just a guy, you are 50% right.
I will not prolongate this discussion but I just like to remember to avoid confusion:
The watt (symbol: W) - The unit is defined as 1 joule per second and can be used to express the rate of energy conversion or transfer with respect to time.
The volt (symbol: V) - is the derived unit for electric potential, electric potential difference (voltage).
The ampere (symbol: A) - An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire.
The ohm (symbol:
) - Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied.
In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current (AC) circuit. Impedance extends the concept of resistance to AC circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude.
So specify things in Volts alone means nothing for sound, you always need at least two information as:
Impedance (frequency dependent due to Le and Re) and current
or
Impedance (frequency dependent due to Le and Re) and voltage
or
Watts can shown alone once it's a results o Volts x Ampere and others equation.
Watts produce sound and not voltage and it's the simplest information even for an Engineer.
Simplifying, to understand "sound system information" people must understand about electric circuits otherwise they can be cheated.
AS long you know how to interpret the information it doesn't meter how it's published.
I will not prolongate this discussion but I just like to remember to avoid confusion:
The watt (symbol: W) - The unit is defined as 1 joule per second and can be used to express the rate of energy conversion or transfer with respect to time.
The volt (symbol: V) - is the derived unit for electric potential, electric potential difference (voltage).
The ampere (symbol: A) - An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire.
The ohm (symbol:
) - Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied.In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current (AC) circuit. Impedance extends the concept of resistance to AC circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude.
So specify things in Volts alone means nothing for sound, you always need at least two information as:
Impedance (frequency dependent due to Le and Re) and current
or
Impedance (frequency dependent due to Le and Re) and voltage
or
Watts can shown alone once it's a results o Volts x Ampere and others equation.
Watts produce sound and not voltage and it's the simplest information even for an Engineer.
Simplifying, to understand "sound system information" people must understand about electric circuits otherwise they can be cheated.
AS long you know how to interpret the information it doesn't meter how it's published.
Show how you can produce Watts in a speaker to produce sound without applying Voltage to said speaker.
Go ahead, I'll wait ;-)
Look, I'll leave it up to you to figure out for yourself how you said a whole bunch of nothing, starting with using a speaker's "max power handling", which more a marketing term than anything scientific. Would you really base a scientific analysis on a marketing term? It's like building a house on sand - it's not going to stand.
For a further hint of why your analysis is flawed, go back and read what I posted in post #18 and see what SCIENTIFIC (not marketing) parameter is missing from your analysis.
28.3V@10M is mathematically equivalent to 2.83V@1M. So you are right in your analysis above. It also gives a better idea of what the speaker's SPL would be like at "pro audio" levels (a 28.3V drive level is much more indicative of that usage than is a 2.83V drive level).
When you see SPL ratings at 1W/1M, they are usually done at 2.83V for a impedance rating of 8 ohms, or 2V for an impedance rating of 4 ohms. Seeing that the impedance of speaker can actually drop lower than its rated impedance in its passband, how does that fit into JAG's position on the matter?
Look - I'd love to know if any speaker company actually measures Rmin as suggested here, then adjusts the test voltage so that the result is exactly 1W/1M at the frequency which Rmin occurs. I suspect they'd be in the significant minority.
Post #14, where you reference it to the speaker's Re:
Post #19, where you reference it to the minimum impedance in the passband:
Those are TWO DIFFERENT THINGS. Re is a measurement of the speaker's DC resistance, NOT its minimum passband impedance, and you only jumped to using the latter as a reference after I took you to task about using the former.
Anyway, it's the last I have to say on the subject, as I believe I've made the point. Let's stop hijacking the original poster's thread!
No.
I tested the cabs using sine sweeps at various voltage levels and stop when the measured distortion started to rapidly increase and/or become audibly noticeable. Typically this happens when the cone starts to meet or exceed Xmax, or when the amplifier has run out of power.
I changed a few things in the design, e.g. moving the lower resonance frequency up a bit (to improve output capability in the passband), changed from a single expansion to a dual-expansion TH (ditto), and changed the physical layout, which made it easier to transport in my car. I also used significantly more bracing (see note below). As a result POC#3 definitely sounds better than POC#2. The POC#4 project, which includes a change in the layout of the horn's path to take cone compensation into consideration, was put on hiatus before I could do any detailed testing, but preliminary testing showed quite positive results.
As for compression ratio, there's a lot of truth to what Art says. A heavier cone usually means a stronger cone (though the material the cone is made of also makes quite a difference). If the drivers you're thinking of using use cone material similar to what the B&C drivers using, then you may likely get away with a higher compression ratio. But too be sure, you could just build a test TH box and do the same thing I did - sine sweeps at gradually increasing voltage levels and examine what happens to the measured distortion. Stop the tests when it starts to jump up, or when your amp starts to clip. And please, brace the blinking box properly - panel flex can noticeably increase distortion, skew the results and "colour" the sound the TH produces.
In post 18 you made it very clear that impedance varies with frequency. You know what else varies with frequency? EVERYTHING. Including spl, efficiency, and yes, even sensitivity.
You seem disgusted by the idea that a "1 watt" specification is not actually 1 watt at all frequencies, but 2.83V is even further off the mark unless the speaker's minimum impedance is exactly 8 ohms. Specifying sensitivity of all products at 2.83V regardless of the product's actual impedance is even more unscientific, more of a marketing strategy, more of a "single number to represent a complex answer" than a 1 watt specification. And this "unscientific" max power handling spec (input power rating) as well as maximum output rating are right below the sensitivity spec on the spec sheet - check the Danley link below.
So if you want to compare two speakers fairly do you compare them both at 2.83V, which in most cases will give a pretty dramatically different power level to each speaker?
NO. You compare them at the same power level. Impedance varies with frequency. So what? Everything varies with frequency. At least if you compare at a voltage that give the same 1 watt to both speakers you are closer to an equal power comparison.
Honestly, what good does it do to specify sensitivity of two different speakers at completely different power levels? None.
Really? Did you do a complete study with polls?
A quick peek at parts express, maybe the largest and most popular diy driver retailer shows that almost every product is specified at 2.83V regardless of the product's nominal or actual impedance. Here's a dvc 4 ohm per coil driver with all specs specified with coils in parallel (2 ohms) but sensitivity specified at 2.83V.
Dayton Audio RSS265HO-44 10" Reference HO DVC Subwoofer
Here's one from the most popular commercial ready made speaker manufacturer on this forum, Danley. This speaker has a 2 ohm NOMINAL impedance (which means the actual impedance is probably around 1.4 ohms) and the sensitivity is specified at 2.83V. Not only that, but they have the audacity to also give the 2.83V sensitivity of this 2 ohm nominal speaker at a higher frequency, at a peak, near or outside the usable passband. Even if an end user chose to use this speaker at the specified higher frequency where it peaks, that peak would be pulled down to the average sensitivity in the passband, so this extra "extra high" sensitivity rating serves what purpose exactly? This is cheating on top of cheating to fool people that don't know better.
Tapped Horns | Danley Sound Labs | Danley Sound Labs, Inc.
It fits like I said several times - specify sensitivity at a voltage that relates to 1 watt by referencing voltage to minimum impedance in the passband and you will have an unbiased and COMPARABLE sensitivity rating that you can compare to every other speaker on the planet.
The sad truth is that no company could specify sensitivity in a meaningful and comparable way like a 1 watt figure. The competition in the marketplace is fierce and the average consumer is really really dumb. You can't enter the marketplace with truth and logic on a spec sheet when everyone else is cheating.
You called max power handling an unscientific marketing term, and admittedly it's a bit ambiguous and hard to nail down to an exact number. But what is that Danely spec sheet I just linked other than pure marketing? Specifying a 2 ohm nominal speaker (probably 1.4 ohm actual impedance) at 2.83V at a peak outside the passband? WTF is that all about? What scientific explanation do you have for that? This is your house on sand, but it's standing just fine because the people that don't know better will buy this product based on these ludicrous specs and the people that should know better are here on the forums condoning it.
NOTHING on that Danley spec sheet is even remotely scientific, comparable to any other product or anything other than marketing (except maybe the actual measurements). Even the frequency response is not a +/- figure, it's only - 3db and -10db. Why is that? It's because if they did +/- 3 db like they should, that fantastically high sensitivity peak at 78 hz that they had the audacity to quote would be past the +3db point, so not even inside the passband.
I could go on for awhile about all the problems on a Danley spec sheet, but this particular case of specifying the sensitivity of a 2 ohm nominal speaker at 2.83V AND specifying an extra sensitivity spec at a peak outside the passband should be more than enough proof that Danley's sensitivity spec method is all about marketing and completely useless for anything else like giving unbiased and comparable information about the speaker.
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Good grief - go back and read my post again. You are talking about a SENSITIVITY rating which IS done in VOLTS, when I referred to "1W/1M", which is an EFFICIENCY rating done in WATTS. I SPECIFICALLY started my comment (which you quoted) with "When you see SPL ratings at 1W/1M...". If you still don't understand the difference between the two terms, it's no wonder your reasoning is so flimsy, flawed and all over the place.
Oh good grief, here's my LAST post on the matter.
Here's what that Danley specification tells me:
1. The amplifier that I choose to drive this speaker must be rated to be able to drive a 2 ohm impedance.
2. You didn't state the RMS rating for the speaker, but if it was given, then for best results, the usual "rule of thumb" is to use an amplifier that's capable of delivering 2xRMS into the speaker's nominal impedance, so if the speaker is rated @1000W RMS, I should be safe going with an amp capable of 2000W into 2 ohms, and if the amp is capable of more than that, I should consider limiting its power output to 2000W.
3. Now, let's say I have to replace the speaker for some reason. if I come across a speaker that happens to have a 4 ohm nominal impedance instead, but everything else is identical (e.g. frequency response, SENSITIVITY rating and RMS power rating), then I should be able to simple swap the two speakers and expect the same or very similar results when using that amplifier, IF it matches the requirements outlined in point #2.
I really don't understand why this is so difficult to comprehend and why it makes it so easy for any prospecting pro audio buyer to make an informed choice about their purchase.
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Eh?
Sensitivity should always be stated in terms of V/M, usually 2.83V/M. That's how the term is defined.
Efficiency should be always stated in terms of W/M, usually 1W/M. That's how the term is defined.
Anyone who specifies a sensitivity rating in terms of "xxxdB @1W/M" or an efficiency rating in terms of "xxx dB @2.83V/M" is using the terms incorrectly. And yes, some companies are actually guilty of this! Even Parts Express
. Have a look at the sensitivity rating for the Dayton Audio PA380-8 (where they state it correctly) and then the Eminence LAB 12 (where they state it incorrectly - that's actually an EFFICIENCY rating, NOT a SENSITIVITY rating, and a peak at the specifications PDF where they detail how they derive it clearly shows this).The spec sheet specifically says it switchable - either a 2 ohm nominal load or two 4 ohm nominal loads. So already your spec sheet analysis is wrong - you could use a 4 ohm amp that is not rated to be run in 2 ohms. Amps that can run stereo 4 ohm loads USUALLY are rated for a bridged 2 ohm load but not always.
Wow, that's a super scientific analysis. WAY more scientific than specifying sensitivity based on actual power input rather than 2.83V for everything.
Point #3 is a really convoluted attempt to justify a nearly meaningless and incomparable spec. I'm not even clear if you are talking about swapping the drivers out or swapping the whole cab for two fully enclosed 4 ohm subs - I will assume the latter.
While this may be obvious to you, it certainly won't be obvious to the average uninformed customer, the average customer doesn't even know that two fully powered cabs have 6 db more output than one fully powered cab.
Besides, even in this convoluted attempt to justify the specs, NOTHING is equal. Your two 4 ohm cabs are not actually 4 ohms (and neither is the Danley cab 2 ohms) these are both nominal numbers that could vary by a factor of 2 within the nominal category. Sensitivity rating might (probably will) vary based on the ACTUAL (not nominal) impedance and the point on the frequency response curve where the manufacturer chose to grab the spl level. (In more cases than you might think, sensitivity is specified at a peak, or a subwoofer sensitivity is specified at a midband frequency WAY higher than it ever gets in the intended passband.) And as we both mentioned, the power rating spec is hard to nail down to an actual number - and furthermore, different manufacturers spec power handling in different ways.
So in conclusion the 3 things that the Danley spec sheet tells you are not nearly as clear cut as you make them seem, and you could be VERY far off by assuming anything you have said is accurate.
I'm not arguing the general statements here, I'm arguing the part in bold. Sensitivity should be specified at an equal power level, not a flat rate 2.83V.
No it's not. It simply went way over your head.
Anyway, my last post on the subject. I think I've explained my POV quite clearly, without adjusting my terms of reference as you have (i.e. shifting from "Re" to "minimum impedance" when I pointed out that impedance varies with frequency, making your whole argument flimsy and unsupportable), so I will leave it at that.
Like I told you really clearly, in most cases these numbers are interchangeable, within a very small percentage of each other. it's easier to use Re because it's right there on the input screen, it's a lot harder to look at the impedance graph, zoom in, check the minimum impedance in the passband, go back to the input screen, adjust voltage, run the sim again. In most cases it's fine (and much easier) to use Re.
LOL, I pointed out that EVERYTHING varies with frequency. electrical impedance, acoustical impedance, sensitivity, efficiency, power handling, excursion, spl, group delay, phase, input power, directivity, velocity, pressure, and everything else. EVERYTHING varies with frequency. And yet we are able to express all of these things with a single number spec or at most a two number spec (and a bit of commonly acknowledged assumptions about what we are talking about) even though they are all better described with a graph showing all frequencies.
Your arguments are so weak all you can focus on and keep repeating is "Re vs minimum impedance" and "impedance varies with frequency", neither of which have any relevance.
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If I understand correctly, all that just a guy is suggesting is to normalise the input voltage Eg to compensate for different driver Re values, so that power response chart absolute levels will not be offset, making comparisons easier.
To illustrate the process:
Attachment 1 shows the standard Hornresp default record (grey trace) compared to the same record with Re changed from 6 ohms to 3 ohms (black trace). Eg = 2.83 volts in each case.
Attachment 2 shows the Hornresp default record with Eg = 2.45 volts (1 watt into Re of 6 ohms) (grey trace) compared to the same record with Re changed from 6 ohms to 3 ohms and Eg = 1.73 volts (1 watt into Re of 3 ohms) (black trace).
I don't see any particular problem in doing this if you can live with having different input voltages for different speakers. As far as the actual sensitivity and efficiency values for each speaker are concerned, they do not change as they are independent of Eg.
Sensitivity is output sound pressure for a given input voltage.
Efficiency is output sound power for a given electrical input power.
Attachments
Thanks David.
However, what JAG wants (and he's suggested it in earlier messages) is for manufacturers to give ratings based on input voltage for "equal power", rather than the standard sensitivity and efficiency spec, and that manufacturers who quote sensitivity specifications using basically industry-standard processes are just trying to fool prospective buyers.
His specification would end up looking something like "xxx dB y.yy V /1M" , for a speaker that would produce xxx dB when fed a voltage of y.yy which would actually produce 1W at Re (which he subsequently changed to minimum impedance, when I pointed out that Re may not represent the speaker's minimum impedance through its passband - a very good example being sealed subwoofers).
However, there's already good enough rating for that - just look for the manufacturer's efficiency (e.g. 1W/1M) rating for the same speaker. Or just work it out on your own from the published sensitivity rating and the published Re, minimum impedance or whatever new impedance benchmark you choose to use for your adjusted definition
.I must ask forgiveness from all for being a bit touchy last night. This whole Trump winning the Presidency thing. Youngest daughter is very upset and changing (still somewhat vague) plans to study in the US.
About that "industry standard"... I've seen several methods from large (and smaller) names.
- 28,3V/10M
- 2,83V/1M
- 1W to nominal impedance/1M
- 1W noise to nominal impedance/1M single figure
one that really blew my mind:
- this is a tapped horn system consisting of 4 horns, I sweep one, 1W1M nom. Imp., measure 106dB (probably 1 peak in band) doubling cabs twice adds 6dB efficiency, so system 1W1M nom.imp. is 112dB. M4.18 | MM-Acoustics That explains getting 153dB max output
I think we need to take a step back and agree on what you want to achieve with the comparison.
For me: I have system A and B. These systems have certain sensitivity plots, and a certain powerhandling.
I want to know 2 things:
- what system makes most noise at (roughly) the same power level?
- what system makes most noise at RMS power?
for the first i think 1W in minimum impedance is fairest.
For the second it is easiest to use this sensitivity rating and add the RMS power in decibels
To make it easier i'd be happy with 1W in nominal impedance. Not a fair comparison, but good enough.
- 28,3V/10M
- 2,83V/1M
- 1W to nominal impedance/1M
- 1W noise to nominal impedance/1M single figure
one that really blew my mind:
- this is a tapped horn system consisting of 4 horns, I sweep one, 1W1M nom. Imp., measure 106dB (probably 1 peak in band) doubling cabs twice adds 6dB efficiency, so system 1W1M nom.imp. is 112dB. M4.18 | MM-Acoustics That explains getting 153dB max output
I think we need to take a step back and agree on what you want to achieve with the comparison.
For me: I have system A and B. These systems have certain sensitivity plots, and a certain powerhandling.
I want to know 2 things:
- what system makes most noise at (roughly) the same power level?
- what system makes most noise at RMS power?
for the first i think 1W in minimum impedance is fairest.
For the second it is easiest to use this sensitivity rating and add the RMS power in decibels
To make it easier i'd be happy with 1W in nominal impedance. Not a fair comparison, but good enough.
I have a 1960s valve amp - It has impedance taps and produces 20 watts into 4 ohms - 8 ohms and 16 ohms.
So if I design a speaker for that amp I want to know roughly what efficency the speaker is per watt regardless of its impedance.
If as lordsansui I have chosen a driver and I want to compare 2 cabinet designs then 2.83V is a reasonable choice to compare the cabinet performance.
If I want to see show the cabinet performs I would adjust the voltage until I reach X-max. Which if exceeded distortion is likely to become an issue.
It probably would be reasonable then to look for an amplifier that can deliver double the power needed for theoretical x-max or even more depending on the characteristics of the driver. This could combat losses due to thermal compression, and allow transients that exceed x-max which might not be hi-fi but might be rock & roll!
The overall performance of the system is what should concern us not some theoretical advantage.
So if I design a speaker for that amp I want to know roughly what efficency the speaker is per watt regardless of its impedance.
If as lordsansui I have chosen a driver and I want to compare 2 cabinet designs then 2.83V is a reasonable choice to compare the cabinet performance.
If I want to see show the cabinet performs I would adjust the voltage until I reach X-max. Which if exceeded distortion is likely to become an issue.
It probably would be reasonable then to look for an amplifier that can deliver double the power needed for theoretical x-max or even more depending on the characteristics of the driver. This could combat losses due to thermal compression, and allow transients that exceed x-max which might not be hi-fi but might be rock & roll!
The overall performance of the system is what should concern us not some theoretical advantage.
The secret of success is to make complex things became simple and not the opposite
I saw on interview with Joe Satriani, the best guitar player in the world (people say), and he said that the secret of his music is to do a lot of complex things playing guitar, add many techniques and so on, but for who is listening his music it should be percept as being simple so this will increase the amount of people that will like his music. If it sound too much complex it will reduce the fan base.
If one music is simple to listening it doesn't mean that it's simple to play.
I'm engineer (not linked to sound) and engineers like complex stuffs but this is not good for market, we need to be able to transform complex stuffs into simple ones. Remember, that data sheet is there if you want to play with number.
I saw on interview with Joe Satriani, the best guitar player in the world (people say), and he said that the secret of his music is to do a lot of complex things playing guitar, add many techniques and so on, but for who is listening his music it should be percept as being simple so this will increase the amount of people that will like his music. If it sound too much complex it will reduce the fan base.
If one music is simple to listening it doesn't mean that it's simple to play.
I'm engineer (not linked to sound) and engineers like complex stuffs but this is not good for market, we need to be able to transform complex stuffs into simple ones. Remember, that data sheet is there if you want to play with number.
- Compare systems at same voltage? (amplifier constrain, we set the gain on it, the current (A) and the power (W) is consequence)
- Compare systems at 1W/1M? (put all things at the same base / voltage and impedance different for each system)
- Compare systems at maximum performance (no constrains)
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.