Speakerplans.com Homepage
Forum Home Forum Home > Plans > New Projects Forum
  New Posts New Posts RSS Feed - 12" BPH design.
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

12" BPH design.

 Post Reply Post Reply Page  123>
Author
Message Reverse Sort Order
LeruSound View Drop Down
Registered User
Registered User
Avatar

Joined: 27 August 2015
Status: Offline
Points: 171
Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Topic: 12" BPH design.
    Posted: 09 August 2018 at 2:02pm
Thanks Fred. I always appreciate your precious advices. I had played around with phase plug for a while. I would love to try fill the front chamber even more or try a different phase plug design at least.
You've seen what i've done in previous pictures. I would avoid to model the plug inside the horn, as still throat is very tight (around 40sqcm), i would so try to model something that fills up the front chamber (very small, just the volume of the paper cone) while it splits the phaths and keeps some kind of horn expansion. Any suggestion on that? 



This is how it looks now. The plug stays 0,5 to 1 cm from the cone.



Edited by LeruSound - 09 August 2018 at 2:06pm
Back to Top
FrederikMA View Drop Down
Registered User
Registered User


Joined: 19 July 2017
Location: Copenhagen
Status: Offline
Points: 76
Post Options Post Options   Thanks (1) Thanks(1)   Quote FrederikMA Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2018 at 10:08am
DE550 is a very high quality driver with large voice coil. So with such a high crossover even on a small horn it shouldn't be the cause of distortion.
From the looks of that 8-horn, the rough throat and mouth will cause som very objectionable diffraction/reflections/HOMs.
These kinds of linear distortion are perceptively non-linear and happen in the CD's lower passband, so its quite in line with your subjective observation.

Deffinately loosen up that 8-horn to let it breath a bit. The problems is not really within the effective range of the phaseplug. An 8" driving a straight horn without any compression chamber will go higher than 1,5Khz and also have improved LF response. Once you have the lower mid in order, you can play around with a phaseplug to extend the upper mid response.

I don't mean to talk ill of your attempts, just dont spend money and time fixing the CD-horn non-issue.

Best regards Fred

Back to Top
LeruSound View Drop Down
Registered User
Registered User
Avatar

Joined: 27 August 2015
Status: Offline
Points: 171
Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 07 August 2018 at 1:26pm
I measured, it does go down around 100 /120 Hz. Would say the 1" driver is the source of harshness. Everything up to 1 kHz comes out strong and spread well.  I don't know. Everytime i'm on a hurry doing measurements, cans stay listening for long.. But i would say the tweeter have something strange when plays loud. It is DE550 filtered at 1,5kHz with 24db/oct filter.
Back to Top
mobiele eenheid View Drop Down
Old Croc
Old Croc


Joined: 15 August 2004
Location: Netherlands
Status: Offline
Points: 1568
Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 07 August 2018 at 9:12am
Because it peaks at 150 Hz quit strongly, you should be able to make it go down to at least 125 Hz in an enclosure of similar size. Also, up to what frequency does it sound good?
Back to Top
LeruSound View Drop Down
Registered User
Registered User
Avatar

Joined: 27 August 2015
Status: Offline
Points: 171
Post Options Post Options   Thanks (0) Thanks(0)   Quote LeruSound Quote  Post ReplyReply Direct Link To This Post Posted: 06 August 2018 at 10:36pm
Indeed, that graph has a filter at 140 Hz, but the cab is supposedly to go down to 100Hz.. by the way, I had another measurement today and I have to admit it's not a total winning idea. I would expect it better.. I will try to switch on a bigger compression driver, 1,4 or more probabily 2", cuz it's the sufferinf band when you push it. But 15 + 8 is not bad at all, just I found difficulties in matching the 8 and the 1". Even if i get the cut lower, the 1" doesn't have enough.. will see..
Back to Top
MarjanM View Drop Down
Old Croc
Old Croc
Avatar

Joined: 10 February 2005
Location: Macedonia
Status: Offline
Points: 7809
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
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713
Back to Top
LeruSound View Drop Down
Registered User
Registered User
Avatar

Joined: 27 August 2015
Status: Offline
Points: 171
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
Back to Top
LeruSound View Drop Down
Registered User
Registered User
Avatar

Joined: 27 August 2015
Status: Offline
Points: 171
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
Back to Top
cravings View Drop Down
Old Croc
Old Croc
Avatar

Joined: 30 January 2007
Location: Ireland
Status: Offline
Points: 7439
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.
Back to Top
LeruSound View Drop Down
Registered User
Registered User
Avatar

Joined: 27 August 2015
Status: Offline
Points: 171
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
Back to Top
Hemisphere View Drop Down
Old Croc
Old Croc


Joined: 21 April 2008
Status: Offline
Points: 2272
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!
Back to Top
LeruSound View Drop Down
Registered User
Registered User
Avatar

Joined: 27 August 2015
Status: Offline
Points: 171
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!)
Back to Top
 Post Reply Post Reply Page  123>

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2023 Web Wiz Ltd.

This page was generated in 0.063 seconds.