re tuba
By some calculations the Tuba is essentially a single ported bandpass box with some high end extension. A dedicated single ported bandpass box can be made about one quarter the size for the same bass output.
By some calculations the Tuba is essentially a single ported bandpass box with some high end extension. A dedicated single ported bandpass box can be made about one quarter the size for the same bass output.
Yes and No
THe assesment is correct untill you consider the horn bandwidth.
It would be difficult to get that response out of a bandpass without getting the "Sowbelly" response. A horn will roll off on the high end and the low end but the passband will usually behave.
MArk
THe assesment is correct untill you consider the horn bandwidth.
It would be difficult to get that response out of a bandpass without getting the "Sowbelly" response. A horn will roll off on the high end and the low end but the passband will usually behave.
MArk
re tuba
I am going by an AES paper written by Peter Fryer of B&W Bass.
This a result of research he did into "revese horns", to develop the nautilus loudspeaker.
He shows that if you take the usually ignored complex part of the impedance into account, then a horn system with a sealed rear chamber, over the range just above to below the horns cut off frequency, acts in a way identical to a single ported bandpass box.
By plugging in a few numbers you can show that a system with dimensions like the Tuba has a responce identical to a bandpass box over roughly the 70-140Hz. octave, and that a single ported bandpass box that has the same efficiency over this range is about one quarter of the size.
I am going by an AES paper written by Peter Fryer of B&W Bass.
This a result of research he did into "revese horns", to develop the nautilus loudspeaker.
He shows that if you take the usually ignored complex part of the impedance into account, then a horn system with a sealed rear chamber, over the range just above to below the horns cut off frequency, acts in a way identical to a single ported bandpass box.
By plugging in a few numbers you can show that a system with dimensions like the Tuba has a responce identical to a bandpass box over roughly the 70-140Hz. octave, and that a single ported bandpass box that has the same efficiency over this range is about one quarter of the size.
you have yet to define your single ported bandpass box.... give some chamber volumes and a front chamber tuning frequency and then what your saying might shed some light.
What about the 40-70hz region????
Bill shows in a graph on his website the measured in car response of a sealed box and the AutoTuba.... On average the sealed box is 10db less efficient. You dont gain 10db of efficiency compared to a sealed box over the entire bandwidth with a bandpass enclosure. Either those measurements are wrong, what you're saying is wrong, or your're talking about a 70hz tuned bandpass enclosure(which might be small, but would sound aweful).
What about the 40-70hz region????
Bill shows in a graph on his website the measured in car response of a sealed box and the AutoTuba.... On average the sealed box is 10db less efficient. You dont gain 10db of efficiency compared to a sealed box over the entire bandwidth with a bandpass enclosure. Either those measurements are wrong, what you're saying is wrong, or your're talking about a 70hz tuned bandpass enclosure(which might be small, but would sound aweful).
Read read and read some more!
I too have read a great many papers on the design and benefit of bandpass enclosures. THere are many types and some of them are covered by the B**E patent monster. THey perform a like function in that they try to better couple a naked driver to the air in a room. It does it well within a limited bandwidth. They have their own particular sound. I would characterise it as more subdued. Less bite a slam than a horn.
TO put some of this stuff into perspective. A horn works as an acoustical transformer. More effectively coupling to the air in the room than a bare driver. With this nice big box you get a greater efficiency and a limited bandwidth. But you get a greater bang for your amplifier buck. It to has it's own particular sound. SOme say it is a clean sound. More life like.
A band pass design trades off bandwidth for some gain in efficiency. It's bandwidth is generally less than a well designed horn.
As there is no free lunch. A bigger box or what ever may be needed. But in the end I think all of use are looking for some elusive thing called realisim. The feeling that you are there.
I've built and listened to all of the above. If I have the room a horn is #1. A well designed ported is #2. And a bandpass would be #3.
Just an opinion. Backed up with a lot of listening both live and recorded.
Mark
I too have read a great many papers on the design and benefit of bandpass enclosures. THere are many types and some of them are covered by the B**E patent monster. THey perform a like function in that they try to better couple a naked driver to the air in a room. It does it well within a limited bandwidth. They have their own particular sound. I would characterise it as more subdued. Less bite a slam than a horn.
TO put some of this stuff into perspective. A horn works as an acoustical transformer. More effectively coupling to the air in the room than a bare driver. With this nice big box you get a greater efficiency and a limited bandwidth. But you get a greater bang for your amplifier buck. It to has it's own particular sound. SOme say it is a clean sound. More life like.
A band pass design trades off bandwidth for some gain in efficiency. It's bandwidth is generally less than a well designed horn.
As there is no free lunch. A bigger box or what ever may be needed. But in the end I think all of use are looking for some elusive thing called realisim. The feeling that you are there.
I've built and listened to all of the above. If I have the room a horn is #1. A well designed ported is #2. And a bandpass would be #3.
Just an opinion. Backed up with a lot of listening both live and recorded.
Mark
re tuba
If you model a system similar to the Tuba in Win ISD, you find that the equivalent single ported bandpass box has an eerie similarity to the published curve for the Tuba, in the range below around 130Hz.
Putting the rear enclosure 10litres, the front 90litres, with the port the same area as the mouth of the Tuba, gives a single large peak of around 16db. this corresponds to the max. output of the Tuba.
Since the bandpass box is an exact analoge of this below around 130Hz. the output in the same test conditions, i.e. below this frequency can be expected to be fairly much the same.
This is using the Adire AV8 driver.
A box one quarter of the size has a rear chamber of 5litres, front of 23 litres tuned to 120Hz. the peak occurs at 117Hz. and is 10db. high, the output at low frequencies can be expected to be around 2-3db. less than the Tuba or its bandpass equivalent.
If you model a system similar to the Tuba in Win ISD, you find that the equivalent single ported bandpass box has an eerie similarity to the published curve for the Tuba, in the range below around 130Hz.
Putting the rear enclosure 10litres, the front 90litres, with the port the same area as the mouth of the Tuba, gives a single large peak of around 16db. this corresponds to the max. output of the Tuba.
Since the bandpass box is an exact analoge of this below around 130Hz. the output in the same test conditions, i.e. below this frequency can be expected to be fairly much the same.
This is using the Adire AV8 driver.
A box one quarter of the size has a rear chamber of 5litres, front of 23 litres tuned to 120Hz. the peak occurs at 117Hz. and is 10db. high, the output at low frequencies can be expected to be around 2-3db. less than the Tuba or its bandpass equivalent.
It seems to me there is probably quite a bit of gain in the 35-50hz region. A bandpass of that type wouldnt have that. I would take the driver out and put it in a bandpass like you say to compare... but alot of liquid nails is preventing that!
Trioth did some measurements and they're posted in a thread labeled "auto tuba measurements plus shiva"
I might do some measurements myself... Autotuba plus Tumult...
This is a for bass duty.... I really dont care what the response looks like above 100hz because it's not going to be used there!!!
Trioth did some measurements and they're posted in a thread labeled "auto tuba measurements plus shiva"
I might do some measurements myself... Autotuba plus Tumult...
This is a for bass duty.... I really dont care what the response looks like above 100hz because it's not going to be used there!!!
So what do you think you are going to do with this AutoTuba? At which point do you find you like the sound of the Tumult more on the top end?
I've been looking at the AutoTuba some more myself, and I wish I could get a pair of them in the corners in my room 🙁
I might have considered running them from 40 - 80 Hz with my existing subs stacked on top running down to 20 Hz ...
I've been looking at the AutoTuba some more myself, and I wish I could get a pair of them in the corners in my room 🙁
I might have considered running them from 40 - 80 Hz with my existing subs stacked on top running down to 20 Hz ...
above 100hz... I like the Tumult better. It rolls off much more and matches my mains better(extremis6.8 midwoofers that needless to say can go well below 100hz
The autotuba is just going to sit in my house until I find a suitable automotve amplifier for it. Then I'll either put it in my ride, or sell it to a freind for a "steal"
What's stopping you? Dont say price! The woodworking is a bit of a challenge(if you're as good as I am at it, or I should say as bad as I am) but it really doesnt take that long to complete. you could probably put 2 together in a single day if that was all you did all day.
The autotuba is just going to sit in my house until I find a suitable automotve amplifier for it. Then I'll either put it in my ride, or sell it to a freind for a "steal"
What's stopping you? Dont say price! The woodworking is a bit of a challenge(if you're as good as I am at it, or I should say as bad as I am) but it really doesnt take that long to complete. you could probably put 2 together in a single day if that was all you did all day.
Re: re tuba
rcw : Yes thats right,but the super peaky gain is not usable for music where as the Autotuba is.Certainly,the horn is a damped resonator,and with a tiny mouth its quite reactive,but its transient response must be relatively good still as people enjoy the sharp attack and lack of boom.
Its interesting seeing the same gain but over a tiny bandwidth from similar sized enclosures.
With modeling software you can really see the 'no free lunch' scenarios with ease.
Mike.e
rcw said:
rcw : Yes thats right,but the super peaky gain is not usable for music where as the Autotuba is.Certainly,the horn is a damped resonator,and with a tiny mouth its quite reactive,but its transient response must be relatively good still as people enjoy the sharp attack and lack of boom.
Its interesting seeing the same gain but over a tiny bandwidth from similar sized enclosures.
With modeling software you can really see the 'no free lunch' scenarios with ease.
Mike.e
re tuba
I was pointing out Mike that if you want a subwoofer , then you can get practically the same output in one, one quarter of the size.
The output of the tuba is extended in the upper bass region and a full three quarters of its volume is there to achieve this extension.
Given that the typical vehicle is said to have pressurisation gain below 70Hz.and crossing over the bandpass box at around 120Hz. I would be surprised if the low bass output was much different, and in a package one quarter the size.
I was pointing out Mike that if you want a subwoofer , then you can get practically the same output in one, one quarter of the size.
The output of the tuba is extended in the upper bass region and a full three quarters of its volume is there to achieve this extension.
Given that the typical vehicle is said to have pressurisation gain below 70Hz.and crossing over the bandpass box at around 120Hz. I would be surprised if the low bass output was much different, and in a package one quarter the size.
BA, I'd like to learn more about horns first. I also suspect that the Autotuba has compromises which could mean the top end may not improve on what I have now. I'd prefer to have a design which is my own, the learning curve is half the fun.
Mike, regarding the peaks I'm not so sure it's in fact the other way around. A bandpass if designed correctly, can be made relatively flat. The difficulty is that it is very sensitive to misalignment, if the parameters differ from those published. However, a bass horn that is significantly compromised will have a peaky response. I could be mistaken, but my impression is they are in fact a little less sensitive to misalignment. Common practice with bass horns seems to be that a different driver can sometimes be used, if parameters are similar. This is certainly not the case with a bandpass.
I was contemplating the idea of a bandpass using my AV12s to cover 20 - 40 Hz, however, the size to get decent performance down there, and the extreme sensitivity to misalignment has come close to putting me off. Although one nice feature of the 6th order bandpass I came up with was that I was able to achieve flat anechoic response down to 20 Hz with output well over 120db without using all the power I have available. As an added bonus, I was able to design it so that the F3 was below 20 Hz when the rumble filter is on, whereas normally it would reduce extension.
Mike, regarding the peaks I'm not so sure it's in fact the other way around. A bandpass if designed correctly, can be made relatively flat. The difficulty is that it is very sensitive to misalignment, if the parameters differ from those published. However, a bass horn that is significantly compromised will have a peaky response. I could be mistaken, but my impression is they are in fact a little less sensitive to misalignment. Common practice with bass horns seems to be that a different driver can sometimes be used, if parameters are similar. This is certainly not the case with a bandpass.
I was contemplating the idea of a bandpass using my AV12s to cover 20 - 40 Hz, however, the size to get decent performance down there, and the extreme sensitivity to misalignment has come close to putting me off. Although one nice feature of the 6th order bandpass I came up with was that I was able to achieve flat anechoic response down to 20 Hz with output well over 120db without using all the power I have available. As an added bonus, I was able to design it so that the F3 was below 20 Hz when the rumble filter is on, whereas normally it would reduce extension.
rcw : If you show me a small unit,with response that confers with what you say,while still being 'a quarter the size' and still sounding good,Il consider your viewpoint as having some merit.
I realise that most of the gain is above the crossover point and therefore unusable.
What you said earlier about getting an efficient bandpass system,that was a resonant and horrible sounding response.
Paul : A bandpass enclosure can well be made flat,but then the 'extra' sensitivity is lost ,defeating the whole purpose.
In the end most people in cars will use a high excursion ten or twelve inch unit to attain huge SPL on a sealed enclosure.
I realise that most of the gain is above the crossover point and therefore unusable.
What you said earlier about getting an efficient bandpass system,that was a resonant and horrible sounding response.
Paul : A bandpass enclosure can well be made flat,but then the 'extra' sensitivity is lost ,defeating the whole purpose.
In the end most people in cars will use a high excursion ten or twelve inch unit to attain huge SPL on a sealed enclosure.
re tuba
All you have to do Mike is to Put rear chamber volume 8 litres, front chamber 20litres, tuning frequency 100Hz. in WIN Isd for the AV8 driver, you can clearly see that with a peak increase in efficiency of 6db. this box has more output than the tuba down to 40Hz. and then the tuba beats it by around 1db. thereafter.
Any way you look at it this box at the subwwoofer frequencies assuming a crossover at around 120Hz. puts out a bit more bass in the subwoofer region and is one quarter the size.
The point is that since in this region the tuba is in fact a bandpass box, crossing it over at around 120Hz. should yeild a result that is the same in terms of sound, except for the fact that it is four times bigger. The evidence is there to see, and no amount of handwaving will change it.
All you have to do Mike is to Put rear chamber volume 8 litres, front chamber 20litres, tuning frequency 100Hz. in WIN Isd for the AV8 driver, you can clearly see that with a peak increase in efficiency of 6db. this box has more output than the tuba down to 40Hz. and then the tuba beats it by around 1db. thereafter.
Any way you look at it this box at the subwwoofer frequencies assuming a crossover at around 120Hz. puts out a bit more bass in the subwoofer region and is one quarter the size.
The point is that since in this region the tuba is in fact a bandpass box, crossing it over at around 120Hz. should yeild a result that is the same in terms of sound, except for the fact that it is four times bigger. The evidence is there to see, and no amount of handwaving will change it.
I largely agree with you now that I see what your saying.
Even so,
everyone hates the bandpass sound,and people enjoy the horn sound. This sound quality cant come at no price.
Your looking at the graphs but not considering the transient response trade offs. For SPL,yes the bandpass has its uses.
Even so,
everyone hates the bandpass sound,and people enjoy the horn sound. This sound quality cant come at no price.
Your looking at the graphs but not considering the transient response trade offs. For SPL,yes the bandpass has its uses.
I think we're comparing apples to oranges here....
The av8 and MCM are two differnet drivers.
I dont know how much the AV8 costs... but I'm thinking more than 32USD. I dont know how much power it handles either.
I can use a box 1/8 the size with an adire Tumult and linkwitz transform and get 10 times the output... also requires ALOT more power... and well alot more money also. Also sounds like junk because the Qtc would be like 1.5 or something insanely high
The av8 and MCM are two differnet drivers.
I dont know how much the AV8 costs... but I'm thinking more than 32USD. I dont know how much power it handles either.
I can use a box 1/8 the size with an adire Tumult and linkwitz transform and get 10 times the output... also requires ALOT more power... and well alot more money also. Also sounds like junk because the Qtc would be like 1.5 or something insanely high
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