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In the Forum: Horn-Loaded Speakers
In the Thread: Altec Model 19 in Boston.
Post Subject: Altec 19’s bass and continuously adjustable output impedancePosted by Romy the Cat on: 9/23/2010
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Last night I was cleaning/setting the room where the hated Altec 19 were sitting and I decided play them for a while. I used a few different amps. To drive Altec 19, especially in it’s default configuration, always was a subject of debates and disagreements. I had a few amps that I tried with more or less success. I did not paid attention to upper region of the Altec 19 – then are improperly made to do it right, but I was looking at bass that the Model 19 does.
As much as I like the Model 19 bass driver as much I always hated the Model 19 bass. Still using different amps, tube sand SS, I recognized that the variation of bass was much larger then it shall be expected. After a bit thinking I concluded that the bass variation that I heard was not the variation in amplifiers but the variation amp’s output impedance.
I decided to test it on practice and tock my Yamaha B2 amp and connected it to Model 19. The good part about B2 is that I have a comfortable full control of how I bias the output stage, so I begin to very accurately and very gradually slide the B2 bias from 20mA to 350mA. The bass of the Altec 19 was changing right in my eyes, perfectly reflecting the amp output. In fact I never had seen the speakers so sensitive to those things. Apparently they have huge port reactance and I guess the best bet would be to have the amp’s current to damp the port reactance. The kink in it to damp it right before or right after the port dive making the speakers to produce what they call ”bass”.
I was able to manage the Altec 19’s bass to very large degree. I do not claim that I was able to get bass that I feel it right bass but it was not my objective. My objective was to confirm that when idiots on-line sing the songs that Altec 19 has a good bass but to get there you need a good tube amplifier then they are expressing nothing more than idiocy. Sure, the Altec 19’s bass channel needs current (power) but it also needs very precise amount of current to control the driver while the port is turning on. Picking different amps would hardly give a right level of precision – it needs to be continuously adjustable output impedance…
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