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Old 10th February 2005, 09:14 AM   #1
set is offline set  Macedonia
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Location: macedonia
Default ins and outs

Here are specs from Celestion and P Audio 18' subs, need opinion about ins and outs for both models. I’ll go for Celestion but maybe I’m wrong.And yes in case anyone wanders why, it’s solely for my X1 sub building intentions. Another reason is that j have never hard P Audio performing so j could compare them with Celestion drivers witch j have heard and use way back and must say that j am very pleased with the performance and reliability even in a extreme conditions.
------------------------------------------------------------ ------
Celestion FTR 18-4080FD
General Specifications

1000Wrms continuous power handling measured to AES Standard)
Flexirol™ technology for greater excursion control
Double suspension to further improve linearity at high excursion
Saturated gap technology for lower harmonic distortion
Extremely low frequency response, down to 30Hz
Smart chassis design minimises acoustic distortion

Nominal diameter (") . . . . . . . . . . . . . . . . . . . . . . 18
Power rating (AES, Wrms) . . . . . . . . . . . . . . . . . . 1000
Nominal impedance (Ω) . . . . . . . . . . . . . . . . . . . . . 8
Sensitivity (dB) . . . . . . . . . . . . . . . . . . . . . . . . . 97
Chassis type . . . . . . . . . . . . . . . . . . . . . . . . . . . Cast
Voice coil diameter (") . . . . . . . . . . . . . . . . . . . . . 4
Surround material . . . . . . . . . . . . . . . . . . . . . . . . .Cloth - sealed
Magnet type . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ceramic
Magnet weight (kg) . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1
Coil material . . . . . . . . . . . . . . . . . . . . . . . . . . Round copper
Cone material Glass loaded paper with weather resistant impregnation
Frequency range (Hz) . . . . . . . . . . . . . . . . . . . . . 30-2500
Resonance frequency, fs (Hz) . . . . . . . . . . . . . . . 25

Thiele-Small Parameters

Mmt (g) . . . . . . . . . . . . . . . . . . . . . 170
Qms . . . . . . . . . . . . . . . . . . . . . . . . 9.4
Qes . . . . . . . . . . . . . . . . . . . . . . . . 0.26
Qts . . . . . . . . . . . . . . . . . . . . . . . . 0.26
Re (Ω) . . . . . . . . . . . . . . . . . . . . . . . 5.4
D (m) . . . . . . . . . . . . . . . . . . . . . . . 0.39
Vas (L) . . . . . . . . . . . . . . . . . . . . . . 445
Bl (Tm) . . . . . . . . . . . . . . . . . . . . . . 23.6
Cms (mm/N) . . . . . . . . . . . . . . . . . . . 0.23
Rms (kg/s) . . . . . . . . . . . . . . . . . . . . 2.87
Xmax (mm) . . . . . . . . . . . . . . . . . . . . 6.0
f/p (mm) . . . . . . . . . . . . . . . . . . . . . 10.0
coil (mm) . . . . . . . . . . . . . . . . . . . . . .22.0
Mounting Information
Diameter (mm) . . . . . . . . . . . . . . . . . 452
Overall depth (mm) . . . . . . . . . . . . . . . 205
Cut-out diameter (mm) . . . . . . . . . . . . 416
Mounting slot dimensions (mm) . . . . . . . 7 x 11
Number of mounting slots . . . . . . . . . . . . 8
Mounting PCD range (mm) . . . . . . . . 429 - 440
Unit weight (kg) . . . . . . . . . . . . . . . . . . 9.8
Packed Dimensions and Weight
Single pack size W x D x H (mm) . . . . . 500 x 500 x 240
Single pack weight (kg) . . . . . . . . . . 11.6

------------------------------------------------------------ ---------
P Audio SD 18



Description
HIGH POWER BASS
Size (in.) 18.0
Nominal Diameter (mm) 460
Colour Blue
Standard Impedance (Ohm) 8 Ohm
Power RMS (Watts) 800
Power Program (Watts) 1600
Sensitivity 1w/1m (dB) 98
Frequency Range (Hz) 30-1500
Basket Material Die cast aluminum
Cone Material Paper
Poles Material 1008 Cold Roll Steel
Gasket Material EVA
Magnet Material Ferrite
Magnet Weight (Kg) 3,07
Surround Material Treated cloth
Voice Coil Material Anodized CCAW
Former Material Glass fiber
Voice Coil Diameter (in.) 4.5
Spider Material Treated cotton
Terminals Type Gold Plated Push
Copper Shorting Ring Yes


Fs (Hz) 33.2
Re (Ohm) 5.1
Sd (sqmt) 0.125
Qms 7.11
Qes 0.27
Qts 0.26
Vas (lt) 264.3
Mms (gr) 192.1
Bl (T/m) 27.5
Xmax (mm) 5.0
Xmax Peak (mm) 30.0
Le (mH) 1.95
Levc20 KHz 0.7
Rem1 KHz 7.91
Rem 20 KHz 68.56
Mmd 166.7
Erm 0.72
Exm 0.65
Hvc (mm) 25.0
Hag (mm) 16.0
Cms (µM/N) 119.1
N0 (%) 3.42
Krm 14.5
SPL0 (dB) 98
Kxm 38.74


Net Weight (kg) 15.32
Gross Weight (kg) 16.8
Pieces per carton 1
Volume (cuft) 2.57
Dimensions (cm) 51x51x28
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Old 11th February 2005, 04:17 AM   #2
simon5 is offline simon5  Canada
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The Celestion is better overall IMHO, lower Fs so better performance down low. Excursion is also a bit better.

The P Audio driver can work better in a smaller box than the Celestion, the rolloff is a bit shallower.
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Old 11th February 2005, 09:10 AM   #3
set is offline set  Macedonia
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Smile Importance of a FS and EBP

Could someone explain me what is the connection between FS and EBP . I’m sure that this question will sound stupid to someone who is familiar with the subject but since I’m still learning j would appreciate help on this topic.
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Old 11th February 2005, 02:01 PM   #4
simon5 is offline simon5  Canada
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Fs is the low frequency resonance of the driver. If the Fs is low, the woofer will be able to go lower in frequency than a woofer with a higher Fs.

EBP is the Efficiency-Bandwidth-Product
EBP = Fs / Qes
If EBP is higher than 50, better in a vented box. If lower than 50, better in a sealed box. If around 50, it will do well in each enclosure. This is only a rule of thumb, it's not an absolute rule. You can put a EBP 80 driver in a sealed box if you want to.
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Old 12th February 2005, 10:44 AM   #5
set is offline set  Macedonia
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Hi Simon the information you have provided is helpful but there is one thing that puts lot of confusion in all this and that is that most of the comments go in a direction of a motor strength BL that as j understand is of high importance when choosing driver for this cabinet, and for that meter for all cabinets, especially when extreme power and reliability is needed. Everything would be jus fine if it is a general rule but various designers have various opinions of this. J was wandering if BL is in direct connection with amplifier power and if so how. The EBP factor depending of an approach to the problem is also questionable because it was denied number of thymes that higher EBP is better and there are a number of designs proving that, Bob Carvers designs using low EBP drivers for example.
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Old 14th February 2005, 05:07 AM   #6
simon5 is offline simon5  Canada
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BL is the strength of the magnet. If BL is higher then the magnet is stronger.

I would not choose a woofer based on BL alone... maybe someone with more experience than me could step into this conversation.
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Old 14th February 2005, 08:01 AM   #7
set is offline set  Macedonia
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Thanks I’ll do some more research and try to connect all factors together and see what comes out of that , than J will decide what to do next. Since time is not of essence I’ll try some of the cabinets with the drivers j have and keep on with the posts in case anyone is interested. Quick question on the end do you have any experience in measuring techniques of the finished cabinets, SPL, impedance and other factors.
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Old 16th February 2005, 12:31 AM   #8
simon5 is offline simon5  Canada
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To measure finished cabinets, you need a SPL meter or a microphone, a computer with a tone generator and a multimeter.
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