SP1200, 1700, or 2500 Crossover Diagrams
- Thread starter Culpeper
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Culpeper
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I'm getting pretty much the same response. Those tapped inductors are just three inductors wrapped into one. I'm not sure how Sansui is claiming 700/6500 with no filtering on the woofer. The xover is really a 2nd order two way setup. I wish I can remember the name of the Japanese company that built these for Sansui. Might be able to find more resources and clues. Without xsim I would have never been able to figure it out. In fact, I'm getting better simulation using a simple 1st order setup. I'm just afraid it would fry the Tweeter or mid.
I'm not as worried about the mids blowing as the tweeters. I think a second order will work, but moving away from the narrow bandpass setup on the mids to a more traditional 2nd order for them. Whatever happens, I think tossing the factory crossover is going to have to be done.
Culpeper
Active Member
Yeah, those xovers are choked up pretty tight. I have an inductor on the woofers and a second pair of two way HUMAN speakers to fill in the voids, lol. Actually, I have four SP2500s in series on one channel (one set has 4 ohms woofers and the other 8). The other channel are the two ways. All on a two channel 80W HK amp. Handles them no problem.
Culpeper
Active Member
Looks like I had the xover components pointing in the wrong direction. I have a spare that I cannibalized to take reading on the inductors. Today I doubled check how the components are connected and discovered I had it a little backwards. This is more like it and I can see how they claim 700/6500 now. Looks like a normal (for its era) rather than narrow bandpass now.
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Culpeper
Active Member
Since the mids and tweeter are paralleled make sure they are showing the correct ohms together. Should be 7 and 7.5, respectively. This is why I'm only showing one speaker using one modified FRD ZMA file.
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Culpeper
Active Member
http://www.radiocollection.be/fr/Sansui_sp2500_fr.html
I took another look at his schematic. Also the K on the resistor is code for +/- 10%.
I took another look at his schematic. Also the K on the resistor is code for +/- 10%.
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Culpeper
Active Member
Checking Clear, Natural, and Soft from the tapped inductor shows 16 ohms at the resistor only on the Clear setting. This lowers dB -3 on Clear. Natural and Soft are dead at the resistor. Like moefuzz explains on page 1, all the tapped inductor does is increase the slope from Clear to Soft. So, on the midranges the settings increase or decrease the left midrange slope in relation to the midrange and the woofer. On the Tweeters it increases or decrease the tweeter slope between the midrange and tweeter. Clear is the lower slope and Soft is the deepest slope. Natural has no material change in dB and Soft has a respectable -6 dB. So, after modeling on Xsim all I'm gong to do is add a -3 dB L-Pad on the midrange and tweeter and make the woofer a 2nd order filter in addition to a Zobel. Based on the media playback material during its era there was no need for extra nice low bass. However, Sansui did on these models increase the high frequency response that was some of the best in its price range at that time. With today's media playback the woofer section needs improvement and the high frequency area need toned downed a little. Also, when you pick your woofer do so that you can use them in a sealed boxed for about 1.3 cubic feet for the 2500. The original ported box is not optimal any longer when upgrading the woofer. The 1200 and 1700 will need similar change from ported to sealed. If not upgrading the woofer than L-Pads may be the only improvement of choice if needed or desired.
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Culpeper
Active Member
I can finally lay this autopsy of the SP2500 to rest. It is not a bad design and clearly there are Klipsch and JBL influences here. There are even rumors that the latter were involved with the design and JBL and Sansui did have a joint venture during this period so it is feasible. First, the box itself. It is not too small. It is just built from the port sizes up (2.5"x3.125"). The box is rated 50-20Khz. So using 50 Hz it is not too hard to calculate the end correction factor for the ports. From there we can calculate box size to approx. 1.3 cu. ft., which just happens to be the size of the internal enclosure itself. So, that mystery is solved. As for the crossover, Sansui or whomever was more interested in acoustic effect (think Kabuki Bose) rather than electrical so we are not going to find the predicted values of the crossover components present on these boards. This became clear when measuring SPL plotting by hand. There are cost cutting measures present that was put into this theory as well. Example, the specs state the crossovers are at 700/6500. The former is probably some acoustic number and the 6500 an average based on the tapped tweeter inductor. The bottom number is impossible to achieve using an electrical response with the original woofer or any replacement woofer. The midrange is just choked up too much and the woofer to midrange has an intentional exaggerated overlap as a result. Thus, the crossover network is really just for the twin midranges and twin tweeters both in parallel. Interesting, and accoustic in nature again, the tweeters and midranges are connected in reverse polarity (same effect as just reversing polarity at the woofer). Tweaking the tone knobs only increase or decrease the left slope of the midranges and tweeters. The higher frequency loudness can be a little too much to handle with today's playback media. But there is a cheap solution to bringing these boxes up to date and playing very well without fatigue.
My SP2500 tweak is cheap and consists with starting with the replacement woofer. 8 ohm is the most abundant out there so forget about finding a new 6 ohm 12" woofer on a budget. Mine are a couple of Pioneer badged 12" from Parts Express. The woofer needs just a little filtering so I used an undersize 1.0 mH inductor and normal size15 uF capacitor for a 2nd order at the woofer. The inductor was mounted in the box and the capacitor was mounted in-line. The type of woofer doesn't really matter just make sure it can be used in a sealed or ported box as far as specs go. I also added a Zobel to even out the impendence. I won't go into capacitor replacement on the crossover because it has been beaten to death but it is something that needs to be done. I used some of the better caps but in hindsight they might just be too good for these speakers. You may just end up with more high frequency SPL than you intend to get. The midranges and tweeters are that good. If I had to do it over again I would have just went with the $1 caps (same thing with the Zobel). The midranges and tweeters are no joke and they may need to be choked down -3dB with L-Pads. With my 80W HK amp at about 15 watts output I'm getting an average acoustic SPL of 93 dB with a standard deviation of less than 6 dB (36 plots measured between 40-10khz) in my listening room and will pick up 19kHZ at 65 dB. Sounds most excellent now. Kabuki Heresy III territory. Don't expect spectacular bass below 50Hz. It is just not going to happen and Sanui is relying more on perceived lower response as most commercial manufacturers do to this day. There is some good science on that topic but this isn't the place.
L-Pad for midrange resistors I used are 2S/12.5P. The tweeters were 2S/16P. L-Pads were connected in-line and stapled to the rear panel board. Zobel cap and resistor will depend on individual woofer specs. Mine were placed right at the woofer terminals. So, I never made a network component board for any tweaks.
I think with a couple of MCM 55-2952 woofers and economy capacitors and resistors the whole thing could be less than a $60 upgrade and big improvement.
My SP2500 tweak is cheap and consists with starting with the replacement woofer. 8 ohm is the most abundant out there so forget about finding a new 6 ohm 12" woofer on a budget. Mine are a couple of Pioneer badged 12" from Parts Express. The woofer needs just a little filtering so I used an undersize 1.0 mH inductor and normal size15 uF capacitor for a 2nd order at the woofer. The inductor was mounted in the box and the capacitor was mounted in-line. The type of woofer doesn't really matter just make sure it can be used in a sealed or ported box as far as specs go. I also added a Zobel to even out the impendence. I won't go into capacitor replacement on the crossover because it has been beaten to death but it is something that needs to be done. I used some of the better caps but in hindsight they might just be too good for these speakers. You may just end up with more high frequency SPL than you intend to get. The midranges and tweeters are that good. If I had to do it over again I would have just went with the $1 caps (same thing with the Zobel). The midranges and tweeters are no joke and they may need to be choked down -3dB with L-Pads. With my 80W HK amp at about 15 watts output I'm getting an average acoustic SPL of 93 dB with a standard deviation of less than 6 dB (36 plots measured between 40-10khz) in my listening room and will pick up 19kHZ at 65 dB. Sounds most excellent now. Kabuki Heresy III territory. Don't expect spectacular bass below 50Hz. It is just not going to happen and Sanui is relying more on perceived lower response as most commercial manufacturers do to this day. There is some good science on that topic but this isn't the place.
L-Pad for midrange resistors I used are 2S/12.5P. The tweeters were 2S/16P. L-Pads were connected in-line and stapled to the rear panel board. Zobel cap and resistor will depend on individual woofer specs. Mine were placed right at the woofer terminals. So, I never made a network component board for any tweaks.
I think with a couple of MCM 55-2952 woofers and economy capacitors and resistors the whole thing could be less than a $60 upgrade and big improvement.
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Sorry, I've been swamped with work, and the Sansui stuff is on hold for a while. The connectors I picked up at Autozone for another project, they just happened to work. It's a variety pack of multi-way gold plated connectors.
I'm with you on the woofer going 2nd order at least. Dayton Classic 12, or even the dual voice coil 12" sub (SD-315A-88) look like they'd run decent in the factory enclosure, sealed for the Classic, tweak the ports for the sub. Getting the sub to play up into the midrange will require 4th order, at least how Xsim looks.
I run an HK 3475, and I'm considering the DVC sub off the rear 2 channels at 4ohms, then the front 2 channels powering the mid/tweet. That may let me forgo the Lpads.
I'm with you on the woofer going 2nd order at least. Dayton Classic 12, or even the dual voice coil 12" sub (SD-315A-88) look like they'd run decent in the factory enclosure, sealed for the Classic, tweak the ports for the sub. Getting the sub to play up into the midrange will require 4th order, at least how Xsim looks.
I run an HK 3475, and I'm considering the DVC sub off the rear 2 channels at 4ohms, then the front 2 channels powering the mid/tweet. That may let me forgo the Lpads.
Culpeper
Active Member
So, got tired of working with the whole band pass and HF filters. I have a couple of MCM $19 woofers with just 1.0 mH inductors on them that have pretty good specs for some reason. For the tweeters I started out with just the 2.2 uF capacitor but the tweeters are pretty sensitive and was about 12dB too high. So, I swapped out the capacitor with 1.2 uF and a 30R shunt resistor. This got everything into line. Since the bass and tweeters are 1st order we don't have to worry about phase alignment. This really opens the door to the tweeters with plenty of protection. Bass is very nice and holds its own like a Heresy III. I left the ports as is. The midranges are left at the Natural (1.062 mH setting). I used SPL Copy to put together a FRD and ZMA file. Those got me started using Xsim to get a good idea of the electrical response. Polarity on the band pass is reversed. Frequency response graph below was measured in the cabinet and the listening room at near field. So, it is an acoustic response. Sort of ironic that this is so simple and yet so good. I'm thinking on bypassing the parallel midrange cap and transformer and make it a full 1st order. That will need a different cap on the tweeter.
Woofers:
http://www.newark.com/mcm-audio-select/55-2952/12-woofer-with-paper-conecloth/dp/80R7003
Woofers:
http://www.newark.com/mcm-audio-select/55-2952/12-woofer-with-paper-conecloth/dp/80R7003
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