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When it all clicks

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IainB View Drop Down
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    Posted: 17 January 2018 at 9:16pm
Lightbulb moment, just been reading through the MT102 faqs and noticed this https://www.speakerplans.com/index.php?id=faq2 
Everything totally makes sense now Smile
For any other newbies or those just a little confused, have a read and see if it works for you LOL
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kevinmcdonough View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 19 January 2018 at 2:43pm
Originally posted by IainB IainB wrote:

Lightbulb moment, just been reading through the MT102 faqs and noticed this https://www.speakerplans.com/index.php?id=faq2 
Everything totally makes sense now Smile
For any other newbies or those just a little confused, have a read and see if it works for you LOL

kind of Confused

It's a good starting place, and those techniques, measuring the distance so that the drivers are all virtually aligned in space, will get you a lot of the way there and you'll be in the ball park.

However it's not quite as easy as that unfortunately.

First of all, drivers will have "group delay". This is a delay that (usually) increases as the frequency gets lower, but isn't just a simple delay, it's kind of a variable delay across the frequencies. So not so easy to compensate for by simply delaying for a certain amount of miliseconds. 

Partly it comes from the mechanics of the driver, and that it takes a little longer to get moving for big bassy notes than it does for a little compression driver to vibrate back and forth. Partly it also comes from the question of when exactly to you measure on the wave form: do you measure the start, the peak, half way?  Obviously these are very different distances/times for low frequencies than high. And partly it also comes from the design of the cab, whether its a band pass or a horn or a reflex etc. 

Then you've also got the fact that each time you add a crossover slope to change between the drivers, that adds a phase change, which in effect is another type of variable delay. And as the crossover regions are the parts that you need to pay most attention to when adjusting the delays it again adds a level of complexity to it.


What all this means is that the only real way to be certain is to measure it using dual channel software. 

An RTA (real time analysis) machine or piece of software measures one channel, and can tell you what frequencies it can hear in the room. However a dual channel measurement system measures te sound from the speaker, but importantly compares it to a direct feed from the mixing desk or cd player etc in the second channel, so it can work out time information as well as frequency information. How much delay was there between a frequency being played by the source, and actually hearing it from the speaker. 

Of course there are very expensive microphones and sound cards and software you can purchase for this, but you can also put these systems together fairly cheaply, a basic PC laptop that I'm sure you already own with some free software like Room EQ Wizard, and a half decent but not prohibitively expensive mic and soundcard combo will get you started (even the Berry mic will do for some basic phase measurements and to get you started, along with something like the Focusrite Sapphire sound cards which are very popular).  The graphs that are generated take a bit of getting used to, but they can really help you measure what's happening at your speakers and line everything up at the crossover points, and once you get your head around it all, then it'll REALLY start to click WinkLOL

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IainB View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IainB Quote  Post ReplyReply Direct Link To This Post Posted: 19 January 2018 at 7:05pm
Originally posted by kevinmcdonough kevinmcdonough wrote:

and once you get your head around it all, then it'll REALLY start to click WinkLOL

Argh!!! 
More food for thought and also makes sense, thank you for taking the time for a little further enlightenment Big smile 
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