Lspcad issue

[ramiro77]

Hi everyone.
I´m trying to design a passive crossover.
I´ve done all measurements. But when I put those measurements in Lspcad, the program interprets wrongly the txt files.
I was watching the example files. I saw that the txt files have a different format inside. I mean that the info is written in other way.

Which program do you use to measure impedance and phase? I was using ARTA, but i don´t know how to make properly those txt files.

I didn´t have any issues with frequency response. I´m using justMLS.

Regards.
Ramiro.

[winslow]

I took the data from SPLtrace, copied it to clipboard, and saved it as a .txt file. And then I used the .txt files for FR and imp. That worked fine for me.

[ramiro77]

Awesome winslow!
I did some succesfuly tests!
Thank you so much.

The only thing that I missing is to measure phase. I´ve been measuring it with Limp. How can I export that measurement to the TXT file? And where should I put that TXT? In the frequency response or in the impedance response?

[JMB]

If you are measuring with ARTA, make certain that you eliminate all of the words at the top of the page and that you are starting with your lowest frequency measurement. You can look at your files by opening in Notepad. You can save them as frd files if you wish by saving as all files (not .txt) and then naming the file with Yourname.frd. IIRC, ARTA does not measure the phase but I suspect that LSPCAD calculates it. I am pretty certain that LSPCAD can read frd files. I have not worked with LSPCAD but having experience with Soundeasy, this worked for me with SE and ARTA measurements. You cannot measure phase with LIMP for frequency, it measures Impedance, a whole nother animal.

[ramiro77]

Thanks for you response JMB!
I´m pretty sure that ARTA (limp) can measure electrical phase. Look at the graphic at the end of this post.
I´m not sure if lspcad can read FRD and ZMA files, but i´ll try it.

Regards!

[JMB]

LIMP is registering the electrical phase of the Impedance. I may have misunderstood you, but I was thinking that you were using that for your SpL measurements. The phase of the SpL measurements would be a completely separate issue; the software generally calculates this and then you can do a Hilbert Bode to find Minimum Phase if you wish. The benefit to minimum phase for the SpL is that by using this along with the relative acoustic offset, you can model off axis. Personally, however, I prefer to model based upon on and off axis measurements. Jay

[ramiro77]

I don´t mind about off axis response.
But I thought that electrical phase was the same thing that the phase who appears in the spl txt.

What is the difference between both? Because i´m using electrical phase in the impedance txt, but i have no thing for phase in the spl txt.

By other way, I recently did some measurements and I´ve put them in lspcad as you said, and everything is fine now. The software is getting the txt files in the right way.

[JMB]

The phase for the Impedance and the Phase for the SpL are completely different things. You cannot substitute one for the other. You need SpL phase to model crossovers while Impedance phase is helpful in identifying the point of resonance. Jay

[ramiro77]

Ok, I understand you.
Can I measure SPL phase with justMLS? Or it´s not enough?

[JMB]

Yes, I believe that the phase is produced through MLS though I am not certain if it is measured or calculated. If you use the phase from it and you do not then calculate the minimum phase, you will only be able to design for the position from which you take the measurements. If you use Minimum Phase and know the relative acoustic offset, you can use the software to predict the response off axis. To calculate relative acoustic offset, the easiest way that I know of is to take 3 measurements from one point: the tweeter, the woofer, and the two connected in parallel. Then using Jeff Bagby's Passive Crossover Design Software (freeware that uses Microsoft Excel Interface), you enter the relative offsets on the baffle for the woofer height and offset relative to the tweeter and then load your woofer and tweeter measurements (you will have to do the Notepad thing to convert the files to .frd files as I described above). Then load the measurement that you took with the two in parallel as a target. By adjusting the z offset value you will be able to re-create the summed measurement of the two drivers. This will give you your relative acoustic offset.

Of course, if LSPCad has the ability to do this, it may do it without going through this procedure. Though it sounds complicated, you will be surprised how quickly you will be able to do it once you try it. Jeff's program is pretty intuitive but I and many others can help you if you have problems with it.

I am not an LSPCad user (Soundeasy and sometimes ARTA for measurements; Jeff's PCD and Soundeasy for design) so I apologize regarding my ignorance regarding that program.

Jay