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--- astra_conv:conversion:audio:audio [2014/08/22 13:33]
richard
+++ astra_conv:conversion:audio:audio [2014/08/22 14:09] (current)
richard
@@ Line 80: / Line 80: @@
 The thin doors of older cars require especially flat speaker chassis. I have chosen the AudioSystem "R165 flat" two-way speaker set, consisting for each side of a flat 165mm chassis, a dome tweeter and a two-way crossover.
-I was not convinced that the 165mm speaker would perform well at higher frequencies, especially what concerns its omnidirectional behaviour. So I daringly extended the front system to three ways (not counting the subwoofer), by adding midrange dome speakers (in a first attempt) and additional three-way cheapo crossovers (SinusLive CR-345). The 165 mm chassis is now only used as bass speaker.
+I was not convinced that the 165mm speaker would perform well at higher frequencies, especially what concerns its omnidirectional behaviour. So I daringly extended the front system to three ways (not counting the subwoofer), by adding midrange dome speakers (in a first attempt) and additional three-way cheapo crossovers (SinusLive CR-345, with 700Hz and 4500Hz crossover frequencies). The 165 mm chassis is now only used as bass speaker.
 The following graph (source: car&hifi) shows the frequency response of the two-way speaker set (including two-way crossovers) at two different angles. The graphs indicate that the 165mm chassis becomes highly directional at frequencies >1kHz (as is to be expected for a large cone speaker). It however also shows that this effect applies to the smaller tweeter too, at correspondingly higher frequencies.
@@ Line 91: / Line 91: @@
 {{:astra_conv:conversion:audio:mitteltoener_jrm3_spec.jpg?600}}
-I meanwhile have serious doubts that the shown frequency response has anything to do with the actual behaviour of these speakers.
+Meanwhile, I have serious doubts that the shown frequency response has anything to do with the actual behaviour of these speakers.
-Meanwhile, I have replaced them by "conventional" cone midrange chassis (Gladen Zero Pro 80). Frequency response including 2nd and 3rd harmonic distortion (source: hifitest.de):
+I later replaced them by "conventional" cone midrange chassis (Gladen Zero Pro 80). Frequency response including 2nd and 3rd harmonic distortion (source: hifitest.de):
 {{:astra_conv:conversion:audio:Gladen_test_results_hifitest_c.jpg?600}}
-#########
+Fortunately, with the given crossover frequencies of 700Hz and 4500Hz, they are operated in their "sweet spot", both what concerns harmonic distortion and frequency response including angular behaviour.
 The AudioSystem crossovers, that have very generous adjustment possibilities for the tweeter branch, remained in the dashboard and connect to the tweeters, that are mounted on top of the dashboard. Their lower frequency output, which is now set to transparent "straight through" mode, is connected to the inputs of the additional three-way crossovers mounted in the doors.
@@ Line 166: / Line 165: @@
 {{:astra_conv:conversion:audio:p1100380.jpg?600|}} {{:astra_conv:conversion:audio:p1100388.jpg?600|}}
-The mid range speakers (which have a closed camber) were mounted on wooden spacer rings, but due to their depth also required cutouts in the door panels. The ugly blain in the cover below the cutout even was intentional, though it came out misshapen: The new bass chassis have a slightly higher diameter, so I had to mistreat the plastic cover with the hot air blower to free some space for them.
+The mid range speakers were mounted on wooden spacer rings, but due to their depth also required cutouts in the door panels.
-{{:astra_conv:conversion:audio:p1100381.jpg?600|}} {{:astra_conv:conversion:audio:p1100383.jpg?600|}}
+For the cone speakers that I installed later, I used wedge-shaped adapter rings to slightly tilt the chassis back - and upwards.
-Re-assembled front door with bass chassis and midrange speaker.
+{{:astra_conv:conversion:audio:p1120163.jpg?600|}}
+{{:astra_conv:conversion:audio:p1120165.jpg?600|}}
+{{:astra_conv:conversion:audio:p1100383.jpg?600|}}
+The ugly blain in the cover below the cutout even was intentional, though it came out misshapen: The new bass chassis have a slightly higher diameter, so I had to mistreat the plastic cover with the hot air blower to free some space for them.
+Re-assembled front door with bass chassis and midrange speaker - first attempt ...
 {{:astra_conv:conversion:audio:p1100959.jpg?600|}}
+and the second, final version:
+{{:astra_conv:conversion:audio:p1120183.jpg?800|}}
 \\
@@ Line 219: / Line 231: @@
 After quite some fruitless efforts to get the system to sound well, I decided to objectively record the frequency response.
+##############################################################
+Please note: The following measurements were all done before I replaced the mid-range speakers. With the second version that I used, I was able to get a proper sound out of the system, by just adapting the levels of the different chassis. I so far have not repeated the measurements with the new setup.
+##############################################################
 This eigthies' electret condensor microphone is placed beneath the passenger seat's headrest.
@@ Line 260: / Line 279: @@
 Apart from that - it seems that here I am at a point where I can either pretend that I am happy with the sound, or I have to bear the effort of integrating a digital sound processor. Starting with this, probably also the passive cross-overs would have to give way to a few more amplifiers...
+##############################################################
+Please note: I had drawn above conclusion before I replaced the crappy midrange speakers. With the second set of speakers, the sound is now much better, without any large investments like sound processor or active crossovers.
+Before the speaker swap, I even had tried to integrate a sound processor. I returned it shortly after, since the sound got "artificial" rather than "good".
+##############################################################
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