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I have seen a number of posts where the more knowledgeable members here claim a speaker (or driver) simply can’t meet published specs.But when I consider which driver to buy I have little more to go on than the published specs. I’d like to think I could trust the “big names” like JBL.
So which companies consistently put out drivers that measure per specs and which one’s had a habit of fudging? I am mostly interested in pro audio style drivers and names like B&C, Beyma, JBL, 18sound, Audax, Radian, Eminence, etc.
What are some of the more common warning signs to look for?
Russ
Follow Ups:
JBL, TAD, B&C, Ciare, Supravox, Usher, Lambda (sadly out of business) - these are the ones that come to mind.I've also tried high efficiency drivers from at least eight other brands whose specs in my limited experience and opinion are somewhat optimistic. That doesn't mean the drivers are bad - just that perhaps the marketing department took some liberties before the specification sheet made it to the printer. The engineering department may well have zero control over the marketing department.
Duke
Always heard they were pretty spot on spec.
It isn't necessarily the manufacturer; the individual driver's design (and parts source) can have a lot to do with it. For example, I bought a pair of JBL 2225's on ebay and measured them the other day. Even though they're old, the specs were almost exactly what was in the spec sheet. I also have a JBL W15GTi (big 15" car sub, neo magnet, differential drive motor). It's not particularly close to meeting the published specs (Fs high about 15%, Qe high about 60%, Vas low by 35%). This is because the moving mass is higher than spec by about 13%, compliance is low by 34%, and BL is about 5% low. Net result, however is not too terrible - in a 200L box, the response difference is the actual driver is about 2dB less sensitive above 150hz, has identical response between 30 and 50hz, and is about 1.5dB lower in output at 20hz (for the same power input). The Q of the box goes from 0.6 to 0.8, so there's less excursion at low frequencies. So the performance of the driver is still in the same ballpark as what the published specs indicate, and the specs are still a somewhat valid way to shop for a driver. In this case, I was more interested in the low distortion motor design. If you want to be really precise, you'll still want to measure the drivers you actually get, but even then, the driver's specs will change with cone excursion and power, so I'm not sure how worthwhile it is to be really picky in doing small-signal box design. What I would be more concerned about is variation between units. Most cone drivers tend to be pretty good in this regard (assuming you get parts from the same production run), but typically this is not spelled out in published specs.
That JBL car woofer sounds very interesting. However, I was unable to find the Thiele-Small parameters on the JBL website. Any pointers? Thanks.
Click the 'enclosures sound quality' link at the bottom.
That Bandpass Box looks pretty interesting for a powered sub project.
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Boo!
In Fostex,Aura, Accuton,BMS,Eminance,JBL,SEAS ,Fountek, PHY,Supravox,TAD I trust for a short list. For me its been cheap drivers that dont meet spec and need careful matching and rejection to get ok sound.HI-VI makes good ribbons but the other drivers I have used from them where a bit off.Audax PR 170mo tested far off spec 95-96db at best.Silver flutes where all over the place measurement wise but with all things audio YMMV Common warning signs? cheap price and wonderful specs,bold claims of performance with no solid test results to back it.
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