Oliver
Although it was done in a haste thanks, I know if you have the time it wouldn't be done in rush.
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Hi,
Your discussing adding an 18" in a vented box to the above.
At some point the technical issues should be discussed rather than assumed.
2 15" drivers have ~ 40% more cone area than an 18" and assuming the
box for them is not small there is no good reason to assume adding an 18"
(or two) will bring anything to the party.
I'd like to help, but there is no detail to go on. There are fundamental
technical issues regarding what is being attempted and whether it
will turn out a success or a disappointing failure. It would be fair to
say that as what would be a "success" is not described, its unlikely.
The speakers already seem like they can play plenty loud enough and
adding more bass could be just a question of additional EQ and/or
port retuning of the 2x15.
If really low bass is wanted what counts is not high driver efficiency, it
is simply high excursion capability and having enough juice to reach it.
Yes it is hard. Especially if your stumbling around in the dark.
A full description of the current speakers and amplication is needed.
I mean a full description, driver specs, tuning, volume/sizes, construction etc.
Pictures or links would be nice.
Also there use, i.e. indoor (room sizes) or outdoor, if outdoor free
standing or are there any walls/corners available to stack it against.
Aso a reasonable statement of what you expect to do to the system, play
louder ? lower ? cleaner ? just make the system look more impressive ?
(The last point isn't as trite as it seems, too many assume looking
like it should be better mans it will be better, and that is not the case.)
Only with that can you sensibly proceed.
And work out whether you need 1 or 2 18"ers per side, or something else.
rgds, sreten.
An "old bass coffin" is mentioned on the first page. What happened to it ?
died ? discarded ? because it wan't good enough ? because its not needed ?
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Sreten
Speaker(bc18tbx100)
Size dimension 22w x27h 30d. Or whatever is best.
Two 18 per side. One per box.
Tuning 35hz to 200hz or whatever is best.
Amps(qsc3000mx)
Used where(outdoor free standing)
Sound quality( loud clean and low deep bass)
Construction( ported box build with 3/4" ply)
The two 15's play upper bass.
Let me know if you need More info
Speaker(bc18tbx100)
Size dimension 22w x27h 30d. Or whatever is best.
Two 18 per side. One per box.
Tuning 35hz to 200hz or whatever is best.
Amps(qsc3000mx)
Used where(outdoor free standing)
Sound quality( loud clean and low deep bass)
Construction( ported box build with 3/4" ply)
The two 15's play upper bass.
Let me know if you need More info
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Hi,
The drivers recommended box is 200L tuned to 34Hz.
To hit maximum SPL in the bass you must use a subsonic filter, as
all vented boxes quickly overload below the port tuning frequency,
not so critical at modest domestic volumes but a killer outdoors.
To go deeper (but not as loud) you could tune lower, say 26Hz
and use a peaking high pass filter, 2nd order q=1.5 set to 26Hz
as a combined bass boost and subsonic filter, flat to 30Hz.
This can be build into the feedback loop of the power amplifier.
Power handling for 34Hz is around 600W at 50Hz, higher either
side, around 450W at 40Hz for the lower tuning. Power handling
for the higher tuning drops like a stone at 30Hz. lower tuning 23Hz.
Max SPL is around 123dB in the bass for the higher tuning, around
119dB for the lower tuning, both hit 127dB 100Hz to 200Hz, 1kW.
All numbers are for one driver into half space.
With 3/4 ply add extensive bracing or ribbing or both.
rgds, sreten.
The drivers recommended box is 200L tuned to 34Hz.
To hit maximum SPL in the bass you must use a subsonic filter, as
all vented boxes quickly overload below the port tuning frequency,
not so critical at modest domestic volumes but a killer outdoors.
To go deeper (but not as loud) you could tune lower, say 26Hz
and use a peaking high pass filter, 2nd order q=1.5 set to 26Hz
as a combined bass boost and subsonic filter, flat to 30Hz.
This can be build into the feedback loop of the power amplifier.
Power handling for 34Hz is around 600W at 50Hz, higher either
side, around 450W at 40Hz for the lower tuning. Power handling
for the higher tuning drops like a stone at 30Hz. lower tuning 23Hz.
Max SPL is around 123dB in the bass for the higher tuning, around
119dB for the lower tuning, both hit 127dB 100Hz to 200Hz, 1kW.
All numbers are for one driver into half space.
With 3/4 ply add extensive bracing or ribbing or both.
rgds, sreten.
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Hi,
The higher tuning is best if your only subsonic filter option is non peaking,
and that should be set to around 30Hz, 2nd or 3rd order Butterworth
are the usual options, both only need one op-amp, and must be used
to approach anywhere near the bass ends maximum capability.
Not always, a lot of recordings have little bass below 40Hz, but if
one comes along that does you would be in trouble. If the sound
source is a PC then plugin bass filters are a very viable option.
The lower tuning + mildly peaking filter is better, sound quality wise but the
extra bass extension lowers the maximum SPL as extra bass always does.
The recommended box and tuning is hard to argue with, especially outdoors.
rgds, sreten.
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Hi Nathenry,
I generally agree with sreten's comments on tuning and filtering, it may be important, to point out, that he is referring to the box recommended in the factory data sheet, not the B&C SUB18 as recommended earlier in this thread. As to filters, it is my opinion, that a bass reflex enclosure should not be used in high power applications (i.e.: PA or block parties) without a suitable low cut (high pass) filter; when the low frequency content of the music drifts below the tuning frequency of the enclosure, the excursion of the driver will become excessive...
The 18TBX100 data sheet shows an example of a BR enclosure w/ a volume of 200 L and a tuning frequency of 34 Hz. It uses a port with an area of 339.6 cm^2 and a length of 26 cm.
The previously recommended factory B&C SUB18 (Post #9) is 183 L and tuned to 35 Hz. It uses a split slot port with an area of 541.2 cm^2 and a length of 32 cm.
I want(ed) to point out, that you can reduce the internal volume even more without any negative effects. I'll attach another Hornresp Wizard screenprint, this time I shortened the port(s) to 25.40 cm (10"). You can see the effect on the frequency response, and the tuning frequency (bottom right: Helmholtz freq is 39.53Hz). In other words, you can tune either one of these boxes high or low. I also tried to make this box as easy to build as possible.
I'll also attach a Rev. A of the drawing:
Regards,
I generally agree with sreten's comments on tuning and filtering, it may be important, to point out, that he is referring to the box recommended in the factory data sheet, not the B&C SUB18 as recommended earlier in this thread. As to filters, it is my opinion, that a bass reflex enclosure should not be used in high power applications (i.e.: PA or block parties) without a suitable low cut (high pass) filter; when the low frequency content of the music drifts below the tuning frequency of the enclosure, the excursion of the driver will become excessive...
The 18TBX100 data sheet shows an example of a BR enclosure w/ a volume of 200 L and a tuning frequency of 34 Hz. It uses a port with an area of 339.6 cm^2 and a length of 26 cm.
The previously recommended factory B&C SUB18 (Post #9) is 183 L and tuned to 35 Hz. It uses a split slot port with an area of 541.2 cm^2 and a length of 32 cm.
I want(ed) to point out, that you can reduce the internal volume even more without any negative effects. I'll attach another Hornresp Wizard screenprint, this time I shortened the port(s) to 25.40 cm (10"). You can see the effect on the frequency response, and the tuning frequency (bottom right: Helmholtz freq is 39.53Hz). In other words, you can tune either one of these boxes high or low. I also tried to make this box as easy to build as possible.
I'll also attach a Rev. A of the drawing:
Regards,
Attachments
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Hi,
If you restrict the bass output of a PA cabinet it will generally handle
more power and go louder in the bass range it covers. As said you
need a high pass filter. Some high output high power handling bass
PA cabinets are very surprisingly restricted in real bass response.
e.g. This 1 x 18" :
Allegedly does 136dB, but
"Frequency Range loud (-10 dB) 50Hz -142 Hz".
"Frequency Range deep (-10 dB) 45Hz -138 Hz".
-10dB at 50Hz and 45Hz is no great shakes by anybodies standards.
rgds, sreten.
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