I acquired a pair of Dayton DC50FA-8. They are my first mid-dome drivers. In fact, I used to listen to the mid-dome drivers but here is my first DIY project with this kind of drivers.
By the way, from what I earned from listening experience on the 2" mid-domes, here is the points I have noted:
1) The high frequency should be extended as highest as possible. In other words, the low-pass filter should be set as highest frequency as possible. I used to experiment by setting crossover at 2kHz versus 3.5kHz. And I preferred the latter. However, this is only my preference.
2) The low frequency isn't necessary to go as lowest frequency as possible. However, I confess that I still don't get where the optimal frequency should be. But, I have an assumption that maybe it should be considered together with the woofer's response. The optimum point may be in between the lowest of the midrange and the highest of the woofer.
Anyway, let's consider my drive units, the DC50FA-8. I have a question about it.
1) According to the data below and regarding the note no.1 above which I mentioned that I preferred to have crossed the midranges as highest frequency as possible, what frequency do you think is the highest point that still won't cause the problems? For me, I think it is about 5kHz because the impedance at 5kHz is approx. 8 Ohms which I think it's top-end of the impedance that is still not required to use the impedance EQ circuit (Zobel). What's your opinion?
2) For the low-end frequency, I also pick the 500Hz because of the same reason as the high-end frequency--8 Ohm impedance. What's about your opinion?
3) Besides those 2 questions above, I'm still curious if the low-end is intended to be crossed as the lowest frequency as possible in order to create the steeper acoustical slope, i.e. the 4th order slope by the 2nd order high-pass filter, which frequency can meet the requirement?
By the way, from what I earned from listening experience on the 2" mid-domes, here is the points I have noted:
1) The high frequency should be extended as highest as possible. In other words, the low-pass filter should be set as highest frequency as possible. I used to experiment by setting crossover at 2kHz versus 3.5kHz. And I preferred the latter. However, this is only my preference.
2) The low frequency isn't necessary to go as lowest frequency as possible. However, I confess that I still don't get where the optimal frequency should be. But, I have an assumption that maybe it should be considered together with the woofer's response. The optimum point may be in between the lowest of the midrange and the highest of the woofer.
Anyway, let's consider my drive units, the DC50FA-8. I have a question about it.
1) According to the data below and regarding the note no.1 above which I mentioned that I preferred to have crossed the midranges as highest frequency as possible, what frequency do you think is the highest point that still won't cause the problems? For me, I think it is about 5kHz because the impedance at 5kHz is approx. 8 Ohms which I think it's top-end of the impedance that is still not required to use the impedance EQ circuit (Zobel). What's your opinion?
2) For the low-end frequency, I also pick the 500Hz because of the same reason as the high-end frequency--8 Ohm impedance. What's about your opinion?
3) Besides those 2 questions above, I'm still curious if the low-end is intended to be crossed as the lowest frequency as possible in order to create the steeper acoustical slope, i.e. the 4th order slope by the 2nd order high-pass filter, which frequency can meet the requirement?
For the low end I would also look at distortion, 2" dome mids will have increased distortion at lower frequencies. Have just been through this trying to marry up a SB WO24P-4, Morel EM1308 and Morel ET448 drivers. Even though the Mid has a FS of 320Hz (published data) you can't really cross them much lower than 600hz 4th order or 750-800hz 2nd order due to rising distortion. Below is the measurements I made at around 85dB for the three drivers and how the distortion overlaps and the ranges I looked to crossover. I ended up at around 800hz and 4khz.
There is a rule of thumb that you should not cross a mid or tweeter lower than 2x Fs, better 2,5 times. You can measure all day long, but this will be right in most cases.
There are a million way's to screw up a speaker project, but much fewer options to make it right. Good luck!
There are a million way's to screw up a speaker project, but much fewer options to make it right. Good luck!
Newb here: shouldn't the upper crossover selection be governed by directivity and FR - as one is trying to mate the mid to the tweeter in both concerns?
Dispersion is often the final arbiter. For the upper bound of your mid, you want the point where the off-axis response is still very close to on-axis. The same is true on the low end (mid HP, woofer LP), but this time you look at your woofer. You want a place where your woofer's dispersion is ideal and your midrange is:
- Well above resonant point
- Low distortion
- Flat response
I wrote about this in some detail here.
There is also something to be said about having a crossover point in the vocal range. Not everyone agrees this is an issue, but it does encourage you to get a mid that goes down further.
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Yes, but what is that in regard to? There's no direct connection to excursion..
The story used to go that the resonance interfered with the filter resonance. Once you measure and are in control of that you can make the correct blend, so are we then free to violate the rule of thumb?
For me, the Fs is useful lower bound more so because the distortion tends to rise around there. The distortion profiles are a better guide, but since those are most often absent the Fs as a guide is not terrible to use, especially when you are shopping for parts on little more than online spec sheets.
For the 2-inch midrange in question, we have Fs = 371 Hz. The impedance peak that shows up at that frequency is due to the large excursion that this driver undergoes at that frequency. From the published frequency response curve, its SPL at 370Hz is about 87dB.
Without considering driver excursion limits, it would seem that this driver could be easily crossed over at its Fs.
However, if we drive it with 10W at that frequency, we are likely to get close to if not exceed its Xmax excursion capability. When this occurs, it would produce significant distortion at those higher SPLs. If we cross over one octave higher, we get a much smaller excursion at Fs. As a result of the attenuation of the high-pass filter, the driver's behaviour is much more linear and lower in distortion when it is trying to reproduce 370Hz at higher input power levels.
Below is a VituixCAD simulation of the Dayton DC50FA-8 2-inch midrange dome when driven by 50W referenced to 8-ohms. A 2nd-order Butterworth high-pass filter with a 740Hz cut-off frequency has been applied. At this power input level, we have used up 60% of the driver's Xmax, and the peak excursion occurs at about 500Hz. These results seem to indicate that the 2xFs rule of thumb is entirely reasonable in this instance.
If we increase the cut-off frequency of the high-pass filter to 2.5xFs, we get the following results. The peak excursion has been reduced from 0.6mm down to 0.4mm.
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I think it is best to use two dome mids with a tweeter mounted between them.A single 2 inch dome has quite a small radiating surface compared to say a 4 or 5 inch cone midrange.Sonique Encore speakers used that design and they sound fantastic.One of the very best midranges you can hear.And of course Duntech used that format before them.I have owned some very good single dome midrange speakers including the highly regarded flagship Dynaudio C5 but I think the double dome Soniques had a better midrange-more dynamic and more body .
https://soundmediagroupau.s3.ap-sou...05_2013/post-104548-0-81922200-1368414846.jpg
https://soundmediagroupau.s3.ap-sou...05_2013/post-104548-0-81922200-1368414846.jpg
Hey, it's such an interesting question I decided to post a new topic and not derail this thread. Please find it here:
https://www.diyaudio.com/community/threads/is-fs-a-stand-in-for-distortion.416072/#post-7757688