Karaoke Forums

What would I need to pay attention to assuming I want to be able to run higher output instruments directly into PA cabs as well as vocals. Such as Electric piano, synth, etc.  Is it wrong to assume that most 15 inch 3 way cabinet designs matched with a proper amp can handle an electric piano's output ?   Do most PA cabs come with a heavier duty speaker design  (such as one that would be found in a bass guitar amp) ?  or isn't a PA necessarily designed to accomodate a wide variety of apps.


Speakers in question:  (2 cabs)  Fender 115XP  

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Frequency Response 60Hz to 20kHz, +/- 6dB (Half Space).
Power Handling 150 Watts (E.I.A. RS-426), 300 Watts (Program), 600 Watts (Peak).
Impedence 8 ohm
Low Frequency Source 15" Woofer with 2" Voice Coil.
High Frequency Source Dual Piezo Tweeters
Sensitivity 95dB, 1 Watt / 1 Meter.
Maximum Output SPL 117dB.
Horizontal Dispersion 70 Degrees (at 5kHz).
Vertical Dispersion 35 Degrees (AT 5kHz).
Crossover Frequency 2kHz


                                                                                                thanks                                                                                

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Northeast United States runner up for the "Singing Hall of Shame".

300 watts program/ 600 Peak


Maximum output SPL  117 DB  




Can someone kindly explain this to me ?   300 (or more) watts only translates to a sound output level of around 117 DB ??    In the old days I don't think you'd hear a jetliner taking off directly overhead with the amps cranked open at 75 watts... Isn't a jet taking off nearby about 120 DB ???

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Northeast United States runner up for the "Singing Hall of Shame".

We used to run Peavey SP5s' for the keyboard monitor with a CS800 powering them.

Here is a good link for average decibel levels.

http://www.lhh.org/noise/decibel.htm

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Thanks Lonman.

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Northeast United States runner up for the "Singing Hall of Shame".

Steve you can fersure run instruments thru your PA mains, but you have to do it correctly...It's best done by mic'ing the instrument amps....A properly matched intrument amp will color and distort the sound of the instrument just the way it should be done....All the PA does from there is amplify it to a level that you can mix in with the vocals and project it all via the main PA at SPL's equal to whatever the main PA is capable of.

Top bands mic their backline instrument amps and run it all thru the PA every day....They do it fersure in large venues where they just can't cover the area using instrument amps alone.

But......(Sometimes a big but).....Sometimes you can ask to  much of your mains when you run all the instruments and vocals thru just two mains....You can lose definition and separation ....There is a fix for that, tho.

Let's say you need to mic the backline instrument cabs but need to retain good definition and separation from the vocals.....In that case, you just add another pair of mains...In one pair, you have the vocals, in the other, you have the instruments.....You can keep adding as required....even to the point that the drums are amped thru one pair and the other instruments thru their own pairs.....That's when you start getting into what's called an array....And that starts to get expensive.

But if you are doing karaoke and you want to add just a keyboard, then I doubt you need to worry about it. Just interface the keyboard into the mixer properly and run it all thru the PA.

We had a KJ here in town who used to always play his keyboard and sing between karaoke singers....many times he would play the keyboard as the singers performed their songs.....Soundwise, it was great, but often it would tick off the singers when he would jump in with his keyboard and backing vocals.

As far as SPL's from a given pair of cabs, remember to check the specs....They are always stated XXX dB/SPL @ 1 watt/meter @ XXX freq....The higher the dB/SPL's, the more efficient the speaker and the less amp required to drive it. There is a HUGE difference between speakers rated @ 127 dB @ 1 watt/meter, and ones rated at 136dB @ 1 watt/meter.....The 136dB speaker will produce several times more "volume" than the 127dB speaker while using the same amount of amp power.

The part you need to concern yourself with then is just how big a venue can these speakers fill at adequate SPL's?...It does not matter that you add instruments....Added inputs will not "weaken" the sound levels, but it fersure might cause things to sound kinda indistinct and just "loud".

Happy new year!

Thanks Keith !   Happy New Year to you, and your's too !

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Northeast United States runner up for the "Singing Hall of Shame".

Keith, Lonman (or anyone who might be familiar with certain audio physics/acoustics principles)



I'm confused about the concept of larger speaker area = fuller perceptible bass (at comparable wattage). Speaker size as a factor of bass response.

Is it ever possible for an 8 inch speaker to project the actual perceptible bottom a person can hear (or feel) in a head-to-head with even a slightly lesser grade 15 inch speaker ?  I've heard costly smaller cabs, in heads-to-heads with larger cabs. (4-5 1/4") woofer's ??? *assuming that's really possible, I suppose that's what I'm questioning*.. Isn't there something known as phantom bass too ? To my perception (and I'm not sure if this is imagined or factual); smaller bookshelf speakers can not provide the bottomy fullness of the larger cab with a 15 inch woofer. Yet I've not heard alot of what's out there today. Thing is, to me, the Bose Acoustimas system's always sounded like Tweeter's, and bass. The mid-range was noticeably missing. I know with the advent of certain technology, speaker's are more efficient today. Meridian for instance might claim their subwoofer's with only 1x10, can throw more bass than another companies 1x15 subwoofer. How much of that is speaker size vs. cabinet design ?

In essence... Assume a sound person want's to achieve the deepest perceptible bass sound and there are two cabinet's side-by-side: ( Both standard cab's with front facing/loaded speakers, not folded horn or reflex bass cabinet designs)

cab 1.     2x15"  Peavey black widow speakers  (rated at 400 RMS 800 Peak)
cab 2.     3x10"  Peavey black widow speakers  (rated at 400 RMS 800 Peak)

both cab's wired the same way, 30 inches of speaker total per cab.

My belief's were that cab 1 (with the fewer YET larger individual speaker's) would deliver the fuller perceptible bass. Is my logic off ?  Does this stuff fall into the "head room" category ?  or is headroom always a function of more speaker area per cab offers greater head room, than lesser speaker area ? I've heard claim's that it's total speaker area in the cabinet that gives the final sound, not individual speaker size (assuming both cabinet's are as efficient) yet here's what's baffling me..  Assuming this were the case,  in a bass stack with two cab's that can each handle the same wattage. Why would the bassist want perhaps a bottom 1x15 (without a horn) and top 2x10 (without a horn) at times as opposed to two 1x15 or two 2x10 cab configs ?? I'm not sure if it's fact (or rumor) that the 2x10 cabinet offer's a tighter punchier bass because of the individual speakers sizes, when compared to the 1x15 cab (given same speaker makes in each cab). I've heard conflicting stories, and I haven't a clue about what's fact vs fiction in this area.


                                                                                     Thanks

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Northeast United States runner up for the "Singing Hall of Shame".

Bass responce is related to how far the cone can travel and the size of the cone....Bass freqs are made up of longer wavelengths so the speaker cone vibrates slower and travels farther....It takes a speaker with lots of travel and a large cone to pump enuff air for decent bass.

Adding same size speakers do not grant you deeper bass, just more SPL's.


10" speakers can be designed to make deep bass, but you must have several of them in the box to produce high SPL's....10" speakers can produce tighter and punchier bass because the have lighter cones and the smaller cone surface won't distort as much as a larger cone.

I found a site Keith, and I'm trying to understand basic principles about speaker's

http://www.webervst.com/spterm.html


I'm reading about DB's now.  Trying to understand the exponential increase. This part is interesting, and something I never had a clue about.  I suppose it's necessary for me to read about this stuff.

This part of the above link is something I need to get to sink in:








I need to even familiarize myself with the part's of a speaker.

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Northeast United States runner up for the "Singing Hall of Shame".

Most of what I know about speakers come from this site. http://www.speakerplans.com/  may be of help to you.

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I can neither confirm nor deny ever having or knowing anything about nothing.... mrscott

I'm glad you both are reading up on bass.

Bass freqs are the most expensive and difficult freqs to do right....They are also the narrowest freqs in the whole spectrum.

But you know when they are right, they hit you in the chest without seeming too loud and your mids and highs still sound really crisp and brite.

A good test of your bottom end is Egyptian Lover's "My Beat Goes Boom"

Let's face it, KJ's need to mix in some hot, bass heavy dance music some nights...We need to see the dance floor fill up and the skirts flipping to keep our crowds happy.....You need a big tite bottom to get those big tite bottoms shaking and dancing.

The best way to run a keyboard is not by micing a amplifer. The most practical method would be using a direct box.

Yes, the keyboard should be patched into the mixer via a direct box...That's what I meant by "correctly interfacing" the input.

You can't do that with guitars and still retain that great guitar distortion.

Thanks for that Link Badsinger, and true Keith & Lyquiddye. For some stuff I suppose you need to run a DI box, and of course in the case of bass guitar, you have to compress it.  An old trick we used to do with guitar, for a weird but interesting Stadium type reverberation, was put a "Pignose" amplifier in a 55 gallon metal drum, and mic' that.. Alot of interesting FX can be played around with when Mic'ing.  I still haven't figured out various techniques regarding using combo's of standard mic's, and crown PZM type mic's to mic a larger piano and get both ranges of course.. Yet I suppose that's not the easiest thing for many...

Do any of you have any suggestions for a decent brand of DI box to run into both a Tascam recording studio, and a PA for piano ?   I think I've made the mistake of NOT putting the keyboard's into a DI box ever.  and even for bass, I've tried to make due with a Shure SM-57... It doesn't work IMHO...I think you must compress bass guitar when going direct, or even if recording fuller bass. seems mic'ing bass doesn't pick up any coloration in that frequency range well. Maybe it can't even pick up that frequency at all, not sure.

Keith, What's confusing to me these days is how much speaker "efficiency" comes into play in terms of sound or wattage heard.  Remember in our day ?   You'd NEVER find a 2X10 bass cab rated at 400 watt's RMS, It just didn't exist.. How many bass player's did we ever know that ran thru even 2x12's ?   Naturally on occassion we did see folder horn 2x12 cabs, but that wasn't too common as I recall... Sunn and Cerwin Vega had reflex and folded horn cab's that could handle 100 watt's RMS of bass (two rear or downward firing 12 inch speakers) projection cab (was that a reflex cab? with folded horn design?), however for larger venues when bass wasn't mic'd, we'd use the SVT cab's (with 8X10's) The Sunn coliseum cab I used to have that was rated at around 300 RMS watts had  two rear projecting 15's, and those were special design speakers to handle such amazingly high wattage for those times... (Of course that cab also weighed about 400 lbs).  Even the lower wattage amps such as Fender Bassman 10 (45 watt's)~(4x10's), some even used the Super Reverb, Fender Bassman 40, 60 (sometimes 2x12 cabs), and 100 (used 2x15's for higher input wattage to speakers) for the cab on the (piggy back) amp setup. I just don't recall it ever suggested in "the old days" that a bass guitar could go thru even 1x12, and handle much more than perhap's 25 watt's RMS.  First time I saw that done I was :floored: by the output (in 1982) of the Galleon Krueger cab. I had to replace my 100 watt Guild Starfire cab rig with 2X15 inch electrovoice SRO's, because even halfway turned up, I blew the speakers.  I didn't understand how 1x12 speaker could project such strong and loud bass when technology first enabled speaker's to handle more power..  My point being, in our "analog" amp days.  The loudest band amps pushed 85-100 watts RMS to even as high as "fender super twins" model in 1981 (a supposed 200 watt's RMS although the tone was horrid) into 2x12 speakers, (and I thought 200 watt's into 2x12 was really pushing things)  Fender Dual showman amps, and the Twin Reverb amps were rated at around 100 watt's RMS, although a few of the blackface, and silverface models were slightly lower wattage. Twin 65 reissue is 85 watts into 2x12's, and you NEVER crank that open. For bass, 4x10 and 2x15's, even an 18 (although that was pretty boomy with little definition) was more common even at lower wattages... Yet today Trace Elliot, SWR, and numerous other companies rate cabs, and speakers at handling double the wattage we saw in our day...  I remember around 1985 I bought a small practice bass amp,  "Gorilla GB-30" rated at 35 watt's I believe into a single 8" speaker, I couldn't believe that was possible... (My Jenson 12 inch Goldbacks in the univox cab handled about 15watt's before cracking up badly). Even the Celestion 12 inch Greenback rating of 75 watt's floored me... the 30 watt speakers seemed more like it to me for individual wattage handling on a 12 inch speaker.  

Technology advances and if you don't read up on newer technology, it's tough to have a clue as to what's going on, I never understood how anyone could even crank up to 25-30 deafening watt's RMS on a Fender Super Reverb in "the old days" (an amp rated at 40 RMS watt's), today with the advent of technology cab's are rated with single 15's and 12's as handling several hundred watts RMS  (unlike the day's of our Altec Lansing VOT monster bin's when stacks of bins comprised a PA to handle less "rated" wattage, thing is,  lower wattage was LOUD).  I need to understand just what "efficiency" means, and why our older tube wattage, appears so much louder than SS wattage... Someone mentioned awhile ago because the calibration of the potentiometer's on the older amps doesn't increase volume proportionately on older amps.. You might get a huge increase in volume turning the volume nob from "1" to "4", but after that there'd be little increase... (something like that).... All I know is that you NEVER saw small speakers rated at 100's of watt's handling capacity back then.

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Northeast United States runner up for the "Singing Hall of Shame".

In most bar sized venues, bass guitar is best left out of the PA and amped backline where you match the bass guitar amp to the venue....Where too big is good cause you can always crank the knobs down.

It's ok to mic the kick drum (even the full set)thru the PA providing you are set up for it and have proper gates and compression and your PA amps can handle the drain of the drums.

Once you reach the point that your mix in the mains sounds not as clear, then you need to expand your array and move the instruments out of the vocal cabs....You want it to sound clear and well defined, not loud.

My cousin and his wife just left here to return to Oklahoma after their weekend visit....She was sitting here last night while we were jamming.....She asked him why his system seemed "loud" but not clear like mine....She described how with my system we could still chat as the music was playing at high volume, but with his gear, it was always too "loud" to attempt conversation.

For bass to blend, or appear balanced in a band mix,  doesn't it require roughly 3X the wattage of the guitar amp ?  Higher frequencies carry at lower volumes ?  or something like that ?

I recall something like a bass amp to mix with a 30 watt guitar amp volume would need to run at around 100 watts..

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Northeast United States runner up for the "Singing Hall of Shame".

You are correct...Bass needs WATTS.

Remember the rule: Bass freqs are the most expensive freqs to do right.....Even a 4 to 1 ratio or more is required sometimes....especially when set up outdoors.

OOOPS...

Let's not get confused.....

When amping instruments strictly backline with just vocals and maybe keyboard in the PA, then you are correct that the bass guitar needs 3 times the watts as the lead guitar amp.

But once you start to mic everything into the PA, then bass needs even more power.

You'll know when you get there cause that's the point when you decide you need to mic the drums to fill the venue....When the drums can't be heard crisp and clear out front, it's time to mic all of it....And that's also time to snake the board out front and employ a decent sound guy....Heh, heh, it's also the time that the band decides to sell their powered mixer they were using for vocals and KB.

I hate powered mixers.