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 Post subject: Sansui SP-2000 Speakers
PostPosted: Dec Wed 14, 2011 9:44 am 
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Location: Albuquerque, NM 87123
I picked up a pair of Sansui speakers in fair shape. I didn't like the original speaker connections so I changed them to 5 way binding posts, since the holes were a convenient 3/4 inch apart. While inside I noticed that the woofer is directly connected to the inputs, and also has a 22uf NP cap across it. No inductor in series; so, this capacitor is across the input.

Is this normal cross-over design? I've seen many speaker systems that had the woofer directly across the inputs, or in series with an inductor, but what would be the value (or intelligence) or having a 22uf cap across the audio source? Isn't this just an inefficient waste of audio power?

Edit: On closer inspection it appears that someone has been inside; the inductors for the woofers had been bypassed. I put the inductors in series again and all is well. The sound is not the best I've heard, but it isn't bad.


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 Post subject: Re: Sansui SP-2000 Speakers
PostPosted: Dec Wed 14, 2011 2:18 pm 
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Location: Warner Robins, GA
Those speakers should sound much better when you replace the capacitors and resistors used in the crossover. Use film capacitors and non-inductive resistors if possible.

Seems like someone may have bypassed the inductors to make up for the reduced audio quality of the failing crossover caps.

I have a couple pairs of late 60's Fisher speakers that my dad uses in his shop. I replaced the crossover caps along with the resistors in the crossover and the sound is much improved.

I have often wondered if the designers of crossovers took into account the use of regular resistors when designing the crossovers given wirewound resistors do have some inducrtance.


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 Post subject: Re: Sansui SP-2000 Speakers
PostPosted: Dec Wed 14, 2011 6:21 pm 
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Joined: Sep Thu 23, 2010 6:37 am
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Location: Powell River BC Canada
Resistors are sometimes found, but not for their inductance, A tweeter can be just too
loud. A resistor can 'shelve' it, that is just reduce its output, but not the frequency
at which starts take over from the squawker or woofer.

Tweeters have different efficiencies, but the good ones had big magnets, which allowed
the work on the cone,dome, and horn to not worry about the sound pressure but
concentrate on the smoothness of response, But sometime, to some people, they
sounded too bright.

If you ever wanted to use resistors with a tweeter, you could buy a T pad control.

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de
VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
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 Post subject: Re: Sansui SP-2000 Speakers
PostPosted: Dec Wed 14, 2011 6:54 pm 
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Joined: Aug Tue 24, 2010 8:56 pm
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Location: Florida
I've seen many speakers where the woofer was wired directly to the inputs, and the crossover was wired in series to the mids/tweeters. I have no idea what the cap was for; there is no line of thinking that would support placing it across the input.

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 Post subject: Re: Sansui SP-2000 Speakers
PostPosted: Dec Wed 14, 2011 8:08 pm 
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Location: Baltimore, MD, USA
tubes4life wrote:
I've seen many speakers where the woofer was wired directly to the inputs, and the crossover was wired in series to the mids/tweeters. I have no idea what the cap was for; there is no line of thinking that would support placing it across the input.


I think that the "better" speakers used inductors to limit the high frequencies to the woofer and non polarized capacitors to the tweeters and mid-range speakers. I have had some "inexpensive" speakers that did have very limited "cross-over" components.

As for the capacitor across the input, I suspect it was done by someone that did not understand what to do, possible a do-it-yourselfer...

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 Post subject: Re: Sansui SP-2000 Speakers
PostPosted: Dec Wed 14, 2011 8:17 pm 
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Joined: Aug Tue 24, 2010 8:56 pm
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Location: Florida
Don Cavey wrote:
tubes4life wrote:
I've seen many speakers where the woofer was wired directly to the inputs, and the crossover was wired in series to the mids/tweeters. I have no idea what the cap was for; there is no line of thinking that would support placing it across the input.


I think that the "better" speakers used inductors to limit the high frequencies to the woofer and non polarized capacitors to the tweeters and mid-range speakers. I have had some "inexpensive" speakers that did have very limited "cross-over" components.

As for the capacitor across the input, I suspect it was done by someone that did not understand what to do, possible a do-it-yourselfer...


I understand about the usage of inductors and proper crossover components, but I am baffled as to why anyone would bridge the woofer; what would that accomplish?

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 Post subject: Re: Sansui SP-2000 Speakers
PostPosted: Dec Wed 14, 2011 9:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12485
Location: Albuquerque, NM 87123
I was comparing the Sansuis to a pair of Snell type K, which are very nice speakers.

On my next order to MCM I will get some audio grade caps. I want to refinish the speaker cabinets, but I think the biggest problem I will have is getting the dust off the wood grilles.


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 Post subject: Re: Sansui SP-2000 Speakers
PostPosted: Dec Wed 14, 2011 10:49 pm 
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Joined: Sep Thu 23, 2010 6:37 am
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Location: Powell River BC Canada
I wouild buzz all the drivers out with an audio generator and an amplifier to check for
rubs or frapps before doing too much.

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VE7ASO VE7ZSO
Amateur Radio Literacy Club. May we help you read better.
Steve Dow
ve7aso@rac.ca


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 Post subject: Re: Sansui SP-2000 Speakers
PostPosted: Dec Thu 15, 2011 6:34 am 
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Joined: Aug Tue 24, 2010 8:56 pm
Posts: 3512
Location: Florida
radiotechnician wrote:
I wouild buzz all the drivers out with an audio generator and an amplifier to check for
rubs or frapps before doing too much.


On the woofers, you can do that with just your fingers by moving the cone in and out along the perimeter of the dust cover; you'll feel it if there's any binding.

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