4 Ohm Load

Well said E.,B

You can try it, but don't get your hopes up. Receivers like your Pioneer were designed to work with very efficient 8 ohm speakers and with the right speaker they can sound quite good. I personally have not had good results trying to drive 4 ohm speakers with vintage receivers. 8 ohm speakers with Alnico magnets are no problem.

Excellent points have been made above. I would add a note of caution about the possibility of clipping the amp and damaging your tweeters as a result.

Stereophile measured your speakers as having a sensitivity of about 87db for 2.83 volts input at 1 meter. Given the 4 ohm nominal impedance, that corresponds to about 84db for 1 watt input, at 1 meter, which is quite low for use with a 27W amplifier.

That is of particular concern if you are listening to material with wide dynamic range, meaning a large difference in volume between the loudest peaks and soft passages. Well recorded classical symphonic music is a good example of that. That will cause you to turn up the volume control much higher than you would for compressed material having narrow dynamic range, resulting in power demand on peaks that greatly exceeds the amp's capability. The resulting distorted, clipped waveform will contain high frequency energy that is not present in the original material, which the speaker's crossover will route to the tweeter.

So I would suggest avoiding material that has wide dynamic range, and being careful to not turn up the volume to the point of audible distortion.

Regards,
-- Al

It is NOT the sensitivity that matters most.

The 'goodness' of a load is about phase angle.....How much does current lead or lag voltage? The moderate phase angle of this speaker is not a 'bad' load, though the impedance dip at 90hz to 2.83 ohms IS a redflag.

http://stereophile.com/images/archivesart/506VABFIG1.jpg

I had the SX-727 a LONG time ago and it was a warm one. Be careful and you should be OK.

Hi Magfan,

Your point about the importance of phase angle is certainly a good one. However, the specific issue I was addressing, the possibility that amplifier clipping caused by the relatively low sensitivity of the speaker coupled with the low power rating of the amp might in turn cause tweeter damage, I think would still be a concern even if the speaker were purely resistive, with 0 phase angle at all frequencies.

Best regards,
-- Al

Guys,
Some great response here. I keep learning. I'll keep it backed off. I've got an integrated amp that's adequte power for the VA's but I really like the tone of the old SX series receivers and my integrated has no tone controls. You get what you get.
I used to have the SX-1250 with JBL L300's and liked the ability to adjust the tone, especially at low litening levels. I suppose I could buy up into the SX-850 or higher and use just the pre amp section? Maybe there's a pre that's more modern that will do what I'm looking for and not cost thousands? I had said that I wouln't bore you with why I wanted to hear this old receiver at home in the first place, but that's why.
Thank you again for your feedback and the ohmformation.

Mike

Mike,

You're welcome. Keep in mind that boosting the bass, via tone controls or an equalizer, will dramatically increase the power demands on the amplifier, also increasing the likelihood that an underpowered amplifier will clip. Although if the boost is modest, and the volume levels are low, you'll probably be ok.

Best regards,
-- Al

I used to own a pair of JBL L300s and I'm still kicking myself for selling them. Now that speaker would work fine with your SX-636.

One of my first rigs was a 125 watt Pioneer receiver and a pair of JBL L65 Jubals.

I wonder if I would be impressed by this matchup today?

I realize a lot of people gravitate to systems like this.

My source was a Dual 1219 and a Grado cartridge.

I never regretted selling the gear and moving on to Ls3/5a's and Dynaco tube gear and LP12 table FR cartridge.

To my ears it was so much better than the Pioneer/JBL.

Perhaps it was just the source upgrade that made all the difference.