Output Impedance and Speaker Impedance
ubbcbus OPNot if overdamped by an amp, you can if they are very underdamped, as it’s travel is increased uncontrollably and the speaker cone "could" hit it’s end stops both inwards and outwards, especially with vinyl at warp frequency. Too much of this can damage the speaker. Ever seen an underdamped bass driver? it wobbles around like jelly when doing bass Cheers George |
Before you read the rest ubbcbus , the Aerial Acoustics 5T is not an overdamped design, it’s normal. A loudspeaker can’t be overdamped electrically, this is why some of the best amps for bass are from class-D, that have output impedances in the milli-ohms, damping factors of 10,000 or more and why they are great for subwoofers. However you can have too much damping if the electrical damping is combined with too much mechanical damping in "over damped" enclosure design. A typical example was the Linn Isobaric speaker which had very lean almost no bass with big Krells of the era, who would have thought a Krell with no bass!!!! I actually heard a Naim amp with very mediocre damping factor sound better than the Krell into the bass of the Linn Isobarics. BTW: this overdamped speaker with underdamped amp, was a great marketing strategy thought up by Linn/Naim at the time, you had to get both their amps and speakers, one did sound right without the other in A/B’s at shops. Cheers George |
I connected the 5T’s back to the 7900, but connected them to the 8 ohm outputs. It really opened up the lower frequencies and I didn’t notice any loss in the mid or high frequencies.What’s happening using the 8ohm tap is that in the bass there is little "damping factor" from the amp to control the speakers movement, so the cone excursion is not halted, but over travels slightly on the out and the inward movement, in other-words it’s not as tightly control as Aerial would like it to be. Stereophile Aerial 5T 6 ohms in just two regions—between 29 and 54Hz and between 110 and 310Hz—and a minimum value of 4.28 ohms at 160Hz. The electrical phase angle (fig.1, dotted trace) is occasionally extreme, and the combination of 6 ohms and –38° at 108 ohms means a good 4 ohm–rated amplifier would be the best match for this speaker. But hey! you "could" have an "over damped" room for bass, or a "lean" source in the bass, so an under-damped speakers bass could be ok for you, not ideal for detail retrieval but fine for tonality.. Cheers George |
