Simple minded here,
Don't want to miss anything before I start but even thought this is probably a simple question I missed because I'm tired, if I make a speaker cabinet with 2 drivers, say a 6 ohm tweeter and a 8 ohm woofer what would the final impedance of the cab be? I understand can be wired differently but if I followed the schematic below to build crossover how would I calculate? (Not my schematic, just borrowed it)
Don't want to miss anything before I start but even thought this is probably a simple question I missed because I'm tired, if I make a speaker cabinet with 2 drivers, say a 6 ohm tweeter and a 8 ohm woofer what would the final impedance of the cab be? I understand can be wired differently but if I followed the schematic below to build crossover how would I calculate? (Not my schematic, just borrowed it)
Attachments
In the ideal world, if the C & L values are correct, the impedance will be 6Ohms above the crossover frequency and 8Ohms below it.
Between 8 and 6Ohms dependant upon the frequency averaging around 7 I suppose. If there was no crossover it would be around 5.
Ok so as long an not wiring a stupid amount of drivers making a really
Low rating its not an exact science, like off the shelf speakers may say 8 ohm bit that's just kind of a 'wont melt at this rating' guide from the manufacturer?
If I made these as above and called the 8 ohm for safety that would be about right? I understand there is no perfect crossover and there is always losses somewhere.
Low rating its not an exact science, like off the shelf speakers may say 8 ohm bit that's just kind of a 'wont melt at this rating' guide from the manufacturer?
If I made these as above and called the 8 ohm for safety that would be about right? I understand there is no perfect crossover and there is always losses somewhere.
Keep in mind that a 8 ohm nominally rated bass driver will have impedance swings as low as 6 ohm and as high as about 50 ohms. Then the cabinet creates some impedance loading on the Speakers and their impedance.
However, using the nominal values, you use the value of the lowest component. In this case, that is 6 ohms. At some frequency the speaker is going to be 6 ohms nominal. If only a single speaker cabinet is used on an amp channel, then 6 ohms or 8 ohms doesn't really matter. However, when you try to add TWO speaker to each amp channel, there combined impedance become pretty critical as it can't drop below 4 ohms nominal.
However, that's a bit more than you need to know at the moment. The Speaker System is rated at the nominal impedance of the lowest driver. Simple as that. In your case, or your example, that would be 6 ohms.
If it happens to be a 4 ohm tweeter with an 8 ohm bass driver, then it is a 4 ohm rated speaker system.
If the tweeter is 12 ohms, and the woofer is 8 ohms, it is an 8 ohm rated system.
If the tweeter is 8 ohms and the woofer is 8 ohms and the midrange is 8 ohms, then the entire system is 8 ohms.
They system is rate at the nominal impedance of the lowest driver.
As others have pointed out, that is for a single woofer, single mid-range, and single tweeter. If you use multiple drivers, then it is the lowest combination of drivers. For example, two 8 ohm woofers in parallel create a combined impedance of 4 ohms, and that would be the rating of the speaker system.
Steve/bluewizard
However, using the nominal values, you use the value of the lowest component. In this case, that is 6 ohms. At some frequency the speaker is going to be 6 ohms nominal. If only a single speaker cabinet is used on an amp channel, then 6 ohms or 8 ohms doesn't really matter. However, when you try to add TWO speaker to each amp channel, there combined impedance become pretty critical as it can't drop below 4 ohms nominal.
However, that's a bit more than you need to know at the moment. The Speaker System is rated at the nominal impedance of the lowest driver. Simple as that. In your case, or your example, that would be 6 ohms.
If it happens to be a 4 ohm tweeter with an 8 ohm bass driver, then it is a 4 ohm rated speaker system.
If the tweeter is 12 ohms, and the woofer is 8 ohms, it is an 8 ohm rated system.
If the tweeter is 8 ohms and the woofer is 8 ohms and the midrange is 8 ohms, then the entire system is 8 ohms.
They system is rate at the nominal impedance of the lowest driver.
As others have pointed out, that is for a single woofer, single mid-range, and single tweeter. If you use multiple drivers, then it is the lowest combination of drivers. For example, two 8 ohm woofers in parallel create a combined impedance of 4 ohms, and that would be the rating of the speaker system.
Steve/bluewizard
If the power being used by the tweeter is 20% of the total and the other 80% going to the woofer the nominal load is 8Ω. It's current that drives woofers which places the greatest load on an amplifier where it's rating is critical. Tweeters are more of voltage devices and place little load on an amplifier.
Power is the Voltage times Current.
Regardless of whether you are feeding a 1/4w to the speaker or if you are feeding 100w to the speakers, 4 ohms is still 4 ohms.
"Load" is the same as impedance in this context, and once again, 4 ohms is still 4 ohms. That Ohm rating determines the current flow. Regardless of the applied voltage, current still flows like it was flowing into 4 ohms.
As I said, with only ONE speaker per amp channel and assuming a fairly descent amp, the impedance doesn't matter that much. But if you add multiple speaker systems to an amp channel that 4 ohm tweeter is going to make a big difference. That is going to drive the functional impedance down to 2 ohms or less. Few amps will tolerate that for long.
Steve/bluewizard
I'd like to kindly thank you for explaining Ohms law to an EE. Perhaps you should reread what was said and in context to how impedance ratings are defined in respect to multiway speakers next time?
H Burch,
Greebster's got it. In layman terms, the woofer is where you worry most about the impedance, so safe to say you could call it a nominal 8Ω load.
Greebster's got it. In layman terms, the woofer is where you worry most about the impedance, so safe to say you could call it a nominal 8Ω load.
You can all it anything you want, all it "Mary" if it makes you feel better, and AS LONG AS you only have ONE speaker system on each amp channel, it doesn't matter what you call it.
Now we all seem to reasonably agree that the power demands in the high frequency range is not that demanding. Though, oddly, people manage to blow a lot of tweeters ... curious.
But, when you put TWO of these speaker sets on a given amp channel, the impedance can drop down in the 1.5 ohm to 2 ohm range. If you are OK with that fine. But if you label a speaker 8 ohms, that is what you are implying, that you can run two speakers per amp channel. But can you?
Now the above (2 spkrs/ch) might work, but it is somewhat deceptive.
Further, I'm not doubting the expertise of the last two posters. I readily admit that they are both more knowledgeable and experienced than I. But I do have a Bachelor's Degree in Physics - EET.
So, like I said, as long are you only have one of these speaker per amp channel, what you call it doesn't matter. There are several nominal 8 ohm rated speakers that can fall as low as 3.4 ohms (ie: B&W). But, one would not put two of those per amp channel on anything but the strongest amp.
I think the underlying question is far more complex than simply 8 ohm woofer, 4 ohm tweeter. The cabinet will matter, the crossover points will matter, the tweeter attenuation will matter, the amp the speaker are used on will matter.
Again, I bow to superior expertise, but I haven't change my mind, because I don't think it is a matter of fact, but rather a matter of perspective.
For what it is worth.
Steve/bluewizard
Now we all seem to reasonably agree that the power demands in the high frequency range is not that demanding. Though, oddly, people manage to blow a lot of tweeters ... curious.
But, when you put TWO of these speaker sets on a given amp channel, the impedance can drop down in the 1.5 ohm to 2 ohm range. If you are OK with that fine. But if you label a speaker 8 ohms, that is what you are implying, that you can run two speakers per amp channel. But can you?
Now the above (2 spkrs/ch) might work, but it is somewhat deceptive.
Further, I'm not doubting the expertise of the last two posters. I readily admit that they are both more knowledgeable and experienced than I. But I do have a Bachelor's Degree in Physics - EET.
So, like I said, as long are you only have one of these speaker per amp channel, what you call it doesn't matter. There are several nominal 8 ohm rated speakers that can fall as low as 3.4 ohms (ie: B&W). But, one would not put two of those per amp channel on anything but the strongest amp.
I think the underlying question is far more complex than simply 8 ohm woofer, 4 ohm tweeter. The cabinet will matter, the crossover points will matter, the tweeter attenuation will matter, the amp the speaker are used on will matter.
Again, I bow to superior expertise, but I haven't change my mind, because I don't think it is a matter of fact, but rather a matter of perspective.
For what it is worth.
Steve/bluewizard
Last edited:
I think it's worth a lot, I like a varied
Bit of info to keep things interesting! So to further the interest angle
Here say I want to use piezo horns
For high freq, how would that effect things? Say a 8 ohm woofer
And 830 ohm piezo driver.
Bit of info to keep things interesting! So to further the interest angle
Here say I want to use piezo horns
For high freq, how would that effect things? Say a 8 ohm woofer
And 830 ohm piezo driver.
H,
These type of tweeters are virtually a Zero load (high impedance), but at very high frequencies their capacitive reactance rises dramatically which places an extreme load on most amplifiers causing them to go into self oscillation. Normally a 10Ω resistor in series to prevent this from happening.
These type of tweeters are virtually a Zero load (high impedance), but at very high frequencies their capacitive reactance rises dramatically which places an extreme load on most amplifiers causing them to go into self oscillation. Normally a 10Ω resistor in series to prevent this from happening.
They blow tweeters because they are clipping the amp, creating massive amounts of high frequency energy that is not music.
Actually I can, the amps I use (all 8 channels of them) are rated for 2Ω.
It is fact. Perspective is nothing more than subjective opinion and not based on evidence.
How very interesting, but in addition to that can it be used in a crossover
To keep the order the same
Or does that not matter so much with a piezo?
To keep the order the same
Or does that not matter so much with a piezo?
"... if I make a speaker cabinet with 2 drivers, say a 6 ohm tweeter and a 8 ohm woofer what would the final impedance of the cab be?"
Does this sound like a question from someone who has 2 ohm rated amps?
If he has an 8 ohms woofer and a 6 ohms tweeter, then to be safe, rate the speaker at 6 ohms.
As long as only one speaker is used on one amp channel, it won't matter, it should work on any common amp. That's all the OP needs to know.
Steve/bluewizard
Yes it matters, 10Ω load instead of the typical load of 4/8 for crossover calculations
- Status
- Not open for further replies.