Why SHOULDN'T I Use MyPA As An Amp?

saxdragon · #1 07-14-2011, 11:20 PM

I plugged my Fender JB into the Hi-Z input of my PA head (Phonic 740 Plus 200 watts, cabinets have a 15-inch speaker and a horn) and it sounded pretty good and plenty loud, and after I put my Art Tube preamp in front of it to add a little dirt it was even better. With plenty of tone variation provided by the graphic EQ, I got a wide variety of sounds.

What's the downside of using a PA as a bass amp live? Not the band's PA but your own.

I'm looking forward to your thoughts.

Thanks,
saxD

T-Bird · #2 07-15-2011, 12:07 AM

Hi.

Quote:

Originally Posted by saxdragon

What's the downside of using a PA as a bass amp live? Not the band's PA but your own.

What's the difference?

A PA or a SR system that can handle the job works equally well regardless of who happens to own it.

Regards
Sam

littlepope · #3 07-15-2011, 12:24 AM

Be careful you don't let the magic smoke get out-'cause you cannot put it back in!!!

Reality: Your sound system total frequency range is more vast than a bass guitar amp. SR systems produce large spl's over a 20-20,000 hz range. Bass generally covers 40-maybe 4000 hz. (no pun for 5 & 6 stringers). 12,000 hz is just hiss in your preamp.

Besides . . who owns it is not relevant like T-bird says. If you blow it up you pay either way. (makes for less beer money).

saxdragon · #4 07-15-2011, 01:02 AM

The ownership is beside the point. I know lots of players DI into the band's PA or the house's sound system. I was wondering about the pros and cons (mostly in terms of tone and what the audience hears) of using my PA head and one of it's speaker cabinets as a bass amp. For instance, the PA speaker cabinet is lighter than the 15" bass speaker cabinet I take to a small gig, and MUCH lighter than the 2x15 cabinet I sometimes take.

That remark about hiss is interesting. I did notice a considerable amount as I turned up the volume.

More more! I want to hear more! Opinions, that is.

saxdragon · #5 07-15-2011, 01:05 AM

Ah yes...the magic smoke! What's the likelihood of it's appearance?

T-Bird · #6 07-15-2011, 02:02 AM

Hi.

Quote:

Originally Posted by saxdragon

Ah yes...the magic smoke! What's the likelihood of it's appearance?

Well...

The 220W to 4 Ohm without any frequency range or THD figure isn't promising. Most likely the cabinet (if it's of the same make) is pretty shy on power with any measuring technique as well. Also, the sensitivity of that speaker could be considerably lower than that of a dedicated bass cab, especially on the lower frequency range.

So my vote would be that the likelihood of a failure of some component of the system is pretty big. It all depends on Your ears, and your willingness and/or ability to back down on the volume if there's an indication of over-stressing the rig. Using any component that creates distortion (or makes an amplifier stage to distort) is going to make that very hard if not impossible.

My suggestion is always not to use a vocal PA to amplify keys or bass in anything outside a coffee-house type gig. If even in there.

Regards
Sam

allexcosta · #7 07-15-2011, 06:09 AM

Quote:

Originally Posted by saxdragon

What's the downside of using a PA as a bass amp live? Not the band's PA but your own.

To achieve a similar performance to the one of a bass system, a PA will have to be bigger, more expensive and probably more complicated to put together.

Even if you think it sounds good, the PA you mention was not conceived to reproduce a bass guitar with fidelity.

To do that, a PA should have a quality subwoofer and a top speaker, plus a powerful amp and a mixer with a good preamp.

A bass system just will have all of that (sort of) in a much smaller package.

Don't mean any disrespect, but a bass through a Phonic 200W PA is not exactly what most people would consider sounding "pretty good" or "plenty loud", but you should always let your ears be the judge. You are playing through it, not us...

Keep in mind that I have played my share of gigs using old Peavey powered mixers and PA or monitor boxes, so I do know how they sound like...

Good luck...

Thombas · #8 07-15-2011, 06:26 AM

I think Anthony Jacksons live-rig is (or at least was) a pre-amp into a couple of active Meyer speakers, either 2 cabs with a 12 and a horn, or a pair with a 15 and a horn. Meyer isn't exactly cheap, but I guess the idea as such can't be totally bad...?

modulusman · #9 07-15-2011, 06:29 AM

The Phonic isn't anywhere near a good sounding PA. I can't imagine it would sound any better as a bass amp.

Silas Stingy · #10 07-15-2011, 08:06 AM

As long as you aren't overpowering the Speakers and it sounds good in a gig situation then you don't have a problem.

allexcosta · #11 07-15-2011, 10:11 AM

Quote:

Originally Posted by Thombas

I think Anthony Jacksons live-rig is (or at least was) a pre-amp into a couple of active Meyer speakers, either 2 cabs with a 12 and a horn, or a pair with a 15 and a horn. Meyer isn't exactly cheap, but I guess the idea as such can't be totally bad...?

Surely I can spend 20K on a pair of Clair 12AM's, a Neve strip and an StudioR amp, but it's just easier and cheaper to achieve good performance with gear meant for bass.

3506string · #12 07-15-2011, 10:25 AM

It sounds to me that what you are enjoying from the PA is the transparency. Even a mediocre PA speaker is usually more transparent than standard bass cab. You may want to consider some of the three way cabs or a fearful.

PA tops aren't really meant to backline loud uncompressed live bass. I have no experience with phonic but given the responses they may be even less than idea for this kind of application.

staindbass · #13 07-15-2011, 04:39 PM

Quote:

Originally Posted by 3506string

It sounds to me that what you are enjoying from the PA is the transparency. Even a mediocre PA speaker is usually more transparent than standard bass cab. You may want to consider some of the three way cabs or a fearful.

PA tops aren't really meant to backline loud uncompressed live bass. I have no experience with phonic but given the responses they may be even less than idea for this kind of application.

i agree. the pa speakers have higher resolution and better fidelity than the crappy bass amps they sell in stores.

saxdragon · #14 07-15-2011, 04:41 PM

Thanks to everybody for responding.

3506String, I think you may be right. The extended frequency range and clarity of the sound may have seduced my ear. I'm an experienced musician with plenty of time spent onstage, but I'm only a novice bassplayer at this point. I was thinking of using my (admittedly cheap) PA as a bass amp to take to auditions and jams, because it's lighter. My knowledge of live rigs for bass is limited, because when I'm in a band it's usually in the role of sax player or singer.

Alexxcosta, thanks for your input. I had a feeling that there was something wrong with the idea of using my PA, but I wasn't sure what it might be. You and the other posters have definitely cleared it up for me. The Phonic is a low-quality PA. I only paid $300 dollars for the package of a 7-channel powered mixer with EQ for mains and monitors and an EFX system with two cabinets. I planned to use it for a rehearsal studio in my home and possibly to augment recording on my computer. My bass rig is an Acoustic 150B with it's matching cab with 2 15's. It's the first amp I ever bought, back around 1972, to play my Fender through. I also have a Sonic cabinet with a 15 inch speaker, which I use for jams and auditions along with the Acoustic head. It's an elementary setup, I know, but since bass is my third most-played it's all I've needed so far.

Thanks again for all the good advice. I guess I should look into buying a good combo amp.

anonymous122511 · #15 07-15-2011, 06:27 PM

Quote:

Originally Posted by saxdragon

Thanks again for all the good advice. I guess I should look into buying a good combo amp.

If you're liking the flat response transparency of a PA you might want to consider going for a more versatile cab/preamp/power amp rig or at least a cab/head combo. A rig of separate components allows you to really zero in on what works for you swapping out preamps and cabs as ones that suit you better come along. Some may disagree but in my experience the cabinet you choose often effects your sound more drastically than anything else.

stingraysvt · #16 07-16-2011, 01:02 AM

Stephan Lessard used to use two Meyer 650 subs and prob some Meyer tops too...

And if I remember correctly, Sting used 2 Clair boxes with his live rig,

I just dig playing through my amp better. Although my EA rig is pretty hi fi, it could prob even pass for a PA speaker...

It'll work, just to what degree... And what are you trying to achieve?