Multiple woofers in a sealed box.

RussellW · 11th September 2010, 07:23 AM

If I put 4 of these speakers in a sealed box, What should the volume of the box be?
The box is stuffed with fiberglass.
Each speaker will be driven by an individual 100 watt rms amplifier.
Should I use a single voice coil or put them in series or parallel?

175W RMS
Dual 4 Ohms
Mounting Depth: 4.5"
Mounting Hole Diameter: 7.3"
Electrical Q Value -Qes: 0.38
Mechanical Q Value -Qms: 4.21
Total Speaker Q Value -Qts: 0.34
Free Air Resonance -Fs: 22.8 Hz
Equivalent Compliance -Vas: 27.1 liters = 0.957027468 cu. feet
One-Way, Linear Excursion -Xmax: 12 mm
Efficiency -SPL 1W/1m: 81.2 dB SPL
Effective Piston Area -Sd: 195 cm^2
DC Resistance -Re: 3.2 ohm
Force Factor -Bl: 15.4

Thank-you,
Russell

tedmich · 11th September 2010, 07:24 PM

as a rule, you NEVER run a single voicecoil in a DVC woofer; they both need juice!

Your (classD?) 4 x 100w probably likes 8 Ohms, not 2 Ohm (few do!) so definitely wire the VCs in series.

A sealed box with Qtc = 0.7 is most common and that volume would be 32.61 liters from WinISD online:
LinearTeam

Notice the ported box would give a low end response (F -3db) of 30Hz, while the (1/2 vol.) sealed will only go to 50Hz. Some do like the sound of a sealed box though.

Also many prefer different sealed box Qtc; lower for faster transients, higher (more common) for better group delay etc.

bjorno · 11th September 2010, 07:25 PM

Quote:

Originally Posted by RussellW

If I put 4 of these speakers in a sealed box, What should the volume of the box be?
The box is stuffed with fiberglass.
Each speaker will be driven by an individual 100 watt rms amplifier.
Should I use a single voice coil or put them in series or parallel?..

Hi Russel,

The TS you have submitted is for the coils in series and is IMO preferred.

I would put 4 of these drivers in a box of ~net volume of 35 L if the speaker are placed away from walls or if are to be used in a car.
If close to wall(s) I suggest a volume of 60L or more.

If you are aiming at a sub system for HT (music only too) I would design a dual driver ~56L T-TQWT and two closed boxes (~16L/box) using your 4 drivers.

b

Andrew Eckhardt · 11th September 2010, 07:36 PM

Whether the individual speaker's coil pairs should be series or parallel on each amplifier depends mainly on the design of the amplifier, because, you'll be potentially determining a difference in output power output limit by a factor of 4. If the amplifiers are designed for a 2 Ohm load you'll be wasting a lot of amplifier with an 8 Ohm load. If the amplifiers are designed for an 8 ohm load then you'll probably get the best fidelity and possibly close to maximum output power with an 8 ohm load. The response of the speakers itself will be very similar either way.

11th September 2010, 07:23 AM	#1
RussellW diyAudio Member Join Date: Apr 2009	Multiple woofers in a sealed box. If I put 4 of these speakers in a sealed box, What should the volume of the box be? The box is stuffed with fiberglass. Each speaker will be driven by an individual 100 watt rms amplifier. Should I use a single voice coil or put them in series or parallel? 175W RMS Dual 4 Ohms Mounting Depth: 4.5" Mounting Hole Diameter: 7.3" Electrical Q Value -Qes: 0.38 Mechanical Q Value -Qms: 4.21 Total Speaker Q Value -Qts: 0.34 Free Air Resonance -Fs: 22.8 Hz Equivalent Compliance -Vas: 27.1 liters = 0.957027468 cu. feet One-Way, Linear Excursion -Xmax: 12 mm Efficiency -SPL 1W/1m: 81.2 dB SPL Effective Piston Area -Sd: 195 cm^2 DC Resistance -Re: 3.2 ohm Force Factor -Bl: 15.4 Thank-you, Russell

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11th September 2010, 07:24 PM	#2
tedmich diyAudio Member Join Date: Feb 2007 Location: PDX	as a rule, you NEVER run a single voicecoil in a DVC woofer; they both need juice! Your (classD?) 4 x 100w probably likes 8 Ohms, not 2 Ohm (few do!) so definitely wire the VCs in series. A sealed box with Qtc = 0.7 is most common and that volume would be 32.61 liters from WinISD online: LinearTeam Notice the ported box would give a low end response (F -3db) of 30Hz, while the (1/2 vol.) sealed will only go to 50Hz. Some do like the sound of a sealed box though. Also many prefer different sealed box Qtc; lower for faster transients, higher (more common) for better group delay etc.

11th September 2010, 07:36 PM	#4
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	Whether the individual speaker's coil pairs should be series or parallel on each amplifier depends mainly on the design of the amplifier, because, you'll be potentially determining a difference in output power output limit by a factor of 4. If the amplifiers are designed for a 2 Ohm load you'll be wasting a lot of amplifier with an 8 Ohm load. If the amplifiers are designed for an 8 ohm load then you'll probably get the best fidelity and possibly close to maximum output power with an 8 ohm load. The response of the speakers itself will be very similar either way.