Guidance reqd for DIY with Fredo 12" DVC driver

[RaahulT]

Hi All.
I have started to build a ported sub with Fredo driver. I know there are better drivers available but since there is nothing for this driver from DIYers in this forum, I decided to go ahead. Driver has been ordered. Presently, I am in calculations stage. I am a novice with an urge to do things myself.

Power rating of driver:

• Nominal power (Single coil) = 275 Watts.
• Max continuous power (Single coil) = 825 Watts.
• Spike power tolerance (Single coil) = 1375 Watts.
• RMS power (Single coil) = 195 Watts, effective Impedance 4 Ohms.
• RMS power (DVC wiring in parallel) = 400 Watts, effective Impedance 2 Ohms.
• RMS power (DVC wiring in series) = 100 Watts, effective Impedance 8 Ohms.

Driver TS as per manufacturer:

• Resonance Frequency Fs = 25.83Hz
• Qms (mechanical) = 6.93
• Qes (electrical) = 0.45
• Qts (Total) = 0.422
• BL (motor strength) = 15.39 Tesla Meter
• VAS = 87 Liters
• Sd (diaphragm surface area) = 506.45 sqCm
• Voice Coil dia = 2 inches + 2 inches

Manufacturer recommended enclosure size:

• Minimum face = 33cms (subwoofer fitting side of box)
• Dimensions (as measured sitting inside box) = 33 x 51 x 52 cms
• Air Volume = 87 Litres
• Compensate for MDF/Box width (example 11mm, makes external dimensions 35 x 53 x 54 cms, keeping 87 Litres volume)
• Port dia = 2 inches
• Port Length (hidden inside box) = minimum 4 inch

I find this size to be like fit for all info. So I tried to arrive at a different size through online calculators.
Dont know how, but speakerBoxlite provided results which appeared to be acceptable if box size is in between 140 litres to 175 lites. (I have space to keep bigger too). 2 nos x 3" circular ports running for 12" length.
I have one chance at building the box of fairly correct size. Need advice for ascertaining the right approach.

DIYers/Experts are requested to advice so that the Fredo can be tested for its claims.

 

[Decadent_Spectre]

Eyeballing the specs have you considered sealed?

Also try simulations in WinISD.

Edit : Also please post Re.

 

[RaahulT]

Eyeballing the specs have you considered sealed?

Also try simulations in WinISD.

Edit : Also please post Re.

Hi.
Not considered sealed enclosure yet.
Regd WinISD I will try to simulate with it.
Re not available. That need to be checked once the driver arrives.

 

[Decadent_Spectre]

It would be easier if they provided a complete T/S.

How many drivers are you thinking about? What amp? Budget?

Is this for movies or music?

 

[RaahulT]

It would be easier if they provided a complete T/S.

How many drivers are you thinking about? What amp? Budget?

Is this for movies or music?

I delved further into equations part and managed to do some calculations for TS parameters. And box design. I will cross check with winISD.

Presently thinking about single driver as it's a DVC and can be world in 3 combinations. Adding one more will be complicated for me. Still pl share your opinion for multiple drivers too..

Amp is a made to order amp with appx 300 watt. I got one more amp for subwoofer having two channels 300 watts each.

Budget: No issue

Strictly for Movies.

Thanks for your consideration.

 

[Decadent_Spectre]

Enter what you have in WinISD based on the online guides, some parameters should auto calculate.

Multiples have the regular benefits, smoothing,output etc. If you have the amp and budget, why not?

Sorry if I missed this but what is Xmax? And Xmech?

For movies I think you might like a ported cab tuned to 20Hz or so.

 

[gp_freak]

I had the Fredo Sub included in my comparison for modeling 12 inch subs. I am not sure whether i posted the results here in the forum or it lies in my laptop. Will check and let you know

Subwoofer Driver Selection for DIY - Home Use

Hello members, it's been a long time! I always wanted to build a sub to compliment my Puny Home theatre setup, but never found the time. Now with this work from Home scenario and me moving back to my hometown to my ancestral home, have a bit of time, space for DIYing, and also space for the...

www.hifivision.com

I dropped the fredo sub !

 

[RaahulT]

Xmax 25mm Xlim 28

I had the Fredo Sub included in my comparison for modeling 12 inch subs. I am not sure whether i posted the results here in the forum or it lies in my laptop. Will check and let you know

Subwoofer Driver Selection for DIY - Home Use

Hello members, it's been a long time! I always wanted to build a sub to compliment my Puny Home theatre setup, but never found the time. Now with this work from Home scenario and me moving back to my hometown to my ancestral home, have a bit of time, space for DIYing, and also space for the...

www.hifivision.com

I dropped the fredo sub !

I went through your posts in the thread. Results for fredo was not there. It will be useful for me.

Enter what you have in WinISD based on the online guides, some parameters should auto calculate.

Multiples have the regular benefits, smoothing,output etc. If you have the amp and budget, why not?

Sorry if I missed this but what is Xmax? And Xmech?

For movies I think you might like a ported cab tuned to 20Hz or so.

Xmax is 25mm.

I applied the parameters in winISD and another excel sheet available online.
Box Volume and other calculated results are in order for both but recommended port length is not matching. That's where I may need to try out with different lengths and find out which appears best to my ears.

 

[RaahulT]

Full TS parameters:
Qms: 6.93, Qes: 0.45, Qts:0.422, Qtc=0.538
Vas: 87 L, Vb: 110 L (Keele), 100 L (Small margoli)
Vdmax: 1.266 L
BL: 15.39, EBP: 57.4, rho: 1.2009, Mpow: 7.567
Fs: 25.83, Fc: 32.93, Fb: 24.607
Sd: 506.45 sqcm, Xmax: 25 mm
Le: 4.24, Les:56.609,
Re:4.136, Rme: 57.265, Res: 63.6966 Rms: 3.71844
mms: 158, ces: 0.2391
alpha: 0.95 to 0.97, gamma: 96.963
Df: 1.1848

 

[Decadent_Spectre]

The difference between the xmax and xmech is low, also the motor is weak, sealed makes most sense IMO. Try simulating in WinISD where excursion does not exceed 22-23mm with the available power input. That would be my suggestion.

 

[Kannan]

Full TS parameters:
Qms: 6.93, Qes: 0.45, Qts:0.422, Qtc=0.538
Vas: 87 L, Vb: 110 L (Keele), 100 L (Small margoli)
Vdmax: 1.266 L
BL: 15.39, EBP: 57.4, rho: 1.2009, Mpow: 7.567
Fs: 25.83, Fc: 32.93, Fb: 24.607
Sd: 506.45 sqcm, Xmax: 25 mm
Le: 4.24, Les:56.609,
Re:4.136, Rme: 57.265, Res: 63.6966 Rms: 3.71844
mms: 158, ces: 0.2391
alpha: 0.95 to 0.97, gamma: 96.963
Df: 1.1848

The effective bandwidth is 57.4, so sealed is a far better option than bass reflex.
If you plan to parallel in DVC then at 2 ohms you will need a very capable amplifier that can handle 1 ohm loads.
At 2 ohms, go with pro audio monoblock amps that can pump around 600 to 700 watt RMS or you can also look at high power car audio monoblocks from Hertz, JL Audio, Kicker, Pioneer, Alpine etc.
Sealed box, 65 - 75 liters should be enough.

If you are keen on ported or 2nd order band pass for the low end extension, my suggestion based on the available parameters is 120 liters including driver displacement.
Single 9 inches (4 inch dia) to 12 inches (3.5 to 4 inch dia) dual flared port depending on enclosure depth for ported.
2nd or 4th order band pass enclosure will need more complex arrangement.

 

[RaahulT]

At 2 ohms, go with pro audio monoblock amps that can pump around 600 to 700 watt RMS or you can also look at high power car audio monoblocks from Hertz, JL Audio, Kicker, Pioneer, Alpine etc.
Sealed box, 65 - 75 liters should be enough.

If you are keen on ported or 2nd order band pass for the low end extension, my suggestion based on the available parameters is 120 liters including driver displacement.
Single 9 inches (4 inch dia) to 12 inches (3.5 to 4 inch dia) dual flared port depending on enclosure depth for ported.

Hi. Thank you so much for your inputs which clarified some of my doubts.

I am planning to power two coils with two inputs (LR) from my sub amplifier which is apparantly capable of 300w+300w. Allowed impedance is 4 to 8 ohm. Hopefully this should drive it well.

If I go for ported at 120L volume will it likely to significantly affect quality offered by sealed of 75 lit?

 

[Kannan]

I am planning to power two coils with two inputs (LR) from my sub amplifier

Do not do this without proper equipment as gain matching is critical and you will not gain any additional power. There could even be phase cancellations leading to very poor quality output.

Wire them as DVC and power from a single amp would be my suggestion.

 

[RaahulT]

Fredo arrived about two weeks ago.
Meanwhile tried my hands at woodwork for enclosure. But it doesn't appear to be my cup of tea. So a local carpenter is tasked to do the job for sealed box of appx 80 lit as suggested FM @Kannan .
Box should be ready in a weeks time.

 

[Bordoloi]

Fs of 25Hz seems doubtful for this driver. I believe you need to measure the parameters on your own

 

[RaahulT]

Fs of 25Hz seems doubtful for this driver. I believe you need to measure the parameters on your own

Yes I also doubt the same.