Hi thanks and i agree completely
And this could be also a reason why the mini monitors usually image very well
Because they have narrow and short front baffles, and maybe also thick
I have notice that cheap minimonitors image better than cheap towers, where the baffles are long and usually also thin and they tend to flex as you say.
Moreover towers have also the woofer on the baffle that transmits vibrations to the mid-high drivers.
This is a good point for a satellite plus woofer arrangement.
Of course the best sounding towers have exceptionally well constructed front baffle, like some Rockport speakers for instance, where the front baffle is a thick sheet of metal.
Thanks and regards, gino
I feel like there are many parts that are not being discussed such as design, damping and isolation. Some people seem to mention metal or stiffness as a use for all three that is simply impossible. You need a non resonance material along with damping to deaden further along with an isolating section for connection to the other drivers. You cannot simply use one material for all 3. isolation implies damping but damping is not isolation.
If one doesn't mind a bipolar radiated sound field, the baffle needn't be so complicated. Many people I make speakers for prefer box speakers.Hi, and thanks a lot for the very valuable reply
Then i wonder if the test with accelerometers cannot be performed also on the front baffle, given its fundamental contribution to sound.
Other designers have addressed this issue, like Epos, even if the material used is a little poor (plastic)
I would use the same design but higher grade material (like aluminum)
just make this baffle in aluminum and the sound will be even better than what already is
Thanks again and kind regards,
gino
In most cases front and rear drivers can be mounted so that the holes in their baskets are aligned. A little threaded ready rod through the cabinets front back axis tightens these drivers against a separating sidewall to sidewall brace.
Instantly damped front rear baffles along with some nice force cancelling benefits.
Not having great math skills, it did take about a month of mucking about with transmission line cabinets to work right.
Doweling through sidewalls helps. Settled on inner layer of acoustic foam, MDF , dynamat, hardyboard, then veneer.
Lots of work.
It's why I prefer open baffles. : )
Hi and thanks for the very valuable advice
I still have this fundamental question: why no measurements of vibrations on the most important panel of the enclosure that is the front baffle
I was thinking myself about damping.
Now i am not so sure about the importance of damping.
Damping in some way is wasting of energy.
So a very stiff front baffle could work perfectly
For me it is important to have a graph like this for the front baffle
Taken from Stereophile magazine
Rockport Technologies Antares loudspeaker Measurements | Stereophile.com
what i really not understand is that this graph is the "cumulative spectral-decay plot of accelerometer output fastened to rear panel above reflex port"
as i said they usually put accelerometer everywhere but where it counts immensely more, the front baffle.
If the front baffle moves/vibrates there is a microdisplacement of the tweeter position in space (especially) and this in my feeling is extremely detrimental for a good soundstage reproduction.
A very thick front baffle would tame this a lot indeed.
The front baffle execution is decisive for me.
Again about damping, if you damp the woofer with the enclosure you will loose energy
The energy from the woofer instead should be all transformed in acoustic energy.
So an extremely stiff enclosure without damping should work best.
You do not want to waste the energy from the transducers.
Thanks again and kind regards, gino
Hi thanks for the very helpful reply.
I do not like at all dipoles and also omnidirectional speakers at all.
For me the sound should come only from the front baffle.
I am looking for a very good monitor speaker
I think that to integrate rear and side reflections with the front one is a real pain. Especially when you want a great soundstage reproduction.
The reflected sounds arrive with a delay in time ... this is unacceptable in my book.
As i said i was focusing on damping the box and did some toxic experiment with lead sheets.
In some way it worked, but now i think that stiffening is the way to go.
A very stiff box could indeed then resonate, i think at higher frequencies.
But this can be cured with a little strategically placed dampning material of the kind you mention.
But stiffness in the enclosure is mandatory.
The Matrix approach by B&W with extensive internal bracing is a very very good one.
What i do not like is kevlar for cones.
Just take a speaker like this and put a Scanspeak paper woofer and you have the ultimate mini size passive monitor
Actually i am looking for empty enclosure like these ones to be used as a base for a DIY little monitor.
I intend to use separate boxes for the bass range.
Looking at the graphs the main vibes generator is, obviously, the woofer
I think there is a good way to test this
If you take a panel with woofer and tweeter mounted on it and you fixed it to a frame by means of springs playing music the woofer will make the panel vibrating
This is of course a extreme situation
I am pretty sure the 3d sound image would be completely destroyed.
Viceversa if the panel would be perfectly still the image would be just perfect.
So it is all in the front panel, i think.
Thanks and regards,
gino
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Hi and sorry i swear, the last rambling 😱 ... almost 😀
I did this test
With a electronic xover i cut all the freqs below 120Hz and send the signal to my small to medium monitors
Actually the sound was missing some bass content compared when run full range but it was also much cleaner and the image better, more focused. 🙄
So my understanding is that the woofer was trasmitting less vibrations to the front baffle.
Also for this i tend to prefer satellite+sub arrangement instead of towers
Towers can be just perfect but the construction of a perfect tower is not an easy task at all.
Thanks and a nice day to everyone.
gino 🙂
I did this test
With a electronic xover i cut all the freqs below 120Hz and send the signal to my small to medium monitors
Actually the sound was missing some bass content compared when run full range but it was also much cleaner and the image better, more focused. 🙄
So my understanding is that the woofer was trasmitting less vibrations to the front baffle.
Also for this i tend to prefer satellite+sub arrangement instead of towers
Towers can be just perfect but the construction of a perfect tower is not an easy task at all.
Thanks and a nice day to everyone.
gino 🙂
In the real world you're not going to get away from the need for damping: no process of turning electrical energy into acoustic energy is perfect, there will always be "wasted" energy, and you then need to get that useless energy out of the picture, quick smart - otherwise something will vibrate that may generate sound, and that's distortion, pure and simple. The trick is to turn that non-utilised energy into harmless heat - and that's the job of damping ...
Thanks a lot for the helpful explanations
But i read something like if you stiffen the cabinet the resonances go higher in frequencies and are easier to tame ... honestly i did not fully understand and the all issue is not clear.
One thing i have noticed.
A very extreme application, where of course the level of vibrations is enormuos, had metal (aluminum) enclosure
http://www.diyaudio.com/forums/subwoofers/4500-krell-master-reference-subwoofer.html
So with an extension the concept if an aluminum cabinet is very ok for this very extreme application it should be good also for a normal speaker
And actually the same Company has a line of speakers with aluminum cabinets.
I do not know anything about their actual construction anyway.
I am sure some sort of damping has been used also there.
By the way looking at the cabinet construction of the best subwoofers around maybe it is possible to get some idea on cabinet design and construction
I have to add also a thing
Cutting low frequencies can also reduce the amount of IMD generated by the woofer when asked to reproduce these frequencies.
So i am not sure it is only an improvement due only to decreased vibrations of the cabinet. Maybe it has nothing to do with this.
Thanks a lot again
Kind regards, gino
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The "easier to tame" is another way of saying that the energy can be damped sometimes by a fortunate combination in how the materials are used, without you needing to go to extra lengths.
I don't know about aluminium - metal rings when you hit it with a hammer, what you want is a dull 'nothing'. Compressed timber, densified is the term used, appeals to me - look up Panzerholz ...
I don't know about aluminium - metal rings when you hit it with a hammer, what you want is a dull 'nothing'. Compressed timber, densified is the term used, appeals to me - look up Panzerholz ...
some Al diecasting alloys with Zn, Mg have very high damping (for metal anyway) http://www.interzinc.org/pdf/zinc6.pdf
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Hi and thanks again
I have personal experience with unfortunately toxic lead sheets glued and nailed to the wooden panel of speakers
To dampen vibes is exceptional indeed anyway. The best i think
I do not know if there is a way to make the lead safe
I would use a combination of metal, bracing and lead elements
But the idea to look at the best subwoofers cabinet is smart, i guess
This is a very extreme extreme situation
Kind regards, gino
Thanks and very interesting
If they use Al for subwoofers ... it must be ok
Krell at CEDIA 2012 (Part 2): New Krell Subwoofer and On-Wall Speaker - YouTube
regards, gino
Hi and well ... i have already been rebuked by him once, very rightly, because i forgot to mention the source of some information that was his magazine
I like the measurement pages on Stereophile a lot.
I think that they are both rare and very valuable for understanding products quality.
Maybe there is a technical reason that does not allow for this
At B&W they have done this since long time for woofers to show the diaphragm behaviour
Tools of the trade - laser measurements | Bowers & Wilkins | B&W speakers
i think it could be applied also to the front baffle
I will experiment some sort of stiffening with metal plates screwed to the front baffles
It is a very easy way
Thanks and regards, gino
If you had the money or the access to a laser test setup like the Kipple test equipment you could look at all the different components and see how each contributes to the overall emissivity of the entire enclosure and drivers. I wouldn't place a plugged nickels worth of faith in the use of aluminum as an undamped enclosure material just because it was done commercially. As far as your comments on lead I would think if you were careful and washed your hands after handling the lead sheets that they would be rather safe in this usage. I wouldn't expect any lead particles to be emitted once the sheets were solidly mounted but perhaps someone else can chime in on that subject. You could cover the lead with a plastic film to contain it in any matter.
Hello, There is a good reason not to measure the front panel.
It is a part of the over all loudspeaker response and it shows up in other measurements. It is even possible that the vibration of the front panel is designed to vibrate in a certain way to enhance the over all sound.
All other cabinet walls will radiate in different directions and have another effect on the sound.
It is my personal opinion that none of the cabinet walls vibrations are relevant. It is the end effect that is important. What is the combined sound field reaching the ears? That is what matters.
Vibrations need to be taken into consideration at the design phase. But they are a part of the finished design.
It is a part of the over all loudspeaker response and it shows up in other measurements. It is even possible that the vibration of the front panel is designed to vibrate in a certain way to enhance the over all sound.
All other cabinet walls will radiate in different directions and have another effect on the sound.
It is my personal opinion that none of the cabinet walls vibrations are relevant. It is the end effect that is important. What is the combined sound field reaching the ears? That is what matters.
Vibrations need to be taken into consideration at the design phase. But they are a part of the finished design.
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