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Compact PA system - comments please?
Compact PA system - comments please?
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Old 1st January 2009, 03:13 AM   #21
rcw is offline rcw  Australia
diyAudio Member
Join Date: Jul 2005
Location: sydney nsw
If you use two beta eights per side with a qb5 II filter assisted reflex alignment...

box volume= 60litre, tuned 90Hz. aux filter q=.5 at 80Hz.

this will accept an average input of 150Watts for pk. cone excursion 2.8mm., ie .2 less than the rated linear and produce 120db. spl for -3db. at 87Hz.

despite tuning lower most of the sound is harmonic anyway the fundamental being much lower in amplitude.

If used as mtm lobe steering is not a problem and centre to centre distance of 335mm. will give a 40degree vertical beam compatible with 40x90 cd horn
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Old 1st January 2009, 05:23 PM   #22
BlueWizard is offline BlueWizard  United States
diyAudio Member
Join Date: Jun 2007
Here is a thought from a PA system I build many years ago. It was basically a so-so PA, but I did have one good idea.

On the back I had THREE 1/4" phone jacks, the center one was for the incoming signal, and the right and left were the outgoing signal. I wired one of the out connector to connect in parallel, and the other to connect in series.

That was several units could be plugged in and have some reasonable chance of maintaining a stable impedance.

Unfortunately, no matter how many times I explained the need to keep impedance within a workable range, the users constantly connected things in a willy-nilly fashion.

Still, if you make more of these cabinets for larger venues, then you will need some flexibility in connecting them. Or, if you are combining your equipment with the equipment of some other band.

The series 1/4" phone jack had a built-in normally closed switch. That switch closed the path to the rest of the speakers. When you plugged another 1/4" phone plug in, the switch opened and inserted the new external speaker in series with the internal speakers.

If you build a cabinet that has two woofers, it is likely to result in 4 ohms, which means whatever else is connected is best connected in series, unless you have a 2 ohm stable amp.

Sorry, off on my own tangent here.

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Old 6th February 2009, 08:58 PM   #23
Lincoln1 is offline Lincoln1  New Zealand
diyAudio Member
Join Date: Feb 2009
First I will apologise as I tried to start a new thread and the forum wouldnt let me, just said "do search" first. so tried that I may also be after the same thing as this tread for my tops, and multiples hence posting.
Anyway admin please feel free to move this to another area.

(Start again)
Hi, I am new to the forum. I used to assist bands with extra PA gear which I built for a disco business I used to run. Recently I got all my gear out of storage and put it into our rumpus room so I could see if it all still goes. I also got some cheap cerwin vega intense PA speakers, but they are crap and not very linear. A good eq helps take the big lump around the 8k area out. The rest was all built by me some 12-15 years ago. I recently also got hold of an XP5000 amp to run all the 4 subs at just over 1k each, as my stack of fet amps are still unfinshed (well amp boards are done but not cased yet.
Here are some pics from yesterdays 'test' day.

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

I took vids but the camera's mic was full-time distorted from the bass, even at around 8-10metres away. The subs are double tuned bandpass for the range of 45Hz-100Hz, and I roll them off at 35Hz where they are around 97dB at 1 watt. at 45Hz-100Hz they are approx 109dB at 1watt/1metre, so incredibly loud which was what I wanted. Reasonbly compact but tight and clean with no after-ring, or upper harmonics like some w-bin's I've heard.

Anyway one of my RCF 15 tops needs replacing/reconing and the CV's that I got are shite, so what is available to replace them with that is of reasonable quality? There is soo much stuff out there, chinese and not. If you could afford them the top notch JBL 15+horn were the go, however around NZ$2.5k a pop back then was out of my price range. They did sound good though.
So are these still the be all and end all of full-range 15" PA stuff? or are there other brands worth a listen? I like building them as well so was hoping I may save some $$ and DIY it if I just buy the drivers.
Please post your opinions on a 15" and horn replacement (just thought I'd make sure that's what I want to use to ensure flexability-wise.
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Old 14th May 2010, 10:05 AM   #24
Eclectic is offline Eclectic
diyAudio Member
Join Date: May 2010
Post My humble attempts

The speakers I have used most of all and currently still use after 25 years and refuse to get rid of comprised 4 boxes each with one 16 ohm Fane Crescendo 60 watt 10" speaker - yes I know, guitar speakers - and one tweeter - not sure of the model but they were all in one black jobs with moulded cover over the magnet, bought cheaply from Tandy (radio shack).

The speakers were originally bought to make up midrange cabinets for a much larger PA, but the larger band never happened and carrying huge speakers lost its appeal.

The boxes are 12x15x12 inches with a small port tuned to 40 hz - about half the resonant frequency of the speakers - and crossed over with a simple capacitor hi pass filter at 10khz.

Yes, I know they were lead guitar speakers and have huge ferrite magnets, so I don't save that much on weight, but they were about as efficient as I could get at the time because I couldn't stretch to JBLs and the like. I crossed them over as high as I did just to let the tweeter cover the overtones and protect them from high energy stuff and tuned them that low because I had read something that said it would work. And it has.

Experiences: One speaker just stopped working after a year or so, but that seems to have been a spontaneous failure which I was unable to find a repair for at the time. I have replaced it with an anonymous driver which has a bassier tone and has been used for low level keyboard/bass duties.

The rest have continued over the years, I was using a pair of fairly large Electrovoice 15b in single cabs with them but stopped and donated them to a friend who was doing a lot of low paid church jobs. I kept going with the tens and have used them for discos (not powerful enough in the bass on stands, but fine on the floor, but the crowd - who were sober - enjoyed the gig) solo and choir gigs, announcements, outdoor music for a wedding, and also keyboard and bass guitar duties in pairs at louder gigs. They have kept going and all fit into the boot of my Fiat Punto hatchback.

I recently bought a Subwoofer and couple of TOA speakers (SL-120 and RS-20) which I got really cheap. as I have starting a soul trio and want something more professional looking for functions. My speakers are very roughly finished.

I intend to compare the three pairs and decide what to keep and what to get rid of. I will probably keep the 10s for foldback duties.

My original design brief, more suck it and see than science, seems to have worked, the 10s stand up against anything and with the high impedance and high efficiency tend not to tax amplifiers very much - the wedding was served well with one pair and a Carlsboro Marlin 120 watt PA amp. The sound is clear and smooth - probably why they were never that successful as guitar speakers.

I would recommend the single 10 plus tweeter route. I reckon if I was using the speakers more regularly with a woofer I could halve the size of the boxes, and I probably would have if I hadn't adopted a "no more projects" motto for this year.

If anyone can get their hands on a single 16 ohm Fane Crescendo 10m 60 watt speaker, I would really like to return to 4 identical speakers in those cabs, or whatever I house them in in future.

Final tip with small speakers - if you are ever using them for meatier duties, Blutack or similar semi permanent fixing material provides a way to couple the cabinets effectively and really helps solidify the bass.

I'm signing off, yes I'm not doing DIY speakers at the moment, but I thought I would share my experience
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Old 22nd May 2010, 08:37 PM   #25
Eclectic is offline Eclectic
diyAudio Member
Join Date: May 2010
I thought I would post the results of the listening test:

1. My DIY (10 guitar speaker plus tweeter) = Loud and middley - harsh even with the subwoofer playing. Lyrics are very clear, the harshness could be tamed easily even with limited eq.

2. The Toa SL120s, (1x12 + piezo driven horn flare) = full, loud, but not great for vocal definition. My friend who was helping me sad "suddenly I can't make out what you're saying or singing". Integrates well with sub woofer. Not bad for 20 plus travel on ebay!

3. The Toa RS 20 (4x5 inch + piezo driven horn flare) = very sweet sound, clear and with that small driver ability to make the sound appear from beyond the box. Again, good integration with sub woofer. Produces good volume, but I suppose if listening with my eyes, I sometimes wonder if they will manage prolonged higher volume - not bad for 20 plus travel with stands on Ebay!

Conclusion: For 100 - 200 vocals and band work, the RS20s on stands, either alone or with subwoofer are perfect.

For anything bigger or open air the sub, SR 120s and home made speakers should project while producing a degree more warmth up front.

So - no more projects . . . . I might take a big saw to the home made 10s and turn them into foldback wedges, but not til next year! But I now have couple of stacks of small speakers which should be fine for anything I have to do on my own or my small band.

I do hope someone reads this!
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