Vibrating speakers

Ahh, you're confusing and conflating several related yet different things. Yes the speaker vibrates. That's what we hear- vibrations. But there's really only one part of the speaker we want to hear vibrating: the cone. 

But playing music the cone goes in and out, which causes the whole speaker cabinet to vibrate opposite that. The speaker is a lot more massive and so it moves less but it still moves some and to the extent it moves it sucks the dynamics and life out of the music. This is one part of why physically bigger more massive speakers project a bigger more lifelike sound.

But its not just the whole speaker cabinet vibrating back and forth. Driver vibrations travel all through the whole speaker cabinet causing every single part to vibrate. All the wires and crossover parts, all the side front and bracing, all of it. None of which we want to hear. All we want to hear is the cone. But even the cone itself is resonating and vibrating in ways we do not want to hear.

So its all vibrations, only some of which we want. Kind of like the posts around here. You just need to figure out which are signal and whose are noise.

Enter speaker isolation. Hel-loo speaker isolation!

Imagine making a speaker attempting to get the same sonic behavior as a violin. Well, that's great, but how do you deal with a drum, a sax, the human voice, bells?  Yes, some instruments are made of wood, but many are not.

The speakers should not add any unintended sonic signature. I say "unintended" because some speakers have a house sound which is achieved through a variety of means, and I imagine cabinet construction is one of them.

Ideally, these vibration controls occur:

• The cabinet does not vibrate
• The cabinet does not transmit vibration to the floor, which then re-radiates into the room
• The speaker itself is fixed in all three dimensions

The last one is why adding mass to the top of a monitor can help.


Having said this, there is some research related to controlling, instead of eliminating, vibration altogether. I don't remember much about it, but it's a compromise brought on by the need to create affordable and relatively small and lightweight systems.

All box speakers vibrate. No way around it. ’Ye cannae change the laws of physics Jim.’


So what to do?

Well, with existing speakers, if you really feel there’s an audible problem - there might not be if the designer has factored in cabinet vibration/ output into the desired sonic signature they wanted - you can try to stand them on something which might attenuate some of their cabinet vibrations. Sorbothane, springs or footers etc. Townshend Audio have a long history of looking at isolation but they are not the only ones. In my experience these products can help where the sound can tend to get slightly ’muddy’ with certain recordings.

With cabinet design there are usually two approaches. Make it either extremely rigid to try to force these resonances up the frequency range (hopefully out of the listening range) or alternatively make the cabinet lossy (BBC style) so they disappear beneath the bass floor where our ears are the least sensitive.

Or alternatively you can opt for planar types and open baffles where the box resonances are naturally less of a problem.

There is a third approach, quite rare nowadays, akin to transmission lines, is to try to carefully use the unavoidable resonances (why fight the impossible?) in the same way as musical instruments do, ie to actually enhance the sound.

I think Russell K loudspeakers employ this strategy and they certainly have their fans. The piano firm Bosendorfer used a similar approach for their loudspeakers, but I don’t know if they still do. In any case I would always prefer a speaker with slightly too much life, and maybe not measure absolutely ruler flat than one that does but has too little life.

None of the current solutions are perfect but hey it’s only 2020 and we still await the next major engineering breakthrough.

It could be closer than we think if AI keeps evolving at its predicted rate.

I broke two laws of physics today and it’s not even time for breakfast. Don’t let some stuffy old physics dudes tell you what you can or cannot do. Faint heart ne’er won fair maiden. 💃

4 stupid questions from me then

Why have a cabinet? - just suspend drivers along an inert pole. Is that what you mean by an open baffle, but is planar totally open? (I have no idea what planar is in this context, do we need any planar aspect anyway)

Surely the other drivers vibrate from the other drivers more than confusion from a box - so what happens there? It's all relative

Why are speakers/drivers in one speaker box? Why not have 3 or 4 or more boxes?

So a concrete floor is just as much a vibration issue as a wooden floor as the speaker will still vibrate the same, presumably ?

Don't listen , the loudspeakers is not like instrument , is totally different .just marketing trick. the vibrate very very small and under control by good manufacturers, most of manufacturers use very hard material . 

Send an email to Alan Shaw with your question and await his response.

As popularized in song not all vibrations are bad. Some are good. Some are really good.😉

tatyana69

Good questions. I’ll try and answer as good as I am able - others may do better.


Q1 Why have a cabinet ?

Well without a cabinet it is difficult to get good bass. If you take a driver out of its box and play music you will notice the sound becoming weaker and very little bass. This is why subwoofers still come in boxes. You can get more bass by using larger drivers but most people wouldn't want to or be able to accommodate them.

Planars are an entirely different type of loudspeaker which uses a frame - not a box to reproduce sound.  

Open baffles also use a frame/ baffle but with conventional drivers and still no box.


Q2 Driver interference

Yes drivers can interfere with each but good designs try to minimise this by either using stiff baffles to mount the drivers and/or mounting the drivers carefully.


Q3 Why not 3/4 boxes?

You can have 3/4 boxes but they will cost more and remember that more drivers can also mean a more complex crossover. Not always desirable as even a 2 driver speaker can be already quite complicated. Some of the most expensive speakers multi driver/multi box speakers such as made by Wilson and Focal are built like this.

Q4 A concrete floor and a wooden floor?

A concrete floor is liable to have a different vibration than a wooden one in terms of resonances.

I’m guessing most speakers will perform better on a concrete floor, but there’s also the issue of secondary reflections. You know how voices sound different indoors and out - it’s a bit like that with floors and rooms.

For your interest I can also suggest that you watch this YouTube lecture by Dr Floyd Toole.

https://youtu.be/zrpUDuUtxPM

A fellow member djones51 posted the link recently and although the lecture is quite long it’s also very informative.

After a lifetime in audio Dr Toole has probably forgotten more about loudspeakers than most of us will ever learn.

cd318
After a lifetime in audio Dr Toole has probably forgotten more about loudspeakers than most of us will ever learn.

>>>>Toole was great in Lawrence of Arabia. 🐪