usbyte
Member
Can someone explain "impedance dips at higher frequencies". Does it mean that the impedance falls as you play louder or impedance falls if your music track contains high frequency.
Martin Logan speaker impedance
- Thread starter usbyte
- Start date
Help Support MartinLogan Audio Owners Forum:
The later.
As the sound being played increases in frequency, the amp sees lower and lower impedance.
This means the amp will supply higher and higher current into the speaker load.
Many amps can't do that well at high volume.
Which is why playing music with strong high frequency content at loud volumes is a problem for amps not designed for these low impedance loads.
As the sound being played increases in frequency, the amp sees lower and lower impedance.
This means the amp will supply higher and higher current into the speaker load.
Many amps can't do that well at high volume.
Which is why playing music with strong high frequency content at loud volumes is a problem for amps not designed for these low impedance loads.
To the tune of 1 to 2 ohms at 20,000 hz.! This can wreak havoc on a lesser quality amp.
donberry
Active member
I am by no means an expert and am only quoting what I read in Stereophile while checking out a review of the SL3.
"Though the impedance drops to 1.5 ohms at 20kHz, there isn't much musical energy present up there, meaning that the amplifier will not be taxed too much. In addition, as is typical, the lowest impedance magnitude coincides with a phase angle of 0 degrees. "
"However, there are three problem areas at lower frequencies, both where the music has a lot of energy and where the SL3 features a combination of low impedance and high phase angle, something that asks a lot of an amplifier. At 50Hz, 4.5 ohms impedance is coupled with a capacitive phase angle of -47 degrees; at 1kHz, a magnitude of 5 ohms coincides with a phase angle of -42 degrees; while at 8.2kHz, a magnitude of 3.8 ohms combines with a phase angle of -57 degrees. In each case, the amplifier's output stage will be maximally stressed. "
so it seems to me that the trouble areas are 50hz, 1khz and 8.2khz and it is the phase angle at those freq. that are troublesome for amps.
"Though the impedance drops to 1.5 ohms at 20kHz, there isn't much musical energy present up there, meaning that the amplifier will not be taxed too much. In addition, as is typical, the lowest impedance magnitude coincides with a phase angle of 0 degrees. "
"However, there are three problem areas at lower frequencies, both where the music has a lot of energy and where the SL3 features a combination of low impedance and high phase angle, something that asks a lot of an amplifier. At 50Hz, 4.5 ohms impedance is coupled with a capacitive phase angle of -47 degrees; at 1kHz, a magnitude of 5 ohms coincides with a phase angle of -42 degrees; while at 8.2kHz, a magnitude of 3.8 ohms combines with a phase angle of -57 degrees. In each case, the amplifier's output stage will be maximally stressed. "
so it seems to me that the trouble areas are 50hz, 1khz and 8.2khz and it is the phase angle at those freq. that are troublesome for amps.
usbyte
Member
thanks for the clarification.
donberry
Active member
actually I found it interesting and did not really know what phase angle was so it gave me a chance to learn something myself.....now I understand why the phase angle is so important
gmartan
Well-known member
I certainly haven't come across any modern amps, other than OTL amps, that should have any problem with driving the load presented by a ML speaker. If your amp has output transformers expect a high frequency roll-off and loss of air since the impedence can't be matched at the higher frequencies.
