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"speakers angled facing" theories

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bob4 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 13 September 2017 at 8:14pm
Originally posted by Conanski Conanski wrote:



Any time there is more than 1 driver in a pass band you get mutual coupling at frequencies below where the the wavelength is equal to the driver diameter, for an 8" driver that is about 1.5khz so as long as your crossover is there or below you are good.

Is this statement correct? to me it appears that  you're mixing up the acoustic transducer beaming threshold (lambda = PI*d ) with the criterion for mutual coupling (summation) of two acoustic sources, which AFAIK should be:    distance between center of drivers =< lambda*1/4

if the distance between centers is higher than that, the result will be comb filtering, not mutual coupling??!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 4:10am
The beaming threshold goes hand in hand with the coupling, as those two do the transition at the threshold ballpark/range between each other. You still have coupled drivers past lambda/4 on axis. They're more coupled then uncoupled unless you go closer to half of the wavelenght. Where edges of the cone get 100% uncoupled at 90 degrees angle. My question really wasn't about if it is doable on the scientific level. I'm rather looking for mechanical solution. Because at 1500Hz, this coupling and wavelenght stuff gets to "properly sized horn size territory". If I want it to act like point source, the driver with the horn has to be in that V-slot. But as it can only be about 20cm "long" at each dimension there is not much chance to put the horn in, unless one doesn't care about directivity pattern. On the other hand, getting some directivity at 1500 Hz should not be big problem. I.E. OSWG approach stretched. I guess I heve to do my development with speakers in my hands to find out.

Natty: hope you solve your issue. Are you into it seriously? Can we expect some wicked project? :-P

Edited by Crashpc - 14 September 2017 at 4:17am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 2:45pm
Originally posted by _Natty_ _Natty_ wrote:

yes david, apologize for my poor eng!
and yes thanks u guess right... honestly i didnt see the other 2 drivers up (ive seen just 2) and I choose this pic just because i'd like to understand what type of loading is that one and looking in what are based and for what... at least the name of the loading type!
If I well understud we talks about a normal sealed or reflex (i cant see in deep the box if its open in the middle of the angle) for optimize spacing and number of driver/speakers!
it seems that u know well this cab... so how its sound in the mid-woofer part?
Im looking for a solution from 200 to 800-1000hz...

Hi Natty,
If you're working in a second language, then no apology needed, you're already doing better than I ever could in a foreign language Smile

The majority of the loading of those 12's will be regular vented - the V loading lets Mackie fit more drivers in a given height and width of cabinet more than anything else.  The vents are the vertical slots alongside the Mid horn at the top of the box. 
There will be a little bit of gain from the cavity in front of the 12's acting like a horn, but that will only put a small peak in the mids, which is a little useful as "free" extra efficiency. As it is an active cabinet (processing & amp built in) I'd imagine Mackie will have taken advantage of that and used EQ to flatten it back down - meaning the amp then has to do less work at those frequencies. Assuming the cavity is a maximum of 30cm deep, I'd expect any such hump would be somewhere in the 280-300Hz range.

The spec sheet for it can be found here: http://technika.czakmusic.pl/wp-content/uploads/2014/12/fussion3000_ss.pdf, which shows Mackie use these 12's all the way from the low end of the cabinet's range up to 500Hz.

I'd be wary of using such an arrangement all the way up to 1000Hz, as the wavelength of sound at that frequency is about the same as the driver to driver spacing, so there is more chance of them not coupling as efficiently, and having some cancellation off axis - depending on how wide you want the coverage to be, that could be a problem.

I think I've only heard these cabs in one venue (which didn't have the best acoustics), and I honestly didn't notice any problems with the sound of them, but as I was only in the audience and not mixing, I can't really be sure.

Good luck,
David.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 4:08pm
Originally posted by Crashpc Crashpc wrote:

  I'm rather looking for mechanical solution. Because at 1500Hz, this coupling and wavelenght stuff gets to "properly sized horn size territory". If I want it to act like point source, the driver with the horn has to be in that V-slot. But as it can only be about 20cm "long" at each dimension there is not much chance to put the horn in, unless one doesn't care about directivity pattern.


Yeah it's a catch 22, you can see with the mackie box that mid horn would completely block the woofers if it was placed in the V so they compromise and put it above. A coax gives you a perfect physical point source between two drivers but there isn't enough room for big enough horn to allow an ideal crossover frequency. The solution is a unity horn, it offers enough room to mount all the drivers and it still acts as a point source.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 4:19pm
Originally posted by Conanski Conanski wrote:

In this case it's all about packaging.. more drivers equals more output simple as that. At the frequencies those woofers operate at the angled baffle has no acoustic effect.. positive or negative.


as others have mentioned too, you get some peaks due to the cavity/bandpasseffect around 200-300hz and a dip/natural rolloff at around 700-800hz..

- one option would be going large HF horn and ideally coax HF driver like bms 4590 etc.
(see tannoy VQ60 or tony wilkes V4M)
- other one would be adding a dedicated MHF to bridge the gap like mackie did
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2017 at 5:42pm
Conanski: with first calculation of dimensions of very compact unity, I found it's not a way for me either, as If I was about to preserve compact size of my liking, drivers wouldn't fit. It would make the horn significantly larger, to fit these in, taking out more volume in the enclosure, and it would end up with very bad compromise or too large for my likings. That's where I started to follow EAW KF394NT approach, but there is no free lunch either, with BMS 2" coaxials. That gets me back to best compromise - v-slot loaded with the HF horn.
I propably will try on my own to see if it can be a way, or it cannot...
Nikon and Canon people should not be married to each other. Why did you let this happen?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 21 September 2017 at 7:08pm
Got to my "final pair" decision. Either go oldschool with B&C 10PLB76 with good driver on some wider horn, or do V-slot with two good 8" and separated HF.
If my first calculations in Hornresp are fine, a tight angle (45 degrees) v-slot crossed at 800Hz would do. The question is, if good strong driver as RCF ND840 can do 800 Hz crossing at 600w for the box too. No idea here. If anybody can help, it's much appreciated.

Edited by Crashpc - 21 September 2017 at 7:09pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 21 September 2017 at 7:26pm
rcf themselves use their high end 3" coil HFs 800hz up on the hf950 horn afaik in some of their cabs..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dlyxover Quote  Post ReplyReply Direct Link To This Post Posted: 21 September 2017 at 7:56pm
I used a Bms 4594nd as the top end in my cab, crossed over At 700hz .

Dose a cracking job
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 21 September 2017 at 8:38pm
Well, HF950 is quite long and generaly large.
I'm striving for compact extremism, so the front baffle will only have max.28cm width (can imagine 28cm wide horn then) and 22-24cm height reserved for the horn. I might even think about 3D printing.


Those BMS coax drivers are awesome, and would do, but price also plays some role. So my question was rather really strict about the 1,4" driver being able or not being able to do the job. On the other hand, those manufacturers put 1200-1600w into their boxes. I'd be around 600-700w, effectively one half with "conscious" usage.
Anyway thanks for suggestions.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Darkstar Quote  Post ReplyReply Direct Link To This Post Posted: 21 September 2017 at 9:05pm
Originally posted by _Natty_ _Natty_ wrote:







Quite similar designs huh? LOL
The above is RCF, with "propetary" mid horn-driver combo.
Bass =/= Enough
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 21 September 2017 at 9:37pm
I had a chance to listen to the RCF model, and to my surprise, didn't like it soundwise more than best two way systems. That was quite a letdown. Had the RCF H100 horn in my two way system too, and there might be something wrong about it. Didn't like it on any "occasion".

Edited by Crashpc - 21 September 2017 at 9:38pm
Nikon and Canon people should not be married to each other. Why did you let this happen?
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