I’m rehabbing an old pair of Sansui SP-X6000 speakers from the late 70s. These are big box 3 ways and three of the six original drivers are blown. Rather than try to find OEM drivers, I’m replacing them with modern drivers from parts express. While the replacement drivers work with the original crossovers (which have adjustable warm/neutral/cool settings), the sound is not ideal. They are very bright, even on the “soft” setting and aggressive DSP can only do but so much to tone down the highs.
I am fully aware that what I’m attempting is not the pathway to top-tier sound, but the speakers have sentimental value and I’m treating this as a fun project to learn about crossover design and driver integration. I’ve made C-notes, but that is my only speaker building experience.
I’ve purchased some cheap drivers that fit in the cabinet, and all are 8 ohm.
GRS 10PF-8 10" woofer, 40-5000 Hz, Fs: 43, sensitivity: 87
GRS 5SBM1-8 5-1/4" mid, 500-10K, Fs: 493, sensitivity: 93 (!)
T-25 2-1/2" tweet, 3200-20K, Fs: 1600, sensitivity: 90
I only have a graph for the woofer and it seems perfectly happy up to 1000 Hz
The major issue is the difference in sensitivity between the drivers. The mid needs -6db and the tweet needs -3db to match the woofer.
Using the diyaudioandvideo online calculator tools, I’ve come up with a 1st order crossover design (attachment #1). I settled on 1st order as it requires fewer parts, reduces complexity, and the sharp filters between drivers may reduce comb filtering between the tweeter and midrange since they are arranged side-by-side.
Resistors will be added to trim the tweeter and midrange as determined by the driver attenuation circuit calculator (attachments #1 and #2)
My major questions:
Overall, how is my strategy looking?
Do I need to factor in the resistance of my capacitors and inductors in my LPad? Which resistor would this impact (series or parallel or both)?
Should I factor in bandpass gain? Does this only happen when I reverse one of the driver’s polarity?
Should I attempt to factor in baffle step compensation? Recommended software for this?
The end use for these will be providing tunes in my workout room. The low end will be supplemented with an old 10” Polk sub, probably crossed 60-80 Hz depending on room gain. Rock/Metal will be played for the most part. The woofer I chose is more suitable for a sealed cabinet, so I plan on stuffing both front-firing ports with foam bungs.
Cheers everyone.
I am fully aware that what I’m attempting is not the pathway to top-tier sound, but the speakers have sentimental value and I’m treating this as a fun project to learn about crossover design and driver integration. I’ve made C-notes, but that is my only speaker building experience.
I’ve purchased some cheap drivers that fit in the cabinet, and all are 8 ohm.
GRS 10PF-8 10" woofer, 40-5000 Hz, Fs: 43, sensitivity: 87
GRS 5SBM1-8 5-1/4" mid, 500-10K, Fs: 493, sensitivity: 93 (!)
T-25 2-1/2" tweet, 3200-20K, Fs: 1600, sensitivity: 90
I only have a graph for the woofer and it seems perfectly happy up to 1000 Hz
The major issue is the difference in sensitivity between the drivers. The mid needs -6db and the tweet needs -3db to match the woofer.
Using the diyaudioandvideo online calculator tools, I’ve come up with a 1st order crossover design (attachment #1). I settled on 1st order as it requires fewer parts, reduces complexity, and the sharp filters between drivers may reduce comb filtering between the tweeter and midrange since they are arranged side-by-side.
Resistors will be added to trim the tweeter and midrange as determined by the driver attenuation circuit calculator (attachments #1 and #2)
My major questions:
Overall, how is my strategy looking?
Do I need to factor in the resistance of my capacitors and inductors in my LPad? Which resistor would this impact (series or parallel or both)?
Should I factor in bandpass gain? Does this only happen when I reverse one of the driver’s polarity?
Should I attempt to factor in baffle step compensation? Recommended software for this?
The end use for these will be providing tunes in my workout room. The low end will be supplemented with an old 10” Polk sub, probably crossed 60-80 Hz depending on room gain. Rock/Metal will be played for the most part. The woofer I chose is more suitable for a sealed cabinet, so I plan on stuffing both front-firing ports with foam bungs.
Cheers everyone.
This might give you some ideas:
All GRS small 3-way -
Techtalk Speaker Building, Audio, Video Discussion Forum
Different woofer and cabinet size, of course but similar concept. Same mid and tweeter I think.
Geoff
All GRS small 3-way -
Techtalk Speaker Building, Audio, Video Discussion Forum
Different woofer and cabinet size, of course but similar concept. Same mid and tweeter I think.
Geoff
NB Because the cabinet sizes are quite different - the width and volume in particular - it needs someone with more expertise than me to look at your XO. For example, your cabinet is much wider, so the amount of Baffle Step Compensation (BSC) will differ. Your 10" may well produce more bass than the 8" in the referenced project. Someone here should be able to advise you further on these matters.
GRS doesn't publish graphs for its drivers,which makes modelling difficult.
Geoff
GRS doesn't publish graphs for its drivers,which makes modelling difficult.
Geoff
Suggest you cross over woofer to mid at the baffle step frequency - that depends on the width of your cabinet. Then go second order for the tweeter, and connect it reverse phase. This gives better power protection and keeps the phase aligned better.
A good L-Pad calculator here: L pad calculator - attenuation dB damping impedance decibel loudspeaker speaker voltage divider - sengpielaudio Sengpiel Berlin.
Can't see a spec sheet for the Mid on Parts express site; where did you get your impedance data from?
Looking at your xover design, it appears you have assumed all are 8 Ohm - not the case! 8 ohms is the 'nominal' impedance; for crossovers you need to use actual impedance, which varies with frequency....
A good L-Pad calculator here: L pad calculator - attenuation dB damping impedance decibel loudspeaker speaker voltage divider - sengpielaudio Sengpiel Berlin.
Can't see a spec sheet for the Mid on Parts express site; where did you get your impedance data from?
Looking at your xover design, it appears you have assumed all are 8 Ohm - not the case! 8 ohms is the 'nominal' impedance; for crossovers you need to use actual impedance, which varies with frequency....
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The Sansui speaker dimensions seem to be 39cm wide, 64cm high and 28cm deep, which I think would make that frequency about 400Hz?
Geoff
I make it 115/.39 = ~295Hz. Good news is that when crossing that low, the mid and woofer impedance is near enough to Re, which can be used for calculations.
Thanks for all the feedback everyone.
It looks like I may have made a misstep with my driver selection. Having a midrange with such high sensitivity seems to exacerbate the BSC issue.
The other elephant in the room is lack of good measurements to use for modelling. From what I've read, the experienced crossover designers will measure their drivers in situ and make design decisions from there. I have a calibrated mic and REW, but am a total novice at using those, so I doubt I'll take that leap this go around.
How about going this direction with the midrange:
GRS 5PF-8 - 5.25" Woofer
Sensitivity is 84 db, so 3 db lower than the woofer. I can cross it around 300 Hz as PeteMcK suggests. I'll have to do a bit more modeling, but I'm willing to spend the $15 bucks to grab these guys and save the high-efficiency midranges for a future project.
By the way, here are the measurements for the woofer:
GRS 10PF-8 - 10" Woofer
Now, for determining the mid/tweet crossover, I think the minimum should be 3200 Hz. The mid is starting to lose sensitivity at 3000 Hz and impedance is climbing. These tweeters were only 3 bucks each, so if I fry one, it is not the end of the world. I believe a good rule of thumb is crossing an octave above the Fs. Is there any contraindication for using a midrange to cover so many octaves?
And using a 2nd order crossover for the mid seems counterintuitive to me as wouldn't that create bandpass gain for the mid?
I appreciate all the comments and insight. This has been hugely educational.
It looks like I may have made a misstep with my driver selection. Having a midrange with such high sensitivity seems to exacerbate the BSC issue.
The other elephant in the room is lack of good measurements to use for modelling. From what I've read, the experienced crossover designers will measure their drivers in situ and make design decisions from there. I have a calibrated mic and REW, but am a total novice at using those, so I doubt I'll take that leap this go around.
How about going this direction with the midrange:
GRS 5PF-8 - 5.25" Woofer
Sensitivity is 84 db, so 3 db lower than the woofer. I can cross it around 300 Hz as PeteMcK suggests. I'll have to do a bit more modeling, but I'm willing to spend the $15 bucks to grab these guys and save the high-efficiency midranges for a future project.
By the way, here are the measurements for the woofer:
GRS 10PF-8 - 10" Woofer
Now, for determining the mid/tweet crossover, I think the minimum should be 3200 Hz. The mid is starting to lose sensitivity at 3000 Hz and impedance is climbing. These tweeters were only 3 bucks each, so if I fry one, it is not the end of the world. I believe a good rule of thumb is crossing an octave above the Fs. Is there any contraindication for using a midrange to cover so many octaves?
And using a 2nd order crossover for the mid seems counterintuitive to me as wouldn't that create bandpass gain for the mid?
I appreciate all the comments and insight. This has been hugely educational.
If you haven't bought the drivers yet, forget the GRS units, they're rubbish. You can do much better for not much more money. Have a look at the SB PFC drivers
I'm sure those drivers are far superior to the budget GRS drivers I have in hand. However, those woofers alone equal my target budget for this entire project. 40 year old cabinets with an antiquated driver layout probably won't do your suggested drivers justice. I'd just like to get the smoothest response possible given my constraints. Taming the midrange seems to be the biggest challenge and if there is a more elegant solution than putting big resistors in front of the GRS 5SBM1-8, I'd be all for it. Getting the less efficient mids, crossing the woofer low, and attenuating the tweeter seems like the way forward.
I assume you checked out the Parts Express build, what did you think of the project?
Similar drivers to yours, different cabinet but perhaps someone with the right expertise could work something out for you. It was a sealed cabinet, not sure if your Sansuis are sealed or vented: I understand that GRS woofers are better suited to sealed due to their specs. However, the way the designer worked through the various issues is well worth an optic.
Re costs, the SB PFC drivers are cheaper in Oz than the GRS due to the $A value relative to the $US and high shipping costs.
Geoff
Similar drivers to yours, different cabinet but perhaps someone with the right expertise could work something out for you. It was a sealed cabinet, not sure if your Sansuis are sealed or vented: I understand that GRS woofers are better suited to sealed due to their specs. However, the way the designer worked through the various issues is well worth an optic.
Re costs, the SB PFC drivers are cheaper in Oz than the GRS due to the $A value relative to the $US and high shipping costs.
Geoff
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I did have a look at the GRS 3 way. That build uses different drivers than those I have selected, so I'm not sure how much I can learn from the crossover design. Their woofer is less efficient than their mid, so there is some attenuation on the mid, but I have no idea why they have a resistor in parallel with the woofer. It doesn't appear BSC has been employed, but maybe they have them up against a wall and are benefiting from room gain.
Putting the speakers on their side makes sense if trying to reduce tweet/mid comb filtering. I can't do this as my tweet/mid config is not mirrored. I misspoke earlier--a 1st order crossover is actually going to exacerbate the comb filtering issue as the tweet and mid will both be playing overlapping frequencies. 1st order also precludes crossing the woofer low, as I'd be asking the mid to play outside its frequency range.
I'm really stuck without good measurements for the drivers. Maybe I'll just have to get out the microphone and see what I can learn before making any crossover design decisions.
Makes total sense on the driver cost issue. Glad you guys get some stuff discounted Down Under.
Putting the speakers on their side makes sense if trying to reduce tweet/mid comb filtering. I can't do this as my tweet/mid config is not mirrored. I misspoke earlier--a 1st order crossover is actually going to exacerbate the comb filtering issue as the tweet and mid will both be playing overlapping frequencies. 1st order also precludes crossing the woofer low, as I'd be asking the mid to play outside its frequency range.
I'm really stuck without good measurements for the drivers. Maybe I'll just have to get out the microphone and see what I can learn before making any crossover design decisions.
Makes total sense on the driver cost issue. Glad you guys get some stuff discounted Down Under.
My mistake, I thought the tweeter and the mid were the same as yours.
Unfortunately, we don't get anything 'discounted' here, it's just that everything is so expensive relative to the US.
Drivers such as Dayton Audio have become much more costly here relative to the SBs, Visaton and some Peerless, as they're sourced from India or Indonesia.
I assume you've done a search on Part Express Tech Talk for GRS projects? There might also be members there who could help you.
HTH
Geoff
Unfortunately, we don't get anything 'discounted' here, it's just that everything is so expensive relative to the US.
Drivers such as Dayton Audio have become much more costly here relative to the SBs, Visaton and some Peerless, as they're sourced from India or Indonesia.
I assume you've done a search on Part Express Tech Talk for GRS projects? There might also be members there who could help you.
HTH
Geoff
This looks like a similar project, unfortunately it's not useful as the speakers use some sort of generic crossover - but at least it shows that people have done similar projects to yours and enjoyed them.
Hugo Lazarte Cuervo | Parts Express Project Gallery
Geoff
Hugo Lazarte Cuervo | Parts Express Project Gallery
Geoff
Very interesting. Those are my exact woofers and midranges in a very similar configuration. I wish he'd provided more info on that crossover, but at least he recognized the need to tame the midrange with that variable resistor.
I went down the youtube rabbit hole last night looking at a crossover design videos, and am more convinced than ever that individual measurements of each driver in the enclosure are essential. Otherwise, I'm basically guessing and tweaking with a bunch of components will be expensive and tedious.
I found the original crossover diagram for the SP-X6000s online and discovered that the midrange is intended to be in a reverse polarity configuration. Modeling the response with normal polarity reveals in Xsim shows me why my new drivers sound so weird with the old crossover and why crude DSP adjustments didn't help address the weird peaks and troughs that resulted. I'll try the polarity swap and see if DSP helps me out---this would solve all kinds of problems.
I went down the youtube rabbit hole last night looking at a crossover design videos, and am more convinced than ever that individual measurements of each driver in the enclosure are essential. Otherwise, I'm basically guessing and tweaking with a bunch of components will be expensive and tedious.
I found the original crossover diagram for the SP-X6000s online and discovered that the midrange is intended to be in a reverse polarity configuration. Modeling the response with normal polarity reveals in Xsim shows me why my new drivers sound so weird with the old crossover and why crude DSP adjustments didn't help address the weird peaks and troughs that resulted. I'll try the polarity swap and see if DSP helps me out---this would solve all kinds of problems.
I've never built a three way but have looked at many, the mids are almost always connected with reverse polarity.
The mid-range section of the XO seems to be the most complex in well designed three ways. It has both low and high pass components, otherwise the sound from the mid interferes with the tweeter and woofer. Looking at the XO in that project, it would not have those features.
Geoff
The mid-range section of the XO seems to be the most complex in well designed three ways. It has both low and high pass components, otherwise the sound from the mid interferes with the tweeter and woofer. Looking at the XO in that project, it would not have those features.
Geoff