Wednesday, May 10, 2017

High Output Speakers

A friend recently offered to sell me a somewhat broken (but highly repairable using the endlessly available preowned and not yet worn out parts on eBay) pair of some famous and popular rock n roll speakers, Pioneer HPM 100, for a very low price.  Though this speaker wasn't on the top of my list for future high output experiments, it's a contender, and for the price I'm paying it can also work as a garage speaker, which I need for my keyboard setup.  Even needing repair, you can tell these speakers have a punchy sound.

HPM 100 will flap out some pretty high output levels, though I haven't been able to find any exacting specifications like I can find now for the likes of JBL 4425, which are specifically rated to 114dB SPL (we could assume that's "flat" rating since it's program material and not noise--for which dBA is intended) with a graph showing the specific MOL for each frequency (114dB is only for a narrow region in the bass, the MOL at higher frequencies is somewhat lower).

Here's a list of vintage JBL speakers from which I identified the 4425 as being of interest.  Also worth looking at are 4411, 4412, 4430, and 4435.  You can tell from their parts that they are designed for high output: big woofer(s), big midrange or horns.  The maximum output of the 4411 isn't described in one number (looks to be above 105dB from the graphs shown, so I'd guestimate around 110dB) but the 4430 and 4435 are rated at 119dB and 122dB respectively and for continuous sound output (!!!).  That's what horns and big woofers can do!

Paul Klipsch (and many others) basically speak in code when they describe the need for "efficiency." In his famous speech, Klipsch says you don't need high efficiency anymore to get high output, you can simply use a high power amplifier.  But then he says with high efficiency your amplifier will distort less and therefore sound better.

It seems to me that if you have a suitably high quality amplifier, one that maintains low distortion levels even at high power output, and there are many such amplifiers today, Klipsch's second argument (that your amplifier will distort less) is as useless as the first.  Neither argument actually justifies high efficiency speakers.  In fact, quality high power amplifiers will generally have less S+N at high output than below 1 watt.  It was only 20 years ago that Nelson Pass praised the First Watt as being the most important, as for the previous decades it was seeming like the first watt was virtually ignored except by those demanding Class A or Class AB+.

But Klipsch (and the current legions of flea amp cultists) are missing one key point.  It is much easier to make a high efficiency speaker play louder than a low efficiency speaker.  Not only does a low efficiency speaker require more power input, it must also dissipate a large fraction of that power as heat, usually in very limited areas such as voice coils.  And there are serious limits in most cases as to what can be dissipated there, except in hugely costly designs.

And it's well known by fair minded people that Klipschorn K's, and the many Altec and JBL high efficiency speakers will play much more loudly than less-than-megabuck audiophile low efficiency sealed boxes.

So when Paul Klipsch brags about efficiency, what he's really doing is giving you an excuse to tote those high _output_ speakers into your living room.  Because output levels up to at least 100 dB are essential to completely accurate reproduction.

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