Hello
I've just bought a pair of Coral Flat 5's on ebay..does anyone have any t/s parameters? I was only able to find some info on the Flat 6's. Their DC resistance or a way to measure it would be especially helpful. Unfortunately I can't afford a woofer tester at this point.
I've just bought a pair of Coral Flat 5's on ebay..does anyone have any t/s parameters? I was only able to find some info on the Flat 6's. Their DC resistance or a way to measure it would be especially helpful. Unfortunately I can't afford a woofer tester at this point.
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FWIW, a starting point.............
Using the II's minimal specs and erroneously using Qo as Qts, then with Mo, Vas = ~12.97 L, ergo a max flat alignment is theoretically ~35.24 L tuned to ~51 Hz with a ~5.08" diameter hole if a 19 mm baffle is used.
GM
Using the II's minimal specs and erroneously using Qo as Qts, then with Mo, Vas = ~12.97 L, ergo a max flat alignment is theoretically ~35.24 L tuned to ~51 Hz with a ~5.08" diameter hole if a 19 mm baffle is used.
GM
Not accurately, unless the Mo, Fs, effective radius specs are. As I said, I made some erroneous assumptions to derive what all I calculated, so I chose to assume Mo = Mms to calc Vas. FWIW, the calc'd Vas is within an acceptable range for the driver size, Fs.
WRT the box calc, I have some experience with the simple Qo calculations and since they're fairly accurate in the range around ~0.4 Qts, I chose to assume Qo = Qts figuring at worst, the box would be too big and/or tuned too low, so with a simple vent hole it would have plenty of tuning flexibility for optimizing it to suit your app. This assumes of course that I used the right specs for your drivers and they are accurate.
All thing considered, I doubt they're even remotely close, but I'd be surprised if you can't make the suggested box work and if turns out to be way too large (or too small, which I doubt unless driving them with a high output impedance amp) you can always make new ones, so suggest you just cobble one together from scrap or other cheap materials, even industrial strength cardboard. Just make sure there's no air leaks before each modification or the effort will be wasted.
Vas = 0.01*po*c^2*Sd^2/((2*PI()*Fs)^2*Mms)
where:
po = 1.21 Kg/m^3
c = 344.43 m/s
Sd in cm^2
Mms is in grams
Note that different programs tend to use different po, c values, so for best theoretical accuracy use the ones for the program.
Bottom line, you want accurate specs you'll have to measure them somehow, whether by someone else, use a woofer tester or do it 'long hand': http://www.diysubwoofers.org/measure.htm
GM
WRT the box calc, I have some experience with the simple Qo calculations and since they're fairly accurate in the range around ~0.4 Qts, I chose to assume Qo = Qts figuring at worst, the box would be too big and/or tuned too low, so with a simple vent hole it would have plenty of tuning flexibility for optimizing it to suit your app. This assumes of course that I used the right specs for your drivers and they are accurate.
All thing considered, I doubt they're even remotely close, but I'd be surprised if you can't make the suggested box work and if turns out to be way too large (or too small, which I doubt unless driving them with a high output impedance amp) you can always make new ones, so suggest you just cobble one together from scrap or other cheap materials, even industrial strength cardboard. Just make sure there's no air leaks before each modification or the effort will be wasted.
Vas = 0.01*po*c^2*Sd^2/((2*PI()*Fs)^2*Mms)
where:
po = 1.21 Kg/m^3
c = 344.43 m/s
Sd in cm^2
Mms is in grams
Note that different programs tend to use different po, c values, so for best theoretical accuracy use the ones for the program.
Bottom line, you want accurate specs you'll have to measure them somehow, whether by someone else, use a woofer tester or do it 'long hand': http://www.diysubwoofers.org/measure.htm
GM
I'm sure these won't be the last enclosures for these drivers, and I was planning on handling it like you said too, so some experimentation is fine. 🙂
Makes sense now..thanks for the help! 😀
Makes sense now..thanks for the help! 😀
Member
Joined 2006
I am interested to know too, I have a same pair as well 😀
Mine have Coral 5A II, 3W nomimal, 8W max....on the back. (not sure if they are the Flat 5 II either
)
I have tentatively made some mini OBs for them....eventually with active xo to be mated with 5" woofers on hand ...
Mine have Coral 5A II, 3W nomimal, 8W max....on the back. (not sure if they are the Flat 5 II either

I have tentatively made some mini OBs for them....eventually with active xo to be mated with 5" woofers on hand ...
Haven't actually gotten mine yet, but I hope they can handle more than 3W. 😕
The auction said 92dB 1w/1m...
The auction said 92dB 1w/1m...
Member
Joined 2006
OK, so from the same Danish gentleman I suppose 😉
Check out the thread from Audioasylum, some info on the box design recommendations
Check out the thread from Audioasylum, some info on the box design recommendations

Ok..they finally got here and it turns out these are Flat 5A-II's (thanks to this Danish guy's completely inaccurate description). I don't really have the patience to go through returning these, so I guess I'll try them out.
GM, could you do your wizard thing and tell me if that Vas approximation would still be relevant? 😀
GM, could you do your wizard thing and tell me if that Vas approximation would still be relevant? 😀
Member
Joined 2006
So yours says Coral 5A II, 3W nomimal, 8W max....on the back as well?
Just tested mine recently and realized one of mine had some scratchy noise at low freqs......
Anyway, mine does look the same as Flat 5 from the front, it's just that the magnet surround is different, and doesn't say Flat 5 II, but 5A II instead...
I will be interested to know any recommendation on the box design as well 😀
Just tested mine recently and realized one of mine had some scratchy noise at low freqs......

Anyway, mine does look the same as Flat 5 from the front, it's just that the magnet surround is different, and doesn't say Flat 5 II, but 5A II instead...
I will be interested to know any recommendation on the box design as well 😀
Yep..sounds exactly like mine. They aren't a matched pair either..one says 3W nom./8W max and the other just says 8W max, but both say 5A-11 on the back. Very dirty too..need to paint over some rust. 🙁
Best guess I can come up with so far (with no info at all other than 3W/8 ohms) is a 0.38 cu. ft. (10.83 l) or bigger box tuned to <67hz, assuming Qts is 0.4 and Fs is 70hz.
But I still have no idea what I'm talking about. 🙂
Have you seen any designs for the 5A-II on Audioasylum?
Best guess I can come up with so far (with no info at all other than 3W/8 ohms) is a 0.38 cu. ft. (10.83 l) or bigger box tuned to <67hz, assuming Qts is 0.4 and Fs is 70hz.
But I still have no idea what I'm talking about. 🙂
Have you seen any designs for the 5A-II on Audioasylum?
ballsingtripp said:
GM, could you do your wizard thing and tell me if that Vas approximation would still be relevant?
...........assuming Qts is 0.4 and Fs is 70hz.
Good as any I guess based on my previous erroneous assumptions which assumes Qo = Qts, so 0.55, not 0.4. IOW, the cab I previously suggested.
GM
Member
Joined 2006
Member
Joined 2006
I have a pair of real Flat 5 II now.
The ones I got earlier as mentioned aren't exactly Flat 5 II. They have smaller magnet and coarser frame, etc, though the paper cone and cloth surround should be the same type....🙄
BTW, suggestion on the enclosure, anyone? 😀
The ones I got earlier as mentioned aren't exactly Flat 5 II. They have smaller magnet and coarser frame, etc, though the paper cone and cloth surround should be the same type....🙄
BTW, suggestion on the enclosure, anyone? 😀
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