How to Design Loudspeakers without Performing Measurements

[DDF]

Hi all,
I've created a presentation explaining the usage of the free speaker design programs that Charlie Laub is kindly hosting on his site. The presentation illustrates a design method for those with without access to measurement equipment, and is geared towards users not yet intimately familiar with the programs. Also included are a number of design tips, tool usage tips, an introduction to *.frd files, and pointers to driver databases.

The programs include:

• Unibox - Excel Program for modeling the response of closed, vented, passive radiator and bandpass loudspeaker boxes
• BoxyCAD - Excel application for planning loudspeaker box construction including cut list and sheet goods estimation
• Baffle Diffraction and Boundary Simulator – Excel application for modeling the effects of baffle and room response
• Frequency Response Modeler - Excel application for manipulating FRD files in many ways
• Passive Crossover Designer - Excel application for designing passive crossovers and equalization
  
  and tools from the FRD Consortium
  
  
• Baffle Diffraction Simulator
• SPL Tracer - a utility for loading a picture file of a frequency response and automating the process of tracing over that response to create a FRD (Frequency Response Data) file for later import into other Acoustic Design Programs

You can find the presentation on Charlie's site (thanks Charlie), where most of the tools are also hosted:

http://audio.claub.net/software.html

Also included is a 12Meg zip file which illustrates step-by step an example design with these programs, including all the necessary .frd and .zma files.

This was originally created for the Ottawa Winter 2011 DIY meeting, and I hope you also find them useful.

Dave Dal Farra
Ottawa, Canada

[donradick]

Re: How to Design Loudspeakers without Performing Measurements

Thanks Dave!

Exactly what I need at this time.
Maybe you could have the mods put this into a permanent link in the "Designing Speakers" thread.

[[email protected]]

Re: How to Design Loudspeakers without Performing Measurements

canadians rock.

[theLinks]

Re: How to Design Loudspeakers without Performing Measurements

Thanks Jeff, Charlie and Dave! And the rest who give back to this hobby!
Tim

[Jeff B.]

Re: How to Design Loudspeakers without Performing Measurements

Hi all,
I've created a presentation explaining the usage of the free speaker design programs that Charlie Laub is kindly hosting on his site. The presentation illustrates a design method for those with without access to measurement equipment, and is geared towards users not yet intimately familiar with the programs. Also included are a number of design tips, tool usage tips, an introduction to *.frd files, and pointers to driver databases.


The programs include:

• Unibox - Excel Program for modeling the response of closed, vented, passive radiator and bandpass loudspeaker boxes
• BoxyCAD - Excel application for planning loudspeaker box construction including cut list and sheet goods estimation
• Baffle Diffraction and Boundary Simulator – Excel application for modeling the effects of baffle and room response
• Frequency Response Modeler - Excel application for manipulating FRD files in many ways
• Passive Crossover Designer - Excel application for designing passive crossovers and equalization
  
  and tools from the FRD Consortium
  
  
• Baffle Diffraction Simulator
• SPL Tracer - a utility for loading a picture file of a frequency response and automating the process of tracing over that response to create a FRD (Frequency Response Data) file for later import into other Acoustic Design Programs

You can find the presentation on Charlie's site (thanks Charlie), where most of the tools are also hosted:

http://audio.claub.net/software.html

Also included is a 12Meg zip file which illustrates step-by step an example design with these programs, including all the necessary .frd and .zma files.

This was originally created for the Ottawa Winter 2011 DIY meeting, and I hope you also find them useful.

Dave Dal Farra
Ottawa, Canada

Dave,

Thanks, this looks excellent, but I do have a question. Why advise the user to "add a small amount of delay" using the Response Modeler to adjust for the woofer's offset and not enter any Z-offset in PCD? First, how much is a "small amount of delay" that would make for an accurate adjustment? Leaving the driver as minimum phase and adding in offsets in the Passive Crossover Designer has two significant advantages: First, it is much more accurate in establishing the correct amount of delay, as -.020 to -0.024 Meters works well over a wide range of small woofers. Second, once entered, the designer now can model the interaction of the drivers on different vertical and horizontal axes, which is a powerful piece of information in the design process as well. I personally feel this is a much better approach and similar to the one we grew up with using CALSOD.

Jeff B.

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

Dave,

Thanks, this looks excellent, but I do have a question. Why advise the user to "add a small amount of delay" using the Response Modeler to adjust for the woofer's offset and not enter any Z-offset in PCD? First, how much is a "small amount of delay" that would make for an accurate adjustment? Leaving the driver as minimum phase and adding in offsets in the Passive Crossover Designer has two significant advantages: First, it is much more accurate in establishing the correct amount of delay, as -.020 to -0.024 Meters works well over a wide range of small woofers. Second, once entered, the designer now can model the interaction of the drivers on different vertical and horizontal axes, which is a powerful piece of information in the design process as well. I personally feel this is a much better approach and similar to the one we grew up with using CALSOD.

Jeff B.

Jeff,
I think this is one of those tomato, toe-matt-oh cases, either way works. I recommended the same offsets in the slides (slide 13), but personally feel its better if the actual frd file contains the delay offset. This replicates what you would get from real measured files.

The user can then still dial in additional delay via the PCD to see the lobe move over various vertical angles.

Dave

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

canadians rock.

No, we Kick Axe, and I have the t-shirt to prove it!

[dlr]

Re: How to Design Loudspeakers without Performing Measurements

Jeff,
I think this is one of those tomato, toe-matt-oh cases, either way works. I recommended the same offsets in the slides (slide 13), but personally feel its better if the actual frd file contains the delay offset. This replicates what you would get from real measured files.

The user can then still dial in additional delay via the PCD to see the lobe move over various vertical angles.

Dave

I don't know how much difference it makes in typical cases, but I agree with Jeff because I believe it's the more accurate model if one is going to examine the off-axis.

dlr

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

I don't know how much difference it makes in typical cases, but I agree with Jeff because I believe it's the more accurate model if one is going to examine the off-axis.

dlr

If you mean also entering the driver position on baffle (x,y,z), then I 100% agree. I didn't get into that. Personally, I don't use PCD that way. I could always add it to a future version of the presentation, but no time in the near future to do so.

I think the presentation offers alot of value as it stands.

[Paul Carmody]

Re: How to Design Loudspeakers without Performing Measurements

That was very nice of you to do that, Dave! I hope it enlightens a few more budding designers!

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

That was very nice of you to do that, Dave! I hope it enlightens a few more budding designers!

Thanks Paul, that's my goal!

[rogoll]

Re: How to Design Loudspeakers without Performing Measurements

Just a suggestion, but what I did was download and extract the zipped files, and then, in the same sub-directory, I "right-clicked" on the link to the tutorial/PDF file and selected the "save target as" to save the PDF along with all the sample files. This way you have the tutorial locally on your hard disk.

[Jeff B.]

Re: How to Design Loudspeakers without Performing Measurements

Jeff,
I think this is one of those tomato, toe-matt-oh cases, either way works. I recommended the same offsets in the slides (slide 13), but personally feel its better if the actual frd file contains the delay offset. This replicates what you would get from real measured files.

The user can then still dial in additional delay via the PCD to see the lobe move over various vertical angles.

Dave

It's really not the same either way. You can't simulate off-axis lobing in PCD without the x,y,z offsets being entered, so you give up a powerful tool in seeing the response family over a wider window.

Don't get me wrong, this is my only qualm. I think your tutorial is very well done, and thank you for creating it.

Jeff

[DDF]

Re: How to Design Loudspeakers without Performing Measurements

It's really not the same either way. You can't simulate off-axis lobing in PCD without the x,y,z offsets being entered, so you give up a powerful tool in seeing the response family over a wider window.

Don't get me wrong, this is my only qualm. I think your tutorial is very well done, and thank you for creating it.

Jeff

Jeff,
dlr's response clarified what you were getting at and please see my response to him. I could always add this in a future edit.

[charlielaub]

Re: How to Design Loudspeakers without Performing Measurements

It's really not the same either way. You can't simulate off-axis lobing in PCD without the x,y,z offsets being entered, so you give up a powerful tool in seeing the response family over a wider window.

If you mean also entering the driver position on baffle (x,y,z), then I 100% agree. I didn't get into that. Personally, I don't use PCD that way.

If one is using manufacturer supplied measurements and impedance curves modeled from MFG T/S parameters, I think DDF's suggestions about offset are valid because the level of approximation about the phase and amplitude data for the drivers is already high.

But for those who do a full blown design, I'd like to chime in on the point that Jeff made, so please read on...

It is a mistake to optimize a speaker based solely on the on-axis response, although that is a good top priority. This is because some topologies can result in severe off-axis lobing (nulls or peaks in the response) in the crossover region while the on-axis response remains mostly flat. This is especially true for low order (e.g. 2nd order) crossovers, which have more driver FR overlap. Off-axis anomalies will color the sound. Off-axis energy is reflected back to the listener from the room and perceived as part of the over all tonal balance of the speaker, even when listening on-axis.

Jeff's point is that, in order to model accurate on and off-axis responses in PCD, you need accurate data on the offsets. Without good offset info, you can't utilize PCD to its fullest potential.

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