I have touched that topic in few discussions, but never got enough good arguments, so here it is.
Modern subwoofers have enough motor force and displacement, that the bassreflex port on a ported bin is often almost not needed.
At least not fully in band. Now I use it just for cone displacement control, impedance shaping and cooling, otherwise it works for me almost out of band. As it is out of band, it can be small, it doesn't get the efficiency hit of small port, port noise is low, power compression is low, what's not to like?
Speaking about 18" subwoofer in a 95l/3.55cu.ft box, tuned at roughly 28Hz, used between 34 and 85Hz. I first did it with 21"s.
Seemingly it works great for its box volume. Only the price per woofer is somewhat higher.
Is here someone willing to discuss and object to get to the bottom of things? Why noone is doing it ever?
Many thanks.
Modern subwoofers have enough motor force and displacement, that the bassreflex port on a ported bin is often almost not needed.
At least not fully in band. Now I use it just for cone displacement control, impedance shaping and cooling, otherwise it works for me almost out of band. As it is out of band, it can be small, it doesn't get the efficiency hit of small port, port noise is low, power compression is low, what's not to like?
Speaking about 18" subwoofer in a 95l/3.55cu.ft box, tuned at roughly 28Hz, used between 34 and 85Hz. I first did it with 21"s.
Seemingly it works great for its box volume. Only the price per woofer is somewhat higher.
Is here someone willing to discuss and object to get to the bottom of things? Why noone is doing it ever?
Many thanks.
i always tune reflex ports as low as possible to 25 / 30hz.
Its the best way if you cannot filter a higher tuned reflex with a high pass.
just tune it low always sounds good.
Its the best way if you cannot filter a higher tuned reflex with a high pass.
just tune it low always sounds good.
Not likely.
Have you made simulation with 1200 or 1600 W subwoofer and their Xmax? The goal in PA/professional sound reinforcement is to get maximum SPL within desired frequency band. Unfortunately, very often Xmax is reached before their max Wattage.
Which 18" driver are you using?
Not sure what the discussion or argument is, but it is common to limit bandwidth to above the Fb (box tuning) in PA subs, like the EAW SB1001:
It has an Fb of 30Hz, raw response at 30Hz ~-12dB from 100Hz, the processing HP is around 40Hz, LP~100Hz.
As far as your cabinets being about half the volume of typical ported PA subs, the only thing not to like is the reduced SPL available from a port in that small a volume.
Art
This is kind of chicken and egg thing for me, regarding wattage. Reaching the wattage means power compression and danger. Xmax is so much easier to control for...
Anyways, you are right. I should say "some, few modern drivers" not "plenty or most of these".
I could be even more specific. For example B&C speakers spend A LOT power at their Xmax/Xvar value, and are not that happy to work there all the time. Most of these are out of question. RCF, 18Sound NTLW, Faital Pro, these have not such issues.
I am talking about drivers hanging around 15mm of Xmax. So, RCF LF18X451, LF18N408, LN16S400/LN18S400/LN18S450 and such. B&C 21DS115 seems to qualify, not sure about 18SW115(had it in my paws) and 18DS115 (also, but didn´t test for it).
Currently I am using RCF LF18X451.
After all the simulations (EQ, power compression, driver power going in), it looks like it could do the job, Indeed the goal is to maximise SPL. That´s what I´m talking about too. Only detail to that, or parameter to that, is SPL density in a small box. On top of other personal goals in chain, I am trying to maximise SPL, and it seems to be a working way.
@weltersys
Well?! You got me. Hard time arguing that it is not a standard practice. But here it is! You beat me to it.
Reduced SPL from the port is not an issue, as it is engineered to assist, not to make much of SPL anyways.
The goal is SPL density in a compact light box, so less utilisation of the driver gets kind of obvious.
Good one, sir. After all I am not insane, I am just blind.
Well?! You got me. Hard time arguing that it is not a standard practice. But here it is! You beat me to it.
Reduced SPL from the port is not an issue, as it is engineered to assist, not to make much of SPL anyways.
The goal is SPL density in a compact light box, so less utilisation of the driver gets kind of obvious.
Good one, sir. After all I am not insane, I am just blind.
Now, the question that comes to mind is, why this EAW SB1001 approach is not used that widely? Is it because people rather want to exploit the driver capabilities fully, at the cost of more wood?
? That is simply not true - B&C drivers are not much different than drivers from other brands you mentioned. Just pick a driver according to your needs.
B&CSW115 is very similar to RCF LF18X451. Both do not reach their Xmax even with their maximum 1700/1800 W input power.
? SB1001 is simple vented double 18" in compact "V" configuration. Nothing unique - just very well executed subwoofer.
That is true. It has been measured by quite few people. Lately with this approach, I measure apparent power spent on the coil at Xmax/Xvar of the driver. There is no talking about it.
Some of that even can be found on data-bass platform still. B&C drivers are positively tighter, no question about it. For example 21DS115 compared to Lavoce San214.50, which goes well above Xmax, no issue.
Reaching Xmax is matter of enclosure design, and the RCF LF18X451 certainly reaches it in the sims of my design.
Doesn't matter how we call SB1001, the core of it is that it allegedly uses the same design. Undersized volume, low tuning, cutting above port tuning. That certainly can be called unconventional. Yet it is proof of the design I am contemplating on.
It's hard to find a PA sub raw response that does not have a rising response at higher frequency.
With the trend towards built in amplification, the raw response is harder to find.
Most PA people (and manufacturers) want to maximize the output per cost, and more wood makes for a better SPL/$ ratio at low frequencies.
A big port is never going to overheat and fail 😉
You have managed to eloquently describe something I couldn't find words for. I have a working example of such use of a port designed by a pro mobile installer 25yrs ago
Currently, I am also working on a bass reflex with a such a port. That enough from me though as the tech side of the discussion is above my pay grade
Response of many drivers
on paper is roughly same.
Comparing 15" to 18"
In a reflex
Thing is 15" Fs is still high.
Around 40 to even 55 Hz.
So they unload hard from EQ
with high port tuning.
18" can be tuned to 20 to 35 Hz
Takes EQ better wont unload with
live bands. Electronic Music , tortures anything
regardless.
4 cubic foot 18 inch bins
nothing new these days.
People want small boxes.
Its a generic for
a lot of manufactures.
Generic 2x18 does similar
little over 7 cubic feet.
So each driver is in , too small
volume.
Dont do much more than a 2x15
Dual 18 Just sounds slightly more workable and deep
with typical EQ bass boost.
on paper is roughly same.
Comparing 15" to 18"
In a reflex
Thing is 15" Fs is still high.
Around 40 to even 55 Hz.
So they unload hard from EQ
with high port tuning.
18" can be tuned to 20 to 35 Hz
Takes EQ better wont unload with
live bands. Electronic Music , tortures anything
regardless.
4 cubic foot 18 inch bins
nothing new these days.
People want small boxes.
Its a generic for
a lot of manufactures.
Generic 2x18 does similar
little over 7 cubic feet.
So each driver is in , too small
volume.
Dont do much more than a 2x15
Dual 18 Just sounds slightly more workable and deep
with typical EQ bass boost.
I would like to talk about that, still. We are not talking about the same, obviously.
I am familiar with the measurements from Data-Bass. Lavoce SAN214.50 was tested in a sealed enclosure, not vented! You are talking about vented enclosures all the time! Apples and oranges...
B&C 21DS115 was tested in both sealed and vented enclosures. Measurements in sealed enclosure are similar to Lavoce SAN214.50. Between 16 Hz and 40 Hz Lavoce has slightly greater SPL output (0.2 - 0.9 dB), but at 80 Hz and 100 Hz it has slightly lower SPL output (0.4 - 0.5 dB). So, basically the same.
If you are reaching Xmax in a vented enclosure, something is wrong with your RCF LF18X451 design.
@weltersys
Indeed most people will grab for best bang/buck ratio. It is just that one would think that there is enough people that look for other things. The mainstream majority is larger than expected. Any deviation, even reasonable, and you are out. Alone. Not much data, support and such. It somewhat bugs me.
@WhiteDragon
Yes, I have simmed this with 15's too, and it stops being feasible. Higher Fs, often less Xmax, then you need almost double the drivers. But the motor is often the same, so price is almost the same per driver. At times, that's why 21" is feasible too. The cone area/displacement is cheaper.
4cu.ft box is nothing new, but rarely it is in the field tuned under 30Hz. To date, I have seen zero compact 18" tuned like that.
Indeed most people will grab for best bang/buck ratio. It is just that one would think that there is enough people that look for other things. The mainstream majority is larger than expected. Any deviation, even reasonable, and you are out. Alone. Not much data, support and such. It somewhat bugs me.
@WhiteDragon
Yes, I have simmed this with 15's too, and it stops being feasible. Higher Fs, often less Xmax, then you need almost double the drivers. But the motor is often the same, so price is almost the same per driver. At times, that's why 21" is feasible too. The cone area/displacement is cheaper.
4cu.ft box is nothing new, but rarely it is in the field tuned under 30Hz. To date, I have seen zero compact 18" tuned like that.
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Cutting at or above port tuning is routine in PA - hardly unconventional.
Undersized volume and low tuning always result in lower SPL in the low frequency band - matter of design compromise. Pick your poison.
Are you sure that drivers in SB1001 are in undersized volume?
Yes it seems like miscomunication.
I mentioned tight suspension "as is" on a driver. That means with no enclosure involved. The B&C speaker is tighter and spends more power at Xmax by itself. So there is no connection to the enclosure, I am not mixing sealed and vented here. Sorry for confusion. Maybe, we discuss one at a time.
Now reaching Xmax in vented enclosure with LF18X451 is not exactly wrong, or out of control. This is very on purpose, as the available speaker displacement volume is utilised on purpose to the fullest here. Very on purpose. Lower port tuning allows for it.
It can be different value in box on dynamic signal, but in the personal standarized test, the LF18x451 only spends 120VA to reach 15mm of excursion. That is very low. Also it has very forced cooling that gets loud. Contrary to B&C, which seem to chuff and cool somewhat less, and eats more power at Xvar. So it is less happy to be driven in such configuration.
It is highly unconventional use, one could say "rubbing it the wrong way", but we're here for the outcomes that are possible, not for following old rules that became unfounded with more capable technology.