I'm building a pair of 2-ways with Fountek NeoCD2.0 tweeters and am not sure if I should place them centered or off center on the baffle board. Baffle board is 10.5 inches wide. Cabinet is 11.5 inches wide.
Concerned about minimizing diffraction issues.
Advice?
Concerned about minimizing diffraction issues.
Advice?
There are good arguments fore mounting off centre
But seem there are some issues as well
Look at what usually happens
Speaker listening setup is usually with the narrow part of front baffle towards the middle/listener
And why is that
One would ideally expect it the other way round, to have better phase allignment to midwoofer, having tweeter further away
Well, I suppose its probably due to the narrow side of baffle having less reflection issues
Off center placement could seem like a winn and loose game
I would rather think of a way to move the tweeter backwards to get better phase allignment with midwoofer
A shallow waveguide seems like the perfect solution to all of it
Or maybe mount it in its own curved baffle, placed on top of woofer box
Or a combination of both
But seem there are some issues as well
Look at what usually happens
Speaker listening setup is usually with the narrow part of front baffle towards the middle/listener
And why is that
One would ideally expect it the other way round, to have better phase allignment to midwoofer, having tweeter further away
Well, I suppose its probably due to the narrow side of baffle having less reflection issues
Off center placement could seem like a winn and loose game
I would rather think of a way to move the tweeter backwards to get better phase allignment with midwoofer
A shallow waveguide seems like the perfect solution to all of it
Or maybe mount it in its own curved baffle, placed on top of woofer box
Or a combination of both
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I tend to mount tweeters off centre (if i mount them on a baffle).
Edge can be used to simulate diffraction.
dave
Edge can be used to simulate diffraction.
dave
I had read that ribbon tweeter's project sound differently than dome tweeters and that they are less prone to causing diffraction problems. Hence the reason for my original post.
True or false?
True or false?
Of axis response is different from the dome tweeters. Neo 2 for example has a good horizontal dispersion but vertical of axis is horrendous. As a wide generalization, they are more directional which can be beneficial or a hazard to the outcome.
Yeah, I was aware of that. However, I thought the wide horiz. dispersion characteristics of ribbons would be considered less directional?
But it still doesn't answer the question regarding diffraction issues from domes vs ribbons and whether or not to offset the ribbons on the BB's.....🙁
Answers are there, and how to do it, but maybe we just dont agree
If you study it you will see that most try to avoid wide baffles around tweeters
Waveguides, curved baffle, cut aways are just a practical way of dealing with a wide flat baffle
My guess is that you can treat ribbons with similar of axis response to the domes similarly. Long ribbons like Neo 2.0 do not need side offsetting and before you even get to diffraction there are other issues that are critical for ribbons and their crossover points, distortions and lobbing at the crossover F.
I don't think you going to find your answer here without doing sample baffles and a multitude of measurements.
The other thing you could do is upholster front baffle in decorative fabric. Ultrasuede looks good.
I don't think you going to find your answer here without doing sample baffles and a multitude of measurements.
The other thing you could do is upholster front baffle in decorative fabric. Ultrasuede looks good.
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Thanks folks for your responses. The baffles are already built. I've given the dimemsions previously. In fact, the cabinets exist. I'm just modding them to accept the ribbons.
With regard to the xover, I realize I'm faced with a challenge. I'm planning on a 3rd order at 2Khz for the ribbon and 1st order for the woofer (HiVi F8).
With regard to the xover, I realize I'm faced with a challenge. I'm planning on a 3rd order at 2Khz for the ribbon and 1st order for the woofer (HiVi F8).
I'm waiting for the woofer to arrive and I'll run an impedance curve on it. I was going to decide then if a zibel was needed or not. I take you've already come to that conclusion for that driver?
if you are planing 2khz for neo 2.0 even with a 3rd order it's a recipe for disaster. first of all neo will distort that low, secondly you will run in to low impedance issues with it. I would think 3200hz is the minimum x-over F. I don't mean to butt in your design process but I've had my own eye opener about ribbons a while ago.
Here's a link to a site with some neat theo. modeling of dome vs ribbon directivity and lobing patterns FYI,
http://phy6.net/audio/papers/ribbon_wavefront_patterns/HP001.Wavefronts.htm
http://phy6.net/audio/papers/ribbon_wavefront_patterns/HP001.Wavefronts.htm
Unfortunately Carpenter is right about one drawback of ribbons, the need fore higher xo point
I forgot that issue
Regarding zobel on woofer
Its needed on all
Its just a matter of the values needed
And, any paralel component might be used just to adjust phase
You need to realise that 6db doesnt really exist in real life
Well, might be possible with a wide range driver
Modern xo design is based on how response looks on the acoustic side
Which means you have to consider a drivers own natural roll off
Older books may suggest to use 6db/18db
But in reality they never knew what was actually happening
Its very common to use 12db/18db with no tweeter offset
But in reality its probably 24db/24db on the acoustic side, or as close as you can get
Though it is possible to fiddle with component values to obtain other slopes, like say 10db
Or maybe softer slopes that starts out as 12db and ends with 24db, or more
I forgot that issue
Regarding zobel on woofer
Its needed on all
Its just a matter of the values needed
And, any paralel component might be used just to adjust phase
You need to realise that 6db doesnt really exist in real life
Well, might be possible with a wide range driver
Modern xo design is based on how response looks on the acoustic side
Which means you have to consider a drivers own natural roll off
Older books may suggest to use 6db/18db
But in reality they never knew what was actually happening
Its very common to use 12db/18db with no tweeter offset
But in reality its probably 24db/24db on the acoustic side, or as close as you can get
Though it is possible to fiddle with component values to obtain other slopes, like say 10db
Or maybe softer slopes that starts out as 12db and ends with 24db, or more
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The Neo 2.0 specs recommend 2500 hz xover. They don't mention order. The ribbon supplier says 2nd order at 2 khz is okay. So, I plan on 3rd to be safe. I may end up going up to 2.2. kHz, the upper recommended freq. for the F8.
All this is contingent on the actual drivers I get and thoroughly test. We can speculate, but the bottom line is what I have in hand to work with. I'll know the answer in about 1 week after I've had a chance to evaluate the drivers.
All this is contingent on the actual drivers I get and thoroughly test. We can speculate, but the bottom line is what I have in hand to work with. I'll know the answer in about 1 week after I've had a chance to evaluate the drivers.
I may actually have MRD files if I didn't delete them. I've been playing with Neo 2.0 for 4 month now and it's a excellent tweeter if used with it's limitations in mind. Usually then the crossover is recommended by manufacturer, it's a second order crossover.
Measure tweeter's distortions and see what your ear can tolerate.
Measure tweeter's distortions and see what your ear can tolerate.
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