Loudspeakers Old v New

[John10b]

In another thread LS efficiency is mentioned, this got me wondering, again, about why vintage LS are, apparently, more efficient than modern LS?
So my question, is this true, and if so why?
John

[paulsherwin]

It isn't really true. Some speakers are more sensitive than others - this has always been the case.

[Herald1360]

If you want a speaker with a flat response and suitable for any old amplifier rather than one that's tailored to the speaker, you effectively have to flatten all the response peaks down to the same level as the troughs. That's going to give a speaker which is less efficient overall at turning electrical power into sound power. Nowadays, electrical audio watts are cheap historically they weren't.

[John_BS]

Yes, it's all about reducing (as far as possible) "colouration" and flattening what might be termed "resonant peaks" (a more extreme version of colouration). Most old non Hi-Fi speakers had thin paper-pulp cones with a straight profile. A light cone raises efficiency, and if the material is not critically damped you tend to get standing wave effects where the acoutic wave travels though the cone material to the surround, where, if of a different "impedence", the wave is reflected etc. Even in many modern speakers you can see peaks of 10dB or so mid-range (where the ear is most sensitive) , which gives the speaker a subjectively high sensitivity. Not too pleasant to listen to for very long, though.

John

[John M0GLN]

I have to admit I always thought that old speakers were more efficient than new ones, I'm no expert and can't quote you any figures except that looking at the power in watts there seems to be a requirement for modern speakers and amps to have very high power, I know there are peak, average, RMS and music watts but even allowing for the differences in them where does this extra power go?
I always assumed that watts were expensive years ago with valves and output transformers and you needed efficient speakers, whereas now a high power amplifier would be very cheap and could do away with the need for efficient speakers.

John

[Lucien Nunes]

Multiple parameters can be traded for sensitivity, which is a less valuable resource now for the reasons stated. Flatness of response, small size and perhaps most perniciously, extended bass response which can be a huge power guzzler if the box size is constrained.

[emeritus]

In the 1970's I used to provide the music for a club I belonged to, using my EL3302 feeding my modified car radio (removable), feeding a pre-war 10" speaker that dad had salvaged from an old radio. The car radio's amp was stated to be only one watt, but the setup provided enough volume for the small hall we used to meet in. Not what you coud call hi-fi, as the 3302 could just about manage 9.5kHz, but adequate for its purpose. Dad's 1950's radiogram, with a specified max 3W ouput from a single output valve operating in class A, subjectively produces more volume than my 30W per channel 1980's music centre.

[joebog1]

I think one of the main reasons "vintage" speakers are more efficient is the gap between the voice coil, the pole piece and the magnet. When I replaced the surrounds on my Tannoys I found that the gap was VERY small. I use pieces of stiff mylar to center the voice coil in the gap and found my stock was all too thick. When I use these same mylar strips in modern speakers some rated at 1000 watts ( 1kW ) I need to put two together to fit the gap. I suppose the heat generated in my Tannoys ( rated 30 watts) would be considerably less than the coil dissipating 1000 watts. remember they will expand with the generated heat.

Its my theory anyway.

Joe

[Radio Wrangler]

Loudspeaker manufacturers came under pressure to flatten their responses. It wasn't possible in a passive device to fill in the troughs up to the level of the peaks, but it was possible to flatten the peaks down to the level of the troughs. A sort of handicapping. You can't make the slower horses run faster, but it's easy to slow down the faster ones, so races get slowed down but produce more uniform results. Loudspeakers similarly got less efficient.

Then the market wanted bass down to lower frequencies. With limited case size, this costs dearly in efficiency, and the speaker has to stay flat, so the lower efficiency has to be extended across the rest of the frequency range.

As a result, modern speakers have become flatter in their responses, have better transient behaviour, and cover a wider frequency range, but have paid for it in efficiency. that's OK, powerful amplifiers became easier, which compensated.... but now the drivers need to handle the heat, as Joe points out above. Bang goes some more efficiency.

As a reference marker, a trombone going flat-out produces about 0.5W of acoustic power.

David

[Herald1360]

Originally Posted by Radio Wrangler

.

As a reference marker, a trombone going flat-out produces about 0.5W of acoustic power.

David

Which would need around 5W into a horn loaded (matched?) speaker and 50W+ into a modern hifi type. Maybe 25W into a "vintage" PA speaker?