hello to all
I purchased a pair of 3 way SD OBS speakers. ( midrange open baffle , ported bass )
seems a previous owner has removed the original xover, and simply fitted;
see photo attatched
1 x 2.2uF cap to the ribbon tweeter. ( 9khz xover )
Cap ( 126uF ) + 4.7 Resistor in series directly to the mid
nothing at all on the bass driver
I dont understand the cap + resistor in series, as for for a simple RC filter, the cap should go across the drive unit.
there are actually 2 caps in parallel, 112 and 14uF , connected to the resistor 4.7 then straight to the mid driver.
these 112uF poly caps are pretty expensive at £ 50 each, I mention this, as Im curious why someone would buy such expensive caps and then create this incorrect xover?
I have seen the xover circuit diagram for the SD1 model, ( larger non open baffle version of the OBS ) and was wondering if I could use that on my speakers.... I know theyre not identical, but Id imagine cant be worse that what Ive got already?
[ the drivers are:- Monicor RBT-180 ribbon tweeter , Dynaudio 5.25" mid ( dont know the model / no labels ) Audax 6.5" paper cone woofer ( dont know the model )
any help greatly appreciated
I purchased a pair of 3 way SD OBS speakers. ( midrange open baffle , ported bass )
seems a previous owner has removed the original xover, and simply fitted;
see photo attatched
1 x 2.2uF cap to the ribbon tweeter. ( 9khz xover )
Cap ( 126uF ) + 4.7 Resistor in series directly to the mid
nothing at all on the bass driver
I dont understand the cap + resistor in series, as for for a simple RC filter, the cap should go across the drive unit.
there are actually 2 caps in parallel, 112 and 14uF , connected to the resistor 4.7 then straight to the mid driver.
these 112uF poly caps are pretty expensive at £ 50 each, I mention this, as Im curious why someone would buy such expensive caps and then create this incorrect xover?
I have seen the xover circuit diagram for the SD1 model, ( larger non open baffle version of the OBS ) and was wondering if I could use that on my speakers.... I know theyre not identical, but Id imagine cant be worse that what Ive got already?
[ the drivers are:- Monicor RBT-180 ribbon tweeter , Dynaudio 5.25" mid ( dont know the model / no labels ) Audax 6.5" paper cone woofer ( dont know the model )
any help greatly appreciated
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It does seem unlikely that what you have is the original OBS crossover: look at the third photo on this page. Lots more parts than in your photo, including at least two inductors.
By the way, yours seem to be a later version than the one being offered on that forum thread, since yours have a ribbon tweeter.
Alex
By the way, yours seem to be a later version than the one being offered on that forum thread, since yours have a ribbon tweeter.
Alex
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All is well. An RC high pass filter has a series capacitor and the resistor goes to ground. In your case the tweeter is the resistor. Then after that there is a resistor added to make the treble more quiet.
Is it possible that the previous owner had bi/tri-amped the speakers and the passive components are error protection / impedance correction?
thanks to all the replies and for the photo of the xover , much appreciated.
yes I guess its possible this pair were used with an active xover, but then again, thats 2 pretty big cap.s that were fitted for impedance correction?
i just know, its a mystery, I will need to remove the existing 'xover' and will build one using the schematic from the SD1 xover
though on the SD1 schematic, it shows the xover as being 2nd order for the bass/tweeter , and a series band pass for the mid
the strange thing is that on the tweeter, the xover consists of a 6.8uF cap and a 0.4mH inductor ....
all SD1 had ribbon tweeters, so dont understand how the cap can be 6.8 , as the ribbon tweeter needs to be xovered at 5khz for 2nd order...... 6.8uF would mean it crossing over at around 2khz .....which makes no sense ... i guess the schematic could be incorrect
yes I guess its possible this pair were used with an active xover, but then again, thats 2 pretty big cap.s that were fitted for impedance correction?
i just know, its a mystery, I will need to remove the existing 'xover' and will build one using the schematic from the SD1 xover
though on the SD1 schematic, it shows the xover as being 2nd order for the bass/tweeter , and a series band pass for the mid
the strange thing is that on the tweeter, the xover consists of a 6.8uF cap and a 0.4mH inductor ....
all SD1 had ribbon tweeters, so dont understand how the cap can be 6.8 , as the ribbon tweeter needs to be xovered at 5khz for 2nd order...... 6.8uF would mean it crossing over at around 2khz .....which makes no sense ... i guess the schematic could be incorrect
NO.
What´s common/normal at "signal" level, where in theory no "power" is involved and "efficiency" is unnecessary becomes quite the opposite when power is involved, as in a speaker cabinet, and to boot you can´t go wild with impedance.
This circuit is a mess:
no speaker crossover EVER will show notyhing like that, it simply shorts a 1 ohm resistor across speaker input terminals.
You will end up with a very hot and unhappy resistor and a blown or at least VERY unhappy amplifier.
Where did you pull that circuit from?
Specially since you said
😕
values look weird but circuit is basically correct, caps in series cut bass from midrange unit and resistor attenuates it.
That said, what you showin tour picture is very poorly made, crude amateurish with poorly supported parts and wiring.
I suppose former owner misunderstood "something he read somewhere" and made that mess.
*Any* crossover fit there at the Factory will be at least, functional, what you show is an unredeemable mess.
Better uproot it and use a proper crossover.
Yes, anybody who believes part brand is all important, while circuit analysis, parts *values*, etc. are minor annoyances to be dispensed with.
Sadly, lots of people think that way.
Nothing can be worse than that.
Any $10 crossover you can buy at Parts Express or anywhere else will be better, because it will at least be functional.
Even if not specific to your model, any crossover meant for those components will be at least a functional starting point.
As an example, this is suggested just for that tweeter:
So do a diligent search and you will find suitable ones 🙂
thank you for the valuable info and advise.
yes I agree, any ready made Xover must be better, what I have is just a high pass filter on the midrange, 126uF , so about 200hz
then the 9khz 1st order on the ribbon tweeter , from what Ive read, 1st orders should never be used on a ribbon, as even tiny amounts of bass can damage the tweeters
I will try the SD1 xover circuit, but use a different cap for the tweeter, to cross at 5khz
I have also seen online, a Kusan 380-C-2 3 way xover, using nice looking air cores and film caps...... it crosses over at 4.5khz, using 2nd order for high+ bass, and 1st order for the midrange... can only see sellers from china, so that would take a few weeks
for now i will try the sd1 circuit.....
yes i agree, very strange that these expensive cap.s were used, but with no real xover circuit
yes I agree, any ready made Xover must be better, what I have is just a high pass filter on the midrange, 126uF , so about 200hz
then the 9khz 1st order on the ribbon tweeter , from what Ive read, 1st orders should never be used on a ribbon, as even tiny amounts of bass can damage the tweeters
I will try the SD1 xover circuit, but use a different cap for the tweeter, to cross at 5khz
I have also seen online, a Kusan 380-C-2 3 way xover, using nice looking air cores and film caps...... it crosses over at 4.5khz, using 2nd order for high+ bass, and 1st order for the midrange... can only see sellers from china, so that would take a few weeks
for now i will try the sd1 circuit.....
yes i agree, very strange that these expensive cap.s were used, but with no real xover circuit
thanks, I had seen that xover with ribbon tweeter online before, they say they ;
' This pre-built crossover is 4th order modified Linkwitz-Riley @ 3.6 khz & prewired with 2x42 strand OFC copper cable '
considering the highs sound pretty good as my speaker is at the moment, and actually it doesnt sound too bad, its just too heavy on the bass / low end, and the mid vocal range is not right ,
no doubt as both the mid + bass are running full range ( well, mid from 200hz up )
that was just a random circuit , nothing to do with the xover on my speakers.... i used it as an example of what a correct circuit looked like.... ignoring the actual component values
SD Acoustic SD1 MKII crossover schematic
I'm not shure if all versions of SD1 has a ribbon tweeter, I remember that there was at least 2: the first with audax loudspeakers and the second with Dynaudio, Scanspeak and, "in my case", Visaton ribbon tweeter.
Searching on the Internet I found some variations, such as Morel components or other brands. Thats's why a double quoted "my case".
Now I'm confused: are those repaired boxes with substituted components?
Anyway I read "OLD" in the upper right corner of this schematic, layed out on a paper marked "Federal Express". So it is something different from an original document.
Maybe there is around the MKII version schema? The only thing in commn seems to be the three 20 MFD capacitors.
I'm not shure if all versions of SD1 has a ribbon tweeter, I remember that there was at least 2: the first with audax loudspeakers and the second with Dynaudio, Scanspeak and, "in my case", Visaton ribbon tweeter.
Searching on the Internet I found some variations, such as Morel components or other brands. Thats's why a double quoted "my case".
Now I'm confused: are those repaired boxes with substituted components?
Anyway I read "OLD" in the upper right corner of this schematic, layed out on a paper marked "Federal Express". So it is something different from an original document.
Maybe there is around the MKII version schema? The only thing in commn seems to be the three 20 MFD capacitors.