Ouch
No, but I do like the name! Nathan would be more appropriately called Summa - he that kind of kid. Has to be on top of everything.What do you think of this BMS driver
I suppose its kind of special having 1.5" throat, and only 1.75" voice coil
http://www.bmspro.info/Specification.4555_compression_technical_info.0.html
Or is it a misunderstanding because of the ringradiator diaphragm
They seem to have removed much of the previous information about their diaphragms
Now they just call it annular diaphragm design
I suppose its kind of special having 1.5" throat, and only 1.75" voice coil
http://www.bmspro.info/Specification.4555_compression_technical_info.0.html
Or is it a misunderstanding because of the ringradiator diaphragm
They seem to have removed much of the previous information about their diaphragms
Now they just call it annular diaphragm design
I know the B&C are good quality, I own a pair. And I know you get a good price on B&C. But to my question, you could modify your crossover and have a Selenium give the same frequency response and polar response at the B&C, right?
Conceptually yes. But what tends to happen with the lower grade of driver is more narrower bandwidth frequency response variations that take more components to correct or are too sharp and unstable to be correctable. With the B&C the responses are usually quite smooth, correctable and stable. Sometimes see variations above 10 kHz but seldom below.
Dr Geddes might give his comment of this " wisdom " :
http://www.goodsoundclub.com/TreeItem.aspx?PostID=11822
OK, I think I need to address the major subject of Mr. Haigner’s design – the CD or the constant directivity.
I have to admit that what I first saw he David’s horn I was taken by the elegance of the elliptical horn idea. Then looking deeper I understood that it was not a cool elliptical horn but David’s way to deal with the facts that CD horn can demonstrate constant directivity ONLY within one surface. The CD horn does the constant directivity trick in horizontal plane by killing directivity in vertical plane, so it is not “getting richer” but rather the redistribution of the wealth. There is however in this “redistribution of the wealth” some ugly moments that the “constant directivity” devotees fail to realize. Pay attention that I took the “constant directivity” in quote and it was not an accident. The constant directivity is just a marketing ** phrase, the very misleading one as there is not such a thing as constant directivity. There is a “slightly better directivity” and it is what it is. Let look in past.
The notion of constant directivity was injected into use by Electro-Voice in mid seventies. Whoever are interested find the Broadus Keele’s AES paper where he will-defined the rules of the game of CD concept.
http://www.xlrtechs.com/dbkeele.com/
The CD horn has is by nature a triple-bent horn where flare move from hyperbolic to exponential and then to conical profile. The whole idea is based upon the navigation of the edge diffraction around the bends. Sounds elegant, doesn’t it? Well, only on a paper and if the directivity was the ONLY concern that a loudspeaker has. The CD horn have very-very bad on axis equalization characteristic – try to get + 6db from CD horn and you will see. So, to get some equalization of juts the “horn gain” the CD horns shrink vertical dissipation and make itself narrow-rectangular. Sure, the narrowing the radiation angle helps to find a few dBs of horn gain but it makes the wavefront non-spherical – here is where the imaging goes… The pro audio folks hardly care about imaging as they never have it. Imaging is not a commodity of pro audio and they juts case to pass FCC (or whoever regulated them) limits by less expense. The CD horn was perfect for them and it allows spreading sound across wide area - with minimum efforts.
But the edge diffraction around bends of the CD horn are very tricky as they behave different at different db levels. Try to make 90 degree turn in your car driving 30 miles and 130 miles per hour. Feels different? Take a camera-obscura and observe the diffraction. Diffraction is a deviation of light in the region of geometrical shadows. The deviation of light in the region of geometrical shadows will have chromatic aberrations. It is because color of light raven with different speed and different speed had different diffraction power. The example with you, taking 90 degree turn in your car become very intuitive… Ironically the very same happened with CD horn – the diffractions around the profile’s bends are subject of pressure change and it makes the directivity horns to sound different at low and high sound levels. At low levels they lose the “more constant directivity” effect and at high levels they sound like overdriven direct radiator. A properly designed and used Tractrix driven with a proper SET in class A1 has very clean ability to raise dymick – it happens gracefully and very effortless. The horn juts does not care how much pressures it handles – if the horns driver and the amp can do it then the horns has no attitude about it. With CD horn, that has the broken up profile, the raise dymick is always accompanied with unproportionally-high elevation of distortions.
There is another thing that the CD horn enthusiasts do not mention. In horns there are no fantasizes - you have pressure and your have dissipation angle - you have one converted into other. Wider angle – less pressure and here is nothing you can do with it. In CD horn HF are tossed wider out of the horn and therefore the CD hoe loose HF much fasters then it shall. To combine the CD horn with a supplementary tweeter is not a good idea and the whole idea of CD horn is to put one *** on all chair and to have so called wide-bandwidth horns. If we have multiple channels then they would not suffer from any directivity “problems” and the CD horn would not be needed to begin with. So, how the CD horn enthusiasts deal with the problem of high frequency lost in CD horns? Well, they use one of two methods. The first method is to use VERY horribly hard-sounding drivers for the horns that have LOT of HF energy in them. The second method is to electronically equalize the CD horns driver with first order, almost writing the RIAA curve into the driver. ALL , with no exception, so-called constant directivity horns are driven by super-bright drivers (mostly in very cheap models) of equalized electronically….
Well, didn’t not you think that it all abs it too much price to pay for the opportunity to “listening together with your family and visitors” at the distance of one-two feet closer than you would do otherwise? Do not forget that the “constant directivity” idea was invented ONLY to get rigid of the multi-channel configuration and to make the horn installation cheaper. Cost - it was the ONLY a key as a properly made multi-channel has no narrow directivity disadvantage. So, I think in high-end audio, where we do surface cost and comfort for some result the we believe are worthy I think the CD Horns is not too much useful concept. I would be interested if David Haigner convert his CD Horns in elliptical horn of CONTINUES profile, get rid of his QE, use better drivers and add a few more channels. Well, he might end up with Macondo configurations then but does not know about it yet….
http://www.goodsoundclub.com/TreeItem.aspx?PostID=11822
OK, I think I need to address the major subject of Mr. Haigner’s design – the CD or the constant directivity.
I have to admit that what I first saw he David’s horn I was taken by the elegance of the elliptical horn idea. Then looking deeper I understood that it was not a cool elliptical horn but David’s way to deal with the facts that CD horn can demonstrate constant directivity ONLY within one surface. The CD horn does the constant directivity trick in horizontal plane by killing directivity in vertical plane, so it is not “getting richer” but rather the redistribution of the wealth. There is however in this “redistribution of the wealth” some ugly moments that the “constant directivity” devotees fail to realize. Pay attention that I took the “constant directivity” in quote and it was not an accident. The constant directivity is just a marketing ** phrase, the very misleading one as there is not such a thing as constant directivity. There is a “slightly better directivity” and it is what it is. Let look in past.
The notion of constant directivity was injected into use by Electro-Voice in mid seventies. Whoever are interested find the Broadus Keele’s AES paper where he will-defined the rules of the game of CD concept.
http://www.xlrtechs.com/dbkeele.com/
The CD horn has is by nature a triple-bent horn where flare move from hyperbolic to exponential and then to conical profile. The whole idea is based upon the navigation of the edge diffraction around the bends. Sounds elegant, doesn’t it? Well, only on a paper and if the directivity was the ONLY concern that a loudspeaker has. The CD horn have very-very bad on axis equalization characteristic – try to get + 6db from CD horn and you will see. So, to get some equalization of juts the “horn gain” the CD horns shrink vertical dissipation and make itself narrow-rectangular. Sure, the narrowing the radiation angle helps to find a few dBs of horn gain but it makes the wavefront non-spherical – here is where the imaging goes… The pro audio folks hardly care about imaging as they never have it. Imaging is not a commodity of pro audio and they juts case to pass FCC (or whoever regulated them) limits by less expense. The CD horn was perfect for them and it allows spreading sound across wide area - with minimum efforts.
But the edge diffraction around bends of the CD horn are very tricky as they behave different at different db levels. Try to make 90 degree turn in your car driving 30 miles and 130 miles per hour. Feels different? Take a camera-obscura and observe the diffraction. Diffraction is a deviation of light in the region of geometrical shadows. The deviation of light in the region of geometrical shadows will have chromatic aberrations. It is because color of light raven with different speed and different speed had different diffraction power. The example with you, taking 90 degree turn in your car become very intuitive… Ironically the very same happened with CD horn – the diffractions around the profile’s bends are subject of pressure change and it makes the directivity horns to sound different at low and high sound levels. At low levels they lose the “more constant directivity” effect and at high levels they sound like overdriven direct radiator. A properly designed and used Tractrix driven with a proper SET in class A1 has very clean ability to raise dymick – it happens gracefully and very effortless. The horn juts does not care how much pressures it handles – if the horns driver and the amp can do it then the horns has no attitude about it. With CD horn, that has the broken up profile, the raise dymick is always accompanied with unproportionally-high elevation of distortions.
There is another thing that the CD horn enthusiasts do not mention. In horns there are no fantasizes - you have pressure and your have dissipation angle - you have one converted into other. Wider angle – less pressure and here is nothing you can do with it. In CD horn HF are tossed wider out of the horn and therefore the CD hoe loose HF much fasters then it shall. To combine the CD horn with a supplementary tweeter is not a good idea and the whole idea of CD horn is to put one *** on all chair and to have so called wide-bandwidth horns. If we have multiple channels then they would not suffer from any directivity “problems” and the CD horn would not be needed to begin with. So, how the CD horn enthusiasts deal with the problem of high frequency lost in CD horns? Well, they use one of two methods. The first method is to use VERY horribly hard-sounding drivers for the horns that have LOT of HF energy in them. The second method is to electronically equalize the CD horns driver with first order, almost writing the RIAA curve into the driver. ALL , with no exception, so-called constant directivity horns are driven by super-bright drivers (mostly in very cheap models) of equalized electronically….
Well, didn’t not you think that it all abs it too much price to pay for the opportunity to “listening together with your family and visitors” at the distance of one-two feet closer than you would do otherwise? Do not forget that the “constant directivity” idea was invented ONLY to get rigid of the multi-channel configuration and to make the horn installation cheaper. Cost - it was the ONLY a key as a properly made multi-channel has no narrow directivity disadvantage. So, I think in high-end audio, where we do surface cost and comfort for some result the we believe are worthy I think the CD Horns is not too much useful concept. I would be interested if David Haigner convert his CD Horns in elliptical horn of CONTINUES profile, get rid of his QE, use better drivers and add a few more channels. Well, he might end up with Macondo configurations then but does not know about it yet….
Yes, they are very similar. Typically the difference has to do with application more than the technique to compute them. PCA is more about studying factors while SVD is about decomposing a matrix for various reasons. They about both based on the eigenvectors.
The point I would make is that the concept of constant directivity is not the same thing as the mechanism used to achieve it.
It is possible to achieve c.d. and minimise diffraction and higher mode production.
This is amply demonstrated in the data refered to and posted in these pages, for both compression drivers and dome radiators.
rcw.
It is possible to achieve c.d. and minimise diffraction and higher mode production.
This is amply demonstrated in the data refered to and posted in these pages, for both compression drivers and dome radiators.
rcw.
Wow! That is outrageous extension for a compression driver with a 1.5" throat. There aren't many 1" models with clean output about 15khz.* I'm using a BMS 4540ND in my car, and the only compression driver that equals it above 10khz is over $1000. I've measured it extensively and it has output beyond 20khz.
I really like the BMS ring radiators.
* yes, I know there are compression drivers that go to 20khz. The difference is that they get the output up high via diaphragm resonances, which sounds raspy to my ears
Earl - I was going back through the archives to find the photos of you and Duke from GPAF 2005. Wanted to post one on the HOM measurement thread. Thought I'd post here too, sort of memory lane.
I remember thinking the woofer and tweeter were about 20" apart, rough guess. Is that about right?
- Geddes and AudioKinesis at GPAF 2005
I'm going to bringing my Accord, with OS waveguides, horns and tapped horns, to the Audio Fest on Mercer Island tomorrow.
www.audiokarma.org/forums/showthread.php?p=3057229
If I can squeeze them into the car, I'll be bringing my Summas up too. Should be interesting. I've managed to cram them into my car before, but it's tricky...
Info on the car is here:
http://www.diyaudio.com/forums/showthread.php?threadid=148006
If anyone is in the area, would be great to discuss waveguides, horns, etc... Should be a fun show.
Actually I have not seen this for dome radiators, some simulations but no actual measurements of a real device.
The bottom line however is that there aren't different ways to achieve CD. You can easily do the inverse problem to calculate what is required from the source to achieve ideal CD in the far field and there aren't two solutions. There are different approximations that one can make that lead to slightly different configurations, but there are not that many options. Basically, I don't see how a dome can achieve CD in any configuration. I know you claim that it can be done using this or that technique, but stated quite simply, I haven't seen it practice yet. And until thats been done its all hypothetical.
Wouldn't this have to be true of all compression drivers? No diaphragm is going to 20 kHz and above with NO resonances. How well are they controlled is the issue. And I suspect that most of the problem above 10 kHz is acoustic - its very hard to get those frequencies out of the device. They tend to rattle arround inside - they don't want to come out to play. Thank goodness that they have so little effect on the total sound quality.
Because the BMS is a ring radiator, the peak is pushed above audibility in many of their compression drivers. My only experience is with the 4540ND - but I'm eager to try the other models. My Summas have the B&C, I've listened to Unity horns with Tad, and in my car I'm running BMS 4540ND.
Above 10khz, the BMS leaves the B&C in the dust, and gives the Tad a run for it's money.
Of course, below 2000hz, the B&C and the TAD eat the BMS alive, and below 2000hz is very important.
So it's a tradeoff of course. The BMS 4540ND has a delicacy and "airiness" in the top octave which reminds me of a ribbon tweeter.
This is a measurement that Brandon (augerpro) did of a B&C on an OS waveguide. You can see there's a peak at 16hz, which is the domes breakup, and then the output drops off a cliff.
My measurements of a BMS 4540ND on an OS waveguide. This is from my car. So the response is a lot more ragged than you'd get in an anechoic measurement. Nonetheless, there's no peak at all, and response continues beyond 20khz. If the peak is there, it's above 20khz.
TimG at audio heritage did this measurement of a 4540ND on an ENG1-90 waveguide, which is clearly inspired by an OS waveguide. Same results : extension beyond 20khz.
I've recently been running some sims on larger configurations. They get very CD without the on axis dip. I will show measurement data when the time is right. But I already have a pretty good feeling what is causing the on-axis dip in your designs.
I already KNOW what causes the dip and I've posted it here a number of times. Its the mouth diffraction which adds out of phase from the direct sound at precisely one frequency when precisely on axis. An elliptical mouth will make this go away.
We've been all through this before, where have you been?