Axiom Home Page Forums General Discussion Home Theater Double Blind Test

This one's for you John.

http://www.matrixhifi.com/ENG_marco.htm

Anyone ever hear the brand / model speakers they used?

That is a great article. I wonder how the people felt that brought the expensive amp and cdp (especially if they picked the wrong system).

My closest experience to something like this was buying an expensive DAC ($1k) to use in my system. When I first installed it, I could swear that I heard details I was missing before. Eventually, after switching back and forth I realized I couldn't distinguish it from the dacs in my receiver.

Luckily I sold it on ebay for almost what I paid for it, so the lesson wasn't too expensive.

The only thing wrong with the the test is that they weren't using Axiom speakers. Maybe then the Axiom speakers would have helped reveal the differences in those systems.

There ya go Dean. The Behringer A500 double blind tested against the big boys.

Must be that expensive speaker cables are the only thing that matters.

My $1200 power cord is going back.

Very good, Mike. As far as the speakers which determined the quality of sound heard, I vaguely recall reading about the ATC speakers in some of the British audio mags I thumbed through. The SCM12s apparently listed for around $2,000 and got some plaudits in British reviews about six years ago.

Dave, good to hear from you again! Yeah, the purveyors of voodoo audio would probably say that the speakers(and even more, the speaker wire)used weren't adequate in "resolution" to reveal what would have to be "huge", "night-and-day" ,etc. differences.

I totally agree with tests such as these. This is why I purchased a $600 dollar Emotiva amp instead of saving up for a $7500 dollar Denon amp. I have come to understand through this site and others that there just isn't enough of a difference to justify spending that much more money.

But, these tests don't address the battle that has been raging on boards such as this one for years... is it worth getting an external amp to power your speakers, or does a power receiver do the exact same job? These tests don't deviate from a specific decible level. And they don't test out the upper reaches of the volume levels. In the past 4 days I've experimented with the Emotiva vs my Denon and found the Emotiva to run my speakers better.... at higher volumes. If I capped the volume levels at around 90 dbs or so, then I am pretty certain I would not notice any percievable differences.

But I didn't buy my amp to listen to music at 90 dbs. My amp pumps out 350 watts to each of my M80's. The best my Denon could do was 125 watts each (perhaps). And in a direct comparison of the two, there's no way the Denon can match the Emotiva when the volume goes up. For instance, with the Denon powering my M80's I could get up to +5 pretty easily. It was loud, but it started to sound just a bit strained (the Denon maxes out at +10, and amplifier distortion rises slightly near it's limit). Switch over to the Emotiva and I got it up to -13 and had to stop... it was just about as loud as I could get her before I thought my head was going to explode. But since it was no where near the limit of the amp, it still sounded very relaxed, like she was just getting started. That's the difference. They should perform a test that takes a receiver up to it's amplified limit, and note the db level it's emitting. Then play an amp with triple the wattage (basically what my XPA-3 has over the Denon) at the same db level and see if there is an audible difference.

That would be an interesting test. Who knows, maybe it would turn out similar to these other tests. All I know is to me the Emotiva can run the M80's at louder volumes much cleaner than the Denon seemed to.

Whoah! Look who's back after almost a year. Nice to see your words again.

AGREED! Dave, good to see your name pop up again. Welcome!!!!!

Here is a good book I recommend for you. Sign Language Made Simple

Just kidding. Well, at least I hope this never becomes more than a joke.

The Whole Mitrix Hi Fi web sight has some interesting reading material, but this is the first time I can recall ever seeing a blind test set up like this.

I think it would be pretty fun to participate in one.

That is exactly what I've found. I was shocked to see that I could not tell Blu-Ray v. CD on Dave Matthews at RCMC, but I couldn't. But I can tell the difference between my Denon AVR 3300 and my separate amp at reference level - i.e., levels designed to reproduce the sound made live. Heck, I can even pick out which of the three fronts in hooked to the Denon in 5 ch music listening based on the harshness of some sounds on peaks.

And I still have not heard anyone explain how a subwoofer could sound great at 50hz working with the 10 or 20 watts the formula says should should drive it to 100db. Where is this mythical beast? I'd love a $100 sub that can reproduce a bass drum's kick accurately.

Physics.

Or Phys. Ed. ?

If you are playing music, which is where I think the calculator came from, you are probably fine with a low power small sub. Most music dosn't go lower than 40Hz, so you could buy a sub with a highly efficient driver like those used in pro subs.

Earl Geddes has no trouble getting 120db (with headroom) out of his mid bass drivers with a 100w amp. The drivers are rated at 105db if I remember correctly. Even his ULF sub (-3db of 20Hz) is not driven with a particularly powerful driver.

It all depends on your objectives and choice of drivers.

Dave! Welcome Back!

Dave, glad your back, I was wondering about you a few months ago...

Charles, I don't know the reason for the "still" comment on the 50Hz note. If a sub or a regular speaker is designed to reproduce 50Hz, it'll do so with 10 or 20 watts input. The output would depend on its sensitivity, of course. If there's some notion that the 50Hz note would somehow need more power than the same speaker would need for the same sound level at 500 or 5000Hz, that isn't the case. Volume is volume, sensitivity is sensitivity. The obvious illustration of this is the speaker graphs taken at 1 watt(typically about 85-90dB). In good speakers the volume is relatively constant. There's no upward slope as the speaker goes from the bass to "easier" mid-range and treble frequencies.

I appreciate the welcome back. You guys are great friends as well as masters of knowledge. It's good to see everyone here again.

Masters of Knowledge?

Hey guys, he's been gone so long he forgot who we were!

Or his sarcasm got a little sharper.

I meant I still don't get it after reading the articles and the posts. I just can't comprehend a subwoofer using 10 watts to make a 90db 50hz note. If that was the case, why would every sub use hundreds of watts even in modest settings. Marketing is one thing, but industry wide overkill is another.

I'll just put this in the long list of things I don't get.

Sounds like you should be all about I've always wondered...

How do you know every sub uses hundreds of watts at modest settings?

The power is there for dynamics. Its there for when it is needed. I would expect that power usage starts to go up exponentially in movie scenes when you have a lot of LFE, particularly at the bottom of the range.

Also, as soon as you use EQ to boost the low end, as it the case with the EP500 (and most any other sealed sub) you start to suck up a lot of power.

How much power a sub requires depends on a lot of things:
- efficiency of the driver
- the material being played
- the volume its being played at
- whether or not EQ is used to boost the low end.

The manufacturer has to take all these things into account and not all of them are in their control.

Add room gain, too...

[quote=fredk]

I think that hits at my point of confusion. It seems well accepted that lower end or LFE, takes more power. But when compared to the formula, the response is often the opposite - i.e., it takes the same for 50hz as 5000hz. Another related question, if only speakers with lower efficiency can make solid bass (this is a question,not a position) thus requiring the higher power, then does the theory hold true since in application the inefficiency of the driver needed to reach 50hz (or 30hz) will always require more power than the 5000hz note?

Just curious. Sorry to beat, flog, skin, and parade this dead horse, but it just blows my mind that you could get a 50 or 30hz kick drum beat from a sub (or any woofer) with 10 watts.

I have heard tweeters or mids play loud on small power supplies, but never a large driver making bass. I have built subs for car use since I was 14 and always found that even with the best subs (presumably of acceptable efficiency) you needed substantial power to get acceptable results.

Damn, now I know how the flat earth society meeting went when Columbas came back to report!

Ok so let me get this straight... the earth isn't flat?

Sniped!
I now have to edit to add this should have directly Quoted Mark's "Add Room Gain Too"

Oddly, it just occurred to me all those words individually insinuate "more"

Add = more
gain = more
too = also = kinda more
room, makes you think of roominess = more

What does this mean? Nothing really.
You guys should be used to the way I think when overtired by now.

It does "seem" counterintuitive to not need more power to drive a 12" SW than say, a 4" midrange.

BTW, who is Columbas?

Founder of the Bas Pro Shop, he discovered that lakes are flat.

Yeah, Adrian; I heard that he also claimed to be a descendant of St. Columba.

Adrian, driver size wasn't part of the discussion, so no "counter-intuitive" factor in that respect should have been suspected. The point was equal power used with a given speaker when playing a note within its designed capability at a given sound level, regardless of frequency. It's entire possible that a 12" driver would be less sensitive than a 4" mid-range(or a 1" tweeter). If that was the case and those drivers were used in the same speaker, the more sensitive drivers would have to have their output attenuated so that the speaker would have level response over its designed frequency limits. This can be done with an attenuation network at the end of the crossover consisting of a resistor in series with the more sensitive driver and another resistor in parallel(so that the impedance of the driver isn't changed).

Sound power is a given quantity which doesn't vary with frequency. For example, an acoustic(not electrical)watt of sound power output by a speaker results in about a 112dB sound pressure level at the standard 1 meter measuring distance. Frequency isn't a factor. If the particular speaker used 1 watt of electrical power and the measurement at 1 meter was 92dB, since this was 20dB down from the full 112dB, the efficiency of that speaker in converting electrical power into acoustic power is about 1%. Typical speakers with sensitivity ratings in the upper 80s of dBs are another 3dB down and are therefore about 1/2% efficient.

Hey Zimm. All you horse flogging has caused me to take a closer look at what I was posting. Johnk is, of course, correct (big surprise). I promise to stop making generic low = more power statements.


Design both of the driver and the box does have a lot to do with how efficiently the sub delivers its bass. All the really big drivers I have seen used in the DIY world seem to need a lot of power for the really low notes. I think it has to do with needing a big motor assembly to reach the high excursion needed to produce those sub 20Hz notes and still maintain linearity as the driver approaches it maximum extension. The big pro drivers seem to trade off low end extension for efficiency and headroom higher up.

Sealed designs rely on eq boost and room gain to maintain linearity. That can take a lot of power. Horn loaded designs seem to rely on gain from the box to increase efficiency.

That's all true. I'm guess I'm just confused by the real world seating position sound versus the math. If it requires big motors, and big boxes, and if room effects dampen bass after the one meter measure, etc., etc., then the math seems off in application. But I don't presume to know the whys, just the purchasing needed to get the sound to the seat. I've had very nice sounding 30w speakers. But, in my experience, when you want to get realistic bass, and mid-bass, you "need" amps with more power, even if the driver stays the exact same.

All B.S. (mine ) aside, I'd love to find out that a good 50 watt amp could drive my home or car system to reference levels (loudish). I get that most sound can be made with under 100 watts (hell, tweeters scream with 20) but that whole bass thing just throws me off.

Not unlike the farmer who walked his "flat" field a million times and had trouble believed he was walking up hill his whole life, I guess.