Help needed! Tweeters have little output on Classix II build

A

ajbologna

New Member
Hi everyone, long post incoming because I want to provide as much information as possible.
TLDR: Tweeters aren't tweeting and I'm out of troubleshooting ideas/in over my head.

This is my first speaker build and I’m making a pair of Paul Carmody’s Classix II speakers. After soldering the crossover and attaching the drivers I gave it a test and noticed that almost no sound is coming out of the 1” tweeters. With everything fully assembled in the box the 6.5” drivers produce some sound but the 1” tweeters can only be heard very faintly if I disconnect the 6.5” drivers. The problem is identical with both speaker boxes. No components were substituted from the original design and all parts were sourced from Parts Express.

I ran both drivers in reverse with no real change in sound output. I am confident that the crossover was built correctly as I have electronics experience and triple checked all of the connections. Inductors are positioned to prevent inductive coupling. I checked that the drivers themselves work, tested directly from the amp output at a low level. Sound levels run directly off the amp are comparable between the 1” and 6.5” drivers at the same level amp output. I then used my 6.5” driver to probe the tweeter half of the crossover and noticed that while the output is high right at the amp input (jumping over the whole tweeter crossover), the sound output decreases sharply after each additional stage of the crossover. Basically the the sound gets quieter and quieter after each of the two capacitors.

On some level this makes sense as the crossover is doing its job of filtering out the lower frequencies, but is such a drastic reduction in sound normal? The tweeter getting the high frequencies doesn’t matter much if it doesn’t get enough power to actually play them. Is the problem in my crossover? The only thing I can think of is that the capacitor polarity is wrong but the capacitors should be non polar. Is this reduction in volume across the caps in the tweeter side of the crossover normal? Any trouble shooting tips or ideas would be very much welcome.

Thanks in advance!
 
i know nothing about crossover design but keen to learn .. i see "-" is not common in this design .
Classix%20II%20XO.jpg
 
No image Pete.. hey mate..anyway!!
bink

Asking for drivers and schema.. wonder if he put in piezo's for the tweets.. they don't need caps in the xovers but I don't do much xover work anymore. Wonder about the input amp, too. maybe not enough power amp output power?
 
Are R1 and R2 the correct value?

Are you able to confirm C1 and C2's value? Try measuring these on a capacitor tester?
 
Two mates on each side of the world!! :beerchug:
Link worked, Pete.
OP can swap leads of the tweeter only and leave the +/- leads to woofer be. Another test is take the tweet cap (say 4uf? non polar) and connect to the woofer. This would be Pos woofer terminal to tweeter neg. If tweet has no +/- marking then swap tweeter leads. I did this with dayton tweets before to get correct polarity.
hope it helps...
bink
 
If this is your first build, then you might simply be unaccustomed to how little the tweeters normally contribute to total acoustic output, especially when the crossover frequency is positioned well above the midrange, and especially if your hearing is even slightly impaired.
 
Wow, thanks for all of the help! First, here is a link to pics of my crossover and the plans. I only have a cheap multimeter so I have not measured the resistance, capacitance, or impedance of any of the components. I played with swapping the tweeter leads and it seemed slightly worse when i switched them.

This might all be solved by BinaryMike's post though because I do have mild bordering on moderate hearing loss above 2000Hz. I hadn't even considered the problem was my ears and had to check my old results to see which frequency I lost. Does this seem likely? And as a followup, is it a crazy idea to brighten up the tweeter to compensate for my hearing loss? I could replace R1 with a lower value resistor so the tweeter gets more current possibly.
 
R1 and R2 work together to do several things including impedance compensation of the tweeter. So if you tweak R1 you would also need to tweak R2.

I would do some reading on "L pads" as that will make things clear.

However only tweaking those two resistors to take into effect the L-pad aspects of these 2 resistors may be a mistake and may affect other parts of the tweeter circuit in other ways. Others may know more on this.
 
I'd say the "problem" is at the L-pad. I don't know who or how the l-pad was calculated. I'd remove it from the crossover and start adding a new L-pad reducing a few dB at a time until finding the right balance. Also, 2 small caps in series cut the high freqs a lot, so what BinaryMike says it's true. Judge the sound of the complete system, forget how loud each driver sounds. The freq response graphs of the original design look very nice, so perhaps that's the way it should be.
 
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Do you know that the crossover point is for this system?

It could well be that a wide range of sound frequencies are being sent to the woofer-mid unit, with only a small amount being sent to the tweeter. Some systems are set up like that, and some send a bigger range of sound to the tweeter.
 
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Well I copied and pasted it and now I can see it. :D

Can you post pics of one of the crossovers so we can see how it's put together?

Just curious, did you get all the crossover components by ordering a kit or did you select them individually?

Classix%20II%20XO.jpg
 
I would agree the tweeter is coming in fairly high here so it is not going to put out a lot of apparent volume playing by itself.

Also the 4th order crossover is in fact going to eat up some amp power. The article doesn't give an overall db sensitivity for the whole speaker but looking at this crossover, you would expect to see lower output after all those stages so that's not unexpected.

I would not think that 'mild to moderate' hearing loss is THAT bad. It is, as someone said, all about the total sound of the speaker.

I wonder if an 8-ohm adjustable L-pad would work here? OP could turn it up till it sounds good.
 
I've had my hearing tested and and anyone concerned about their hearing.. Please don't trust your sound card and headphones for a test. You can have gaps from one hz to another.. I have a gap in one ear at about 19khz. then I can hear up to 22khz. if I'm listening to like lots of cymbals.. or good hi-hat? or range of high range bird songs. Some are beyond human hearing range.

Ya know? doesn't take much for a young person to experience very loud ear shock and take a while to restore itself. ringing etc. Barametric pressure changes numbs my ears off, too.
 
L-pads made for some interesting reading slimecity. I believe that is the problem! I think that I'm going to follow the route that elnaldo and toxcrusadr recommended and replace the two resistors of the tweeter half of the crossover with an 8-ohm 50W Lpad and tune it until the whole system sounds best to me. The crossover was not designed with an l-pad in mind but the amp sees 8 ohms of impedance currently so an 8 ohm l-pad shouldn't change anything unless my understanding of l-pads is flawed.

As to other questions, the crossover point is just above 2000Hz as seen on THIS GRAPH on the designer's website. I've checked my wiring a couple of times but would welcome another set of eyes Grenadeslio. I put a link to the images in my last post but again, CLICK HERE to see it. I bought all the components individually from parts express and I've since triple checked that what I have matches the plans.
 
I had my hearing tested by an audiologist about two years ago and here are the results for anyone interested. I also work in a loud wood shop and while I'm very good about wearing hearing protection, I'm sure it hasn't improved in the mean time.

upload_2018-11-2_18-45-54.png
 
I'd remove the L-pad. Perhaps your hearing balances things. If that graph is accurate, you hear almost -20dB from 500Hz, at 2kHz.

You can always tame a couple of dB later with some resistors (if needed)
 
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