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How do most small bookshelf speakers and large floorstanding speakers have the same impedance and sensetivities? shouldn't a 4 way floorstander have less impedance than a 2 way bookshelf?
 

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No.


The impedances of the individual drivers vary, and they are all connected in a complex of crossover networks that also have a lot to do with the overall speaker system impedance.


There is no way to make any general statements of that kind because every design is unique.


The number given on a spec sheet as the "speaker impedance" is only a very general approximation anyway; it tells you very little.


Every speaker system has a different impedance at every audio frequency, and the only way to know this in detail is to view a GRAPH of the speaker impedance VS frequency for EACH speaker system.


Look at the Stereophile website and check out the "Measurements" section of a speaker review from a past issue. They always give a graph of Impedance VS frequency for each speaker reviewed, as well as other useful graphs and measurements.


A typical "8 ohm" speaker system may have an impedance of 5 ohms at some frequencies and 20 ohms at some frequencies.


The drivers used in a 4-way design might be chosen because they have somewhat higher impedances, so that the overall speaker system impedance does not end up being unacceptably low.


The driver and crossover design possibilities are infinite, and so the graph of every speaker system's impedance will also be unique.
 

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Quote:
Originally Posted by ryanenos  /t/1521495/impedance-of-bookshelf-vs-floorstanding-question#post_24453711


shouldn't a 4 way floorstander have less impedance than a 2 way bookshelf?
No. The number of drivers has no bearing on the speaker impedance.
 

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Quote:
Originally Posted by ryanenos  /t/1521495/impedance-of-bookshelf-vs-floorstanding-question/0_50#post_24453711


How do most small bookshelf speakers and large floorstanding speakers have the same impedance and sensetivities? shouldn't a 4 way floorstander have less impedance than a 2 way bookshelf?
No. Let's say for example we have a 2 way speaker with a 1kHz xover and each driver is a nominally 8R unit. The xover for the tweeter works to roll off the signals below 1kHz by increasing impedance in series with the driver below 1kHz. The woofer xover does similarly, but it increases impedance above 1kHz. These two sections are connected in parallel so that the higher impedance of the other section barely makes any difference. At 100Hz, the amplifier sees the 8R of the woofer in parallel with the crossover imedance as well as that 8R of the tweeter. At 100Hz the HF section in total my be 50R which in parallel is about 6.9R still close enough to 8R. It doesn't matter how many ways/sections you add, the results will be roughly the same, but also depend if the designer cares what the final impedance curve for the speaker is like. As another poster mentions, the typical impedance curve of a speaker is anything but flat.
 
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