The Qts is 0.40 - on the low side and means it has a powerful motor that is not suitable for a MLTL to pull bass tuning below fs. If you can provide me the linear-straight line representation of the MLTL with cross sectional areas in square inches or cm with associated segment length in inches or cm, I can run a model for you. Also, if you can type the TS parameters into this format (for example), it will save me some time too.
Dear XRK,
Thanks for your help in the modelling.
Cross section would be 153cm^2 (l=60cm) followed by woofer and fold, followed by 176cm^2 (l=50cm) ending with a port that is 25cm long (5cm diameter).
Def_Driver 'SB16PFC25-4' | comments after vertical bar here SBA 6in cone mid bass, Qts 0.34, 89.5dB, 40W rms, 5mm xmax
Sd=124cm2
Bl=5Tm
Qms=2.76
Qes=0.39
Mms=13.8g
fs=35Hz
Vas= 32.7mH
Le= 0.56 ohm.
Re=3.2ohm
Many thanks.
Oon
Thanks for your help in the modelling.
Cross section would be 153cm^2 (l=60cm) followed by woofer and fold, followed by 176cm^2 (l=50cm) ending with a port that is 25cm long (5cm diameter).
Def_Driver 'SB16PFC25-4' | comments after vertical bar here SBA 6in cone mid bass, Qts 0.34, 89.5dB, 40W rms, 5mm xmax
Sd=124cm2
Bl=5Tm
Qms=2.76
Qes=0.39
Mms=13.8g
fs=35Hz
Vas= 32.7mH
Le= 0.56 ohm.
Re=3.2ohm
Many thanks.
Oon
Last edited:
Hi All,
I used the MLTL technique to build these towers. The innards are a transplant from my first pair of DIY bookshelf speakers that I wasn't happy with the performance of (too far on CTC caused lobing and sealed didn't really get good bass extension). I used an enclosure calculator on my phone to get the dimensions to something I was happy with, just told it to calculate the other dimensions needed with a 1"x 6" slot port, 6.5" wide baffle, and 36" tall. This gave me a 14" depth with a 5 1/2" long port for a net volume of 55l. Port tuning was set to 35 Hz, and box tuning to 60 Hz, which in theory should give a bit of a saddle between them. Didn't really seem to work out that way, unfortunately, and I think that's mostly down to the fact that the Qts on these drivers is just too high to do really well in MLTLs (0.92). Still, they sound better than they did in the sealed bookshelfs both in terms of bass extension and the lobing that I mentioned earlier, plus the sound quality to time investment ratio is really high. These are stuffed with polyfill somewhere between halfway and two thirds down the line, and driver is placed one third from the top. I don't remember the exact crossover frequency, but it's a second-order Butterworth somewhere in the 2.5k range. Lower than it should be, but the tweeter doesn't sound harsh and I wanted to avoid a pretty serious ~+7 dB hump the woofer has at 3k. Probably didn't work out that way, as the lower treble range is really quite a bit stronger than it should be. No measurements, unfortunately, as I haven't gotten around to buying a calibrated mic yet. I would post the drivers I used, but then you might be tempted to use them, and I wouldn't advise that in a similar build.
EDIT: the importance of bracing can't be understated. I only used 1/2" panels for the sides, and you can absolutely tell where the bracing is and isn't. I plan on gluing another layer to the outside to give it a bit better rigidity.
Here's a couple of pictures:
I used the MLTL technique to build these towers. The innards are a transplant from my first pair of DIY bookshelf speakers that I wasn't happy with the performance of (too far on CTC caused lobing and sealed didn't really get good bass extension). I used an enclosure calculator on my phone to get the dimensions to something I was happy with, just told it to calculate the other dimensions needed with a 1"x 6" slot port, 6.5" wide baffle, and 36" tall. This gave me a 14" depth with a 5 1/2" long port for a net volume of 55l. Port tuning was set to 35 Hz, and box tuning to 60 Hz, which in theory should give a bit of a saddle between them. Didn't really seem to work out that way, unfortunately, and I think that's mostly down to the fact that the Qts on these drivers is just too high to do really well in MLTLs (0.92). Still, they sound better than they did in the sealed bookshelfs both in terms of bass extension and the lobing that I mentioned earlier, plus the sound quality to time investment ratio is really high. These are stuffed with polyfill somewhere between halfway and two thirds down the line, and driver is placed one third from the top. I don't remember the exact crossover frequency, but it's a second-order Butterworth somewhere in the 2.5k range. Lower than it should be, but the tweeter doesn't sound harsh and I wanted to avoid a pretty serious ~+7 dB hump the woofer has at 3k. Probably didn't work out that way, as the lower treble range is really quite a bit stronger than it should be. No measurements, unfortunately, as I haven't gotten around to buying a calibrated mic yet. I would post the drivers I used, but then you might be tempted to use them, and I wouldn't advise that in a similar build.
EDIT: the importance of bracing can't be understated. I only used 1/2" panels for the sides, and you can absolutely tell where the bracing is and isn't. I plan on gluing another layer to the outside to give it a bit better rigidity.
Here's a couple of pictures:
Last edited:
Hi OFH,
Thanks for sharing - I once made very similar tall towers for budget 6.5in $5 woofers from PE (used in their popular sealed bookshelf speakers). The drivers indeed had too high Qts and did not work well here. So it should be stressed that Qts should be in range around 0.45 to maybe 0.65 ideally. Too low Qts is not good either as you won't get bass extension below fs of the driver from the mass loading.
X
Thanks for sharing - I once made very similar tall towers for budget 6.5in $5 woofers from PE (used in their popular sealed bookshelf speakers). The drivers indeed had too high Qts and did not work well here. So it should be stressed that Qts should be in range around 0.45 to maybe 0.65 ideally. Too low Qts is not good either as you won't get bass extension below fs of the driver from the mass loading.
X
I'm designing some desk speakers around the Mark Audio Pluvia 7, which may get occasional other use (or I may build another set of for other locations, depending on how they come out).
I have realised that if I go to the recommended size for a reflex design (11-12 litres) and if I combine that with a cabinet height putting the drivers near ear height I can end up with something quite tall and slim - temptingly close to being a MLTL folded in half. However, to keep the cabinet depth reasonable I end up with a cross section for the constant width line being about 2.8 X SD.
Question is; is that too tight? Should I just revert to a standard BR?
Also; I don't have the wherewithal to model the design before I build it - but in very general terms I have the driver about 30% of the way down the line and the port about 20% from the other end - would that be a reasonable starting point?
Line is 85cm, driver is at 24cm, port is at 68cm.
I have realised that if I go to the recommended size for a reflex design (11-12 litres) and if I combine that with a cabinet height putting the drivers near ear height I can end up with something quite tall and slim - temptingly close to being a MLTL folded in half. However, to keep the cabinet depth reasonable I end up with a cross section for the constant width line being about 2.8 X SD.
Question is; is that too tight? Should I just revert to a standard BR?
Also; I don't have the wherewithal to model the design before I build it - but in very general terms I have the driver about 30% of the way down the line and the port about 20% from the other end - would that be a reasonable starting point?
Line is 85cm, driver is at 24cm, port is at 68cm.
That's great news, thanks for the tips. Earlier in this thread I got some great advice when I was trying to figure out a MLTL bass section - as is often the case daily life got in the way of me finishing that design, but these desk speakers are going to be quite simple and inexpensive to build - and hopefully they will be quite flexible. That's the idea anyway.
I don't quite understand how the BR volume relates to that of the MLTL, for smaller drivers at least. For example WinISD suggests a 6 litre cabinet for the TB W3-871 at 75 Hz, yet that of the TABAQ is more like 10 litres and 55 Hz. Such a small volume makes it infeasible to have a CSA that isn't narrower than the driver itself, for any kind of TL length.
If you tune the BR for 55Hz (and this only works with Qts > 0.42 or so) you will find that it can tune lower than fs. Volume usually increases to make box frequency go down. Once you have volume, set the baffle width, and set the TL length, typically no shorter than 30in to 32in. Solve for depth to make volume work out.
Hi X and others
I am looking at designing an MLtL for Monacor sph 176 MiD WOOFERS I came up with a an 85cm line with a cross section of 270cm with a 5cm wide by 11cm long port giving 23 litres tuned to 42 hz , am on the right track here? Thanks in advance for any advise.
Simon
TECHNICAL DATA:
Impedance (Z) 8 Ω
Resonant frequency (fs) 39 Hz
Max. frequency range f3-4,500 Hz
Music power 120 WMAX
Power rating (P) 70 WRMS
SPL (1 W/m) 90 dB
Suspension compl. (Cms) 1.01 mm/N
Moving mass (Mms) 14 g
Mech. Q factor (Qms) 2.27
Electr. Q factor (Qes) 0.44
Total Q factor (Qts) 0.37
Equivalent volume (Vas) 27 l
DC resistance (Re) 6.6 Ω
Force factor (BxL) 7.7 Tm
Voice coil induct. (Le) 0.75 mH
Voice coil diameter 25 mm
Voice coil former aluminium
Linear excursion (XMAX) ±5.5 mm
Eff. cone area (Sd) 140 cm2
Magnet weight 450 g
Weight 1.25 kg
I am looking at designing an MLtL for Monacor sph 176 MiD WOOFERS I came up with a an 85cm line with a cross section of 270cm with a 5cm wide by 11cm long port giving 23 litres tuned to 42 hz , am on the right track here? Thanks in advance for any advise.
Simon
TECHNICAL DATA:
Impedance (Z) 8 Ω
Resonant frequency (fs) 39 Hz
Max. frequency range f3-4,500 Hz
Music power 120 WMAX
Power rating (P) 70 WRMS
SPL (1 W/m) 90 dB
Suspension compl. (Cms) 1.01 mm/N
Moving mass (Mms) 14 g
Mech. Q factor (Qms) 2.27
Electr. Q factor (Qes) 0.44
Total Q factor (Qts) 0.37
Equivalent volume (Vas) 27 l
DC resistance (Re) 6.6 Ω
Force factor (BxL) 7.7 Tm
Voice coil induct. (Le) 0.75 mH
Voice coil diameter 25 mm
Voice coil former aluminium
Linear excursion (XMAX) ±5.5 mm
Eff. cone area (Sd) 140 cm2
Magnet weight 450 g
Weight 1.25 kg
Greets!
Assuming you mean a 5 cm diameter port and an unspoken 0.349 driver offset, then looks fine in Hornresp with minimal stuffing except that at a peak usable 40 W the vent mach will be over twice the considered acceptable limit [~12.6% Vs ~5%]. To get to ~5% requires a 3"/7.62 cm diameter x 11"/28 cm.
BTW, it's OK to just post the driver specs' link
: https://www.monacor.com/products/co...nology/hi-fi-midrange-speakers/sph-176/?r=pdf
GM
Assuming you mean a 5 cm diameter port and an unspoken 0.349 driver offset, then looks fine in Hornresp with minimal stuffing except that at a peak usable 40 W the vent mach will be over twice the considered acceptable limit [~12.6% Vs ~5%]. To get to ~5% requires a 3"/7.62 cm diameter x 11"/28 cm.
BTW, it's OK to just post the driver specs' link
: https://www.monacor.com/products/co...nology/hi-fi-midrange-speakers/sph-176/?r=pdfGM
Hi GM
TABAQ has a relatively large volume for a 3 inch driver and is well stuffed.
My current TABAQ is with Peerlees 830987 which is not even 3 inch. The bass is amazing but the SPL is of
course limited. For normal listening level it works fine.
For a 4 inch driver the volume should be increased. For the time being I am - again - looking at the design for a 4 inch version.
I see stuffing as an important design parameter in TL / WQ. To keep the desired bass output I increase the volume.
Bjørn
TABAQ has a relatively large volume for a 3 inch driver and is well stuffed.
My current TABAQ is with Peerlees 830987 which is not even 3 inch. The bass is amazing but the SPL is of
course limited. For normal listening level it works fine.
For a 4 inch driver the volume should be increased. For the time being I am - again - looking at the design for a 4 inch version.
I see stuffing as an important design parameter in TL / WQ. To keep the desired bass output I increase the volume.
Bjørn
Greets!
OK, so highly damped it is, which allows smaller than predicted vents.
Agreed, we are on the same [design] 'page' with the caveat that damping doesn't take away too much box efficiency.
Where I can't seem to relate to though is claims of 'bass is amazing but the SPL is of course limited. For normal listening level it works fine.'
I mean I've built quite a few speakers using tiny round and ovals out of small radios, TVs, etc., and no how, no way would I make such claims for them.
Decent mid-bass/lower mids, yes, due to being high Q, hence well suited to damped [ML] TLs; SPL OK for highly compressed AM/FM, TV BW limited signals at typical TV viewing levels since obviously it's what they were designed for, but small HIFI except computer monitors well within 1 m, no, or at least not without some form of signal compression, which isn't HIFI to me.
Regardless, whatever works for the end user and seems like plenty of folks like the TABAQ and that's all that really counts, so congrats on such a successful design.
GM
OK, so highly damped it is, which allows smaller than predicted vents.
Agreed, we are on the same [design] 'page' with the caveat that damping doesn't take away too much box efficiency.
Where I can't seem to relate to though is claims of 'bass is amazing but the SPL is of course limited. For normal listening level it works fine.'
I mean I've built quite a few speakers using tiny round and ovals out of small radios, TVs, etc., and no how, no way would I make such claims for them.
Decent mid-bass/lower mids, yes, due to being high Q, hence well suited to damped [ML] TLs; SPL OK for highly compressed AM/FM, TV BW limited signals at typical TV viewing levels since obviously it's what they were designed for, but small HIFI except computer monitors well within 1 m, no, or at least not without some form of signal compression, which isn't HIFI to me.
Regardless, whatever works for the end user and seems like plenty of folks like the TABAQ and that's all that really counts, so congrats on such a successful design.
GM