I would like someone to explain how speaker impendence affects the amplifier. I know amplifier have a impedence rating and you're not supposed to go below that because it will draw too much current from the transistor.
How is that speaker impendence measured though? For example, I have a two way speaker system here whose impedence dips to 3.1 ohm. If I build the XO the way I want to it will dip down to 2.1 ohm. We all know a speaker doesn't just play one tone. It plays a spectrum of music at the same time. So, if it is playing a bass tone at 12 ohm and a high frequency tone at 3.1 tone at the same time, will it place an average impendence on the amplifier of 9 ohm? This is what I do not understand and I would like someone to explain to me.
I am an electrical engineer (slash manufacturing engineer) but I honestly do not really understand class D amplifiers. That is half the reason I got into this hobby. I like things I don't understand.
Thank you in advance for your response.
How is that speaker impendence measured though? For example, I have a two way speaker system here whose impedence dips to 3.1 ohm. If I build the XO the way I want to it will dip down to 2.1 ohm. We all know a speaker doesn't just play one tone. It plays a spectrum of music at the same time. So, if it is playing a bass tone at 12 ohm and a high frequency tone at 3.1 tone at the same time, will it place an average impendence on the amplifier of 9 ohm? This is what I do not understand and I would like someone to explain to me.
I am an electrical engineer (slash manufacturing engineer) but I honestly do not really understand class D amplifiers. That is half the reason I got into this hobby. I like things I don't understand.
Thank you in advance for your response.
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The impedance rating of an amplifier is based on the nominal impedance of a loudspeaker.
Look at the impedance plot for a two-way speaker shown below.
The nominal impedance can be taken as the value which occurs in the valley between the bass resonance peak(s) and the impedance peak at the crossover frequency. This value is often taken to be the impedance at 400 Hz. In the above plot, the nominal impedance would be around 6 ohm.
The IEC method of specifying nominal loudspeaker impedance is set such that minimum impedance must not fall below 80% of nominal, so for an 8 ohm speaker this would be 6.4 ohms minimum, and for 4 ohms would be 3.2 ohms.
Look at the impedance plot for a two-way speaker shown below.
The nominal impedance can be taken as the value which occurs in the valley between the bass resonance peak(s) and the impedance peak at the crossover frequency. This value is often taken to be the impedance at 400 Hz. In the above plot, the nominal impedance would be around 6 ohm.
The IEC method of specifying nominal loudspeaker impedance is set such that minimum impedance must not fall below 80% of nominal, so for an 8 ohm speaker this would be 6.4 ohms minimum, and for 4 ohms would be 3.2 ohms.
Many amplifiers cannot perform very well with even 4 ohm loads.
Lower speaker impedance than that would be likely cause real problems for the amplifier.
Lower speaker impedance than that would be likely cause real problems for the amplifier.
If I understand it correctly, some amplifiers have more trouble than others with driving varying impedance loads especially when the phase of the crossover has a steep angle. I have a tube amp that drastically changes my speaker's frequency response by giving more output as the impedance is higher and less output as the impedance nears 4 ohms even when I'm using the 4 ohm tap. Another point is that some older class D amps had trouble with load dependency, which would change the frequency response depending on the nature of the crossover's impedance response. Newer Class D amps (Hypex, Purifi) don't seem to have these problems and I have seen them perform well on speakers that go as low as 2.7 ohms in certain places.
This is definitely one of the biggest differences I've heard in all the amplifier/speaker combo's I've ever tried/tested - namely the ability to work with low impedance.
Getting my hands on a much stronger amplifier and trying it out on speakers like Dynaudio, B&W and JMlab, really showed a rather big difference in especially bass, where quite a few "typical" HIFI amplifiers simply can't pull it off. And especially the classic approach of weight and wattage, actually does not say much - which I learned the hard way - carrying around heavy gear and trying out all the combinations I could.
The first time I really experienced the actual difference in amplifiers, was with the Vincent SAV P200. It's a 45kg heavy 6 channel beast, which is nice and all, but have very low control over speakers - I found out. Tried to use it to drive my DIY subwoofers with a LAT500 driver, and the cone easily flapped and bottomed out. Then I tried a Groundsound HPA2K - which just grapped that cone and kept it in an iron fist. Much deeper and louder bass, which ZERO cone flapping. Of course, the cone could bottom out, but that's just because all drivers do have X-max to deal with eventually.
After that, I just kept to that brand of amplifiers and never thought of low impedance again. Every time, a friend thinks they might want to upgrade, I just bring mine, to show them how bass sounds, when the driver is controlled like a dominatrix 😆
There's always the fact that people often really like their speakers, and then EQ comes into play + bi-amping, so they can control that woofer and keep whatever they want for the midrange and tweeter, which is mostly possible because most of the trouble with low impedance, comes from filtering the woofer. Even small bookshelfs can rip most amplifiers a pair 😈
Running fully active, definitely solves a lot of this, but just introduces new "fun". Choose your poison, I guess 🤣
Love it here though. Lots of competent power for each driver, no complicated passive network to learn how to build, and DSP finesse to filter it all 😊 But again, complexity, size and price.... choose wisely 🤓
I believe the rather new speaker from MOFI, the Sourcepoint 888, is a great example of a passive speaker that present a very nice impedance for any amplifier. It is also very smooth in frequency response and power response, making it an overall very easy speaker to work with, both regarding placement, EQ and choice of gear that you combine it with.
Getting my hands on a much stronger amplifier and trying it out on speakers like Dynaudio, B&W and JMlab, really showed a rather big difference in especially bass, where quite a few "typical" HIFI amplifiers simply can't pull it off. And especially the classic approach of weight and wattage, actually does not say much - which I learned the hard way - carrying around heavy gear and trying out all the combinations I could.
The first time I really experienced the actual difference in amplifiers, was with the Vincent SAV P200. It's a 45kg heavy 6 channel beast, which is nice and all, but have very low control over speakers - I found out. Tried to use it to drive my DIY subwoofers with a LAT500 driver, and the cone easily flapped and bottomed out. Then I tried a Groundsound HPA2K - which just grapped that cone and kept it in an iron fist. Much deeper and louder bass, which ZERO cone flapping. Of course, the cone could bottom out, but that's just because all drivers do have X-max to deal with eventually.
After that, I just kept to that brand of amplifiers and never thought of low impedance again. Every time, a friend thinks they might want to upgrade, I just bring mine, to show them how bass sounds, when the driver is controlled like a dominatrix 😆
There's always the fact that people often really like their speakers, and then EQ comes into play + bi-amping, so they can control that woofer and keep whatever they want for the midrange and tweeter, which is mostly possible because most of the trouble with low impedance, comes from filtering the woofer. Even small bookshelfs can rip most amplifiers a pair 😈
Running fully active, definitely solves a lot of this, but just introduces new "fun". Choose your poison, I guess 🤣
Love it here though. Lots of competent power for each driver, no complicated passive network to learn how to build, and DSP finesse to filter it all 😊 But again, complexity, size and price.... choose wisely 🤓
I believe the rather new speaker from MOFI, the Sourcepoint 888, is a great example of a passive speaker that present a very nice impedance for any amplifier. It is also very smooth in frequency response and power response, making it an overall very easy speaker to work with, both regarding placement, EQ and choice of gear that you combine it with.
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