The dome midrange thread

For an average 12" the upper limit would be 800 hz before it starts to break up. That would be an acceptable xover to a 2" mid dome.
The directivity of a 12" woofer is going to be substantially different than a 2" dome at 800 Hz. Even going from a 10" to a 3" dome at 500 Hz results in an abrupt directivity change based on my recent simulations.

In your opinion, how much importance do you put on a smoothly and linearly changing directivity in the range from 100 to 1000 Hz?
 
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I like larger midbass drivers, which is why I like to use at least an 8" for the 200 to 700 hz range.
I agree after trying smaller mid bass drivers, like a Vifa 6.5 inch, they do not have the same impact and scale in the low mid range as a 8 inch or larger driver. I do think that a 8 inch is the sweet spot between cone weight, speed and displacement to match a 2-3 inch dome but i have no experience with large bass drivers like a 10 or 12 inch for this low mid range up to 800 Hz. A 8 inch is even better when combined with a sub woofer and cut of at 40 Hz. to restrict cone movement at the low end.
 
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The tweeter that goes with this mid has got some concerning resonances just above Fs. There are two significant bumps there which could be caused by the chamber design and VC gap venting. The price point looks good, but I'll need to see some further assessment. I do like the compact design. It looks a little like a rip off of the bliesma faceplate design.
If used with the mid dome at 3-4K crossover the resonance should be attenuated. I think this combo looks promising with a 93-95db midbass 500hz and up.
 
@hifijim Those are interesting observations. I've used similar xover points with 2" and 3" domes and had decent results with power response and overall stable average linearity.

I think it depends highly on the specific chosen LF driver, whether it performs decently off axis at a given xover point. Additionally, the chosen CTC spacing, filter slopes and even acoustic center alignment can significantly change off axis characteristics.

Larger dust caps on a cone driver can help improve off axis behavior, even though these generally tend to promote upper midrange beaming effects, especially if the cone profile is deeper than usual. Even the surround profile and dampening can change this. When you have LF drivers with sharp dips and notches in the pistonic range, these usually indicate a driver with very lively surround and/or rear suspension resonance behavior.

The acoustic phase has to be examined without a filter in place, so FR directly correlates with it and can be directly considered with off axis performance. Using the FRD data will show in a sim whether the LF driver can deal with a higher than usual xover. By this, I refer to an xover point higher than typically chosen for use with a cone midrange. With wider filter slopes ie. 2nd order, its more fitting to use a lower LP xover on the LF. This is due to increased overlap necessitating an extended smooth FR for decent driver integration.

Steeper LP slopes help with a higher LF xover, but the sharper transition will usually exagerate a directivity change when used with smaller mids, as you'd expect. Again, this is where the specific character of LF and MF drivers needs to considered.

That being said, IMO its important to measure the individual drivers mounted in the specific baffle and enclosure configuration. This as a complete package of variables will determine with certainty whether a higher or lower xover at specific slopes is possible.

I'm sure there are specific sim models able to show all these little variables not commonly accounted for, but this more complex modeling isn't considered by the typical sim platforms available to most diy. It requires more advanced modeling to incorporate all these little driver attributes in the sim to end up with a precise model which can show more exact details in off axis performance of an LF driver.

Larger cone drivers can behave very unpredictably at the first radial breakup mode. Some surrounds are constructed with varying thickness throughout the surround profile. There are cones which can also vary in thickness and stiffness progressively over their diameter. The side profile shape is also another detail which isn't normally considered. The spider profile and compliance is also non linear on most drivers, but this obviously doesn't directly affect dispersion. It does however affect overall driver linearity, so its an important parameter to be considered in the FR model.

Sorry for the long winded post, but I feel its important to look at all these little things when considering a certain driver. I personally wouldn't exclude using a driver just because it didn't sim favorably. It depends on so many smaller, less apparent factors whether a driver is suitable for use at higher xover points. Sims just don't allways account for these factors. They offer a rough guide but ultimately its a more complex issues.
 
The directivity of a 12" woofer is going to be substantially different than a 2" dome at 800 Hz. Even going from a 10" to a 3" dome at 500 Hz results in an abrupt directivity change based on my recent simulations.

In your opinion, how much importance do you put on a smoothly and linearly changing directivity in the range from 100 to 1000 Hz?

This is one of the reasons why I cut off my HiVi at 400 Hz.
The dispersion behavior of a loudspeaker should not look like a Fir tree.
This problem is even more important in the PA area than at home, but should not be ignored.
I try to cover the sides of the 10” so that the dispersion is wider at the crossover frequency.
And I hope that this will not increase the distortion because the air is pulling at the cone through the cover.


A few centimeters of cover to the left and right of the bass speaker should be enough.
Then the width is more like an 8” chassis
 
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Sorry for the long winded post, but I feel its important to look at all these little things when considering a certain driver. I personally wouldn't exclude using a driver just because it didn't sim favorably. It depends on so many smaller, less apparent factors whether a driver is suitable for use at higher xover points. Sims just don't allways account for these factors. They offer a rough guide but ultimately its a more complex issues.
Since I have a table saw and the hardware store is just around the corner, I simply try out such things with a quickly glued-together box and my measuring microphone.
I produce a bit more waste this way, but I learn much faster than spending days racking my brains over something that can be checked within hours.
Sometimes a piece of cardboard is enough to get an impression of the influences of the housing.
 
@PingPongTennis I've combined many paper drivers with aluminum mids and tweeters without a noticeable shift in acoustic character between the two at xover. The only place you can start identifying diaphragm or cone material is above pistonic operation. Under this point, the drivers should be mostly inert, with motor design being the primary defining element of the driver's acoustic character.

Even crossing fairly high from a cone to a dome, the woofer will still be operating in pistonic mode. For an average 12" the upper limit would be 800 hz before it starts to break up. That would be an acceptable xover to a 2" mid dome.

Crossing from a 2" dome mid to dome tweeter is also un-problematic in terms of still being in pistonic mode at xover. That's assuming you're not crossing higher than 5k with a 2nd or higher order filter and notching the upper mid breakup. You shouldn't be able to discern the diaphragm material under these circumstances, but its important to understand the THD profile of the driver can still be a direct correlation to dome material (within reason). The VC former design can dictate this more than any other element of the motor.
No. 🙂
Let's leave the tweeter out of this consideration.
I think the bass and the midrange should go together.
The easiest way to do this is to use similar materials.
There may be a few exceptions but in most cases this rule of thumb works well to get good results.
 
@PingPongTennis I used to have the same opinion about this subject. It took some time to do extensive research and listening to understand why certain diaphragm materials sound the way they do, as well as their out of band breakup characteristics. I recommend you investigate some higher end drivers which don't follow the rules. You will be surprised what exceptions there are.
 
The second pair of HiVi has been fitted with protection.
They are super sensitive to brooms or the wrong hand movement.




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I bougth a Daytong RS-52an and loaded it into a horn made from an 8" diameter $2 funnel. Lol! With some simple EQ it's pretty impressive sounding. There's a notch on-axis at about 7kHz, so useable I'd say from 500 Hz to 5 kHz. Strangely, off axis you can see that the usual spike at 12 kHz looks like a deep notch. I also applied a litle EQ to bring it down, so the notch effect from being horn loaded isn't really that deep. Maybe with some expertise on the throat design the response could be extended a bit higher.
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I bougth a Daytong RS-52an and loaded it into a horn made from an 8" diameter $2 funnel. Lol! With some simple EQ it's pretty impressive sounding. There's a notch on-axis at about 7kHz, so useable I'd say from 500 Hz to 5 kHz.
I've taped the funnel to the Dayton driver and set it on a stand so it's pointing at me. Looking at the in-room response at the listening position I'm seeing decent output down to about 350 Hz, and up to about 13.5 kHz. That's with the midrange EQ'd down quite a bit. Crossing it over to my woofer horns at about 350 Hz yields a surprisingly smooth and pleasant sound that doesn't seem strained at my normal listening levels. I think there's some hope for this with a bigger horn. Also, the notch at 12.5kHz is not apparent in whole room response, Instead, just a huge peak at the 12 kHz breakup that needs to be EQ'd down.
 
More on the Dayon RS-52an. After messing around with plastic funnels on these dome midranges, I finally had a listen to them in stereo without a horn. No baffle of any kind. Just propped up and fairly clear of any nearby things for sound to reflect and refract off of.

I have to say, these do deliver on some of the promise of what I always hoped a dome midrange could do. I added an FIR filter to flatten the response and phase out between about 500 and nearly 20 kHz on axis. Off axis they roll of above 20 kHz of course. But it sounds pretty amazing when crossed over to some woofers that are completely different - a big stack of horn woofers. It doesn't sound as solid and direct as it did with the funnel horns. But it's super detailed and the imaging is spooky and magical.

Years ago I had some Morel MDM 55 that I thought were OK, but I never got them to do anything that really impressed me. And, one of them had an issue with it's motor occasionally getting stuck. So I guess that's not a fair comparison. In any case, a point source dome covering a wide range of frequencies in the middle of the human hearing range is, I think, a very good idea. What I'm wonder is if I can horn load it well enough to give it a boost without losing some of it's magic in the process. I think the magic may be a lot to do with minimum baffle. In that case, the horn is going to offer it's own kind of lifelike presence but not have the ethereal lightness and airiness of the minimum baffle. Or maybe there is a way to have one's cake and eat it too? Building horns is difficult and expensive.
 
Well yes that has been done:

1”
2”
5”

Then you choose your separate bass bin or subwoofers below ~150Hz

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So now we have smoother transition between drive units and lower directivity in the horizontal plane.

But compared to a coaxial we have asymmetrical directivity above and below the on/reference axis.

If we want symmetrical directivity in vertical axis a coaxial will be better, but the directivity will be higher.

trade offs.
 
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thanks that's sort of what I meant but more like this included sketch . I have dynaudio tweeters and d76 middomes and 9.5 in bass drivers and was thinking of picking up some 5inch dynaudio woofers from their automotive line to bridge the gap . moddled the ts parameters of the driver I had in mind and it gave a f3 of 100hz in a 7ltr sealed enclosure so should work perfectly ? can you see any problems with my little idea ?
 

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No listening experience, but as many of us won't hear much beyond 16khz, I might be tempted to skip using a tweeter, as some Audax based speakers did. I recall one being crossed at 800hz, to a pair of 6.5" that was certainly near 50mm (though perhaps less)
it's a error to think that if we can't hear beyond 15khz we can't hear a beaming and distorded high frequency ..
 
Well yes that has been done:

1”
2”
5”

Then you choose your separate bass bin or subwoofers below ~150Hz

View attachment 1406431

View attachment 1406432


So now we have smoother transition between drive units and lower directivity in the horizontal plane.

But compared to a coaxial we have asymmetrical directivity above and below the on/reference axis.

If we want symmetrical directivity in vertical axis a coaxial will be better, but the directivity will be higher.

trade offs.
Reminds me my experiments with domes.
 

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