I want to start a project, a floor stander with SB13PFC25-4 COAX and I need some suggestions for subwoofer and some opinions whether it is worthwhile or not.
Thank you!
Thank you!
Sounds like a good idea to me 🙂
The coax in a 10-15Litre sealed box with a 2nd order Butterworth electrical highpass at 75Hz should achieve approximately 4th order Linkwitz-Riley acoustic highpass at 100Hz. This gives 50Watts power handling before xmax is exceeded at 105dB SPL - more than enough for most home listening environments.
A sub can then be used with a 100Hz 4th order lowpass. The choice of sub is really dependant on your physical size requirements, budget and how low in frequency you want it to go. Just about any sub 8-12" will be happy to cross at 100Hz.
At 100Hz if using passive crossovers the components will be big and therefore a bit pricey (particularly inductors) but it is the most logical place to cross since the coax's mechanical resonance/rolloff is used as part of the crossover slope. If using an active crossover then it's no issue. You could cross a bit higher, perhaps up to around 300Hz if using one sub in each floor stander to create a 3-way system. This may make the crossover components cheaper but it will be more difficult to design because the mechanical resonance of the coax becomes a hindrance rather than helping.
The coax in a 10-15Litre sealed box with a 2nd order Butterworth electrical highpass at 75Hz should achieve approximately 4th order Linkwitz-Riley acoustic highpass at 100Hz. This gives 50Watts power handling before xmax is exceeded at 105dB SPL - more than enough for most home listening environments.
A sub can then be used with a 100Hz 4th order lowpass. The choice of sub is really dependant on your physical size requirements, budget and how low in frequency you want it to go. Just about any sub 8-12" will be happy to cross at 100Hz.
At 100Hz if using passive crossovers the components will be big and therefore a bit pricey (particularly inductors) but it is the most logical place to cross since the coax's mechanical resonance/rolloff is used as part of the crossover slope. If using an active crossover then it's no issue. You could cross a bit higher, perhaps up to around 300Hz if using one sub in each floor stander to create a 3-way system. This may make the crossover components cheaper but it will be more difficult to design because the mechanical resonance of the coax becomes a hindrance rather than helping.
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I would like recommend shallower xo to subwoofer, more punch with less group delay. Easy to test with minidsp. Eh. LR2 at 180hz should not stress mid too much.
Problem is that you get about a BW2 acoustic highpass for free from the driver/box, so to achieve 180Hz LR2 you effectively need a notch filter giving no attenuation below 50Hz or so because by then the woofer is already on a 2nd order slope. That is rather demanding on the woofer.
Either that or you have a slope that hits LR2 from 180Hz down to about 70Hz and then steepens to 4th order. Phase tracking with the sub will be suboptimal. If you move the XO up to about 300Hz the fact that it steepens 2 orders at 70hz becomes less of an issue.
edit: actually putting a 1st order electrical highpass at 200Hz is close enough to 180Hz LR4 and could work nicely. Excursion is about twice that of 100Hz LR4 acoustical below about 40Hz, but still acceptable.
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I haven't learnt to design passive xo circuits! Tuu easy to live with dsps...
This is SB13coax in IEC baffle, cone has resonance at 43Hz, pretty low!
This is SB13coax in IEC baffle, cone has resonance at 43Hz, pretty low!
Transfer functions (all in 12L sealed boxes)
Yellow - unfiltered
Green - 90Hz BW2 electrical to achieve 100Hz LR4 acoustical
Orange - 200Hz BW1 electrical to achieve 180Hz LR2 acoustical
Excursion at 50Watts:
Both are quite viable and easy to implement via DSP. For passive XO you can probably fudge the 2nd order filter's Q (lower it) to account for the impedance peak of the woofer.
A 1st order passive highpass will require an LCR conjugate impedance flattening network to make the highpass behave.
Yellow - unfiltered
Green - 90Hz BW2 electrical to achieve 100Hz LR4 acoustical
Orange - 200Hz BW1 electrical to achieve 180Hz LR2 acoustical
Excursion at 50Watts:
Both are quite viable and easy to implement via DSP. For passive XO you can probably fudge the 2nd order filter's Q (lower it) to account for the impedance peak of the woofer.
A 1st order passive highpass will require an LCR conjugate impedance flattening network to make the highpass behave.
That's because of the gain from ~1-6khz provided by the woofer cone acting as a horn/waveguide. The rough response above 8kHz is also fairly typical of a dome tweeter in a waveguide. Once you factor in baffle step compensation of the woofer and shaping the lower part of the tweeters response down to flat, you should achieve a flat-ish response about 86dB/1m or so.
Does anyone know if the tweeter is in the same plane as the origin of the cone or is placed behind the magnet?
I'd prefer to see a woofer used rather than a sub.... Unless the main intended program material is loud movies. A pair of DA175 (side firing?) in a tower with the coax sausage/log enclosure on the top could be done in 72 litres with the port tuned to somewhere around 30Hz. That setup would comfortably play up through 500Hz and avoid playing any bass through the coax driver.
Being addicted to the Edge (yes, I do have a problem with Edge) I just can't help publishing a typical baffle diffraction effects, the remedy of which is known in the circles as BSC... but coud be just helpful in this case. Actually any midrange-woofer xo in a 3-4-way speaker should incorporate this! Actually setting xo around 3-400hz is very easy for any subwoog´fer driver. Ready-made plate amplifiers can't do that , but we have those neat little dsp boxes!
The cone is very deep!
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Sound nice but:
I prefer 10 inches if possible
I like projects with side woofer but from experience I know that if you cut it above 120hz-150hz does not sound good. I do not have experience with two side woofers, maybe it can be cut higher.
In Romania the price for DA175 is huge, is more than two time more that on parts-express
if you cut it below 250hz I also need a mid-woofer for the lower mid's
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It is so much easier to get a blend between mid and woofer in the 250-400 Hz range. This also keeps the weight of the lower mids intact, while stressing the midrange less. It depends on how large the woofer is as to where the blend is best, as well as how close it is to the floor.
Later,
Wolf
Later,
Wolf
For a side woofer blending mid and woofer in the 250-400 Hz range will not work.
With woofer in front I'm with you with this frequency range of crossover.
With woofer in front I'm with you with this frequency range of crossover.
I built a compact floorstander using a side firing 10" woofer, the SB13PFC25-04 which is similar to the coaxials and the SB26STCN tweeter (very nice unit by the way). It was liked enough to built a total of 11 pairs but...
If you do a side firing design and use a cutoff above 150Hz (i used 95Hz on these, will post some info later and will give you the plans if you want) you will hear a separate sound source from the side woofer. In the one I did it was put in 2l sealed enclosure and the SB13 was bottoming out at around 35W. It looks nice on spec but is a weak unit so you better get two. And the frame is really annoying - you need a CNC router to cut it off and it will cost the premium to the SB15NRX/MFC which are better. You can buy a cheap and very decent woofer (W.25.200.8.MC - Nagłośnienie STX) from a Polish company called STX. Specs are within 5%, well were on the several pairs I had.
The Monacor SPM-205/8 can also do well - its a nice unit for the money and can be used in classic TL designs, also cheap and easy to acquire in Europe. 🙂
If you do a side firing design and use a cutoff above 150Hz (i used 95Hz on these, will post some info later and will give you the plans if you want) you will hear a separate sound source from the side woofer. In the one I did it was put in 2l sealed enclosure and the SB13 was bottoming out at around 35W. It looks nice on spec but is a weak unit so you better get two. And the frame is really annoying - you need a CNC router to cut it off and it will cost the premium to the SB15NRX/MFC which are better. You can buy a cheap and very decent woofer (W.25.200.8.MC - Nagłośnienie STX) from a Polish company called STX. Specs are within 5%, well were on the several pairs I had.
The Monacor SPM-205/8 can also do well - its a nice unit for the money and can be used in classic TL designs, also cheap and easy to acquire in Europe. 🙂
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Is too much if I ask you for plans? Maybe some measurements?
I'm afraid that the maximum power is too low or, in other words, that the maximum SPL is too low because I like listening loudly. Not necessarily very loud, but I am afraid that there may be limitations to dynamics at the fortissimo passages. I'm afraid that the med's will reach the maximum excursion too early due to too low crossover.
With the speakers I use now, no matter how loud the amplifier is, I do not feel any change in the music timbre until the amplifier protection is activated.
The amplifier is capable of 100W-RMS, minimum 170W peak (+/-56V power rails).
Thank you!
PS: these are the speaker that I use now: speakers comparison
I'm afraid that the maximum power is too low or, in other words, that the maximum SPL is too low because I like listening loudly. Not necessarily very loud, but I am afraid that there may be limitations to dynamics at the fortissimo passages. I'm afraid that the med's will reach the maximum excursion too early due to too low crossover.
With the speakers I use now, no matter how loud the amplifier is, I do not feel any change in the music timbre until the amplifier protection is activated.
The amplifier is capable of 100W-RMS, minimum 170W peak (+/-56V power rails).
Thank you!
PS: these are the speaker that I use now: speakers comparison
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The OP mentioned nothing of a side mounted woofer. If that is the goal, then I agree that 150 is about the highest you should go.
Later,
Wolf
Of course not, its a diy forum, diy should be fun 🙂
I have limited measurements as the hard drive went through a mboard explosion, but i think we did cloud them on google drive.