Building small portable P.A.

[wood nacho]

Hey guys and gals

I do a fair amount of busking and am planning to put together a small, lightweight, battery powered P.A. I've looking into the Roland products but they seem to be too pricy and have way to many features I won't need.

The plan so far is to use a small 12V battery:
http://www.atbatt.com/product/24211/...h/battery#tabs

Hooked up to an efficient/tiny poweramp:
http://www.daytonaudio.com/index.php...er-module.html

Speakers, here is where I need a little help. I'm not sure what the best combination is to use. I'm thinking either 2 8" fullrange speakers or and 6" midrange driver and a little tweeter or something along those lines. I need the speakers to be as efficient as possible with a 90db 1w/1m or higher rating. I will be playing acoustic guitar and vocals/vocal percussion through the unit. Any speaker recommendations? I don't have much experience with speaker selection so any info is helpful? I would like a fair amount of bass but can smaller speakers 6" or under) provide a good amount of bass?

These full range speakers seem to be really affordable and fit my needs:
http://qcomponents.ca/product.php?pr...&cat=59&page=1

I'm going to use some sort of preamp infront of the P.A. to give me some control over my sound. Maybe even a simple Boss Eq or something. As for the cab itself, I'll probably just end up making one.

[Bobby1note]

Sorry, I don't mean to rain on your parade, but did you look at the distortion spec for that amp-module? 10% THD at rated output (15w). At 9w, it's .03%

Do you have tools and woodworking know-how, to build a cabinet? This could end up costing you a lot more than an off-the-shelf combo-amp, or powered speaker.

You may want to consider a power inverter (12vDC/AC), and a 12v deep-cycle battery.

[wood nacho]

Originally Posted by Bobby1note

Sorry, I don't mean to rain on your parade, but did you look at the distortion spec for that amp-module? 10% THD at rated output (15w). At 9w, it's .03%

Do you have tools and woodworking know-how, to build a cabinet? This could end up costing you a lot more than an off-the-shelf combo-amp, or powered speaker.

You may want to consider a power inverter (12vDC/AC), and a 12v deep-cycle battery.

Hi there, to be completely honest, I have no idea about distortions specs. I take 10% at 15W is extremely bad? I won't be running it full power. Probably like half or 3/4. Could you recommend perhaps a better amp? I was also thinking of getting this one but it seems also to have a similar disortio spec.

http://www.daytonaudio.com/index.php...er-15-wpc.html

Yes, I can build a cab.

The reason I tried to avoid the deep cycle battery/inverter is that I had a hard time finding one that was under 25lbs. Having an inverter would also be another investment/something to carry around with me. I'm trying to keep this whole unit as lightweight/simple as possible.

[jomaynor]

Distortion for a tube guitar amp is a desirable quality by many, but for PA amps, under 1% is the norm. 10% distortion of a vocal signal would not be desirable.

Regarding speaker sensitivity, generally the larger the speaker diameter, the greater the sensitivity. Horn loaded speakers, for example, have greater sensitivity than other designs, since the horn mouth acts as an extension of the speaker driver.

[Bobby1note]

Originally Posted by jomaynor

Distortion for a tube guitar amp is a desirable quality by many, but for PA amps, under 1% is the norm. 10% distortion of a vocal signal would not be desirable.

Regarding speaker sensitivity, generally the larger the speaker diameter, the greater the sensitivity. Horn loaded speakers, for example, have greater sensitivity than other designs, since the horn mouth acts as an extension of the speaker driver.

Those are internet myths. Speaker diameter has absolutely nothing to do with sensitivity. Some examples would be an 18: JBL XLFs subwoofer (99db @1w,1m), and a Yorkville LS801P (106dB @1w,1m. Both have 18" drivers.

Same applies to the horn-loaded drivers.

[kramster]

Find a used Roland or a Crate Taxi

[TerryAllanHall]

Originally Posted by wood nacho

Hey guys and gals

I do a fair amount of busking and am planning to put together a small, lightweight, battery powered P.A. I've looking into the Roland products but they seem to be too pricy and have way to many features I won't need.

The plan so far is to use a small 12V battery:
http://www.atbatt.com/product/24211/...h/battery#tabs

Hooked up to an efficient/tiny poweramp:
http://www.daytonaudio.com/index.php...er-module.html

Speakers, here is where I need a little help. I'm not sure what the best combination is to use. I'm thinking either 2 8" fullrange speakers or and 6" midrange driver and a little tweeter or something along those lines. I need the speakers to be as efficient as possible with a 90db 1w/1m or higher rating. I will be playing acoustic guitar and vocals/vocal percussion through the unit. Any speaker recommendations? I don't have much experience with speaker selection so any info is helpful? I would like a fair amount of bass but can smaller speakers 6" or under) provide a good amount of bass?

These full range speakers seem to be really affordable and fit my needs:
http://qcomponents.ca/product.php?pr...&cat=59&page=1

I'm going to use some sort of preamp infront of the P.A. to give me some control over my sound. Maybe even a simple Boss Eq or something. As for the cab itself, I'll probably just end up making one.

Look for a used Crate Limo 50...doubt you could build your own "mini-PA / battery" for less $$$ and these are VERY dependable, sound great w/ a Shure SM58 and an a/e guitar, and get easily 6 hours of use between chargings.

Been busking w/ one for some years, w/ my bassist partner plugging into my spare Limo. Also handy for weddings, nursing homes, veteran's hospitals and other low-volume solo gigs.

[wood nacho]

Thanks for the advice everyone. I have a bit of money saved up and I'm actually going to try both routes, building my own amp, and buying one as well. If the build doesn't work out so well I can always use it as my rooms new sound system.

I've ordered a Roland KC-110 keyboard amp/P.A. I chose it for it's weight (20lbs), it's size, and it's speaker arrangement. The only thing I'm worried about is not enough volume. (only 20W)

For my build, I bought an efficient class D amplifier putting out 2x15 Watts, and 2 cheap 6" full range speakers. This came to a total of about $50. I really skimped out on the speakers and thus I think the sound may really suffer. If it turns out alright, I might buy a battery powered mixer to give me some tone/volume control and more inputs.

I'll be sure to post my findings once everything arrives/is assembled.

[jomaynor]

Originally Posted by Bobby1note

Those are internet myths. Speaker diameter has absolutely nothing to do with sensitivity. Some examples would be an 18: JBL XLFs subwoofer (99db @1w,1m), and a Yorkville LS801P (106dB @1w,1m. Both have 18" drivers.

Same applies to the horn-loaded drivers.

It's not an internet myth at all.

Besides - you, without perhaps realizing it, proved the point about speaker sensitivity and horn loading. The JBL 18" sub is a front firing, vented design, and the Yorkville 18" is ... a horn design.

Sensitivity is not as important in live sound today since power is comparatively cheap, so other factors, such as excursion and reduced distortion at high SPL take precedence over sensitivity, as a rule (other than HF drivers, since these fry diaphragms so easily, so designers almost always use horn loaded systems for HF in live sound, the exceptions being the stack-a-tweet stick types).

http://mixonline.com/TECnology-Hall-...eakers-090106/

Horn loaded mains cabinets, such as the Altec Voice of the Theater, were standard loud rock box PAs, due to their ability to get loud with minimal amplifier power - due to their 103db 1W/1m sensitivity - back when watts were expensive, and the Crown DC 300 was the pinnacle of amp power until a couple of decades ago.

[Bobby1note]

Originally Posted by jomaynor

It's not an internet myth at all.

Besides - you, without perhaps realizing it, proved the point about speaker sensitivity and horn loading. The JBL 18" sub is a front firing, vented design, and the Yorkville 18" is ... a horn design.

Sensitivity is not as important in live sound today since power is comparatively cheap, so other factors, such as excursion and reduced distortion at high SPL take precedence over sensitivity, as a rule (other than HF drivers, since these fry diaphragms so easily, so designers almost always use horn loaded systems for HF in live sound, the exceptions being the stack-a-tweet stick types).

http://mixonline.com/TECnology-Hall-...eakers-090106/

Horn loaded mains cabinets, such as the Altec Voice of the Theater, were standard loud rock box PAs, due to their ability to get loud with minimal amplifier power - due to their 103db 1W/1m sensitivity - back when watts were expensive, and the Crown DC 300 was the pinnacle of amp power until a couple of decades ago.

Wow !!! There's a "blast-from-the-past" for you. The Altec A7 Voice-of-the-Theatre were a heck of a loudspeaker in their day. A friend of mine, actually had four of those, which he used for his home-theatre set-up, back in the 80's. (12' diagonal screen/video-projector). SPL was insane. I watched "Top Gun" over that system, and the aircraft carrier scenes, were insanely loud.

Jomaynor, I'm in full agreement that horn-loaded cabinets will be louder, but that's not how I read your post. As I read it, you were saying that the larger the raw "driver" was,,, the more efficient it was? In other words, all i8" drivers for example, would have the same efficiency (sensitivity), and that only the enclosure-design, makes one 18" driver more efficient that another. Did I misread that?

[RustyAxe]

My "small, portable PA" consists of a Carvin S400D and the matching extension speaker. Runs about 3 hours (depending on volume) on the internal "gel cell" battery, and all weekend on a 12V marine battery.

[jomaynor]

Originally Posted by Bobby1note

Wow !!! There's a "blast-from-the-past" for you. The Altec A7 Voice-of-the-Theatre were a heck of a loudspeaker in their day. A friend of mine, actually had four of those, which he used for his home-theatre set-up, back in the 80's. (12' diagonal screen/video-projector). SPL was insane. I watched "Top Gun" over that system, and the aircraft carrier scenes, were insanely loud.

Jomaynor, I'm in full agreement that horn-loaded cabinets will be louder, but that's not how I read your post. As I read it, you were saying that the larger the raw "driver" was,,, the more efficient it was? In other words, all i8" drivers for example, would have the same efficiency (sensitivity), and that only the enclosure-design, makes one 18" driver more efficient that another. Did I misread that?

Bobby1note, yeah, VOTT - a blast from the past! Used everywhere from your best local bands in town, to the rock ballrooms, to Woodstock.

Regarding non horn loaded sensitivity differences: this would be a situation where if, say, the magnet weight, the motor structure and voice coil, and importantly, the speaker cone material was identical, then a 15" driver would have approx a dB more 1W1m sensitivity than 12", which, in turn have have roughly the same ammount more sensitivity than the 10". This is due, of course, to the larger radiating area of the cone, given x ammount of voltage over otherwise identical motor structures. A good example of this would be the JBL EON series, where the 15" plus HF horn has a couple of dB higher sensitivity spec than the 10" plus HF. Hope this helps - cheers.

[Bobby1note]

Originally Posted by jomaynor

Bobby1note, yeah, VOTT - a blast from the past! Used everywhere from your best local bands in town, to the rock ballrooms, to Woodstock.

Regarding non horn loaded sensitivity differences: this would be a situation where if, say, the magnet weight, the motor structure and voice coil, and importantly, the speaker cone material was identical, then a 15" driver would have approx a dB more 1W1m sensitivity than 12", which, in turn have have roughly the same ammount more sensitivity than the 10". This is due, of course, to the larger radiating area of the cone, given x ammount of voltage over otherwise identical motor structures. A good example of this would be the JBL EON series, where the 15" plus HF horn has a couple of dB higher sensitivity spec than the 10" plus HF. Hope this helps - cheers.

Jomaynor, are you (ahem) "young enough" to remember the ElectroVoice Patrician 800, with it's 30" Hartley woofer? (late 60's/early 70's)? Seems to me, that it ran on a 100w amp, and the woofer had a 1" voice-coil. It looked to be the size of a refrigerator. There's an exercise in 'efficiency".

On "sensitivity", basically, what I'm saying is; not all drivers of the same size, have the same (or similar) sensitivity. Example, not all 15" drivers (enclosure excluded), have the same sensitivity, and, a 15" driver with lower sensitivity, will not necessarily be as loud as some smaller drivers, which have greater sensitivity.

[jomaynor]

Originally Posted by Bobby1note

Jomaynor, are you (ahem) "young enough" to remember the ElectroVoice Patrician 800, with it's 30" Hartley woofer? (late 60's/early 70's)? Seems to me, that it ran on a 100w amp, and the woofer had a 1" voice-coil. It looked to be the size of a refrigerator. There's an exercise in 'efficiency".

On "sensitivity", basically, what I'm saying is; not all drivers of the same size, have the same (or similar) sensitivity. Example, not all 15" drivers (enclosure excluded), have the same sensitivity, and, a 15" driver with lower sensitivity, will not necessarily be as loud as some smaller drivers, which have greater sensitivity.

Well, I'm "young," but I must not be THAT "young." I only became aware of that behemoth in the past few years, although they could have been on the market back then, and me not knowing it, given my "youth."

Before the VOTT became the go-to rig for rock, there was the Sunn Coliseum, which I remember as being way out of our budget in my high school years rock band, and we used play a lot, so they must have been really expensive back in the day. We aspired to the Shure Vocal Master, which we got, after selling that cool looking rolled and pleated sparkly PA - talk about listening with your eyes, those old Kustoms looked so appealing to the male adolescent brain, and they sounded so... uh, I don't recall. OK, I guess. I do recall thinking the Vocal Master sounded better. And talk about a basic concept whose time has returned - now there's Fish sticks and Bose sticks on the scene.

http://www.flickr.com/photos/515b/se...57615996097964

And speaking of behemoth speakers, Rudy Bozak's 1939 World's Fair speaker tower with 8 27" drivers is also noteworthy.

[DukeLeJeune]

Originally Posted by wood nacho

Yes, I can build a cab.

If your first attempt falls short in the SPL department, you might consider a Bill Fitzmaurice DIY design like the Jack 10:

http://www.billfitzmaurice.com/Jack.html