My speaker design program, updated

[will33]

My boxes are largish. If you were to modify Francis compact box to show zero port, you should see the airspring effect that doesn't allow excursion to keep rising beyond some point.

 

[fdeck]

Love it.

Question, in your modling software, how would you tackle a sealed cab?

I've been entering a very low value for the port tuning (e.g., 1 Hz) and ignoring the port air speed graph. Next time I crack it open, I'll add explicit support for sealed designs, just to make sure there are no numerical gotchas.

Wow, thanks for the responses! It's cool to see a design be debated and refined in real time on a forum. I'll claim that as a feature. Also, I will look into a way of time-stamping the URL's to keep track of which design is the most up-to-date.

 

[DukeLeJeune]

Great program, Francis! Thank you for making it freely available!

Without divulging any secrets, can you give us a ballpark idea of how you derive the waveform-based excursion? I presume you reduce the excursion requirements based on estimated distribution of the total energy across the harmonic sequence, and I also presume that the devil be in the details.

 

[will33]

Invalid Link Removed

That should be an 8ohm FaitalPro 10FE200 in a 7/8ths cu.ft (24.5 liter) box. "Sealed" by entering 0's for all your port info.

The response looks reasonably close to my WinISD model of the same.

The excursion is quite different though. My WinISD shows a very noticable airspring effect that won't let it overexcurse, rather just make it cook any extra power off as heat. **


** This may be due to a faulty Vas entry. If "dm^3" isn't the same as a liter, the model may be fine and pilot error is the culprit.

Dodging traffic here.

 

[will33]

Great program, Francis! Thank you for making it freely available!

Without divulging any secrets, can you give us a ballpark idea of how you derive the waveform-based excursion? I presume you reduce the excursion requirements based on estimated distribution of the total energy across the harmonic sequence, and I also presume that the devil be in the details.

That was my very limited educated guess. Real world power demand reducing with increasing frequency.

Stands up to my empirical "crank it up and see what happens" test methods.

Going by constant power test tone input, I should be farting out lots of cabs that I'm just not farting out, at least not until much louder than predicted levels. And they're not any sort of super-excursion mega-woofers either.

Whatever WinISD says I can do with sinewaves, I default to being able to do double that with a bass string when it comes to power input.

That's no calculated number either, just an estimation.

 

[DukeLeJeune]

Whatever WinISD says I can do with sinewaves, I default to being able to do double that with a bass string when it comes to power input.

That's pretty much the same fudge factor I use. If I'm cutting it close, I'll try to avoid box size + tuning combinations where the excursion on the fundamental + the excursion on the first overtone look like they might add up to a fart.

 

[fdeck]

Great program, Francis! Thank you for making it freely available!

Without divulging any secrets, can you give us a ballpark idea of how you derive the waveform-based excursion? I presume you reduce the excursion requirements based on estimated distribution of the total energy across the harmonic sequence, and I also presume that the devil be in the details.

I'm happy to divulge! In fact, it's open source. If you do Ctrl-U in Google Chrome, my source code will display.

Long ago, I looked at the output of my bass on a scope, and found that I could replicate the waveform pretty well as a sum of the first few harmonics, equally weighted. So, it's the harmonic structure of the open A string of my passive Ibanez. Not very scientific, but I felt it was probably sufficiently representative of an electric bass when run through an amp without too much bass boost. I could add some settings so you could change the weighting factors, for instance to use the fundamental plus first overtone as you mention. I tried more elaborate algorithms, and they didn't change things very much.

This was my attempt to understand if there was a difference between the rather pessimistic "peak" excursion graphs that are typical of the free design software, and the realistic power handling of a bass speaker.

I might be completely swamped this weekend and next, but I'd like to begin adding drivers and maybe even complete designs to the library page.

 

[astack]

So cool! Big thanks for all your work on this.

Here are my ideas:

Drop down menu of default drivers. There are probably a dozen favorites we talk about a lot here. ##PR###, 301#'s, 2512's, betas, alphas, etc.

Design comparisons: it may look like having 2 or 3 columns of the same calc to see side by side, especially for on a phone where you can't have side by side windows.

Phase delay graph? Is this useful to people? I've just thought about it in regards to sealed vs ported.

It seems like the port data and tuning aren't coupled, i.e. if I change the size/number of ports it doesn't update the tuning.

Is it possible to have the graph extents fixed rather than zoom to fit? It would make comparisons easier.

This might be going beyond the intended scope, but I have a spreadsheet template I use to go from WinISD to box dimensions. Maybe something like that added to the bottom or a second page to click through to. Input things like volume overage factor, panel thickness, grill offset, port dimensions (read from above) and 2 outer dimensions. That way in a couple minutes of tinkering you could be ready to cut wood, which would be very cool.

 

[T_Bone_TL]

Invalid Link Removed

As best I can, this is the SP 15425 Scorpion driver in the Peavey TNT130 as it sits. Le is guesstimated since I cannot find it and Peavey didn't give it to me when they did send along a few parameters not in the data sheet (and some others somewhat different from the data sheet) - I noted that the 4 ohm BW I found one for was half the 8 ohm BW I also found one for, so I found an 8 Ohm Scorpion number from Parts Express, and cut it in half. Could be quite utterly wrong.

Xmax as supplied by Peavey is +/- 3.0mm - they do mention that some other makers use 6.0mm to describe the same thing. I'm not sure which is right to use for your model. Not much by modern standards.

The Box port & tuning is also a guesstimate - 3.75 inch single triangle, what I entered should be a square port of same area, tuning was adjusted to get the "length" reported to equal the baffle thickness since that's all the "port" is - a hole in the baffle.

WRT @astack comment that the size and number of port does not seem to change tuning, pay attention to the port length it calculates. The frequency and frontal size are inputs, the port length is down at the bottom of the outputs, and does change. However, number of ports does not seem to affect the calculated length, and presumably should, as 2 ports are twice as large as one port, and one port twice as large gets a longer length. Or the length and width are considered totals, not per port (but in that case number of ports would not matter...)

It certainly does illustrate that there is much room for improvement to the TNT130 via a new cabinet (which is a project I am v-e-r-y slowly working on, and got a lot of input from dhsierra a long time back that I have yet to act on.)

Screwed up Sd - should be right now. Hmm. I entered 200W for Pe, but when I copy the url and follow it, the Pe changes to 250W. Makes no real difference, but....

 

[T_Bone_TL]

Francis has been hard (if quietly) at work, and has nicely implemented some things that were mentioned in this thread...

http://www.talkbass.com/threads/diy-angle-cab-what-would-you-load-it-with.1125175/page-3

So the SPL curve now has both 1-watt response and the response for the entered amp power, and everything is more clearly labeled.

 

[Jim Carr]

Very cool.

 

[fdeck]

However, number of ports does not seem to affect the calculated length, and presumably should, as 2 ports are twice as large as one port, and one port twice as large gets a longer length. Or the length and width are considered totals, not per port (but in that case number of ports would not matter...)

Uh-oh. I'd better take a look at my code for that part.

 

[fdeck]

And... fixed.

 

[Vince Klortho]

I'm happy to divulge! In fact, it's open source. If you do Ctrl-U in Google Chrome, my source code will display.

Long ago, I looked at the output of my bass on a scope, and found that I could replicate the waveform pretty well as a sum of the first few harmonics, equally weighted. So, it's the harmonic structure of the open A string of my passive Ibanez. Not very scientific, but I felt it was probably sufficiently representative of an electric bass when run through an amp without too much bass boost. I could add some settings so you could change the weighting factors, for instance to use the fundamental plus first overtone as you mention. I tried more elaborate algorithms, and they didn't change things very much.

Invalid Link Removed shows a graph (Figure 3) and a chart that lists the relative outputs of the harmonics of an open E from a Precision.

 

[fdeck]

Invalid Link Removed shows a graph (Figure 3) and a chart that lists the relative outputs of the harmonics of an open E from a Precision.

Thanks! That's basically what I observed. I was able to influence the relative strength of the harmonics somewhat by plucking in different ways, playing different strings, etc. But the changes weren't massive. What I decided to do was leave it as an un-weighted sum of the first four harmonics (in the JavaScipt program), no correction for phase. I also played with a number of "better" models (summing the waveforms instead of the amplitudes, etc.) that didn't have much of a practical impact on the graphs, so I figured it was good enough for practical use.

As a cautionary note, EQ changes the game, and a lot of bassists use a "scooped" EQ built into their amps that probably adds strength to the fundamental.

 

[OldogNewTrick]

Francis, thank you. Great effort from you and great fun for me to play with !

However, I cant't seem to get it to display the graphs when executed from my hard drive.
Is my directory structure correct?

... :\Privat\DIY Box\flot\speakerjs\speaker.html
... :\Privat\DIY Box\flot\speakerjs\speaker-Dateien containing jquery.js and jquery_002.js

 

[fdeck]

Francis, thank you. Great effort from you and great fun for me to play with !

However, I cant't seem to get it to display the graphs when executed from my hard drive.
Is my directory structure correct?

... :\Privat\DIY Box\flot\speakerjs\speaker.html
... :\Privat\DIY Box\flot\speakerjs\speaker-Dateien containing jquery.js and jquery_002.js

When I run it on my hard drive, my directory looks like this:

The "flot" directory is from this file:

http://www.flotcharts.org/downloads/flot-0.8.3.zip

jquery is inside the "flot" directory. If this doesn't work, let me know and I will create a zip file that you can download, with the entire package.

 

[OldogNewTrick]

Francis, thanks, got it, however....

My mistake was (in Firefox) to download the page as "web page complete" and not just "html only"

So, instructions for others to avoid the pit I fell into:
Download as "html only"
Place in a directory. Place "flot" directory one level below (sub directory)

Works just fine now. Thanks.

 

[fishdreams]

Wow, I am definitely going to look at that, after just finishing my own first wet-finger-in-the-wind designed cab (Comparatively speaking). Thanks!!

 

[nekomatic]

The speaker design page gives a 'forbidden' error for me since a few weeks ago...