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Multi-Way Conventional loudspeakers with crossovers

Driver spacing and crossover frequency
Driver spacing and crossover frequency
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Old 20th February 2019, 04:00 PM   #1
bcrazy is offline bcrazy  Norway
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Default Driver spacing and crossover frequency

Been reading Vance Dickason "Loudspeaker design cookbok"
Regarding driver spacing it is recommended to keep drivers as close as possible, and to make sure this distance is less than one wavelenght at the crossover frequency.

So typically for a 6,5 and tweeter 2-way, it is hard to get the drivers center to center much closer than about 5,25 inch, wich means crossover should be less than around 2600hZ.

However i have seen a few commercial, and diy speakers with 6,5" + tweeter with a crossover of 3000 Hz or higher.

Does this mean they are poorly comstructed from start, or is is possible to design a good sounding speaker with a crosseover frequency higher than one wavelength?
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Old 20th February 2019, 04:29 PM   #2
schiirrn is offline schiirrn  Germany
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You need to have a look why these recommendations are given and what happens if distances increase. Figure out the actuel length of a "wavelength" in centimeters. Check the distance of your ears. How many waves of what frequency fit between your ears and what does that mean?
It influences localisation. And influences lobing issues. Keep the drivers oriented in a vertical line, keep them close and cross where they need to be crossed to work in their optimum range and you'll be fine.
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Old 20th February 2019, 04:35 PM   #3
DPH is offline DPH  United States
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Everything is a compromise at the end of the day. While Vance is entirely correct, so do the best you can to shrink the spacing without losing your mind, then design your crossover accordingly.

Many >25mm tweeters can take a ~1800 Hz crossover point in domestic applications (unless you thrash your speakers), so not all is lost! Paradoxically, shallower crossovers in the overlap that steepen outside the region offer the greatest power handling because the first couple dB of attenuation matter the most.
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Old 20th February 2019, 05:17 PM   #4
bcrazy is offline bcrazy  Norway
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Quote:
Originally Posted by schiirrn View Post
You need to have a look why these recommendations are given and what happens if distances increase. Figure out the actuel length of a "wavelength" in centimeters. Check the distance of your ears. How many waves of what frequency fit between your ears and what does that mean?
It influences localisation. And influences lobing issues. Keep the drivers oriented in a vertical line, keep them close and cross where they need to be crossed to work in their optimum range and you'll be fine.
Ok, a particular speaker i am working on now with 6.5+1in tweeter seems to simulate best with a 4k crossover, so this may be better than try to push the crossover frequency down, as I can not make the response flat with with a 2.5k crossover, and also the tweeter reosnance is at 1800 hz.
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Old 20th February 2019, 06:03 PM   #5
schiirrn is offline schiirrn  Germany
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With the 4k crossover point you also moved it out of the "telephone range" which for some people is a good thing to do.
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Old 20th February 2019, 06:18 PM   #6
krivium is online now krivium  France
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Not really out of the inteligibility range as usually identified in pro audio field (usually it is considered 300hz/ 6khz) but you are closer to 4,5k where our brain/ear start to be less sensitive ( take a look at Fletcher Munson curves).
It may work or not... it'll depend of drivers, filter,... Are you sure you won't goes into trouble about mismatch of directivity between drivers ? (It is one of the reason to cross lower).
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Old 20th February 2019, 07:28 PM   #7
ctrlx is offline ctrlx  United Kingdom
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Originally Posted by DPH View Post
do the best you can to shrink the spacing without losing your mind.
choose a truncated driver and a tweeter with a rectangular flange

also you could cut out a section from a tweeters round flange....
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Old 20th February 2019, 07:29 PM   #8
planet10 is offline planet10  Canada
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Driver spacing and crossover frequency
Quote:
Originally Posted by bcrazy View Post
Regarding driver spacing it is recommended to keep drivers as close as possible, and to make sure this distance is less than one wavelenght at the crossover frequency.
Ideally the centre-to-centre distance of 2 drivers being crossed over should be such that the XO frequency is less than a quarter wavelength of that C-C.

The 1 wl DIckason uses is a compromise number chosen because his head is into cone + domes where unless you have a coax, the required close spacing is almost always impossible.

Much of the “art “ of speaker design is the set of compromises you choose.

dave
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Old 20th February 2019, 07:32 PM   #9
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by ctrlx View Post
choose a truncated driver and a tweeter with a rectangular flange

also you could cut out a section from a tweeters round flange....
I like perceval's idea WFW FAST with SBA racetrack woofers and SB65
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Old 20th February 2019, 07:37 PM   #10
DPH is offline DPH  United States
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Quote:
Originally Posted by ctrlx View Post
choose a truncated driver and a tweeter with a rectangular flange

also you could cut out a section from a tweeters round flange....
I think that's the part where I'd lose my mind.

To that end, we have a CNC mill at work and I have weekends access to screwing around with it, aka learning to use the thing better, which may well have me heavily modifying driver flanges to get C-C spacing as small as unreasonably possible. But do as I say and not as I do.

But I agree with your recommendations!
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