Which type of tweeters best marry up to open baffles

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Bumpy

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What tweeter orientation is recommended to cover the higher frequencies of 3 way open baffles?

1) A dipole tweeter located adjacent to the midrange driver within the baffle.

2) A forward firing monopole on top of the baffle.

3) An upward firing monopole on top of the baffle.

4)  A combination of two monopoles on top of the baffle, one firing forward and the other rearward.

5) An omni-directional driver on top of the baffle.

Does anyone have an opinion on this?

I am not asking for recommended manufacturers.

matevana

Re: Which type of tweeters best marry up to open baffles
« Reply #1 on: 6 Nov 2018, 04:30 pm »
Where three-way designs are concerned, I've always been intrigued by the Wharfdale SFB. It uses a rear mounted, up-firing monopole tweeter.  It happens to be a very seamless integration.

Bumpy

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Re: Which type of tweeters best marry up to open baffles
« Reply #2 on: 6 Nov 2018, 04:45 pm »
Where three-way designs are concerned, I've always been intrigued by the Wharfdale SFB. It uses a rear mounted, up-firing monopole tweeter.  It happens to be a very seamless integration.

Yes, I've noted that too, and the SFB is a speaker with a cult status.  I could be wrong but I think that tweeter is a paper cone dipole :)




Tyson

Re: Which type of tweeters best marry up to open baffles
« Reply #3 on: 6 Nov 2018, 06:03 pm »
AMT with open back or Neo3 with open back both are great OB tweeters.

matevana

Re: Which type of tweeters best marry up to open baffles
« Reply #4 on: 6 Nov 2018, 06:47 pm »
Yes, I've noted that too, and the SFB is a speaker with a cult status.  I could be wrong but I think that tweeter is a paper cone dipole :)


Yes, you're right. It's not in a chamber so it's technically an up-firing dipole. I'd be tempted to try something like a Fostex FF85wk.   

Bumpy

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Re: Which type of tweeters best marry up to open baffles
« Reply #5 on: 6 Nov 2018, 10:28 pm »
Thanks for the recommendations, but for the moment I would like to concentrate solely on the location and tweeter type (monopole, dipole, omni directional etc)

Thanks

Bumpy

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Re: Which type of tweeters best marry up to open baffles
« Reply #6 on: 8 Nov 2018, 05:00 pm »
Interesting comments from Linkwitz Labs. They pretty much eschew the idea of rear facing tweeters or indeed dipole tweeters


Q25 - Why do you not use a rear firing tweeter or a dipole ribbon tweeter?

A25 - A rear firing tweeter for the PHOENIX would increase the speaker's high frequency 4p acoustic output by 3 dB for an even more uniform power response. In earlier designs I actually used such a tweeter. Because of the physical size and separation of the two tweeters - in terms of wavelength - it is impossible to obtain a simple cos(a) polar response. Instead, the off-axis response will consist of multiple beams, where the outputs of the two drivers see each other, which is primarily off-axis. On-axis, in front, the rear tweeter contributes very little to the sound. Overall I have not found a real benefit resulting from a rear tweeter. The off-axis response of the single tweeter-midrange combination is well behaved and actually has its widest dispersion around 4 kHz. Above that point the normal increase in tweeter directivity comes into play. Also, a rear tweeter may cause reflections from nearby objects which affects imaging and makes speaker placement critical. I am therefore using only a front tweeter.

A dipole ribbon tweeter would have the same potential problems as a rear tweeter. In addition the low 1440 Hz crossover requires large volume displacement capability. Typical high frequency ribbons would generate severe non-linear distortion under this condition.  A ribbon of greater length would narrow the vertical polar response too much. The large amount of air movement due to the close proximity of the 8" drivers might modulate the movement of the low mass ribbon and lead to further distortion. I have not used a ribbon driver, because the ones that I am aware of do not seem to fit this application.

WC

Re: Which type of tweeters best marry up to open baffles
« Reply #7 on: 8 Nov 2018, 05:19 pm »
Linkwitz must have changed his mind. The LX521 have front and rear facing tweeters.  :D
The LX-mini has a full range driver acting as a dipole with some of the backwave damped.

Bumpy

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Re: Which type of tweeters best marry up to open baffles
« Reply #8 on: 8 Nov 2018, 10:15 pm »
Its nice to see what they say backed up by measurement as well as listening.

ossidian

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Re: Which type of tweeters best marry up to open baffles
« Reply #9 on: 11 Nov 2018, 04:17 pm »
If one is using a large midrange driver I prefer the AMT, one gets 40khz down to 900hz (depending on model used).
The AMT 500 is rather large with a cultured marble baffle where as the AMT 700 and 900 models have a more scaled down baffle.
Hawthorne did make several AMT drivers that were fantastic. The AMT 500 is what I am currently listening to in my system.
Yes Hawthorne is currently out of business (Canadian company is taking them over soon) but the drivers can be found.