Boxplot and other cabinet software

[airboss]

As I said yesterday. I know nothing! Anyway, about certain things....other things I'm a virtual encyclopedia of irrelevant information.

I have used Boxplot software for years and more or less accepted it as being the way to go for the DIY speaker builder. Never have built anything it outputs, just goofing off and spending my time doing other stuff.

So I run the Boxplot on the 416-c woofer and it tells me to put it in a 2 1/2 '^2 box with a round port and expect a 3db down point around 60 hz.

When you fool with the alpha and H parameters you can see what it will do with various other boxes but really it doesn't ever measure up to what I expect when I model the Model 19 as drawn. It gets down there in a ported 13^2' box. This is puzzling to me. Is the crossover equalized to bring the bass down? Do Altec woofers simply not play by Thiele-Small rules? Or is the room what brings the bass down on the Mod 19? All of the above? Or is that 3db down point real and our minds fill in the blanks for us?

According to some bologna a set of Seas 4" aluminum cone woofers outperform an Altec 416. Horsefeathers. Can you imagine a set of those little turds in an auditorium filled with movie goers watching Space Odyssey?

Something is either wrong with my expectations or somebody is full of it.

Help requested

[Earl K]

As I said yesterday. I know nothing! Anyway, about certain things....other things I'm a virtual encyclopedia of irrelevant information.

I have used Boxplot software for years and more or less accepted it as being the way to go for the DIY speaker builder. Never have built anything it outputs, just goofing off and spending my time doing other stuff.

So I run the Boxplot on the 416-c woofer and it tells me to put it in a 2 1/2 '^2 box with a round port and expect a 3db down point around 60 hz.

- BoxPlot does return results that are usually corroborated by other woofer alignment programs ( therefore it's not out to lunch, IME ) .

- OTOH, why are you letting it tell you anything ? / or put another way / why are you accepting BoxPlots dictation/direction:coffeedrinker: ?

- What happens when you demand that it to draw out the response curve of a 416-8C woofer ( installed in a 7.5 cu ft box & tuned to 30 hz ) ?

( Does BoxPlot get pissed off and leave the room or does it comply ?)

<> cheers Earl K

[airboss]

- BoxPlot does return results that are usually corroborated by other woofer alignment programs ( therefore it's not out to lunch, IME ) .

- OTOH, why are you letting it tell you anything ? / or put another way / why are you accepting BoxPlots dictation/direction:coffeedrinker: ?

- What happens when you demand that it to draw out the response curve of a 416-8C woofer ( installed in a 7.5 cu ft box & tuned to 30 hz ) ?

( Does BoxPlot get pissed off and leave the room or does it comply ?)

<> cheers Earl K

Operator error? How could that possibly be? Garbage in garbage out. eh? :doh: The thought has occurred to me actually. I'll keep at it. I have been able to get the response curve I want by working alpha and H from the box parameter window, but I don't think I've quite figured out the whole magilla. You've answered my question though. It works, I don't. :thankU:

[Earl K]

I find it best to use a few programs and then make sure that they mostly agree .

You'll find that they all have the unspoken bias(es) of the programmers built into the code .
These biases can lead one down the garden path ( so to speak ) and into unwarranted conclusions .

I find these bias(es) will become ( at the very least ) annoyances when one just wants to get from A, over to Z .

Anyways ( as a suggestion & assuming you're using a PC )

• Download LinearTeams WinISD (Pro) and give it a go ( it's shareware ) .
  
• It's a pretty interesting program in its own right .
  
• I'd say it's biggest quirk ( feature ) is that it implements auto-checking for all of the TS parameters that a person attempts to enter into it .
  
• This ( feature ?) disallows non-sensical ( "garbage-in" ) TS measurements .
  
• As a result , it's best to let WinISD auto calculate some of the parameters // when inputting the TS values for a speaker not yet represented in its library ( such as the 416-8C ).

<. cheers

[airboss]

That's interesting Earl. Years ago, when this forum was located in the green I had a pair of 604-8Ks in wonderful shape. I'm still not happy I sold them. They financed part of a move. Anyway. At that time the published parameters for the driver indicated a really weird QTS for the 8K. It just didn't work. That's a mathmatical calculation.

Here's the thread from years ago where I figured out what was amis using high arithmatic. It's post 20.
http://www.hostboard.com/forums/alte...s-my-604s.html

Anyway, it's not a bad idea that the software checks the numbers. Boxplot (at that time I was using the freeware, now I have the registered) didn't

Dan

[airboss]

Hey! Earl, I went at it the other way around as you suggested and it spit out just what I wanted. Hallelujah. 3db down point at 40hz and 5db down at about 32. Now I have to get some idea of the volume of the 811 and 808 so that I can add that in. In my situation the horn has to live in the box. I'm gonna damp it with some sheet lead if I can find some local.

If you're willing to listen at 18 watts I think it stays flat to 30hz.

:thankU:

[bfish]

0.19 and 0.42 cu/ft for 811 and 511, respectively.

You'll find that M19s defy standard box theory and calculations a bit, as it's really a box with a resonant chamber separated by a (relatively) large port.

[airboss]

0.19 and 0.42 cu/ft for 811 and 511, respectively.

You'll find that M19s defy standard box theory and calculations a bit, as it's really a box with a resonant chamber separated by a (relatively) large port.

Hey thanks. Now I don't have to buy a big bag of vermiculite. I don't think the horn is going to make a lot of difference at those numbers anyway. Boxplot says add 10%-15% for bracing and dampening material anyway.

The program keeps making the port 3" round and I forget what depth. The box won't be the right shape but it will be the right volume....more or less. I'm gonna stick with the centers of the dirvers both horizontally and vertically and the drawing is pretty emphatic about port size and location too. We'll see. The first iteration will be plain MDF with a lacquer finish inside and out. As I go along I'll make it exactly as it shows.

Interesting point. At my local hardwood guy, MDF Red Oak both sides is $52 a sheet, Cherry is $82 a sheet and Walnut is $106. That's less than I thought. 7/16ths OSB is $16.00 a sheet! There's something wrong there.

[Earl K]

Hi Dan,

I'm glad you arm-twisted that program into complying with your wishes .

Do Altec woofers simply not play by Thiele-Small rules?

They do, but applying the T-S rules to Altecs' woofers does underscore their electromechanical design shortcomings ( from the perspective of maximum power handling vs output per BR alignment ) in the solidstate age .

<> cheers

[GM]

0.19 and 0.42 cu/ft for 811 and 511, respectively.

You'll find that M19s defy standard box theory and calculations a bit, as it's really a box with a resonant chamber separated by a (relatively) large port.

Yeah, the crudely expanding 'port' between the chambers introduces a phase inversion around its ~180 Hz upper mass corner as well as modestly 'pumps up' its vent gain, though considering how leaky the originals are, it may just offset vent losses. Personally, I'd rather have a well sealed cab and the entire area in the coupling chamber cut out to get a nice smooth response once the bottom side of the horn/driver is damped against spurious woofer reflections. This should make for a subjectively 'tighter'. more accurate bass line which some folks consider too 'dry' sounding though.

GM