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Multi-Way Conventional loudspeakers with crossovers

calculations for spherical enclosure.
calculations for spherical enclosure.
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Old 12th October 2018, 02:08 AM   #41
krivium is offline krivium  France
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Hollowboy,
Your suggestion of 150hz fc for sub/satellite could work ( but you may have to use bsc on sat or you may end up with a loudness/bell curve, which may be totally acceptable dependent of spl used) but it will depend of room size ime.

Usually it is considered sub 80hz you can't locate source. This is true in large room in my experience
. In typical domestic where modal zone goes higher in freq you could not be able to locate up to 150/200hz because the room screw up the response.

However the sub should be located close to the satellite or there will be some issue which can be annoyable (ever heard a Bose acoustimass -and this is not only related to the hole in fr between the sub and sat, there is other issues too i heard-?).

In fact the 150hz fc works well for a fast/waw where the fullrange is usually close to the subwoofer.
I would design for 80hz for sat just in case 150hz will be too much an issue (and if it works at 150hz it will give more spl or headroom which cannot be bad either).
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Old 12th October 2018, 07:02 AM   #42
hollowboy is offline hollowboy  Australia
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Quote:
Originally Posted by krivium View Post
However the sub should be located close to the satellite [...]

In fact the 150hz fc works well for a fast/waw [ note for OP: a type of sub / sat system ]where the fullrange is usually close to the subwoofer.
Agree. Ideally the OP would use 2 (or more) subs and place the L sub near the L satellite, and the R sub near the R satellite. The higher the crossover point, the closer they'd want to get the subs to the satellites.

...but for a normal space (not a dedicated listening room), the perfect gear + layout might not be possible. Close enough is good enough
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Old 12th October 2018, 08:01 AM   #43
Aucosticraft is offline Aucosticraft  India
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Quote:
Originally Posted by krivium View Post
Hi,
This will help:
True Audio TechTopics: Diffraction Loss

SBIR calculator

Once you've got your fc for baffle step compensation (1000hz in my previous example) you'll have a choice to make: either you 'boost' your low end, either you 'cut' the high end.
Two things have to be taken into account in the choice you'll make:
_first is headroom: if you boost low end frequency you'll loose headroom in the low which may be an issue as low are usually high crest factor signal ( think about a kick drum: no or low sustain but high impact thus high transient, this is the reason in PA you'll have kwatts amplifier dedicated to low end too: high transients to take care of...),
_second we (our brain) are less sensitive to phase rotation implied in cut eq than in boost.

So for bsc the logical choice for me is to use an eq in high shelf mode where fc is 1khz and attenuate the high end by an amount up to -6db. This value is a worst case scenario ( in free field with the loudspeaker mounted on a 6meter pole) and you'll usually have something within 2 to 4 db range of attenuation in a real room ( you have room gain and boundary conditions which come into play).

You can use any high shelf eq on your source material ( if your source is a computer this is easy) cause you'll cut the high freq ( much less chance to saturate the source as you cut) and then you can either move away to listen to your music or if you plan a passive bsc circuit you'll have the attenuation needed for your speakers.

I hope this is clearer.
Anyway, what is the outside diameter of the ball you plan to use? We will do the math here.

Thanks....

It's very clear ..

I am banging my head. feeling stupid . How could I miss the concept of standing waves, and all that phenomena of different spaces.

Usually, I am not much into satellite and sub design although done few.

The calculation page you provided , got my senses back.

So a room small satellite speakers placed on wall voids all the calculations of BSD for that specific speaker. And what actually works is the calculations for standing waves.

So, the enclosure diameter is 0.17m.
F3 will be 115/ 0.117 = 983 Hz. ( I always used calculator for this. without bothering to understand equations.)
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Old 12th October 2018, 08:07 AM   #44
Aucosticraft is offline Aucosticraft  India
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Quote:
Originally Posted by Richidoo View Post

EDIT: There's perfectly smooth and predictable diffraction cancellation with a sphere. You don't need a simulator to tell you that. It's about a 3-4dB per octave attenuation toward the low freq. If you know the center freq of the baffle step then you can easily flatten it perfectly with a simple filter, active or passive. The center freq is solely determined by the diameter of the sphere.
Got it Sir...
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Old 12th October 2018, 08:20 AM   #45
Aucosticraft is offline Aucosticraft  India
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Quote:
Originally Posted by krivium View Post

Usually it is considered sub 80hz you can't locate source. This is true in large room in my experience
. In typical domestic where modal zone goes higher in freq you could not be able to locate up to 150/200hz because the room screw up the response.

I would design for 80hz for sat just in case 150hz will be too much an issue (and if it works at 150hz it will give more spl or headroom which cannot be bad either).
Check reference for LFE here.


Quote:
Originally Posted by krivium View Post

However the sub should be located close to the satellite or there will be some issue which can be annoyable (ever heard a Bose acoustimass -and this is not only related to the hole in fr between the sub and sat, there is other issues too i heard-?).
Idealy Satellite speakers should start rolling off at 120Hz. and -6db should be at 80Hz. Do you think those tiny satellite of acoustimass can go that low?
So somewhere they got subwoofer cutoff at much higher freq ie around 200Hz. And as we know 200hz has some directional information. It sounds crazy. Check the link here Bose Acoustimass Review - intellexual.net
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Old 12th October 2018, 11:20 AM   #46
krivium is offline krivium  France
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Hi Aucosticraft,
No reason to feel stupid, enclosure diffraction is a vast subject and there is controversial views about it ( check 'baffle diffraction' thread to have an idea...).

That said box diffraction ( Baffle step and edge diffraction) are related to acoustic and room behavior yes, but those are different issues and should be taken as different things. There is overlap between them though ( the modal zone screwing up response in small room i talked about previously being one example). But don't expect to rely on one to fix the other this won't nescessarely work.

About Bose acoustimass, well there is a lot of theorical flaws for an high quality reproduction system in the concept but it have some virtues ( it is visually non intrusive, for its size and bulkyness it produce an impressive spl amount) and once you've got a nice picture and a well written sentence to back on it a price in accordance to the sentence (not cheap for what it is!), most potential customers will be sure this is a high grade HIFI and will happily spend their hard earned money on this...

Technically speaking, there is a range (around 200hz) where the acoustimass subwoofer isn't able to produce enough output to fill the range up to satellite (which won't produce any real output below 300hz). So this area is lacking in the one i've heard ( they may have revised that since the one i've listened regularly was from mid 90's).
Then they don't follow the "1/4 wavelength center to center distance at cut off frequency" rule either. This is the issue i find more problematic: the emmission source is not corelated and appear to be from different points in space for me. This is not natural and the worst issue in my opinion. This is true for most satelite/sub system (2.1) i've heard and the reason Hollowboy and I warned about having the subs located closest possible to satellite. But as Hollowboy stated better being 'close enough' than not at all! And if compromise have to made then make the one that will not bother you the most.

About LFE, i might have skipped it but are you designing a 5.1 system (Home Theater) or a music system (2.1 or 2.2)? Both are different and requirement aren't the same.
The page you linked is for Home Theater and the '.1' chanel which is different than what you need for music reproduction.
In other words the reference they give about volume (spl) and crossover frequency may be valid in an Home Theater not for music.
The choice of crossover frequency for example is a design choice which induce compromise (as everything loudspeaker related), and choice you'll make won't nescessary follow some rules given the result you want at the end.
EG: i would be perfectly happy with a Bose acoustimass in my kitchen or if i was a bar/coffeeshop/restaurant owner to diffuse background music while i'm doing other things and having an spl that allow discussion. For critical listening? Well... not at all!

Last edited by krivium; 12th October 2018 at 11:23 AM.
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Old 16th October 2018, 09:12 PM   #47
Aucosticraft is offline Aucosticraft  India
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Quote:
Originally Posted by krivium View Post

About Bose acoustimass, well there is a lot of theorical flaws for an high quality reproduction system in the concept but it have some virtues ( it is visually non intrusive, for its size and bulkyness it produce an impressive spl amount) and once you've got a nice picture and a well written sentence to back on it a price in accordance to the sentence (not cheap for what it is!), most potential customers will be sure this is a high grade HIFI and will happily spend their hard earned money on this...


I agree, I think it's the BP design of subwoofer. That gives it spl feelings. I haven't tried any BP woofer enclosure. DO you have any idea does it get that signature bass from BP enclosure?

If you say yes. Let me try this time.


My wife dont understand music system All she can say is if it feels good or bad . So once when sitting in a sports bar. I asked her how down the music system sound? It was a known music played. She replied, Why are the the speakers screaming ? Those were Acostimass.

And the same kind of section she gave when visited Mcdonalds. (She has no idea What Bose is.)
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