Perhaps someone can give some insight into amp-speaker compatibility? I'm considering auditioning a pair of speakers shortly, but if my current amp will not be able to drive them well then I will not bother. A seller is offering a used pair of Polk LSi9 bookshelf speakers (however, I'd audition a new pair in an audio store). The speaker's specs are: Nominal Impedance 4 ohms Recommended Amplifier Power 20 - 200 w/channel Efficiency 88 dB
My amp is a Yamaha A-700 100W integrated (circa 1985). I'n general, I'm shopping for speakers to use in a 2 speaker system. I do anticipate upgrading my system over the course of the next year, but am looking for a pair of speakers that will serve for the next several months/year or so. If the bass on this (or any other bookshelf speaker pair I aquire) is shy, I could add a sub eventually.
The A700 was a bit "iffy" at four Ohms. It depends on the stability of the load. Check for reviews of the speaker and look in the measurements for how much impedance swing there is away from the nominal four Ohm load. If the impedance has dramatic variations from four Ohms, other than the two peaks in impedance which are common to any ported speaker system in the bass (system resonance) region, you might want to consider letting these speakers pass. Look also for the "electrical phase angle" of the speaker. The phase angle of the speaker system indicates how difficult the speaker will be to drive just as much as impedance does. Anything in the way of a convoluted phase angle should be avoided. Most speakers have a moderate amount of phase angle shift and a reasonable amount of either impedance swing or angle shift can usually be accepted. If the speaker system remains at close to a four Ohm load or moves very gradually from low to high impedance, with the exception of the two peaks already noted, the speaker will probably work with the A700. If the speakers have minimal phase angle shifts, it will work with the amp. If the speaker dips much beneath four Ohms to any extent, pass it by.
As a genearl rule, Polks are fairly simple loads meant to work with mid-fi equipment such as your Yamaha. They shouldn't require a brute force amp; but check the measurements before buying any four Ohm speaker. Impedance is stated as a "nominal" rating and can be of little use in determining the "reactance" of a speaker. If the speaker looks very even and has no sudden shifts in load (a "benign" load), other than the two peaks, you can usually get by with a four Ohm load.
Check the reviews for measurements or call Polk and ask.
"As a genearl rule, Polks are fairly simple loads meant to work with mid-fi equipment such as your Yamaha. They shouldn't require a brute force amp; but check the measurements before buying any four Ohm speaker. Impedance is stated as a "nominal" rating and can be of little use in determining the "reactance" of a speaker. If the speaker looks very even and has no sudden shifts in load (a "benign" load), other than the two peaks, you can usually get by with a four Ohm load.
Check the reviews for measurements or call Polk and ask. "
The LSi series of Polk's speakers are much different than there normal speakers. They do require good amplification much more any other of there speaker lines. But then again I think you would be able to run them off that amp, though in the future they would want more power.
Thanks for the detailed information Jan. I spoke with a Polk technician and was told that the LSi9 can run as low as 3.3 Ohms and as high as 5.6-6.2 Ohms. He claims to have sold the Yamaha A-700 int amp in the 80's and is familiar with it: he said it wouldn't have a problem driving the LSi9 speaker. He also said I needn't be concerned with the "electrical phase angle" as an issue in my amp driving the speakers. He sounded like he knew what he was talking about, he even gave me some particulars about my Yamaha amp. He said the Yamaha has a fairly burly power supply and it would only run into problems if I tried running two speakers pairs at the same time. Can I take that as an informed reply (it sounds like it to me)?
Paul S., What would more power give me out of the speakers? If the Yamaha is underpowered for the speakers, how would that effect the sound?
In general, when checking out a pair of used speakers, what if anything do you inspect? Cosmetic issues aside, do you merely pop the grill off and have a look at the drivers and surrounds making certain everything looks intact? If the drivers have ssutained some damage, i.e. from clipping etc, how would this manifest either visually or in listening to them?
I assume my upgrade path will at some point turn to my amp. The T-amps reviews have excited me ( Sonic Impact v.1 & v.2 for example) and on the surface seem to be a fine match for someone at my level in audio to experiment with. A consensus has formed from many listeners pleased and surprised with the sound, and virtually everyone gives these the highest recommendation...as a budget amp. Does a speaker with specs like the Polk LSi9 represent a design that would seriously challenge one of the budget T-amps?
If down the road I got one of the budget T-amps (ex. Sonic Impact or one of the Panasonic T-class amps) and used that to drive a pair of speakers, would the Yamaha A-700 int. amp be suitable to drive a budget subwoofer?