douro20 wrote:they sound like air-raid sirens
What you are hearing is a response out of an LAFD fire station. The engines are the old Hall-Scott gasoline engines used by Crown Firecoach back in the 1950's and into the 1970's.
The sirens on the trucks are B&M S-8's. Though the last truck pulling out may be a Super Chief.
If you're familiar with Crown Firecoach, the S-8 siren is what is mounted behind the grille that is centered on the front of the pumper. The sirens were recessed. If you see a siren protruding from the front of the Crown, it usually is a Super Chief.
While they are all 8 port sirens, the Super Chief had a more nasaly sound, the S-8's had a deeper sound. Some of that had to do with how they were mounted on the trucks.
Crown with a Super Chief:
http://www.crownisking.org/cpsantamonicae7.html
Crown with an S-8
http://www.crownisking.org/cproyaloaks.html
Once in a while, you'll see a Crown with an external S-8
http://www.crownisking.org/cporcft36.html
Not all of the Crowns used B&M. There are more than a few that sported a Q2B:
http://www.crownisking.org/cplaco572.html
Also, during the 1970's the new look was the dual Federal electronic speakers:
http://www.crownisking.org/cplacitye3.html
Not to take this thread off topic, but one cannot really speak about B&M Sirens without talking about Crown Firecoach. Crowns made the B&Ms famous.
John