Re: [Harp-L] Multi-amplifier

["Jim Rumbaugh" <jrumbaug@xxxxxxxxxxxx>]

You asked:
Q:But what's the risk of putting a 3 ohm speaker on an 8 ohm amp
A: It's "kinda" like a small short circuit, The tubes and transformer have 
to dispate the energy gemerated. I do not recomended it.

Q:could an 8" 4 ohm speaker (be wired in *series* with the  3 ohm?
A: Yes, that is a good solution. You could also opt for a resistor in 
series. If the speaker is truley a 3 ohm speaker, ( dc ohm resistance 
measurements may not equal audio signal resistance/impedance), then a 4 or 5 
ohm resistor would work well. I would recomend the resistor be a 25 watt or 
greater size. ( that is 5 times the expected power dispated of about 5 watts 
of a 9 watt amp)

Jim Rumbaugh


----- Original Message ----- 
From: "geoff atkins" <geoffatkins@xxxxxxxxxxxxxx>
To: <harp-l@xxxxxxxxxx>
Sent: Monday, December 14, 2009 1:30 AM
Subject: [Harp-L] Multi-amplifier


> Advice please.
> I just got my new amplifier yesterday,.. we are "nearly there".
> It has a coke bottle rectifier, DC heaters, a couple of ECC83 preamp 
> tubes,
> separate bass mid and treble controls, and two class A-b outputs:
> one is a single ended 6V6 (~5W) and
> the other is twin EL84 's in push pull (~9W).
> Problem:
> I have narrowed the 12" speaker choice down to two: an 8 ohm HandH 35year
> old (~50watts), and a German 3 ohm veteran from the late 30's (~25 watt
> handling capacity). The output transformers are designed for 8 ohms.
> The German 3ohm speaker sounds wonderful, -even without a cabinet!
> But what's the risk of putting a 3 ohm speaker on an 8 ohm amp?
> What blows first, speaker, output transformer or tubes?
> "I won't play at full volume".. not for the first week anyway.
>
> Option: could an 8" 4 ohm speaker (be wired in *series* with the
> 3 ohm? and would the speakers then interfere with the signal getting to 
> the
> other?
>
>
>
> Geoff Atkins
>
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