Speaker Asylum

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In Reply to: RE: What measuring tool? posted by kellymon on May 15, 2008 at 16:12:05

But will get you nowhere without at least a decent measuring suite plus some time spent learning how to measure and interpreting what you see on the pretty graphs.
The first thing people realize is that pretty "theoretical" mirror-imaged electrical textbook crossovers are almost never called for in real-life designs. Mos designs incorporate the acoustic rolloff of one or more drivers, which can add up to 12db/octave in addition to the electrical filter. (A lot of guys who are using only caps and assume they have a 1st order design really have 1st order *electrical* filters with a net 3rd order acoustic response due to a 2nd order driver rolloff they did not account for.)
There are SO many things that affect response of a driver on a common baffle that it's really difficult to see (at first) cause and effect relationships.
I would start with a good newbie speaker design book like this one from David S Weems.
http://www.amazon.com/Designing-Building-Testing-Speaker-Projects/dp/007069429X/ref=sr_1_1/002-7360838-4523255?ie=UTF8&s=books&qid=1210895946&sr=1-1
Sure, you won't learn how to implement linear-phase FIR digital filters or how to design transient perfect subtractive delay speakers, but you'll get loudspeakers 101 (and maybe a little 102) plus some neat project ideas.
For total newbies I HIGHLY recommend kits: ket a nice kit from Madisound, Zalytron, Solen, Orca, or Parts Express. Then, you get the fun of building your own speakers, plus then you can try out your measuring suite and REVERSE ENGINEER the kits you've built after you're done. This way you can see what the design intention was and how the design came to be. This "measure an already properly designed speaker" technique has advantages to just starting from scratch and measuring random drivers on random baffles. I know it helped me a lot.
Everyone who starts off in speaker building is usually a very optimistic and eager person thinking that they can pop some quality drivers with smooth looking response curves into a box and get good sound with a simple crossover. The truth is, this is a stretch for the speaker building Newbie. The biggest danger of DIY is the "I did it myself" effect on what you hear. I remember the first time I heard my first set of speakers - I as so amazed at the sound! (Or just amazed they actually MADE sound). Now, my brother has these speakers and I can't even listen to them. They're that bad. My dad never DID like them... I could tell by his facial expressions that all the woodworking we did, to him anyways, was not really worth it!
The first thing to STOP doing (let me save you months or years of time here) is looking at manufacturers curves provided for raw drivers. I used to drool over these and make AMAZING theories about how these drivers would perform in a typical baffle. Ha ha. Not quite. Some manufacturers use an infinite baffle. Some use a test enclosure. Some compensate for baffle step. Others do not. Some use more smoothing than others. Just having two different VERTICAL SCALES on two different graphs can be VERY misleading to the untrained eye. You usually CANNOT COMPARE two drivers based on measurements if they are not done in exactly the same way. All driver response curves from manufacturers do is give ideas about over-all response smoothness, when break up starts, signs of edge or surround roll diffraction. Comparing comparable drivers from the same manufacturer can be information - comparing drivers from two DIFFERENT manufacturers can result in very misled driver selection.
I would read the Weems book, and consider starting with a kit. I was told this 1000 times before I started and I never listened. Feel free to follow in my footsteps and flounder for years, or be a bit smarter if you like! :o)
Cheers,
Presto

Edits: 05/15/08

Follow Ups:

Thanks for the good suggestions - kellymon 18:20:14 05/15/08 (0)

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