Speaker Sound Degradation Outdoors

Discussion in 'Hi-Fi and General Audio' started by Jack Walton, Apr 14, 2017.

  1. Jack Walton

    Jack Walton

    Apr 14, 2017
    Likes Received:
    San Francisco
    Hey all - new here and was wondering whether somebody could point me to a study or information that deals with the relationship between the degradation of sound quality (and volume) and external factors in an outdoors environment. I'm interested in what the impact of more plants, or a body of water would be on sound quality and volume for example. Don't care whether it's a pretty academic source. Topic came up in a dinner discussion and I'd love to educate myself a bit.

    Thanks! :)
    Jack Walton, Apr 14, 2017
    Jason Lewis likes this.
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  2. Jack Walton


    Apr 24, 2017
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    Peavy is fairly relevant for outdoor sound--that ported booming midbass, that abrasive clear vocal treatment, are not pleasant in a little country club, but does get Peavy heard, clearly, outdoors.

    To explain the matter, we might have to look at automotive sound and church/theatre pipe organs.

    It only takes a few watts and basic tone controls to make rather impressive (or at least loud enough) automotive sound. But, it will fail to reproduce the low clear bass of the 32 foot pipe organ stops unless the car is at least that long. That's kind of, sort of why, cranking up the bass in the car sounds like weird high-pitch booming from outside the car. I summarized the matter a bit.

    Baffle step of speakers is a related matter--all signals physical as big as or smaller than the baffle, are just a bit louder than the lower pitched (larger physical size) signals. It is a good practice to arrange the crossover and baffle step frequencies the same so that the inequality can be cut more easily. It is either that or spend for a BSC circuit to do the same job (however, the BSC is an extra luxury that won't make it into production examples--instead the bass will suck in trade for the speaker being available instead of not. . . so let's have one more look at the notion of crossover at baffle step frequencies, please).

    Outdoors (except on the water or near a wall), we don't have the boost exhibited by cabin of the car, and the boost of the speaker, in comparison to the size of the outdoors, is insignificant. We also don't have the size limitation of bass notes. There's nothing in the way to prevent low-clear bass; however, there's one thing. . . you'd have to have an array of speakers the same or greater physical size as the bass note you'd like to hear. It is why Steinway can't make pianos at toaster size. So, for pipe organ, you need a 32 foot long bank of woofers, for orchestral 16 foot is minimum, and for pop music in the neighborhood of 8 foot and 12 foot will make do.

    In free air outdoors, you have to have the bass array (end to end woofers, in a row) the same physical size (refer to the pipe organ bass pipe measures for frequency versus length) as the lowest bass note that you want to hear.

    However, a wall or perhaps even a lake and/or other hard surfaces can reduce that inconvenience considerably, so long as the hard surface is quite near the speaker and is at least as physically large as the lowest bass note you want to hear. In this case, the full wave size is accomplished by the surface, so then the radiating element can be 1/4th as large as the lowest bass note you want to hear (or half that much if you do some EQ and at least 4 times the power--couple more speakers might be more convenient than breaker-blowing power, although that depends on the case).

    That's my view. It is from memory, so you can consider it opinion. I urge you to double check to see if there might be something more convenient.

    Not much works well outside to provide trouser-flapping bass and such a pleasant tone that you can still converse without shouting; however, the guys at Turbo-Sound have done that, and I haven't been informed as to how. It was outdoors, it was pop music rendered impressively, because a combination of clear and pleasant isn't easy to do with that much power, and the bass array was 11 foot long, just below the stage, at the front. This was witnessed at an Oktoberfest (so I was pasted), but I did bother to go ask the sound man how it was done. There was two large cabinets of TurboSound amplifiers run off one little Honda generator. The easy answer on that one is that the amplifiers were especially stable in all conditions and that the "main" speakers were rather well made and not loaded with bass tasks. Well, that's understandable. The separation, what with one cabinet and assocated speakers for mains&monitors and the other cabinet for powering the bass array, would have made reliance on speaker quality less important. The speaker that reproduced vocals wasn't shaken up by also reproducing bass. Those tasks were thoroughly separated.

    That soundman was the only one to get the job done at that particular outdoor party. All the rest were screeching and booming, usually both (also customers fleeing like roaches escaping the kitchen light, which is something that happens if the rent is reasonable). The answer he gave, a rather overstabilized (electronic version of stoned) amplifier wasn't the answer I was looking for although it was informative--he didn't have to work hard for a pleasant tone from the mains. I had already made amplifiers like that, and yes I do love the tone (the cost can be treble resolution unless you have a separate system for that--reconnoiter the basics of bi-amp). However, the electronic separation of task was better information, because it was also the well working divide-and-conquer approach, resulting in a solution with less compromise and more performance (at the speaker groups--with their necessarily separated tasks).

    The mystery at that particular soundman's presentation is what and how the separate treble array was done. To get the resolution up for that task, the amplifier is wound up tight, a bit nervous, with narrow tolerances, and thus probably shouldn't be used for anything other than the high treble.
    I noticed that the job got done. However, I did not notice how it was done. For that job, I would prefer high fidelity amplifiers driving electrostatic/ribbon/planar arrays. You could actually do that job with tv (clear vocals = nervous amplifier and the tight tolerances for treble, and we don't actually need to replay harsh vocals from it, in this case) and 2" or smaller paper tweeters (it doesn't take a magician with the crossover to do awesome with small paper tweeters). Dome tweeters of 3/4" and smaller size in an array, and an actual magician at the crossover, is perfectly acceptable for doing the very same job. The only thing I know for sure about their treble arrays is that they'd done it on purpose, it was electronically separate, and it had to have been powered by a wound up tight tolerenced, nervous, hi-fi amplifier that could not have done vocals pleasantly and would have either burned itself up or overloaded the generator had they tried it for bass.

    So, outdoors, there were 3 separate systems. The treble had a tight-tolerances amplifier and treble speaker-drive arrays of physically small (for their type) drivers in a row not much longer than my arm. The midrange and bass probably used the same style amplifiers, overcomp, very stable, placid, but they were separated by task. The midrange and some upper frequencies group drove speakers suited for that. The bass amplifier group was completely separate and drove only a lineup of woofers (it has to be at least as long as the physical size of the lowest pitch bass note you need to hear).

    I certainly do wish you can find a more convenient solution than this.
    And, I did deliver notes on the topic as best I could.
    The thing is that I sure would like some news about better than that.

    Edit: This form is about how to enjoy the music. And I really love that. Let me try to recap what I just said in a way that more closely matches what I love about this forum. They've used an array of extra small tweeters along with a high resolution amplifier for the treble. They've used an especially placid (super stable "current headroom") amplifier for the voice band. They've used a placid amplifier that may have been class d, and had to have the gain loop dc filters enlarged to pass at least 4hz for bass. All three systems were separate, meeting only at the mixer board.
    So, the outdoor sound that was so memorable from Oktoberfest was Tri-Amp. Also the bass was done from an array of woofers at least as physically large as the lowest note to be heard. It was fantastic! This did not require any brand name, but it did require purpose--3 separated purposes (and groups of equipment) that met only at the mixer.
    Last edited: Apr 26, 2017
    danielwritesback, Apr 26, 2017
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