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1850horn rear chamber size?

Printed From: Speakerplans.com
Category: Plans
Forum Name: 1850 and 186 horns
Forum Description: Discussion / Questions about the 1850 and 186 horns
URL: https://forum.speakerplans.com/forum_posts.asp?TID=2424
Printed Date: 28 March 2024 at 5:21pm
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Topic: 1850horn rear chamber size?
Posted By: Sencesync
Subject: 1850horn rear chamber size?
Date Posted: 20 August 2005 at 8:26pm
anyone know how much volume the rear chamber is for the 1850horn?



Replies:
Posted By: rastaman
Date Posted: 20 August 2005 at 8:30pm
1 litre = 1,000,000 millimetres cubed


Posted By: Sencesync
Date Posted: 20 August 2005 at 8:39pm
Rastaman, thats NOT what im looking for. im looking for the rear chamber volume size. not the convertion for millimeters to litres...


Posted By: Sencesync
Date Posted: 20 August 2005 at 11:51pm
see this is why im trying to get the info from others. because i keep comming up with 69.74 litres no matter how many times i check it. and i HIGHLY doubt that thier is nearly 2.5cuf (70.8 litres) of rearchamber space in the 1850horn. so please tell me other-wise because i dont believe that there is that much room, it would seem like there should be less room.


Posted By: rastaman
Date Posted: 21 August 2005 at 10:12am
Ballpark it, it looks not bad to me.

Take the 3 largest measurements of the rear chamber as if it were a cube, you get about 87l, take the 3 smallest you get about 56l.

Somewhere Rog talks about designing short horns as a sealed box unit first, which for the 1850 recommended enclosures are 90-220.

Course I could be making the exact same mistakes as you, but oh well.


Posted By: Timber_MG
Date Posted: 21 August 2005 at 3:53pm
Subtract the volume occupied by the driver.  Other than that, high scool geometry will get you to the answer fairly quickly.


Posted By: rastaman
Date Posted: 21 August 2005 at 4:24pm
Yeah Rog says in the FAQ a standard 18" will occupy about 7litres if memory serves. Seeing as he specs the 1850 for just about everything, thats probably his standard 


Posted By: Timber_MG
Date Posted: 21 August 2005 at 5:02pm
I'd expect that spec from PD, though to be truly exact one would have to look at a little more detail (like thickness of the wood its being mounted in)


Posted By: tb_mike
Date Posted: 28 August 2005 at 2:57am

Originally posted by Timber_MG Timber_MG wrote:

I'd expect that spec from PD, though to be truly exact one would have to look at a little more detail (like thickness of the wood its being mounted in)

if you were one who must split inaudible hairs that is



Posted By: loophole
Date Posted: 10 September 2005 at 9:01am
not that inaudible mike.
an 18" hole in a double-thickness baffle (ie 36mm) is over 5 litres. certainly not incondsiderable

i measure the rear chamber to be about 68 litres too. that seems about right, but im almost certain the pd1850 must be more than 7 litres... i would say about 15-20 is more along the right lines. and even that seems small compared to how much space it visibly takes up in the chamber


Posted By: minaximal
Date Posted: 16 September 2005 at 7:36am

i contacted mark from pd a while ago, and he said they work on a volume of approximately 6 litres of displacement from the 1850, i worked out the concave cone area to add up to around 3 litres to the throat area.

looking back at my old spreadsheets: if the baffle hole for an 18" is 43cm dia, and 1.8cm deep, thats 2.6l on top of 3 litres, before counting the actual throat area.

although dont forget the pistonic motion of a driver increases and decreases the area with each stoke...

haha nothing is that simple, and these are things which can easily get forgotten.




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