Welfare PA project

[SoundInMotionDJ]

I completely disagree with using passive crossovers, because you'd be locked-in to a frequency and slope which, in all likelihood, will be far less than optimal. Inexpensive active crossovers have many shortcomings, least of which is often poor reliability.

In anything that even resembled a Pro Audio context, I would agree that a passive crossover is not the way to go.

BUT...this thing is not like that other things. The recommended driver for the SLA has 40w of power handling. Wired with a pair in series, and each pair in parallel, the system will still have an 8 ohm impedance, and a whopping 80w of power handling. That is well within the range of what a passive crossover can handle. And, the passive components are $20-ish per SLA. For someone who is putting a toe in the water, instead of leaping with both feet / going in head first, that is a very reasonable compromise. Yes, a passive crossover will be a single slope and frequency. No a passive crossover will not handle large amounts of power. BUT, given the goal, and the application - passive will be fine.

At that point, I would lean heavily toward the DEQ as the next purchase. Using the RTA to set the EQ is a better use of $$$ than the DCX to control the crossover points.

--Stan Graves

[Mikey]

For someone who is putting a toe in the water, instead of leaping with both feet / going in head first, that is a very reasonable compromise.

It's not a matter of power handling, as a passive crossover with adequate components could easily be used in this system without fear of over-powering, obviously. It's a matter of having good control in order to maximize the ability of getting the best possible sound from the system.

The Goldwood drivers are 40w each. With four drivers wired series/parallel in each cab (8 ohms per cab), they will handle 160w per cab, and each cab will have sensitivity of about 90db.

For heavy synth usage, I wouldn't use the onkyo tweets. I'd use 4 series piezos per cab, since added sensitivity isn't needed but power-handling is. Also, by using piezos instead of the Onkyo tweets, that eliminates the need for crossovers in the SLAs.

Each AT and each SLA would be 8 ohms. If passive crossovers between subs and mains were used, then a decision would have to be made ... mono or stereo. For mono, the crossover components would be for a 4 ohm / 4 ohm system. For stereo, the crossover components would be for two 8 ohm / 8 ohm systems (L & R). Passive components for subs-to-mains are not cheap. IMO, the cost-versus-usefulness of passive components just isn't worth it. If passive crossovers are tried and not liked, then you're out the money spent and you end-up buying what you should have bought in the first place. Or, to quote the popular phrase here ... Spend once, cry once. If OP wants to use passive crossovers in order to put together this "welfare system", that's cool, it's his decision, but at least now the pros and cons of passive-versus-active crossovers have been pretty well-explained, so that he has more information to aid him with his decision.

[Frankenspeakers]

http://ratch-h.com/arrayimpedance-revised.html

check out the above link for array impedance...
an array of 4 per side is ok... but fer a few dollers more: 6 drivers per side gets you 9.6 dB gain instead of 6 dB for 4
the caveat is that the total impedance is about 5.3 ohms, but most amps can handle that fine.

I agree with most of what Mikey sez, but for the sla's you will need a 3rd order low pass to roll the mid-woofers off between 3K and 3.5K (where the Piezos 'turn on' at) you can either stay with 4 tweeters or go up to six and series-parrallel them with two groups of three.

You will want some stands for them that make the tops of the lines slightly above the average Joe (Joanna) standing and sitting. (between 3 and 6 feet) Line arrays are VERY directional in the nearfield which means that you don't have HF reflections bouncing off the floors and ceilings to blur the highs.

Triamping your setup is unnecessesary, but I do recommend biamping it.

You can find a slough of electronic crossovers on craigslist or fleabay expect to spend about 80 for a good used rane. you only need one that is a 2 way that can sum the bass, you will be crossing between 100 and 150 if you go with the SLA/AT combo. for the Home mode a pair of ADCOM 535's or NAD 2240's will be all you need, possibly all you need for a budget show... If you want more power, then the NAD 2100 or a Carver or Hafler amp (these are all good used possibilities) Highly recommend the DEQ/DCZ if you can budget it.

This should give youse some food fer thought... and some direction to your thinking.

[Mikey]

an array of 4 per side is ok... but fer a few dollers more: 6 drivers per side gets you 9.6 dB gain instead of 6 dB for 4
the caveat is that the total impedance is about 5.3 ohms, but most amps can handle that fine.

But once your parallel the two cabs, the nominal impedence is only about 2.7 ohms to the amp. I won't about impedence again. However, bear in mind that some relatively low power amps are only good to 4 ohms per channel. Also, given the small gigs he does, the extra drivers may just be unnecessary overkill and packspace. That's all up to OP.

Triamping your setup is unnecessesary, but I do recommend biamping it.

Me too. Although using passives would be the cheapest route, I don't personally feel that it's a sacrifice worth making. But, again, that's the builders' decision. At least it's been pretty well explained for him.