Here is a measurement. My own measurements show the same.
As for bats, according to Wikipedia (couldn't find any other information about it, lazy searcher as I am), their echolocation range is primarily limited by their pulse interval, not air absorption.
To clarify further, I don't believe in super-hyper-tweeters also, I agree that importance of frequencies above 10 kHz falls (for humans and their music, anyways). But I wouldn't say that those frequencies are absent in nature - I have fooled around with a bat detector outdoors, it was quite fun to hear all this ultrasonic noise. Up to around 30 kHz it's quite busy (crickets, grass and leaves moving in the wind etc), after that it gets increasingly quiet.
My wife teaches Audiology and she told me that nob ody does tests above 8 kHz, that the standard is only defined to 8 kHz and she showed me the form, which only went to 8 kHz.
Sorry, but that simply doesn't make sense. I can get distance with a single pulse, I don't need a pulse interval. Thats not to say that bats don't use the interval, I can see how they would, but the interval cannot be the limiting factor.
Please don't misquote me, or let me correct any misunderstanding, its not that no animals or signals use the frequency band above 10 kHz, its simply that with the large air absorption, those frequencies are very limited in scope. Humans deal on a very large distance scale compared to say a small cat. Cats hear well above 20 kHz, but on their distance scale the absorption is not a big factor. For humans it is. It's all a matter of degree. Signals exist, we can detect them, but our hearing is ill equiped to utilize them to any significant degree. The obviuos reason is that there has been no evolutionary development of these frequencies because of their rarity over larger distances in the environment. Our hearing is amazingly precise in all those attributes that nature dictates would be important for survival. Above 10 kHz is NOT one of those.
But a 7" scanspeak woofer simply sucks in terms of performance when you are considering the dynamics that exist in music or movies and . Im not a fan of compression, distortion at all so I choose better designs that can properly handle the peaks that exist in the content today.
Your quick answer about the 15" woofer having problems before 1200Hz is incorrect. You just need to realize what some QUALITY woofers can do! Linearity is incredible, distortion, extremely low and its just below the point of beaming.
Your post is a great example of over simplification. You haven't seen some of the better drivers and you might be assuming your needs are paramount. Some of us require dynamics without compression and distortion and some of us do have bigger rooms then a shoe box too!
HiFi drivers can not do that period so they are of a lessor quality then other choices like quality built pro audio drivers.
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Doug, I agree with you but looking at current recordings one could argue easily the other way around. See Loudness War Explained
Best, Markus
Slightly OT- there's some literature on the range of bat echolocation (I can post cites if anyone is interested). One factor on why the range is surprising is the astonishing SPL that the bat can produce; these have been measured as 120-133dB!
That most modern recordings are extremely poor is true, but really great ones do exist. I find the artists who care about their art care about how it is reproduced. One exception that I found was a terrible recording of Linda Ronstadt whom I have always had great respect for. How she allowed such a flawed recording to get out is truely a mystery to me. It may well be that she doesn't even know. Lets hope that someone actually realizes this and tthat the quality control has not degraded to the point where bad recordings get distributed without anyone even realizing it.
That's already reality.
Pink Floyd "Money"
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Metallica "Frantic"
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Roxy Music "Avalon"
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Bob Dylan "Thunder on the Mountain"
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Best, Markus
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That explains a lot!! Quite consistant with the kind of loses that I was describing. 120 dB out, -60 dB attenuation traveling through the air, 60 dB returning to the bat. Not a problem. For humans, 20 kHz at "normal" levels of say 80-90 dB and a distance of say 10->20 meters and you have 50->60 dB - not audible for most people in most environments.
What do you base that comment on. Do you have evidence that this is the case? I put it down to distribution where the maximum perceived loudness is felt to be the most desirable attribute and that the lower sound quality that results is recognized as "unfortunate" but completely accepted as a "trade-off" to making more money. In other words they know precisely what they are doing and accept it as OK. This was the situation with "quality" at the car companies when I started. They knew exactly how bad the cars were, but they didn't care. Poor quality made more money.
Sure, look at the pictures I added to my last posting. Most releases today are compressed to death to make them sound louder. The loudness war is over, tools that maximize loudness are standard.
Best, Markus
No arguement from me about compression that exists now but quality records still exist (I have FLACs that Im happy with) and for those we need dynamics to handle it! Of course only if we sit more then 5 feet away and we like to enjoy it a little louder after several drinks once in a blue moon 😀 Even at normal levels peaks are important. More so in Movies and care a great deal about my Home Theater experience.
Not only the speaker but the amp clipping issue is something that people are seldom aware of. I would rather have 95dB speakers then 86 dB speakers because I then do not require higher power amps.
I've seen measurements of some of the best pro drivers money can buy, and the ScanSpeak beats the lot of them in everything except dynamic range, especially once you get above 1khz.
While there are definite compromises involved in running the woofer in question as a woofer, using it in conjunction with a larger (10"+) bass driver can give very good results. If you need more SPL, run it in an WMTMW configuration.
The absorption increases with frequency but the main factor of sound attenuation remains (by far) the 1/r law (+ the reflections) for home audio purposes. In a normal condition, the absorption coefficient for 20 KHz is still much less than 1 (i.e. 100%). For a 20KHz signal the atmospheric absorption in an average condition (50% humidity and 20 C degree) is 0.52 dB/m. This is valid for a free field situation.
In a closed environment there is an additive contribution from reflections.
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If we look at the requirements for a typical home theater application, it probably would become apparent that there are more pro drivers that fit the bill than HiFi drivers. Pro vs. HiFi doesn't help much. Either a driver is suitable for the intended application or not. It's all about the application and reasonable trade-offs.
Best, Markus
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Doing a WMTMW is not great HT design, IMO and I care about performance under 1KHz and above...again, Its all about true dynamics.
Do you have 3rd party measurements for scanspeak 7" you are talking about?
Here is the TD12M, its a link because there are several great measurements for it from Augerpro.
AE Speakers TD12M (drivervault)
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I agree with him too, but it completely misses the point!! The point is that IN NATURE air absorption is high enough that HFs did not reach our ancestors to any appreciable degree and hence there was no reason for our hearing to develop at these frequencies - and it didn't. The absorption rates drops significantly below 10 kHz and these frequencies will propagate great distances.
Our hearing developed precisely in that range where best localization is possible as the result of shorter wavelengths and a sufficient perevalence of signal content to be useful. This is precisley why the region from 1 kHz to 10 kHz is so critical, because its this region where the most advtange is gained from high resolution. Below 1 kHz localization is becoming poorer, albeit still useful, but above 10 kHz the content is simply becoming insignificant.
I can blast a room with 30 kHz at 120 dB and you will DETECT it. Thats completely irrelavent. (Wow, is it ever hard to get people to comprehend a simple point.)
They chirp, then listen. Then they chirp again, and listen again, but only for THAT chirp echoing back, not the previous one. The largest distance at which they can detect an object by that method is half the distance that sound can travel between those chirps. When prey is detected, the bat closes it, chirping faster and faster, getting more accurate results for position but decreasing the detection range. Typical interval is around 100 msec in normal flight.
Seems I just misunderstood you. Point taken🙂
Anyway, shouldn't we get back to the original discussion, pro vs. hi-fi drivers?
For example, here is freq. response and distortion plots for a small 6,5" + horn PA speaker. Certainly not bad at all, to say the least. And knowing the designer of these speakers (Rog Mogale, founder of speakerplans.com), these plots are true.
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