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Spec Wars: Looking Inside Loudspeaker SPL Specifications

While it might be possible to attain stated max levels from that box, it'll probably only happen once... and it might catch fire.

But no, the chap I spoke to was adamant; apparently that 10-inch box would definitely produce 136 dB, and further, would sound good doing it. I ran the simulation, and the driver would need to move 2 inches one way to produce the stated SPL at 80 Hz (where the port would be inactive). There isn’t a 10-inch midbass cone on the planet that can do this, and definitely not this company’s driver.

I wasn’t getting anywhere, so I moved on. I also reached out to this manufacturer’s R&D department regarding this issue but haven’t received a response.

Manufacturer B, another fairly large company, proved more sympathetic, admitting there definitely is a specification “war” going on and that they do try to keep their numbers reasonable despite losing potential projects (and sales) over it. Apparently customers often came back around, though, when they realized that competitive products won’t do what it’s claimed.

The other seven manufacturers I spoke with are mostly smaller companies that share my views on this topic. Most provide sensible numbers with their boxes, such as a 12-inch, 1 KW model with a 127 dB maximum SPL. I checked with the designer of that particular loudspeaker, and he confirmed – 97 dB at 1 watt, and indeed it carries a 1 KW amplifier. Fair enough.

One company representative pointed out that if the loudspeakers made by Manufacturer A could really attain 136 dB, they really ought to be bolted on to every jet aircraft to be used for active noise cancellation. Touché.

Later, I dropped by to visit another big company, which was showing a 3-way point source cabinet equipped with a pair of 10-inch midbass cones, an 8-inch midrange in a horn, and a compression driver. The stated SPL spec is 141 dB.

When I raised the issue with a person that really knows his stuff (Hi, Hans!), I was told that it will “technically” produce 141 dB. The test resulting in this number utilizes a very short burst of signal containing all frequencies, and it doesn’t matter how much compression or limiting is taking place, the engineering team keeps pushing the power up until the meter reading won’t increase any more.

Think about that. Even if one driver started limiting 10 dB ago, they carry on with pushing the fader. If they were to keep that fader position and replace the test signal with music, whichever part was limiting (bass, midrange or treble) would pretty much disappear from the music, and it would sound horrible. This doesn’t account for distortion levels at that power level either.

So, we have new information about how we should rate our example system. Let’s get back to that.

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