"Power hungry" speakers

Bemopti: Right on. The more complex the crossover, the more "power hungry" the speakers will be. Not only are such designs "sucking up power", they are "eating signal" at the expense of losing micro-dynamics and detail. After all, there wouldn't be any power there if the signal didn't call for it. Losing that power means losing signal. Thermal inefficiency / power loss due to heavy parts count in the crossover is directly related to "lifelessness" in presentation with a lack of liquidity. These are speakers that measure great, but sound boring.

In my experience, many companies that make their own drivers and farm them out to other companies should stay away from designing / building / marketing complete assemblies. Dynaudio, Morel, Focal aka "JMLabs", etc... are prime examples. These companies all make good to excellent drivers, but lose sight of what music is and try to make a product that is technically excellent. In the process, their efforts to design something that is "worthy of their technical excellence" and "design prowess" ends up stripping the music of its' "soul".

The above "thermal inefficiency" comment should NOT confuse speakers that are simply less efficient with designs that have too many passive parts between the amp / drivers. Sean
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I'm not familiar with Sonus designs at all. The only thing that i can think of is tonal balance. A speaker with a very laid back or semi-sunken response will never sound as "loud" as a speaker with a more forward ( or even "flatter" ) response. From what i've read, the Sonus speakers have a rather laid back / soft presentation. Sean
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Capacitors have varying levels of dielectric absorption and thermal losses as frequency is varied. Their transfer characteristics ( linearity ) can be measured and compared over a given frequency range. None of this is new technology and studying these factors along with many others is what have led to the breakthroughs in higher resolution / lower loss circuitry. This is part of why newer gear has the potential to sound better than older gear i.e. improvements in passive parts. Some capacitors that were believed to be "excellent" in the past are actually quite horrid in performance. Most electrolytics are amongst that group along with several others.

In order to get around this problem, some have experimented with using two different types of capacitors wired in parallel i.e. "bypasses". The non-linearities of one cap offset those of the other, summing together to improve the transfer characterstics of the circuit on the whole. This can be a VERY tricky business though as you can end up with two ( or more ) non-complimentary distortions, resulting in even poorer performance. This is why some folks say that "bypasses work well" and "bypasses create other problems". Sean
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Start looking at bass transients into low sensitivity and / or low impedance and / or highly reactive loads and you need hundreds upon hundreds of watts. Combining all of the above will mean that you need a MONSTER sized amp to do the job right. This is part of the reason why high powered "digital" or high effiency amplifier designs have been finding their way into more and more systems. They can work quite effectively as sub amplifiers. There are some simple tricks that can be done to these amps that make them even better for this purpose. Sean
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I assume that you're talking about Apogee's based on your impedances and mention of ribbons. Having said that, you state that the speakers are 76 dB's yet only a few amps could drive them beyond 70 dB's. How is that possible? It would require less than 1 watt to do this based on your own figures. Was it due to "protection" circuitry kicking in? If so, you need an amp without protection circuitry.

Other than that, i agree that a low bias output stage / high efficiency amp works very well with loads like this. Due to the lack of duty cycle that the amp reproduces / reduced current & heat involved, some of these newer designs truly are an "answer to audio prayers".

As far as 95 dB's go, i consider that to be a "moderate" listening level. While some recordings ( acoustic based music, etc.. ) sounds very good ( even "loud" ) at that level, it just wouldn't cut it for large scale Classical or hard Rock music. Bare in mind i'm talking about spl's as measured at the seated listening position, not one meter from the speaker.

El: My main system is actively crossed. No capacitors between amp and speakers other than the speaker cables themselves.

My Brother's system was previously quad-amped using passive networks a while back. He is now actively crossed and the passive networks came out of the system. The difference between active and passive was staggering to say the least. Bare in mind that the passive networks were VERY simple first order designs.

Sean125: The chart that you provided doesn't take into account the speaker going into compression and is also based on 1 meter spl's. Taking measurements at the seated listening position would alter those readings DRASTICALLY.

What others may find interesting and i find to be "coincidental" is that the mains in my HT system are rated at 87 dB's @ 1 w @ 1 meter. I was running these with two amps and passively biamping. I had 400+ wpc up top and 500+ wpc on the bottom end. When running these in two channel mode, even with this much power, i could drive the amps into saturation. Moving to a single amp that is rated at 1200 wpc and clips at slightly over 1450 wpc gave me the headroom that i needed. Not only does the system play louder, it does so in a cleaner fashion.

With that in mind, those interested in being able to sustain high spl's and / or obtain very dynamic peaks might want to print out and save the chart that you provided. They should also consider that they will be running two speakers when in stereo mode, so you effectively double the spl level for the same rated power output. As such, things are looking better in terms of trying to obtain clean dynamic output with lower power. Only problem is that most speakers WILL go into noticeable compression when you start throttling them.

The mains in my HT system are 4 ways with 5 drivers, limiting the power and bandwidth that any given driver has to deal with. If you want to "crank" the system and maintain linearity, you either have to use this type of approach ( multi-way with large surface area ) OR you can go with fewer crossover points, but use more total drivers i.e. two way line arrays, etc... Line arrays tend to maintain spl's better into the distance, so they are well suited to situations where you have a longer rooms and / or further listening positions.

Lots of variables in selecting speakers and there are quite a few different ways that "linearity" comes into play. Sean
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El: active crossovers betweem preamp and amps, not passive. Sean
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I could go on a tirade here about how passive crossovers "suck" ( both power and sonically ), but i've already pissed off enough people lately. It's bad enough that those with vented speakers don't like me, i don't need to add those with sealed, TL's, etc... that are passively crossed-over to that list. The amount of people running sealed & stuffed / actively crossed speakers is a pretty slim percentage of all audiophiles out there, so i'll stop while there are at least two or three people that don't want to tar and feather me : ) Sean
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Op-amps can sound quite good when properly selected and implimented. Obviously, there are vast differences amongst Op-amps. Stereophile ran a very interesting article on the subject a few years back. Sean
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Some distortions are not "additive" in nature i.e. they aren't creating / adding additional output on top of what the original signal had. This means that losing some ( any portion ) of the signal also equals to distortion. Since more power = more heat and more heat = thermal loss, you end up with more distortion from the speaker.

On top of that, lower sensitivity designs have to move more air to produce the same amount of air that a higher sensitivity design does. In order to do that, the driver has to make longer excursions. The longer the excursion that a driver takes, the more distortion that it will generate. Another side effect / drawback is that a longer excursion will also generate more reflected EMF ( electrical "back-pressure" ), making it harder for the amp to control & load into the speaker.

Besides those primary factors, the electrical characteristics of a speaker change as the power levels are raised. Depending on what power level / spl range a speaker was tuned or "voiced" at, one can end up running the speaker in a range where it is less accurate / running out of the linear pass-band of operation. Then again, the reverse is also true of a speaker that was tuned to operate at higher spl's being run at / not working as well at lower spl's.

As a side note, vented systems will suffer from what becomes a "roving resonance" depending on the transfer efficiency of the port itself. While ALL speakers end up raising their frequency of resonance as you drive them harder, "straight" ports or ports that are only flared on the exit side are much more sensitive to this phenomena than a double-flared port or passive radiator design. Passive radiators have their own problems though as they have the moving mass of the drone cone itself to overcome. This problem becomes more apparent / harder to deal with as spl's are raised. Since greater mass is harder to accelerate and / or stop rapidly, trying to do so with the longer excursions / more inertial momentum compounds the problem. This situation also occurs with sealed designs, but not as severely. That's because the pressure or "air spring" inside of a sealed box remains consistent regardless of the drive levels applied.

Other than that, most all of my speakers are sealed and of lower efficiency. This means that i need pretty sizable amounts of power to obtain good performance. On top of that, most are also low impedance designs, meaning that i need even more power to get them moving / keep them under control. Even with all of the above in mind and much like Muralman, the aforementioned trade-offs still aren't enough to make me want to get rid of them and move over to more efficient, but typically sloppier designs. The high efficiency designs that i do have ( 96 dB's and 104 dB's ) are both sealed. Since you can't get something for nothing and maintain linearity, the efficiency of the 104 dB design is achieved via horn loading. Due to the length and size of the horn used, low frequency extension is reduced. In order to obtain ultra high efficiency and maintain good extension, you have to go to a BIG horn like the ones that Mike aka Magnetar builds and uses. You can see what i'm talking about here on his "horny" website. The three subwoofer horns are the huge cabinets behind the mains ( they take up the WHOLE front wall ) and look like wood trim surrounding black centers. Yes, Mike is a "little" crazy, but he's a real nice guy. You just wouldn't want to live next door to him : )

The little 96 dB units that i have are horn loaded for the mids and tweeters, but not the woofers. As mentioned above though, you can't get something for nothing, so these too are also limited in terms of low frequency bandwidth.

By the way, the rear wave of a driver can be sealed or vented when using some type of front loaded horn. My larger horns are sealed and as far as i know, i think that Mike's MEGA horn's are too. Sean
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You mentioned an spl rating of 76 dB's. At 70 dB's, this would allow you 6 dB's of headroom before you reached 1 watt of input. As mentioned though, i didn't know if you were measuring at 1 meter ( which is useless except for sake of comparisons to reviews ) or at the seated listening position. Given that most rock music only offers appr 5 - 6 dB's of dynamic range, you would be using 1 watt of power to produce the full dynamic range of such a recording based on the above information. This isn't to say that i was recommending such an installation or that it would work as well as theory dictates, i was just spouting off figures based on the math that "acoustic theoriticians" would tell us was sufficient. We all know better than that.

I was also wondering by what you meant by the statement that very few amps would drive them beyond 70 dB's??? Obviously, most any amp could generate 1 watt of electrical output relatively easily, so what's the fuss? As mentioned, the only thing i can see coming into play here is the low impedance / protection circuitry kicking in.

As to why the Class D amps work better, that has to do with the reduced duty cycle that the amp sees, the lack of sag in the power supply and lower levels of reflected EMF generated by the speaker. As you reduce the duty cycle of the amplifier, you also reduce the amount of drive applied to the speaker. Less drive equates to lower levels of reactance, which gives us less reflected power to deal with. This in turn allows the amp to load up more efficiently, which is just more icing on the cake. If the switching frequency is high enough, the power is delivered in very short and fast pulses, giving the power supply ample time to recover from the small amount of power drawn from during those bursts. If the switching frequency is too low, you can hear the "pulsing" of signal and it sounds fuzzy, choppy and lacks cohesiveness. A higher switching frequency limits the duration between pulses and the energy in the gaps is somewhat "filled in" by what is called "the flywheel effect". In English, the overshoot of energy initially applied keeps the forward or reverse momentum going until the next pulse is delivered. The potential for distortion with such a design is quite high, but with newer technology and MUCH higher switching rates, they are finding ways to get around this. Sean
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Muralman: Is the "Current Trends in Multi Thousand Dollar Speakers" thread the one that you were talking about?

As to Greg's comments, most recordings take advantage of sizable amounts of compression, particularly rock / pop recordings. This is less true in Classical recordings and you can always tell this when trying to listen to something in your car. Some passages are SO much quieter than others that it becomes difficult to hear them when you have the volume adjusted for "reasonable" listening during the crescendo's. It would be nice if the car audio industry introduced some type of switchable "compander" ( DBX type circuitry ) into their head units. I think that the reduction in sound quality would be more than made up for by the increases obtained by being able to hear the entire presentation without having to strain. Sean
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I started and finished that thread. Need i say more ??? : ) Sean
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