amplifierimpedanceimpedance-matchingpowerspeakers
I’m a little confused as to how I should be matching my amplifier and speaker in bridged mono mode. Let’s say I have the following,
• Amplifier Power: 100W at 8 ohms
• Amplifier Supported Output Impedance: 4-16 ohms
• Speakers Rating: 8 ohms
Firstly, when we are in bridged mono, it would theoretically give 400W. But what happens to the output impedance: Does it remain the same, halve or double – 16, 4 or 8 ohms?
Secondly, is it safe to use my 8 ohm speakers if I keep the power low?
You use different speakers in different systems and even different serial and parallel configurations; that's one of the reasons there are different impedance values. 8 Ohm speakers are the standard for home, while 4 ohm are usually found in car audio systems.
If a lower impedance loudspeaker generally has better dynamic range and can achieve louder volumes, why do we still see 6, 8 or even 16 ohm speakers? Shouldn't we be "progressing" toward more efficient speakers with lower impedance?
While yes, the benefit of 4 ohm speakers is that the increased current means they have a wider dynamic range, they will be harder on the amplifier (if the amp is made for 8 ohm) and at higher volumes they will have larger THD (total harmonic distortion.) Essentially the output voltage will be unstable during high power application as the Amp will struggle to supply enough current to drive the load.
Using a 4 ohm speaker on a generic home amplifier that is made for an 8 ohm speaker will draw twice as much power and can cause the amplifier to go into protect mode or even overheat and break.
why do we still see 6, 8 or even 16 ohm speakers?
Different serial and parallel configurations are used to change the load on an amplifier. For example, you can have two 4 ohm speakers in series so that the load will be 8 ohms. Or (common in custom car systems,) you may have two 4 ohm speakers connected in parallel so the load on the amplifier is only 2 ohms, thus doubling the current.
Or in this case, four 8 ohm speakers are connected in series parallel so that the total impedance is only 8 ohms.
Are higher impedance speakers merely a product of backward-compatibility?
No they have their place, from allowing different speaker configurations, or less wear and tear on amplifiers to improved sound quality.
Using speaker with higher than minimum impedance may improve quality as the Amp will generate more stable voltage and current. Hence the THD will remain lower at higher impedance while the maximum power output by the Amp will be reduced due to higher load impedance.
Loudspeakers have impedances of 8 ohms, 6 ohms or 4 ohms (those are "nominal" or approximate values, because the impedance of a speaker changes all the time with the different frequencies of music
They are also referred to as at rest values, and if you connect a ohm meter to the speaker it should read 4 or 8 etc. ohms. Then if you gently move the speaker that reading will change. If you measure a speaker and it shows a different value than what it is supposed to then it may be defective of blown or at least slightly damaged.
None of the options is good. The speaker produces a sound pressure level for a certain wattage inputted and this is the criteria you need to look at. Some speakers are more effective than others and this effectiveness is largely determined by their enclosure. Luckily, for any given size and shape of speaker the enclosure is roughly constant.
Decide what SPL you need and look at speaker specs to shortlist a handful then design your enclosure to suit the shortlisted items then do comparative studies. You are obviously looking for bandwidth, loudness and distortion as the key ingredients of the selected speaker. Choose also, the speaker that is capable of withstanding the power output that can be thrown at it. Choose an amplifier that won't melt down ie has protection built in.
Best Answer
For most (if not all) audio power amplifiers the output impedance is a fraction of an ohm and the speaker might be 4 ohms. The point I'm trying to make is that you don't match a speaker impedance to the audio amplifiers output impedance because the audio amplifier's output impedance is (usually if not always) much, much smaller than the impedance of the load.
So, say the output impedance is 0.1 ohms (as per my earlier words), in bridged mode this would approximately double to 0.2 ohms but, as I previously said this is unrelated to the speaker impedance. The reason why amplifier manufacturers quote a speaker load range is to prevent overload and out-of-bounds distortion. Matching is not involved.
Yes it is. Reason: think about an 8 ohm speaker with a centre tap winding exactly halfway along the speaker coil. Now imagine what AC voltage you would see there when used in a balanced bridge. If you can't imagine it I'll tell you - it is 0 V AC and therefore two 4 ohm speakers with one on one amp and the other on the other amp is the same as an 8 ohm bridged amp.