Hello everyone,
We have a small soundsystem (5-way) where we use a 2x12 reflex box to cover the frequencies from 200 Hz to 2000 Hz. We built this box a couple of years ago with no expenses and no knowledge, but now we have a couple of good drivers (PD121) and so we've been trying to use WinISD to build a new box with better wood, ecc. in order to replace the old cabinet.
We would also like the new box, apart from being able to cover the 200 Hz - 2000 Hz range, to have the possibility of being used in a smaller scenario, for example inside a cafe, as a bass cabinet (hp filter from 60 Hz with dcx2496?). Hence why we would like it to be a reflex design.
Using WinISD for the first time, right now where we stand is:
The thing we would like to know are:
Please don't be too harsh if we've thought all of this completely wrong, it's our first time using the software and we suppose that the easiest thing to do would be to just do a sealed box for the 200-2000 Hz range.
Lastly, we have to possibility to get Crown XS1200 for a cheap price. We already have one, and it seems to suit our needs. Looking at the PD121 peak at 1200 watts, we should be ok connecting 2x PD121 in parallel to one channel --> 1100 watts at 4 Ohms, right?
Kindest regards,
Dan
We have a small soundsystem (5-way) where we use a 2x12 reflex box to cover the frequencies from 200 Hz to 2000 Hz. We built this box a couple of years ago with no expenses and no knowledge, but now we have a couple of good drivers (PD121) and so we've been trying to use WinISD to build a new box with better wood, ecc. in order to replace the old cabinet.
We would also like the new box, apart from being able to cover the 200 Hz - 2000 Hz range, to have the possibility of being used in a smaller scenario, for example inside a cafe, as a bass cabinet (hp filter from 60 Hz with dcx2496?). Hence why we would like it to be a reflex design.
Using WinISD for the first time, right now where we stand is:
- Box Voume: 109.5 L
- Tuning Fr: 70 Hz
- Vents: 2x squared - Area = 277 cm^2 - Vent Length = 5.70 cm - 1st port resonance: 3005.15 Hz
The thing we would like to know are:
- Regarding the tuning frequency, should we aim for a lower tuning? Looking at the driver datasheet, stated Fs is of 53.27 Hz, and we've always heard to stay above it with the hp filter.
- Another thing we've heard is to keep the 1st resonant frequency of the port out of the desired frequency range. Would in this case 3k Hz be ok or should we aim for higher, 4k?
- Cone excursion. This is something we can't really understand on WinISD, as both this, and the sealed 2x12 sealed version (same volume, just for comparison) seem to go over excursion really fast from around 150/200 Hz down. But, this depends on signal input power and we're not really sure what value to put there.
Please don't be too harsh if we've thought all of this completely wrong, it's our first time using the software and we suppose that the easiest thing to do would be to just do a sealed box for the 200-2000 Hz range.
Lastly, we have to possibility to get Crown XS1200 for a cheap price. We already have one, and it seems to suit our needs. Looking at the PD121 peak at 1200 watts, we should be ok connecting 2x PD121 in parallel to one channel --> 1100 watts at 4 Ohms, right?
Kindest regards,
Dan
A thing I forgot to mention. I've seen that WinISD has the parameters of the driver, but they are different from the ones in the datasheet. So I put the ones from the datasheet (PD121, not PD121/2) on WinISD and used those ones.
Dan,
The PD.121 is a good midrange driver designed for use over 100Hz.
The lower the tuning frequency (Fb), the less SPL at Xmax (only 2.7mm).
Each doubling of excursion allows +6dB more output.
12" wide band woofers with 6mm Xmax are common, sub woofers double that.
The HP filter should be set just below Fb, where excursion rises uncontrollably, and results in little output.
3kHz port resonance with a 2kHz crossover (12dB/octave or greater) is not a problem.
When using the drivers for midrange, the ports could be plugged with hard foam inserts.
Exceeding Xmax will cause the driver to distort as the coil is driven out of the magnetic gap.
It won't take much power at all to exceed Xmax about 1/3 octave above Fb (tuning frequency).
With a 70Hz Fb, probably looking at around 108dB at one meter max at the low E of a guitar (81Hz), compared to 123dB at 200Hz (sealed).
Oops, you said 2x12", so you can add +6dB, 114dB and 129dB.
You are OK connecting it, but can easily make the speakers flap at lower frequencies with a fraction of that power.
The DCX2496 has dynamic EQs for level-dependent equalization, you could use them as frequency dependent limiters.
Art
https://www.usspeaker.com/faital pro 12pr330-1.htm
I‘ve used this driver to build quite a few full range 2 ways and it will do just what you need.
A pair will need 4 cuft ported and tuned to 50hz. When you use it for your 5 way, simply block off the port……you’ll be high passing it in that application at 200hz so nothing to resonate anyway. The sealed box will have a lower Q than what’s best for it in that application but there won’t be any significant loss to performance. Make sure the port plug is tight and won’t pop out during use.
I‘ve used this driver to build quite a few full range 2 ways and it will do just what you need.
A pair will need 4 cuft ported and tuned to 50hz. When you use it for your 5 way, simply block off the port……you’ll be high passing it in that application at 200hz so nothing to resonate anyway. The sealed box will have a lower Q than what’s best for it in that application but there won’t be any significant loss to performance. Make sure the port plug is tight and won’t pop out during use.
Any 12" driver will be beaming at 2kHz, so be prepared for narrow dispersion! Additionally, comb filtering of large drivers will cause additional problems well below 2kHz.
Agreed, and many PA systems sounded - and still sound - absolutely dreadful, both on- and off-axis! 🤣
I've been playing that game for 40+ years...
I've been playing that game for 40+ years...
These guys are using a 5 way mono PA they consider 'small' .........there's bigger fishes to fry i think
To weltersys:
We were a little bit sceptical about the reflex idea, but now we have some more information, and in this case it seems that the xmax is just too small for lower frequency handling. We will think this through as we have 2x15 reflex (plan is BBC BR215) that we use as kick in our sessions. We can maybe use that in smaller scenarios as a bass cabinet, and with these PD121 drivers focus on sealed midrange cabinet that can work well from 100 Hz up or similar.
Regarding the rest of the comments, we already have these drivers at hand, and we see other roots/dub soundsystems using 2x12 cabinets for midrange, or 2x10, sealed or ported, under horns and tweeters for example.
We consider our PA small mostly because we see around soundsystems with 18 inch scoops, or 21 inch bp, and we are currently using a couple of 15 inch scoops, borrowed from a friend. In that sense we see our sound as small, as high SPL at sub levels is not really achievable, yet. Nevertheless, scoops have a really specific sound that does help with genres we deal with. We play mostly roots and dub music, so it's natural for us to look at and take inspiration from those kind of PA's.
Other questions we have:
- What kind of material does WinISD use? We are looking at birch plywood but we are not sure if 18mm or 15mm. Of course 15mm is cheaper and maybe would make sense if the cabinet will be built to be used only as a midrange. Using the cabinet, supposedly sealed, only in 200-2000 Hz range, would there be a sensible better choice between 15mm and 18mm plywood?
The enclosure volumes in WinISD do not use any material.
Well braced 15mm plywood is stiff enough for use above 100Hz.
11 ply 15mm Baltic Birch has been used for large production bass horn systems, though 13ply 18mm requires less bracing.
Lighter plywood with adequate bracing works fine too, but is less resistant to road abuse.
Well braced 15mm plywood is stiff enough for use above 100Hz.
11 ply 15mm Baltic Birch has been used for large production bass horn systems, though 13ply 18mm requires less bracing.
Lighter plywood with adequate bracing works fine too, but is less resistant to road abuse.
If this is the case, the enclosure is way too large or you are trying to get LF extension of which the driver is not capable. I have not simulated it, but 200Hz ought to be a doddle for that driver.
To do dub reggae justice, multiple 18"+ subs are a must as this is where your system will run out of puff first! My single 10" mids cross over at 100Hz and the 4 x 18" sealed subs match perfectly, output-wise.