Senior Member
Location: Bishops Stortford
Posts: 1,250
I'm Chris.
30 ohm bass drivers
As part of a 3 way speaker system I currently run the 8 ohm 15 inch Eminence Alpha drivers from a dedicated Rotel transistor amp.
I want to try a vintage pair of 15 inch drivers, but they are only available at 30 ohm impedance. Are there any issues I should be aware of if I plug them in, apart from changing component values in the low pass filter.
Source
SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
SW1X USB II
SW1X DAC III Special
Audiolab 6000 CDT transport
Amps
Pre amps -- Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired. And First Watt B1 active no gain buffer.
Power amps -- Welborne 45 SET monoblocks 1.8W / Decware Taboo 6W / Elekit 300B TU-8600SVK plus further improved components 9W / ICE Power 1000W
Speakers
Highly modified Endorphin P17 open baffle speakers containing both vintage and modern alnico drivers and paper cones. All silver wired - 8" Cube Audio FC8 full range drivers and vintage 15" Altec VOTT 416 bass drivers. All sat on Townsend Audio Podium seismic isolation platforms.
BK Electronics XLS400FF Sub.
Cabling
Silver mains cables, interconnects and speaker cables by SW1X
Headphones
HRT HeadStreamer and SennHeiser HD650 headphones
Senior Member
Location: The Black Country
Posts: 6,089
I'm Alan.
Yes, you will only achieve 1/4 of the power into 30 ohm speakers compared to 8 ohm.
If the drivers have a greater sensitivity you should be OK.
Trade: LDR
Location: North Island New Zealand
Posts: 1,757
I'm Chris.
Certainly that is the case with solid state amplifiers, but not valve amplifiers http://education.lenardaudio.com/en/...ve_amps_7.htmlOriginally Posted by Firebottle
"because Valve and solid-state amps operate in opposite ways to how power is delivered into a changing Impedance, the resultant audible difference is very noticeable.
Voltage Current drive comparison
Valve amp power is directly proportional to speaker Impedance
therefore power increases as the speaker Impedance rises.
Solid-state power is inversely proportional to speaker Impedance
therefore power decreases as the speaker Impedance rises. "
Senior Member
Location: London/Durham
Posts: 6,878
I'm Lawrence.
Doesn't that assume that amplifiers are perfect voltage or current drivers, which is just not true? There's the output impedance to consider if nothing else.
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Captain Insightful
Location: Seaford UK
Posts: 1,861
I'm Dennis.
My conception is that voltage drive was always the aim even with valve amps, but they were compromised because of O/P transformer characteristics, and the presence of the O/P transformer is because of the inherently higher O/P Z of valves.
When transistors evolved, much lower O/P Zs were obtainable and so the ccts functioned more towards the voltage drive ideal, and they were also transformerless, then going direct coupled thus removing the O/P caps.
There are still some who espouse deliberately designed current drive, saying that it has other advantages.
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