JL Audio tests the SMD DD-1

[audiofanaticz]

This is awesome!!

[Ric Thornton]

good stuff bro!

its a fantastic device for sure!

[DTS909]

one more reason why I want one.

[larrys95civic]

thats freakin cool man,

[meade916]

a follow up from JL from the facebook post/thread.

JL Audio

OK…the long and short of how our nine-step method came to be may shed some light on the questions on how we compensate for different impedance loads. First, the “best” way to set levels would be with an oscilloscope. However, in reality we realize that most shops either don’t own one or if they do, they may not know the best way to use one. We looked for an easier method that did not involve expensive / elaborate equipment. The logic was that EVERY shop could be expected to have a digital voltmeter and have access to a CD with test tones. In order to make these very basic tools work, a number of assumptions needed to be made. And you know what they say about assumptions….

One assumption is that the source unit does not clip at 75% of full volume. This is not always the case, but it is USUALLY the case.

Another assumption made has to do with how we calculate our target voltages. Using Joule’s Law, we know that power is equal to voltage squared divided by resistance. By reworking that basic formula, you can determine that voltage is equal to the square root of power multiplied by resistance. Example #1: Let’s say we have 31.6 volts and a 2-ohm load. Using the first formula, 31.6 times 31.6 give you 998.56 (voltage squared). Take that number and divide it by 2 (resistance) and you get 499.28…which we can easily call “500 watts”. Example #2: You have 750 watts and a 4-ohm load. Using the reworked formula, 750 multiplied by 4 gives you 3000 (power times resistance). Take the square root of 3000 and you get 54.77 volts. So the target voltage in this second example would be 54.8 volts. But herein lies the tricky part…that word: “resistance”. Resistance is used for DC applications, but music and audio amplifiers are AC. When you model up a speaker you can often look at the impedance graph and you will see how the impedance will have peak(s) and valley(s). Without getting TOO deep on this, by using the “nominal impedance”; such as “2-ohm” or “4-ohm”, we are taking an educated guess for our calculations. In practice, every amplifier has a maximum output voltage, determined by clipping and a maximum output current (another aspect of Joule’s Law is that power is equal to voltage times current…) which is determined by protection circuits, fuses or explosions.

So, when using our method, we are seeking to set the voltage according to an admittedly compromised situation based upon assumptions (but not blindly…). The DD-1 is finding the voltage limit of the amplifier. In both cases, the speaker that is connected will “fill in the blank” with regard to the CURRENT and therefore determine the power. If you read all that carefully you will notice that your speaker is RARELY if EVER getting every single Watt you might be expecting. But what you can expect is that when your music asks for your amplifier to produce maximum power to the speaker connected, it will do so with MINIMAL clipping (as determined by the overlap; about 10dB or so in our method or the various levels that the DD-1 allows for). Speakers typically don’t die after short bursts of ‘butt-loads” of power (technical term….)….they typically die after longer lasting events of excessive power; and those events are most often a result of improperly set levels. This is why we strongly support using our nine-step method, the DD-1 or an oscilloscope (there are a couple of other cool methods too). This is a heck of a lot better than “by ear” or arbitrarily setting things at “half way” or something like that… -st

[Q-Bert]

Maybe I can convince my boss to buy DD-1's for his other shops now that a respected manufacturer has backed the tool. He refuses to believe that the DD-1 does what it say's even after I sent him numerous YouTube videos and a demo of using it in my vehicle. He still thinks his ear is just as good even after proving him wrong.

[meade916]

Maybe I can convince my boss to buy DD-1's for his other shops now that a respected manufacturer has backed the tool. He refuses to believe that the DD-1 does what it say's even after I sent him numerous YouTube videos and a demo of using it in my vehicle. He still thinks his ear is just as good even after proving him wrong.

to be honest, if your boss doesn't at least use an o-scope, he probably shouldn't be the boss. At least not an "installer" boss. Maybe he should stick to paperwork

[JEMT8]

I know what i am getting for Christmas

[VIPmeetSPL]

If JL saisld it was cool then am getting one lol jk. JL has nothing to do.with my decision just still saving up and.then bam I will rule the world....(don't ask)

[VIPmeetSPL]

Hey Steve did you set your Tahoe with a dd1 was there any difference than when you set it.with an.o scope?