Gents,
I originally placed this in an old thread but it might be get lost in the mud so I've started a new one...
I built a pair of Jaycar JC-50 speakers and I have a problem so here's hoping that someone responds. The JC-50's were described in Electronics Australia December 1998 - yeah I know that's a long time ago but it's worth a try. I'm a retired techo and have built several amps over the years but this was my first pair of speakers. I purchased them as a Jaycar kit in 1999 and was sort of happy with them mainly because I'd spent the money so they had to be good - I didn't want to dent my pride. After a while I decided that they were rubbish. Very poor base and sounding fairly thin but of course I didn't want to admit it. Then I discovered that my Pioneer amp had a "Loudness" control. Wow - What a difference! Good punchy base and quite acceptable. But they are meant to sound good when driven with a flat response amp but they didn't. My only explanation was that the loudness control compensated in a rather rough way for the bad response of the speakers. Both speakers by the way, perform the same.
Just recently, I built the Silicon Chip/Altronics Ultra Low distortion amp. This is a straight thru amp with no loudness or tone controls. And yes the speakers were rubbish. So I decided it was time to upgrade. So I ended up with a pair of Paradigm Monitor 11 speakers (good price from Eastman Hi-Fi I might add). I tried them with both amps and yes, the JC-50's are crap. So what to do?
Well, I wasn't going to throw them out! So I've decided to investigate further..
Firstly, am I the only one who's experienced this?
I've removed the woofer in one box and got to the x-over board out. I was hoping to find the obvious like a capacitor that's wrong or maybe even an error in the board layout. At this stage, I can only accept that the inductor values are correct. Everything looked okay. But then I had a closer look at the original article in "Electronics Australia" December 1998 edition. It gave the values for the components in the x-over. Again, I'm no speaker design engineer so can only go on what the original designer came up with and he would know a lot more about speaker design than me. But a closer look at the article said that the low pass was at 600Hz and the high pass was at 5kHz. Looking further, I found in a Jaycar catalog info on how to design x-overs. Okay, I know that x-over design requires a lot more than a few formula to come up with the L and C values (and their formulae don't quite gell with the L & C charts they've added) but from that info, I just can't see how the JC-50 designers came up with the capacitor and inductor values they have in the design. There appear to be big gaps in the designed x-over points which are meant to be 600Hz (too low?) and 5kHz. For instance, if the formula is used it looks like the L.P. for the woofer is at around the 300Hz mark and the Midrange is all over the shop as well with the 12db/octave points at around 430Hz & 1200Hz, whereas it should be closer to 600 Hz & 5KHz. If my calcs are wrong I'll accept the flak but the bottom line is, they sound awful so something has gone astray somewhere.
I'll be doing some further testing now and see if I can improve the x-over. I'll tackle the base driver first because it only has one inductor and one capacitor involved. The mid and high drivers are a little more involved.
I'm really keen to hear any comments. I recon these speakers will be okay if I can solve this dilemma.
Regards
Talbit
I originally placed this in an old thread but it might be get lost in the mud so I've started a new one...
I built a pair of Jaycar JC-50 speakers and I have a problem so here's hoping that someone responds. The JC-50's were described in Electronics Australia December 1998 - yeah I know that's a long time ago but it's worth a try. I'm a retired techo and have built several amps over the years but this was my first pair of speakers. I purchased them as a Jaycar kit in 1999 and was sort of happy with them mainly because I'd spent the money so they had to be good - I didn't want to dent my pride. After a while I decided that they were rubbish. Very poor base and sounding fairly thin but of course I didn't want to admit it. Then I discovered that my Pioneer amp had a "Loudness" control. Wow - What a difference! Good punchy base and quite acceptable. But they are meant to sound good when driven with a flat response amp but they didn't. My only explanation was that the loudness control compensated in a rather rough way for the bad response of the speakers. Both speakers by the way, perform the same.
Just recently, I built the Silicon Chip/Altronics Ultra Low distortion amp. This is a straight thru amp with no loudness or tone controls. And yes the speakers were rubbish. So I decided it was time to upgrade. So I ended up with a pair of Paradigm Monitor 11 speakers (good price from Eastman Hi-Fi I might add). I tried them with both amps and yes, the JC-50's are crap. So what to do?
Well, I wasn't going to throw them out! So I've decided to investigate further..
Firstly, am I the only one who's experienced this?
I've removed the woofer in one box and got to the x-over board out. I was hoping to find the obvious like a capacitor that's wrong or maybe even an error in the board layout. At this stage, I can only accept that the inductor values are correct. Everything looked okay. But then I had a closer look at the original article in "Electronics Australia" December 1998 edition. It gave the values for the components in the x-over. Again, I'm no speaker design engineer so can only go on what the original designer came up with and he would know a lot more about speaker design than me. But a closer look at the article said that the low pass was at 600Hz and the high pass was at 5kHz. Looking further, I found in a Jaycar catalog info on how to design x-overs. Okay, I know that x-over design requires a lot more than a few formula to come up with the L and C values (and their formulae don't quite gell with the L & C charts they've added) but from that info, I just can't see how the JC-50 designers came up with the capacitor and inductor values they have in the design. There appear to be big gaps in the designed x-over points which are meant to be 600Hz (too low?) and 5kHz. For instance, if the formula is used it looks like the L.P. for the woofer is at around the 300Hz mark and the Midrange is all over the shop as well with the 12db/octave points at around 430Hz & 1200Hz, whereas it should be closer to 600 Hz & 5KHz. If my calcs are wrong I'll accept the flak but the bottom line is, they sound awful so something has gone astray somewhere.
I'll be doing some further testing now and see if I can improve the x-over. I'll tackle the base driver first because it only has one inductor and one capacitor involved. The mid and high drivers are a little more involved.
I'm really keen to hear any comments. I recon these speakers will be okay if I can solve this dilemma.
Regards
Talbit
Posting the crossover schematic would be useful, pics of loudspeakers and individual drivers also.
A tip is to take a listen to one driver only (disconnect the other two) on a range of music, and identify where nasties are.
Then try two drivers (mid+bass, mid+tweeter) and take a listen to how they combine.
Dan.
A tip is to take a listen to one driver only (disconnect the other two) on a range of music, and identify where nasties are.
Then try two drivers (mid+bass, mid+tweeter) and take a listen to how they combine.
Dan.
Gents,
I could download the driver info by posting the pdf images from the Jaycar 1999 catalogue. Can someone let me know if it's okay to post these on the forum. If not, I'll type out the important parameters and post those. The woofer is the Response CW-2137, the midrange is the Response CM-2092 and the tweeter is the VIFA D19 CT-2019. It looks like Jaycar have discontinued these particular speakers and have replaced them with cheaper varieties. I lost my original copy of the article in "Electronics Australia" magazine so I downloaded a pdf from Silicon Chip. But I had to pay for it so I'd better not include it here. So I'll knock up my own schematic of the x-over now and post it when done.
Regards
Talbit
I could download the driver info by posting the pdf images from the Jaycar 1999 catalogue. Can someone let me know if it's okay to post these on the forum. If not, I'll type out the important parameters and post those. The woofer is the Response CW-2137, the midrange is the Response CM-2092 and the tweeter is the VIFA D19 CT-2019. It looks like Jaycar have discontinued these particular speakers and have replaced them with cheaper varieties. I lost my original copy of the article in "Electronics Australia" magazine so I downloaded a pdf from Silicon Chip. But I had to pay for it so I'd better not include it here. So I'll knock up my own schematic of the x-over now and post it when done.
Regards
Talbit
Why do you say the JC50 are bad? If you can critique them we may be able to point you in the right direction. Overly bright? Not enough bass? Muddied midrange?
I have to say tho that I have never liked the D-19 and lots of people myself included have trouble with that particular dome midrange driver.
I think the trick to using it is to cross as close to it's resonant frequency as practical and cross to a bigger tweeter much lower
The orientation of the coils on the XO is all wrong tho
I have to say tho that I have never liked the D-19 and lots of people myself included have trouble with that particular dome midrange driver.
I think the trick to using it is to cross as close to it's resonant frequency as practical and cross to a bigger tweeter much lower
The orientation of the coils on the XO is all wrong tho
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Thanks,
All I can say is a repeat of my first post... "Very poor base and sounding fairly thin" but definitely not right. And not just borderline. Definitely not right.
I recon the coils are in the right place - just the wrong L & C values. Standard low-pass for the woofer (L1 & C1) then mid-range band-pass made up of C5 & L6 plus L2 & C2 then the high-pass C7 and L5 for the tweeter. The x-overs are meant to be at 600Hz and 5kHz. The extra odd components are there to try and keep the impedance fairly level across the frequency range. The article explains it all and it makes sense.
I'll ask my wife to go out tomorrow while I do some tests.
I've extracted the x-over board and run the cables to the drivers thru one of the ports. That way I should be able to play around with the component values.
I really can't send a copy of the original article because of copyright.
I'm going to try and contact the original designer Phil Routley. According to the original article, he used to work for Occasion Audio but I can't find any reference to them. I can't imagine Jaycar would be of any assistance after all these years.
Talbit
All I can say is a repeat of my first post... "Very poor base and sounding fairly thin" but definitely not right. And not just borderline. Definitely not right.
I recon the coils are in the right place - just the wrong L & C values. Standard low-pass for the woofer (L1 & C1) then mid-range band-pass made up of C5 & L6 plus L2 & C2 then the high-pass C7 and L5 for the tweeter. The x-overs are meant to be at 600Hz and 5kHz. The extra odd components are there to try and keep the impedance fairly level across the frequency range. The article explains it all and it makes sense.
I'll ask my wife to go out tomorrow while I do some tests.
I've extracted the x-over board and run the cables to the drivers thru one of the ports. That way I should be able to play around with the component values.
I really can't send a copy of the original article because of copyright.
I'm going to try and contact the original designer Phil Routley. According to the original article, he used to work for Occasion Audio but I can't find any reference to them. I can't imagine Jaycar would be of any assistance after all these years.
Talbit
Read this first
Placement of coils in crossover networks
Have you checked stereo phase??
L& C values look reasonable to me and posting the link to the original article or a copy is usually OK so long as you give provenance
Also make sure that the outputs to the drivers are not reversed.
Placement of coils in crossover networks
Have you checked stereo phase??
L& C values look reasonable to me and posting the link to the original article or a copy is usually OK so long as you give provenance
Also make sure that the outputs to the drivers are not reversed.
Thanks for going to the effort of the pdf.
Yes, please describe your sonic/subjective ills.
There is quite a lot that can be done to significantly improve your existing crossover at relatively little cost.
IIRC those Jaycar dome midranges are all wrong somehow....IIRC gently rubbing a finger tip across the dome excites some fearsome nasties.
Dome mids are generally regarded as bad, but coating/doping treatments can help.
This is looking like a group DIY effort.
Dan.
Yes, check phasing of L/M/H drivers.....like I said try pairs of L/M/H drivers individually to confirm correct driver polarities......mission critical !.
Also, IME ferrite cored inductors sound all wrong....thin, lumpy, annoying.
You might like to try subbing out those ferrite cored inductor with air-cored ones.
Correct bass is everything....get the bass sounding right, and then you can tune the rest correctly....otherwise you have no hope.
Those BP/NP electros need bypassing also.
Dan.
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Yes the phase of the drivers is correct at least presuming the markings on the posts are correct.
What I need is to find someone who has a set of these and see what they think. Someone here in Canberra would have them but unless he spots this post, I'll never find out.
I'll do some tests tomorrow. I'm also doing a lot of reading re x-overs so will be able to come up with some more calculations. My cals so far tell me that the values are wrong. But then I can't imagine Jaycar selling lots of these without someone picking up on it. But then I've only started to listen critically using a flat amp after all these years.
Talbit
What I need is to find someone who has a set of these and see what they think. Someone here in Canberra would have them but unless he spots this post, I'll never find out.
I'll do some tests tomorrow. I'm also doing a lot of reading re x-overs so will be able to come up with some more calculations. My cals so far tell me that the values are wrong. But then I can't imagine Jaycar selling lots of these without someone picking up on it. But then I've only started to listen critically using a flat amp after all these years.
Talbit
Sure, but subjective confirmation is required....you do know what phase reversed drivers sound like don't you ?.
I saw an old advert for these for $20.00....maybe they really are that bad, LOL.
It could well be, that somebody got it all wrong.
With the right tweaking, the group here might help you, but I do fear that that dome midrange might be a big part of the problem.
We can all play along and help, maybe we can polish a turd.
Dan.
I know what out of phase sounds like. I'll double check the phasing tomorrow but I'd bet my last dollar it's not phasing. I can check the woofers with a 1.5V battery but not sure if I'll see a movement with the mid or tweeter.
As I said, when I hit the loudness switch it improves dramatically so my bet is the x-over is all up the whack.
These speakers are crap as they stand at the moment, especially alongside the Paradigms. It's like chalk and cheese.
I'll go back to first principles.
Even if it is cheap drivers, the boxes are still usable so a rebuilt might be on the cards.
Regards
Talbit
As I said, when I hit the loudness switch it improves dramatically so my bet is the x-over is all up the whack.
These speakers are crap as they stand at the moment, especially alongside the Paradigms. It's like chalk and cheese.
I'll go back to first principles.
Even if it is cheap drivers, the boxes are still usable so a rebuilt might be on the cards.
Regards
Talbit
If I start with feeding the woofer only from the x-over then that should immediately tell me if the woofer is being feed the correct frequency band. From what you said before, I shouldn't have to have the M & H connected to start with? If it works out the woofer is okay, then I'll add the mid and try a phase reversal. What I haven't done is check for any Notes and Errata in the magazine but I thought I would have spotted it if there was one. It's 5:30 am here so I'll have to wait 'til my other half goes shopping!
Talbit
Talbit
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