-
Categories
-
Platforms
-
Content
The definition of a capacitor is two conductors separated by an insulator. The capacitor symbol is a representation of that.
The "spring looking drawing" for a coil is a representation of the coil's windings.
Something else to consider is that the impedances of the drivers are not linear; That is, an "8Ω" woofer is not 8 ohms at all frequencies (this is why the calculated values for crossover components are not always close to the values determined in the lab).
It seems to me that you might be better off using separate amplifiers for each driver with the crossover dividing the audio spectrum between the amps rather than a passive crossover between the amp and the drivers. That would allow a very sharp rolloff at the ends of the spectra presented to the drivers and much less chance of interference between sounds produced by the drivers.
I think any delays caused by the conductors within the speaker will have no notable effect.
What will have a much larger effect is the difference between the areas where the speakers propagate sound at various frequencies (higher frequencies tend to come from the small end of the cone and lower ones from the wide end and the same goes for horns), particularly in the crossover zone (the crossover point is usually the point where the outputs of the drivers producing the same sound are approx. 3dB down and both drivers are producing some sound for about an octave above & below that frequency). This can result in the sounds from, for example, a woofer and a midrange to be out of phase, which can lead to sounds produced by both being cancelled or reinforced at some places in the listening area. Usually the designer will chose whether to connect the midrange &/or tweeter electrically in phase or out of phase to the woofer to compensate for that.
I would suggest that most of what you have read about so-called high end speaker wire is gibberish produced by people trying to separate you from your money.
It is forgotten now but when the first special cables for speakers came on the market half a century ago they consisted of multiple strands of enamelled wire braided together with half of the strands connected together for positive and the other half for negative. It sounded good in theory but in practice the strands acted like a capacitor and, since the impedance of a capacitor decreases as frequency increases they were pretty close to a short circuit at something like 200khz. The thing is that while people can't hear 200 Khz transistors can amplify it and it didn't take much stray signal getting into an amp to make it produce enough signal into that near short to pop the power transistors...
The best advice when I was in the speaker industry was to use ordinary AWG 16 lamp cord and keep the runs under 30 feet. I doubt that things have changed much since then in that respect.
I don't have time to study the schematic you produced right now (spring, planting garden, daylight is burning) so maybe someone else can comment on it.
To the moon and back, maybe if you're lucky you'll experience the difference.
(because you will now be considerably poorer due to the cost of the cable)
yes, i have considered using an active crossover with another miniDSP and 2 amplifiers. BUT that will be another future project if i dont like the results from my XO upgrade.
A lot of what you have stated i am aware of and have considered before going ahead. I believe i have gone about cloning the current crossover in the best way i can practically do.
I have an LCR meter to measure the components and ability to measure the frequency response, phase etc etc of the completed system. I have tested the LCR meter with known value components and found it to be accurate.
Everything i replace will be as identical values of inductance, resistance and capacitance as possible.
I use 12AWG 99.99% OFC from KabelDirect in germany, 777strands per wire. its really nice cable and not expensive, no bells and whistles its just wire! - i made it look fancy and put some of my own connectors on but anyway, a lot of this im repeating from previous posts.
All im getting to grips with now is laying out the crossover design ready for when all the parts arrive.
Thanks for the input all,
If anyone can check out that crossover compared to the images of the original please. Let me know if you see any errors.
The woofer section seems much simpler.
Cheers
A lot of what you have stated i am aware of and have considered before going ahead. I believe i have gone about cloning the current crossover in the best way i can practically do.
I have an LCR meter to measure the components and ability to measure the frequency response, phase etc etc of the completed system. I have tested the LCR meter with known value components and found it to be accurate.
Everything i replace will be as identical values of inductance, resistance and capacitance as possible.
I use 12AWG 99.99% OFC from KabelDirect in germany, 777strands per wire. its really nice cable and not expensive, no bells and whistles its just wire! - i made it look fancy and put some of my own connectors on but anyway, a lot of this im repeating from previous posts.
All im getting to grips with now is laying out the crossover design ready for when all the parts arrive.
Thanks for the input all,
If anyone can check out that crossover compared to the images of the original please. Let me know if you see any errors.
The woofer section seems much simpler.
Cheers
i am aware of placebo, bias, confirmation bias etc etc i will be using measurments AND listening to determine if i like it more.
OK, fresh day, fresh head. iv re-done it again.
Iv quad-checked it and to my eyes that looks right.. but this is the first time iv done it so its possibly wrong.
ive marked out better on the rear of the PCB the components to make it easier to see.
wires with the colour line are the NEGATIVE (-) terminal.
Thanks for looking.
*EDIT* ignore the word WOOFER, thats below.
Last edited:
I am about to write what you do not want to read. lol!
I've upgraded filter networks on several speakers and I believe there are significant gains to be made, but different caps have different impact on sound quality.
A big bass cap is going to have little to no impact. Unless the speaker is 25+ years old, it is probably a waste to replace it.
Small caps, such the cap inline to your tweeter have a lot more potential for sound quality gain.
I haven't tried many cap brands but I really like Mundorf Gold caps on tweeters and mids. They perform as well as anything I've heard and they are reasonably priced in smaller values. In big values in a woofer circuit, I cannot tell the difference between a Mundorf Gold and a Solen from Parts Express.
I'm not saying Mundorf are the best. I haven't done an exhaustive test of all brands and I am not in a position to quantify it. The next pair of speakers I recap will be tested with REW before/after the re-cap. That will allow me to inspect the speakers objectively to go along with subjective listening tests.
Some years ago now, I fixed up a pair of Heco Superior 700 from 1983. One made sound but no woofer or tweeter. The other had just a non-working tweeter. I was familiar with that model from the early 80s when I worked in an audio store, and thought I had enough replacement drivers to repair them. It turned out, all drivers were fine. The problem was the crossover networks. Heco, being German, used Mundorf caps back in the day. It's just a matter of not hearing anything I feel sounds better than Mundorf.
Polk uses some generic looking, white wrapper, caps in the RTi series. I re-capped both of my A9 with Mundorfs for a very real quality improvement. I did not replace the big woofer cap in the A9, BTW. Replacing the largest value caps would have doubled the cost and I have no expectation of being able to tell the difference.
Good luck with whatever you do and I hope you report back with results.
Last edited:
None of that stuff matters.
The job of a sound system is to make you happy. If it succeeds, it is doing it's job.
Mission make some nice speakers.
I believe what is happening here is they are utilizing a cost saving technique that I have not tried but is said to work. It is easy to tell the sound quality difference between a really good cap and a poor quality cap and the price reflects it.
I believe Paul McGowan at PS Audio came up with the idea to use two caps, one large and cheap, the other small and high quality, in place of a single large cap for both cost and sound quality benefit. That seems to be what your diagram indicates.
In the case of the 14uF tweeter cap, they have parallel connected a 10uF and a 4.7uF. I would expect the 4.7uF to be a very high quality cap and the 10uF to be more affordable. People I trust tell me it works, and PS Audio has some amazing products, so I don't question this approach despite having no experience or ability to endorse it personally.
If those were my speakers, I would be inclined to go top quality on the small value caps and leave the higher value partner alone.
Sorry for posting so much...
When I did a five way capacitor shoot-out some years ago, I unsoldered the tweeter capacitor from the network circuit board and wired it out the back of the speaker. I unscrewed the terminal plate, ran the wires out, and sealed it with blue-tack before screwing down the terminal plate again with the wires pinched.
From there, I could try a bunch of caps quickly. You might enjoy doing this, if you enjoy playing with caps and are trying to educate yourself on the various brands and models.
When I did a five way capacitor shoot-out some years ago, I unsoldered the tweeter capacitor from the network circuit board and wired it out the back of the speaker. I unscrewed the terminal plate, ran the wires out, and sealed it with blue-tack before screwing down the terminal plate again with the wires pinched.
From there, I could try a bunch of caps quickly. You might enjoy doing this, if you enjoy playing with caps and are trying to educate yourself on the various brands and models.
dont apologise any input is welcome.
Thanks,
i have thought about upgrading only the MF/HF network but while im there i may aswell do the lot, the woofer network is only 1 inductor, 1 resistor and 2 caps in bypass as you say. Even if i can't tell much difference, knowing its done is peace of mind.
Im going to try some caps i have been reccomended and definitly replace the electrolytics with pp caps, im not going mad on the caps for the woofers, they are not that expensive really.
Thanks for the input.
If you know how to read Xover diagrams please take a look at mine and see if ive done it right
Cheers
Thanks,
i have thought about upgrading only the MF/HF network but while im there i may aswell do the lot, the woofer network is only 1 inductor, 1 resistor and 2 caps in bypass as you say. Even if i can't tell much difference, knowing its done is peace of mind.
Im going to try some caps i have been reccomended and definitly replace the electrolytics with pp caps, im not going mad on the caps for the woofers, they are not that expensive really.
Thanks for the input.
If you know how to read Xover diagrams please take a look at mine and see if ive done it right
Cheers
on the contrary, im happy to hear your views.
I might be banned for typing this but... different caps have different sound characteristics. It's not just about upgrading and, IMO, more expensive doesn't mean better sound.
Mundorf have a smooth sound that I like.
There are a couple of other brands that will sharpen the top end a bit. That might not be a big deal on a speaker with a soft dome tweeter but it can be over-the-top on an aluminium or titanium dome tweeter.
"aluminium" ... you Brits... lol!
(no disrespect intended... my family is from Britain)For this reason, you may enjoy trying a few different brands using the external wiring technique described above. Who knows, you may not find any difference at all and it will be an opportunity to save a bunch of quid.
If you know how to read Xover diagrams please take a look at mine and see if ive done it right
If you want me to do so, I will do a diagram and see if I come up with the same schematic as you but it isn't necessary to dive so deeply into it. You can just replace the small value of every parallel pair with a like value. Or, you can replace them both with a single cap of the summed value if you don't believe in the big/little approach.
Understanding the circuit isn't required and isn't possible until you account for the series resistance of some of these components. Once you have the series resistances, you can calculate the crossover behaviour precisely, if that is your goal.
Last edited:
I just had a quick scan of your schematic. I don't understand the amplifier input. What goes to what? I assume it has dual binding posts for bi-wire/bi-amp? Can you please draw these as your diagram does not have this detail.
Also, not sure that is going on with L3. Is it 0.72mH or 0.127mH? Your schematic doesn't seem to align with the image. I believe that is the vertical coil that is not labelled in a way that is visible in the pic.
Also, not sure that is going on with L3. Is it 0.72mH or 0.127mH? Your schematic doesn't seem to align with the image. I believe that is the vertical coil that is not labelled in a way that is visible in the pic.
i definitly do want to build it all from scratch and seperate it into 2 boards, thats why i didnt even draw the woofer section yet.
Is measuring the resistance simply removing the part and doing a resistance measurment with my LCR meter?
The inductors are just a measurment i took without removing the component from the circuit, so i dont know if thats actually correct yet ( i dont know if you can measure them in circuit or not), when i measured it the tweeter plays the tone the LCR meter uses to read the inductance, so i have no idea but i have a feeling that its not 0.127mh becaue of this. However i will remove and measure the inductance and resistance of ALL the coils off board before i order new ones.
Learning as i go
im considering copper foil inductors for the tweeter / mid section and waxed/baked air core inductors for the woofer inductor.
the black mark on the cable is simply some glue i think they stuck the wire to the side of the cabinet so it doesnt move around in there. its definitly not a burn or damage.
As for capacitor choice i dont really want to be experimenting so much, so i will go with miflex for bypass (small) caps and probably ClarityCap CSA for the larger values , the 56uf and 80uf are HUGE and ill probably use JB JFX for that as not many of the manufacturers do that value, or use 2x40uf for example in parralel (miflex 80uf would be like a petrolium tanker size i gueess and be about £30,000 hahaha)
But yes, please, go ahead and draw up the network as you would do it, but if possible make it as easy for me to read as possible
thanks for the replies my man.
Cheers
the benefit i hear of bypass caps is the charge/discharge time. but the downside is it can cause "phase shift" - but as this default network already has bypass caps im pretty sure Peter Comeau took this into account when designing the network for mission.
So i will be keeping an eye on phase when i take measurments.
So i will be keeping an eye on phase when i take measurments.
