Karaoke Forums

I am looking to add a sub to my tops for some low end.. Here is what I want to do. I want to get a hold of some jl w6's throw them in a isobaric type designed box, and choke the crap out of them.

My question is this... I have heard people say that this is not good because those speakers are not built for live sound, but I digress. All I am using them for is bass, so does it really matter that much? All it is doing is providing the 50hz or so and below...

I am not the pro, you guys are. Does this sound viable?

What about using a real sub cabinet?

Isoberic subs are designed more for car stereo in db competitons to get the lowest bass response, but are not really designed for 'live' sound use which karaoke is 50% since live vocals are incorporated.

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Professional sound providers brickwall their subs at 40 hz. Anything lower than that runs the risk of voice coil damage due to going beyond their excursion limits.

What you really want out of your subs is the most decibels you can get between there and around 85. That's why most of us use front loaded cabs. It's the most practical way of getting there in a box that can be moved about easily.

I'm not a pro sound provider either. Just a musician/ KJ. But there are plenty of forums to lurk about in that specialize in this sort of thing if you want to hear from the serious guys in the field.

well, maybe not an isobaric design, and I wouldnt mind front facing. I guess the point is, that in order to get a good bass speaker for "live " sound, I have to spend 600+, and I can put 2 15in jl audio subs in a box, choke them down to 50hz - 65hz and just run lows through them off my amps. This will cost me half of what 1 JBL will run me.

I picked up a pair of 18-inch subs at a pawnshop (Yamaha I believe they are - haven't used them in a while) for $400. If you are diligent, you may be able to find them used through Craiglist (don't know where you are, but CL is very active in Seattle area) and check our all the pawn shops wherever you are. (I picked up most of my drum set through pawn shops - fabulous set, probably paid half of what I would have to pay new.)

Things are probably going to get even worse for a lot of people financially and for some reason people let go of their musical equipment first.  :shock:

k

Except you are using subs that aren't designed for live PA use, you could get them to work but could possibly blow them with the volume levels that they will encounter & live vocals that are raw signal as opposed to what they were designed to reporduce - compressed signals (cd/radio/etc,).

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So if I played just music through it, and did no live sound type stuff, then it would work? I think I am getting the picture. Thanks guys!

If you only played the music through the subs & had a separate amp/speaker for the vocals, then yes it may work fine.  But it also may sound a little weird because the vocals are going to be coming from a different source!

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look around. you can find good 18s pretty cheap..  you can buy GOOD drivers for less than what those jls cost.. eminence drivers are cleaner than most anything on the market and can be had really reasonably EVs are sometimes around at a good price also. they are even better and require less power than a JBL.  the true sound will depend on the cabs but most any live audio sub will work better for you than a car speaker.

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the voices arent real, but they have some good ideas

Eminence makes a wide variety of drivers... everything from very cheap to pro touring levels. I wouldn't go any lower than their Omega line for an 18" sub.

In an 18" sub look for a speaker with at least a 4" voice coil and Xmax of at least 4.5mm (the distance a voice coil travels before leaving the magnet gap). Getting this info usually means going online and getting the manufacturer's technical specs. The longer the Xmax the less efficient a driver is, so there's a trade-off there and you don't want that figure to be too high.

Peavey subs are great if you're looking for something on the low end of the price scale. You can often scrounge them up cheap used.  Their Low Rider 18s are terrific speakers, but their budget 18 is not bad and within the above specs.

Do the subs usually come with a crossover built in, or do i have to buy one of those? Thanks again!

Please be careful with generalized statements, they can be very misleading, especially to those that are just learning.
The first things I take into consideration when selecting a speaker are:
1) Nominal Impedance: Ohms, Resistance
2) SPL: How efficient a speaker is
3) Power Handling Ability
4) Frequency Range
5) XMAS: voice coil travel
For Example: Four popular speakers compared  
                       Nom Imp  SPL   PWR      Range         XMAS
Omega Pro18A          8      97      800      40-800        4.8mm
Peavey Low Rider      8      97.3    800      25-1000      9.6mm
JBL 2241H                 8      98       600     30-3000      7.6mm
EV EVX180B              8       98     1000     20-2000      6.4mm

As you may have noticed a high XMAS value doesn't necessarily mean a less  efficient speaker (SPL Value)There are a few other specs that come into play for me, but these are the top five I look at. Also, you may have noticed that the JBL does not, in fact, require more power than the EV. The bottom line is, as others have suggested, get the speakers that fit the application they are intended for. As Bill has previously mentioned, the lowrider equipped bottoms are probably the best bang for the buck subwoofers out there. Some subs do have a low pass filter built in, you'd have to read the specs. The Peavey PV118 does(which you could probably get by with), but the Peavey SP118 does not, but the SP118 is the better of the two speakers. The Yamaha SW118V isn't  to bad either and I believe it has a low pass filter in it. I'd probably take the Yamaha SW118V over the Peavey PV118.

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Quickness of mind will deceive the eye

Actually I was trying to keep it as simple as possible because of the group here. I've been involved in speaker design projects in the past and magnet weight, Vas, Qts, Fs, and Xmax are all interrelated and affect efficiency, box size, and porting as a group. I brought up just one of these figures - Xmax - because overextension is where most people get into trouble these days. Amplifier power is so cheap and there's a tendency to pour too much into subs.

Don't know what Xmas is other than Christmas.

But definitely check impedance, power handling (hopefully there's an RMS figure), SPL 1w@1m... these are the ones usually available right on the cab.

Last time I opened up a Yamaha 18 sub it had a driver with a 3"vc which is why I didn't recommend it. And those cabs, which are MDF constructed,  have been known to rattle apart.  But it was the series IV. Did they upgrade the series V's Londonlive?

edit: After thinking about it I'm going to add that for karaoke Yamaha Club subs should be just fine. If you aren't doing high-volume DJ work or using them in a band (my previous experience) they're not going to get pushed as hard. I know that Karen K has a pair and they're probably working out great.

Depends on the sub, some will come with a basic passive crossover built in, but you'd be alot better off going with a separate external & crossover the entire system to match each other.

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Ok so Ive got a yamaha emx512c and 2 br 12's right now. I want to add low end, what would be the best way, and with what components? Not necessarily highend stuff! This is for my garage only... Thanks guys!

You didn't state that this is not for club use.  For home use, you COULD probably get away with the homemade subs as you aren't going to be really pushing the volume that hard as you would in a club setting.
However you have to be careful with the ohms.  The 512 only goes down to 4 ohms maximum.  If the subs in question are not 8 ohms, they would need a separate amp to power them coming from the line out on the front of the mixer.  If they are 8 ohms, you could add them in parallel with the BR12 - 1 per side.

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I am kinda leaning more towards I would rather do it right the first time, then to do it wrong or half assed and not get results. I am looking to get a peavy or behringer 18. They have them at good prices from my local music shop. I think I will need an amp as well... Do they make amps with crossovers built in?

Some do. The Yamaha "P" series has variable low or hi cut. I have the P7000s for sub use and really love it. My QSC PLX amps have fixed frequency switches I believe but I don't have them here at home so can't remember for sure. You just have to check the specs.

I use a Driverack for crossover and other signal management duties but have often thought about going without it on some jobs and just using the crossovers in the power amps. But I haven't been that brave yet.