If you boost atr the box tuning frequency, you will still get an increase in excursion, but as it will have been low anyway, it may well stay within Xmax, so not necessarily a problem.
However, it will increase the power demanded from your amp (particularly as electrical impedance is low at tuning frequency, so it really will ask for good current delivery) and it will increase vent airspeed a lot too.
Edit PS: it looks a lot like you're using WinISD, so you can easily model this for yourself in the "Filters" section of the program ;-)
However, it will increase the power demanded from your amp (particularly as electrical impedance is low at tuning frequency, so it really will ask for good current delivery) and it will increase vent airspeed a lot too.
Edit PS: it looks a lot like you're using WinISD, so you can easily model this for yourself in the "Filters" section of the program ;-)
Ok cool....thanks for the reply David...
Asking more power, or higher vent air velocity is pretty obvious.
As long as there is no negative impact on the overall driver+port system it's fine.
By the way, winisd filters are not very relaistic. They are ok for reference though....
Asking more power, or higher vent air velocity is pretty obvious.
As long as there is no negative impact on the overall driver+port system it's fine.
By the way, winisd filters are not very relaistic. They are ok for reference though....
Small bluetooth speakers with passive radiators sometimes do this. One of the JBL's (Flip? Charge?) has its passive radiators tuned at 70 Hz and applies boost at 70 Hz. This way there is lots of 'bass' output from the 2" full range drivers.
The passive radiators have to displace more air, but that is not a problem for them.
The passive radiators have to displace more air, but that is not a problem for them.
Could you expand on that please?
I'm aware that many DSP platforms have variations in how they calculate things like filter Q's, so we have to be careful transferring settings from one make/model to another, but AFAIK WinISD is modelling "theoretically ideal" filters, so there shouldn't be anything unrealistic as long as we can accurately implement what is modelled?
Hi guys ....sorry my word "realistic" might sound a bit misleading. They are more theoriticall as David pointed.
But i there might be a chance of a bug. End correction for port didn't work for me. If you manually edit end correction values, winisd doesn't change port length.
But i there might be a chance of a bug. End correction for port didn't work for me. If you manually edit end correction values, winisd doesn't change port length.
yes, the port correction is bugged. i never rely on it anyway, except to estimate maximum port length vs box dimensions.
all my builds seem to end up with weird port configurations anyway, making any calculation moot.
i prefer to build, measure system impedence with DATS, and trim the port length until I reach the desired tuning.
all my builds seem to end up with weird port configurations anyway, making any calculation moot.
i prefer to build, measure system impedence with DATS, and trim the port length until I reach the desired tuning.
I guess the theory of all the tuned systems needs to be re-thought in light of readily available DSP today. And the old sims (and T/S computational model too) are looking too rudimentary to be useful if they don't allow you to input parametric EQ.
All the tuned boxes (BR, pseudo-horn, QWTL...) have dual outputs which is (a) anaesthetic engineering (AKA nuts) and (b) complex. But true horns, sealed boxes, and labyrinths (ahem, ahem) don't have those complexities in the same ways. Ditto for non-box mounting.
B.
All the tuned boxes (BR, pseudo-horn, QWTL...) have dual outputs which is (a) anaesthetic engineering (AKA nuts) and (b) complex. But true horns, sealed boxes, and labyrinths (ahem, ahem) don't have those complexities in the same ways. Ditto for non-box mounting.
B.
6th order boosted ported.
you basically use a high pass filter with a q = 2 at the tuning frequency.
I like to use low qts drivers, then tune to the Fs if qts = .312 (or box's f9 if you tuned to Fs) then use the filter above.
It boosts output by 6db at tuning (now -3db there) and doesn't bottom out because the filter acts like a subsonic filter, and the driver isn't moving much at tuning frequency already.
If anything, the sub now " gets up and goes" because it isn't trying to reproduce the really low stuff.
you basically use a high pass filter with a q = 2 at the tuning frequency.
I like to use low qts drivers, then tune to the Fs if qts = .312 (or box's f9 if you tuned to Fs) then use the filter above.
It boosts output by 6db at tuning (now -3db there) and doesn't bottom out because the filter acts like a subsonic filter, and the driver isn't moving much at tuning frequency already.
If anything, the sub now " gets up and goes" because it isn't trying to reproduce the really low stuff.
To stress this some more: At port tuning frequency, the cone excursion is little, while the impedance is at its lowest. Meaning that you are pushing most power where the coil does not move as much, lacking cooling effect. Then some DJ wants to feed your intestines with solid bass line right at the port tuning frequency of your box for few minutes, and you can rest assured there will be some cooking sooner or later, and then silence. If you are lucky, the amplifier might shut down sooner. Many just don't...
Regarding BT speakers radiators, this is true, but very general. Firstly, small cones move quite a bit more (in proportion), secondly, it is not such problem to dissipate 4W against 40W, compared to big subs with 400W/4000W ratio.
And lastly, I am delighted that my Energy Sistems Urban5+ or whatever is the name, is tuned to 40Hz. When put in the corner of larger room, it truly produces some serious bass. 🙂
Regarding BT speakers radiators, this is true, but very general. Firstly, small cones move quite a bit more (in proportion), secondly, it is not such problem to dissipate 4W against 40W, compared to big subs with 400W/4000W ratio.
And lastly, I am delighted that my Energy Sistems Urban5+ or whatever is the name, is tuned to 40Hz. When put in the corner of larger room, it truly produces some serious bass. 🙂
I remember years ago, bandpass subs would just go silent.
At certain frequencies, cone not moving much, then build up of heat.
I remember djk mentioning that for pa. He had some subs in a club, retuned them to 40hz, rolled them there, never had a problem.
At certain frequencies, cone not moving much, then build up of heat.
I remember djk mentioning that for pa. He had some subs in a club, retuned them to 40hz, rolled them there, never had a problem.