Please help the noob (me)

A Jedi

Member
2019-05-01 9:53 pm
Hey gang, I'm designing speakers for the first time and have some specific questions. First question is, are the below steps correct:

1) measure T/S of drivers
2) use software like REW, XSim, VituixCAD, etc. to design cab
3) measure FR with drivers in cab
4) design crossover based on FR and Impedance curves
5) tweak crossover until the cows come home :spin:

My second question is specific to driver measurements.
1) Is the DATS V3 (I know it's not available yet but I assume it's similar in performance to V2) competent enough for T/S measurements
2) when it's time for FR measurements, is the OMNI Mic competent?
3) how are measurements done (T/S and FR) so as to not to blow tweeters with low frequencies

Thanks much!

Alex
 

ILikeFoodz

Member
2014-06-22 12:33 pm
On the whole I'd say your approach looks good. For the tweeter, run the frequency sweep starting below where you intend to cross it, but above its resonant frequency and not at too high a volume (2.83 volts would be pretty standard). If you want, you could put a capacitor in series with it too that would start its rolloff in that range somewhere based on the datasheet impedance curve, just make sure to remember if you do when designing your crossover. Also, if you're using a ribbon tweeter or any type that's a dead short to the amp, you MUST use something in series with it (cap and/or resistor).

Just fyi, I've found it very difficult in practice to get good measurements myself that are more useful than the datasheet. Doing the tests outside would help because that eliminates room resonances.

Also, I've used all the software you mentioned, and for measurement I like REW best, and I found I get my best results using WinISD and VituixCAD for design. I also use a program like SketchUp or Fusion360 for doing the full cabinet design.
 

ILikeFoodz

Member
2014-06-22 12:33 pm
Also forgot to mention: driver burn-in is an important step before measuring TS Parameters. One common way to do it for non-tweeters is to play a tone at Fs at a level that's just below max excursion for several hours. Be careful too, because as the surround becomes more compliant due to heating and getting broken in, excursion will rise a bit, which can cause the driver to exceed Xmax if you started too close to Xmax.
 

turk 182

Member
2012-10-26 3:03 pm
could be four rather then six amp channels, mid/high can be passive no?


so it's a three way design your going for, correct? depending on driver selection and x-over freq. going active for a low end to mid cross could prove advantageous and large value inductors get pricey fast, copper ain't cheap (maybe i should look at copper stocks!?!)
 
4) design crossover based on FR and Impedance curves
5) tweak crossover until the cows come home :spin:

What is your music source? If all your media will be played via PC, you can use global EQ (e.g. free software, like equalizer APO) and vastly simplify these two steps.

The passive crossover can be very simple if all the level matching and so on are done actively.

1) Is the DATS V3 (I know it's not available yet but I assume it's similar in performance to V2) competent enough for T/S measurements

If this is the only project you'll build, you could simply skip buying the tester.

Just get good brands / parts that are already known to the DIY community (that don't really need testing). The Peerless 8" model XYZ that someone measured 2 weeks ago will be very close the the Peerless 8" model XYZ that you buy today.

2) when it's time for FR measurements, is the OMNI Mic competent?

Any calibrated mic will be accurate enough.

Particularly if you use active eq, the $15 Dayton Audio iMM-6 (and a $5 app) is worth considering.
Dayton Audio iMM-6 Calibrated Measurement Microphone for Tablets iPhone iPad and Android

Something like the OMNI Mic or the UMIK-1 is better for plugging into a PC / Mac, that is, they are better mostly for the interface. If you want to overlay multiple charts, these mics clearly win. You can do 25 measurements with the mic at various points, then change a crossover part, repeat the 25 measurements, then overlay the two sets of before-and-after plots to see which configuration is best. That has a certain nerdy satisfaction, but gets pretty boring if you just wanna play some music.

If you aren't a perfectionist, and you just want to tweak your active eq to get a decent response over the listening area, the Dayton Audio iMM-6 is probably a better tool.

(as far as I know) OMNI Mic or the UMIK-1 only take measurements at a single point. You can use them 'perfectly' to get the average (power response) over a listening area, but you have to measure and then average out a whole lot of individual points.

To do a rigorous before-and-after test means that after the change, you have to repeat the whole lot of measurements, re-placing the mic in the exact same positions. This means putting markers all over your floor and being fastidious about setup - some of your results will change if someone opens a door, or moves a chair, or if the mic stand is set up differently.

With the iMM-6 + an active eq, the same task takes about 10 seconds: just press 'average' on the app and simply wave the mic across the listening area. If non-flat, simply change the eq and repeat.
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General advice = pick a project that is reasonably noob friendly:

a) simple (ish) box
b) drivers with a decent amount of smooth overlap

...then your crossover can be simpler, and your measurements won't need to be perfect.

Also, some slop factor is good. Building the box slightly too big is better than too small.
 

A Jedi

Member
2019-05-01 9:53 pm
What is your music source?

Source is either lossless files or CD transport.

If this is the only project you'll build, you could simply skip buying the tester.

There will be 2 to start with - a desktop/bookshelf 2 way and a floor stander 3 way with MTM top end. And I'm pretty sure I'll want to do a high sensitivity speaker afterwards. So at minimum 3.

You can do 25 measurements with the mic at various points, then change a crossover part, repeat the 25 measurements, then overlay the two sets of before-and-after plots to see which configuration is best. That has a certain nerdy satisfaction, but gets pretty boring if you just wanna play some music.

That's the thing, it's not just about the music. I started out doing car audio systems back in the day (professionally) and loved fabricating, tweaking etc. (I was a SQ guy). I did home audio afterwards as well but didn't care for it since only like 1 out of 100 customers actually had a clue and cared about fidelity to the nth degree. All the rest just care about loud and fancy looking equipment. Point being, I can do 25 measurements and be pissed off about it but then the satisfaction of getting things right is totally worth it.

To do a rigorous before-and-after test means that after the change, you have to repeat the whole lot of measurements, re-placing the mic in the exact same positions. This means putting markers all over your floor and being fastidious about setup...

Yup - I'm that guy lol

General advice = pick a project that is reasonably noob friendly:

The only thing missing from my repertoire really is the crossover design (the easiest part I know :D ). I also wanted to make sure I'm taking the steps in a methodical manner to arrive at a successful design more efficiently.

Thanks for your comments though. Any new knowledge is a good thing.
 
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