How to Design Loudspeakers without Performing Measurements

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

I urge everyone to determine offsets as best as possible, get the frequency response looking good on axis, and then explore a few off axis angles within a +/- 30 degree window to make sure there are no nasty surprises in there. Maybe this is what people do, and maybe not, I am not sure.

-Charlie

Absolutely right Charlie. I didn't get into that level of design detail in the presentation as it was meant as a tool training aid, not a design tutorial. We could fill many pages herein discussing that topic.

FWIW, in design, I put most importance on the direct axis response, followed by the response at the angle that corresponds to the first side wall reflection, followed by the angle that corresponds to the floor bounce, followed by a general +/- 45 deg "wellness" view. Dips are relatively OK, peaks, not so much.

One other thing i need to stress is that it's important to do a good job on the diffraction modeling and splicing. Changes in <150Hz level relative to 1 kHz of even 1 dB has a profound effect on the tonal balance. Thin and brittle results from too soft a mid bass.

Dave

[gowa]

Re: How to Design Loudspeakers without Performing Measurements

Thanks Dave.

[DDF]

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

Hi folks,
The typo was corrected and Charlie has uploaded the update to his site.

Dave

[gowa]

Re: How to Design Loudspeakers without Performing Measurements

Thanks again Dave.

[[email protected]]

Re: How to Design Loudspeakers without Performing Measurements

Added to The Speaker Building Bible. Thanks for the time and effort that went into this!

[ripcard]

Re: How to Design Loudspeakers without Performing Measurements

Way to go Dave! Too bad we didn't make the time at the DIY meet for you to present this. Maybe next one?

[fntn]

Re: How to Design Loudspeakers without Performing Measurements

How do you obtain accurate offset data without "measurements"? :D

Maybe a ban on crossovers higher than 1500hz would make that whole issue go away.

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

Thanks Gowa and Rick. Rick, I'd be happy to field any questions at the next DIY.

fntn, use the approximations shown in the slides. They're close enough. If you have other driver sizes to worry about, measure where the voice coil attaches to the cone and use that as the approximate recess behind the baffle for teh driver acoustic center. It will get you close enough. If it doesn't, it means that your xover has really tight lobes with nulls near on axis, never a great thing anyway (ie you'd have bigger issues in that case).

[Taterworks]

Re: How to Design Loudspeakers without Performing Measurements

Designing speakers without measurements: http://www.youtube.com/watch?v=crPp7LOduJM

In my opinion, the notion of developing a quality speaker design without making even one set of measurements is silly, and its validity is wishful thinking.

You either need to measure to design, or you need to measure in order to validate the simulations. But if you don't measure, you'll never know if your design came out right, and might be caught with your fly unzipped at a DIY event or when a more well-traveled audio enthusiast stops by your place with some of his own source material for a listen. Every serious designer needs to have access to a means of making FR magnitude measurements and impedance measurements (a mic and a WT3 suffice), and they are as essential to diagnostics as to design, so it makes sense to consider making the investment.

That said, with the kind of accuracy one can manage with a simulation, and with the difficulties in setting up a space in most rooms that can make good measurements of a speaker, I'm leaning heavily toward the second option these days: measure to validate. It's less work overall.

My $.02

[fntn]

Re: How to Design Loudspeakers without Performing Measurements

Thanks Gowa and Rick. Rick, I'd be happy to field any questions at the next DIY.

fntn, use the approximations shown in the slides. They're close enough. If you have other driver sizes to worry about, measure where the voice coil attaches to the cone and use that as the approximate recess behind the baffle for teh driver acoustic center. It will get you close enough. If it doesn't, it means that your xover has really tight lobes with nulls near on axis, never a great thing anyway (ie you'd have bigger issues in that case).

:D I was just joking about the thread title - "without performing measurements". I use impulse recordings to get precise measurements of raw drivers in the baffle.

[fntn]

Re: How to Design Loudspeakers without Performing Measurements

Designing speakers without measurements: http://www.youtube.com/watch?v=crPp7LOduJM

In my opinion, the notion of developing a quality speaker design without making even one set of measurements is silly, and its validity is wishful thinking.

You either need to measure to design, or you need to measure in order to validate the simulations. But if you don't measure, you'll never know if your design came out right, and might be caught with your fly unzipped at a DIY event or when a more well-traveled audio enthusiast stops by your place with some of his own source material for a listen. Every serious designer needs to have access to a means of making FR magnitude measurements and impedance measurements (a mic and a WT3 suffice), and they are as essential to diagnostics as to design, so it makes sense to consider making the investment.

That said, with the kind of accuracy one can manage with a simulation, and with the difficulties in setting up a space in most rooms that can make good measurements of a speaker, I'm leaning heavily toward the second option these days: measure to validate. It's less work overall.

My $.02

+1

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

Every system I've designed for the last 25 years has been based on acoustic measurements. I've taken thousands, in and out of anechoic chambers. I've contributed to IEEE standards on it.

But not everyone is that fortunate, either in dollars, or time to learn all the ins and outs. I put this together for those without access to measurement gear, so they can still get well within voicing range, enjoy the hobby and make themselves a good sounding design they can be proud of. No shame in that.

Dave

[raiderone]

Re: How to Design Loudspeakers without Performing Measurements

Every system I've designed for the last 25 years has been based on acoustic measurements. I've taken thousands, in and out of anechoic chambers. I've contributed to IEEE standards on it.

But not everyone is that fortunate, either in dollars, or time to learn all the ins and outs. I put this together for those without access to measurement gear, so they can still get well within voicing range, enjoy the hobby and make themselves a good sounding design they can be proud of. No shame in that.

Dave

Thanks. And even if one does have the measurement equiptment, most do not have the resources to buy and measure every driver contemplated for a build. This resource is also useful in selecting potential drivers for a build.

[donradick]

Re: How to Design Loudspeakers without Performing Measurements

I'm working an a budget MT design using this guide, and have come to a sticking point on Slide 11 - using the Frequency combining worksheet and Splview normalizing on page 10.
1: While most FR plots cover 20Hz to 20KHz, Unibox puts out FRDs that end at 1000Hz. Is this a problem? Should I choose 20KHz to normalize the Unibox file also?
2: for the FRC worksheet, there are a number of sections that do not coorsespond directly to the DDF explanation on Slide 11. Can you tell me which section to load each source FRD into? (Driver base is obviously the manu frd, but which section for BDS transform - "Baffle Measure" and Unibox frd - "Box Measure"?)

Thanks again for the guide. I never really understood all the tools and the data flow through them as input to PCD.