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Small 2-way speakers with linear on-axis and power response characteristics (Scan Speak and SB Acoustics drivers). H&V off-axis measurements included
- Thread starter XMechanik
- Start date
- Thread Starter
- #202
Great job! I'm glad that you liked the design.
You may also try to experiment with closer wall placement or even putting them on a shelf.
I have them placed a few cm from the side walls and about 1 m from the back wall, turned towards the listening place. It was determined more by the room topology than a sound optimum but it works quite well.
Did you have a chance do take any measurements? Even simple impedance sweep can be very useful. If by chance any connection in the crossover is misplaced or missing it creates evident change in the impedance graph.
You may also try to experiment with closer wall placement or even putting them on a shelf.
I have them placed a few cm from the side walls and about 1 m from the back wall, turned towards the listening place. It was determined more by the room topology than a sound optimum but it works quite well.
Did you have a chance do take any measurements? Even simple impedance sweep can be very useful. If by chance any connection in the crossover is misplaced or missing it creates evident change in the impedance graph.
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I'm thinking of using this approach to avoid buying something that I'll only use once: https://audiojudgement.com/loudspeaker-impedance-measurement/
Any advice or comments?
Build it, it is EASY. Here are step-by-step instructions (maybe annoyingly long) on building a jig and measuring impedance in REW.
How good is your multimeter? Audio Judgement uses a $350 Fluke and gets a marginal result compared to the manufacturer spec. For $125, you can buy a DATS from Parts Express.
If you are skilled, you can build a test box, but you need a good soundcard or audio interface. If you have one around, may be cheaper to use with DIY test box, otherwise DATS is a better choice.
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I appreciate the responses, but your objectives seem different from mine. You both seem heavily involved in DIY speakers; I expect the two Mechano23's to be the only speakers I will ever build.
So, to clarify: My only purpose in measuring impedance is to confirm that I have wired two Mechano23 crossovers properly. My cost in using Audio Judgement's approach is about $6.
The DATS is $125, the audio interfaces I could easily find were that or more.
Will the simple and cheap Audio Judgement approach confirm my wiring?
So, to clarify: My only purpose in measuring impedance is to confirm that I have wired two Mechano23 crossovers properly. My cost in using Audio Judgement's approach is about $6.
The DATS is $125, the audio interfaces I could easily find were that or more.
Will the simple and cheap Audio Judgement approach confirm my wiring?
It might be good enough, but why I asked about your multimeter. Many are not very good for accurate AC measurements at higher frequencies. Soundcards can have comparable issues and is why REW has you load a calibration profile. If you can set up and follow the REW instructions with the recommended load, would not bother with the spreadsheet, REW will create a nice chart for you. This is all discussed in the REW documentation.
If you get a comparable impedance curve, the crossover likely fine. Peaks and valleys at specific frequencies are more important than impedance magnitude accuracy.
Thank you. As my multimeter cost ~$10 a decade ago I'm confident it's not good enough. I'll read more on REW's measurements, but I expect that I'll revert to visual inspections. After all, it's a simple circuit and I'll lay it out the same way. What could go wrong?
Honestly it seems like false economy to me.
I measured my speakers 4 times during construction - one reading free-air per crossover and one reading per finished cabinet. If we take the author's estimate of 30 minutes per impedance sweep as accurate, and not optimistic, that's 2 hours of work, assuming no mistakes or re-work. I value my time at more than $65/hour (Dats v3 cost = $130/2), plus I know the resulting data is almost surely good.
Despite what we may want to tell ourselves, DIY speakers are not about saving money. We can't compete with China on price, certainly not on the low end. Do it right and take satisfaction in the process.
Here are mine. Totally stock build, no deviations from the original recipe.
Here are the DATS sweeps, since we are talking about that, and this site loves graphs.
Free-air sweep (before cabinets put together):
Impedance from XMechanik's original post:
Final impedance sweep of finished cabinet:
Squinting past the scaling differences and Y axis origin differences, they seem right to me. (I'm only posting one image per type here, both cabinets/crossovers measured the same.)
Here are the DATS sweeps, since we are talking about that, and this site loves graphs.
Free-air sweep (before cabinets put together):
Impedance from XMechanik's original post:
Final impedance sweep of finished cabinet:
Squinting past the scaling differences and Y axis origin differences, they seem right to me. (I'm only posting one image per type here, both cabinets/crossovers measured the same.)
- Thread Starter
- #211
Looks great! (both the impedance measurement and the enclosures). Or maybe try to release the LogZ button, then the Y scale should become linear and the comparison to the VituixCad chart will be slightly more readable?
Download a phone app (RTA?) and measure the speaker at 1m or 2m with the xo installed. If the xo is wrong it will probably be clear in the measurement.
Excellent speaker!! And a very easy DIY build. Thanks.
@XMechanik You have any ideas about designing more speakers? Or maybe you already have other designs. Clearly you know what you are doing!
@XMechanik You have any ideas about designing more speakers? Or maybe you already have other designs. Clearly you know what you are doing!
somebodyelse
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Am I hearing that right, 30 minutes per sweep?
I was referring to the time estimate given by the author of the manual multimeter technique referenced above. The DATS box I used takes maybe 2-6 seconds total to do an impedance sweep.
Oops, I missed that. Thanks.
- Thread Starter
- #219
There was a concern (link) that Mechano23 crossover was tuned to the specific drivers copies and the results with other driver samples, especially coming from different production lots, might be significantly different.
I've built another Mechano23 pair, the drivers were purchased from the same source but 1.5 year later so they're possibly from different production lot.
Gated spl measurements (>300Hz) are very similar. The measurement curves are shifted for better readability, the lower pair is the original, the upper is new.
The impedance characteristics look different on the LF side (higher fs of new midwoofers?).
Good correlation overall but it's hard to call it a definitive conclusion.
BTW, the enclosures are bit different No change in external dimensions but panels and joints are modified.
I've built another Mechano23 pair, the drivers were purchased from the same source but 1.5 year later so they're possibly from different production lot.
Gated spl measurements (>300Hz) are very similar. The measurement curves are shifted for better readability, the lower pair is the original, the upper is new.
The impedance characteristics look different on the LF side (higher fs of new midwoofers?).
Good correlation overall but it's hard to call it a definitive conclusion.
BTW, the enclosures are bit different No change in external dimensions but panels and joints are modified.
