The MLTL alignment is my preference at the moment. You give up a bit in terms of overall output, but midbass transition is better and out of band noise is much less of an issue. And for home use, you could possibly get away with a smaller vent.
However, whether or not it's a good match for your speaker is another matter. What do the layout and the sim look like?
You'll need to keep the cross-sectional area and the length the same as the total cross-sectional area and length of those vents.
I think you might find that this results in slot vents that are pretty narrow. You could flare each end of the vent to compensate, but it might be difficult to model the flaring in Hornresp to determine what the final response might be like.
BTW, getting down to 32 Hz with a pro audio 12 in a small box designed for pro audio use? That's pretty decent results.
Down to 32 Hz is a great result that’s why I endorse this design! And I will be building more but I would like to try slot ports. I thought it was not a simple area conversion, I thought slots have more surface area to resist the air movement. No?
hello noviygera,
You can find in the link below some loudspeakers with slot solutions available to support you in the design process. Very easy to use.
https://freeloudspeakerplan.rf.gd/
You can find in the link below some loudspeakers with slot solutions available to support you in the design process. Very easy to use.
https://freeloudspeakerplan.rf.gd/
Thanks Brian for your advice/meaning
I calculated with your BOXplan MLTL Vers 2.8 spreadsheet a little to find out what the MLTL results with 12LW1400 can be expected.
But first:
- The BP6 housing from Eighteensound outside size seem to be 67x40x40cm size - I will keep the same size with the MLTL calculations/sim for comparison assuming 15mm thick wood (81.9liter/net, 107.2liter/gross)
- the total port size with the BP6 box is 4x100mm diameter round ports - I doubt that can be directly taken as the port size for the MLTL for same tuning frequency. Instead I play with the spreadsheets by playing with various sizes between 1/2 Sd to 1/4 Sd and check the tuning and velocities, Hornresp will calculate.
1/2 Sd = 260mm2 port size MLTL with 12LW1400, I get this:
The lowest peak of the 260mm2 port is incredible low at about 33Hz.... although the size is already half of Sd - usually a good size especially if not used for very rough PA use, but home music bass speaker cabinet.
When running 30V at the speaker, I can expect around just around 115db at a displacement of 8mm at that frequency of 33Hz - it needs steep HF filtering to keep the displacement save at this levels - not problem, as I run long 64k/128k FIR-filtered processing and as it is only music any latency of the HP is no problem...
Mouth Velocity at that 30V level (which needs about 200W amp) indeed reaches critical level of 18m/sec.... however I rather would prefer a lower tuning, as the speaker will not be driven very often at that level at home.
Indeed, the mid bass performance seem to much better, than an usual BR housing, as port resonance is much lower - perhaps it can be even more reduced, with optimum speaker placement on the baffle as well as some stuffing - to give up a db or so of efficiency in home use is not a problem...
I wonder, if this design can be even used as a 2 way speaker at home, when I introduce the mid/high frequency horn at 650Hz...
This is my analysis so far for pure comparison, keeping the same outside dimension as the Eighteensound BP6 suggestion.
Next I will play around with some different box size/dimensions, to find out if a different proportion of depth/width/height of the housing could be even more beneficial for the MLTL design.... That will be part of my next post here...
My driver just arrived, still waiting on the plate amp. My thoughts are to go with a box with dimensions close to the 18 sound design but with slot ports that match the area of the tube ports. Wondering on the best placement for them though - in the small front chamber in particular if they are central, is that going to create any odd resonances, the volume behind the slot would look almost like a stub or would they be better right at each end of the box?
Decided to stick with the 18 Sound design pretty closely but with added bracing and plate amp.
https://a360.co/3HaeV6C
https://a360.co/3HaeV6C
Finally finished off the build (except last bit of painting) and ran a first test. The Powersoft litemod-4hc plate amp runs the sub in bridge on 2 channels and the other two channels can run one satellite (B&C 8FCX51) each - I replaced the speakon power out with a speakon NL4 out.
Definitely rolls off higher than the 18 Sound application note. I did add a fraction extra volume to the box to account for the plate amp and extra bracing so in terms of dead volume it should be about the same. There is a fair bit of padding on the walls not sure if that would have a significant affect.
Definitely rolls off higher than the 18 Sound application note. I did add a fraction extra volume to the box to account for the plate amp and extra bracing so in terms of dead volume it should be about the same. There is a fair bit of padding on the walls not sure if that would have a significant affect.
Yeah, that's what I'd expect from a 12" pro audio driver in a 6th order BP alignment of that size. Are you able to do a measurement of its impedance response curve?
Looks like a pretty decent passband, and a rolloff just below 50 Hz is actually Ok for most pro audio uses. Aiming for more output at low frequencies from a 12" driver usually results in less SPL capability in the passband because of increased excursion requirements (and I'm saying this as I'm getting a 40 Hz Offset TL with a 12" driver being built for me, sigh).
Looks like a pretty decent passband, and a rolloff just below 50 Hz is actually Ok for most pro audio uses. Aiming for more output at low frequencies from a 12" driver usually results in less SPL capability in the passband because of increased excursion requirements (and I'm saying this as I'm getting a 40 Hz Offset TL with a 12" driver being built for me, sigh).
I'm a bit green on measurements. What's the best way to measure impedance. My powersoft T series amps have a live impedance output, but i don't think the litemod does.
The easiest, but likely the most expensive, way to take an impedance curve of your build is with a DATS, available from Parts Express. Cheaper would be to build your own impedance-measuring jig and use REW (free PC software) to perform the measurement.
Usually when I do a build, the first thing I do is measure the impedance curve. Not only does it quickly confirm if my build is a good match for the sim, it also lets me know if there are any issues with the build (leaks and panel flex will impact the impedance curve).
Usually when I do a build, the first thing I do is measure the impedance curve. Not only does it quickly confirm if my build is a good match for the sim, it also lets me know if there are any issues with the build (leaks and panel flex will impact the impedance curve).