I'm curious what people are doing as far as subwoofers and low pass filters and high pass filters with vintage gear.
I'm using an SX-750 with some Pioneer bookshelf speakers and a subwoofer. I'm using the line level inputs on the sub and using the crossover knob on the subwoofer itself which is no big deal. The sub is crossed at about 60hz. The thing that bothers me most is that I'm running my little bookshelf speakers full range 20hz - 20khz. I'm using them near field so it's not taking much power to get them going, so I'm not too worried about them trying to play the frequencies below 60hz or so. For the first couple weeks I used these bookshelf speakers with the grilles off so I could watch the cone excursion and to my surprise I never saw them moving all that much even on the bassiest music. I'm just curious as to what people are doing here in this regard.
My speakers have a sensitivity of 87db at 1 watt at 1 meter. Using a digital Radio Shack SPL meter I never see myself listening at higher than 90db, even on peaks. I'm always listening somewhere in the 70-85db range. So looking at the math it seems that I'm never giving these speakers more than 2 watts each. Most of the time, especially night time listening when I listen at under 80db, if the math is right they aren't even getting a full watt each. This seems crazy low and hard to believe, but if this is true, then these speakers should have no problems being run full range.
If they are really 87db at 1 watt at 1 meter then here is the math, +3db = double the power.
87db @ 1 watt
90db @ 2 watts
93db @ 4 watts
96db @ 8 watts
99db @ 16 watts
102db @ 32 watts
105db @ 64 watts
Is anybody else running small(ish) speakers full range on their vintage amp? If so, have any comments or concerns?
I'm using infinity entra pointe 5's (small guys) on my sony str-6120 with a separate powered woofer. They claim a frequency response between 50 and 20,000 Hz. That being said, a lot of music has frequencies down to/below 20 Hz in the subsonic region. I find that when I try to feed a lot of bass to the small speakers, they'll keep taking power until the cones bottom out (which is reeealy bad for them). If you take a bit of the load off their bass, you can A) turn your music up louder and B) get much better bass reproduction. Remember that the stated roll-off frequency is the corner frequency, defined as the point at which the response is -3dB (3 dB down) from the average response. This means that the point at which you start losing the response is likely many Hz higher, possibly as high as 500Hz for a 1st order system, but likely closer to 100-150 Hz for more sophisticated speakers (based on box volume if not ported & x-over design). If you have access to their response curves, you should ideally try to set your woofer x-over frequency so that the combined curve is a flat as possible (though I personally like a little sub&ultra sonic boost). I have mine set at 100 Hz, for comparison.
Regarding filters, I don't use them in my system. The bookshelf speakers have a nice roll off and the woofer has a tuneable cutoff LPF that nicely picks up the slack. I just adjust the gain on the woofer to get the desired response and take advantage of the natural roll off of the bookshelfs to get a nice effect.
Considering that your speakers are not played very loudly, it is not at all surprising to hear how little power you use with them. Rule of thumb, about 1 watt will give nice conversation level music, 2 watts will be loud enough to be distracting, 4 watts will overpower conversations within 10 feet, 20 watts will shake the windows of a studio apartment, and 60 watts will make a normal suburban home very loud inside throughout and probably loud outside as well. Anything more and the cops are coming/ you will need a bouncer for your night club. Unless you like a lot of bass, in which case quadruple all those numbers to feed your hungry subwoofer(s).
I run somewhat inefficient speakers on my main system (sx-1980, mcintosh XR-250's), but even at 10w/per, I am overpowering every other human or mechanical noise in the house. Including my terrible attempts to sing along haha. Lucky me.
You might still think those are all small numbers. They are. Marketing people long ago realized that people want more power and BIGGER numbers sell more units. There is a whole bevy of marketing math lies that are told to inflate specs. If you deconstruct the math going into a car power amplifier that claims "1000W", you might find that they are actually more like 20 rms continuous into 8 ohms after you get past all the smoke and mirrors. Don't get me wrong, 20 W will shake your guts when it's all bass in a small car, but it's a far far cry from 1kW.