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12" BPH design.

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mobiele eenheid View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2018 at 9:55am
From: https://forum.speakerplans.com/guide-to-winisd-pro-and-hornresp_topic1314_page2.html

Quote Hornresp models the power response of the horn. This is different than the on-axis response which you might measure with a microphone. The power response is what you would measure at a point if sound radiated evenly in all directions away from the horn, within the solid angle specified in the ANG input
In your case you're unlikely measuring truly in 4,0 pi, rather somewhere between 2,0 and 4,0 pi, so expect some difference based on that.

Quote So the modelled results should be fairly accurate up to the frequency where the horn starts to have directivity - where the polar pattern starts to narrow. This is typically at the frequency where the wavelength falls below the diameter of the horn mouth. Above this frequency, Hornresp will predict lower SPL levels than what you would measure on-axis
In other words you can expect the actual on-axis response to have a more rising response, than your sims now show.

Quote Hornresp now includes tools to investigate this effect. Once you calculate the model, go to the SPL Response chart. Under Tools, select Directivity. If you enter a blank input, you will see the power response. If you enter 0, you will see a prediction of the on-axis response. You can also enter other angles. Also under tools, you can look at the Pattern tool. This will predict the polar pattern at the frequency you input and show you the directivity index (DI) at that frequency. The DI is a number in dB giving the gain over what the level of the power response is
For this you need to approximate your horn as a single segment.

If you look at other designs going up till 300 - 350 Hz, you'll see that they are either straight horns or have extra ordinary effort (like phase bungs/ plugs) to keep the Vtc small.

Johan


Edited by mobiele eenheid - 07 March 2018 at 9:56am
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LeruSound View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2018 at 12:36pm
So I will probably convert it to a 15" as i found 15NDL76 as better performance speaker. But this will for sure enlarge my chamber and my throat.. this is not helping much the high freq reproduction.. but I'm still faithful. It's gonna be reverse firing in common symmetrical front chamber, and this should help. I'll try to play on it. Thank you very much Mr Johan!

Edited by LeruSound - 07 March 2018 at 12:37pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2018 at 12:45pm
Originally posted by LeruSound LeruSound wrote:

So I will probably convert it to a 15" as i found 15NDL76 as better performance speaker. But this will for sure enlarge my chamber and my throat.. this is not helping much the high freq reproduction.. but I'm still faithful. It's gonna be reverse firing in common symmetrical front chamber, and this should help. I'll try to play on it. Thank you very much Mr Johan!


I have a pair of authentic Turbosound THL-818, that with right driver and outboard tuning, will make very decent job of 75hz-300hz.

PM for more details.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 23 April 2018 at 2:27pm
So, in the end i went for 15" + 8" + 1". I post here some pics of prototyping and building.













Edited by LeruSound - 23 April 2018 at 2:28pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mini-mad Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2018 at 4:12pm
Very unique looking!! A bright green would REALLY make them stand out!


If it sounds like a gorilla is trying to escape, turn it down.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2018 at 5:22pm
Thank you guys, what i aim is it sound as i wanted.. We see in the end how it performs.. I already had some preview but waiting for those inductors and capacitors, than i realign everything and eq and serius setting.. Already got some confirmations that something has gone out of my plans such as some box rifractions/reflections giving me one unexpected dip in the most precious&delicate band range...

Finitures and paint such as building has nott been directed by me.. I helped but it's still in DIY policy so the guy wanted to use his own skills, and result is nice!! (we really no needed to fix every detail!)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2018 at 7:21am
I wonder how it would look if you added a trim to the edge of the HF horn, a border edge/baffle piece so that it feels more incorporated and less tacked on.


Ideally it would fit flush with the brace and the MF horn panels, so the HF horn wouldn't move at all from it's current position but the gap behind it would be filled in.

Probably too involved a process to retrofit, but if this is a prototype it might be something to think about. No acoustic benefit (well, maybe a very marginal benefit to the HF horn stability that would probably outweigh any negative impact to the BPH), but it could help the cab look more fleshed out/coherent.

If you could manage to get the HF horn sitting flush in this baffle that would be neater still.


Edited by Hemisphere - 25 April 2018 at 7:30am
Phase 1: Post on Speakerplans
Phase 2: ?????
Phase 3: Profit!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2018 at 8:04am
I did that. If you get a look to the XT1086 from 18Sound you see cutout of that horn is almost all the horn large. I did it and it came out very weak due to tiny woods, and also i I didn't wanted to make horn+support structure bigger & bigger.
I.e. the woods & braces behing top and bottom of HF horn are cutted out so the horn is fitting those 2 3 cm inside.


Edited by LeruSound - 25 April 2018 at 8:10am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cravings Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2018 at 10:04am
tell us a little more about the 8". cool project.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 26 April 2018 at 8:53am
8 inches horn has been a pain in the ass. The whole system was supposed to be:
15" BPH from ~100 Hz - ~300 Hz
8" SH from ~ 300 Hz to ~2 kHz
1" CD Horn ~2kHz 

The aim of this system is to get a wide and best possible V dispersion, with a controlled and linear H dispersion, that is still narrower than V (enough to array 2 or more pieces without heavy combs).
Why wider V dispersion? It's for reagge/dub soundsystem, pointsourced at a fixed height, so not an ambient where versatility/sound reinforcement experiments are requied, and i wanted to design a speaker able to deliver a good and coherent translation of sound even 1/2 meters far from the stack, place where usually ppl dance as they get dat fatty bass, the juice of a dub/reggae party. One way is to easily angle a little FWD the tops cab, but it depends, not always is easy and pleasant to do.
So my researches went in asymetrical horns, and i learned is not a common topic, neither a proper way to do, as it ended up that is easyer to angle a symetrical horn rather than find complex geometries to bend the wavefront down.

Btw, i wanted to try, so reading a lot and modifying my initial idea, i finished to get that design + 8" cutted/molded phase plug (5 to 8 mm far from cone), that fills Vd of speaker and splits in two the paths vertically. That helped a lot in HF, cause horn has kind of large mouth, so off axis freq above 1 kHz were killed, on axis were killed around 1,5 kHz; more than 2 kHz after the phase plug. Directivity has gone as i expected, i got a something more or less good till 1.6 kHz in lower V axis, while it is killed above 1 kHz above V axis. I did these tests with that horrible prototype u see in first pic, but with the entire cab i got some refraction/reflection with BPH and i destroyed something in 1 kHz band, very sad as it was crucial point between what was good and what i achieved with ph.plug and horn modelling...

For may reasons (weak directivity results at HF in 8 inches horn mianly) i decided to move the cuts as this with these drivers:

15" BPH 15NDL76 - 280 Hz
8" SH 8PE21 - 280 Hz to 1.4 kHz (still to decide if to move up or stay like this)
1" CD horn DE550 mylar + XT1086 18Sound, same cut as above.

I now need to test the whole system with passive xvoer (from 15" to 8", very difficult decision that had to be taken) and i can spend some more words on final results.





Edited by LeruSound - 26 April 2018 at 10:40am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 06 August 2018 at 2:57pm
This is some result i obtained from last measurement. Quite a bit of processing has been needed, but nothig CRUCIAL :D (Global polarity should have been reversed, but this is just a screenshot i got by the hurry)




Edited by LeruSound - 06 August 2018 at 2:59pm
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 06 August 2018 at 4:39pm
That is quite a complex built for a box that dies at 150hz.
Marjan Milosevic
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