New FAQ - How to design without measurement gear

[Pete00t]

Re: New FAQ - How to design without measurement gear

I wrote video game soundtracks for a while, .

Wrong place to ask this but. I and a few others are working on an Xbox live game. Its in early planning development. May we keep you in mind when the demo is closer to Beta? It is months off and I understand you are a new father with many responsibilities on your plate.

[Wolf]

Re: New FAQ - How to design without measurement gear

They're done! :D
Link below has links to both sections of Tips! Volume 3.

http://techtalk.parts-express.com/showthread.php?t=218978

There you go, Pete!
Wolf

[dlr]

Re: New FAQ - How to design without measurement gear

Yeah, the Chameleon writeup is excellent, and really does walk a person through the paces of speaker design. I put a link to it on my website not long after you did it.

I'm glad that some have found interest in it and hope that it's helpful. It sure took a lot of time to write.

dlr

[Pete00t]

Re: New FAQ - How to design without measurement gear

OMG i can actually understand it. thanks Wolf

[Wolf]

Re: New FAQ - How to design without measurement gear

No problem, Pete!
Later,
Wolf

[Paul Carmody]

Update: comparison to real-world measurements

The big question I have left unanswered so far is: "how accurate is this method?" Let's find out...

https://sites.google.com/site/undefinition/simulated-measurements2

[johnd]

Re: New FAQ - How to design without measurement gear

What would be good is explainations of Measurement Techniques.
People buy measurement equipment and do not have a clue on how to use it properly.
I have looked and there really only bits and pieces on how why etc.
What is the most common mistakes that are made when measuring.

[r-carpenter]

Re: New FAQ - How to design without measurement gear

my question is, why design without measurement gear???
Dayton mice and sound card with phantom cost very little. Arta and Holmi are free.
Why get involved in design then one can just copy a known design?

[dlr]

Re: New FAQ - How to design without measurement gear

What would be good is explainations of Measurement Techniques.
People buy measurement equipment and do not have a clue on how to use it properly.
I have looked and there really only bits and pieces on how why etc.
What is the most common mistakes that are made when measuring.

Get the book by Joe D'Appolito "Testing Loudspeakers".

dlr

[robert]

Re: New FAQ - How to design without measurement gear

Unfortunately, some of the measurement freeware out there is very tough to use. I won't touch ARTA with a stick, no documentation. As an electronics tech, measuring things and setting up test equipment came pretty naturally, getting the PC to do what it was supposed to was a whole different animal, and can be pretty much at the whim of the pc mfr. In other words, an individual experience, especially with laptops.

SoundEasy's measurement suite is non-obvious but by blindly following JohnK's CD and figuring out what was going on, I was pretty successful, and pretty much understand the process now. I read the manual too, a big help. You also have to practice it lots so setup and getting things to work is automatic. JohnK goes into farfield/nearfield splicing, how to ensure your splice was correct, etc. With sims, your bass response shows flat to F3, and it ain't so. Did I lose time when I could have made 6-7 speakers? Yes.

Measurement capability doesn't necessarily mean a good design, either. If you don't know what you are doing designing speakers, you'll get flat measuring designs that don't sound good. This can also happen with sims. In the end, I am happy that I took the time to learn it, but it would have been nice to produce, too. I agree with Paul - do a couple in sim, then break out and get some documented measuring software and equipment, and set up just like someone else that has been successful. Don't customize, don't buy that freakin' cool sound card you just have to have, get one that has worked for someone else without complex issues. I followed Dan Neubecker's rig, and used the same sound card. TA DA! It worked and I have never had a lag or delay issue with 2 different pc's. In fact, Ed and I shot some perfect minimum phase measurements a few weeks ago. Amazing, following a proven formula :D

Again, it took some time out of my building and buying drivers, but I bought myself a 12-pack when I had measurement, modelling, and sim all up in SE.

Cheers / Robert

[dano]

Go

"If you don't know what you are doing designing speakers, you'll get flat measuring designs that don't sound good"
Could you explain a little? Do you mean obvious things like crossing tweeters to low or woofers too high, or something else less obvious? I'm trying to learn all I can.
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SHINTO FORUM

[robert]

Re: New FAQ - How to design without measurement gear

When I built my 8" 2-way, I measured farfield/nearfield/port outputs and spliced them together. I also measured the 27TDFC. When I started designing the system, I shot for flat frequency response with about 4-5dB of baffle step compensation. I brought these to Iowa and they sounded heavy and dull compared to other's work.

2 reasons this happened:

1.) The cabinet and driver were capable of 28Hz or so and hit room modes with a vengeance, so bass response was heavy even though it measured as having considerable rolloff. I should have used a smaller cab, 1.4-1.5cf.

2.) With that bass response, keeping the driver's response near flat through the midrange made the system sound even heavier. Note that with a smaller driver, this may make the system sound more full, but with an 8, especially the HiVi, it wasn't a good idea.

When I reduced the series coil on the woofer and tweaked everything else out, it sounded much better, although the strong bass (lots would like it in their living rooms) is still a touch heavy, though much improved from Iowa. I may actually further reduce the woofer coil to see what happens. Easy enough.

Another issue: the Seas 27TDFC requires a series RC circuit to roll off the very top end a bit. When I measured, this looked pretty benign. When I listened, OUCH! You could hear scratchiness, something I hate from a tweeter. I looked at Zaph's SR-71 and used the same circuit tweaked a bit, and scratchiness away.

At Fort Wayne, I got Wolf feedback and ended up increasing the series resistor on the tweeter 1/2 Ohm to further sweeten the tweeter. Really good final touch.

So lots of things that looked good on measurement didn't sound good. Another argument for a proven design to compare.

Also, if the driver has high harmonic distortion, you need to dip it a bit where it peaks. This is because to the ear, it'll sound brighter than it measures, since the harmonics add to the output. I don't have a quiet enough house/neighborhood to do distortion measurements but hope to someday.

Cheers / Robert

[Paul Carmody]

Re: New FAQ - How to design without measurement gear

"If you don't know what you are doing designing speakers, you'll get flat measuring designs that don't sound good"
Could you explain a little? Do you mean obvious things like crossing tweeters to low or woofers too high, or something else less obvious? I'm trying to learn all I can.

That is an excellent question.

When I was first designing my own speakers, I figured "If the overall FR is flat, then it's all good. It all comes out in the wash." And really, since I started out using drivers with pretty flat FR, that theory pretty much worked for me.

But then after working with metal cone drivers, I started to notice that a speaker would have extra sibilance or a sort of "glassy" sound in the upper midrange/lower treble, even though its overall FR was flat. I realized that this was the breakup mode of the woofer; it didn't show up in the system FR, but it was clearly audible and annoying. So I learned how to use notch filters, and the extra sibilance went away.

"So why doesn't it all come out in the wash?" I'd wonder. Then I thought of an analogy that helped me. For example, say I were listening to an orchestra, and say the oboe was playing a counter-melody to the rest of the orchestra. If I were simply watching a VU meter of the performance I'd probably only see the peaks created by the orchestra as a whole. However, most people listening could probably pick out the oboe part with its counter-melody. For a non-classical example, think of a rock song with an acoustic guitar or tambourine added; again, it doesn't show up on the VU meter, but you can hear it.

[LouC]

Warning Possibly Heretical Controversy

I agree totally with Paul, particularly with metal cones. I know some tweeters (of any material) just grate on me when pushed too high.

Flat is probably a good goal, but if you do get there, most people find boxes voiced that way to be on the bright and edgy side. I recall Dennis Murphy visited Tucson once, and we chatted about that topic. I think we both agreed that a 1-2 db downward tilt from about 2K and up usually sounds better to most people in real rooms. (The BBC dip) (With your music, & your hearing...)

Personally, I design flat, then voice by ear. Usually that winds up with more tweeter padding. Sometimes I go back and start the whole crossover over again. Once it sounds right, I put the measurement gear away.

I'm a rock/pop/blues guy. Flat response often collapses the stage, and puts the vocalist right in my face. If the master/recording is poorly done, it sounds like someone is spitting in the microphone. I'd rather sit in the audience, than inside the band, but that's my preference.

Xavier came by my house one day, and played a couple of short pieces on his viola for my wife and I. In our carpeted great room, he sounded dead and tiny, when we moved into the kitchen, the difference in the life of the music was astounding. I'll bet they measured the same from 1 meter.

[dano]

Go

Thanks guys now were getting somewhere. I remember years ago I designed an auto system for IASCA competition. I designed and build the crossovers and we put everything in. When we finished and started listening to it everyone was pumped.

The owner and my installers were all high five-in, exclaiming how good it sounded. I said it aint right! I heard a faint raspy sound so I put a zoble on the mid woofers. That small change made the difference. The mids rising impedance defeated the crossover letting the mids play too high. I was hearing their cones breakup.

I don't know a lot about designing home speakers. I appreciate you guys helping me out. I'm not saying I was great at car stereo but I got by.
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