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best choice for a 12" horn plans

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gen0me View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 23 October 2017 at 10:01pm
Its front loaded. Vtc can be measured/calculated. Atc is here some stupid value as front chamber is as small as possible. Distance from suspension to s1 is few times shorter then deepth of membrane. Than how to figure out length from membrane to s1 and Atc?
It may be use same way as Lrc influence resonances. So with Atc = 250-450 you are in reasoneable range that change wont influence you.
Vtc just as small as you can get in design. There is a vtc calculator from membrane shape in hornresp. Check in tools in input window.
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_Natty_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 24 October 2017 at 10:35am
i cant understand why in simulation of TDA version there is a so high value, even i read that "horn resp simulating the speaker as plane pistone surface" so how can this number be part of the calculation, and why speaker builder do not give this value is strange... even the graphic simulation seem to draw a front chamber at high value of this number.... and having a front chamber is a things that many doing or I wrong? I still asking about this, because when I add some random number the things help me a lot to have a flattern response than having just one segment horn.

what im doing is to set the Area bigger like S1 and acting on volume... but maybe is just a wasting of time!
what Im trying to understand if i'm trying to source out a flatten response with a speaker that may is not so flat....in term of response

today i will try some reflex enclosure, starging from bass box 6 sims
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 24 October 2017 at 11:02am
Sorry yes driver front loaded. Unless your a beyma fan who refer to the panel not the driver and it would be rear loaded lol. Yeah not sure what’s going on in the tda sim. Can’t be correct.
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gen0me View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 24 October 2017 at 12:04pm
Maybe he didnt know. Its hard to figure it precisely. How about measuring it with beans?

The speaker is very flat I simmed it in Abec. 12MH32. On last plans looked super flat. Maybe simplified version(without bend) suffers from midband waste banding.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 24 October 2017 at 2:27pm
Originally posted by _Natty_ _Natty_ wrote:

  • my driver is 3,3L of volume
  •  mt130 have VRC= 14,81 LRC=13,6
  • mt121(both TDA and classic version) have VRC= 17,6 LRC= 14,8
both are suitable for driver like pd121 
so pd121 VS b&c 12mh32 are:
  • fs=53hz ->>>>>>>>>>>>>>>> fs=53
  • vas =66,5L->>>>>>>>>>>>>> vas=63
  • cms = 168.33 µm/N ->>>>>>>>cms= - (value calculated from hornresp)
  • qts = 0.23->>>>>>>>>>>>>>>qts=0,19
  • deep of basket= 115mm->>>>>deep of the basket=133mm
so maybe i need more space on the back due the longest basket, but it seem that i've a lot of benefit in keeping low the value of the volume inside the box something around 11l give me the best benefit but it seem almost impossible to fit a 12" in a little box like that...
So i made some test in between 15 -30l and it seems that something around 20-22l give me good results. (I try this in winIsd, bass box pro 6 and an online calculator).

is it a good way to proceed?

I would still be a little concerned about trying to run a driver hard in such a small rear chamber as the 2 designs you link above, but if other people have made it work then perhaps I'm just being too cautious.

Modelling a direct radiating driver isn't going to give you an ideal rear chamber size for a horn, no, so just adjust Vrc in Hornresp to model that.

Quote
Yes, exactly that. So, for a 12" driver with Sd = 522, you'll be 522 x whatever the depth of the cone is, less an amount for the fact that the cone sides slant inwards towards the dustcap. Again, you can model this in Hornresp to see the effects of different values for yourself - as long as you use a realistic value it won't make too much difference. Try modelling say 800 vs 1200 (per driver, so 1600 vs 2400 for the whole box) - that is probably the range you need to stay in.

EDIT: thanks to gen0me for pointing out that Hornresp has a calculator for this, you can measure your drivers and get an exact value so no guesstimating required Thumbs Up

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I think it's better to model that as the first segment of the horn, as it does have some expansion.
S1 would be the area at the start of the 13cm length - ie 27.3*6.8cm or 185.6 cm2.
S2 is the area at the end of the 13cm - 33*8.5 or 280.5cm2 with L12 = 13.
S3 is the area at the mouth - 33*50.8 = 1676.4cm2 with L23 = 40.5.


Edited by DMorison - 24 October 2017 at 2:32pm
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_Natty_ View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 25 October 2017 at 10:48am
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I would still be a little concerned about trying to run a driver hard in such a small rear chamber as the 2 designs you link above, but if other people have made it work then perhaps I'm just being too cautious.

Modelling a direct radiating driver isn't going to give you an ideal rear chamber size for a horn, no, so just adjust Vrc in Hornresp to model that.

This is about hornresp behavior? 
because I read in many books that design an horn can be done by split the problem in 2: 
  1. design the rear chamber with a proper tuning 
  2. design/optimize the horn using that back chamber


Edited by _Natty_ - 25 October 2017 at 10:50am
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DMorison View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 25 October 2017 at 2:02pm
Originally posted by _Natty_ _Natty_ wrote:

Quote
I would still be a little concerned about trying to run a driver hard in such a small rear chamber as the 2 designs you link above, but if other people have made it work then perhaps I'm just being too cautious.

Modelling a direct radiating driver isn't going to give you an ideal rear chamber size for a horn, no, so just adjust Vrc in Hornresp to model that.

This is about hornresp behavior? 
because I read in many books that design an horn can be done by split the problem in 2: 
  1. design the rear chamber with a proper tuning 
  2. design/optimize the horn using that back chamber

The heat problem is nothing to do with Hornresp or even horns, but applies to every enclosure type.

If you run anywhere near full power into any driver, the voice coil gets very hot. (Think how hot even a 40W domestic light bulb got when it had been on for a while, before we all switched to low energy types.)
That heat has to go somewhere, otherwise the driver's performance is degraded (power compression) and eventually damage may occur.
The vents on the back of the driver are there to allow air movement to help carry away some of the heat, but they can't work properly if the back of the driver is too close to the back of the cab.
As I said earlier, JBL recommended several cm of gap, not just a few mm.

If you want to be sure, contact B&C and ask them directly.

Regarding splitting the design process into 2 stages, that would definitely have been helpful before programs like Hornresp existed.
The point I was trying to make though was that the type of "optimised" box size for a direct radiating enclosure (either sealed or vented) is not necessarily the best rear chamber size for a horn, so using WinISD or BB6 as you said you did earlier isn't as helpful as you may have thought.

Now that we do have programs like Hornresp that allow you to model everything together, there's less need to do that - just make sure that your Hornresp models have a realistic rear chamber volume. 15l per driver does sound a lot better that what you had a few pages ago, it is physically practical and does give you about 4 or 5 cm clearance behind the driver for cooling, so it should avoid the worst of the heating problems reasonably well.
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gen0me View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 25 October 2017 at 2:26pm
Also. If yo are building rear chamber try to make all dimensions relatively even from a driver becouse then length from membrane to the walls is minimised so the 1st standing wave resonance is moved to higher frequencies.
Here is example with scale:

Its 573hz
30.5cm is ~half of a wavelength.

Edited by gen0me - 25 October 2017 at 4:10pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mikkel Quote  Post ReplyReply Direct Link To This Post Posted: 25 October 2017 at 3:05pm
Im sorry to hijack but its fairly relevant to the discussion at hand. I have heard 10-15mm from driver to rear of enclosure is fine for cooling for low to medium power mid drivers. Im assuming it depends on how much air is being moved, i.e. a driver with 2.5mm excursion at full volume wouldnt need several cm clearance. Or am i wrong?
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_Natty_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 25 October 2017 at 3:12pm
even nowadays the ceramic/ferrite part in b&c speakers have nice holes thats helps a lot in cooling! for example my super scooper are so tiny for 18tbx and we talk really about few mm from the insulation! when i push harder, yes i see some burning over the wall! but the speaker still roaring after 10 years of hard gig!
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_Natty_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 18 December 2017 at 2:44pm
 Still very busy, but the works goes on! 
and now Ive some better simulation, and a lot tips on this thread here now have a lot of more sense to me! 

 Just a one more quick question,
 I need to build 6 of them, and now im challenging with 3 options: 

  1. straight exp 1segment horn ---> easy to build
  2.  straight exp 3 segement horn with a tiny duct in front of the chamber long 7-10cm circa but straigth no expansion ---> not so easy to build but best performance on paper 
  3. staright exp 3 segment horn with 3 different expansion---> more simple than the one before but not so "perfect" on paper; 

The back chamber is the same for all 3 model, so in my mind there is about: 
 -building the back chamber with 18 or 15mm 
-building 3 different mouth/horns with the tinyest wood to make some meausurement without closing it in a box;  this kind of approach have some sense? wich is the littlest thickness of the wood that i can Use? consider that i found a place where i can easy cut by laser woods, but i cut 18/15mm wood cost 4 times than cutting until 10mm. 0,5mm is so cheap!!!!! I meant that for the same project asks from 65eu to 10eu!!!!




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_Natty_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 03 July 2018 at 10:58am
 
when u have a lot of things to do times passes.....
so finally i've all the things that i need, and just for a check I put all the things together and some random ideas comes:

about numbers:
-if i put 2 scoop i need 2 12"
-if i put 3 or 4 scoop i need 4 12"
-if i put 6 scoop i need at least 8 of them

-if ill put all in a box it will be so hard do climb the stack: the stack is 182 cm tall and the speakers are 15kgs and some kgs of driver -another 5-6kg circa- so it will be about 20kgs circa without the wood...how much kgs can I rate for a project like that? -we can take a project like mt122 as esample- plus the tops part!
most of the times we are in 2 for moving and build up the stack

-if Ill put just one box over the stack the emission point will be in the center of 2 scoop and 2 es18bph, it will be a sufficient dispersion on the 12" and 2" or is best to split and having 2 boxes angled? or again just one but with the 12" in horziontal instead than vertical as the pic. In fact thats our actual configuration as u can see on this pic...


In this months i read a lot and ive tried to understand better directions and coverage of an horn, but ive seen that is almost impossible to predict with not professional and expensive software or again with builds and measurement from different points...but is not in my pocket possibility

but a wish is to keep al togheter !!!!!

so actually Ive 2 idea in my mind, or going in MT-121 TDA so about just 1 12" one 2" and tops, with a modedd horn

or

going for something like that 
http://i68.servimg.com/u/f68/19/38/08/36/tda_au10.jpg
plus the "driver part" in separated units

or going for the orginal project 2 horns 12" in a layout like the one showed on the first pic, that will be about a polar double 12" horn a 2" and some tops....

goals:

-keep as much things possible togheter;
-possible meant not too heavy
-having a good dispersion
-not too complicated to build up
-avoid comb filters

-12" from 150hz170 to 1khz


Edited by _Natty_ - 03 July 2018 at 10:59am
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