Hello there,
I am finally building my own soundsystem. I have already decided on the subwoofer design. However, when designing the tops and selecting drivers I came across a problem: There are 4 and 8 Ohm versions of one driver model and now I have to decide. I did research but couldn't find what I was looking for. There are tons of comparisons between the 2 "technologies" in general but I have not been able to find a comparison between 4 and 8 Ohm drivers of the same model. Can someone elaborate the pros and cons of each? Thanks in advance!
Blessings,
Domme
I am finally building my own soundsystem. I have already decided on the subwoofer design. However, when designing the tops and selecting drivers I came across a problem: There are 4 and 8 Ohm versions of one driver model and now I have to decide. I did research but couldn't find what I was looking for. There are tons of comparisons between the 2 "technologies" in general but I have not been able to find a comparison between 4 and 8 Ohm drivers of the same model. Can someone elaborate the pros and cons of each? Thanks in advance!
Blessings,
Domme
Welcome to the forum!
You won't have an absolutely "equivalent" driver if you simply change the resistance of the voice coil.
It has something to do with BL product, moving mass etc. - all a bit above my pay grade!
(BL: The product of magnet field strength in the voice coil gap and the length of wire in the magnetic field.)
Hopefully the loudspeaker designers will now chip in and educate both of us! 😀
You can make a speaker with a different nominal impedance and still aim for similar behaviour. What should probably interest you is your amplifier/load situation.
edit: Great minds........😉
Greets!
The basics:
Low ohms Vs high ohms = draws more current = increased inductance [Le] = increased VC heating = driver thermal power distortion = rolls off ~flat HF BW
ergo:
High ohms Vs low ohms = decreased inductance [Le] = decreased VC heating = less driver thermal power distortion = more flat HF BW
Historically, drivers might have hundreds of ohms [FWIW my 1960 AM tube radio clock's is listed as 600 ohms!] to keep power requirements next to nothing since power was incredibly expensive, though as design/materials/manufacturing knowledge increased it has slowly changed to the exact opposite plus the HF response can be adjusted to make them virtually the same, making choosing almost moot unless a low power amp and/or a very wide bandwidth ['full-range'] is required.
Greets!
The basics:
Low ohms Vs high ohms = draws more current = increased inductance [Le] = increased VC heating = driver thermal power distortion = rolls off ~flat HF BW
ergo:
High ohms Vs low ohms = decreased inductance [Le] = decreased VC heating = less driver thermal power distortion = more flat HF BW
Historically, drivers might have hundreds of ohms [FWIW my 1960 AM tube radio clock's is listed as 600 ohms!] to keep power requirements next to nothing since power was incredibly expensive, though as design/materials/manufacturing knowledge increased it has slowly changed to the exact opposite plus the HF response can be adjusted to make them virtually the same, making choosing almost moot unless a low power amp and/or a very wide bandwidth ['full-range'] is required.
Last edited:
4 Ohm versions of the 'same' driver are typically 3dB more sensitive. They will model slightly differently from the 8 ohm version.
Those advocating for 4 ohm never measured distortion of an amplifier for 4 ohm, 8 ohm and 16 ohm.
Its your decision, perhaps you enjoy to torture your amp with 4 ohms, while it surely drops below that, providing you with nasty distortion artifacts.
Enjoy.
Its your decision, perhaps you enjoy to torture your amp with 4 ohms, while it surely drops below that, providing you with nasty distortion artifacts.
Enjoy.
It has a lot of factors involved in the decision Tube amp or solid state? If it is a quality solid state amp that can run 4 ohm speakers you will get more power out of the amp at 4 ohms. You will also get more distortion and heat. If it a tube amp make sure it has the proper output for the impedance selected. You will not get any more power in 4 ohms. Look at the specs of both impedances and model both for cabinet size etc.. They will be different. Many times you hear the 4 ohm unit plays louder than the 8 ohm, if it’s on a SS amp you get more power into 4 ohms so you’ll gain 3db in theory. The speaker isn’t more efficient it’s just getting more power so it plays louder. If you’re going to use 2 per channel you’ll get6db more output, 2 drivers doing the same thing is 3db and 4 ohms is 3db so 6db of increased output for “free”. 8 ohms is easier on the amp and there will be less heat due to less current flowing. Lots to weigh.
In an amp with a very well designed power supply there isn’t a huge difference. If the amp is rated at double the wattage into four ohms it is well designed. An even better test is if the amp can be switched into mono it should have four times the output power as in stereo. That test pushes both channels to the max at the same time so you know it’s well built. Remember you are doubling the required current in four ohm and most amps are not thrilled doing that at full power out. If you’re not going to hammer on it you might be fine.
Pete, a subjective opinion on some Class AB amps is that it's better to reach a voltage limit than to find a current limit.
The 4 ohm speaker is more sensitive, not more efficient. This last segment of your response is rife with missing valuable information to make this easier to understand for someone new.
2 drivers per channel wired in parallel compared to 1 yields +6dB. Just using 2 in series nets a null gain, but they are 'doing the same thing'.
The gain in sensitivity is due to the doubling of cone area (+3dB), and also the halving of impedance resulting in twice the current (+3dB). Just being 4 ohms does not make it 3dB gain, unless the reference of a prior situ is provided. When parallel wired; 2x 16 ohm drivers or 2x 6 ohm drivers or 2x 8 ohm drivers all will yield a +6dB compared to a single driver.
You may think I'm splitting hairs, but this information is important.
One of the big pros is that it's much easier to pump high power into 4ohms (and now even 2ohms) than into 8ohms from a PA perspective - it's simply a case of making the amplifier output stages able to handle higher current at the same voltage. For ordinary home listening, 4ohm speakers could give problems with some low powered hifi amplifiers more happy with an 8ohm load.
te 4 ohm speaker is not more sensitive, it is getting twice the current from the amp compared to an 8 ohm speaker. As such it is getting twice the wattage. If given the same wattage they both will put out the same Db level. If given the same voltage the 4 ohm unit will be 3db louder.
Wrong. The 4 Ohm version is more sensitive, because sensitivity means Voltage sensitivity, in other words, how much Voltage we have to send to the speaker for X dB SPL. Of course they have probably both the same (or very similar) efficiency, because efficiency means how much Wattage we have to send to the speaker for X dB SPL.
With a Voltage source amplifier (most solid state amps), the 4 Ohm version will pull more current than the 8 Ohm version for the same Voltage. That is why the 4 Ohm version is more sensitive than the 8 Ohm, because it produces more SPL for the same Voltage.
Last edited:
At this point it might be worth a reminder that doubling the power into a loudspeaker does not make it twice as loud to our ears - that requires a 10db increase in spl and ten times the electrical power in order to double the apparent loudness. (If a given speaker produces a sound level of 85dB with one Watt of power, it will require 100W to produce 105dB). Note that this 10dB is not a mathematically derived figure, but the average and universally accepted subjective result of audiometric testing of many real people.
It is not surely common practice to refer to a speaker's sensitivity in terms of power and distance - dB/W 1m so that impedance can be ignored, not dB/2.83V 1m?
dB/W is the indicator of efficiency, but often called as sensitivity. But with most amps, we adjust the output Voltage (Wattage only indirectly) with the volume knob and the Wattage depends on the impedance of the speaker and that latter is usually not constant, so if the speaker impedance at 100Hz is 8Ohm, then 2.83V means 1W at that frequency, but if at 500Hz is 16Ohm for the same speaker, then the adjusted 2.83V means 0.5W at that frequency.
WRONG.
Your so called "definition" is completely misleading and useless.
Of course perfect for some unscrupulous marketers.
By your definition, a short is the best load.