The original enclosure is rated to go down to 27Hz and is in a 2 cubic foot enclosure. It was a compromise between performance, cost and customer acceptance. My calculations show a bigger box / port for a better response (2.5 cubes / 3"D x 8"L).
We have 2 options.
Duplicate the design as is in a new enclosure.
Build the “optimum” enclosure and make it as good as possible.
What do the more experienced people think?
JBL PB12
Re(ohms) 5.30
Fs(hz) 24.80
Le(mh) 3.44
Qm 8.14
Qe 0.331
QT 0.318
Vas(L) 164.30
Xmax(mm) 4.20
SPL(db) 91.00
BL(Tm) 15.18
Mms(g) 97.81
Cms(mm/n) 0.418
Sd(m^2) 0.053
We have 2 options.
Duplicate the design as is in a new enclosure.
Build the “optimum” enclosure and make it as good as possible.
What do the more experienced people think?
JBL PB12
Re(ohms) 5.30
Fs(hz) 24.80
Le(mh) 3.44
Qm 8.14
Qe 0.331
QT 0.318
Vas(L) 164.30
Xmax(mm) 4.20
SPL(db) 91.00
BL(Tm) 15.18
Mms(g) 97.81
Cms(mm/n) 0.418
Sd(m^2) 0.053
What Happened?
This thread started out about Front or Down Firing subs.
I prefer front myself. Down firing, firing at the wall, corner loading, Ports & passive radiators are all attempts to increase the loudness of under sized woofers at the sacrifice of sound quality (Exception to the rule, Klipch Corner Horn, uses the wall to increase horn length). If you want to reproduce a 16Hz pipe organ note size does matter, just take a look at a pipe organ.
Sydney Opera House Grand Organ with 64' stops
http://upload.wikimedia.org/wikipedia/en/9/96/Grand_organ.jpg
The 64' Diaphone-Dulzian of the Boardwalk Hall Auditorium Organ.
http://upload.wikimedia.org/wikipedia/en/6/6c/Diaphone-Dulzian.jpg
This thread started out about Front or Down Firing subs.
I prefer front myself. Down firing, firing at the wall, corner loading, Ports & passive radiators are all attempts to increase the loudness of under sized woofers at the sacrifice of sound quality (Exception to the rule, Klipch Corner Horn, uses the wall to increase horn length). If you want to reproduce a 16Hz pipe organ note size does matter, just take a look at a pipe organ.
Sydney Opera House Grand Organ with 64' stops
http://upload.wikimedia.org/wikipedia/en/9/96/Grand_organ.jpg
The 64' Diaphone-Dulzian of the Boardwalk Hall Auditorium Organ.
http://upload.wikimedia.org/wikipedia/en/6/6c/Diaphone-Dulzian.jpg
"This thread started out about Front or Down Firing subs."
Agreed. The starter is rebuilding a JBL PB12 and wants to know whether he should clone or change slightly. At this point I would suggest change to front firing driver, down firing port.
"I prefer front myself. Down firing, firing at the wall, corner loading, Ports & passive radiators are all attempts to increase the loudness of under sized woofers at the sacrifice of sound quality (Exception to the rule, Klipch Corner Horn, uses the wall to increase horn length). If you want to reproduce a 16Hz pipe organ note size does matter, just take a look at a pipe organ."
Again, agreed. The starter is also trying to decide if he should change the volume of the box along with diver orientation. I would suggest he change to "optimum" size.
So my suggestion to him is:
Front fire
Bottom port
Box made for optimum results.
Keep in mind the calss D amp on the sub broke and he replaced it with a PE amp that will not fit in the same location as the original. That is what started the whole box re-engineer process. Now if your going to do a lot of work, you might as well do it RIGHT.
My calculations suggested 2.5 cubes with 3" diameter port 8" long. Tuning of 24 Hz.
Can I get a second opinion on that?
Agreed. The starter is rebuilding a JBL PB12 and wants to know whether he should clone or change slightly. At this point I would suggest change to front firing driver, down firing port.
"I prefer front myself. Down firing, firing at the wall, corner loading, Ports & passive radiators are all attempts to increase the loudness of under sized woofers at the sacrifice of sound quality (Exception to the rule, Klipch Corner Horn, uses the wall to increase horn length). If you want to reproduce a 16Hz pipe organ note size does matter, just take a look at a pipe organ."
Again, agreed. The starter is also trying to decide if he should change the volume of the box along with diver orientation. I would suggest he change to "optimum" size.
So my suggestion to him is:
Front fire
Bottom port
Box made for optimum results.
Keep in mind the calss D amp on the sub broke and he replaced it with a PE amp that will not fit in the same location as the original. That is what started the whole box re-engineer process. Now if your going to do a lot of work, you might as well do it RIGHT.
My calculations suggested 2.5 cubes with 3" diameter port 8" long. Tuning of 24 Hz.
Can I get a second opinion on that?
Unles I missed it , one benefit of downfiring is the elimination of higher frequency content being absorbed more readily into carpet or self cancelation.
One thing that seperates good and great subs is if you can tell where the sub is located. Downfiring seems to at least help in this crucial area. Sometimes a sub needs more help than a lower crossover point & slope won't cure
A great one should blend with the mains and never call attention to itself. There should just be an extension to the main speakers and no more! Totaly transparent
Most systems with subs that you can localize, sound like a phase disconnect or something going on down there.
Regards
David
One thing that seperates good and great subs is if you can tell where the sub is located. Downfiring seems to at least help in this crucial area. Sometimes a sub needs more help than a lower crossover point & slope won't cure
A great one should blend with the mains and never call attention to itself. There should just be an extension to the main speakers and no more! Totaly transparent
Most systems with subs that you can localize, sound like a phase disconnect or something going on down there.
Regards
David
down fired is not good i guess
sorry to intrupt this enclosure conversation
But i think down fired port is no good idea
floor will choke the port, flow of air into port will be distruped, this means effective port dimensions will change... means bad i guess
i think port should be placed such that there is nothing in front of it, my guess is front fires is best
plus sound that comes from port is near to port freq(which is alwayz very small) thus i dont think any carpet on floor can block high frequencies because high freq never come out f port)
now if any 1 thinks down fired acts as a horn and can give u extra db spl, for 50hz horn length is almost 3.5 meters long so dont think there is any horn helping u down there
1 advantage of down fired, it sucks in all the dirt and cleans ur floor n carpet, n dies .......
i am not pro audio geek but can any 1 explain me if my concepts are all false or true
sorry to intrupt this enclosure conversation
But i think down fired port is no good idea
floor will choke the port, flow of air into port will be distruped, this means effective port dimensions will change... means bad i guess
i think port should be placed such that there is nothing in front of it, my guess is front fires is best
plus sound that comes from port is near to port freq(which is alwayz very small) thus i dont think any carpet on floor can block high frequencies because high freq never come out f port)
now if any 1 thinks down fired acts as a horn and can give u extra db spl, for 50hz horn length is almost 3.5 meters long so dont think there is any horn helping u down there
1 advantage of down fired, it sucks in all the dirt and cleans ur floor n carpet, n dies .......
i am not pro audio geek but can any 1 explain me if my concepts are all false or true
Re: down fired is not good i guess
Nothing to do with pseudo horn loading. Here's some clues.
Better room coupling
Hiding leaking mids
No boundary dimension effects due to the small distance to floor
Smoother as only boundary effect is due to close wall
etc etc
Have a look at vented subs from B&W, Proac etc and you'll find some downward ports. I think you will find the majority of commercial subs these days has some coupling with floor by driver or port or PR.
There's plenty of info out there on the subject.
Amit_112dB said:sorry to intrupt this enclosure conversation
But i think down fired port is no good idea
floor will choke the port, flow of air into port will be distruped, this means effective port dimensions will change... means bad i guess
now if any 1 thinks down fired acts as a horn and can give u extra db spl, for 50hz horn length is almost 3.5 meters long so dont think there is any horn helping u down there
i am not pro audio geek but can any 1 explain me if my concepts are all false or true
Nothing to do with pseudo horn loading. Here's some clues.
Better room coupling
Hiding leaking mids
No boundary dimension effects due to the small distance to floor
Smoother as only boundary effect is due to close wall
etc etc
Have a look at vented subs from B&W, Proac etc and you'll find some downward ports. I think you will find the majority of commercial subs these days has some coupling with floor by driver or port or PR.
There's plenty of info out there on the subject.
thanks u all
i think i'll go for down fired port in my comming up exlosure
MAIN REASON- i can have only limited port length if my sub is front fired..... top and Down fired offer an advantage of effective space utilization (as height is normaly kept more than width and depth) and thus i can have bigger port.
The only issue of down firing i suspect now is that it wont be suitable for outdoors use(my roof top beer parties)....for outdoor only front fired is suitable coz u can direct all the energy in single direction...
troystg: i did'nt get you, where can i find down fired drawings ??
i think i'll go for down fired port in my comming up exlosure
MAIN REASON- i can have only limited port length if my sub is front fired..... top and Down fired offer an advantage of effective space utilization (as height is normaly kept more than width and depth) and thus i can have bigger port.
The only issue of down firing i suspect now is that it wont be suitable for outdoors use(my roof top beer parties)....for outdoor only front fired is suitable coz u can direct all the energy in single direction...
troystg: i did'nt get you, where can i find down fired drawings ??
I saw Tee-Bruce's sub enclosure today. Very well constructed and although not perfect it is still light years ahead of the original factory enclosure.
He should be getting some pictures soon. Thing to note is the dampening "wool" that was rubber cemented to all the internal walls. He will be using poly-fill but he had a really neat 3/4 - 1 inch padding that starts out very dense and gradually thins out. I think he used a "rubbery" type of glue so it stays compliant.
He bought 2 of the flared ports from Parts Express so we can experiment with one then when we have it "right" set up the other permanently.
He should be getting some pictures soon. Thing to note is the dampening "wool" that was rubber cemented to all the internal walls. He will be using poly-fill but he had a really neat 3/4 - 1 inch padding that starts out very dense and gradually thins out. I think he used a "rubbery" type of glue so it stays compliant.
He bought 2 of the flared ports from Parts Express so we can experiment with one then when we have it "right" set up the other permanently.
I was thinking along the lines that have been discussed in these posts
Was wanting to use peerless 830500 and matching passive radiator along with a 600 watt “d” class plate amp so am not sure if the discussion was conclusive re port or drone in downward firing position
Have been tinkering with bass box and can only achieve f3 of approximately 28 Hz in a cube shape having 55 litres, would like to be around the 20 Hz mark am I doing something wrong with my calculations
I want to use veneered 32 mm MDF board and have no internal bracing would this be ok with respect to cabinet vibrations, I would fabricate feet to elevate the enclosure of the floor to allow for cone movement but am not sure how high it should be.
I have searched the posts and there is a similar design but in a tower configuration it uses the same components but achieves 19 Hz (both are forward firing)
Some more discussion would be appreciated
Cheers speedie
Was wanting to use peerless 830500 and matching passive radiator along with a 600 watt “d” class plate amp so am not sure if the discussion was conclusive re port or drone in downward firing position
Have been tinkering with bass box and can only achieve f3 of approximately 28 Hz in a cube shape having 55 litres, would like to be around the 20 Hz mark am I doing something wrong with my calculations
I want to use veneered 32 mm MDF board and have no internal bracing would this be ok with respect to cabinet vibrations, I would fabricate feet to elevate the enclosure of the floor to allow for cone movement but am not sure how high it should be.
I have searched the posts and there is a similar design but in a tower configuration it uses the same components but achieves 19 Hz (both are forward firing)
Some more discussion would be appreciated
Cheers speedie
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