Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 1blueheron on April 09, 2020, 02:14:57 pm

Title: Help matching impedance
Post by: 1blueheron on April 09, 2020, 02:14:57 pm

I am building a 2X12 cab for a little Silvertone SE amp.  The original speaker measured about 7.6 ohms.  I have 2- 8ohm speakers I would like to use in the cab.  I am not that familiar with tube amp to speaker impedance matching other than I know it is supposed to be more critical than with SS.

What are my options?

Title: Re: Help matching impedance
Post by: sluckey on April 09, 2020, 03:10:12 pm

Don't worry. Be happy.

Title: Re: Help matching impedance
Post by: PRR on April 09, 2020, 09:45:30 pm

Ohm meters read DC. Amp-"matching" you want an Audio impedance. "8 Ohms" audio will read 5 to 8 ohms on the ohm-meter.

Anyway an SE amp will work fine if impedance is even "close". It may be down on power. But a more efficient speaker may compensate. Anyway if you need BIG sound in big spaces you won't be using an SE amp.

Or what Sluckey says.

Title: Re: Help matching impedance
Post by: Latole on April 10, 2020, 04:22:42 am

8 ohms speaker is impedance ( in ohms )
Meter can read only resistance, ( in ohms too ) but two different things. It is close from speaker impedance.

Meter resistance reading : Not good for transformer impedance, too far

Résistance and impedance :

https://circuitglobe.com/difference-between-resistance-and-impedance.html

Title: Re: Help matching impedance
Post by: 1blueheron on April 13, 2020, 12:13:26 pm

Thanks for the help guys.  We wired the 2- 8 ohm speakers in parallel Fri. and tried it out.  Sounds good so proceeding with the new cabinet build and will leave them in parallel.   Will post some sound clips when finished.