There's one in their ebay store. http://stores.ebay.com/Adire-Audio-Outlet_W0QQssPageNameZviQ3asibQ3astoreviewQQtZkm
re tuba
I don't know if they still make it bass, I just looked in the driver data base for the sort of thing people would use.
I don't know what particular mcm driver you are using, when I put them into my search engine they just come up as an electronic parts retailer.
The close resemblace between the tuba output and that of the roughly equivalent bandpass box indicates that the output with a similar driver will not be too much different.
I have not done an exact bandpass equivalent to the tuba because I don't know the rear chamber volume, but putting 10litres for it gives the correct peak output.
I don't know if they still make it bass, I just looked in the driver data base for the sort of thing people would use.
I don't know what particular mcm driver you are using, when I put them into my search engine they just come up as an electronic parts retailer.
The close resemblace between the tuba output and that of the roughly equivalent bandpass box indicates that the output with a similar driver will not be too much different.
I have not done an exact bandpass equivalent to the tuba because I don't know the rear chamber volume, but putting 10litres for it gives the correct peak output.
The MCM driver is viewable here....
http://mcm.newark.com/NewarkWebComm...SKU=55-2421&N=4
They dont publish any specs but judging it myself I'd say max excursion is about 1" p-p. Other parameters.... well those you cant really look and listen to tell very well. They say either 120wattsRMS or 140wattsRMS power handling. It's got a big beefy magnet on it and a top plate that is probably 1/4-3/8" thick so I'd assume BL is probably over 20T/m. Definately overhung
What I dont get is, yes you may be able to model an "equivilant" bandpass with the same gain up higher, but where is Bill getting this +10db average increase in efficiency vs sealed that he shows on the graph on his website??? Look at the graph below
15db gain at 20hz?????? Theres no way a 4th order bandpass tuned to 120hz is getting that! Something seems funny here.... I think Bill may be playing a little trick. He says measured where it counts, In car.... Well the sealed box has an ~18db/octave rolloff from 40 to 20hz, which wouldnt make any sense period. First off a sealed box only has 12db octave rolloff to begin with, and 2ndly the cabing gain of the car is supposed to add ~12db/octave below say 80hz
Looks like maybe Bill is showing a sealed box in full space, and a tuba in auto environment... hardly comparable.... It'd be nice if the man himself still posted here and could give some enlightenment. Maybe I'll email him and let him know of our discussion....
http://mcm.newark.com/NewarkWebComm...SKU=55-2421&N=4
They dont publish any specs but judging it myself I'd say max excursion is about 1" p-p. Other parameters.... well those you cant really look and listen to tell very well. They say either 120wattsRMS or 140wattsRMS power handling. It's got a big beefy magnet on it and a top plate that is probably 1/4-3/8" thick so I'd assume BL is probably over 20T/m. Definately overhung
What I dont get is, yes you may be able to model an "equivilant" bandpass with the same gain up higher, but where is Bill getting this +10db average increase in efficiency vs sealed that he shows on the graph on his website??? Look at the graph below
15db gain at 20hz?????? Theres no way a 4th order bandpass tuned to 120hz is getting that! Something seems funny here.... I think Bill may be playing a little trick. He says measured where it counts, In car.... Well the sealed box has an ~18db/octave rolloff from 40 to 20hz, which wouldnt make any sense period. First off a sealed box only has 12db octave rolloff to begin with, and 2ndly the cabing gain of the car is supposed to add ~12db/octave below say 80hz
Looks like maybe Bill is showing a sealed box in full space, and a tuba in auto environment... hardly comparable.... It'd be nice if the man himself still posted here and could give some enlightenment. Maybe I'll email him and let him know of our discussion....
Attachments
re tuba
I am not sure about the two curves myself.
My overall point is that if you take a sealed box with an ideal qt=.707 and a roll off at around 70-80Hz. then in a typical well sealed modern vehicle you should get nearly flat reponce below the lf roll off. If you feed such an enclosure with a 2nd. order low pass filter at 120Hz, as you would for a subwoofer, what you have done is in fact produced a responce that is equivalent to a fourth order bandpass box, but with 6db. less efficiency. With the same driver making the same excursions you need four times the power and four drivers if you use sealed boxes.
To my way of thinking the bandpass box wins hands down in all respects, it is probably smaller, definately cheaper, in a double blind test it would probably sound the same. Its major disadvantage for the young is that a one cubic foot box with a hole in it is no match for an array of shiney woofers and amplifiers when showing off down at the local strip, not to mention retailers who only get to sell you one quarter of the goods they otherwise would.
I am not sure about the two curves myself.
My overall point is that if you take a sealed box with an ideal qt=.707 and a roll off at around 70-80Hz. then in a typical well sealed modern vehicle you should get nearly flat reponce below the lf roll off. If you feed such an enclosure with a 2nd. order low pass filter at 120Hz, as you would for a subwoofer, what you have done is in fact produced a responce that is equivalent to a fourth order bandpass box, but with 6db. less efficiency. With the same driver making the same excursions you need four times the power and four drivers if you use sealed boxes.
To my way of thinking the bandpass box wins hands down in all respects, it is probably smaller, definately cheaper, in a double blind test it would probably sound the same. Its major disadvantage for the young is that a one cubic foot box with a hole in it is no match for an array of shiney woofers and amplifiers when showing off down at the local strip, not to mention retailers who only get to sell you one quarter of the goods they otherwise would.
Re: re tuba
All apart from the appalling Group Delay from most BP boxes. I can certainly hear it, but I doubt the average buyer who just wants lots of one note bass in the back of his car would care.
rcw said:
All apart from the appalling Group Delay from most BP boxes. I can certainly hear it, but I doubt the average buyer who just wants lots of one note bass in the back of his car would care.
re tuba
Moderator or no, I doubt if I have read a more a monumentally stupid remark in a long time.
If the described system will produce '"one note " bass then all systems of the equivalent bandwidth will also produce one note bass, despite the method of loading. Whats more all systems with the same transfer function, (despite if that transfer function is achieved by electronic or acoustic means), will have the same group delay since the system is the minimum phase sort.
Moderator or no, I doubt if I have read a more a monumentally stupid remark in a long time.
If the described system will produce '"one note " bass then all systems of the equivalent bandwidth will also produce one note bass, despite the method of loading. Whats more all systems with the same transfer function, (despite if that transfer function is achieved by electronic or acoustic means), will have the same group delay since the system is the minimum phase sort.
rcw, if you had posted that comment about any other member then you would be in the sinbin now. We do not tolerate personal insults on this board against anyone. This is your last warning.
Regarding the SPL graph....
Ripped off from the site. The graph illustrates the difference between the driver horn loaded and in a sealed enclosure. The overall 10db gain is the plus you get with using a horn. As in a bandpass the overall limited passband of a horn yields an efficiency in the coupling of the diaphrams motion to the air in the room. More or less a gain like that found in a stepup transformer. The no free lunch part is that the horn or bandpass enclosure can only support this gain over a limited bandwidth.
The gain in the low end is just what you think. Cabin gain. Cool when you think about it. An almost free lunch!
Mark
Ripped off from the site. The graph illustrates the difference between the driver horn loaded and in a sealed enclosure. The overall 10db gain is the plus you get with using a horn. As in a bandpass the overall limited passband of a horn yields an efficiency in the coupling of the diaphrams motion to the air in the room. More or less a gain like that found in a stepup transformer. The no free lunch part is that the horn or bandpass enclosure can only support this gain over a limited bandwidth.
The gain in the low end is just what you think. Cabin gain. Cool when you think about it. An almost free lunch!
Mark
mwmkravchenko,
Yes the graph was ripped off of the site... I took it from there so people who were too lazy to actually visit the site could see it.
My point is about the graph that it is improper to compare a sealed box to a horn loaded box if they arent measured in the same place.
Yes the graph was ripped off of the site... I took it from there so people who were too lazy to actually visit the site could see it.
My point is about the graph that it is improper to compare a sealed box to a horn loaded box if they arent measured in the same place.
I think he was banned, so you probably won't get a reply in this thread. He's pretty good about replying to direct emails.
ahh that would explain why he hasnt posted since february or so....
I wonder why bill was banned.... It doesnt seem that hard to me to not say rule offending things in these threads... I have yet to be sin binned or recieved any warnings etc... that I am aware of.
I think everyone can get along...
Sockpuppeting
To use another ID than your own.
For example if I were to make posts under the name Johny Dont to shill for myself, provide strawmen for my real ID, and talk about your mothers complete lack of hygene and moral standards, that would be sock puppeting.
To use another ID than your own.
For example if I were to make posts under the name Johny Dont to shill for myself, provide strawmen for my real ID, and talk about your mothers complete lack of hygene and moral standards, that would be sock puppeting.
Just look at post #34 and the posts following to understand...
http://www.diyaudio.com/forums/showthread.php?postid=575415#post575415
http://www.diyaudio.com/forums/showthread.php?postid=575415#post575415
I get it... That is what I suspected, but wasnt quite sure....
Seems kinda silly... Isnt your IP addy available by the webmaster? I guess another computer could always be used, but that'd be alot of work just to badmouth on DIYaudio.....
Seems kinda silly... Isnt your IP addy available by the webmaster? I guess another computer could always be used, but that'd be alot of work just to badmouth on DIYaudio.....
Re: re tuba
Feel free to double blind test - I havent see results of one, neither for or against.
I dont disagree with the physics - What I disagree on is the designers INTENT when looking at bandpass boxes. How often do you see a bandpass enclosure that is wide bandwidth,and really the same response as a ported enclosure, but with just the extra tuning point(BP6 i mean)
The graphs are abit sus, theres no real point in posting graphs made by oneself on a site where your selling a product - Id get independant testing for credibility. No doubt many fitz plans buyers are happy with their result.
The normal/popular route is to make it boomy and loud,a kind of abuse of the scheme.
rcw said:
Feel free to double blind test - I havent see results of one, neither for or against.
I dont disagree with the physics - What I disagree on is the designers INTENT when looking at bandpass boxes. How often do you see a bandpass enclosure that is wide bandwidth,and really the same response as a ported enclosure, but with just the extra tuning point(BP6 i mean)
The graphs are abit sus, theres no real point in posting graphs made by oneself on a site where your selling a product - Id get independant testing for credibility. No doubt many fitz plans buyers are happy with their result.
The normal/popular route is to make it boomy and loud,a kind of abuse of the scheme.
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