -720 144
WIRE -512 144 -592 144
WIRE -592 192 -592 144
WIRE -144 208 -144 144
WIRE -80 208 -144 208
WIRE 144 208 144 64
WIRE -944 224 -944 144
WIRE -448 224 -448 192
WIRE -144 224 -144 208
WIRE -944 336 -944 304
WIRE -592 336 -592 272
WIRE -592 336 -944 336
WIRE -512 336 -592 336
WIRE -448 336 -448 304
WIRE -448 336 -512 336
WIRE -352 336 -448 336
WIRE -144 336 -144 304
WIRE -144 336 -352 336
WIRE -16 336 -16 256
WIRE -16 336 -144 336
WIRE 144 336 144 288
WIRE 144 336 -16 336
WIRE -512 352 -512 336
WIRE -352 400 -352 336
WIRE 304 400 304 -32
WIRE 304 400 -352 400
FLAG -512 352 0
SYMBOL npn3 -512 96 R0
SYMATTR InstName Q1
SYMBOL res -608 -160 R0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res -608 176 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL res -464 208 R0
SYMATTR InstName R3
SYMATTR Value 100
SYMBOL Misc\\signal -944 208 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value SINE(0 .5 400)
SYMBOL res -464 -192 R0
SYMATTR InstName R4
SYMATTR Value 1k
SYMBOL res -160 -208 R0
SYMATTR InstName R5
SYMATTR Value 1k
SYMBOL res -160 208 R0
SYMATTR InstName R6
SYMATTR Value 1k
SYMBOL npn -80 -144 R0
SYMATTR InstName Q2
SYMBOL Misc\\battery 304 -128 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 20
SYMBOL res 128 192 R0
SYMATTR InstName Speaker
SYMATTR Value 8
SYMBOL cap -304 32 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C2
SYMATTR Value 10µ
SYMBOL pnp -80 256 M180
SYMATTR InstName Q3
SYMBOL diode -160 -32 R0
WINDOW 0 39 32 Left 0
WINDOW 3 -28 29 Left 0
SYMATTR InstName D1
SYMBOL diode -160 80 R0
WINDOW 0 42 30 Left 0
WINDOW 3 -29 30 Left 0
SYMATTR InstName D2
SYMBOL res -32 -48 R0
SYMATTR InstName R7
SYMATTR Value 1
SYMBOL res -32 64 R0
SYMATTR InstName R8
SYMATTR Value 1
SYMBOL Misc\\EuropeanPolcap 48 80 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName C3
SYMATTR Value 1000µ
SYMBOL cap -720 128 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 10µ
TEXT -752 -32 Left 0 !.tran 0 5 1 1