Help required with matching tweeters please

[The Grand Wazoo]

Morning blokes and other folks,
I'd like a little assistance please. As mentioned in my Genexxa speaker thread (http://theartofsound.net/forum/showthread.php?27501-Genexxa-Pro-LX5-Speakers-Tart-em-up-or-Chuck-em-out!), one of the Linaeum tweeters is noticeably down in output.

I've found another pair of speakers and I'd like to select from them, the most closely matched pair of tweeters as possible out of the 4 that I have. I have a good multimeter but apart from checking resistance, is there anything else I should be looking for? If so, how can I test for it?

http://imageshack.us/a/img849/4800/5a0t.jpg

[StanleyB]

[QUOTE=The Grand Wazoo;503109]

I've found another pair of speakers and I'd like to select from them, the most closely matched pair of tweeters as possible out of the 4 that I have. I have a good multimeter but apart from checking resistance, is there anything else I should be looking for? If so, how can I test for it?/QUOTE]
How good is your multi meter? If it can measure down to 0.01 Ohms then it would be a good enough method to select the best of the three.
If you got a smart phone then look for an app that can measure decibels. I have one installed on my Nokia phone. I have used it to measure sound levels and speaker positioning. You can use an app like that to measure the sound output from each driver at a specific point on the volume control of your amp. Then select the best matched pair.

[The Grand Wazoo]

OK, thanks for that Stan.
No, I don't have a smartphone - tools of the devil!

[Welder]

Hello Chris. :)

I think the most important thing is to match the drivers impedance at nominal first and throughout the curve.

If you don’t fancy all the faffing about just get a match at nominal and fit a Zobel network.
Anyway, here are some links to help give you some ideas.
I built a Wallin jig and I have some software that does the job but it ain’t easy.



http://www.raymondaudio.nl/files/jig.pdf

http://www.speakerworkshop.com/SW/Project/Equipment.htm

http://www.speakerworkshop.com/SW/Real%20Results.htm

http://www.artalabs.hr/requirements.htm

[The Grand Wazoo]

Hi stranger!
Hows things you ol' bugger?!
Thanks for this - looks like some reading is in order then. Sounds like it's going to start getting complex and technical for a simple lad from the woods.

[awkwardbydesign]

Can you simply power up a pair, preferably in parallel, place them far enough apart to get a central image, play test tones, or simple music, and listen to find a matched pair?
Then reverse them, or your head, and do it again? My ears are not matched, so this will even it out.
Then try them in series. If you have no test equipment, use your ears. The original test equipment.

[The Grand Wazoo]

Yes, it was the MkI lug'ole that spotted the dodgy unit!
That's how I'd planned to do it, but I wonder if testing might not be a useful approach here also.

[awkwardbydesign]

Yes, it was the MkI lug'ole that spotted the dodgy unit!
That's how I'd planned to do it, but I wonder if testing might not be a useful approach here also.
As long as you remember "also", not "instead of".

[Welder]

Hi stranger!
Hows things you ol' bugger?!
Thanks for this - looks like some reading is in order then. Sounds like it's going to start getting complex and technical for a simple lad from the woods.

Things are good thank you Chris. How about yourself?

Interesting project you’ve got going there. :)
Given it’s the high frequency units you’re dealing with I would probably try the zobel network option.
My approach in general is to match impedances to the bass driver. Hopefully this means with the right driver selection possibly just a zobel network on high and at worst midrange, leaving the bass free from the extra circuit in a three way driver system for example. It’s a pretty cheap tryout option and you can add the zobel network at the driver terminals instead of messing about with the crossover.

It does get complicated if the drive units are radically different throughout the impedance curve. Hopefully, if you buy good quality drivers this isn't a major issue but I've come accross a few where all the trimming of coils and adjust of gaps etc etc just wouldn't give a matched curve.
I don't know how much of a mismatch is needed to be audible and for your project I doubt if you want to get super fussy.

BTW, got any recommendations for an easy start twelve inch chainsaw?

[Reffc]

Morning blokes and other folks,
I'd like a little assistance please. As mentioned in my Genexxa speaker thread (http://theartofsound.net/forum/showthread.php?27501-Genexxa-Pro-LX5-Speakers-Tart-em-up-or-Chuck-em-out!), one of the Linaeum tweeters is noticeably down in output.

I've found another pair of speakers and I'd like to select from them, the most closely matched pair of tweeters as possible out of the 4 that I have. I have a good multimeter but apart from checking resistance, is there anything else I should be looking for? If so, how can I test for it?

http://imageshack.us/a/img849/4800/5a0t.jpg



Hi Chris

most definitely there is!

You may need some crossover changes too but you will need the following data:

DCR (Voicecoil DC resistance);
Resonant Frequency (Hz)
Le (inductance equivalent)
Impedance...Please note, do NOT rely on stated impedance as this is only ever a reference to the nearest of 4, 6 or 8 Ohms. Actual nominal impedance needs to be known. This requires specialist measurement kit really (which I have), or at the very least the manufacturer's impedance plot for the drive units.
Sensitivity. (dB for 2.83V input)

With these, you can determine exact crossover values.

If unsure, send them to me and I can measure all of these things for you and advise on crossover changes.

These things cannot be guessed as it's simply working in the dark without actual measurements.

Regards

Paul

[The Grand Wazoo]

I may have not explained the task at hand properly, so I'll try to be clearer here:


I have a pair of speakers from which I replaced the crossover components, like for like.
One of the tweeters has a reduced output, for whatever reason.
I have acquired an identical pair of speakers and so I now have three good tweeter units.


I want to find the two tweeters that are matched most closely to each other.

[Reffc]

In principle, you can just swap them over Chris, but for thoroughness, I was merely suggesting checking actual driver measurements as it can often save some tinker time with crossovers. Try them and see. If they sound good and are the same tweeters, then nothing else should need doing. If for any reason they don't, by having the drivers measured and the crossovers examined then a solution would be straightforward.

[The Grand Wazoo]

OK yes thanks Paul, a simple straight swap is actually what I've done now, but I just wondered whether having a third good one, it might be worth comparing them to see which were the closest pair in all parameters.
However, they sound good and to be honest, at the moment, I can't be arsed! If it is easy enough to test them with a multimeter, this might be something I do at some future time.

Thanks to all for your contributions.
The main thread will be updated shortly.

[Welder]

There isn’t an easy accurate way of doing this Chris. To get this stuff right you need a computer program and impedance jig of some sort. :eyebrows::doh:

You can measure the resistance of each drive unit (+ probe to + on driver terminal etc) but obviously, this gives you a DC based measurement and what the driver sees from the amp is AC.
However, you should be able to get best a match at nominal. Very roughly, a drivers impedance will in fact be a couple of ohms less than the DC resistance reading.

Having picked the best pair from your resistance measurement you can match them using this L pad circuit (bottom of the page)

http://ccs.exl.info/calc_cr.html#lpad

Assuming there isn't something else wrong with the drivers they should output approximately the same. :eyebrows:
Hope this helps.

Further reading if you’re interested……

http://sound.westhost.com/tsp.htm

[The Grand Wazoo]

Thanks John.

[Reffc]

John's right...DC measurement only gives you comparative DCR for the voicecoils between drivers. If you change your mind and want them properly tested in the future for any reason, I have one of the "test jigs" and the requisite associated computer programs that John's referring to and can do full frequency signal sweeps and obtain all the Thiele Small parameters plus actual impedance curves (so nominal impedance can be accurately established as well as resonance peaks).

[The Grand Wazoo]

Excellent!
Thanks so much for the kind offer.