Hello all:
I have a few MCM 55-1205's* kicking around and want to experiment a bit. Some are currently in .3 cu ft sealed boxes which actually sound better than they should. I want to see if they are candidates for TL duty. The first kicker is I want to use a 2.5 TMM configuration in leiu of BSC, rolling the second one off around 600~ Hz instead of burning 3-6 dB up in a resistor.
Second is I want to see if it is practical to use a tall/ slim straight / folded TL to get what low end there is.
I also found out I'm a few days late to get Martin King's mathcad files, so I am trying to bend my non-calculus brain around the still available charts. I also found a couple of calculators to try modeling some configurations instead of trial & error. Paper is cheaper than sawdust.
What I have been exploring are iterations on the Weems Pipe, but with updated math for the TLL with the SL>SO. One spreadsheet wants something like a BIB line, the other looks more reasonable but I'll have to translate some German terms... Looking for some more (non-calculus) solutions, or a line on the currently unavailable MJK mathcad files.
Thanks in advance for your feedback, pointers, and suggestions
.
* Here is the driver sheet: www.newark.com/mcm-audio-select/55-1205/5-1-4-poly-treated-cone-woofer/dp/36C6658
Fs=65Hz, Qts~.77, Vas=.388ft2.
I have a few MCM 55-1205's* kicking around and want to experiment a bit. Some are currently in .3 cu ft sealed boxes which actually sound better than they should. I want to see if they are candidates for TL duty. The first kicker is I want to use a 2.5 TMM configuration in leiu of BSC, rolling the second one off around 600~ Hz instead of burning 3-6 dB up in a resistor.
Second is I want to see if it is practical to use a tall/ slim straight / folded TL to get what low end there is.
I also found out I'm a few days late to get Martin King's mathcad files, so I am trying to bend my non-calculus brain around the still available charts. I also found a couple of calculators to try modeling some configurations instead of trial & error. Paper is cheaper than sawdust.
What I have been exploring are iterations on the Weems Pipe, but with updated math for the TLL with the SL>SO. One spreadsheet wants something like a BIB line, the other looks more reasonable but I'll have to translate some German terms... Looking for some more (non-calculus) solutions, or a line on the currently unavailable MJK mathcad files.
Thanks in advance for your feedback, pointers, and suggestions
.* Here is the driver sheet: www.newark.com/mcm-audio-select/55-1205/5-1-4-poly-treated-cone-woofer/dp/36C6658
Fs=65Hz, Qts~.77, Vas=.388ft2.
Hi,
Build a larger vented box, you can simulate and optimize to a reasonably good loading and then plug the port if needed. Corner loading can further help to decide what sounds better. Try to measure the TSP yourself to further reinforce your confidence in doing the right thing.
p.s. your link appears to be damaged, an excess of letters just before www.
Build a larger vented box, you can simulate and optimize to a reasonably good loading and then plug the port if needed. Corner loading can further help to decide what sounds better. Try to measure the TSP yourself to further reinforce your confidence in doing the right thing.
p.s. your link appears to be damaged, an excess of letters just before www.
Yep and within the range of 0.35 to 0.45 (and sometimes up to 0.50 or so). The OP's choice of this quite high-Qts driver will result in a really ugly-looking response in a TL.
Paul
Paul
Thanks for the responses Gentlemen, I have looked at the plots for sealed & reflex boxes, and the driver dosen't seem to gain much unless I go over 2 cubic feet for a 5.25" driver. Even then, I have to push the tuning down into the 40's to level out the hump. (will post when iPad starts talking to desktop). Sealed .8 cu.ft. -1.5 look OK.
I know that .4 Qts is a good ballpark for reflex enclosures because the Vas ~optimal cabinet volume, but I was under the impression that higher Q drivers were 'happier' in TL's.
Does anyone have a line on martin King's "Lost files"?
Will post some graphics when the desktop is more obedient.
Mucho Gracias!
I know that .4 Qts is a good ballpark for reflex enclosures because the Vas ~optimal cabinet volume, but I was under the impression that higher Q drivers were 'happier' in TL's.
Does anyone have a line on martin King's "Lost files"?
Will post some graphics when the desktop is more obedient.
Mucho Gracias!
Greets!
As already noted, inverse tapered TQWT are best suited to lower Qts' systems same as for BR alignments. Beyond ~0.312 Qts' to ~0.54 Qts' is better suited to constant [straight] tapered pipes with expanding TQWT [ pipe horn] up to the practical limit where the mass corner has dropped to Fs [Fs/Qts' = Fs].
The Weems Pipe is a vent terminated [mass loaded] pipe horn aka ML-TQWT in MJK 'speak' and I choose to call a ML-horn to differentiate it from his inverse tapered ML-TQWT.
Adding 0.5 ohms for wiring/whatever brings the Qts up to a ~0.811 Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
I'll post some Hornresp straight pipe, pipe horn sims as time permits.
GM
As already noted, inverse tapered TQWT are best suited to lower Qts' systems same as for BR alignments. Beyond ~0.312 Qts' to ~0.54 Qts' is better suited to constant [straight] tapered pipes with expanding TQWT [ pipe horn] up to the practical limit where the mass corner has dropped to Fs [Fs/Qts' = Fs].
The Weems Pipe is a vent terminated [mass loaded] pipe horn aka ML-TQWT in MJK 'speak' and I choose to call a ML-horn to differentiate it from his inverse tapered ML-TQWT.
Adding 0.5 ohms for wiring/whatever brings the Qts up to a ~0.811 Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
I'll post some Hornresp straight pipe, pipe horn sims as time permits.
GM
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Hi GM: The files I was referring to are Martin J.King's worksheets. I contacted Martin and found that they are no longer available.
"Hi Frank,
Unfortunately I stopped new user access to the MathCad worksheets at the end of 2018. I suggest looking into HornResp or Leonard Audio's TL program, both are available on the DIYaudio forum.
Sorry,
Martin"
Since those are no longer an option, is there a good copy of the Leonard Audio TL program available? I'm reading up on HornResp which looks to have a bit of a learning curve to become proficient.
I did try using Keith Webb's spreadsheet from MJK's Quarter-wave site, and the size is a bit big for 5.25" drivers. It does appear that Bl & Qt do have more of an affect than I would have supposed.
What effect does reducing (or porting the open end of the line (I see it is now called "mass-loading")? Seems like it would diminish the loading & efficiency.
Thanks,
Frank
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Ah! Didn't know that, bummer!
My LATL was working fine when it went down, but recently it crashed, so tried the workaround written up on the official thread to reload it and when I opened it I still get a .NET error that I've no clue how to deal with, leaving me with HR since I don't have MathCad loaded. It all started here: Transmission Line Modelling Software
T/S is all about 'trimming the fat' off cab size, so MJK's program is as lean as it gets without starting to sacrifice low end acoustic efficiency. Not many 'free lunches' in audio design.
TLs are generally too long for mass loading [venting], so keep the net Vb and shorten the length to the ~42-60" range and add a vent to make a MLTL.
GM
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Hi GM: I have given up on the Leonard TL thing, and MJK's mathcad papers are now unobtanium. So, I am fiddling around with Hornresp and learning how it works... I have been spending what spare time I have developing some competency with it.
I have been trying the workaround of modeling the drivers in a conventional bass reflex box and using the derived box volume (and port area) as a jumping off point for Hornresp volumes. It seems that the drivers in question (Fs=65Hz, Qts~.77, Vas=11L.) may work OK in a Metronome style ML-QQT application. One question among many I have, is whether the Metronome models more closely as Conical, or a Parabolic in Hornresp.
Another is whether since I am planning on using a TMM (2.5) configuration for baffle step and rolling off everything above the BSC point- is it necessary to have the drivers back to back?
Thanks in advance,
Frank
I have been trying the workaround of modeling the drivers in a conventional bass reflex box and using the derived box volume (and port area) as a jumping off point for Hornresp volumes. It seems that the drivers in question (Fs=65Hz, Qts~.77, Vas=11L.) may work OK in a Metronome style ML-QQT application. One question among many I have, is whether the Metronome models more closely as Conical, or a Parabolic in Hornresp.
Another is whether since I am planning on using a TMM (2.5) configuration for baffle step and rolling off everything above the BSC point- is it necessary to have the drivers back to back?
Thanks in advance,
Frank
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