A MLTL is a transmission line. Bass reflex is only bass reflex if the enclosure is golden ratio. If you increase the length of a TL (MLTL) beyond optimally flat, it will tune the enclosure lower, with a drooping response. The driver is still damped due to the mass loading (port) is set to Fs of the driver.
Sometimes this can be advantagous if we have enough room gain from placement, eg, floor loading, corner loading etc. to make up for the extreme low end loss.
What is interesting is modeling a typical (non GR) BR design with TL software.
Sometimes this can be advantagous if we have enough room gain from placement, eg, floor loading, corner loading etc. to make up for the extreme low end loss.
What is interesting is modeling a typical (non GR) BR design with TL software.
I tuned the cabinet as high as i could with just the hole in the back of the cabinet. The second impedance peak around 55 hz, would have expected higher freq for a port tuned to 45hz.
Experimented increasing the port length - increasing the length to around 4" long which in theory should have dropped the port freq to around 35hz, dropped the second impedance peak to 48hz. To me (as GM suggests) a leaky cabinet.
Removed the extended port. Tuned with stuffing - I ended up added stuffing from the end of the line to just under the driver, and draping a blanket of BAF over the central divider.
The freq response similar to those i have posted previously. The big suck out around 50hz due to the room response(?) ( i do need to understand how to deal with this - next challenge?)
Carried out some subjective listening - for the last hour or so, only one bass cabinet so not HI-FI. The bottom end is there - subtle though - dry. Something seems to be lacking - the attack of the kick drum etc - something which the Onkens did well seems to be missing. As my wife says- not alot of presence for a very big box!! - sums it up well.
Not sure where to go next with this. As with everything in life its a compromise, i could build a front loaded bass horn and get the slam and attack that will integrate well with the JBL 2482's - but nothing below 60 hz.
Experimented increasing the port length - increasing the length to around 4" long which in theory should have dropped the port freq to around 35hz, dropped the second impedance peak to 48hz. To me (as GM suggests) a leaky cabinet.
Removed the extended port. Tuned with stuffing - I ended up added stuffing from the end of the line to just under the driver, and draping a blanket of BAF over the central divider.
The freq response similar to those i have posted previously. The big suck out around 50hz due to the room response(?) ( i do need to understand how to deal with this - next challenge?)
Carried out some subjective listening - for the last hour or so, only one bass cabinet so not HI-FI. The bottom end is there - subtle though - dry. Something seems to be lacking - the attack of the kick drum etc - something which the Onkens did well seems to be missing. As my wife says- not alot of presence for a very big box!! - sums it up well.
Not sure where to go next with this. As with everything in life its a compromise, i could build a front loaded bass horn and get the slam and attack that will integrate well with the JBL 2482's - but nothing below 60 hz.
More listening with the MLTL bass - added the LF channels together, this seemed to give a more whole sound. ( did not realise that so many recordings have stereo right at the bottom end) This has convienced me to build another test cabinet to hone out some issues i have.
I have been modelling the room acoustic to "sort" the 50Hz suck out. I had my test cabinet into the room by 2 ft to allow the rear port to "breathe" The room response spread sheet would suggest that the response would be smoother if i push them back to the wall ( maybe closer to the corner).
How do get the port onto the front, without adding lots of folds which i think will introduce more problems than it solves. I was wondering about having a double vertical fold so you would have vents at the sides, Onken meets TL.
Suggestions please.
I have been modelling the room acoustic to "sort" the 50Hz suck out. I had my test cabinet into the room by 2 ft to allow the rear port to "breathe" The room response spread sheet would suggest that the response would be smoother if i push them back to the wall ( maybe closer to the corner).
How do get the port onto the front, without adding lots of folds which i think will introduce more problems than it solves. I was wondering about having a double vertical fold so you would have vents at the sides, Onken meets TL.
Suggestions please.
I have thinking what is the best way to integrate MLTL's into my room. The layout is as follows
I have tried the room the otherway around and its alot worse! My throught are maybe i could push the MLTL's into the corner, and front vent them maybe. The other throught i have had is to use vertical space, as you get alot more space for a given foot print. Having heard some top venting speakers a number of years back i throught about the following. I would use the cabinet to attach the horns to. Don't think i could get away with a parallel line so maybe a 2:1 taper. Did to sim to bad, obviously if tapered it needs to be around 6 ft to get the same Vb as a rectangular cabinet.
Anybody done anything similar or has any experience which would suggets corner loading would be bad.
I have tried the room the otherway around and its alot worse! My throught are maybe i could push the MLTL's into the corner, and front vent them maybe. The other throught i have had is to use vertical space, as you get alot more space for a given foot print. Having heard some top venting speakers a number of years back i throught about the following. I would use the cabinet to attach the horns to. Don't think i could get away with a parallel line so maybe a 2:1 taper. Did to sim to bad, obviously if tapered it needs to be around 6 ft to get the same Vb as a rectangular cabinet.
Anybody done anything similar or has any experience which would suggets corner loading would be bad.
Not delivering there true potential - i think is a better way of describing the situation! I believe that the rooms contribution is not helping the situation currently, and wish to work with the room than against it. I am looking at the different options of where to port the line, front, back into the ceiling or into the floor. I understand that venting towards the ceiling can make the bass less muddy in some cases (even though its not muddy currently).
The second point was is there a better arrangement of the speaker system that having a bass cabinet and just "plonking" the horns on top of it. Thats why i was thinking of a columnal structure to attach the other drivers too. It will also allow the MLTL to have a longer line potentially which cannot be a bad think (?)
The second point was is there a better arrangement of the speaker system that having a bass cabinet and just "plonking" the horns on top of it. Thats why i was thinking of a columnal structure to attach the other drivers too. It will also allow the MLTL to have a longer line potentially which cannot be a bad think (?)
More thinking (no building!!!)
I know that wave guides allow a speaker to be placed closer to room boundaries, so i was wondering whether a front loaded horn (wave guide) could be combined with the MLTL. I have sketched something up.
By dividing the volume differently it allows me to have 2 folds allowing a longer line for a given height. The only problem i see is the exit of the line splits - so i would be have to have two ports venting out the front.
Will this be a problem ? I have throught i could rejoin the lines if necessary to have a single port.
Is this a stupid idea, i am hoping as its similar to the altec a5/a7 thats it not!!
I know that wave guides allow a speaker to be placed closer to room boundaries, so i was wondering whether a front loaded horn (wave guide) could be combined with the MLTL. I have sketched something up.
An externally hosted image should be here but it was not working when we last tested it.
By dividing the volume differently it allows me to have 2 folds allowing a longer line for a given height. The only problem i see is the exit of the line splits - so i would be have to have two ports venting out the front.
Will this be a problem ? I have throught i could rejoin the lines if necessary to have a single port.
Is this a stupid idea, i am hoping as its similar to the altec a5/a7 thats it not!!
I have a second pair drivers Altec 414 16B's i have been comparing against my existing 414Z's. I have put them in the test MLTL cabinet and measured near and pair field, and they don't seem to be that dis-similar, traces within a couple of db's.
How close do a pair of drivers need to be to each other to use them in a duplex arrangement, and should i pay more attention to installed response or T/S measurements?
I assume if i used a pair in a MLTL i would just double the volume. Obviously both drivers would not be at the same position in the transmission line, - so how do you model it in MJK's work sheets.
I current thoughts are something similar to this but around 2/3's the size.
Smaller cabinet assumed as Vas for a 414 is around 2/3's that of a 515b's but instead of an Onken loading would fold the line for MLTL. The vane guide (front horn) would allow me to time align easier with my midrange horns
How close do a pair of drivers need to be to each other to use them in a duplex arrangement, and should i pay more attention to installed response or T/S measurements?
I assume if i used a pair in a MLTL i would just double the volume. Obviously both drivers would not be at the same position in the transmission line, - so how do you model it in MJK's work sheets.
I current thoughts are something similar to this but around 2/3's the size.
Smaller cabinet assumed as Vas for a 414 is around 2/3's that of a 515b's but instead of an Onken loading would fold the line for MLTL. The vane guide (front horn) would allow me to time align easier with my midrange horns
Looks like i will be going back to only one driver per cabinet - one of the 414b's is defective - it is rubbing and it feels really stiff. The guy hwo sold me the drivers has been very appologetic, looks like may be able to claim on postal insurance. He has offered a couple of recone kits at a very good price - i am just clarifying whether these are GPA ones or generics. My current opinion is that a recone is never going to come close to my existing 414z's and would have to recone all 4 if i was going to get anywhere near matched.
??? 414B with, without magnet pot, though the frame is the same, so wondering what ya'll have.
GM
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Probably right, though tuning each pair individually and using EQ to match L/R channel levels can make mismatched pairs work well together.
GM
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