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Multi-Way Conventional loudspeakers with crossovers

Juggling Midrange Location in a Unity Horn
Juggling Midrange Location in a Unity Horn
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Old 23rd January 2018, 07:02 AM   #11
Hylle is offline Hylle  Denmark
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How wide a frequency response is possible with midrange build this way? How low is possible? Is it possible to put a midrange i na bigger volume and make it go lower?
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Old 23rd January 2018, 07:09 AM   #12
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by Hylle View Post
How wide a frequency response is possible with midrange build this way?
Depends on a million factors. With the Celestion or Misco midranges I can get about two octaves. The tricky part here isn't just the bandwidth, it's also the rolloff. For instance, the AuraSound NS3 can do a bandwidth that's comparable to the Misco woofer, but due to it's high MMS, low QES and high QTS, you wind up with a very steep rolloff on the lowend. 3D printers and phase plugs are your friend here, phase plugs help a lot.

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How low is possible?
Take a look at GM's post in the first page of the 'suitable midrange for a Unity horn' thread

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Is it possible to put a midrange i na bigger volume and make it go lower?
I tried that, but it gets tricky. As you go lower you start to run into issues with the compression ratio. For instance, if you go an octave lower, you're moving 4X as much air, and that requires a larger midrange tap. Check out my post history, I posted a thread about this a couple of weeks ago.
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Old 23rd January 2018, 06:17 PM   #13
Jack Arnott is offline Jack Arnott  United States
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Hello Patrick,
A while back you posted about compression ratio, and the 10-1 ratio. I thought you were talking about the ratio of cone to the size of the holes that the sound went through into the horn. Now I see you are referencing the compression of the cone(s) to the area of the horn where it enters.

What is optimal size for the holes?
Does this also vary if you are using one driver instead of two or four?
Is the ratio in regards to the driver, or the horn entrant area or both?

Thanks.
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Old 27th May 2019, 03:40 PM   #14
ErikNils is offline ErikNils
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I stumbled onto this thread because I was running into trouble with the compression ratio for my mids and then I got an interesting thought. Instead of reducing the number of mid-range drivers could one use different locations and different crossover points? Like people do with regular box speakers with 2.5 way? You could put 2 mids as close to the tweeter as possible and 2 further down the line.

To prevent phase issues the the drivers close to the tweeter should have longer ports which creates it's own problems..... I am not knowledgeable enough yet to work this out but I thought I just throw this thought out there.
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Old 27th May 2019, 04:18 PM   #15
nc535 is offline nc535
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lots of people have had success without that complication

as to compression ratio, that doesn't matter so much. what does matter is particle velocity in the port throat exit. Keep its peak below 17m/s like you would for a vented woofer. HornResp will show that to you.

A 10:1 compression ratio typically lets you drive the driver to full Xmax. With 4 drivers, you don't need to do that. At lower drive levels you can have a higher compression ratio. I might have different advice were we talking about woofers instead of mids.

If you make the ports too small, you will hear noise or distortion. Better to start small and drill out larger if you hear or measure issues. That way you do least damage to the polars or the horn's appearance.
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Old 27th May 2019, 06:27 PM   #16
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by Jack Arnott View Post
Hello Patrick,
A while back you posted about compression ratio, and the 10-1 ratio. I thought you were talking about the ratio of cone to the size of the holes that the sound went through into the horn. Now I see you are referencing the compression of the cone(s) to the area of the horn where it enters.

What is optimal size for the holes?
Does this also vary if you are using one driver instead of two or four?
Is the ratio in regards to the driver, or the horn entrant area or both?

Thanks.
It's a whole bunch of variables, unfortunately.

The main variable is:

How close are the midrange taps to the throat? That variable basically dictates your upper limit, because the reflection off of the throat creates a notch in the response.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Here's the waveguides from my current project, the frequency response of the midrange and tweeters, and the polar response.

In the measurement, you can see that the midrange array is starting to roll off at 1.2khz. This is due to the efficiency bandwidth product of the midranges, along with the distance from the throat.

I think there are a bunch of other factors involved also:

1) anecdotally, I've noticed that long midrange taps seem to have lower distortion.

Click the image to open in full size.

I think that this is similar to what happens with bandpass boxes. If you tinker with a bandpass box calculator, you'll find that the *diameter* of the port gets larger and larger and larger as the volume of the front chamber increases. So I think that something similar happens with the midrange taps on a Unity horn; basically if you can figure out a way to enlarge the volume of the front chamber, you can get away with a smaller exit.

The midrange taps on my waveguide are over an inch long, whereas the midrange taps on the Lambda Unity Horn are a fraction of an inch, about 1/2" if memory serves. Of course, there's NO WAY I could get away with what I'm doing without a 3D printer; the shape of my taps would be nearly impossible in wood. (The cross section is expanding, to maximize the flow through the taps.)

Click the image to open in full size.

Lambda Unity Horn

Click the image to open in full size.
2019 Compact Unity Waveguide c/o yours truly

I have tried out a zillion different midrange tap shapes, and I haven't found anything that outperforms the shape that I am using in this project.

Click the image to open in full size.
It's basically a wedge that begins as a circle.
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Old 27th May 2019, 06:31 PM   #17
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by ErikNils View Post
I stumbled onto this thread because I was running into trouble with the compression ratio for my mids and then I got an interesting thought. Instead of reducing the number of mid-range drivers could one use different locations and different crossover points? Like people do with regular box speakers with 2.5 way? You could put 2 mids as close to the tweeter as possible and 2 further down the line.

To prevent phase issues the the drivers close to the tweeter should have longer ports which creates it's own problems..... I am not knowledgeable enough yet to work this out but I thought I just throw this thought out there.
You could.

I think the challenge would be the expense.

IE, if you had two mids that were 3" from the throat, and two mids that were 5" from the throat, and each had it's own xover... It will probably be simpler and cheaper to have four mids that are 4" from the throat, with a single sover.
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Old 27th May 2019, 08:33 PM   #18
InOtIn is offline InOtIn
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Quote:
Originally Posted by Patrick Bateman View Post
If you tinker with a bandpass box calculator, you'll find that the *diameter* of the port gets larger and larger and larger as the volume of the front chamber increases. So I think that something similar happens with the midrange taps on a Unity horn; basically if you can figure out a way to enlarge the volume of the front chamber, you can get away with a smaller exit.
Patrick,

This is contradictory. If the "diameter of the port gets larger and larger and larger as the volume of the front chamber increases", you would need to decrease "the volume of the front chamber [to] get away with a smaller exit", no?
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Old 27th May 2019, 08:39 PM   #19
Patrick Bateman is offline Patrick Bateman  United States
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Good catch!

Yes, my comment is completely backwards.

It says :

"If you tinker with a bandpass box calculator, you'll find that the *diameter* of the port gets larger and larger and larger as the volume of the front chamber increases.

should say:

If you tinker with a bandpass box calculator, you'll find that the *diameter* of the port gets larger and larger and larger as the volume of the front chamber DECREASES.
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