BLI PA's sound

[Cajonpassfan]

Help!
The recent BLI PA's come with Paragon 2 sound decoder and a single 50 Ohm speaker. I'd like to supplement the sound with another, larger 50 Ohm speaker, in the dummy B-Unit, to help with low end response. I've done this with other installs and really like the sound. Unfortunately, I've been unable to find any 50 Ohm speakers in the size I need...say 14x24 to 16 x30. Any advice or creative thoughts would be appreciated.
Regards, Otto K. [ Guests cannot view attachments ]

[peteski]

That might be tough to find.  Why not use an array of smaller speakers. WIth smaller speakers the total area of the speaker cones will be equivalent to a larger speaker.

For example, 2 100 ohm speakers in parallel. or 2 25 ohm speakers on series (or something along those lines)?

[Cajonpassfan]

Well, the whole point of this is to use a BIGGER speaker in the unpowered dummy to get some lower end frequencies. I don't need more volume, I need more BASS....

[peteski]

I'm not an acoustical engineer but wouldn't combined area of all the speaker cones move more air (giving you that bass sound)?  Bose 901 speaker produces lots of bass and it is an array of smaller speakers (no giant woofer).

[wcfn100]

I'm not an acoustical engineer but wouldn't combined area of all the speaker cones move more air (giving you that bass sound)?  Bose 901 speaker produces lots of bass and it is an array of smaller speakers (no giant woofer).

No giant woofer but a bass reflex port at the rear front. 



Jason

[peteski]

Still, it is the volume of air moved by the array of smaller speakers which exits through the tuned port.  Since sound waves do not scale, tuned port would not work (for low frequencies) in a small model. But even if the speakers are in a sealed enclosure (in N scale model), the total volume of air moved by an array of small speakers will be equal to a larger speaker with the same cone area.  That is how I see this applying "Peteski's logic"  (as a non-expert in acoustics).

[Cajonpassfan]

Well, I did ask for creative thoughts, didn't I?...thanks guys!
I guess I'm looking for a simple solution, just dropping the largest available speaker, with enclosure, into the available space, say 16x30mm. I  don't understand why Paragon 2 uses such an odd (50 Ohm) impedance and why other 50 Ohm speakers in this range don't appear to be available.... Maybe just using another identical speaker, such as the one that comes in the A unit, would help, doubling the amount of surface...
Otto K.

[peteski]

50 ohm speaker is a bit of an oddball.  Why use it?  I imagine because of the lesser current draw for the same wattage.  Lower impedance speaker would need more current to produce the same volume of sound (with lower voltage across it). Since the amplifier is powered with 12V, the voltage difference of 12 volts minus what is across the speaker leads would be wasted as heat by the output transistors of the amplifier. But with a higher impedance speaker the current is lower so the amplifier components can be made smaller and dissipate less heat.