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Multi-Way Conventional loudspeakers with crossovers

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Old 15th April 2008, 10:16 PM   #3371
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Quote:
Originally posted by Magnetar


Why would you recommend crossing a narrow radiation ( ihave plenty of Altec 15 curvalinear cones here - they work best no higher than 1.2K with a wide radiation horn) 15" driver to a wide radiation ribbon tweeter? To me that would be a disaster. IE I found a 6" driver to be much more appropriate with a ribbon.., even when use a big ribbon as low as 1K with a 8th order network a ten inch was pushing it.

There are several things to look at and always tradeoffs. The radiation pattern is one issue, low distortion at higher SPL is another. First you need to determine the range you are covering both in frequency and the radiation pattern. If you are looking to cover only a short midrange band, then the 6" driver could be fine if SPL requirements are not too high. However if you are essentially looking to cover a large range, say from 50Hz up to the xover point, the 6" driver will just not be able to do this well at any reasonable SPL's. You will be severely limited in output with only the 6" driver and will have to deal with much higher distortions. This means you would then need a 3way system leading to more complexity in the design, more cost, etc.

The other tradeoff is to deal with the more narrow radiation pattern on the woofer that can provide these SPL's at low distortion. You would have approximately a 60degree pattern at 2KHz with the 15" TD drivers. For most applications I actually like to have a more narrow radiation pattern to minimize room interaction. It all depends on what your goals are though. If your goal is for very wide horizontal dispersion, an array of multiple smaller drivers would likely be an option, but then you would have the limited vertical dispersion and other issues with an array.

As far as the Altec drivers go, there is no way to do a direct comparison simply if they use the same profile on the cone. None of the altec drivers that I am aware of take advantage of a full copper sleeve to lower inductance. They are not close to electrically flat to the 5KHz range. Nor do they have the large phase plug which also greatly increases the usable frequency range both on and off axis.

John
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Old 15th April 2008, 10:24 PM   #3372
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Quote:
Originally posted by John_E_Janowitz



There are several things to look at and always tradeoffs. The radiation pattern is one issue, low distortion at higher SPL is another. First you need to determine the range you are covering both in frequency and the radiation pattern. If you are looking to cover only a short midrange band, then the 6" driver could be fine if SPL requirements are not too high. However if you are essentially looking to cover a large range, say from 50Hz up to the xover point, the 6" driver will just not be able to do this well at any reasonable SPL's. You will be severely limited in output with only the 6" driver and will have to deal with much higher distortions. This means you would then need a 3way system leading to more complexity in the design, more cost, etc.

The other tradeoff is to deal with the more narrow radiation pattern on the woofer that can provide these SPL's at low distortion. You would have approximately a 60degree pattern at 2KHz with the 15" TD drivers. For most applications I actually like to have a more narrow radiation pattern to minimize room interaction. It all depends on what your goals are though. If your goal is for very wide horizontal dispersion, an array of multiple smaller drivers would likely be an option, but then you would have the limited vertical dispersion and other issues with an array.

As far as the Altec drivers go, there is no way to do a direct comparison simply if they use the same profile on the cone. None of the altec drivers that I am aware of take advantage of a full copper sleeve to lower inductance. They are not close to electrically flat to the 5KHz range. Nor do they have the large phase plug which also greatly increases the usable frequency range both on and off axis.

John
You didn't answer my question, maybe because you fail to realize the rediation of the rall ribbon at 2k?
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Old 15th April 2008, 10:36 PM   #3373
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Quote:
Originally posted by Magnetar


You didn't answer my question, maybe because you fail to realize the rediation of the rall ribbon at 2k?
Well looking at the horizontal dispersion spl vs frequency I see nothing past 60degree on the chart. I don't have more info than that so all i can guess is that it drops slightly at 140 vs 120 degrees. I also realize that the TD15M would be only at 60 degrees. This does not mean that things completely disappear after 60degrees. You would likely have a dip in the power response the farther you go off axis. This may or may not be an issue depending on your listening position, position of speakers in room, and the room itself. If a smooth power response is your only goal, then this would not likely be the combination for you. If you can live with some differences in power response and are looking for high SPL with low distortion, it has some promise.

John
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Old 15th April 2008, 10:53 PM   #3374
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Quote:
Originally posted by John_E_Janowitz


Well looking at the horizontal dispersion spl vs frequency I see nothing past 60degree on the chart. I don't have more info than that so all i can guess is that it drops slightly at 140 vs 120 degrees. I also realize that the TD15M would be only at 60 degrees. This does not mean that things completely disappear after 60degrees. You would likely have a dip in the power response the farther you go off axis. This may or may not be an issue depending on your listening position, position of speakers in room, and the room itself. If a smooth power response is your only goal, then this would not likely be the combination for you. If you can live with some differences in power response and are looking for high SPL with low distortion, it has some promise.

John

I wouldn't use a ribbon (I'd use a horn that would mate with it) at all, but if I did use the rall it would be mated with an appropriate driver. not a 15 - If I was concerned about SPL I would not use a ribbon but a horn, and I don't think a single 15 (any!) on an open baffle would 'cut it' IE - keep up with a good horn with 'low distortion'

The rall driver is only 3-4 db down at 15K at 60 degrees after the foam band aid is applied.
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Old 16th April 2008, 12:02 AM   #3375
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Quote:
Originally posted by Magnetar


You didn't answer my question, maybe because you fail to realize the rediation of the rall ribbon at 2k?

John is being very cordial and helpful. Please don't be rude.
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Old 16th April 2008, 12:24 AM   #3376
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Default thank you for your post edit ...

I only see a civil disagreement so far. We cannot like everybody and not everyone will like us so to discuss openly like this is good. Differing opinion is useful.
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Old 16th April 2008, 12:25 AM   #3377
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Quote:
Originally posted by augerpro



John is being very cordial and helpful. Please don't be rude.
What?

You HAVE TO BE KIDDING!

I suppose you use one of his 15's on an open baffle crossed over to a little ribbon?
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Old 16th April 2008, 01:17 AM   #3378
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Default There were a boat load...

of speaker designs over the decades that used a small tweeter (one inch dome to 3 inch cone) crossed over to 10 - 12 inch drivers. I always shook my head but the popularity was and still is astounding.
What about the trick of extending a ribbon to match the ribbon's vertical dimension (and polar pattern) to that of the bass driver. What happens at crossover in this situation as far as dispertion of the two drivers? Have good fudge jobs been done this way?
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Old 16th April 2008, 01:44 AM   #3379
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Quote:
Originally posted by Magnetar


What?

You HAVE TO BE KIDDING!

I suppose you use one of his 15's on an open baffle crossed over to a little ribbon?
I just stumbled onto John's creations a week ago, so no...

I don't mean to start a fight and maybe I overreacted, but very often the helpful experience you have is overshadowed by the somewhat condescending and rude manner...and the debate tends to go to hell after that. I hope you take that as a constructive observation.

I'm going to butt out now so we don't derail this thread.
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Old 16th April 2008, 02:10 AM   #3380
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Default Earl Geddes

does it with a 15" and a compression driver.....and so does JBL.....and TAD.....and (insert professional monitor company here).

It may not be a ribbon, but the idea is what your design goals are for a system....not when one starts to beam, or how low it will go. I have heard that tweeter crossed quite low in a PA style 2-way at HIGH volumes and it is IMPRESSIVE.

Best,

C

p.s. This is Lynn's thread. Can everyone (including me) play nice in his sandbox? The mod's are on it around here when things get out of line.
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