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Where is the throat in this plan? |
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mykey 
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Joined: 18 August 2005 Location: UK/Indonesia Status: Offline Points: 9680 |
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 Posted: 01 December 2007 at 3:46pm |
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the compression chamber is what the speaker is sitting in like Tony has said
Dr. do you mean throat compression chamber? because on that drawing there isn't one, unless you count 18mm as a chamber, I wouldn't bother
its just rear chamber throat and horn
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kpippen
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Joined: 04 July 2007 Location: United States Status: Offline Points: 174 |
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Posted: 01 December 2007 at 3:53pm |
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Hi Guys,
Mind if I join the party?... IMHO,..The throat chamber is the area (VTC cm3) that is bounded by the steepest part of the "> angle" at the top right corner of the of the cabinet,...and by the edge of the left side of the cone (all of the area directly above the cone and to the right of it) The area for calculation of S1 cm2 is bounded by the throat chamber at the edge of the left side of the cone... Compression ratio is the driver SD cm2 divided by S1 cm2... S1 cm2 is the cross section area (HxW) at the edge of the left side of the cone...
 Kevin Edited by kpippen - 02 December 2007 at 3:58pm |
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turn on, tune in, drop out
Hey Nipper,...we gotta have more cowbell!!! |
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mykey
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Joined: 18 August 2005 Location: UK/Indonesia Status: Offline Points: 9680 |
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Posted: 01 December 2007 at 4:38pm |
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Take the driver out of the picture, stretch the folded horn into one straight horn
where does the horn start?
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kpippen
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Posted: 01 December 2007 at 4:47pm |
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Mike,
The first section of the horn (S1) starts at the edge of the left side of the cone...
 Kev Edited by kpippen - 01 December 2007 at 4:49pm |
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turn on, tune in, drop out
Hey Nipper,...we gotta have more cowbell!!! |
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mykey
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Joined: 18 August 2005 Location: UK/Indonesia Status: Offline Points: 9680 |
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Posted: 01 December 2007 at 4:52pm |
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ok kev
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mykey
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Posted: 02 December 2007 at 5:15pm |
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If the red circle area to the left was a greater size (cm2) than the area of the blue circle
then you couldn't count the wedge shape as a compression chamber
I thought this area (110mm) was a greater size, its not.
I have just worked out the area of the left red circle and its 660 cm2 and the blue circle throat roughly is 1385 cm2
then you could say that the area marked with the red circle to the left is a throat because its a smaller area
then the throat compression chamber would be the wedge shape in front of the driver
and the horn would start from this point marked with the left red circle
the throat compression chamber is 1788 cm3
would be interesting to see both ways in horn response to see if there is much of a difference Edited by mykey - 03 December 2007 at 1:13pm |
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kpippen
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Posted: 02 December 2007 at 7:53pm |
Mike,...If you looked down at the top of the cabinet and drew a straight line (600mm long)across the interior cabinet width at the left side edge on the cone (approx where the dotted line is just left of the red circle to the right) that would be the start of the horn... Now,...the cross sectional area at that point which would be 60cm X approx 8cm = 480cm2... The PD1850 has a SD of 1150cm2 this means the compression ratio (1150/480) is approx 2.3:1... Just for comparison the compression ratio of the punisher is 2.5:1... This doesn't imply that the punisher is a better horn but it should have the capability for higher SPL... Yes,...the entire wedge shape directly above the driver bounded by the edge of the driver cone on the left and bounded by the end of the wedge on the right is most definately the throat chamber...
Anyways,...This is a pretty difficult horn to model without drawing it up in AutoCAD... So this is mt best estimate using my abacus...:) The TS parameters I found didn't give the LE value for the vc and this usually plays a major role in the response curve...
  Kev
Edited by kpippen - 05 December 2007 at 8:24pm |
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turn on, tune in, drop out
Hey Nipper,...we gotta have more cowbell!!! |
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Jake_Fielder
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Posted: 03 December 2007 at 10:23am |
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hmmmm confusing....
So how would I work out what the throat area and throat compression chamber size (if there is one?) is on design like this??
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minaximal
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Posted: 03 December 2007 at 1:36pm |
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i believe...
as explained above by mike and jake you would see all you have done is added an extra piston into the throat chamber, and i would count the volume inside the drivers. for an 18" at around three litres, add it to the volume of the throat chamber, apart from that the other factors are the same but you have now increased the compression ratio. 110mm x 600mm = throat of 660cm2 (to the left of the driver) 2xpd1850 sd = 2300/660= comp ratio of 3.4-1 which is very high for 18" drivers!! but now you also have a larger volume. dont forget that an 18mm x 18"(430mm diameter) baffle cutout is 2.614litres and to confuse things, if the v wedge of the throat follows a similar linear negative expansion from the horn throat to 0, then the horn can also see this or at least find it hard to distinguish the difference of it as being a part of the horn. in aj horn you can simulate how far down the length of a horn the driver is placed. le 1k in horn resp is not a very important a factor in narrow band bass horns. al |
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mykey
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Posted: 03 December 2007 at 1:40pm |
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I took the overall depth 750mm (75cm) minus 190mm (19cm) leaves 560mm minus 18mm = 524mm
if you look at the drawing where it says 110mm i took that as the throat so 11cm x 60cm x 54.2cm = 35772 then divided by 2 = 17886 cm3 throat chamber
your saying it starts from 8cm instead of 11cm
so it will be 8 cm x 60 cm x 47.2 = 2265.6 divide by 2 = 1132.8 throat chamber
the schematic should look like this
 Edited by mykey - 05 December 2007 at 3:14pm |
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mykey
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Posted: 03 December 2007 at 1:51pm |
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so minimaxil agrees with me where the throat is?
110 x 600 11cm x 60cm
and agreed you should also take into account the cone volume and baffle opening (18mm) as volume Edited by mykey - 03 December 2007 at 1:54pm |
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DrWoofer.com
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Posted: 03 December 2007 at 2:04pm |
If this is the S1 then why the front chamber(starting from left side of cone to the start point at right) has this conical shape? It could be a simpe rectangular. |
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Mykey wrote: