120studio.com 4/8/2015

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Intro

If you've read much on this site, you'll know I like cheap gear that works well.

A couple years ago, I picked up a pair of Sansui SP-30's for next to nothing.    Here's a review, with some details on how to make them sound better.


A Quick Note


This article is made possible only by the support of readers like you, when you use the links on here to purchase your gear.

The small commissions from sales are what allow me to keep this site going.   Thank you in advance for your help.


In This Article


Some Specs

General Characteristics


Re-Capping

Blown Speakers


Distortion

Price / Value

Conclusion



 (Shown with the latticework grill removed.)



Some Specs



Cabinet Material:  Plywood
Capacitor:  2.2 microfarad, 25 volts, bipolar electrolytic (1 per tweeter)
Crossover Frequency:  7,000 Hz
Dimensions:  17" tall x 11" wide x 8" deep 
Frequency Response:  50 Hz - 20,000 Hz
Impedance:  8 ohms
Made In:  Japan
Power rating:  20 watts max.
Sensitivity:  91 dB/Wm
Tweeters:  Sansui T-50N, horn-type, 10 watts (1 per speaker)
Weight (each):  about 9.5 pounds
Woofer size:  6.5 inches
Woofers:  Sansui W-30 (1 per speaker), 6.5 inch
Years of Manufacture:  1968-'72




General Characteristics

The SP-30 was the smallest in a whole line of SP-series speakers from Sansui.  They were made in the late Sixties and early Seventies.


First, the drawbacks.   The bass response is somewhat weak.  The treble really isn't that prominent, either;  the midrange is great, though, and the mid-high and the mid-bass sound good (or at least, not annoying to my ear).  It's really just the extreme ends of the frequency range that roll off, but that's not too surprising for a pair of small speakers made more than forty years ago.  

Also, these speakers do not handle overmodulated or "red-lined" recordings very well.   Then again, these are 20-watt bookshelf speakers.  If you're listening to a mix-CD or cassette, and suddenly a red-lined song comes on, turn down the volume.  Otherwise, you could damage these speakers.

Now, the positives.   Even though it's a cheap speaker, the SP-30 is still surprisingly good.  Aside from the rather weak bass, the sound is fairly detailed and crisp for such a low-cost speaker.    It doesn't take a lot of power to get good sound from these.

And if you turn the bass and treble controls up on your receiver, the sound becomes fuller.   Is there distortion when you do that?  Probably.  Is it noticeable?  Depends on your amplifier and your room acoustics.  I don't find it to be a problem.

These have a reputation for sounding good with a tube amplifier.   (See Distortion for a partial explanation of why.)

Unlike many small, lightweight speakers, the SP-30's don't have that flimsy, balsa-wood sound when you play music through them.  They're not exactly big Cerwin Vegas, but then again they don't sound like a kid's toy phonograph speaker, either.  The SP-30's can fill an average room with music;  in fact, you could probably listen to them from the next room. 

When I've tried that, they've always sounded quite OK to me.

Some people stuff the cabinets with polyester fill or even fiberglass insulation.  (Or, even better, get this stuff.)  Any of these will improve the bass response somewhat.  They will also attenuate unwanted resonance in the cabinet. 







Re-Capping


The SP-30 uses a single 2.2 µF capacitor in each crossover.  The capacitor is glued to the metal bracket on the tweeter assembly.   Being electrolytic, these capacitors can go bad.   And the failure doesn't have to be complete;  the speaker could still work, but the sound quality might be somewhat degraded. (Capacitance can drift over the years.)

Replace the electrolytics with a good polypropylene capacitor.   This will improve the sound.

Most people get this one for the SP-30's.   It's also 2.2 µF, but rated for more voltage.     These caps really do make a difference.

I would get four capacitors (two pair) in case you mess up a couple of them while trying to solder.  Probably you won't cause the polypropylene film to melt, but if for some reason you cut one of the leads too short, it's good to have an extra.  I say that because these speakers are kind of slow to take apart.  I'd rather have to buy an extra capacitor than have to remove and replace the back again.  (With a very short capacitor lead, you could probably melt the film while soldering.)

Be careful when you solder the leads.  The circuit board material looks to be a phenolic plastic or something else that melts easily.    It doesn't just look easy to melt... it melts.  Been there, done that.




There's the original capacitor (light blue).  It's glued to the side of that metal part, which forms the back of the tweeter.  My replacement job (not shown) was rather amateurish, because I didn't want to go the length of perfectly gluing it and then finding out the tweeter was bad anyway.  It's not really a big deal, though.  The new capacitor could just hang off into the empty space of the cabinet, as long as you solder the leads properly.




Blown Speakers


If you buy these from a yard sale or thrift store, you'll have no way of knowing if they were damaged... unless you give them a careful listen.  

Sure, you can test the ohms with a multimeter, but you won't know if there's partial damage that could degrade the sound.

Mine were crackling when songs were turned up, even moderately loud. 

I knew that wasn't supposed to happen.  It was a very scratchy-sounding kind of static.  You'd hear it on the loudest portions of the songs.  I thought the tweeters were damaged, but new capacitors seemed to fix the problem.  Good thing, because I wouldn't want to have to go in there and replace the tweeters after re-closing the backs once already.  There are a lot of screws to remove and re-install when you're done (see photo higher up on this page.)

These speakers are small enough that I'm sure a lot of people have blown them by playing too loud.  You're more likely to do this on a low-powered amplifier, actually, because distorted or clipped audio is worse for speakers than clear audio.  

And whatever you do, don't play recordings that were trashed by the Loudness War, because they will trash almost any speakers. 



Distortion

The SP-30's are very pleasant to listen to, without any fatigue.  That means third-order harmonic distortion is probably minimal.

According to this site, the SP-30's indeed have nearly all the distortion in the form of second harmonic.   That's very good.  It might be one reason these speakers pair well with a vacuum-tube amp.  

All audio equipment has some distortion, but you want that distortion to be even-order rather than odd-order.  If you had nothing but odd-order harmonics, you would get a square wave, which sounds nasty as I'm sure you know.  

I've found that a good recording on these will sound almost like the band is playing in your room, albeit at lower volume.  It's very clear, and that's with a transistor amp.   




Price / Value


These speakers are good enough that someone could easily hype them as the greatest thing in the hipster world, at least for this moment.   But seriously, don't pay too much for these speakers.  They are actually quite common.  Sansui made some speaker models that are rare today, but the SP-30's are not rare.  Being the smallest and cheapest of their speakers, they were bought by the largest number of people.

For a pair that hasn't been tested... five or six dollars.   This is the most I would pay at a yard sale or thrift store for these.  I've seen 'em for two or three dollars, the pair.   Buying untested speakers is like buying untested cameras... likely as not, there will be repairs needed.  There is a good chance that any given pair of these could have one or both with blown speaker elements.   Or, the electrolytic capacitors could be bad.  Or both.

Established sellers will charge more money than you'd pay in a yard sale, but any good seller will have tested them... and they'll usually know what to listen for during a test. 

And if you buy them online, realize that shipping is going to cost some money. 

For a pair that's been tested and is known to be good, figure on paying $25 to $60 here for the pair of speakers (depending on condition), plus the shipping cost.  That could be another $30 to $40.   There are pairs with higher asking prices (and sometimes selling prices), but I'd be wanting to see some extra feature such as their being already re-capped, or perhaps including the original boxes.

(Please help support my site by purchasing your SP-30's or anything else through this link.)




Conclusion


Sansui SP-30's are good little speakers.  They might not be the best ones ever made, but they're surprisingly clear and have low distortion if you don't overdrive them.  I would go ahead and get these speakers today without the slightest hesitation.  Even with the shipping cost, it's worth it if you get ones that are fully functional and tested. 

They're not real "bass kings", so don't expect to blast the loud stuff at high volume;  but the SP-30's are pleasant enough for easy-listening, polka, strings, vocal tracks, certain types of classical, some jazz, and country.  And of course, Gospel.

I hope you found this page useful, informative, or entertaining.  If so, please help me out by purchasing your stuff through these links.   Your help is greatly appreciated and is the only way I can keep this website going.

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