QSC kw153 sensitivity compared to omniTop 12

[y2kindyz]

A friend came by the other day and saw my tuba 30 build. I asked him if he had ever heard of a horn loaded Sub. He said that he had never heard of such a speaker, so I started to explain the theory of horn loaded subs with my limited experience. Then he started to tell me about the QSC system that he purchased. It was pair KW153 and a pair KW181. He raved about having the amp and mixer on board is the way pro sound should be run, due to having the amp so close to the speaker and not having a delay in vocals when singing. He went on to explain that there is a lot of delay when the Sound Engineer is in FOH there is a signal delay from vocals having to travel from mic to FOH amps the to speakers. He also said that a 12" was too small for a sub and did not believe that it could it would be very loud.

Ok, I told him about my build and I told him that 2 30 Tubas with 12" speakers would probably keep up with his KW181's with 18" speakers and the OnmiTops 12 would do the same with his KW153's with 15" speakers.

Needless to say he didn't believe me. So I told him that I would invite him over to listen after I finished up my T30's and OTop 12's.

I could not find any sensitivity specs on the QSC site or any graphs. All it said was Max SPL of 135db

So, Did I miss speak? I plan on running a EP2500 for the subs and XTI1000 for the OTops. How will my setup compare to his QSC system?

Many Thanks

Oscar

[BrentEvans]

A friend came by the other day and saw my tuba 30 build. I asked him if he had ever heard of a horn loaded Sub. He said that he had never heard of such a speaker, so I started to explain the theory of horn loaded subs with my limited experience. Then he started to tell me about the QSC system that he purchased. It was pair KW153 and a pair KW181. He raved about having the amp and mixer on board is the way pro sound should be run, due to having the amp so close to the speaker and not having a delay in vocals when singing. He went on to explain that there is a lot of delay when the Sound Engineer is in FOH there is a signal delay from vocals having to travel from mic to FOH amps the to speakers. He also said that a 12" was too small for a sub and did not believe that it could it would be very loud.

Your friend knows much less than he thinks he does. Electricity travels through wire at close to the speed of light. Wire doesn't cause latency. Latency comes from distance the sound travels in air, not in wire (roughly 1ms/ft in air). In teh same time sound travels 1 foot in air, it can travel ~1,865 miles in wire.

There is a reason to have the amps close to the speakers, and it has to do with impedance (voltage drop) and capacitance in the speaker wire. Keep your runs 14 gauge or larger and less than 100 feet and you'll find those problems to be negligible.

Ok, I told him about my build and I told him that 2 30 Tubas with 12" speakers would probably keep up with his KW181's with 18" speakers and the OnmiTops 12 would do the same with his KW153's with 15" speakers.

I could not find any sensitivity specs on the QSC site or any graphs. All it said was Max SPL of 135db

QSC published a calculated maximum based on the point of highest sensitivity (in the horn) and the amount of power available to the whole cab (even through only half is available to the horn). The woofer can't keep up with the horn, so the cab is a bit topheavy in balance. The real max output is about 127db, and sensitivity of about 99-100db 1w/1m.

So, Did I miss speak? I plan on running a EP2500 for the subs and XTI1000 for the OTops. How will my setup compare to his QSC system?

Your system will be a bit louder than his, have better horizontal dispersion in the tops, and with EQ, it will sound just as good if not better.

By the way.. the crossover in the XTI is fine for the tops, but you'll need something separate for the subs.

[sine143]

what are you loading your T30s/ Otops12s with?

As far as the "delay in the vocals" bit.... does he somehow think that sound magically travels faster through xlr cables than it does through speaker cables?

A pair of t30s with premium drivers (vplated) with enough power will easily outrun a single kw181. (and go lower). How do you plan on processing the t30s?

[Bill Fitzmaurice]

He went on to explain that there is a lot of delay when the Sound Engineer is in FOH there is a signal delay from vocals having to travel from mic to FOH amps the to speakers.

Your friend isn't exactly up to speed. The speed of an electron wave through wire, that is. At 650,000,000 feet per second there's no audible signal delay until the total wire length reaches 10,000 miles long. Give or take.
The rest of his 'theories' are just as valid.

[y2kindyz]

what are you loading your T30s/ Otops12s with?

I got the Delta 12lfa's and the deltalite 2512.

I have a DriveRack PA for processing.

From what I have read on the forum I know that he really did not know what he was talking about. Especially when I asked him if he knew what the sensitivity of his speakers was and if he could show me the response chart. He had no clue. I am sure he researched and read reviews on his system but he lacks education that this forum has helped me with.



thanks for confirming my thoughts. I know now that I was not over stating the potential of the T30's and OT12's

[BrentEvans]

From what I have read on the forum I know that he really did not know what he was talking about. Especially when I asked him if he knew what the sensitivity of his speakers was and if he could show me the response chart. He had no clue.

That's not entirely his fault. QSC simply doesn't publish the information. Since they're powered cabs, though, it's nearly irrelevant. In those cabs, also, there is DSP to flatten the response so the sound good out of the box (and they do sound good enough for most purposes).

QSC's big sin is what I posted earlier... they have their max Spl statements badly wrong. I doubt any engineer would have made that bad of a mistake... it almost had to have been derived by marketing.

[doncolga]

Be sure to keep us posted on the listening/comparison.

[byacey]

He raved about having the amp and mixer on board is the way pro sound should be run, due to having the amp so close to the speaker and not having a delay in vocals when singing.

The only noticeable delay would be between the FOH engineer's ears and his fingers when prompted by a performer on the stage to adjust the mix.

I can't imagine trying to do good job of mixing twiddling knobs behind the FOH speakers.


Those powered speakers are what I call "all the eggs in one basket". Should something happen to the speaker, you are down one speaker and one power amp, and the same situation if an amp fails; you're down one amp and the associated speaker. At least with individual components, you can usually shuffle things around to continue making sound.

[sine143]

It might be a close bout between te delta 12 lfs and the kw181. I would have sprung for lab 12s personally

[Grant Bunter]

I was just looking at the asking price for kw153's on ebay in the US, and they start at about 1K/cab.
You're going to build all 4 of your cabs for not a whole lot more than 1 of his, unless he got an astounding deal somewhere. Even with amps and everything, you'll still be well under his cost.

That alone should be enough to make him green.
But don't tell him that until after he's heard your system

Just keep in mind though, you may never convince him that your cabs are louder, or any of the other stuff he firmly believes now is myth/questionable/what he's been told.

QSC are not alone when it comes to not putting out SPL charts...

[67baja]

Wow - $5299 for the set:
http://www.amazon.com/QSC-KW153-Powered ... =qsc+kw153

[Curtybob]

Wow... by my best guesses, it is going to cost me less than that for 8 T39's, 8 DR250's, and 4 NU3000DSP power amps.

[Bill Fitzmaurice]

Wow - $5299 for the set:
http://www.amazon.com/QSC-KW153-Powered ... =qsc+kw153

A complete mis-match. The tops are twice the size they need to be to match those subs. Or there's half the number of subs required to keep up with those tops. Whichever way you look at it, it's typical of commercial systems marketed to those who have little to no understanding of how to match up speaker components, which of course describes the OPs friend.

[y2kindyz]

I will keep you all posted as soon as I get them finished and have him take a take a listen.

It might be a close bout between te delta 12 lfs and the kw181. I would have sprung for lab 12s personally

These are for my Bro-in-law and that was his budget. I think he will be happy and my friend will be impressed. Besides, he is already thinking it's only a 12" compared to his 18". I think they will blow his mind that the subs are only 12" and able to play as loud as his.

[Chris_Allen]

Be careful with the 'loud' comparison. Harmonic distortion creating frequencies in the band pass above the subwoofer may make the QSC sound louder.