What's all the DSP rocket science?

[DaBender]

I keep reading over and over about how great powered speakers are for the neophyte, since there's a lot of magic already done and you just need to hook up your mixer and go. I've been hanging around here for a few years now, and the amount of magic I'm aware of in a typical club system is pretty small and might only be dealt with once, so I'm all ears as to what I'm missing. Here's what's required for a passive system, to my knowledge -

 

1) you must buy an amp or amps to match your speakers, being aware of the effect of daisy chaining on impedance and amp channel output. This isn't that difficult and is essentially dealt with in the buying process.

 

2) assuming you're running subs, you need a crossover in the system. Many of the MI amps have this built in now. Set it once, and if you always set up the same way, the only magic involves running the speaker wires from the proper channel to the tops or subs.

 

3) there should be a high pass filter in the system. Many eqs and standalone crossovers have this feature, as well as some amps. Again, set it once and leave it that way forever.

 

4) eq - a big subject. Active speakers need no eq for the box, while a passive can probably benefit from it. Again, the box doesn't change and you will probably eq to the room anyways, so I'm not sure there's a big benefit here.

 

5) clip limiters - probably built in to the actives, available on some power amps where it would be set once and left for life. Amps with internal crossovers usually don't have limiters or high pass filters, but many folks have run without them for years without blowing things up.

 

6) bi-amping the top boxes. A feature of all the quality active speakers, but not possible on all passives and a bit of hassle if you choose to do so, often debatable as to how much benefit is achieved.

 

7) ease of setup - while many folks claim active has a huge benefit here, with a couple of well thought out rack cases and the new lightweight power amps, less connections may be made for setup than running power cords to every cabinet.

 

What am I missing?

[Dookietwo]

You pretty much have it. One small advantage with powered speakers is less room in the van,car,or trailer. No amp-eq-processing racks to transport. Also its very easy to turn a powered speaker into a powered monitor. Making it easier to have multi channel mixes with less routing. As an example with 5 monitor mixes that need to be Biamped you need 10 amp channels. 5 stereo crossovers (if the power amps don't have built in dsp) proper eqing. ( Active may need some but it depends on the desk being used) Of course there are powered monitors out as well.

Down side is bringing power-signal to the boxes. But with multi signal-power cabling its easy to do.

With the same speakers used for mains and monitors a system then can be expanded or made small to fit the gig / pay.

Like in this PA with 8 EVSxA250 speakers and a 4 matching subs. This gave me lots of front end and an easy to run 4 channel monitor mix. I had a fun time running it.

 

As always "It depends" is the best way to look at it. What is easy for one person is not right for another. They all require work and they both can sound bad if the wrong person is behind the mix.

 

Kindest Regards;

Doug

[rwhealey]

8) A professional speaker designer matched the amplifier to the speaker, created the DSP program/designed the analog signal processing, and set the limiters.

[agedhorse]

You are missing pretty much everything.

 

driver appropriate limiting algorithms

appropriately sized power amps

proper crossover frequencies, slopes and offset delays... maybe very steep filters

HPF's that may move depending on drive level versus frequency

Eq that may be much more than what is available with a 1/3 octave graphic

proper band levels in biamp boxes

much more complex multi-parameter limiting with appropriate time constants and integrating functions

 

The engineering and test equipment to do this is relatively expensive and complex to operate (correctly) and many cases of bad data have been encountered.

[dboomer]

Gotta agree with Andy. The benefits of a "captured" system are enormous compared to a roll your own system. About the only time good quality self contained systems aren't the best choice is when you need to design clusters otherwise pound for pound and dollar for dollar they are much better.

 

#1 - Engineers can design a specific amp to power a specific speaker. This leads to a better and more reliable system. Other systems both speakers and amps much include extra protection since they don't know what's coming. This protection tends to be audible and expensive.

 

#2 - Other "magic" includes level matching, EQ and time and phase alignment probably not included in a roll your own.

 

#3 - Maybe ... but you will get a general purpose filter rather that a designed for the system filter.

 

#4 - if you run the speaker in other than tiny rooms the need for EQ is very small (or none)

 

#5 - again ... limiters in amps are peak limiters and usles you get lucky they are only "generally" set. With self powered again engineers can dial you in much better

 

#6 - Are you kidding? I haven't seen a pro show in 40 years that wasn't bi-amped (at a minimum. Big difference in expanded dynamic range, lower distortion and driver protection.

 

#7 - yes, much easier, probably lighter, more reliable and way more versatile. Easier to "shade" levels

 

Like I said ... with the exception of custom clusters I can't think of a reason that separate racks and stacks would be the best choice. Your post almost reads like a guy that just spent a bunch of money on the wrong thing trying to convince himself it's the right thing. I can't see it.

 

What do you think the benefits of separates are?

[Coaster]

you can pry my DSP outtas my cold dead hands, i aint going back to analog xover

[abzurd]

Specifically to #6 - If you're not bi-amping the mains then your'e using the passive crossover in the box. Active crossovers head and shoulders better than passive. I was going to write some down, but THIS ARTICLE seems to do a decent job of touting the benefits.

[DaBender]

 

#6 - Are you kidding? I haven't seen a pro show in 40 years that wasn't bi-amped (at a minimum. Big difference in expanded dynamic range, lower distortion and driver protection.

 

 

As I said, I'm talking about a club situation, thinking crowds of 200 or less. I realize actual concerts are a whole different ballgame.

 

And no, I haven't recently spent much of anything. I have spent a lot of time contemplating whether any upgrade in the future will be active or passive. It seems odd that manufacturers like JBL are pricing the MRX and PRX series so close, though the recent increases doubled the difference between the 12" models from $50 to $100.

 

I've heard a lot of great music from passive systems over the years, I have a hard time to picture how much sweeter it would have been to my ears had it come through powered speakers.

 

One of my favorite bands still runs the bass and guitar to the room, and they always sound fabulous.

[abzurd]

Nobody said passive systems can't sound good. No doubt though that, if the mains aren't bi-amped, it's not sounding as good as it could (although you can certainly make a bi-amped system sound worse too). You started the thread with the "neophyte" in mind. Plug-n-Play with all the homework done for you is advantageous. Sure you can still make it sound horrendous, but that's a different issue.

 

Understanding sound is subjective, take an inexperienced band that was going to be running sound from the stage and stacked the makings of a passive system in one room and an active in another. Next tell them to set both up and you'd be back to hear them play through each. Now you're told you have to place $100 on which system would sound better. Where do you put your money?

[RoadRanger]

IMO passive monitors and subs can still make sense but powered tops generally sound much better than their passive cousins. If you only need two or three monitors powered makes sense there too (I run up to nine often) . Passive tops start to make sense again when you get to the SRX and above level and can afford the external DSP and expertise needed to "tweak" them properly. YMMV ...

[DaBender]

I really wasn't trying to be argumentative about the subject. As I stated, I keep hearing about all this "DSP" done for you, but I've heard very little about what it does. I'm here to learn, and the points in my list largely reflect what I've learned here.

 

I am learning from this thread. I never would have dreamed that a person buying a crossover might choose one that wasn't optimal for his speakers and amp, for example. I figured there was a quality gradient and better was better, not "it depends". You folks are making it sound like the average person has been dealing with a sizable handicap until the advent of powered speakers.

 

Keep talking and you may have me convinced.

[Axisplayer]

Since you said crossover, lets go with that one. A DSP allows asymmetric crossover points that an analog crossover doesn't. Being able to create that "hole" is one way to deal with issues AT the crossover point. You can over/under lap cabinet bands to smooth out response and phase issues. You can use it to adjust acoustic crossover points without changing slope. You can vary the slopes much more easily. Pick a BW-12 for one cab, and LR-24 for another, Most analog crossovers (until you play with the big boys) are not going to give you that flexibility.

 

The average person HAS been dealing with a sizable handicap until the work was done for them with tools they generally don't have.

[WynnD]

We used to sing through a Shure Vocal Master PA in the early 70s. It wasn't the best sounding PA of that type, but it was almost impossible to get it to sound bad. The ones that could sound better could also sound much worse. That's a 70s vote for matched components. (And we don't want to go back to those PAs if we can avoid it.) I'd say that this is the reason that engineers get paid big bucks, but they're probably only making a decent middle class living. Powered speakers are a good choice for most small bands. While it's not the only way to do it, you really have to have a gotta do it myself attitude to bother with passive speakers. (I've got that problem, and even I consider going with powered speakers from time to time.)

 

I have a working Vox Continental organ that I loved playing at the time. It can't hold a candle to my current gig rig. (Even though I'd like to take it out once in a while.) Sometimes the fantasy is much better than the reality. It's probably going to rot in my basement. (Or be trashed when I die.)

[agedhorse]

 

You folks are making it sound like the average person has been dealing with a sizable handicap until the advent of powered speakers.

 

 

Absolutely.

[agedhorse]

Generally, asymmetric crossover filters are not a great choice (there are exceptions), but sometimes underlapping points is the best tool for dealing with acoustic anomolies.

[dboomer]

 

I've heard a lot of great music from passive systems over the years, I have a hard time to picture how much sweeter it would have been to my ears had it come through powered speakers. One of my favorite bands still runs the bass and guitar to the room, and they always sound fabulous.

 

 

So how much better could it have sounded? I'm certain there are a number of people that thought their older state of the art analog TV's looked pretty sweet ... that is until the first time they saw a football game broadcast in high def and could count the blades of grass on the field. After that going back to the old analog system they had and been perfectly happy with just looked smeary.

 

Also I think that this band probably sounds fabulous because they simply are fabulous. Likewise a great sound system isn't gonna make a crappy band sound better.

 

So the average person dealing with an old roll your own "system" may not have a sizable handicap but they do have a handicap (unless they can out engineer the engineers). There is just no way that dollar for dollar they can compete. That doesn't mean they should go replace an existing system that seems to be working well, but I would think that moving forward it's the way to go.

[dboomer]

 

Generally, asymmetric crossover filters are not a great choice (there are exceptions), but sometimes underlapping points is the best tool for dealing with acoustic anomolies.

 

 

I don't know if I'd agree with the generalization. Having developed a few dozen "factory presets" it seems to me that maybe half of them involved asymmetrical filters and/or underlapping filters. It just depends. That said there is not one and only one way to design them anyway, just a bunch of trade-offs

[agedhorse]

I would generally look at underlapping before asymmetry due to all the other variables and trade-offs involved with asymmetry.

[Barisaxman2000]

Biggest drawback IMO at this time is powered systems in the MI-grade space don't scale that well where tops are concerned. Most tops are 90 degree boxes that only really work in a 1 over x (subs) configuration. Powered subs are simple in this scenario, but other than Yorkville Unity tops, I'm not aware of middle of the pack powered boxes readily available that can scale to 2 over 2 etc. per side (I'm sure there are some). Most of those that fit this description are well out of the budget of most MI operators.

 

I'll keep my QRX212's and DSP for now

[RoadRanger]

Most tops are 90 degree boxes that only really work in a 1 over x (subs) configuration.

I'd have to join AH in disagreeing on that one.

[Barisaxman2000]

 

I'd have to join AH in disagreeing on that one.

 

 

Like I said, I know there are powered boxes with less than 90 degree horns, but the vast majority of MI level boxes (those readily available to consumers at your local shop of choice) do NOT fall into the category of boxes that work well in multiples per side.

[RoadRanger]

Like I said, I know there are powered boxes with less than 90 degree horns, but the vast majority of MI level boxes (those readily available to consumers at your local shop of choice) do NOT fall into the category of boxes that work well in multiples per side.

To clarify - no prob according to AH with doubling or tripling up PRX (or SRX) tops even though they are 90 degree boxes.

[jlb]

 

To clarify - no prob according to AH with doubling or tripling up PRX (or SRX) tops even though they are 90 degree boxes.

 

 

This is good to know as I might add another 712 to each side in the future.

[agedhorse]

 

To clarify - no prob according to AH with doubling or tripling up PRX (or SRX) tops even though they are 90 degree boxes.

 

 

Correct, the off axis uniformity is smooth enough that comb filtering is not much of an issue. Don't forget that under ~1k, the pattern of even a 40 degree box is still >120 degrees so it's all in the perception.

 

Where is was a big problem was in some of the old exponential horns where the off axis pattern looked ragged and not uniform in the slightest. Combine this with HF on axis beaming and you had a tough situation to combine. This is what led to dual driver adapters, etc.

[Zeromus-X]

 

As I said, I'm talking about a club situation, thinking crowds of 200 or less. I realize actual concerts are a whole different ballgame. I've heard a lot of great music from passive systems over the years, I have a hard time to picture how much sweeter it would have been to my ears had it come through powered speakers.

 

 

It's not the difference between passive and active, but between non-processed and processed. When I had a pair of Meyer USWs, I was surprised by just how ... bland? ... they sounded. When I added their B2 processor, it's like the things took on a life of their own. The sound was tighter, deeper, and louder, just by adding the processor to the mix.