FWIW, in designing bass horns, the pioneers determined that a square mouth of the same area as the desired circular area could be 'squashed' to a 1: 1.273 max ratio before it affected design/performance, so your 1:2.7 will need to be longer for a given circular one and has been pointed out there's potentially some chuffing, though can be critically damped at some loss of lowest bass, i.e. higher corner frequency roll-off.
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Thanks again all! It sounds like we are close to a solution, and the following queries are as much about education as perfection seeking.
@GM - thanks for the learnings & tips! Does the 1:2.7 ratio refer to the ideal or minimum port diameter vs cone area? Or is it port length vs diamater?
Interesting about the square vs circular port ratios. I had been wondering about turning the existing port into a slotted vent shape. I wonder if plasticine will be my friend...
Alpair 11ms = 111cm3 so / 2.7 = 41.1cm? Or cm3? Can someone confirm that this is the optimum or minimum ideal diameter? Or port area? If 41.1cm3 that equals 7.23 cm diameter port.. .😒
If the 2.7 ratio refers to port length vs diameter then please feel free to school me!
@tansand - 4cm x 9cm does look flatter for frequency 👍 I am uncertain whether the step or shelf on the group delay plot is an issue?
@GM - thanks for the learnings & tips! Does the 1:2.7 ratio refer to the ideal or minimum port diameter vs cone area? Or is it port length vs diamater?
Interesting about the square vs circular port ratios. I had been wondering about turning the existing port into a slotted vent shape. I wonder if plasticine will be my friend...
Alpair 11ms = 111cm3 so / 2.7 = 41.1cm? Or cm3? Can someone confirm that this is the optimum or minimum ideal diameter? Or port area? If 41.1cm3 that equals 7.23 cm diameter port.. .😒
If the 2.7 ratio refers to port length vs diameter then please feel free to school me!
@tansand - 4cm x 9cm does look flatter for frequency 👍 I am uncertain whether the step or shelf on the group delay plot is an issue?
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In regards to Dave p10's click test, interesting... This drivers impedance is listed as 7.2ohms. Most of my amps have low damping factors of 20 to 25. The first one I'll use is 23.
So 7.2ohms/23 = 0.313 ohms? So a 0.3ohm resistor?
@planet10 Hi Dave - very sorry to trouble you... I hope this isn't really bad form! You seem to be a resident expert on markaudio drivers. I just wonder if you could give this project a seal of approval, in regards to driver choice?
Nobody so far seems to have experience with the alpair 11ms.
Asides from port chuffing etc, I was initially worried about the wide dispersion of this model, and my deep edge reveal as per original photos.
Any comments would be most gratefully received 🙏
So 7.2ohms/23 = 0.313 ohms? So a 0.3ohm resistor?
@planet10 Hi Dave - very sorry to trouble you... I hope this isn't really bad form! You seem to be a resident expert on markaudio drivers. I just wonder if you could give this project a seal of approval, in regards to driver choice?
Nobody so far seems to have experience with the alpair 11ms.
Asides from port chuffing etc, I was initially worried about the wide dispersion of this model, and my deep edge reveal as per original photos.
Any comments would be most gratefully received 🙏
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The 4x9 is better than the 3.7 x 10 port for both those, you want the step response ripple to die out faster, and the group delay I've read should ideally be kept below .01, lower is better. I wouldn't get too alarmed because it's near the top of the chart, the chart will rescale itself according to the level. The two peaks in the impedance are because it's a vented enclosure. I think 4 x 9 is about the biggest you can do, as you'll need a port diameter of distance, at least, between the end of the port and the back wall, another rule of thumb.
Ideally you can find one of those push in ports they have on ebay of the right diameter so you can buy extra ones, drill a hole with a hole saw, and experiment with different lengths to see what you like, you might like it shorter.
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Thanks again @tansand 🙂
Super helpful & educational, I really appreciate it.
I used the modeling software with a few other Mark Audio drivers for comparison, as attached. Played with optimal port sizes to flatten curves, none look awful, and all have different overall efficiencies etc
If anyone thinks any of these stand out versus the Alpair 11ms please speak up!
Super helpful & educational, I really appreciate it.
I used the modeling software with a few other Mark Audio drivers for comparison, as attached. Played with optimal port sizes to flatten curves, none look awful, and all have different overall efficiencies etc
If anyone thinks any of these stand out versus the Alpair 11ms please speak up!
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H x W max ratio, < ~17 m/s limits pipe dia., HxW ratio/acoustic pathlength which includes pipe end correction.
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Thanks @GM - lots to get my head around there!
In the meantime I have decided the Alpair MS11 looks the best fit all round, so have ordered a pair!
I was also able to buy a 39mm x 135mm flared trumpet port. I will saw this to size. Is there any wisdom about which end of the flare is more useful? Eg. Facing outwards at the listener, or inside the speaker box? Port chuffing minimizing etc
I attach the most accurate up to date plots, having finessed the internal volume. Turns out there was more bracing than I at first could see. Plots still look good... although for the first time I entered the voice-coil inductance LE (mH).
The impedance rise on the last graph, with increased frequency looks very scary!!! 400ohms at 10,000 hz?!
Can anyone tell me if this is as worrisome as it looks?
I hope not. Worst case I end up with a great pair of drivers 🙂
In the meantime I have decided the Alpair MS11 looks the best fit all round, so have ordered a pair!
I was also able to buy a 39mm x 135mm flared trumpet port. I will saw this to size. Is there any wisdom about which end of the flare is more useful? Eg. Facing outwards at the listener, or inside the speaker box? Port chuffing minimizing etc
I attach the most accurate up to date plots, having finessed the internal volume. Turns out there was more bracing than I at first could see. Plots still look good... although for the first time I entered the voice-coil inductance LE (mH).
The impedance rise on the last graph, with increased frequency looks very scary!!! 400ohms at 10,000 hz?!
Can anyone tell me if this is as worrisome as it looks?
I hope not. Worst case I end up with a great pair of drivers 🙂
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Impedance rise with frequency is normal, but that value calculated by the software is most likely bogus.
You have, so you're good. 🙂
jeff
Not sure of what your port looks like, but if it's like other push in kinds and you want to avail yourself of that you'll need to cut off the inside flare, because the side with the raised fins presses against the inside of the hole..
Thanks @tansand - indeed it's as you suggest. See attached. The thing is, as my existing port is 9.9cm diameter, I have to faff around anyway! So although I will likely cut off the inner flare, I have options.
I could even try to rejoin it at the correct length (cut a section out) although this could go wrong if sausage fingers prevail...
That's why I'm curious if the flare makes more of a difference at either end for less chuffing!
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I surely do not know. What I would do if it were me is glue a small board on the inside (clamp) to seal over where the old port was, then make a new hole somewhere else on the front. edit: Although if you have some way of making a 9.9cm circle of the right thickness, you could do the board and then glue the circle to the front of it after it's dried, and put the new port in the middle of that..
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Did they come with the F10 FR? It is really quite good.
Width 251x Height 392x Depth 190 mm
15mm wood, and extra 15mm for the grill… extinated net volume > 11.5 litre.
A11ms will work but a bi less is better.
dave
Width 251x Height 392x Depth 190 mm
15mm wood, and extra 15mm for the grill… extinated net volume > 11.5 litre.
A11ms will work but a bi less is better.
dave
CHN-110 is a first rarte driver for peanuts. Might be a bit tightfitting into 11 litres, but i have fitted it into 13l so shouldbedoable.
dave
dave
Yes, though perhaps a 2nd iteration? See Photo. Sadly only one working however...
You missed the mighty 27mm edge reveal (2nd photo) 10.2 litres is my most accurate estimate. This was what has me most worried with the Alpair 11ms & it's negative camber/ wide dispersion... any thoughts??
Indeed. I tried to make a simulation for this work, but it was beyond my skills. Perhaps vented. In any case I've ordered the 11ms, which does seem to fit better on paper!
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Drivers arrived and now warmed up. I knocked up some basic cardboard open baffle stands to try them out 🙂
Really impressed and happy with my choice. Paired with a sub while running open baffle. Very expansive sound, with great detail. Lovely tone also, although whether that comes more from my amplifier, who knows.
The rear speaker terminal panel is thin plastic and almost directly behind the driver inside! To improve box damping I bought some butyl and sticky felt 😀
A bit fidly to fit, as the inside bracing comprises triangular lengths of wood gluing front baffle and rear face. Still after much cutting, happy with result.
Unfortunately the baffle cut out for original drivers is wider than ideal for the MS11 alpair, meaning new bolt holes are too close to empty space... (I bought hex bolt fittings so as not to screw directly into baffle as they will be coming on and off a good few times for adjustments).
Managed to source some 5mm plywood hoops on ebay, 130mm by 200mm. The MS11s need about 140mm to squeeze in tight, so thought I would rasp file to fit. After waiting almost a week unfortunately I was sent 150mm inside diameter by 200mm outer. The same diameter as the speakers already have 🤦♂️
Really impressed and happy with my choice. Paired with a sub while running open baffle. Very expansive sound, with great detail. Lovely tone also, although whether that comes more from my amplifier, who knows.
The rear speaker terminal panel is thin plastic and almost directly behind the driver inside! To improve box damping I bought some butyl and sticky felt 😀
A bit fidly to fit, as the inside bracing comprises triangular lengths of wood gluing front baffle and rear face. Still after much cutting, happy with result.
Unfortunately the baffle cut out for original drivers is wider than ideal for the MS11 alpair, meaning new bolt holes are too close to empty space... (I bought hex bolt fittings so as not to screw directly into baffle as they will be coming on and off a good few times for adjustments).
Managed to source some 5mm plywood hoops on ebay, 130mm by 200mm. The MS11s need about 140mm to squeeze in tight, so thought I would rasp file to fit. After waiting almost a week unfortunately I was sent 150mm inside diameter by 200mm outer. The same diameter as the speakers already have 🤦♂️
