I have a home theatre audio system that the subwoofer is a sealed box, 1'w X 2.5'h x 2'd, speaker mounts in the center of the 1'x2.5'side. The box made from 1" thick particle board covered in the blue fuzzy material. The box has an inernal baffle that separates the speaker cavity from the rear terminal. There is dense acoustic foam material inside. The box alone weighs about 70 pounds and typically car audio use. There is no cross over network.
The old driver speaker is a 4 ohm "Thruster" purchased about 12 years ago. Since my amp can only handle an 8 ohm load I've installed a 4 ohm series resister in series located on the negative side in the enclosure.
My old Thruster has been buzzing for quite a while under heavy load and today bought a replacement, which is a Lightning Audio 10" 300w peak 35-100hz.
Thruster provided satisfactory results, I don't require a powerful chest massage but need to hear the low Hz's. My question for you guru's:
1. The subwoofer will be required to get reasonable performance in a 24x28 room, lots of furniture, book cases etc to break standing waves. Did I buy the right speaker? 2. I understand my 4 ohm current limiting resistor is absorbing energy. Is there a better way? Do they make a crossover that will provide the impedence match? Are they hard to find? I MIGHT be able to squeeze a 2nd speaker in the enclosure but it would look cramped.
My equip: This is kind of a rag-tag collection I know but acutally sounds quite nice: *SS (Surround Sound) rack mount Dolby processor 5 channel w/subwoof line outs *1970 Vintage Kenwood 150watt/ch power amp driving (2) 1970's vintage JBL large bookshelf front speakers (Original) *1980's Sansui 100watt/ch driving (2) rear surround speakers *1980's Pioneer 200watt/ch power amp driving the subwooffer and center speaker
Obviously a very limited budget, thanks Steve
dwsw
Unregistered guest
Posted on
Your best choice for a woofer would have been a 4 ohm dual voice coil, which would have allowed you to series the coils for an overall 8 ohm load. The 4 ohm resistor you installed will protect your amp, but as the frequencies go lower, the resistor will present higher losses, which is opposite of what you want here. If you have room for a second driver, you could put both of them in series, and effectively have an 8 ohm load for one channel of your amp. (make sure your polarities are + - + -, or they will be out of phase with each other. Your Home theater room is a large one, but 200 watts ought to make a decent impact if your drivers and enclosure are fairly efficient. Where do you plan to locate the SUB, mine are in the back of the room due to lack of space up front. They say that the sub can be placed anywhere in the room, but I feel strongly that it makes a greater impact if they are located near or even under the front L&R speakers. Good luck & have fun.
Thanks dwsw for the quick response. I was mistaken about the blown speaker brand, it is a 10" Kicker, not that it matters much at this point.
Thanks for the info on the resistor. I didn't realize it absorbs mainly low HZ energy.
My sub is in the back of the room for same reason as yours. I had it firing to the floor for years until it began to buzz, bottoming out I suppose. Then turned it toward the listening area to "baby" it w/less power but it doesn't sound the same.
I believe my best bet is to put my new 10" into the existing cabinet by itself and remove my current limiting resistor. Then add a 2nd 4-ohm satellite sub closer to the front and wire in series as you describe. Who knows with a 2nd sub located opposite in the room with multiple placement opportunities perhaps I can experiment with controlling standing waves.
dwsw
Unregistered guest
Posted on
Sounds like you've got a good plan. I've got twin subs, and its a lot of fun. The more surface area of woofer you have, the less they have to work to produce the same sound, and the bass seems more difficult to localize, which is what you want. I think it better fills the room with sound also. FYI, to give you an idea of just how much power it takes to drive bass. Bag End claims that the sound pressure of a sub at 95 hz with 1 watt of power, would take 400 watts to produce that same sound pressure at 8hz. That is why you need to get away from the resistor. As the frequency goes lower, the AC impedance of your drivers goes lower, and the series resistor will begin to be the predomonant impedance in the circuit, which means it will absorb more and more energy as the frequencies go lower. Keep your speaker wire a little heavier for the subs, I recommend a 14 gauge or heavier, especially if its a long run to the back of your room, but don't spend a ton of on Monster, its not worth it. If you have a Menards, they have a decent choice for half the price of Best Buy.