HELP - Crossover Designing

[tcpip]

The data downloaded from Zaph Audio is evidently that of a real driver. Such readings may have mistakes or be inaccurate, but that's a matter of the skill and experience of the person taking the measurements. (John Krutke is one of the best, people like me are still making mistakes...)

But the data from your "captured data" screen is not of a real driver. I am sure there were some hookup or settings mistakes during measurements. It is not a case of the SPL curve being inaccurate -- it is a case of this not being a real SPL curve of a real driver at all. In other words, real data did not get captured at all, or it was processed incorrectly and you got invalid output. No real driver's SPL curve is that smooth. Ever.

I do not use ARTA, so I cannot even go beyond this point to suggest the cause. I have always used Speaker Workshop, and that has worked well. It had a steep learning curve, but they all have this challenge. I am sure you are facing the same challenge with ARTA right now. I got help from people on diyaudio.com for my initial Speaker Workshop experiments, and Claudio Negro's pages are a huge additional help. In comparison, hifivision has only a tiny sub-community which does serious DIY with measurements.

In fact, people tell me that SPL measurement using Speaker Workshop is easy -- most beginners apparently get into trouble measuring impedance, because a small amount of extra hardware is needed for that part. You should try using Speaker Workshop for your measurements, maybe?

Or else, go find an ARTA guru on the forums.

 

[keith_correa]

Check this. Seems clear enough for even me to understand.
BTW, what mic. are you using?

 

[jmascreen]

Check this. Seems clear enough for even me to understand.
BTW, what mic. are you using?

I have a very basic Intex Mic. Can you please suggest some good mic for measurements?
I have followed the instructions given here. ARTA Which for me looks similar to the link you suggested

 

[jmascreen]

tcpip - I will try with Speaker workshop, however on download my Antiviruses program detects it as threat. Did you get any behavior like that?

 

[tcpip]

I have a very basic Intex Mic. Can you please suggest some good mic for measurements?

Don't bother about the "which mic" question now. Currently, your measurements are not working at all -- it's not a question of inaccuracy. Once they work, you can progressively upgrade your mic to get more accurate measurements.

FWIW, I started my DIY measurements story with a two-dollar Panasonic mic capsule which Seigfried Linkwitz had said was very linear -- I bought the capsules from Digikey and made a wand out of a short length of aluminium pipe.

Recently I moved to a better mic from Parts Express, calibrated by Cross Spectrum Labs. This one costs me $75 and forced me to upgrade my mic interface hardware too (this one needs an XLR input). That was another $50.

I'm saying all this to assure you that your choice of mic can always be upgraded later -- just get the basic rig working now.

 

[tcpip]

tcpip - I will try with Speaker workshop, however on download my Antiviruses program detects it as threat. Did you get any behavior like that?

No, I did not get any such warning.

Speaker Workshop has become an open source product a few years ago. It should be easy to get a genuine, authoritative copy of the binary.

 

[tcpip]

I have followed the instructions given here. ARTA Which for me looks similar to the link you suggested

I have a very strange suggestion -- try it. I can see on your ARTA instructions page that they have asked you to connect the power amp line-out to your sound card's right-channel input, and the mic to your sound card's left-channel input. I suggest

• Try first by swapping these two connections. Put the power amp's line-out to the left-channel input and the mic to the sound card's right channel input. (Does your sound card have two channels of mic input, BTW? Mine doesn't.)
• Then, if you don't get a good real-looking reading, just disconnect the connection from the power-amp's line-out. Leave that input free. See what happens.

Try these and let us know.

Looking at the smooth, near-perfect, flat SPL curve you are getting, I am pretty certain that ARTA is measuring your power amp's line-out signal, not your mic signal. Use this as a hint, and start digging.

 

[jmascreen]

I have a very strange suggestion -- try it. I can see on your ARTA instructions page that they have asked you to connect the power amp line-out to your sound card's right-channel input, and the mic to your sound card's left-channel input. I suggest

• Try first by swapping these two connections. Put the power amp's line-out to the left-channel input and the mic to the sound card's right channel input. (Does your sound card have two channels of mic input, BTW? Mine doesn't.)
• Then, if you don't get a good real-looking reading, just disconnect the connection from the power-amp's line-out. Leave that input free. See what happens.

Try these and let us know.

Looking at the smooth, near-perfect, flat SPL curve you are getting, I am pretty certain that ARTA is measuring your power amp's line-out signal, not your mic signal. Use this as a hint, and start digging.

I will try it but I dont have separate ports as suggested by ARTA. I am using my laptop for this purpose.

 

[tcpip]

I will try it but I dont have separate ports as suggested by ARTA. I am using my laptop for this purpose.

I don't understand. Whether you have a separate sound card or built-in ports, you need at least a separate line-in for the power-amp's line-out connection, and a separate mic-in for the mic's signal. Do you have these on your laptop or don't you?

If your laptop is like mine, then it will just have a headphone out (which can be treated as a stereo line-out) and a mic in (a mono mic-in). IN that case, you MUST NOT try to connect the power-amp's line-out signal back to your laptop.

 

[jmascreen]

I don't understand. Whether you have a separate sound card or built-in ports, you need at least a separate line-in for the power-amp's line-out connection, and a separate mic-in for the mic's signal. Do you have these on your laptop or don't you?

If your laptop is like mine, then it will just have a headphone out (which can be treated as a stereo line-out) and a mic in (a mono mic-in). IN that case, you MUST NOT try to connect the power-amp's line-out signal back to your laptop.

No I dont have a seperate line IN in my laptop it has one Headphone, 1 Spdif and one Mic.

So do you think without the Power-amp input it will work?

 

[tcpip]

No I dont have a seperate line IN in my laptop it has one Headphone, 1 Spdif and one Mic.

So do you think without the Power-amp input it will work?

I can't say about ARTA, but with Speaker Workshop, it will definitely work. Speaker Workshop needs one channel of line-out (you have two, in the headphone outputs), and one mic in for the measurements. This is the mandatory part. It can also take a loop-back from the power-amp, but that's optional.

I am now curious -- if you didn't have a line-in, how were you connecting the power-amp line-out signal to your laptop?

 

[jmascreen]

I can't say about ARTA, but with Speaker Workshop, it will definitely work. Speaker Workshop needs one channel of line-out (you have two, in the headphone outputs), and one mic in for the measurements. This is the mandatory part. It can also take a loop-back from the power-amp, but that's optional.

I am now curious -- if you didn't have a line-in, how were you connecting the power-amp line-out signal to your laptop?

I had bypassed that part, as I understood that all data's were supposed to be captured via MIC. Let me know if I am wrong.
Also do the drivers need any components while testing or a direct connection from AMP. I went with the direct path

 

[jmascreen]

I have just made the enclosure smaller by a feet in height. Here is the updated enclosure diagram.

Please let me know if this worth a try, trying to start working on it from tomorrow EOD and measuring the drivers on Saturday.
Please Note - This diagram i had taken from tech forum of parts express, since its having same drivers and my targeted enclosure (TQWT)

 

[kapvin]

that response you posted, the alignment is not just fine, it's really good. I am curious as to where you got the worksheets, because now subscription is closed is closed.

if you are using the sheets, i would only look at two other things, now - 1. the woofer excursion, 2. the vent velocity. my sense is you will run out of excursion really soon (at about 10w below 40hz). I do not think vent air velocity will be a problem but you should just make sure that everything checks out.


happy building

 

[jmascreen]

that response you posted, the alignment is not just fine, it's really good. I am curious as to where you got the worksheets, because now subscription is closed is closed.

if you are using the sheets, i would only look at two other things, now - 1. the woofer excursion, 2. the vent velocity. my sense is you will run out of excursion really soon (at about 10w below 40hz). I do not think vent air velocity will be a problem but you should just make sure that everything checks out.


happy building

I dont have that sheets, I am a sample one provided by MJK. As stated earlier this I have taken from PE Tech Forum

 

[jmascreen]

Kapil, do i need to stick bitumen sheet, foam for damping entire inside and add the acoustic damping as shown in fig?

 

[keith_correa]

Kapil, do i need to stick bitumen sheet, foam for damping entire inside and add the acoustic damping as shown in fig?

Am not Kapil, but I'll chime in anyways The answer IMO, is: No, you don't need it. Just add the stuffing correctly and you should be golden. Peter S. and others say it in that post and I will second that - experiment with the port length between 5" - 7". A couple of side by side braces towards the open end will not hurt either. I think you will be very pleased with what you hear. :licklips:

 

[jmascreen]

As expected the Carpenter ditched me.... now need to run from pillar to post for finding a new one who can make the enclosures.. seems going to waste my long weekend

 

[keith_correa]

As expected the Carpenter ditched me.... now need to run from pillar to post for finding a new one who can make the enclosures.. seems going to waste my long weekend

As is usual, when you most need them, that's when they decide that a trip to their "gaon" is in order.

 

[jmascreen]

Is the drivers sitting on top of each other or just touching it from top?