Speakers, speakers and speakers

Heard any audio today? All of you use and listen to loudspeakers on a daily basis – but how often have you thought about these rather amazing devices, and how they have changed and continue to change our world?

This is the first in a series of articles that are intended to discuss the different types and uses of loudspeakers that are used in our industry in terms that hopefully make sense – and we aim to do so without sending you to sleep – or rushing over to wherever you store your old math books in the vague hope they’re not in a landfill somewhere.

If you’re a speaker expert you may find this somewhat simplistic – but we’re not trying to go into the science of these speakers. Instead we want to explain the basic differences between the different options available for those of you that are not familiar with the subject. We intend to discuss why you’d consider designing with one type of speaker rather than another one.

Wikipedia tells us that “A loudspeaker (or loud-speaker or speaker) is a device containing one or more electroacoustic transducers; which convert an electrical audio signal into a corresponding sound”. Although Wiki is quite right, there is rather more to it than that when it comes to different speaker types.

There are actually a host of different types of loudspeakers – but it is relatively simple to split them into groups that have similar characteristics.

Before we start – one thing to remember is that ‘low’ and ‘high’ frequencies behave differently in air. ‘Low’ frequencies (such as generated by a bass speaker) will travel in pretty much any direction, and there’s mostly not a lot you can do about that (although we have seen a quite impressive steered bass array demo a few years ago). High frequencies are easier to control. What that means is bass speakers tend to behave as point sources, and that control of where audio goes can mostly only be done only at higher frequencies.

Spherical Speakers

I’m sure you recognize this one. These are the most common speakers that we see every day in the office, retail environments and at home. Spherical speakers are basically point sources. In very simple terms, the output from these speakers radiates outwards sort of like the light from a flashlight (reality is somewhat more complex, but that description will suffice for now). The angle at which the sound radiates matters – sometimes we want a tighter angle, sometimes we want the dispersion angle as wide as possible, and the angle at which a speaker radiates is pretty well set by the way that they are manufactured.

In principle, ‘normal’ speakers attenuate at around 6dB per doubling of distance – in other words, every time you double the distance from the speaker, you lose 6dB of volume level, simply because of the way the energy distribution from these speakers works. This means that when you’re close, they can be loud – but that audio levels go down relatively quickly as you walk away from these speakers. This property can be annoying, and it can be very useful depending on how you design your audio system.

Linear or Line Array Speakers

So here’s the thing – although they LOOK just like any other speaker, linear arrays really are quite different.

Linear arrays are the huge speaker arrays you see on (or mostly hanging above) stage nowadays. The radiation profile from a linear array is quite different, in that the output is wide, but quite limited vertically. Think of it maybe more like a car headlight where the light output is wide, but not very high.
This in turn means that the energy distribution of the speaker is high in one direction (usually horizontal), but limited in the other direction. This results in an attenuation at 3dB per doubling of distance as the audio is directed more tightly. This means that a linear array ‘throws’ sound further than a ‘normal’ speaker – but at the cost of limiting radiation in one direction. By shaping the array, you can control where the sound goes in the vertical dimension, and you can therefore control where the resulting audio ends up.
The principle is, that there’s no point at sending audio towards the roof – there’s no one there, and all that energy will only be reflected down causing echoes which reduces audio quality. If you look at these speakers such as the line array speaker here, the audio spreads widely from side to side, but is limited to about the height of the speaker in the vertical direction – so if you want to cover a 6’ area (to deal with a mixed seated and standing audience) you’re likely to want to mount two of these 3’ high speakers on top of one another to create a 6’ high sound field. The good thing is, that there is no extraneous energy that will go up or down from there, so even if you have a hard floor and a hard ceiling, you’ll avoid a lot of audio reflections, which is a good thing especially if you’re intending to get optimal speech intelligibility.
We have used linear arrays for a number of different purposes, and like them – the only limitation being that you can’t use them for low frequencies, so for a full range audio performance you’d somehow need to add bass (and control the area where the bass can be heard, obviously). There are some really good applications where this works though, and that is something we’ll address in a future article.

Phased Array Speakers

Phased array technology is quite normal when it comes to radar – but in the audio field we don’t see THAT many devices. A phased array speaker takes the principle of the linear array one step further by limiting dispersion both in the vertical and the horizontal direction.

Some of these devices actually allow you to ‘steer’ the sound somewhat by controlling the exit angle (done by changing the audio phasing between the speakers in this array) which can be very useful. Phased arrays tend to be expensive, and have their limitations, but they can be good for specific uses where other options don’t quite give the desired effect.

Dome Speakers

These speakers have their uses, we’re sure. However, these are not one of our favorites. There have been a range of dome speakers available that use a ‘normal’ speaker mounted in a usually fiberglass or acrylic dome. The dome takes the audio output from the speaker and turns it into a beam, a bit like the mirror in the back of your flashlight converges the light from the lamp.

In principle not a bad thing – however, since the behavior at each frequency is a little different, you’ll hear this weird effect as you’re walking into and out of the beam that to me always feels like someone is pulling a cork-screw through my head. The dome approach does not work at all for low frequencies, so the use of these speakers is limited to voice and music without a lot of low frequencies in it.

Combined with the appearance of these speaker types (large and often not easy to hide), we would only recommend their use in situations where there is just no other way of getting audio to your audience.

Ultra-sonic Beam Speakers

These speakers got a lot of interest a few years ago. The principle is that you send two ultra-sonic beams (easy to steer, as they’re VERY high audio frequencies) and modulate them such that the difference signal is audible – a bit like an in-air mixer effect. Again, not really one of our favorites although they can be useful. We have one in the lab, and anyone who would like to experience one of these is welcome to come and play with it.

The problem is the ultra-sonic component, which gives the writer a very uncomfortable feeling, followed by a headache when exposed to it for a while. Not pleasant. The fact that the US Navy use them (with rather higher power levels than the one we have here, obviously) to repel would-be boarders might have something to do with why we’re not crazy about them. Also, they only work for a fairly limited audio frequency range (think ‘tinny’) – about that of an old fashioned telephone.

One cool thing with them is, that you can really aim these speakers at someone at a distance, and they’ll be the only one hearing the sound (ideal for pranks, as we found out). The other thing is that the beam will reflect against hard surfaces, which allows you to bounce audio around. Conversely, using these speakers does mean you have to be careful about these reflections as audio can turn up in unexpected places if you’re not careful.

Cone-less Speakers

Cone-less speakers vary from the ubiquitous “Buttkicker” to a range of other devices that can be mounted onto a variety of surfaces such as Sintra, Corian, Drywall and even glass to turn them into a source of audio.

The Buttkicker transducer transfers low frequency energy (only) into whatever they are attached to (seats are a popular destination for these devices to cause a ‘rumble’ effect). Other higher frequency devices are used to hide speakers into set work and in effect turn the surfaces to which they are connected into speakers. These devices can be very useful, but don’t expect a low cost solution when they’re set up and used properly.

The limitation really is that the frequency response of the result can be somewhat problematic, and although you can get generic ‘filters’ with these devices, we have found that using a Digital Signal Processor is the right solution: you can set the frequency response to something that is acceptable by using white noise as an audio source, and then analyze what the output actually sounds like – and then to compensate for the various strange frequency related behavior using the DSP. The result can be quite acceptable, and there are sometimes enormous advantages to using this technology.

Well – that’s about it for this article on basic loudspeaker types. There are more options out there, but these are the ones that are most relevant to our industry as they’re the ones we’ll come across most often – and they’re the ones you’re most likely to be working with.

If you’d like more info on any of this, or if you’d like a more in-depth article, let us know; we’d be happy to help!

#speaker #loudspeaker #coneless #domespeaker #lineararray #phasedarray #sphericalspeaker #audio

扬声器、扬声器、扬声器 Speakers, speakers and speakers

今天是不是听到音响里的声音??每个人都习惯每天听到扬声器发出的声音——但是你是否总能想到这些神奇的设备呢,它们如何改变并持续改变我们的世界?

在系列文章中,这是第一次谈论用在主题娱乐行业中的扬声器的不同类型,我们致力于不让你读睡了,或者立即跑过去哪儿翻出落灰的数学书,模糊记忆中它们应该不至于被当垃圾扔了。

如果你是扬声器专家你可能觉得这对于你来说太容易了,但是我们不是要谈扬声器的科学,相反,我们要解释在你不熟悉的课题上,各种解决办法的不同点。我们想要讨论为什么你想要设计这样的扬声器而不是另外一种。

维基告诉我们“扬声器(德语:Lautsprecher;英语:Loudspeaker;西班牙语:Altavoz),俗称喇叭,是一种转换电子信号成为声音的换能器、电子组件,可以由一个或多个组成音响组。”虽然维基很正确,但如果说到扬声器的不同类型有更多需要知道的。

扬声器有很多不同的类型,但是可以根据它们类似的特点简单分为几组。

我们开始前,一件事一定要记住“低”和“高”频率在空气中的不同表现。“低”频(比如由低音扬声器发出的)会扩散到各个方向,差不多你拿它没办法(虽然我们几年前也见过被控制的很棒的低音阵列演示)。高频更容易被控制。这就意味着低音扮演点声源的角色,至于音频发散到哪里大部分要通过更高的频率完成。

圆形扬声器

我确信你认出这个。这些是我们在公司、卖场、家里最常见的扬声器。圆形扬声器主要是点声源。简单地说,这些扬声器的对外输出在某种程度上好像手电筒发出的光(但是更复杂,只是这个比喻可以帮助我们理解)。声音辐射的角度与声音是相关的,有时我们想要个小角度的,有时希望辐射角度尽可能的大,在扬声器制造的时候这个角度基本就被固定了。

原则上,每双倍距离“一般”扬声器衰减大概6分贝,换句话说,你与扬声器之间的距离每次乘以2后,你损失6分贝的音量级,就是因为来自这些扬声器的能量分布方式发生了作用。这就意味着当你靠近的时候,它们就声音大,但是你走的离它们越远它们的音频量就迅速响应降低。这东西能特吵人,但也可以非常有用,都取决于你如何设计你的音响系统。

线性或线性阵列扬声器

虽然看起来和其他扬声器差不多,但是线性阵列是非常不一样的。

现今你看到的舞台上(或大多数时候悬挂在舞台上方)的大型扬声器是线阵列。线性阵列扬声器的声音辐射侧剖很大不同,输出很远但垂直范围却有限。想象这个,就像汽车大灯,远但是不高。这就是说扬声器的能量分布在一个方向上是高的(通常是水平方向),但是另一个方向受到了制约。当音频被严格控制的时候,每双倍距离音频衰减3分贝。就是说线性阵列扬声器和一般扬声器比更像是把声音“扔”了出去,代价是限制了另一个方向的辐射。通过布局线阵列,你可以控制声音发出去的垂直距离,进而控制音频的结束位置。原则是,将音频发向屋顶是没有任何意义的,那儿没人而且所有能量将被反射下来引发回声降低音频的质量。如果你看一下这些扬声器,如线性阵列,从一边到另一边音频的扩散很远,但是垂直方向上高度也就是扬声器的高度,那你想要涵盖1.8米的范围吗(来解决混合座席和站席观众区的需求)?那你得安装两个这种0.9米高的扬声器,摞起来,以制造1.8米高的音场。好处是外部环境对这个音场不能构成干扰,即使你的房间内是硬地板、硬天花板,你也可以避免了很多音频反射,特别能帮你实现最佳演讲清晰度。
我们的线性阵列扬声器用于许多不同的使用目的,唯一的限制是你不能把它们用于低音频上,所以对于全音域的演出你就需要添加低音(当然要对能听到低音的区域进行音场控制)。这一方法有很多成功应用的案例,我们以后的文章再详细说。

相控阵扬声器

相控阵技术在雷达领域很常见,但是用在音响领域我们真没见有多少。相控阵扬声器比线阵列扬声器理论上又前进了一步,就是在垂直和水平方向都限制能量的分散。

这些设备实际上可以通过控制出入口角度(通过改变扬声器间的音频定向)让你“驾驶”声音,这个方法很有效。相控阵扬声器很贵,且有它们的局限性,但是对于那些有特殊需求但是其他解决方案都尽如人意的项目还是很好的。

穹顶扬声器

当然,这些扬声器有它们的用途。但是它们不是我们的最爱。通常在玻璃钢或亚克力的穹顶使用了大量穹顶扬声器,但其实它们就是一般的扬声器。穹顶把从扬声器发出的音频输出变成声波,有点像手电筒里面的那个镜子,聚集光源的光。

原则上这不是坏事儿,但是在每个频率上的表现都不太相同,当你走进走出声音声波时这就会让你听到奇怪的声音,对我来说就好像有人往我脑袋里塞耳塞。穹顶里使用低频完全不行,所以这些扬声器对声音有局限,音乐中不能有太多低音。

再考虑到这些扬声器的外形(很大且不容易藏),所以我们仅推荐在没有其他办法的情况下使用。

超声波扬声器

几年前这种扬声器得到很多关注。原理是你发射两组超声波(容易控制的极高音频)然后对它们进行调节,不同的信号都变得可听,这有点像个空中混合器的效果。虽然他们可能很有用但是还不是我们最喜欢的。我们在自己的实验室有一个,如果你愿意欢迎来我们这里玩玩体验一下。

问题是超声波组件让人有很不舒服的感觉,时间长了头疼。这可不好。美国海军用它们(比我们的功率级别高很多)的原因是击退非法入境的人,我们可不需要。超声波仅作用在特定的音频频率范围(很窄),差不多就是个老式电话机。

但有一个厉害的功能是你可以在远处让这些超声波扬声器指向特定的人群,他们是唯一能听到这个声音的人(我们认为作为表演环节中的戏弄音乐是非常好的)。声波会在硬表面反射,这样你就可以在环境中让声音窜来窜去。相反,正是因为这个,所以使用超声波扬声器要很小心声音反射问题,不然一不小心就会在你不想让它出声儿的地方出声儿。

非圆锥形扬声器

非圆锥形扬声器与广泛使用的“Buttkicker”及一系列其它设备不同,它们能安装在各种表面上,如挤压聚氯乙烯(挤塑板)、可耐丽(人造大理石)、干墙、甚至把玻璃都能变成声源。

Buttkicker传感器向其任何定向目标(通常是观众座席,并引发隆隆声的效果)传送低频(仅)能量。其他高一些频率的装置用于把扬声器藏在景片中,实际效果就是把材质表面和扬声器相连。这些装置可以非常有效,但是想安装并用好别指望想少花钱。

局限是频率反应的问题。虽然在这些装置里有一般的“过滤器”,但是我们发现数字信号处理器是最好的解决方案:通过用白噪音作为音频源你可以把频率反应调到能接受的程度,然后分析输出到底听起来怎样,然后用数字信号处理器弥补不同奇怪的和频率有关的表现。最后效果能很不错,有时候使用这个技术有很大的优势。

总之,以上文字都是关于基本扬声器的类型。还有更多类型,但这些是与我们的行业最相关的,是我们遇到最多的,且是你应该最希望使用的。

如果你希望了解比上面更多的内容或者想要更有深度的文章,请与我们联系,我们非常乐意帮忙!

#扬声器#扩音器#非圆锥#穹顶扬声器#线性阵列#相控阵列#圆形扬声器#音频

Speakers, speakers and speakers

Heard any audio today?? All of you use and listen to loudspeakers on a daily basis – but how often have you thought about these rather amazing devices, and how they have changed and continue to change our world?

This is the first in a series of articles that are intended to discuss the different types and uses of loudspeakers that are used in our industry in terms that hopefully make sense – and we aim to do so without sending you to sleep – or rushing over to wherever you store your old math books in the vague hope they’re not in a landfill somewhere.

If you’re a speaker expert you may find this somewhat simplistic – but we’re not trying to go into the science of these speakers. Instead we want to explain the basic differences between the different options available for those of you that are not familiar with the subject. We intend to discuss why you’d consider designing with one type of speaker rather than another one.

Wikipedia tells us that “A loudspeaker (or loud-speaker or speaker) is a device containing one or more electroacoustic transducers; which convert an electrical audio signal into a corresponding sound”. Although Wiki is quite right, there is rather more to it than that when it comes to different speaker types.

There are actually a host of different types of loudspeakers – but it is relatively simple to split them into groups that have similar characteristics.

Before we start – one thing to remember is that ‘low’ and ‘high’ frequencies behave differently in air. ‘Low’ frequencies (such as generated by a bass speaker) will travel in pretty much any direction, and there’s mostly not a lot you can do about that (although we have seen a quite impressive steered bass array demo a few years ago). High frequencies are easier to control. What that means is bass speakers tend to behave as point sources, and that control of where audio goes can mostly only be done only at higher frequencies.

Spherical Speakers

I’m sure you recognize this one. These are the most common speakers that we see every day in the office, retail environments and at home. Spherical speakers are basically point sources. In very simple terms, the output from these speakers radiates outwards sort of like the light from a flashlight (reality is somewhat more complex, but that description will suffice for now). The angle at which the sound radiates matters – sometimes we want a tighter angle, sometimes we want the dispersion angle as wide as possible, and the angle at which a speaker radiates is pretty well set by the way that they are manufactured.

In principle, ‘normal’ speakers attenuate at around 6dB per doubling of distance – in other words, every time you double the distance from the speaker, you lose 6dB of volume level, simply because of the way the energy distribution from these speakers works. This means that when you’re close, they can be loud – but that audio levels go down relatively quickly as you walk away from these speakers. This property can be annoying, and it can be very useful depending on how you design your audio system.

Linear or Line Array Speakers

So here’s the thing – although they LOOK just like any other speaker, linear arrays really are quite different.

Linear arrays are the huge speaker arrays you see on (or mostly hanging above) stage nowadays. The radiation profile from a linear array is quite different, in that the output is wide, but quite limited vertically. Think of it maybe more like a car headlight where the light output is wide, but not very high.

This in turn means that the energy distribution of the speaker is high in one direction (usually horizontal), but limited in the other direction. This results in an attenuation at 3dB per doubling of distance as the audio is directed more tightly. This means that a linear array ‘throws’ sound further than a ‘normal’ speaker – but at the cost of limiting radiation in one direction. By shaping the array, you can control where the sound goes in the vertical dimension, and you can therefore control where the resulting audio ends up. The principle is, that there’s no point at sending audio towards the roof – there’s no one there, and all that energy will only be reflected down causing echoes which reduces audio quality. If you look at these speakers such as the line array speaker here, the audio spreads widely from side to side, but is limited to about the height of the speaker in the vertical direction – so if you want to cover a 6’ area (to deal with a mixed seated and standing audience) you’re likely to want to mount two of these 3’ high speakers on top of one another to create a 6’ high sound field. The good thing is, that there is no extraneous energy that will go up or down from there, so even if you have a hard floor and a hard ceiling, you’ll avoid a lot of audio reflections, which is a good thing especially if you’re intending to get optimal speech intelligibility.
We have used linear arrays for a number of different purposes, and like them – the only limitation being that you can’t use them for low frequencies, so for a full range audio performance you’d somehow need to add bass (and control the area where the bass can be heard, obviously). There are some really good applications where this works though, and that is something we’ll address in a future article.

Phased Array Speakers

Phased array technology is quite normal when it comes to radar – but in the audio field we don’t see THAT many devices. A phased array speaker takes the principle of the linear array one step further by limiting dispersion both in the vertical and the horizontal direction.

Some of these devices actually allow you to ‘steer’ the sound somewhat by controlling the exit angle (done by changing the audio phasing between the speakers in this array) which can be very useful. Phased arrays tend to be expensive, and have their limitations, but they can be good for specific uses where other options don’t quite give the desired effect.

Dome Speakers

These speakers have their uses, we’re sure. However, these are not one of our favorites. There have been a range of dome speakers available that use a ‘normal’ speaker mounted in a usually fiberglass or acrylic dome. The dome takes the audio output from the speaker and turns it into a beam, a bit like the mirror in the back of your flashlight converges the light from the lamp.

In principle not a bad thing – however, since the behavior at each frequency is a little different, you’ll hear this weird effect as you’re walking into and out of the beam that to me always feels like someone is pulling a cork-screw through my head. The dome approach does not work at all for low frequencies, so the use of these speakers is limited to voice and music without a lot of low frequencies in it.

Combined with the appearance of these speaker types (large and often not easy to hide), we would only recommend their use in situations where there is just no other way of getting audio to your audience.

Ultra-sonic Beam Speakers

These speakers got a lot of interest a few years ago. The principle is that you send two ultra-sonic beams (easy to steer, as they’re VERY high audio frequencies) and modulate them such that the difference signal is audible – a bit like an in-air mixer effect. Again, not really one of our favorites although they can be useful. We have one in the lab, and anyone who would like to experience one of these is welcome to come and play with it.

The problem is the ultra-sonic component, which gives the writer a very uncomfortable feeling, followed by a headache when exposed to it for a while. Not pleasant. The fact that the US Navy use them (with rather higher power levels than the one we have here, obviously) to repel would-be boarders might have something to do with why we’re not crazy about them. Also, they only work for a fairly limited audio frequency range (think ‘tinny’) – about that of an old fashioned telephone.

One cool thing with them is, that you can really aim these speakers at someone at a distance, and they’ll be the only one hearing the sound (ideal for pranks, as we found out). The other thing is that the beam will reflect against hard surfaces, which allows you to bounce audio around. Conversely, using these speakers does mean you have to be careful about these reflections as audio can turn up in unexpected places if you’re not careful.

Cone-less speakers

Cone-less speakers vary from the ubiquitous “Buttkicker” to a range of other devices that can be mounted onto a variety of surfaces such as Sintra, Corian, Drywall and even glass to turn them into a source of audio.

The Buttkicker transducer transfers low frequency energy (only) into whatever they are attached to (seats are a popular destination for these devices to cause a ‘rumble’ effect). Other higher frequency devices are used to hide speakers into set work and in effect turn the surfaces to which they are connected into speakers. These devices can be very useful, but don’t expect a low cost solution when they’re set up and used properly.

The limitation really is that the frequency response of the result can be somewhat problematic, and although you can get generic ‘filters’ with these devices, we have found that using a Digital Signal Processor is the right solution: you can set the frequency response to something that is acceptable by using white noise as an audio source, and then analyze what the output actually sounds like – and then to compensate for the various strange frequency related behavior using the DSP. The result can be quite acceptable, and there are sometimes enormous advantages to using this technology.

Well – that’s about it for this article on basic loudspeaker types. There are more options out there, but these are the ones that are most relevant to our industry as they’re the ones we’ll come across most often – and they’re the ones you’re most likely to be working with.

If you’d like more info on any of this, or if you’d like a more in-depth article, let us know; we’d be happy to help!

#speaker #loudspeaker #coneless #domespeaker #lineararray #phasedarray #sphericalspeaker #audio