Driving JBL L100 speakers

[Heath Hamby]

I have a Pioneer sx-850 receiver. Just bought some JBl L100 Century speakers. Wondering if the receiver is enough to push these speakers to optimal performance? I have a chance to get an sx 1050. Wondering if it's worth the money?

 

[Chris Brown]

For what it's worth, JBL themselves rates this speaker at "50 Watts continuous program", but at the same time says that "a quality amplifier delivering up to 150 Watts RMS per channel will provide optimum performance". The SX-850 is rated at 65WPC at 8ohms.

The SX-850 would probably be fine, but if it were me, I would be somewhat uncomfortable powering them with less than 100wpc. Your listening habits will be what determines if it's "enough". At what volume level do you want to be able to maintain "optimum performance"? What sort of music do you listen to? Do you use EQ or tone controls?

I power my JBLs with between 240-700wpc, but the L100 doesn't have quite as much power handling as many of the "newer" vintage JBLs. I use a lot of power because I like to listen loud, and often while listening to bass-heavy content which requires the most power.

The SX-1050, at 120wpc, would be better in terms of power. Those things are a beast, with a huge toroidal transformer. My friend used one at one point to power two pairs of Cerwin-Vega D-9s simultaneously at party volumes. That is pretty remarkable, considering that the combined load would dip down to 2ohms or so, and it was definitely putting out more than 120wpc. The faceplate lights would actually dim during strong bass, probably soft-clipping, but it didn't stop the receiver from chugging along like a freight train.

Another route you might consider is to use SX-850 for now, and eventually get an external power amplifier in the 200wpc+ range. At that point you could simply use the SX-850 as a preamp (using pre-out jacks on receiver to feed the external power amplifier). That would probably be the most cost-effective, since the SX-850 and SX-1050 are already very similar in terms of features, the SX-1050 simply has more power. You can find a lot of nice external power amplifiers for a lot cheaper than what an SX-1050 would usually cost while also delivering more power.

I can't help but recall a scenario from about a decade ago where a friend thought that his SX-780 was "enough", and ended up burning up the receiver from pushing it too hard. The 850 should do better than the 780 in that regard, but still... always better to have too much power than not enough.

 

[WaynerN]

When a speaker starts to show signs of strain, regardless of amplifier size, that is your maximum level. A larger amp may help with increasing the point of the strain, because (as always) the speaker and the amplifier are a couple and all amps have a particular behavior reacting to different impedance loads. Damping factor of an amp can also play a role.

The other problem is that the L100s have a simple 6db per octave slope on the mid and HF drivers and the mid is not contained on the top end, so it will respond to some high frequency stuff at the same time the tweeter is, which can produce some of the harshness.

I modded my L100s by bi-amping them, by installing a another set of speaker terminals, loading just the woofer on one set, the midrange and tweeter on the other set. The woofer was driven by a Marantz 240 amp, the mid and tweeter were driven by a Dynaco Stereo 70 tube amp, both being fed via simple "Y" cables from my Marantz 3300 preamp. The tube amp had slightly less output ratio then the SS amp, which tamed some of the harshness and the tubes also brought some mellowness to the whole affair.