Okay... I have designed a 60litre for for a Peerless 12inch XLS sub (830500) The total internal volume is 100litres, due to the volume taken up by the port....
Below is a picture..
I have a few questions, is it okay to have a 90 degree angle in the port??
BTW. It took me about an hour to work out how to do this... the final total internal volume is 63litres... then you have to account for the speaker..
the box is tuned to about 29 - 31 Hz.... the final thing will be a 52cm X 52cm X 52cm cube with a slot port the full width of the internal dimension, which btw is 47 cm as I designed the box to use 25mm MDF walls... is there any problem with the design? I thought it was pretty good.. got the volume spot on, and I believe I got the tuning right....
THE OTHER QUESTION!!
How do I measure the length of the port? I personally worked it out by the volume... I knew it had a constant cross section of 47cm X 5cm so I worked out the same volume for straight as bent.. ALSO!! is the gap between the internal end of the port and the speaker baffel big enough? is it a bad idea to have the port sortof facing the rear of the woofer???
THANX!
Below is a picture..
I have a few questions, is it okay to have a 90 degree angle in the port??
BTW. It took me about an hour to work out how to do this... the final total internal volume is 63litres... then you have to account for the speaker..
the box is tuned to about 29 - 31 Hz.... the final thing will be a 52cm X 52cm X 52cm cube with a slot port the full width of the internal dimension, which btw is 47 cm as I designed the box to use 25mm MDF walls... is there any problem with the design? I thought it was pretty good.. got the volume spot on, and I believe I got the tuning right....THE OTHER QUESTION!!
How do I measure the length of the port? I personally worked it out by the volume... I knew it had a constant cross section of 47cm X 5cm so I worked out the same volume for straight as bent..
ALSO!! is the gap between the internal end of the port and the speaker baffel big enough? is it a bad idea to have the port sortof facing the rear of the woofer???THANX!
Attachments
personaly i hesitate using a driver that wants such a tiny box with mid tuning and a LONG port.It wastes the 18hz Fs and low efficiency which accompanies the low resonance.
adrian mack <www.geocities.com/adrian_mack >
mentioned this to me,about his PR'd XLS12,how its nearly impossible to build it with a port to optimum specs.
i attempted a ported design,but i always ended up compromising it.
if your using winisd,you could save the project,and add as attachment so i can look over it to ensure im using same inputs.
i expect Group delay to be abit high...
personaly id go for the lower quality shiva in a more comfortable sized box tuned to 22hz without 4metre long ports
adrian mack <www.geocities.com/adrian_mack >
mentioned this to me,about his PR'd XLS12,how its nearly impossible to build it with a port to optimum specs.
i attempted a ported design,but i always ended up compromising it.
if your using winisd,you could save the project,and add as attachment so i can look over it to ensure im using same inputs.
thats fine
yes
i expect Group delay to be abit high...
personaly id go for the lower quality shiva in a more comfortable sized box tuned to 22hz without 4metre long ports
also i think for shelf ports you minus 0.5x port height from the total length because it has different loading to usual.
if im wrong,my jbl2226h is still tuned exactly right with a shelf port anyway
www.jlaudio.com ;tutorials;
if im wrong,my jbl2226h is still tuned exactly right with a shelf port anyway
www.jlaudio.com ;tutorials;
i made a spreedsheet that worked out all my volumes for me,saved alot of time.
also,your group delay is alittle high. 27ms.
i would think about using a smaller sized port for only 75cm length approximately.<trade off port speed,but makes it more managable>
it will never be the best, why not save for a PR and tune 19hz?
i had to wait ages to get my jbl2226..
or u cud just get a shiva in 120Litres...
also,your group delay is alittle high. 27ms.
i would think about using a smaller sized port for only 75cm length approximately.<trade off port speed,but makes it more managable>
it will never be the best, why not save for a PR and tune 19hz?
i had to wait ages to get my jbl2226..
or u cud just get a shiva in 120Litres...
Using:
Fs=28
Qts=.3
Qes=.32
Vas=81L
Re=1.8
Dia=24.75 (guess)
Xmax=12.5
Ql=15, Qa=30, Qp=30
I modeled in my spreadsheet a 60Liter box tuned to 30Hz.
I got:
F3=32
Power handling 28Volts RMS+ (450watts+ into 1.8 ohms) at 26Hz+.
Excursion at 40Volts Peak (28VRMS) was 11mm at ~41Hz (this is the max above resonance). Excursion follows voltage so at 20V peak it would be 5.5mm.
Vent velocity was 14m/s peak at ~27Hz. with 40Volts peak input, assuming a 47X5cm vent.
Group delay was ~45ms at ~29Hz. This confirms insidious errors still exist in winISD - unless a different box/tuning were used by "mikeported"
Group delay is not important anyway, so I wouldn't worry about it. The resonant decay in your room is probably on the order of seconds, not milliseconds. The room decay is usually overwhelmingly worse than box group delay. The audibility is still a contentious issue among those who think they know what the term means.
Your mileage may vary.
Please note: Peak=RMS*1.414
Fs=28
Qts=.3
Qes=.32
Vas=81L
Re=1.8
Dia=24.75 (guess)
Xmax=12.5
Ql=15, Qa=30, Qp=30
I modeled in my spreadsheet a 60Liter box tuned to 30Hz.
I got:
F3=32
Power handling 28Volts RMS+ (450watts+ into 1.8 ohms) at 26Hz+.
Excursion at 40Volts Peak (28VRMS) was 11mm at ~41Hz (this is the max above resonance). Excursion follows voltage so at 20V peak it would be 5.5mm.
Vent velocity was 14m/s peak at ~27Hz. with 40Volts peak input, assuming a 47X5cm vent.
Group delay was ~45ms at ~29Hz. This confirms insidious errors still exist in winISD - unless a different box/tuning were used by "mikeported"
Group delay is not important anyway, so I wouldn't worry about it. The resonant decay in your room is probably on the order of seconds, not milliseconds. The room decay is usually overwhelmingly worse than box group delay. The audibility is still a contentious issue among those who think they know what the term means.
Your mileage may vary.
Please note: Peak=RMS*1.414
ron e where did u get ur specs from,i thought this was 12inch XLS
Fs=18hz Qts=0.2 ! and a larger vas.
hehe im just quoted adireaudio about high GD
also sense says that 30ms + cant be good
perhaps in an non reflective non echoic room you could hear it.
personaly i cant say.
i used skinnyboys winisd file.
on winisdpro >perhaps buggy>
download subwoofer simulator,to compare
anyway the point is,it can be done,its just abit dodgy without PR.
proly sound fine.,if u can tune it so it doesnt have a peak ,wil sound nicer i reckon.<more like sbb4> ,just slightly.
Fs=18hz Qts=0.2 ! and a larger vas.
hehe im just quoted adireaudio about high GD
also sense says that 30ms + cant be good
perhaps in an non reflective non echoic room you could hear it.
personaly i cant say.
i used skinnyboys winisd file.
on winisdpro >perhaps buggy>
download subwoofer simulator,to compare
anyway the point is,it can be done,its just abit dodgy without PR.
proly sound fine.,if u can tune it so it doesnt have a peak ,wil sound nicer i reckon.<more like sbb4> ,just slightly.
Whoa!
I screwed up and used the wrong driver - Peerless has another 12" XLS autosound sub with different specs...
Using: (830500)
Fs 18.1
Qts 0.2
Qes 0.21
Vas 139
Re 3.5
Dia 24.75
Xmax 12.5
Pe_max 300
and Vb=60L, Fb=30
I got: F3=29
Power handling more than 300W over 26Hz
Excursion max above resonance 7.3mm at 39Hz with 40V peak input.
Vent velocity 10m/s at 29Hz with 40V pk input.
BTW, Group delay shows 85msec here. for this design, with these specs.
Depending on the goals, I might try this design just to try a folded port - or I might try to tune lower to get rid of the peak in response by either sacrificing port area and living with the possible noise or going with a PR, as others have suggested.
The peerless 12" PR (830548) would be perfect in a ~45-60L box with no added mass. Group delay would be in the 100msec range with the PR...
Have fun - hope I got the driver specs right this time
I screwed up and used the wrong driver - Peerless has another 12" XLS autosound sub with different specs...
Using: (830500)
Fs 18.1
Qts 0.2
Qes 0.21
Vas 139
Re 3.5
Dia 24.75
Xmax 12.5
Pe_max 300
and Vb=60L, Fb=30
I got: F3=29
Power handling more than 300W over 26Hz
Excursion max above resonance 7.3mm at 39Hz with 40V peak input.
Vent velocity 10m/s at 29Hz with 40V pk input.
BTW, Group delay shows 85msec here. for this design, with these specs.
Depending on the goals, I might try this design just to try a folded port - or I might try to tune lower to get rid of the peak in response by either sacrificing port area and living with the possible noise or going with a PR, as others have suggested.
The peerless 12" PR (830548) would be perfect in a ~45-60L box with no added mass. Group delay would be in the 100msec range with the PR...
Have fun - hope I got the driver specs right this time
Ron E : u used the car one ,
are u using winisd? what version exactly.i really should compare it to sub sim and any other prog i can get my hands on.i sitl have dosbox,from 1991
thats expensive mdf! i used 48$ for my 175L jbl box with 2 braces and shelf port <about 1.4sheets>
ohh.
ididnt realise the foam surround was that bad-have u heard a few horror storys? if its so bad,howcome its sold so freely in Oz
in the adire pdf it says'should last in excess of twenty years' if i remember correctly,dont quote me.
that isnt very long
are you sure theres no other choices? is the tempest foam surround??
what about the DPL12 is it foam too/?
youd think that there would be more choice in Oz! im in nz,and theres nothing to choose from!.
i really am not sure about such long ports. taking up half the box volume, with high GD ,and in the end it only does 30hz....
which a jaycar carbon fibre 12 will do<its efficient too>
,but i did hear about some oen who was measuing the SPL of one of them,and while he took notes on spl level, the thing blew
are u using winisd? what version exactly.i really should compare it to sub sim and any other prog i can get my hands on.i sitl have dosbox,from 1991
thats expensive mdf! i used 48$ for my 175L jbl box with 2 braces and shelf port <about 1.4sheets>
ohh.
ididnt realise the foam surround was that bad-have u heard a few horror storys? if its so bad,howcome its sold so freely in Oz
in the adire pdf it says'should last in excess of twenty years' if i remember correctly,dont quote me.
that isnt very long
are you sure theres no other choices? is the tempest foam surround??
what about the DPL12 is it foam too/?
youd think that there would be more choice in Oz! im in nz,and theres nothing to choose from!.
i really am not sure about such long ports. taking up half the box volume, with high GD ,and in the end it only does 30hz....
which a jaycar carbon fibre 12 will do<its efficient too>
,but i did hear about some oen who was measuing the SPL of one of them,and while he took notes on spl level, the thing blew
Mike,
I use my own spreadsheet, which is similar to unibox, but better for my uses because I know how it works and exactly what the input and output mean. I have verified it correct against LEAP simulations.
With either Unibox or subsim you should get the same results as my program, when the inputs are the same. I have found a number of errors in winISD, Bassbox 5, and other programs with my spreadsheet.
I downloaded winISD pro alpha to see if it was an improvement over the beta, and I t is better, but it still seems to have some errors. The shape of the excursion and group delay curves looked better than the old winISD, but the values were still not correct, IMO.
Subsim is much better than WinISD, IMO. Isaac's work factors in VC inductance, which is unprecedented in a free program.
I don't think anyone knows how long foam surrounds will last. My foam surrounds from 1988 just rotted a year or so ago. It is pretty easy to refoam, and the driver weill probably want replacing after 10-15 years anyway, so I don't worry about it much.... I have seen 15 year old rubber surrounds that are checked and torn (and they can also harden and change properties), so I don't think they are all that much better.
If you want long lasting speakers, you need to get speakers with cloth surrounds. You won't find too many high excursion drivers with these, so...
Reportedly the problem with foam rot is a fungus, so perhaps treating with fungicide would make them last longer, but I have never tried it.
I use my own spreadsheet, which is similar to unibox, but better for my uses because I know how it works and exactly what the input and output mean. I have verified it correct against LEAP simulations.
With either Unibox or subsim you should get the same results as my program, when the inputs are the same. I have found a number of errors in winISD, Bassbox 5, and other programs with my spreadsheet.
I downloaded winISD pro alpha to see if it was an improvement over the beta, and I t is better, but it still seems to have some errors. The shape of the excursion and group delay curves looked better than the old winISD, but the values were still not correct, IMO.
Subsim is much better than WinISD, IMO. Isaac's work factors in VC inductance, which is unprecedented in a free program.
I don't think anyone knows how long foam surrounds will last. My foam surrounds from 1988 just rotted a year or so ago. It is pretty easy to refoam, and the driver weill probably want replacing after 10-15 years anyway, so I don't worry about it much.... I have seen 15 year old rubber surrounds that are checked and torn (and they can also harden and change properties), so I don't think they are all that much better.
If you want long lasting speakers, you need to get speakers with cloth surrounds. You won't find too many high excursion drivers with these, so...
Reportedly the problem with foam rot is a fungus, so perhaps treating with fungicide would make them last longer, but I have never tried it.
When living in L.A. in the 70's I saw a lot of foam rot. I always suspected, but could not prove, that the cause was air pollution.
I just did a search and came up with this from JBL:
One of the most common problems with older speakers (foam edge type), is the serious degredation of the outer foam ring. It deteriorates over time, and is mainly due to ozone and pollution agents in the air.
I just did a search and came up with this from JBL:
One of the most common problems with older speakers (foam edge type), is the serious degredation of the outer foam ring. It deteriorates over time, and is mainly due to ozone and pollution agents in the air.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.