What about those Frogs? They listen to single source, high efficiency designs with mono SETs....call me a buzzkill...but I actually like separation, panning, ect.... |
Many good points here gents!
I do not agree that all amplifiers sound "the same" at one Watt. However, most amps will operate in Class A at low output, and definitely sound their best there - it may well be that they sound less different at one Watt.
I would add that the laws of physics define a relationship between low bass limit, efficiency, and box volume. So for a bass woofer, the designer who wishes to increase efficiency must either compromise bandwidth (low frequency limit) or make the box bigger.
Cheers,
CRP |
Thanks guys. I'm glad you learned from them and that my writing wasn't too confusing.
Best regards,
Roy |
Yes, thanks for all the informative posts! |
Roy aka gma@pcisys.net: Thanks for your contribution regarding speaker design and the way that you worded it. It was very well put and easy to understand. I'm glad that you have the ability to speak in terms that the average audio enthusiast can follow along with. Your post was a great contribution as far as i'm concerned. Then again, it agreed with what i've been trying to say, so it's no wonder that i like it : ) Sean
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Except that goes against the very many audiophiles who report that each amplifier is different in their retrieval of low-level detail, which definitely lies below one watt even on 90dB speakers. And was it Audio Note who came up with the phrase "the first Watt is the most important."??
I'm sure the designer heard what he heard, but perhaps the explanation for what he heard lies elsewhere-
-Perhaps his horns do not respond very well to low-level changes in music- changes in the swing of the rhythm or changes in the way a note is attacked or released.
-Far more likely, though- the interconnects and speaker wires used weren't very clear at those small signals (something I and others have experienced over and over again for more than 15 years).
-Source gear often fails in the same way.
But he is right- higher efficiency speakers relieve amplifiers of a lot of stress. But I cannot believe they all sound the same at one Watt.
What is anyone ele's experience?
Roy |
I talked to a horn speaker mfgr. He told me his speaker contributed at least 80% of the sound because amps sound virtually identical at the 1 watt used to run the high efficiency horns. Meaning, the lower power, the less effect amp qualities can have on make / breaking the system. |
Richard, everyone above makes good points.
There seem to be three advantages to seeking high sensitivity during the design of any speaker system:
--to use lower-powered amplifiers (= a simpler amp, which is often more linear/more transparent)
--to reduce voice coil temperature swings (sensitivity decreases as the voice coil's impedance climbs with temp, a form of "power compression")
--to be able to play it more loudly (assuming it can handle the power AND has the excursion).
Personally, I think #2 is the main "hi-fi" reason a speaker designer should seek the highest sensitivity raw driver for a given task.
There are several disadvantages/obstacles to increasing a driver's sensitivity:
--no matter how large/powerful the magnet, we can only get a finite amount of magnetization into the pole piece, located inside the voice coil.
--about half the moving mass of a cone or dome driver is in the voice coil. All the high-sensitivity woofers and mids have very short voice coils, to reduce their moving mass. For a woofer, that shorter coil reduces the maximum stroke available, which limits loudness and low bass excursion (think Lowther). A mid driver that has a short stroke forces the use of a higher-order crossover to keep it from running out of stroke, and that crossover always screws up the time coherence.
--the lower the moving mass, the more compliant that driver's suspension must be, to keep the driver's frequency response flat before a crossover is even applied. And to let the driver go just as low as its lower-sensitivity competition. Except there's a limit as to how compliant the suspension can be manufactured, for consistency from unit to unit and to keep the voice coil centered.
Most high-sensitivity speakers do not go below 45Hz, flat, because of their suspensions' intentional lack of compliance- done to limit the stroke of their short voice coils. They do not have to be "boomy" however- that's the result of poor engineering somewhere in the design process, not sensitivity.
If multiple drivers are used to increase sensitivity, there are many problems:
-little chance of time coherence.
-room positioning becomes critical, as off-axis, the tone balance and time-coherence (if any) are unpredictable.
-more reflections off the larger cabinet face.
The highest sensitivity, high power-handling drivers must be carefully assembled. One of the biggest decreases in sensitivity comes from widening the voice-coil gap for sloppier, faster assembly and out-of-round voice coils. This is why there are a lot of 83-87dB designs out there.
The best woofers, made by larger manufacturers, with high sensitivity and low distortion are from PHL Audio and Volt Loudspeakers. However none of those are "ideal"- some are not flat in tone balance, and others do not respond to small signals.
There is the 100dB-sensitive Stage Accompany 6" ribbon tweeter, if one could afford it (>$600 each). Regardless, finding a mid driver to mate to it seems impossible, without loading the SA down with resistors to turn it down (reducing its sensitivity).
In a complete speaker system that uses only a single driver per frequency range, the upper limit to sensitivity is now 90-91dB, if you are to have any useful bass response, a cabinet that's not too large, and wide dispersion.
Sealed-box woofer boxes are smaller than ported woofer boxes, for the same low-bass extension. To go that low, they have longer voice coils- they need the stroke since there's no port. Which means more moving mass, thus less sensitivity.
Sealed-box woofers have softer suspensions than ported woofers, so the sealed box itself can become the primary "spring"- a more perfect suspension than any man-made one, for lower distortion and better response to very soft signals.
Sealed box designs were necessitated by the onset of stereo reproduction, as no one really wanted TWO big Altec or E-V speakers in the living room back in the '50's, or could afford two. When those sealed boxes started selling in big numbers, that was one impetus for amplifier companies to increase power outputs. The other was "marketing".
Yes Richard, you did open a Pandora's box. Shame on you.
Best regards,
Roy
Green Mountain Audio |
Aroc asks an interesting question. I'm hardly an expert but as I've come to understand it, the first speakers were actually extremely efficient. The early years of vacuum tube amplification required efficient single driver baffle mounted speakers. Musical, but pretty crummy frequency response. Later came the "great" multidriver high efficiency horn speakers (Klipsch's, Altec's, JBL's, etc).
The less efficient sealed box designs utilizing multiple drivers and power robbing filter components happened to come at a time when we saw higher output tube and transistor amplifier designs. Efficiency was no longer a big deal. The culmination of this was probably the small closed box mini-monitors that utilized complex power hungry crossovers and a sealed box to create "bass" from much smaller than expected drivers. (I played with these designs for awhile in the early 80's. The crossovers were complex and the resistor networks in them often became quite warm to the touch at moderate listening levels. Lots of the amplifier power was used to warm the room! I recently acquired a blueprint copy of the KEF 101 crossover from the factory and that extremely complex 2-way crossover included 25 components including a relay and an LED!)
Vented box designs promised better efficiency with even lower bass. (Unfortunately it's not always well executed.) That has sort of made them the predominant design for the last couple of decades. Now, with audiophiles falling into various camps that favor everything from SET's with single digit wattage to solid state designs with nearly 4-digit outputs, speaker designers are free to create what sounds best to them with the knowledge that proper amplification can be found for nearly design.
Sean is right, unless you're running a SET amp, choose any reasonably efficient speaker. Other than that there don't seem to be an absolute pros and cons to high efficiency. If your amp is unhappy with low impedances, checking the impedance curve of a speaker is important before buying. Again, I'm certainly no expert but those are the only numbers I pay much attention to. I buy what I enjoy listening to. |
This is a VERY technical question and involves the engineering trade-offs between transient response, bandwidth, driver excursion, cone break-up ( distortion ), power handling, etc... Suffice it to say that if one could achieve "perfection" i.e. all of the desirable traits that we look for in hi-fi with high efficiency, the designer would be a genius that knew how to circumvent the laws of physics. As such, engineers and manufacturers weigh the balance in what they are looking for and design according to what they have available to achieve those goals at a given price point. As such, a medium efficiency speaker offers the best compromise in several areas. On top of that, they are also the most commonly available in terms of selection of drivers, so that is what we end up with as a majority. As others have mentioned, either design can work well in a system IF that system is set up to work as a team. Like anything else though, the team is bound to have a few "star players" ( high points ) and a few sore-spots ( weaknesses ) regardless of the efficiency.
My suggestion is to look for speakers that are at least "reasonable" in efficiency ( 88+ dB's ), offer a stable impedance that is 6 - 10 ohms nominal and will cover the frequency range that you want in a room the size that you'll be using them in. Then again, finding all of these features in one package at a price you can afford is "almost" like having your cake and eating it too : ) Sean
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Let me shoot this question. Theoretically, why would the first engineers to design a low sensitivity/efficiency (???) (like 84dB/w/m) when ligh sensitivity/efficiency (??) speakers were available? Considering the fact that the first viable amplifiers were diminuitive (3W SETs, etc) naturally speakers that designed around those amps. Since all things being equal (and they never are) a 50W or 150W amp generally costs more than a 3W or 8W one. What would be the driving (pun not intended) reason to reduce sensitivity/efficiency (??) in a new loud speaker design.
Flatter response over wide frequency range?
Cheaper construction or cheaper R&D costs?
A different "sound?"
For example consider a $75-200 loudspeaker from Circuit City. (Essentially a shoe box with some drivers). Why should these designs be 87dB/w/m. Why not make then 97dB/w/m? Since someone that price conscience about loudspeakers probably can't afford a decent amplifier (either SQ wise or power output wise). You'd think the HT crowd would be all over high sensitivity/efficiency speakers, since you could drive 5 our 7 speakers in a big room with just about any A/V receiver.
Tubes vs. SS. Analog vs. digital. MC vs. MM/MI. Active vs. passive. 3way vs. 2way vs. 1way. I realize everything is a trade-off. And no matter what the technology or features, there are generally great executions of all of the above. And it's more about the end result than any specific technology. There are no absolutes. No "magic bullets."
This is just something I've always wondered. What do low sensivity/efficiency speakers "bring to the table" so to speak? |
Richardmr, from my humble knowledge and experience, I would have to agree with Von Schweikert on there answer. Your amp and speakers will probably sound simply fabulous. |
Thanks, everyone, for your responses so far. It seems that I've opened Pandora's Box a crack.
Matchstickman - My 100 DB's are 8 ohms nominal and 10 ohms max. They are also 100db at 1 watt at 1 meter, in room.
My amp is a Rogue Push/pull KT88 Tube at 60 watts. Do you think it will be a good match? Von Schweikert says yes. |
I have been researching Amps and Speaker for the last few months and I would like to pass along some info here. High efficiency does not necessarily equal high sensitivity. A high sensitivity speaker may still not be efficient and it might require lots of power whereas a low sensitivity speaker might be highly efficient. SET amps like/need high sensivity speakers simply because the low wattage of SET amps cannot be heard otherwise unless they are running through high sensitivity speakers; however, what makes a high sensivity speaker efficient is the impedance swing. An 8ohm speakers that stays true and close to 8ohms as possible is an efficient speaker. Let me clarify. It takes 300 watts at 4ohms to equal the sound of 8ohms at 150 watts. SET amps are not what I would call efficient. This being the case, if the SET is connected to a speaker that swings from 8ohms, down to 4ohms, some of the frequencies will be lost, probably the lower end. This is because the SET will have to push twice as hard to pump current when the loads swings down to 4ohms. Do I have you confused? The SET needs a speakers that is steady; whether it is a steady 4ohm, 8ohm, or 16ohm, or whatever. So, in essence, you could have a speaker with an 86db sensitivity rating, but with a nomimal, steady, 8ohm requirement and therefore be efficient.
This info is why I have chosen to pick out my speakers and then pick out an amp that goes with my chosen speakers. It should work out for me.
Those Von Schweikert DB-100s, what is their impedance swing? Do they have a nomimal rating or do they go between 4 and 8 as most speakers do?
I am still a rookie at this, but I think I am somewhere in the ball park. Experts, how close am I? |
Phasecorrect is right on! |
I wouldnt worry too much about it...find a speaker u like...then mate with appropiate power...as much as people want to make it...this is not rocket science....I also agree there are no real advantages to hi-efficiency designs other than low power/tubes can be used... |
Speakers that are high efficiency ( 95 - 96 dB's and up ) tend to sound punchier aka "more dynamic". This is even truer for "ultra high efficiency" designs ( 100+ dB's ). Having said that, most of them also tend to be bandwidth limited and lack the ability to handle gobs of power / play at sustained high volume levels. They tend to use inexpensive low mass* drivers that break up and distort if pushed hard. As such, the benefits of high efficiency are only good if used at lower power levels. As Unsound said, these are pretty vague generalizations, but ones that i've come to realize via past experiences. There are exceptions to every rule though and more than one way to skin a cat. Sean
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* the more mass you have in a driver, the harder the motor must work to push it, hence a loss in efficiency. |
Please take this with a grain of salt, as these are gross generalizations. High efficiency speakers may be more suceptible to noise infiltration, may have greater impedance swings, and may have looser bass. I repeat, these are gross generalizations. |
You cannot separate the loudspeaker from the amplifier that drives it. There is nothing in either approach (low power/high efficiency vs. high power/low efficiency) that makes one inherently better. Outstanding musical performance can be achieved by both methods. |
Higher efficiency speakers have no edge sonically. Their main benefit being that they are easier to drive, so they are available to be used with a wider range of amplifiers. The less efficient a speaker, the more careful you have to be in mating a amp for best sound. In general, there are good and bad sounding speakers that have high and low efficiencies. So the efficiency rating has nothing to do with sound quality, only amplifier selection really.
An analogy: look at the speaker efficiency rating as you would the miles per gallon rating in a motor vehicle. A vehicle with a MPG rating of 28 is not necessarily a better vehicle than one with a rating of 20. It may not even go further, depending on the size of the gas tank (amp). A higher MPG rating (efficiency) and a large gas tank (amp) will take you farther (max spl), but may or may not be, in comfortable style (sound quality).
I hope this was helpful.
Regards,
John
BTW, they usually save you money on amps. Because you won't need much to drive them, even if you don't go the SET route, you can buy a company's less expensive 60 watt amp, instead of the same company's more expensive 300 watt amp. |
If you have other speakers that do not reveal the deficiencies of your system, they are also not revealing part of the music. When you reveal all, you also get a more revealing musical experience. Some cannot tolerate this, and seek a more "forgiving" speaker. Each person needs to fill his/her own music needs.
When playing records, the efficient speaker usually shows up more record noise than other types, because it does not mask as much. |
