Following the lead
After watching 123Toid’s / Toid’s DIY video: https://youtu.be/CvUjWNwPHDU
I thought to myself, what else could I possibly be dismissing on single driver performance?
Well, just for fun I stopped by PE’s Home Subwoofer page and did as I always do, Sort from Cheapest. First thing that pops up is the Goldwood GW-406D, a 6-1/2″ poly sub that is currently on sale for $12.13 USD. That’s pretty darn cheap. And looking at the rest of the specs, you’d probably dismiss them without a thought – 16 Ohm, 85dB @2.83V, 60/90W, 2mm excursion – not the most promising. As I’ve said before, you need to read into the specs rather than just gloss over things. Let’s break it down.
16 Ohm and 85dB@2.83V. These NEED to be taken together. What you are looking at is 85dB @ 1/2 W. 2.83^2=8.0089/16=0.500556W. In order to get it up to 1W, you’ll need to be pushing 4V, which would put it up at 88dB +-.
Ok, so you need more power, a minus right there.
But wait! there’s MORE!
Is there a way to wire them up to get 8 Ohms or something else? Well, 4 in parallel would be 4 ohms and 8 in a series / parallel combo would get 8 ohms. 4 Ohm ~91dB @ 1 W and 8 Ohm ~88dB.
4 drivers – 1.87 cu.ft. box, 3″ port @ 4-3/4″ long, Fb & Fp 38Hz, F3 30 Hz, 240/360W
8 drivers – 3.74 cu.ft. box, 3″ port @ 1-1/4″ or 4″ port @ 3-1/4″, Fb & Fp 38 Hz, F3 30 Hz. 480/720W
Of course, this is in the same style as the video, Isobaric / Compound configuration.
Ok, what does all this mean? This is something I learned a long time ago from a guy in the PA business – doing sound for State Fairs and Country music acts – he’d take 4-10″ or 4-12″ over 1-15″ any day as they’d hit harder (faster) and generally deeper. The more voice coils you can combine the better. So what that translates to is that each speaker (or combined speaker) has to move less to make the same amount of air be moved. Here’s the hypothetical math: let’s say that at a certain power a driver moves 1mm and displaces X amount of air. Now you place another driver on the same face right next to the first. you now have 2x’s the cone surface, so each driver only needs to move 1/2mm to displace the same X amount of air. If you put 4 on the same face, then that’s 4x’s the cone surface and each only has to move 1/4mm to displace that exact same amount of air. Not necessarily intuitive, but when you think about it, extremely simple to understand.
What would I do? Well, at that price, they’re almost worth trying either a pair of 4 drivers or a single 8 driver. 4 = $48.52, 8 = $97.04.
Fun exercise in thought, and that’s just with the first driver that comes up. I haven’t even looked at anything else yet.
*PS – I did a quick check of just putting 2 in a box like the video, and you get a 0.94 cu.ft. box, 2″ port 4-5/8″ long, same Fb, Fp, F3, and 120/180W @ 8 ohm. Total $24.26 That’s intriguing too! Hmmmm…
**PPS – Fb = Fbox, Fp = Fport, F3 = -3dB point.