2-way DJ subwoofer

[pikipupiba]

I started my own company that rents out DJ-ing equipment for parties and stuff.

I am building all my own speakers and am trying to keep prices low by using bargain drivers.

I have tried 2 boss subs:

Amazon.com: Boss P156DVC 15" Subwoofer Dual 4ohm Voice Coils: Electronics

Amazon.com: Boss CX15 15" Subwoofer 4ohm Voice Coil: Electronics

The first one covers the lowest of the lows and hits hard, but sounds awful in the higher bass frequencies. The second one is very melodic and can cover higher bass frequencies, but dies at the low end.

My solution to this was to make a 2-way subwoofer. I have a few plans for balancing them: (first sub is wired at 8 ohms, both subs are in separate 2 cubic foot sealed boxes as recommended by the manufacturer)

1. Standard crossover. Could get expensive with the high power parts needed. Don't have experience with many crossovers, don't really know.

2. Just connect them in series (12 ohm load). This is how I figure (and have observed) - They have different resonant frequencies. The more powerful and heavier sub has a lower resonant frequency than the lesser one. They are in series, so the current through them both is the same. Impedance reaches a maximum at resonance. Therefore, the voltage drop across the sub currently at resonance will be greater than the other one, thus each sub sort of "takes over" around its resonance point. And since the lower sub is twice the impedance on average it will get twice the power on average (remember, same current). Only problem I see with this is how to get the lower sub to stop completely in the higher frequencies, cause it sounds like crap up there.

3. Any other ideas are welcome!!!


In summary... Is this a good idea? Thoughts on my methods? Am I a moron?

[deiksac]

if you rent, people will destroy your bargain drivers rather easily. cheap is not the way in pa rental

[pikipupiba]

As of right now, I set max volumes during set-up and people pay for what they destroy, so it all works out. And my amps can't physically blow most of my speakers.

[jbell]

You're spending over $100 bucks on those 2 drivers.... wholesale a 3015lf is $110, retail about $150. By the time you add electronic crossover and amp channels to power these two drivers at different frequencies, you'll have spent more than if you just went with a single good driver.

My 2c on this. (as I've set up MANY of these systems)

Build a ss15, a pair of tops of your choice and a crown xti1000. (which you can get for $260) Every thing you need is in the crown -- dsp, delay, limiter, eq, crossover, amp. Crown has 3 year 'no fault' warranty, it's as close to monkey proof as it gets.

I also have built what I call HS12 tops using eminence beta12 and selenium compression driver.

Put the crown amp and dj mixer in a skb dj capsule, and you have a nice small light, professional dj setup that fits in a corolla's back seat.

$200 sub
$200 pair of tops
$260 crown xti
$100 skb dj capsule
$200 dj mixer of your choice
$40 cables, etc.

$1000 total out the door.

As I said, my 2c....

[pikipupiba]

I guess I omitted this part: my entire working capital is around $2000. And that has to pay for the workshop, tools, parts, amps, everything. Yes I agree that using name brands and such will provide a better and more reliable system, I simply don't have the money to buy them. Maybe once I start making some money I can, but I can't now I'm building from the ground up!

[18Hurts]

I'm with JBell on this one,

Back in the 90's during my DJ days, I was well aware of people doing crazy things with PA systems--then add alcohol. If you are going rent out PA systems in the days of everyone having songs on their phones--making it idiot proof is a must.

The XTI series of amps is a great start, they have filters (high pass) to cut out the bass the subs can't reproduce, built-in crossovers to cut the amount of components and programmable limiters to protect the speakers from being over driven. Once the safe settings are plugged in, then they are password protected to prevent being bypassed.

If the system will have a mic, then other things must be put in to prevent nuking the system. What worked for me was a compressor/limiter/gate on the microphones. The mics would automatically shut off if there was no signal (when people talk then lower the mic to their side and point it at the speaker) it would compress at 4 to 1 so when they yell into it, it would cut the signal to not overload. The compression also boosted the signal when they talked softly (or pointed the mic wrong) so it sounded much better. The limiter came into effect when they screamed or dropped the mic to prevent the signal from maxing out the inputs to the mixer. If the mixer has a 500Hz and below filter--use it!

Those "feedback destroyers" would also be a good idea on the mics. They notch out the feedback with EQ in real time--not perfect but will save your system, the crowds ears and but easier on the drunk giving announcements.

Since drunks will be screaming into the mics, make sure the vocals will be going through a driver that can handle a ton of power. The Beta12 would be great for this--cross the Selenium horn up high--around 8 KHz to keep it out of the vocal range just in case Mariah Carey stops by. Don't forget to set the limiters on the Crown amps to protect the Beta12's from getting smoked in the screaming contests. Look into those auto-resetting breakers for the Selenium horns--you have no idea what will be going through them. (mosquito 17 KHz ring tone from my phone--wonder if it works--hey! There is a mic! Watch this!)

For the mixer, mount plates with rivets over the inputs. Uncle Bob might plug his guitar into the mic inputs (it happens and it fits) Gangsta Slick will plug in his phone and play "Bass I Love You" with it's 16 Hz and 7 Hz tones to get the party going. Another person will have the latest drum and bass tune with sub 20Hz harmonics and all he needs is an input. Everyone that walks in has music on their phone and would like to hear it full blast--blast it like a rental!

Somehow the words "Inexpensive" "PA" and "rental" don't mix well together. The Crown XTI, feedback destroyers, compressor/limiter/gates, automatic resetting breakers on the horns and sealed off input ports should supply about 90% of idiot-proofing. Maybe put the amps/mixers and cables all in the same rack. Lock the back panel on the rack and the output cables can be clamped down so they can't be removed.

Good luck with your PA rental business!

[wg_ski]

Originally Posted by 18Hurts

The XTI series of amps is a great start, they have filters (high pass) to cut out the bass the subs can't reproduce, built-in crossovers to cut the amount of components and programmable limiters to protect the speakers from being over driven. Once the safe settings are plugged in, then they are password protected to prevent being bypassed.

And a solid pair of 2x18 conventional subs (in non-bridged mode). Horns are better, but I don't trust idiots with them. Use an amp that's well within the RMS rating and won't drive much beyond x-max, use a high pass, and you almost can't destroy them. My rentals are and RMX2450 with limiter and 30 Hz cut switches *permanently hardwired*, and a pair of double Omega Pro 18's tuned to 40 Hz.

For tops, a permanent high pass is a must. The XTi's are great here also. Some QSC's also have sub/top options that can be hardwired as well. Use the highest output compression driver you can possibly afford if you want to keep it. A 2" is good if you can swing $150. Then you can pad 10dB with those big metal cased heat-sinkable resistors, and by the time you get 50 watts of average power into it, the amp has long since thermalled and the "vocalist" has put down the mike.

[jbell]

Originally Posted by pikipupiba

I guess I omitted this part: my entire working capital is around $2000. And that has to pay for the workshop, tools, parts, amps, everything. Yes I agree that using name brands and such will provide a better and more reliable system, I simply don't have the money to buy them. Maybe once I start making some money I can, but I can't now I'm building from the ground up!

Did you see my price list? $1000 total (excluding tools) In fact you can afford to build a pair of subs and really have dj level bass for your $2k startup costs.

Tools,
$80 cordless drill (for screws)
$50 skill saw
$20 good carbide blade
$30 Drywall T-square
$20 couple of clamps
$10 glue gun for your tubes of PL premium polyurethane

thats it. Yea I'd rather you buy a good table saw, but then if you are on a budget, the above works. You can clamp down the T-square for a guide for the skill saw. Framers do it all the time.

As for my tops with the beta12a and selenium. I use the 16ohm selenium crossed at 1900hz -- works great, and I have no worries about it smoking before the beta12 gives up the ghost.

Here's another 'monkey proof' thing to consider. The xti has both channels on a dual pole speakon connector. Run tops on 1, subs on 2. When you build cabinets use dual channel speakons. One speaker cable from dj capsule daisy chained to all speakers -- impossible to mess that up !!


18hurts -- mosquito ring tone through pa? That's just brutal.

[pikipupiba]

But what about the other speakers? I need more than just 2 subs. I have a gig at a bar next week that needs 4 subs plus mids and highs!

[wg_ski]

Originally Posted by jbell

$50 skill saw

Yea I'd rather you buy a good table saw, but then if you are on a budget, the above works. You can clamp down the T-square for a guide for the skill saw. Framers do it all the time.

Framers use a $170 worm drive skil saw. You don't need a guide and you can operate it one handed hanging from the framing (or roofing) with the other.

Even a $500 table saw can't handle a 4x8 sheet without either help or building a big extension table. A couple of 2x4's and a worm drive on the ground and you can cut the main panels with ease. It will stay straight on (or inside) the line unless you move it - unlike the sidewinders that will try to go off in the woods.