Pros:
More tradeoff flexibility
inherent filtration of distortion products
Cons:
More complex to build and design.
port resonances can be a problem
Go to www.diysubwoofers.org and read a bit about them.
More tradeoff flexibility
inherent filtration of distortion products
Cons:
More complex to build and design.
port resonances can be a problem
Go to www.diysubwoofers.org and read a bit about them.
There are no pros and cons as far as the enclosure itype is concerned, just whether it's what you need. If your necessity is for an enclosure that trades off wide bandwidth for a higher level of performance with a narrow bandwidth you use a bandpass box. That usually means that the application is a subwoofer. If you require a wide bandwidth for the application then a bandpass box won't work. Simple as that.
IMO the higher the order, the more complexity, more chance for error, and smaller and smaller bandpass but at increased output.
I'm trying to repair my buddy's Acoustimass 5, looks like water got on the amp. Anyway, while trying to repair the amp I hooked up the sub for some listening and for anyone whoever said bose's bandpass enclosures are good for only one note were right. It doesn't matter what you're listening to it all sounds the like the same drum same bass guitar etc...
But it does play that one note very loud for such a small enclosure.
I'm trying to repair my buddy's Acoustimass 5, looks like water got on the amp. Anyway, while trying to repair the amp I hooked up the sub for some listening and for anyone whoever said bose's bandpass enclosures are good for only one note were right. It doesn't matter what you're listening to it all sounds the like the same drum same bass guitar etc...
But it does play that one note very loud for such a small enclosure.
Ive never built a bandpass enclosure for the very reason of sound quality issues.. a ported box is resonant enough...
From all the sound books ive read,no one reccomends them for Nice quality bass..just honk..but some people MAY want honk!
You can design them to be wider bandwidth,but then the whole point of more 'efficient' bass is lost...
😎
From all the sound books ive read,no one reccomends them for Nice quality bass..just honk..but some people MAY want honk!
You can design them to be wider bandwidth,but then the whole point of more 'efficient' bass is lost...
😎
Member
Joined 2002
I tell this story al the time. but Id build another bandpass again if i could.. I had 2 subs in the same room was was a 800$ subwoofer a USD 15" sub with about 1500 watts. the other was a used kicker 10" sub the cheapest one they made. i build 2 boxes one for each.. the 15" was a ported 4ltr box witch was pretty loud but then i had the kicker c10 in a bandpass box.. and the one that one and was cleanest.. was the bandpass and it took very little effort to get bass too.. really efficient box.. So next time i want another cheap easy sub to build it will be a bandpass.
I've used bandpass enclosures with good success in car audio (both for sound Q and boom) infact with some cars bandpass is the only practical option.
With a normal reflex box you could tune it so it really pumps at 20Hz and will handle full power down there, but up at 30Hz it will run out of excursion because it is starting to behave like a closed box as the air in the port is not moving very much at this frequency like it was at 20Hz. (At 40Hz it would probably be ok again).
With a bandpass box you can have the smaller chamber tuned to 40Hz so that it comes to the rescue and by time *it* starts to behave like a closed box, cone excursion is not an issue. Anyway, the whole box has rolled off it's output at this point. In a nutshell, you can have a tight grip on cone excursion over a wider range of frequencies.
My very rough starting point for a 2-chamber 2-port 6th order bandpass is what I call the 1:2:4 method -> port ratio = 1:1, tuning frequency = 2:1, chamber volume ratio = 4:1.
In actual fact I am very interested in putting a bulkhead inside both of my subs to divide the volume into 200L/50L tuned to 20Hz/40Hz with an active filter to make the cheap junk 12" drivers sit up and take notice.
Will definitely report on it when it is done.
BTW, many people say that a 6th order bandpass box has worse transient response than a normal reflex box. How is this since the sound is coming out of one box-and-port or the other, not both in series? Sure there is six reactive elements, but in a way only four ever get used at one time.
With a bandpass box you can have the smaller chamber tuned to 40Hz so that it comes to the rescue and by time *it* starts to behave like a closed box, cone excursion is not an issue. Anyway, the whole box has rolled off it's output at this point. In a nutshell, you can have a tight grip on cone excursion over a wider range of frequencies.
My very rough starting point for a 2-chamber 2-port 6th order bandpass is what I call the 1:2:4 method -> port ratio = 1:1, tuning frequency = 2:1, chamber volume ratio = 4:1.
In actual fact I am very interested in putting a bulkhead inside both of my subs to divide the volume into 200L/50L tuned to 20Hz/40Hz with an active filter to make the cheap junk 12" drivers sit up and take notice.
Will definitely report on it when it is done. BTW, many people say that a 6th order bandpass box has worse transient response than a normal reflex box. How is this since the sound is coming out of one box-and-port or the other, not both in series? Sure there is six reactive elements, but in a way only four ever get used at one time.
One note bass is normal
The fact that the drums/bass etc all sounded the same through a bandpass sub is normal. One thing a bandpass will allow is for you to hear fundamental tones without any harmonic content, and when you do so you find that a 40 Hz tone, for instance, sounds for all intents and purposes the same regardless of the source, be it electric bass, keyboard, kettle drum or bassoon. It is the harmonics that define the true sound of any instrument, not the fundamentals.
The fact that the drums/bass etc all sounded the same through a bandpass sub is normal. One thing a bandpass will allow is for you to hear fundamental tones without any harmonic content, and when you do so you find that a 40 Hz tone, for instance, sounds for all intents and purposes the same regardless of the source, be it electric bass, keyboard, kettle drum or bassoon. It is the harmonics that define the true sound of any instrument, not the fundamentals.
mikee12345 said:
KEF used 4th order bandpass in their flagship loudspeaker and it sounded fine. Bandpass gets a bad rap 'cause people buy ready made bandpass boxes and put any old woofer in there that looks cool through the plexiglass.
Circlotron said:
4th order BP boxes have an excursion maximum near the lower F3 point and this can be a problem in some cases, although they protect the driver below that because of the sealed chamber. Their transient response is no worse than a sealed box with similar rolloff characteristics and a lowpass filter at the high frequency rolloff point.
6th order BP boxes are producing sound from both ports continuously. Their transient response is no worse than a 4th order Bass reflex with similar Low frequency rolloff characteristics and a lowpass filter at the high frequency rolloff point. They have excursion minimums near each end of the response curve and they do not protect the driver below the lower resonance, similar to a vented box....
qi said:
Bose no longer has a patent on the design - everyone will soon be making BP subs - so Bose is on to the next big thing so they can be claimed as a "research" company......
This is a picture of a 50Hz tone burst with 24dB per octave LPF starting at 50Hz. The transient response is indeed degraded.Ron E said:
So, would it be right to conclude that a closed box speaker has a better transient response mainly because the cone is still exposed therefore it has a more extended frequency response than a system that has all the sound coming from the port(s)?
Attachments
Perhaps an example would be more illustrative.
Say you have a 4th order bandpass with a -3dB bandwidth of 40-100Hz. You also have a sealed box with F3=40Hz and Qtc-0.707.
Say that you have designed the BP box so that its LF rolloff behavior is essentially the same as the sealed box.
Now take that 40Hz sealed box and filter it with a 2nd order lowpass filter at 100Hz. When you compare tone bursts, step response, or what have you, the two systems will be essentially equivalent.
When comparing transient response, you must be aware of the bandwidth of the device. It is not a fair comparison to compare a sealed box with no LP filter to a 4th order bandpass box. The sealed box will always look better, even though it is not. This is not to say that 4th Order bandpass boxes cannot be misaligned or that they always have similar transient response to sealed boxes, because you can trade off box size for ripple in the BP box and the more ripple, the worse the transient response gets....
Say you have a 4th order bandpass with a -3dB bandwidth of 40-100Hz. You also have a sealed box with F3=40Hz and Qtc-0.707.
Say that you have designed the BP box so that its LF rolloff behavior is essentially the same as the sealed box.
Now take that 40Hz sealed box and filter it with a 2nd order lowpass filter at 100Hz. When you compare tone bursts, step response, or what have you, the two systems will be essentially equivalent.
When comparing transient response, you must be aware of the bandwidth of the device. It is not a fair comparison to compare a sealed box with no LP filter to a 4th order bandpass box. The sealed box will always look better, even though it is not. This is not to say that 4th Order bandpass boxes cannot be misaligned or that they always have similar transient response to sealed boxes, because you can trade off box size for ripple in the BP box and the more ripple, the worse the transient response gets....
- Status
- Not open for further replies.