New version of Martin King's MathCad Worksheets is coming soon!

[Henkjan]

and with 2 woofs (old sheet)

 

[Henkjan]

and 2 woofs new sheet

(why can't I find how to attach more than 1 pic to a message )

 

[MJK]

Henkjan,

I get the same type of results when I compare the old worksheets (dated 12/03) with the new ones. This is caused by a change in the damping correlation for very lightly stuffed pipes. A few years ago I found my original fiber damping correlation could be improved and that for an empty TL it was under predicting the response I was measuring. When you add stuffing the old and the new worksheets should be much closer.

Hope that helps,

 

[GM]

Greets!

I noticed that the infinite baffle midbass response changes between one and two drivers implying that 'Le' is unchanged rather than halved when two are wired in parallel. IOW they should be the same except offset by ~6 dB, which of course affects your TL's response.

GM

 

[Henkjan]

Henkjan,

I get the same type of results when I compare the old worksheets (dated 12/03) with the new ones. This is caused by a change in the damping correlation for very lightly stuffed pipes. A few years ago I found my original fiber damping correlation could be improved and that for an empty TL it was under predicting the response I was measuring. When you add stuffing the old and the new worksheets should be much closer.

Hope that helps,

OK, thanks

but how about the difference in the 1 and 2 woofs?

 

[MJK]

I think it is the same effect.

 

[Henkjan]

.....

another thing I noticed: when setting the parameters for 2 drivers in paralel (so: Sd double, Vas double, Re halved) the response changes quite a bit

I meant this, it's similar in both versions

 

[MJK]

You have lost me, I am not sure what the question is all about. Can you repost the two curves you are looking at, the driver parameters entered for each, and the enclosure parameters for each enclosure and then re ask the question?

 

[Henkjan]

what I did was 2 simulations, one with a single driver, one with two drivers. parameters adjusted as per your paper, cabinet made double cross-section. I expected the same output, but that was not the case. I will send you the mathcad file by mail when I get home

 

[Henkjan]

one woof

 

[Henkjan]

two woofs.

 

[MJK]

The plots look close to the same shape but with the two driver plot shifted up 6 dB as expected. There will always be slight differences due to the change in cross-section areas in particular the port area. I don't see anything indicating an error in your results, the two designs will never be identical in SPL response shape but they should be close.

 

[Henkjan]

OK, thanks

 

[Henkjan]

adding the graph of the TL profile was a briliant idea, the saying "a picture tells more than a thousand words" still holds true! helps a lot in checking the input and in optimising the design.

 

[MJK]

The graph of the TL cross-section has been a big improvement for me. It really helps eliminate silly mistakes when inputting the detailed data in TL Sections and helps visualize changes you make to the design.

 

[Scottmoose]

A Godsend in the BLH sheet too. Visual checks are always useful -especially when somewhare, amongst the mass of data, you've put a decimal in the wrong place. Before you were pulling your hair out trying to find where you'd messed up -far easier to isolate errors now.

 

[Tyimo]

Mathcad12 problem

Hi!

I have a problem with Mathcad 12.
When I try to open the "old" TL Sections workshets with Mathcad 12, there is nothing in the graphical windows! The program says:"An internal error has occurred" in the windows and there are a lot of error "line" under the sections numbers.
"This expressions redefines a previously defined variable"

Could somebody help me?
I could use this workshet with MathCad 8 explorer with out problems.

Greets:

Tyimo

 

[MJK]

For the worksheets to run in MathCad 12, you need to install all of the patches from the MathSoft website (www.mathsoft.com). The first vesion of MathCad 12 was dead out of the box and a huge screw up by MathSoft, they lost a lot of repeat customers. A perfect example of marketing people rushing a product to market before it was ready.

There is nothing wrong with the worksheets, the redefining of a previous expression underlining is a warning that can be turned off if it bothers you, that is what I did. This warning message will not stop the program from executing a worksheet.

 

[Scottmoose]

Ah. MathCad 12. Almost as big a mess-up as Windows 95 and Windows ME (98 was a little more stable), and that's saying something. Sad, because under all the bugs was a decent piece of software. I got sick of continually patching it up, so reverted back to Explorer. Got a copy of the latest edition coming in the new year though.

 

[Tyimo]

Thanks Martin!

I found only the Mathcad 12.1 Update. I donn't know is it enough for it to work.....

Greets:

Tyimo