Do those charts take account of the rumble filter? It doesn't look like they do. GD will go up, excursion should be controlled below tuning. Look at excursion - you reach xmax at 100w because the rumble filter is either not shown or not doing its job - the driver is idling above tuning and below it is out of control.
Does your program allow you to input filters and see their impact? If not use WinISD pro. You can't design it properly without doing this. The F3 will be altered by modelling the lowpass filter, and this will affect your choice of box volume and vent tuning.
Vent velocity is too high. This will be improved by the rumble filter, but those charts don't seem to show the effect. Again, they need to be included, then you will see how the rumble filter will reduce turbulence by reducing the extreme excursions below tuning.
Look up Collo's vent calculator - which shows acceptable vent velocity for a vent of a given size and flare radius.
You should be able to achieve an F3 from 20 - 25 Hz. Model the lowpass filter, experiment with tuning and box size - bigger box and lower tuning will give you more bottom end.
What is the F3 of your mains and what is their rolloff? Are they vented or sealed?
150 Hz is a high xo point - up to this point you would ideally be considering stereo subs since they are operating into the midrange.
Does your program allow you to input filters and see their impact? If not use WinISD pro. You can't design it properly without doing this. The F3 will be altered by modelling the lowpass filter, and this will affect your choice of box volume and vent tuning.
Vent velocity is too high. This will be improved by the rumble filter, but those charts don't seem to show the effect. Again, they need to be included, then you will see how the rumble filter will reduce turbulence by reducing the extreme excursions below tuning.
Look up Collo's vent calculator - which shows acceptable vent velocity for a vent of a given size and flare radius.
You should be able to achieve an F3 from 20 - 25 Hz. Model the lowpass filter, experiment with tuning and box size - bigger box and lower tuning will give you more bottom end.
What is the F3 of your mains and what is their rolloff? Are they vented or sealed?
150 Hz is a high xo point - up to this point you would ideally be considering stereo subs since they are operating into the midrange.
I did some sims in WinISD.
Try this:
35L net box volume
20 Hz tuning
Set highpass (rumble filter) to 10 Hz 2nd order (based on the bk amp specs - a bit of a guess)
Set lowpass (crossover) to 2nd order @ 55 Hz
Result:
F3 @ 20 Hz
Upper -3db point is 100 Hz
With 100w max excursion is exceeded below tuning as expected, but this should be within the suspension limits of the driver so it is safe and would mostly only occur with movies. Above tuning the driver is idling at 100w. For music it will have an easy job.
Vent velocity is high. A 65mm PVC pipe needs to be 660mm long to achieve tuning and flares on each end are essential - as big as you can mange to build. Vent velocity reaches 28m/s which may be a problem at times. If you go with a bigger vent this will reduce vent chuffing, but because the box is small, the vent will be long. You could improve on this aspect using a 45L box with a 90mm vent which will now need to be 1m long but the velocity will remain below 17m/s now.
This driver is difficult in a small vented box! It really does want a PR.
If you opt for a sealed version the response does not look good without eq. There is no mention of boost on that amp. Now, if you are a bit clever, you can actually get a good sealed response with some fiddling. Try this. Put it in a 28L sealed box (1 cu ft) and put a 2nd order lowpass at 38 Hz. What you get now is -3db points at 25 and 80 Hz - not bad.
Looking back at what speakers you have, I think either of these would be more than adequate:
1. 35L vented design with the small vent (yes a compromise but more than enough to go with those speakers)
2. 28L sealed design
The sub will be well beyond those speakers, and later you might consider upgrading at least a stereo pair to replace the front 3 speakers. Replace them with say a modest bookshelf speaker with a 6.5" midbass driver in a sealed box.
Try this:
35L net box volume
20 Hz tuning
Set highpass (rumble filter) to 10 Hz 2nd order (based on the bk amp specs - a bit of a guess)
Set lowpass (crossover) to 2nd order @ 55 Hz
Result:
F3 @ 20 Hz
Upper -3db point is 100 Hz
With 100w max excursion is exceeded below tuning as expected, but this should be within the suspension limits of the driver so it is safe and would mostly only occur with movies. Above tuning the driver is idling at 100w. For music it will have an easy job.
Vent velocity is high. A 65mm PVC pipe needs to be 660mm long to achieve tuning and flares on each end are essential - as big as you can mange to build. Vent velocity reaches 28m/s which may be a problem at times. If you go with a bigger vent this will reduce vent chuffing, but because the box is small, the vent will be long. You could improve on this aspect using a 45L box with a 90mm vent which will now need to be 1m long but the velocity will remain below 17m/s now.
This driver is difficult in a small vented box! It really does want a PR.
If you opt for a sealed version the response does not look good without eq. There is no mention of boost on that amp. Now, if you are a bit clever, you can actually get a good sealed response with some fiddling. Try this. Put it in a 28L sealed box (1 cu ft) and put a 2nd order lowpass at 38 Hz. What you get now is -3db points at 25 and 80 Hz - not bad.
Looking back at what speakers you have, I think either of these would be more than adequate:
1. 35L vented design with the small vent (yes a compromise but more than enough to go with those speakers)
2. 28L sealed design
The sub will be well beyond those speakers, and later you might consider upgrading at least a stereo pair to replace the front 3 speakers. Replace them with say a modest bookshelf speaker with a 6.5" midbass driver in a sealed box.
Reasons why:
1) If the amp doesn't seal properly, you get farting sounds that sound like those ghetto blasters turned up full - the air rushes through around all the dials
2) Some cheap plate amps have a plastic cover to the amp contents and under pressure inside a sealed box would become like an secondary unwanted transducer
3) Box will be more solid and inert overall, with less to vibrate and colour the sound.
1) If the amp doesn't seal properly, you get farting sounds that sound like those ghetto blasters turned up full - the air rushes through around all the dials
2) Some cheap plate amps have a plastic cover to the amp contents and under pressure inside a sealed box would become like an secondary unwanted transducer
3) Box will be more solid and inert overall, with less to vibrate and colour the sound.
Not a stupid question at all.
There is a difference between the point where you set the filter (corner frequency fc) and the actual -3 db point. If you look back, you will see that while the fc is 38 Hz but the resulting -3 db point is 80 Hz. So if you set the fc at 120 Hz then you might actually get the -3 db point too high.
What you need to do is have a play with WinISD pro. Put in the numbers. Put in filters. Keep adjusting until you get the -3 db point where you want it, say 120 Hz. Try the fc at say 60 Hz and see what you get. This all sounds so much more confusing when it is written down, but when you actually try it and see the charts, it's very simple.
There is a difference between the point where you set the filter (corner frequency fc) and the actual -3 db point. If you look back, you will see that while the fc is 38 Hz but the resulting -3 db point is 80 Hz. So if you set the fc at 120 Hz then you might actually get the -3 db point too high.
What you need to do is have a play with WinISD pro. Put in the numbers. Put in filters. Keep adjusting until you get the -3 db point where you want it, say 120 Hz. Try the fc at say 60 Hz and see what you get. This all sounds so much more confusing when it is written down, but when you actually try it and see the charts, it's very simple.
hi
I emailed BK a pic of my winISD project to see if there BSBP 200/8 amp's had the filters i was using in my project ( Lowpass butterworth n=2 fc=40 and Highpass butterworth n=2 fc=7).
this is the info on the amp i got back
first email
The BSBP 200/8 has two low pass filters in series one is fixed at 140Hz at 12dB / Oct the other is variable from 40Hz to 120Hz at 12dB / Oct this filter can be bypassed.
On the low end the natural filter of the amplifier gives a -3dB at 5Hz
I think for any custom filtering you would need to run the amplifier with the filter bypassed and build in your own filters
second email
I modelled the Peerless driver in a 50 Litre enclosure and set the eq. to HP 5 hz single pole and low pass 40Hz 3 pole which would be more like what the panel would give set to 40hz and I have attached the image
so now i know that amp wont do the job unless i build my own filter can anyone point me in the right direction how to build a lowpass butterworth n=2 fc=40 filter or better still where i can buy one
thanks guys
I emailed BK a pic of my winISD project to see if there BSBP 200/8 amp's had the filters i was using in my project ( Lowpass butterworth n=2 fc=40 and Highpass butterworth n=2 fc=7).
this is the info on the amp i got back
first email
The BSBP 200/8 has two low pass filters in series one is fixed at 140Hz at 12dB / Oct the other is variable from 40Hz to 120Hz at 12dB / Oct this filter can be bypassed.
On the low end the natural filter of the amplifier gives a -3dB at 5Hz
I think for any custom filtering you would need to run the amplifier with the filter bypassed and build in your own filters
second email
I modelled the Peerless driver in a 50 Litre enclosure and set the eq. to HP 5 hz single pole and low pass 40Hz 3 pole which would be more like what the panel would give set to 40hz and I have attached the image
so now i know that amp wont do the job unless i build my own filter can anyone point me in the right direction how to build a lowpass butterworth n=2 fc=40 filter or better still where i can buy one
thanks guys
Attachments
ok thanks for the help its just when he modeled the responce he put down n=3 if you look at the attached image from my last post and when i use n=3 its not anywhere near as good as when i use n=2 for what i want
(just incase my post was not very clear the second email was from bk also)
thanks
(just incase my post was not very clear the second email was from bk also)
thanks
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