Is vibration bad or good

[lorenzoS]

Dear members, I am new. I think it is a bad idea to join this forum at a time in my life when I'm low on cash. Anyway. I have a burning question.

I have recently finished my first ever set of speakers. They are a two-way bookshelf stereo set of about 3.5L from memory with 5" woofers and first-order crossovers with cutoff at 6kHz. Wall material is 18mm MDF. I acoustically stuffed with nontraditional layers of hessian sackcloth. They work. I'm pleased.

I am not really an audiophile (I'm an electronic engineer (well now communications but...)coming at this from an electronics hobby perspective rather than as a Hi-Fi aficionado or music lover). This means I'm finding it hard to evaluate my speakers perceptively. I tried a simple sine tone test. I was pleased to find my laptop speakers wont produce sound below 150 Hz whereas my homebrew speakers were still audible at 70 Hz. I also compared them to a libratone too, my previous home audio solution. That was also audible at 70 Hz but quieter. However, the libratone was much more vibrate-y. The floor could be felt to shake. It also had I want to say more "echo-y" colourful sound. I think I prefer this sound slightly, and it solidified an idea in my head that the homebrew speakers sounded a bit "dead". Indeed there is no vibration even when I put my hand on the things apart from the cones. Violin sounds great, enya sounds cool, some other songs I like less, especially most electronic or pop songs.

My question is, in theory, is room shaking bass good or bad? Is vibration good or bad? And also what variables affect how much vibration is produced?

Thanks in advance.

 

[rayma]

Speaker cabinet vibrations are always bad, and all the sound should be from the drivers.
Bass should only be present if it is in the source recording, though most commercial speakers
are tuned otherwise.

 

[Johno]

Hi LorenzoS welcome to the club. I suspect most of us here are retired and therefore cash flow negative or neutral, but ultimately, a hobby is good for mind, body and perhaps soul.


I live in a place where live music performance is very strong - choirs, opera, ballet, brass bands and a magnificent old pipe organ - and where vibration producing bass is always part of the experience. So vibration and bass at a reasonable level is good.

 

[Galu]

There is a school of thought that a loudspeaker cabinet should be designed to be as light and thin as possible.

It is claimed that the more solid and heavily damped a cabinet, the more energy it stores, the slower energy is released and the more sluggish and leaden the speaker sounds.

Having a light and thin-walled cabinet, it is suggested, allows any stored energy to be dissipated quickly.

One would think that light, undamped cabinet panels would vibrate, but could this be essential to convert stored energy into heat and provide the rapid energy dissipation mechanism suggested above?

 

[scottjoplin]

If it vibrated equally at all frequencies it wouldn't be much of an issue

 

[fatmarley]

If some music sounds good but other stuff not so good then you most likely have a wonky frequency response. Best thing you could do is buy a measurement microphone.

 

[MAAC0]

Let me put this way. You are watching a movie on TV. Do You like explosions or Thunder ? Do want to feel it ? Yes ! Your walls and floor and even You couch must vibrate.
Now consider listening to a violin or even Enya's voice. She's singing that high frequency tone and You hear the cabinets and not the drivers. That's bad of course. What i want to say is, there should be always vibration but in a controlled way. There is no perfect world nor perfect speakers. The best speakers are the ones You like.

 

[system7]

A libratone speaker seems to be a wifi boombox of small size.

These gadgets use tremendous electronic bass boost to produce that illusion of deep bass. It doesn't really convince since you can't beat the laws of physics with small drivers. The bass output is probably a highly boosted 120Hz lump!

Your own project at 3.5L and 5" driver is not going to rattle the floorboards either!

No replacement for displacement with bass:

Even something 8" 25L closed box like this is only right for a smallish 4metre square living room:

You have built a bedroom speaker....

Tricks can be employed, like reflex loading to get another octave, or a bit of bass boost from a bigger bafflestep coil. but really I wouldn't expect anything much from less than 8L:

Peerless HDS PPB 830860

Even that won't go loud. The 5" driver will run out of excursion quite quickly. And distort.

 

[Tweet]

LorenzoS,

Because you are new to most of this can I direct you to a site that may give you a leg up on loudspeaker design. It is somewhat elementry for the more seasoned DIY'ers of many years but will introduce you to the complexity of loudspeaker design. The presenter is not pretentious in any way and is down to earth in his videos.


Worth a look.


YouTube


C.M

 

[lorenzoS]

@System7, always good to hear from a Portsmouth man. When you say a 120 Hz 'lump', this means you suspect they have an active base boost circuit which just massively amplifies the 120Hz band in question? Is it really bad to use such tone controls to compensate from less than flat frequency response, if yes, why?

 

[YSDR]

There is a school of thought that a loudspeaker cabinet should be designed to be as light and thin as possible.

It is claimed that the more solid and heavily damped a cabinet, the more energy it stores, the slower energy is released and the more sluggish and leaden the speaker sounds.

Having a light and thin-walled cabinet, it is suggested, allows any stored energy to be dissipated quickly.

One would think that light, undamped cabinet panels would vibrate, but could this be essential to convert stored energy into heat and provide the rapid energy dissipation mechanism suggested above?

If the speaker walls are thick and heavy but not stiff enough then that might be a problem, but usually thick and heavy walls are more stiff than a thin and light wall. So the thick and heavy walls are less excited by the vibration from the drivers. This is only my guessing.

 

[system7]

Thin-wall or light cabinet construction is based on the fiendishly difficult theory of resonances, and how best to avoid them:

Interesting read I found on Lossy Cabinet designs by Harbeth

The idea is a light and rigid cabinet can't store much energy, and a lot of that energy can be absorbed by rubbery panels stuck to the side and top and bottom walls as it flows around. This is what the BBC found back in the day for their monitor outside broadcast speakers. And light is good when you have to hump them around! Take a tip from an old timer, that rubber feet reduce nasty rattles.

Below a certain -30dB level, cabinet resonances don't intrude. Something Harbeth have applied for many years, and people like them. If a slightly wooden sound is part of the package, maybe it suits wooden instruments in the Classical Orchestra. IDK.

@System7, always good to hear from a Portsmouth man. When you say a 120 Hz 'lump', this means you suspect they have an active base boost circuit which just massively amplifies the 120Hz band in question? Is it really bad to use such tone controls to compensate from less than flat frequency response, if yes, why?

The libratones are probably 3" basses in reflex. I'd be surprised if they go below 120Hz in any significant fashion. Boomboxes have very little in common with the flattish response of a big bass speaker.

Let's look at a 8" reflex (Qts=0.33) Visaton W200S-8 bass driver in 30L closed box:

Now we give it its preferred reflex enclosure, because if it worked well in closed box, it would have a Qts nearer 0.5 and a smaller magnet:

See it goes much deeper. FWIW, you can always spot a reflex driver (where there is a tuned tube in the cabinet) by the big magnet.

Hours of fun to be had with the Boxsim simulator:
Software | Visaton

If you want the big bass, the Debra charity shop in Elm Grove has a pair of Wharfedale 8" bass Linton II's for sale at an outrageous £90. I think they'd take £50!

Probably most of it still works, and you could fix them if they don't. But good 25L boxes that you could fit most 8" woofers and tweeters to. And biggish bass. Those old speakers are like old digital cameras. People are throwing them away. Bargains to be had.

 

[res07njc]

I've read about these lossy/resonant cabinet constructs. I'm quite certainly no expert, but they do seem to offer something lively? Is that the right term? Where a life-like or euphonic experience can occur, at the expense of volume.

For lower volume listeners like myself this seems like something worth pursuing; but still respecting the science of all of this, it also seems like something difficult to analyze/predict/replicate for a given situation/equipment and thus a black art area.

And then dependent on one's taste even. I wish there were more of these types of speakers being DIY's or explored. The experimental nature of it is prohibiting, unless you want to build 4 or 5 different cabs to experiment with. If only there was an LtSpice for materials....