• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Fostex or Car Speakers for My Tube Car Amp

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Hi All,

Thanks for all your assistance regarding the Tube Amp that I'm building for my car. So far so good. I'm currently busy and it should be up and running in a few days time. I've decided to follow the Dynaco Mark 3 circuit but using 6550's in the output stage. By what I read they seem to be quite hardy and tolerent to rough usage. I'm also going to wire up in Class A, Triode Coupled. Where my question comes in, do you suggest I use ordinary car speakers, been considering the 2 way components from MB Quarts. A 6½ inch bass-mid and a 1 inch soft dome tweeter. Sensitivity at 87 dB/w/m. An 8 inch Sub powered by a Solid state amp will assist in the bottom octave or two. Or i've been thinking of trying out a Fostex FE166E, sensitivity 94 dB/w/m. Fitted into a 2 liter sealed cabinet frequency is stable from 200Hz and up. The sub can be adjusted up and to roll off at 200Hz. Please help me with some advise. Still looking for a tweeter. Any suggestions there?
If going Fostex, the FE167E may be better than the FE166E in your application. The FE166E was meant to be horn loaded where the FE167E was meant for BR. Just a suggestion, check the spec sheets to see which one best fit's.

However, with that sensitivity rating of 94dB you can pretty much bet there will be noise issues if you put them into a car. Also, the amp your building will have much more power than what is needed to drive the fostex to loud levels. You may be better off using something in the 87-91dB range. If you want to go the full range driver route you may want to check out some tang band or Jordan drivers. I'm not familiar with the component set you refer to, but generally tube amps like a somewhat flat impedance response. So that means low Q drivers to avoid the single frequency bass hit effect. Also, there can be frequency response coloration in some multi-way designs when paired with some tube amps. However, some Higher Q drivers in a sealed box can give a ported box like response when paired with an amp with a high output impedance.

The best thing to do would be build the amp then find out the output power and output impedance. Then post back, and we can help find a good match for your amp.
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