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Multi-Way Conventional loudspeakers with crossovers

Mid tweeters-too easy?
Mid tweeters-too easy?
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Old 21st September 2018, 06:03 AM   #11
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by jtgofish View Post
I have been down the active/digital crossover /DSP route too but never got great sound compared to a well designed passive crossover. It seems you can get it good but not great.
I know they are popular now, but I experimented with digital crossovers in the late 1990s, and I *never* managed to get good imaging with them.

Digital crossovers usually involve many milliseconds of latency, which is enough time for sound waves to travel several feet. Unless you are very precise about exactly matching the latency to each driver, you can end up with the equivalent of a tweeter that's mounted four or five feet ahead - or behind - the midrange.

Not surprisingly, if that happens, the sound from the two drivers will never integrate properly, and the speaker will never sound good.

Under some conditions, people with good hearing can sometimes hear a difference in stereo imaging if the tweeter and midrange are only one inch away from proper time alignment. That's equivalent to a time misalignment of less than 80 micro seconds. If you're using separate DSP and digital crossovers for each driver, this is the level to which the various speaker outputs should be time-aligned. I don't know how easy this is to achieve in practice.

Though they are not as easy to tweak, I like old-fashioned active analogue crossover networks - a fistful of opamps, resistors, and capacitors. With 1% resistors and capacitors, frequency responses are very accurate. Latencies are usually only a few microseconds, thousands of times smaller than for digital crossovers, so it is relatively easy to time-align the tweeter and midrange by putting the appropriate step in the front baffle. Or you can use a few more opamps and build an all-pass filter to provide the same time alignment electronically, and use a flat speaker front baffle.

Now my ears are a couple of decades older than they were when I worked with those speaker designers, so I'm sure I won't hear some of the fine details I could hear back then with young ears.

-Gnobuddy
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Old 21st September 2018, 06:14 AM   #12
hollowboy is offline hollowboy  Australia
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Originally Posted by Gnobuddy View Post
Digital crossovers usually involve many milliseconds of latency, which is enough time for sound waves to travel several fee [...] you can end up with the equivalent of a tweeter that's mounted four or five feet ahead - or behind - the midrange [...] the sound from the two drivers will never integrate properly, and the speaker will never sound good.
Can you not measure the delay, then adjust for it?

Time alignment

how to time align drivers (with minidsp) ?
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Old 21st September 2018, 06:16 AM   #13
Ugg10 is offline Ugg10  United Kingdom
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The visaton b80, which is slightly bigger at 3.3 seems to be an alternative but not cheap.

B 80 - 8 Ohm | Visaton
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Old 21st September 2018, 08:23 AM   #14
jtgofish is offline jtgofish
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The Faital Pro M5N 8-80.

This is also a very interesting mid/lower treble driver with massive sensitivity.
It would need support of a bullet or slot tweeter with similar sensitivity above 8000Hz but could sound exceptional covering 5-6 octaves.


https://www.google.com/url?sa=t&rct=...UcICSIrIaJqBu-

Last edited by jtgofish; 21st September 2018 at 08:29 AM.
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Old 21st September 2018, 05:28 PM   #15
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by hollowboy View Post
Can you not measure the delay, then adjust for it?
In principle, sure. In practice, distinguishing 50 uS worth of delay on top of a 5 - 10 mS latency (a baseline that's a couple of hundred times longer than the thing you care about) wasn't that easy. You're trying to spot and correct a 1% or smaller difference between two large quantities. What sort of microphones, measurement environment, and test signals will you need to do this? It turned out to be hard, even with access to a really good measurement mic.

With analog active crossovers, the delay is only microseconds to start with. So now you're trying to spot the difference between 2 and 1, rather than 201 and 200. Much easier.

The other complication I found was that the latency and phase shift in the DSP crossover / EQ isn't necessarily constant; depending on the software implementation, it can change depending on the type of EQ you dial in. One implementation we tried introduced an additional 180 degree phase shift every time you added one more notch or peak into the EQ!

-Gnobuddy
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Old 25th September 2018, 03:05 AM   #16
head_unit is offline head_unit  United States
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Originally Posted by jtgofish View Post
I recently bought some NOS Realistic 40-1289A mid tweeters....why aren't these mini point source type drivers more common?
Any suggestions of modern equivalents.?...
I fixed up some old speakers with that type of tweeter for my best friend's husband. He was so happy he still has them some 15 years later. So yes, those old drivers do have a certain goodness about the sound. Why did they die?
- Once you get to higher prices for the raw drivers, other types/materials can simply have more delicacy of sound.
- Fashion! Domes became more nouveau, and "cooler" so those old-school tweeters seemed cheap and old.
I don't think you have many true equivalents today. Most all the stuff you'll find are attempting to be full range (or nearly), not tweeters. And the efficiency of those does tend to be low.
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Old 25th September 2018, 04:22 AM   #17
jtgofish is offline jtgofish
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Originally Posted by head_unit View Post
I fixed up some old speakers with that type of tweeter for my best friend's husband. He was so happy he still has them some 15 years later. So yes, those old drivers do have a certain goodness about the sound. Why did they die?
- Once you get to higher prices for the raw drivers, other types/materials can simply have more delicacy of sound.
- Fashion! Domes became more nouveau, and "cooler" so those old-school tweeters seemed cheap and old.
I don't think you have many true equivalents today. Most all the stuff you'll find are attempting to be full range (or nearly), not tweeters. And the efficiency of those does tend to be low.

Yes the "certain goodness" is obvious.There is a bit of classic Tannoy dual concentrics about them.That same sense of coherence and timing.They also seem to integrate with a woofer using just a series inductor so you get all first order crossovers which also helps with phase coherence.

Last edited by jtgofish; 25th September 2018 at 04:24 AM.
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Old 25th September 2018, 07:10 AM   #18
TMM is offline TMM  Australia
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Having the xmax to support 500Hz at sufficient volume is one thing. Having a mechanical arrangement which remains linear at that excursion is another thing. Most 2" drivers start becoming very non-linear below about 800Hz-1kHz if you push them >95dB/1m.

The best i've seen is the Peerless TC7FD00-04. Cross at about 800Hz LR4.

Last edited by TMM; 25th September 2018 at 07:18 AM.
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Old 25th September 2018, 08:37 AM   #19
jtgofish is offline jtgofish
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This Peerless could also be OK.
Again more of a wide range driver than a mid/tweeter but could work fine as mid/tweeter if you cut off the bass below about 500Hz or so.
86.5 db /watt sensitivity which is higher than most of the others.


https://www.google.com/url?sa=t&rct=...AeJv2i_GVaZ0Ui
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Old 25th September 2018, 02:34 PM   #20
phivates is online now phivates  United States
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That little mid-tweet had two problems: no sizzle and limited dispersion. Now we appreciate its virtues. Back then AR had sold us on the virtues of the dome and we bought in.
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