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Part 3 of 3
OK, getting back to that 46 dB thing in part 2, is that good or bad, what does it mean ? And why can’t we hear that big difference in our equipment ?
Fortunately, when the speaker is considered as an integral part of the amplifier system, it doesn’t mean all THAT much (if one ignores a parameter called “damping”). That’s because of a VERY poorly understood subject: negative feedback. (The howl produced by the interaction between your guitar and close proximity to your amplifier is POSITIVE feedback.)
Negative feedback exists within all guitar amplifiers (unless intentionally removed – bad idea), the process starts by detecting the actual audio voltage across the speaker system and then, further back in the amplifier chain, compensating for two things:
SOME of the speaker shortcomings that we’ve been discussing
Distortion and poor frequency response of output power stages in almost every type of amplifier but especially tube amplifiers.
There are several reasons why you can’t easily detect poor amplifier/speaker performance:
Our equipment doesn’t have to be very good if it only has to reproduce a bass instrument or a guitar instrument, neither instrument has a very broad frequency range. Problems start to occur when we require the speaker to reproduce very broad bandwidths, like a piano. (BUT practical compromise IS possible.)
Cabinet design is influential in “smoothing” out volume variations over frequency.
The speaker design can be compromised in several other ways to “flatten” its response, by implementing both mechanical and electrical modifications.
Amplifiers can readily accommodate changes in EQ of 15 dB (and more) by manipulation of the EQ circuits IF excess gain and power is available and also by means of the negative feedback mechanism previously mentioned.
Our EARS are not a reliable indicator of “good” performance. So "good" or "acceptable" performance is simply individual taste and opinion unless it is understood and agreed to be quantifiable by measurement.
We’ve neglected another key characteristic of stringed musical instruments that use magnetic pickups. The pickups themselves do not have good frequency response. Our amplifiers universally accommodate that “problem” by using pre-emphasis, which just means that the tone control component values are selected to “favor” those areas of the spectrum where the magnetic pickup is not very efficient.
(This is very noticeable, by the way, in older amplifiers. Connecting a Super Reverb, for example, to a turntable, will produce a sound that is definitely low fidelity. The pre-emphasis of the Fender amp is all wrong for the typical ceramic phonograph cartridge.)
High fidelity systems get around speaker deficiencies by the use of negative feedback, careful cabinet design and the use of multiple speakers, to extend bandwidth. So-called “cross-over networks” are used to electronically modify frequency response as well as defining the approximate frequency where the speaker driving voltage is diverted from one speaker to the other one.
Here are a couple of questions that, hopefully, can be answered by what we now know:
Q: So it’s impossible to just use one large speaker to reproduce ALL audible frequencies ?
A: No, we can use single speakers, just as in our computer sound systems, if we don’t mind amplifier inefficiencies and are willing to give up some fidelity. Some nice amplifier/speaker combinations (e.g. Polytone) have been developed over the years. The key to successful designs is that the response of a guitar is quite limited, allowing pre-emphasis in the amplifier to make up for some speaker deficiencies, and especially the use of negative feedback.
Q: Then, if small speakers can reproduce low frequencies in my computer sound system, why not use the same technique for guitar amplifiers ?
A: Many manufacturers are trying that technique. But, as we’ve shown, the most important characteristic for reproducing low frequencies is speaker cone travel – LOTS of it. It’s possible to increase the travel distance in small speakers somewhat but there are definite limitations. The Evans design compromises the travel limitations – and keeps the total package small - by using LOTS of little speakers.
Also, in Part 1, we talked about the speaker "pumping" air in proportion to it's area and displacement. The area of round speakers increases as the SQUARE of diameter. The displacement of a speaker is roughly proportional to the increase in diameter, so efficiency and volume can increase as the CUBE of speaker diameter. It takes a LOT of little speakers to approximate the efficiency of one big one !)
Many little speakers might be a practical technique using solid-state Class “D” designs, where excess power is available. The sound that these smaller packages deliver at present is not high-fidelity by normal definition but you can bet that it will get better as the market demands better speakers.
(BTW, you’ll never “hear” the power that these amplifiers are capable of producing. Hundreds of watts of power, mostly unusable by the speakers across the full audio spectrum, are required to produce a few watts of "listenable" power. It’s not really a practical problem, however, because switching amplifiers pay no efficiency penalty (as do conventional amplifiers where high headroom equals lots of waste power and heat).
Power levels in this type of amplifier have little meaning, in the conventional sense, because their power is mostly used to overcome speaker shortcomings. Comparing a 250 watt Class "D" amplifier with a 20 watt tube amplifier, one would THINK the 250 watt device would be a LOT louder. In practice, it may not even be AS loud, depending upon speakers and configuration.
In order for power measurements to be meaningful, they must be either SPL measurements (i.e. “listening” power) or comparisons between two different amplifiers of comparable or similar design.
(BTW, this option is definitely not available with a tube amplifier at this time . I know of no vacuum tube devices that can use Class “D” technology - commonly used audio tubes have frequency response limitations that preclude this.)
In this discussion, we’ve touched only on the MECHANICAL aspects of loudspeaker performance and design. There are at least as many compromises in the ELECTRICAL portions of the loudspeaker but I think that they may be a little esoteric for our purpose. In general, however, the electrical compromises in the design usually result in somewhat degraded performance, like the mechanical ones.
Anyway, I suggest that you read this for entertainment, rather than for engineering enlightenment. Hopefully it will give a little insight into the subject, though.Last edited by randyc; 10-23-2009 at 02:00 AM. Reason: clarify
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10-22-2009 05:47 PM
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Thank you: very clear and organized. In this land of psychoacoustic nuttiness, it's good to read something based on reality.
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John, it didn't feel clear and organized when I finished typing it for the THIRD time, LOL.
I don't know how to communicate well with non-engineers and I lack the ability to make a subject interesting for those who don't have a previous background.
I did try to improve my original thoughts but the result sort of came across like an OP/ED piece.
cheers,
Randy
P.S. wife was right again when she said "nobody is going to read something like that without being forced".
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Wrong. Speaking as a onetime freelance writer, the challenge is always not to provide cheap entertainment but to rigorously adhere to clarity. In my lifetime I have read some incredibly convoluted explanations of what should have been an easily digestible subject. The fault is not in the matter at hand, but in one's treatment of it. Words, as you must be aware, are slippery things, and concepts that seem easy to grasp in principal become labyrinths when exposed to persons who bring any number of irrational expectations and prior misunderstood experience to your expositions.
Think of the issue of speaker coloration: each of my guitar amplifiers sounds different when coupled to any of my speaker cabinets. Some combinations are attractive, some less so, some improve the sound of particular guitars while making others sound worse (and the ones I think sound worse may sound better to someone else with different taste or merely a different touch). As with all things not understood, a considerable amount of oral history, also known as urban legend, or downright folklore, arises to "explain" in some dogmatic way why this is so.
A person with a clear mind can sort out those elements he can control and understand, and perhaps gain a step or two on others who depend on "mojo" or, my preferred expression, pixie dust. Facts count, and any inquiring musician owes it to himself to go as far as he can (for the feminists, I came up in the generation that liked to say, "the male embraces the female" which allows the avoidance of clumsy constructions such as using the formula "he or she, as the case may be") in order to increase the percentage, say, of a performance under his control.
Back in my racing days, when we had to build bikes from street machines (except for those lucky few with access to Manxes and G50s and whatnot), theories about improving handling and horsepower were rampant. A select few had a hard-won understanding of a couple of principals: make changes one at a time, keep the changes that worked, and never forget that you are constantly stressing the machinery beyond its intended use. Those who mastered that, finished and often won. Those who depended on what sounded really cool generally finished the race with something broken.
As I've said before, you can't fall off a guitar, so in that sense the stakes are a little lower. But the same large rules apply.
This has gotten about as long as one of your treatises, to less purpose. Thanks for posting the information.
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Tell your wife not so!
And I'm not even an engineer. I might go as far as saying I enjoyed it. And yes I have other things in my life.
So if the power rating does not necessarily correspond to loudness for the amplifier what parameters are used to express this?
Thanks for your time and effort spent!
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from Part 3:
Originally Posted by keith
"In order for power measurements to be meaningful, they must be either SPL measurements (i.e. “listening” power) or comparisons between two different amplifiers of comparable or similar design."
Inexpensive SPL (sound pressure level) meters used to be commonly available and I assume that they still are. Using one of these simple instruments, one could - with care - make comparative measurements, BUT you'd have to have the amplifiers available that you wanted to compare ...
Manufacturers are reluctant to publish SPL data for a lot of reasons, mainly because they are STRONGLY dependant upon the speaker (cheap speakers usually have poor SPL characteristics but cheap speakers are frequently the ones that manufacturers select to keep cost down). It's easier for the manufacturer to just specify an output power (watts) number .
If you want to compare amplifiers of similar design, things are simpler PROVIDED THAT THE AMPLIFIERS ARE NOT CLASS "D" DESIGNS. These amplifiers are all about the speaker configuration and speaker efficiency and published power levels have very little to do with performance. So far the manufacturers are keeping quiet about meaningful specifications.
Comparing a vacuum tube amplifier with a certain speaker configuration against another vacuum tube amplifier with a similar speaker configuration and similar fundamental design can allow the use of output power ratings for valid comparison.
Ditto for solid state designs that are not Class "D". If the speaker configuration is similar you can use output power as a comparison tool, making the assumption that circuit configurations are not dramatically different from various manufacturers.
Some manufacturers in the past have misled us by changing their definition of "output power" so be cautious. Especially be careful when you hear (or read) terms like "music power" or "peak power", those terms aren't very meaningful without qualifications being established (be assured that they will reflect most favorably on the individual manufacturer's product). To be fair, I haven't seen this trick in a while ...
The standard, from AC power supplies to millimeter wave amplifiers, for power measurement is the RMS watt, with the load impedance specified. Audio devices normally include % distortion level (and sometimes frequency).
e.g. 50 watts rms into 8 ohms at 5% distortion (1 kHz)Last edited by randyc; 10-23-2009 at 02:20 AM. Reason: add distortion qualification, misspell correction .. add "meter" ro SPL
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Randy, thanks for the articles.
One thing I don't understand is why you make a distinction between class D and other (most commonly AB) classes. So long as all outputs are measured consistently, the class of operation should be immaterial.
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I'm wondering that, too. Class D's often post impressive wattage, like Acoustic Image's Clarus +'s 1000W@2ohms. Are you saying the numbers lie?
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Sorry guys, my ten minutes typing just went into Neverland AGAIN. And for some reason I cannot save ANYTHING on this site, it's all gone. And since the IT tech (my wife) can't solve the problem of my frequent internet disconnects .... well it's a spiraling catastrophe
Will take the answer over to Word, type it there then come back and cut and paste. TTYL
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When I write an involved post (such as one I did at another forum on rewiring a Sheraton II through its treble f-hole!) I compose it in Word, then cut and paste when I'm ready to post. I also save such as Word docs, so that, when others want a copy, I can e-mail it as an attachment (if the recipient also has Word, of course).
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OK, I went back to the physics textbook on this question and ended up with four pages. Let’s see if I can simplify it adequately to answer in a manner that satisfies those who asked it:
Q: Why make a distinction between Class “D” solid-state amplifiers and more conventional amplifiers, isn’t output power the same, regardless of what device is generating the power ?
Absolutely – if an industry-wide technique is used to make the measurements, accurate determination of ANY amplifier’s ability to generate power is easy.
BUT, what one is measuring varies, depending on how the measurement is made. The “best” technique (arguably) was pioneered by Hewlett-Packard with their 435 Power Meter. This technique doesn’t depend on measuring voltage, current then performing calculations to derive the power. It’s more straightforward and gets back to first principals. A tiny resistive element in the power meter head is heated by the power applied. The amount of heat is directly proportional to power and is displayed directly on the instrument face.
No speaker, unhappily, behaves like a power meter. Speakers are not nice, resistive loads so “loudness” can’t be predicted by amplifier power, far from it. A LOT more information must be known before attempting to arrive at that difficult answer.
And loudness is what we’re really interested in, not power.
When I said that the power of the Class “D” configurations had no meaning, perhaps I should have added the words “since that power cannot be translated into meaningful volume levels to the listener”.
Further, I should qualify that I include only amplifier/speaker combinations in that statement. (I would expect that if I connected one of those tiny little beasts to my old Altec Voice of the Theater cabinets, that the result would be something close to the sound I used to obtain with my Phase Linear 1400 watt amplifier connected to them, i.e. earthquake levels.)
My topic was loudspeakers and what I was attempting (clumsily) to point out was that these tiny little Class “D” amplifiers are universally associated with tiny little speaker systems. The situation reminds me of the worm constantly eating its tail (Ouroboros?): because the desire is to produce a compact, light structure, small and inefficient speakers must be used which require HUGE amounts of power in order to drive to a listenable level, while decent bass response is STILL unobtainable due to the travel limitations of the tiny speakers.
This could not have happened ten years ago – only the advent of Class “D” technology allows the production of high power amplifiers in such a small size, a marvelous achievement in itself. But speaker technology lags far behind ! We haven’t yet derived the benefits of the amplifier technology IMO.
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I've noticed that everywhere you look, mention of the ZT Lunchbox includes the rating 200W. You have to dig in their web site to see this is one of those "music power" ratings, and that it is 130W RMS. Originally Posted by randyc
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Good catch, BDLH. I thought that the days of salepeople writing "specifications" were over, darn it ! It's a good thing that people like you and me are around to keep 'em honest. Obviously, the meaningful number is the RMS one.
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By the way, on the subject of small speakers and bass response, check out Phil Jones' bass cabinets: Bass Amplification | Phil Jones Pure Sound
He uses 5" speakers exclusively (but up to 32 of them at a time!). They are of his own design and can go down to 35Hz.
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When I read about a new amp, I wonder "how loud is it?", or which amp is louder, A or B?
But this reminds me of watching TV. You're watching late at night with the kids asleep when a commercial comes on that so much louder than the movie that you have to jump and mute it. But then you see a segment on TV where they take your complaint and measure the DBs to find: the commercial isn't any louder! What's going on? Well, the commercial's sound is compressed into mid-range frequencies to which our ears are more sensitive. I guess this is what is meant when there is talk of the "psycho-acoustics" of sound. Some guitar amps use this same idea: they're midrangey compared to "hifi" amplification.
l
So in the end, I think the only thing to do is listen to the amp itself.
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BDLH, you grasp this stuff very well. Although I was going to post these to illustrate another point, these curves demonstrate your point too !
OK guys, be patient with me for a minute, I know that you're not used to looking at this stuff. The two curves above are computer simulations of the same vacuum tube guitar amplifier, one that I previously posted a month or so back. The curves represent the frequency response of the voltage across the speaker terminals. In other words, if we attached a voltmeter to the speaker terminals, connected a signal generator to the input and then made voltage measurements at every frequency, we could make a plot (curve) like these ...
One of the curves, the top one, is very "peaky". That's the effect of the amplifier driving a loudspeaker ... the impedance of the loudspeaker varies with frequency, so the voltage also varies. Additionally, the output section of the amplifier isn't very flat either and that adds to the "peakiness" of the response.
Now look at the lower plot, which is nice and flat. It's exactly the same amplifier, adjusted exactly the same way except that a negative feedback loop has been added. (FYI: feedback consists of 150 pF capacitor in parallel with 8.2 k resistor, this circuit is connected between the speaker and the cathode of the second stage preamp.)
Miraculous, yes ? I'm thinking of starting a new topic entirely about negative feedback but it's a mathematically complex subject, so .... we'll see.
If one looks at the left side of both curves, the predicted voltage across the speaker is shown. There is a drastic difference between the peak voltages between the two curves. Mother Nature and Sir Isaac Newton never allow us something for nothing. Sir Isaac's "conservation of energy" laws express this stuff in physics terms but we can see it here graphically.
The amplifier without feedback has very high voltages but over a narrow frequency range. The amplifier with feedback has low output voltages but over a wide frequency range. If one were to integrate the voltage, or power, of the two amplifiers over frequency, as Sir Isaac would point out, one would find that both amplifiers produce exactly the same power, the only difference is the way that it is distributed !
Getting back to BDLH's comments about tv commercials, here is his point, made graphically:
The flat response represents normal tv programming, music, special effects, the whole works. The audio HAS to be wide band, have a good frequency response, to faithfully reproduce that wide variety of sounds. Using our example, the speaker voltage is slightly over 10.
Cutting to commercial, all that's needed is enough fidelity to reproduce a little music and MOSTLY the pitch-man/lady's voice. The same power is used but it's concentrated into a very narrow band so it's way LOUDER ! Our example, without feedback, shows a speaker voltage over 300 ! A difference of almost 30 dB and one the human ear can readily hear.
cheers
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Yes, I looked at that website the first time the subject came up. They use terms like "knowledge base" and "white papers" apparently to give sort of an engineering spin to things. Interestingly, the only "quote" from any user that I can find is that guy "anonymous". I don't trust that guy; he says EVERYBODY'S products are great. Originally Posted by BigDaddyLoveHandles
"SHOW US THE DATA", that's a simple enough request.
There is nothing on that web site that contradicts anything said here. It's just "spun" so that up becomes down and left is right. Like the old saying about writing software, "it's not a BUG, it's a FEATURE".
Anyone can argue with ME, no problem. Arguing with Sir Isaac is a different propostion and there's only one guy that does it, Charles Darwin, who is interred right beside him. As Mister Darwin's son said at the interment, "They will have such interesting conversations".
PS: just looked at that website again, my word ! They have their own version of "Monster Cables", how tacky Whoever does their writing sounds like the same guy that writes tv commercials for chiropractics, product liability lawyers and bail bondsmen.
Last edited by randyc; 10-23-2009 at 05:54 PM. Reason: add PS
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My favorite was always, "Failure is not an option: it's bundled with the software." Originally Posted by randyc
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More on speaker performance versus speaker size
In an earlier part of the discussion, I made the assertion that larger speakers moved more air in proportion to the cube of their diameter. Using this relationship, the difference in “loudness” between a 5 inch speaker and a 15 inch speaker would be about:
10 x Log[(15/5)^3] or about 14 dB
I took a look at a cross section of commercially available speakers, both 5 inch and 15 inch, as a sanity check of my comments. I looked at the manufacturer’s data sheet of measured performance for low-cost and high-cost speakers, ranging from about $20 up to about $300. Interestingly, the big difference in price is not reflected in actual performance, like many other things.
A quick comparison of sound pressure level measurements (SPL) shows that all of the 5 inch speakers are roughly 86 dB/W/m (which is a relative measurement parameter that can be used to compare “loudness” of various speakers). The same brief comparison of 15 inch speakers indicates that they all produce about 96 dB/W/m – they are some 10 dB louder than the 5 inch versions.
So our rough estimate of 14 dB is close to the 10 dB actually measured. I’d like closer agreement but this is certainly acceptable, given all of the presumptions that I made to arrive at efficiency estimates.
All of the speakers had a stated frequency response of about 30 to 3000 Hz. That immediately got my attention and posed the question: how can a five inch speaker have the bass response of a fifteen inch speaker ? After all, haven’t we already examined this in our discussion by comparing the cone travels of small and large speakers?
I went back to the manufacturer’s data sheets and looked at the actual measured curves of sound pressure levels as a function of frequency. I found that the measured performance of the 5 inch speakers didn’t accord with the published claims. The low end of these speakers were shown to be around 150 Hz, NOT 30 Hz.
Further, I noted a couple of interesting notes on the data sheet, located just below the data curves. The notes read: “due to testing limitations, response below 200 Hz is not an actual representation”.
I’m not real sure what that’s supposed to mean, it would have been nice if they told us WHY. More importantly, where did the information come from that was used to produce the “response below 200 Hz” ?
Imagination ? Wishful thinking ? An estimate based on computer modeling for which an engineer is willing to assume responsibility ? and so forth … this is one weird situation.
There certainly CAN be valid reasons for their omission. If so, these reasons should be clearly stated and the basis for the published “specification” explained. Otherwise, how can one intelligently select a loudspeaker for a specific application ?
There’s more detail available in the SPL curves that is interesting, we’ll save it for later.
In the next episode of this soap opera, we'll perform a brief design exercise, select some speakers and make some performance estimates.
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OK, let’s pretend that we’re working for a company that is thinking to design/build a compact audio amplifier combo and our management has asked us to make some engineering estimates of performance by … say tomorrow morning. No time for computer simulations, no time for performing measurements, we just need to suck it up and crank out some preliminary numbers for management to use for costing/marketing purposes.
The actual amplifier design, although not trivial, is a predictable effort so we can start out with a target output power that won’t be difficult to meet, say 100 watts. Our target weight is 25 pounds and experience suggests that the amplifier and cabinet will weigh about 10 pounds. Now we have to deal with those pesky speaker specs, coming up with a speaker configuration that weighs no more than 10 pounds and then making a performance prediction …
Maybe we’ll make up a comparison table, listing some speakers by size, sound pressure level, frequency response and cost, like the following one:
Part No. SPL size freq range weight cost
Abc123 86 5 inch 100-3000 2 lbs $24
Abc234 85 5 inch 130-3000 2.2 lbs $28
Abc345 84 5 inch 120-3500 3 lbs $40
Bcd123 90 10 inch 80-3500 9 lbs $75
Bcd234 91 10 inch 90-4000 11 lbs $90
Cde123 96 15 inch 30-3000 17 lbs $130
Using the weight requirement to come up with speaker configurations, we need a combination that is around 15 lbs and these would work:
A: one 15 inch speaker, 17 lbs, SPL = 96 dB, $130
B: one 10 inch speaker and one 5 inch speaker, 13 pounds (the 11 lb speaker + 2 lb speaker), SPL = 92.2 dB, $114
C: one 10 inch speaker and one 5 inch speaker, 12 pounds (the 9 lb speaker + 3 lb speaker), SPL = 91 dB, $115
D: five 5 inch speakers, 10 lbs, SPL = 93, $120
If we have a target MARKET in mind, we need to be able to make a rough comparison with a popular similar product that services that market. The management people won’t understand technical specifications but they should be able to grasp simple comparisons J
We’ve determined that our target market and target competitor will be the Shrive-Boonley model “Wharf-rat”. This is a vacuum tube amplifier of modest performance but a rich heritage. Market/comparative research indicates that this amplifier has an output power level of 50 watts RMS, it has a single 12 inch speaker that we’ve determined has a SPL of 94 dB (we know this because we’ve peeked inside the cabinet, got the part number of the speaker and looked up the data sheet on the internet).
A little bit of calculator crunching gives us a working performance goal, we determine that the listenable volume level of the Wharf-rat is 111 dB/w (the speaker SPL is referenced to a one-watt level, so we convert the amplifier power to the same units and add the two). This means that the volume is 111 dB greater than a bare speaker with a power level of one watt applied to the speaker terminals.
We can now use this number and the speaker SPL estimates that we’ve already made to find a configuration that “competes” with the Wharf-rat. This exercise will permit us to refine the estimated output power of our amplifier-that-yet-needs-to-be-designed.
The power level of our amplifier is going to depend on speaker efficiency which can be estimated by using the competitor’s 111 dB/w level and subtracting the predicted SPL of our various cabinet configurations. That will result in amplifier power, expressed in the terms of a ratio, in dB, compared to one watt:
Configuration A: requires amplifier power of 111 – 96 = 15 dB/w or 32 watts (LESS power than the Wharf-rat because of the 15 inch speaker configuration, which is more efficient than the 12 inch speaker of the Wharf-rat.)
Configuration B: requires amplifier power of 111 – 92.2 = 18.8 dB/w or 76 watts (the ten inch and five inch speakers are less efficient than the 12 inch speaker in the Wharf-rat)
Configuration C: requires amplifier power of 111 – 91 = 20 dB/w or 100 watts
Configuration D: requires amplifier power of 111 – 93 = 18 dB/w or 63 watts
OK, now we’re getting somewhere. We can make some cost estimates now for the AMPLIFIER based on different power requirements. Different output power levels imply different overall gain and especially, different output semiconductors.
Let’s say that we’ve gone through that exercise and we’ve determined that the amplifier fixed costs are about $45 and that each additional watt over … say 30 watts, will increase cost at the rate of $1.60 per watt. Again, without detailing the calculations, we can prepare the following chart to present to our management tomorrow morning:
BASELINE PERFORMANCE IS SHRIVE-BOONLEY WHARF-RAT
Configuration A meets competitor specs wt = 27 lbs cost = $178.20
Configuration B meets competitor specs wt = 23 lbs cost = $232.60
Configuration C meets competitor specs wt = 22 lbs cost = $271.00
Configuration D lo freq response not OK wt = 20 lbs cost = $217.80
Management can now, using this chart as a tool and consulting with the marketing staff, determine which configuration is the desirable one. Basically, they will estimate how much a customer is willing to pay for each pound of weight saved and whether any performance compromises are acceptable.
After this has been determined, a pricing exercise takes place, which can be VERY complicated, determined by desired profit margin, return-on-investment, capital equipment depreciation, labor rate projected increases, overhead changes, component cost increases, interest rates on loans …. Well, you get the idea, it’s HARD. Engineering personnel provide the bulk of this information and usually participate in final price decisions.
In this particular example, interestingly the configuration with the largest speaker was also the lowest price configuration. That wasn’t intentional – all of these figures were plucked out of the air – cost and weight figures, anyway. But do note that the multiple small speaker configuration didn’t meet performance goals. That’s based on the little bit of speaker data sheet browsing that I did earlier this evening.Last edited by randyc; 10-24-2009 at 02:24 PM. Reason: rev spkr wt from 10 to 15 lbs (error)
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Grant Green, What is This Thing
Today, 01:59 PM in Ear Training, Transcribing & Reading