We can argue what should be ... all day long. But, we have to look at the current reality.
I think we have made it clear the nature of 4 ohms speakers and 8 ohms speakers and have even given you way to adjust the output level when both speakers are rated at 1w/m
But I repeat, unless it serves the design in some other way or provides some other benefit, you don't choose a 4 ohm driver simply because it is a 4 ohm driver. That is just straining the amp to no end. Though it is probably less strain when the mid/high is 4 ohms because there is generally less power in that area. A 4 ohm bass driver would be more demanding of the amp. But as you will see below, 4 ohm rates speakers systems are nothing new.
Now, some manufacturer's do choose 4 ohms speakers. For example, Dynaudio makes very good sounding speakers, and most of them are 4 ohms. There is probably some engineering reason or design philosophy behind that choice, but it is not simply to have 4 ohm speakers. There is a greater purpose that coincidentally results in the speaker being 4 ohms.
As to the suggestion that no reputable speaker maker would do any thing other than use 2.83v/m, I've already shown that Dayton Audio rates both 8 ohm and 4 ohms speakers at 1w/m. I think most would agree that within its price range, Dayton Audio is a reputable company.
And keep in mind, it would be to their advantage to rated 4 ohms speakers at 2.83v and gain the corresponding +3dB higher output. But they don't. At least not based on the specifications I found at Parts Express.
You can't wish reality into being. It is what is. However with a strong enough lobbying effort, with enough discussion, and with a general consensus, you could probably get one single worldwide standard for Sensitivity ratings. Though that would take a sizable chunk of your life and your fortune.
It makes more sense to simply have a basic understanding of speaker design, and choose your speakers on that knowledge.
In your example, the 4 ohm driver is the mid/tweeter driver. Therefore if it is 4 ohms and louder, you will have to bring it down to more closely match the woofer. Though not precisely so, in general, you want the various driver's outputs balanced. Though absolutely equal does not necessarily meant that they will sound equal.
Though only theoretical, if you have an 8 ohm bass and a 4 ohm mid/high, it is conceivable that the 8 ohm bass could be louder. That would be rare in reality, but is conceivable.
However, in most cases, 4 ohm or 8 ohm, the tweeter is too loud and needs to be brought down.
Could you give us some more context to your original question? Is this a design you are thinking about? Did you have specific drivers in mind? Or, at this stage is it all conceptual? A theoretical question solely to increase your general knowledge?
I think we've exhausted the general discussion, but perhaps if you could add some more framework to the question, we could answer more specifically within your framework.
1w/m vs 2.83v/m IS a debate, and it is an old one, and like so many of these debates, once started they ping-pong back and forth endlessly. There are several 'hot' topics like this in the audio world, that are often discussed and never resolved, and then they are discussed again.
So, if there are more specifics you can give us to re-frame the question into a more practical real-world context, then there is probably more to be said. If not, then I don't know where the conversation can go from here.
Just a few thoughts.
Steve
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Thanks. I'm choosing drivers for a very simple 2 way 1st order design and don't want to make any expensive mistakes before purchase; the 8" nomex Peerless is far cheaper than other candidates but 8 ohm. Its rated Half Space Sensitivity @ 2.83V is 89.6 and 1w/1m is 90.2
The Alpair 6p is 4ohm. Its rated 86dB @2.83v altho it looks a little higher in the treble region- I wanted to mount it in a v shallow waveguide altho this may push the treble rise too far
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if these are accurate then ot's the same as the Tannoy I explained earlier. ".83Vac goes only 89.6dB @ 1m but when the voltage is increased so that 1W is delivered to the slightly higher than 8ohms impedance we see an extra 0.6dB.
The slight rise in response is usually corrected with a little EQ.
That EQ may reduce the voltage sensitivity slightly below the stated 86dB/2.83Vac @ 1m.
You will have to pad down the 89.6dB driver to match the 86, or maybe 85.5dB driver. That 3 to 4dB difference will be very audible, if you don't correct for it.
I don't think it will need EQ, the response curve of the alpairs shows it pretty much matches the Peerless but with a drop in the upper midrange- this is intentional on the part of the manufacturer
http://www.madisoundspeakerstore.com/store/images/Image/alpair6p-spl.png
http://www.madisoundspeakerstore.com/store/images/Image/alpair6p-spl.png
Let's ignore any effect of a passive crossover as that is another ball of messy wax in itself...
If both drivers have the same SPL sensitivity, then the amount of radiated power depends on the amp.
Most solid state amps deliver more power (for the same given input signal level) into a lower impedance load than a higher impedance load.
So, the answer, in that case, would be that the 4Ω driver will produce more sound output than the 8Ω driver.
If both drivers have the same SPL sensitivity, then the amount of radiated power depends on the amp.
Most solid state amps deliver more power (for the same given input signal level) into a lower impedance load than a higher impedance load.
So, the answer, in that case, would be that the 4Ω driver will produce more sound output than the 8Ω driver.
The number I'm finding for the driver are $80 for the 8" Peerless Nomex and $54 for the
Markaudio Alpair-6P Paper Cone 3.5" Fullrange Gen 2.
You can certainly build speakers for less than that.
Do you have some sense of where you were going to crossover. Given that you are looking at a full range speaker rather than a tweeter, one assume a very low crossover, probably below 500hz.
Like most bass drivers, the Peerless get shaky fast above about 1khz. So it would require a crossover below that. Though I suppose it could be pushed up to 2k or so.
The Markaudio Alpair-6P seems to be functional above about 200hz. So certainly there is a workable range in there somewhere.
I'm wondering why you picked these specific speakers, though I don't mean to imply there is anything wrong with them, I'm just trying to understand what lead to your choices to better understand the project.
Steve
Markaudio Alpair-6P Paper Cone 3.5" Fullrange Gen 2.
You can certainly build speakers for less than that.
Do you have some sense of where you were going to crossover. Given that you are looking at a full range speaker rather than a tweeter, one assume a very low crossover, probably below 500hz.
Like most bass drivers, the Peerless get shaky fast above about 1khz. So it would require a crossover below that. Though I suppose it could be pushed up to 2k or so.
The Markaudio Alpair-6P seems to be functional above about 200hz. So certainly there is a workable range in there somewhere.
I'm wondering why you picked these specific speakers, though I don't mean to imply there is anything wrong with them, I'm just trying to understand what lead to your choices to better understand the project.
Steve
Thanks Steve, ok will try to answer these best I can.
I'm currently in the UK and Falcon Acoustics is by far the best place to buy (on price) - the Peerless is £65 inc tax and delivery. The Alpair is not available in the UK so I need to look into this more; possibly I cd purchase both drivers from the same retailer and then choose a different bass driver.
The Alpair has a very low Fs of 65hz, but as I'm going for a simple 1st order I want to stay a good 3 octaves above the impedance spike of the Alpair, at 550hz or so- also this will mean the peerless is around 12db down by 2khz ( or with the slope starting bf x/o point is it more?)
The reason for drivers of similar material is to do with integration.
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You're correct about PE's sensitivity ratings but that was not always the case and, in fact, was changed from using 2.83 volts to 1 watt just in the last year or so. When they did that, all of us stout PE fans wondered why in the heck did they do that? It has nothing to do with being reputable or not, it's just not a good way because it simply does not allow the sensitivities of drivers with different impedances to be compared. Sure you can say, "just add or subtract 3 dB SPL when comparing 8-ohm and 4-ohm drivers", but it's not that simple because driver impedances vary quite a bit even when they are all nominally the same value. Amplifiers are voltage sources and, really, the whole point is to determine what's the most accurate way to compare drivers' sensitivities? It sure ain't with a 1-watt input.
Paul
Paul
There's 2 schools of thought here I think. Even if an amp has a higher output into 4 ohms, I'm guessing Wolf is saying that through a passive x/o circuit bf meeting the 2 drivers, its the same output level regardless
I think there may be an unstated assumption here.There's 2 schools of thought here I think. Even if an amp has a higher output into 4 ohms, I'm guessing Wolf is saying that through a passive x/o circuit bf meeting the 2 drivers, its the same output level regardless
With a "simple" crossover (one designed assuming all drivers are resistors of equal value), the driver with the greater VOLTAGE sensitivity (as opposed to power sensitivity, which is how drivers are rated) will be louder. As far as volume level from the drivers, this is similar to wiring the drivers in parallel.
A "well designed" passive crossover will be designed for the exact models of drivers it's going to be connected to, and it will have a series resistance or an L pad to reduce the volume of the louder driver, making their outputs equal. In two-way systems the tweeter is (almost?) always more sensitive than the woofer, so the crossover has something in it that reduces the level going to the tweeter.
There's 2 schools of thought here I think. Even if an amp has a higher output into 4 ohms, I'm guessing Wolf is saying that through a passive x/o circuit bf meeting the 2 drivers, its the same output level regardless
Okay- given that an amp doubles its power into 4 ohms as compared to 8 ohms, and 2.83V is 1W at 8 ohms and 2W at 4 ohms; why can we not agree that 2.83V already takes the higher wattage output into account from the amplifier? It already does this for you if you use 2.83V as your designated voltage sensitivity rating.
IMO and IME, power sensitivity is pretty much useless when comparing drivers, unless they are all the same relative nominal impedance.
If a simple xover is used, and it is implemented correctly, the drivers will still not be working as if they are in parallel. That's not a probable result.
Later,
Wolf
Try looking for Tang Band Full Range or that the Dayton Reference 3" and 4" full range speakers. I know of at least one company in the EU that sells Dayton, though I don't know if they will have the specific Daytons I mentioned. Tang Band are also very common speakers.
They also sell Fostex which are popular full range speakers.
8" Woofers -
Woofers • 8" • Europe Audio
They have the Peerless Nomex, but I would consider looking at some of the SEAS in the same price range.
3" & 4" Full Range -
Fullrange • 3" • Europe Audio
Fullrange • 3.3" • Europe Audio
Fullrange • 3.5" • Europe Audio
Fullrange • 4" • Europe Audio
Though you choice, I would consider this combination, especially for a low crossover -
RS100-4 - Dayton 4 inch Reference Full-Range Driver - Europe Audio
RS225-8 - Dayton Shielded Woofer 8 inch - Europe Audio
I'm sure you are also familiar with Wilmslow Audio -
Drive Units: Treble Units, Co-axial Units, Midrange Units, Bass Units
Bass-mid & Bass Units
Full Range & Co-axial Units
They also have Fostex, Peerless, Seas, and many other brands.
Though I don't have a specific Source in the UK, here are some examples of full range Tang Band speakers -
Tang Band W4-1337SD 4" Titanium Driver 264-848
Tang Band W3-593SF 3" Full Range Silver Cone Driver 264-809
Tang Band W4-1052SDF 4" Full Range Speaker 264-913
Tang Band W4-1320SIF 4" Bamboo Full Range Speaker 264-914
Just to name a few Tang Band.
Steve
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Tinitus,
The problem is, you didn't actually ask a question.
Would you like to add a sentence that ends in a question mark? And given that you are a moderator, it seems unlikely that you don't understand the diagram, though I could be wrong on that. Still, I'll give it my best shot.
Given that you have a coil in series, we must assume that the two drivers are both woofers.
The COIL in the diagram will see the combined impedance of the speakers.
Rt = (R1 x R2) / (R1 + R2) = (8x16) / (8+16) = 128 / 24 = 5.3333 ohms
That is the impedance you must use to determine the value of the Coil relative to your selected crossover frequency.
EDITED: Revised for a Math Error. Hopefully, I got it right the second time around.
Next because the two drivers do not have the same impedance and they are in parallel, they will get the same signal voltage but will not consume equal amounts of power.
Let's apply 10v to make the math easier.
If we designate the 8 ohms as R1 and the 16 ohm are R2, here is the power applied to each speaker.
Pr1 = E²/R = 10²/8 = 100/8 = 12.5 watts
Pr2 = E²/R = 10²/16 = 100/16 = 6.25 watts
So twice the power is consumed by the 8 ohm driver.
We would then have to look at the Sensitivity specification of the speakers to determine the output of each, in order to determine if one speaker is going to be louder than the other. If the 16 ohm is rated at 90dB and the 8 ohm is 87dB, then they will be reasonable balanced. Assuming they both have the same cone area.
In my view, there is no right or wrong, there are only the goals and objectives of the design. Under some circumstance, this configuration might further the design, under other circumstances, this configuration might be detrimental to the overall design goals.
Is that what you had in mind for the question you never actually asked?
Steve/bluewizard
The problem is, you didn't actually ask a question.
Would you like to add a sentence that ends in a question mark? And given that you are a moderator, it seems unlikely that you don't understand the diagram, though I could be wrong on that. Still, I'll give it my best shot.
Given that you have a coil in series, we must assume that the two drivers are both woofers.
The COIL in the diagram will see the combined impedance of the speakers.
Rt = (R1 x R2) / (R1 + R2) = (8x16) / (8+16) = 128 / 24 = 5.3333 ohms
That is the impedance you must use to determine the value of the Coil relative to your selected crossover frequency.
EDITED: Revised for a Math Error. Hopefully, I got it right the second time around.
Next because the two drivers do not have the same impedance and they are in parallel, they will get the same signal voltage but will not consume equal amounts of power.
Let's apply 10v to make the math easier.
If we designate the 8 ohms as R1 and the 16 ohm are R2, here is the power applied to each speaker.
Pr1 = E²/R = 10²/8 = 100/8 = 12.5 watts
Pr2 = E²/R = 10²/16 = 100/16 = 6.25 watts
So twice the power is consumed by the 8 ohm driver.
We would then have to look at the Sensitivity specification of the speakers to determine the output of each, in order to determine if one speaker is going to be louder than the other. If the 16 ohm is rated at 90dB and the 8 ohm is 87dB, then they will be reasonable balanced. Assuming they both have the same cone area.
In my view, there is no right or wrong, there are only the goals and objectives of the design. Under some circumstance, this configuration might further the design, under other circumstances, this configuration might be detrimental to the overall design goals.
Is that what you had in mind for the question you never actually asked?
Steve/bluewizard
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so you say both drivers will have the same roll off slope, only with different SPL
just a quick question
say u mix an 8 ohm bass and a 4 ohm full range or tweet, will output be the same if the sensitivity
rating is the same for each? or will the 8 ohm driver have less output when used with the 4 ohm ?
hope this makes sense
Hi,
Yes and No are the simple answers.
However 4 ohm bass and 8 ohm FR makes far more sense
in the general scheme of things than the other way round.
Generally you want more bass sensitivity than the FR.
rgds, sreten.
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