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Hi-Eff loudspeakers
system INTRODUCTION
This project born to create a loudspeaker
with very high efficiency and low cost to be driven by low power single ended
amplifier with one or two 2a3 (SE or PSE). |
HIGH FREQUENCY
To limit the cost I have decided to use 1" driver with an 800Hz-1KHz crossover. |
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Follows the first measurements of CP380M loaded by the cf600 horn at 1m.
I have used in all the measurements the Clio system by Audiomatica with the Transit by M-Audio to use the USB port of my portable pc (instead of the PCI audio board).
A very flat response in the band 800Hz - 20KHz.
LOW FREQUENCY
Now about the woofer we need a 15" with:
- linear frequency band until 3-4KHz to prevvent problem after the crossover
frequency
- moving mass no more than 90
gr to be fast
- sensitivity near to 100dB to be drivven with low power amp. like 2a3
single ended
- low
resonant Frequency, near 35Hz, to have a good bass
frequency band
-Thiele-small parameters to be fit in a max 150lt reflex or sealed box to be fit
in my room
- An high min impedance value to get the mosst high system impedance to be easy
to drive
Beyma
15MW Nd
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not very
good linearity Fs=42Hz (a little high) Sensitivity =96-99dB (good)Mms=90gr (good) Min. Imp = 5.8ohm |
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Beyma
SM115N |
not very
good linearity Fs=29Hz (a little high) Sensitivity =95-99dB (low)Mms=77gr (good) Min. Imp = 7.4ohm
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Beyma
15LW30 |
good linearity Fs=32Hz (good) Sensitivity =95dB (low)Mms=83gr (good) Min Imp=7ohm
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Beyma 15P80Nd
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good linearity Fs=35Hz (good) Sensitivity =100dB (good)Mms=99gr (a little high) Min Imp=6.2ohm |
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B&C
Speakers 15NDL76
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good linearity Fs=37Hz (good) Sensitivity =98dB (good)Mms=96gr (a little high) Min Imp=6.7ohm |
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B&C
Speakers 15PH40
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good linearity Fs=38Hz (good) Sensitivity =97dB (good)Mms=72gr (good) Min Imp=7ohm
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RCF
L15-554K
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bad linearity Fs=35Hz (good) Sensitivity =97dB (bad)Mms=91gr (good) Min Imp=7.9ohm |
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Faital PRO
W15N8-350 |
good linearity Fs=32Hz (good) Sensitivity =98dB (good)Mms=85gr (good) Min Imp=5.9
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Eminence
OmegaPro 15A
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bad linearity Fs=33Hz (good) Sensitivity =97dB (little low)Mms=94gr (a little high) Min Imp=6.5ohm
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Celestion FTR15-3070C
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good linearity Fs=40Hz (good) Sensitivity =97dB (good)Mms=70gr (good) Min Imp=8ohm
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Monacor IMG Stage Line
SP-38/300NEO |
good linearity Fs=36Hz (good) Sensitivity =101dB (good)Mms=71gr (good) Min Imp=7ohm
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Monacor IMG Stage Line
SP15A/402PA |
medium linearity Fs=36Hz (good) Sensitivity =101dB (good)Mms=87gr (good) Min Imp=8.5ohm
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these should be the best:
- Monacor IMG Stage Line SP-38/300NEO
- Monacor IMG Stage Line SP-15A/402PA
- Beyma 15MW Nd
- Beyma 15P80Nd
- Beyma 15PH40
-
Celestion FTR15-3070C
- Faital PRO W15N8-3500
- B&C15NDL76
Now I am will try to simulate these in a standard bass-reflex box for the best
alignment using WinISD (free beta pogram)
good result for:
-
SP-15A/402PA to get the best
sensitivity
- W15N8-350 compact box and
good bass freq.
- 15MW Nd enough bass frequency and goood
sensitivity
- Celestion
FTR15-3070C good bass and good
sensitivity
-
15PH40 good bass and
good sensitivity
less good result for these:
- SP-38/300NEO too large box necessary
-15NDL76 too bad low frequency band
-15P80Nd bad low frequenccy band
- 15LX30 low sensitivity
Follows the bass frequency simulation with
Onken spreadsheet by Cyr-Marc Debien 2000 ©
cdebien@cmaisonneuve.qc.ca.
After original research from M. Eijiro Koïzumi and Jacques Mahul and Jean Hiraga
calculations.
model | volume | dB 1W/1m | F(-3db) | |
Beyma 15LW30 | 166 | 97.3 | 44.6 | |
Beyma 15MW Nd | 164 | 96.7 | 43.0 | |
Beyma 15P80 | 68 | 98.0 | 63.7 | bad bass frequency |
Beyma SM212 | 139 | 95.5 | 41.9 | low sensitivity |
Monacor SP15A/402PA | 158 | 97.1 | 44.6 | |
Monacor SP38/300NEO | 361 | 96.3 | 32.7 | too large box |
Faital PRO W15N8 | 177 | 96.8 | 42.3 | |
B&C 15PH40 | 183 | 97.6 | 44.3 | |
B&C 15NDL76 | 67.3 | 97.8 | 63.3 | bad bass frequency |
Celestion FTR15-3070C | 163.4 | 97.0 | 43.4 |
So now are 6 the best woofer selected for this project.
The price is a factor to consider because this project born to be cheap so probably I will buy a pair of Celestion FTR15-3070C available for few money at Lean shop only £99.95 (normal price in US is about 220-245$ and in UE about 220-250 euro).
From Celestion website: Designed for high-end sound reinforcement applications, Celestion FTR aluminium chassis, Ferrite magnet drivers feature a Smart Chassis Design and wet wound Inside/Outside Voice Coils for efficient cooling, reducing thermal compensation and minimising distortion. Exceptional BL and stiffness (K) symmetry further contribute to low distortion, while FEA-optimised magnet topology reduces inductance, also minimising distortion. The FTRs use water-resistant, glass fibre impregnated cones with sealed surrounds and added damping for reduced cone resonances. FTR-HDX drivers are among the lightest in their class |
Follows the simulation of the bass reflex for the best alignment using WinISD and Onken configuration (larger box)
Follows the final Onken box design
I have selected 30 millimeter birch plywood for the cabinet in order to raise cabinet resonance to a point well above the radiated frequencies.
Follows the measued impedance on air and the measured Thiele-Small parameters
9gr
FS 44.4072 Hz
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78gr
FS
44.4072 Hz QMS 3.1876 QES 0.5349 QTS 0.4580 B×l 51.2330 T×m dBSPL 85.6450 SD 0.0804 m2 CMS 0.0156 mm/N MMS 824.8739 g RMS 72.2028 WM CAS 1.01E-0007 m5/N MAS 127.53 kg/m4 RAS 11163 WA CMES 314.2594 mF LCES 40.8739 mH RES 36.3534 W RAT 77689 WA RMT 502.5008 WM MMD 811.9647 g ZMIN 7.3081 W ZMAX 42.4534 W ZAVG 16.6360 W h0 0.2211 % L1kHz 0.7112 mH L10kHz 0.3356 mH |
15g FS 44.4072 Hz VAS 196.0080 L RE 6.1000 W QMS 3.1876 QES 0.5349 QTS 0.4580 B×l 13.7238 T×m dBSPL 97.0865 SD 0.0804 m2 CMS 0.2170 mm/N MMS 59.1887 g RMS 5.1809 WM CAS 1.40E-0006 m5/N MAS 9.15 kg/m4 RAS 801 WA CMES 314.2594 mF LCES 40.8739 mH RES 36.3534 W RAT 5575 WA RMT 36.0569 WM MMD 46.2795 g ZMIN 7.3081 W ZMAX 42.4534 W ZAVG 16.6360 W h0 3.0807 % L1kHz 0.7112 mH L10kHz 0.3356 mH
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For this purpose I have used www.officinelettroniche.it of Ivan De Cesaris.
Are necessary 250 euro for the chassie and 240 euro for the wood + tax.
For this large
loudspeakers it is impossible use the normal damping articles for loudspeakers
because in this case the cost would exceed the cost of wood.
Following the suggestion of my friend Andrea of
PuntoMusica
I have used two different damping materials used in the cars:
1)
panels composed of fabric processing residues bottom tar
for the base and the back
2)
moquette
with
longhaired and
bottom in lute