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Anyone help with scripting this?
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Disco Stu View Drop Down
Old Croc
Old Croc


Joined: 03 March 2005
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    Posted: 30 September 2010 at 11:29pm
Ok so a while ago I got put onto a horn design where the rear chamber vents into the horn throat via a slot, and gain is therefore added to this by the horn, meaning you keep most of the efficiency of the hornloaded section (up to 105dB with a 15" driver on a 1-1.2m horn) but you also get the benefit of the horn adding gain to the port output as well, which might bring the response up to say 100dB which I believe is better than porting to the outside world directly. 

I thought it was a good idea at the time and still do now. 

So can anyone help with how to script this idea successfully in AkAbak?

Have attached a quick paint sketch so you can see what I am getting at.



Stu
All you need to know is:
Sensitivity + Power Handling - Power Compression = Max Output

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_djk_ View Drop Down
Old Croc
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Points: 6002 		Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 12:14am
That is not a good idea.
 
BFM tried it years ago and reported his results in Speaker Builder magazine.
djk
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numtie View Drop Down
Young Croc
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Points: 585 		Post Options Post Options   Thanks (0) Thanks(0)   Quote numtie Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 12:40am
yer wouldnt you get a weird phase issue with something like that so maybe something more along the lines of
Disco Hire Wales
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_djk_ View Drop Down
Old Croc
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Points: 6002 		Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 2:06am
You can model that as a TH in Hornresp.
djk
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numtie View Drop Down
Young Croc
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Points: 585 		Post Options Post Options   Thanks (0) Thanks(0)   Quote numtie Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 2:15am
i woulnt even know where to start
Disco Hire Wales
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Louder than loud View Drop Down
Old Croc
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Stern Smile
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Disco Stu View Drop Down
Old Croc
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Points: 2487 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 7:25am
Numtie what you have drawn is just a kick horn no?

The horn I am talking about has actually been built in multiples and is being used successfully by another forum member.

Incidentally DJK can you remember how long was the horn in BFMs case.... did it have a front chamber? How many different configs were tried?

Stu
All you need to know is:
Sensitivity + Power Handling - Power Compression = Max Output

My acts:
www.myspace.com/thebowiexperience
www.myspace.com/scheisseelektronisches
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snowflake View Drop Down
Old Croc
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Points: 3122 		Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 12:09pm
Stu,
 
model it as a horn with a vented rear chamber, export to akabak and then change the node connections on the vent duct to connect it to the mouth of one of the horn sections. I've modelled and built similar but with the vents just 12cm from the mouth of a 60cm horn. see 15" ported horn thread in new projects forum.
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numtie View Drop Down
Young Croc
Young Croc


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Points: 585 		Post Options Post Options   Thanks (0) Thanks(0)   Quote numtie Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 1:34pm
proabbly im not really a desighner i thought you was just trying to make use of the rear chamber. to be amplified within the horn mouth. I was just thinking that maybe you could make it so that the rear chamber came round to the front and meet the rear of speaker driver hakl a cycle behind thus making it into a sort of push pull/horn thing but blatenly im waaaaaaaaaaaaaaay of the mark.
Ill get ma coat.
Disco Hire Wales
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Disco Stu View Drop Down
Old Croc
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Points: 2487 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 3:42pm
Hi Snowflake are you able to post the function that I would need to add to the AkAbak script of where I would "tap" the port back into the horn?

Ideally it would be at or before S1. I had been trying to model this in Hornresp before but modelling the port output seperately using a front chamber volume approaching infinity and then overlaying the two plots to see how they combine, but it would make more sense if there was a way to model it fully so I could play a little more. It seems that the length of the horn is particularly relevant, if you can get 105dB at 85Hz with only a 60cm horn then perhaps the horn of 1.2m I am modelling is too long, because the response is no better but it is much larger. Either that or the driver is wrong, either way would like to play a little more but don't have the AkAbak skill at the moment.

Stu
All you need to know is:
Sensitivity + Power Handling - Power Compression = Max Output

My acts:
www.myspace.com/thebowiexperience
www.myspace.com/scheisseelektronisches
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Jake_Fielder View Drop Down
Old Croc
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Points: 4231 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Jake_Fielder Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 4:01pm
Originally posted by Disco Stu Disco Stu wrote:

Numtie what you have drawn is just a kick horn no?
 
he has shown it with the back of the driver open though, not in a chamber, directly into the hornmouth
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Ibex View Drop Down
Young Croc
Young Croc


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Points: 1013 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Ibex Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2010 at 5:24pm
Originally posted by _djk_ _djk_ wrote:

That is not a good idea.
 
BFM tried it years ago and reported his results in Speaker Builder magazine.


@djk
Please, would you be so kind to post the related article of the magazine?


Once I read that someone successfully ported a w-bin at the throat.
I only know one commercial product that makes use of a into the front chamber ported rear chamber, it's the Föön V387HLC.

Both designs are utilizing a relatively short horn of only ~80cm path length.
Anyway you should take care that the port area is smaller in comparison to the cross sectional area of the horn path where the port is tapped, otherwise the horn will increase the length of the port and the tuning will be lower than expected.

gzg
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