How do I determine the "magic numbers"
rhyde
Posts: 10
I would like to learn how to set all the "magic numbers" in the DriveRack 4800.
Specifically, I have some amps (generic), I have some speaker cabinets (generic, bi- and tri- amped).
How do I determine the parameter values for each of the "units" in the drive rack?
Okay, cross-over frequencies aren't *that* hard, but what do I use for delay values (intra-cabinet delays for phase alignment)? What do I use for limiter thresholds? How do I determine the magic "EQ" bumps and valleys for a particular cabinet?
I have found the speaker tunings to be less than useful, to be honest. At best, they provide crossover values and maybe some EQ values. They don't provide limiter settings (because they're independent of an amplifier).
I want to be able to write a document explaining to my sound people how to do this; the DBX documentation doesn't come close to this and the only info I got from DBX at the NAMM show is "call DBX technical support, the guy there is great at providing this information." That may well be, and he might be absolutely brilliant, but that doesn't help me a whole lot on a Saturday morning when I show up at a show and someone wants to tie a weird amp and cabinet ("weird" meaning I've not programmed it before) into my system or one of my amps is down and I have to substitute a different amp into the system.
Cheers,
Randy Hyde
Plantation Productions, Inc.
P.S. I miss the Wizards of the DR 260 units
Specifically, I have some amps (generic), I have some speaker cabinets (generic, bi- and tri- amped).
How do I determine the parameter values for each of the "units" in the drive rack?
Okay, cross-over frequencies aren't *that* hard, but what do I use for delay values (intra-cabinet delays for phase alignment)? What do I use for limiter thresholds? How do I determine the magic "EQ" bumps and valleys for a particular cabinet?
I have found the speaker tunings to be less than useful, to be honest. At best, they provide crossover values and maybe some EQ values. They don't provide limiter settings (because they're independent of an amplifier).
I want to be able to write a document explaining to my sound people how to do this; the DBX documentation doesn't come close to this and the only info I got from DBX at the NAMM show is "call DBX technical support, the guy there is great at providing this information." That may well be, and he might be absolutely brilliant, but that doesn't help me a whole lot on a Saturday morning when I show up at a show and someone wants to tie a weird amp and cabinet ("weird" meaning I've not programmed it before) into my system or one of my amps is down and I have to substitute a different amp into the system.
Cheers,
Randy Hyde
Plantation Productions, Inc.
P.S. I miss the Wizards of the DR 260 units
0
Comments
That said, there are formula for amp input sensitivity, but that even really isn't ultimately that important in the light of doing a proper gain structure.
There are ways to determine alignment delay at the crossover points without using FFT
1. invert the polarity of one of the drivers at the crossover point I.E. the sub at the sub to lo mid crossover, and play a tone that is equal to the crossover point (lets assume 100hz) so, one speaker is reverse polarity so the tones should cancel...It won't be quite as easy as finding a LACK of sound... because there are overtones and harmonics involved that will complicate things...but find the place of LEAST sound and you'll be close. The same goes for the other crossover points.
The 260, with it's Auto eq offers a chance to get the volumetric frequency balance right IF the polarity is right for the various drivers...this brings up another tip, IF you are having a TOUGH time with a crossover point, just can't seem to get the equalization right... reverse the polarity of one of the components (note here that if this is the lo mid, and the lo mid to high mid is ok, reverse the polarity of the sub...and so forth...The 260 could help you (even in a room) get the balance of frequencies right (if you miced close enough to keep reflected energies low enough to not be a factor in the Auto EQ...HOWEVER there is NOTHING that can be done for a system if the drivers are out of polarity, or the cabinets are aligned improperly.
This brings up another absolute... MAKE DOUBLE DAMN SURE that all the cables and speakers produce a positive outgoing pulse when one is present, and a negative one when that pulse arrives (usually a positive pulse results in an OUTWARD motion of the cones, and thus a 9V battery would produce the same results, but the tweeters are hard to detect ***note***some JBL drivers are REVERSE wound! )
There are ways to determine a rooms impulse response, and some of the other factors but determining a flat frequency response without MAD skills or a measurement system (especially with DIY speakers)... well it's complicated...
I also have two DR PA units, but that's another story
If buying SMAART is what it takes, I don't have a problem with that. To be honest, I ought to have SMAART running all the time for the same reason I bought a 4800 -- largely for looks if nothing else. Note that I run ITech 8000 amps, so logically I would have been better off using the DSP in the amps and skipping the 4800 altogether. I chose the 4800 for three or so reasons:
1) It looks cool in the rack ($3,000 cool? I don't know, but the box does look good on my tech rider).
2) One device to program instead of six
3) Allows me to use "less than ITech" amps for the HF component of my tri-amped rig.
Gain structure is understood.
But when I'm using an IT8K to drive some SRX 725 cabinets (LF section), I'd like to know how to compute the thresholds for the limiter section to protect the speakers (both RMS and Peak).
Very OLD JBL drivers, I might point out. Been down that road in the past. All modern stuff (since sometime in the 80's if the technical people at JBL are to be believed) is wound to produce an outward excursion with a positive going pulse.
Granted.
Fortunately, most of my gigs are outdoors and I can usually get by working on 1-space or, worst case, 1/2 space.
Clearly, phase aligning my subs (usually center clustered and a dozen or more feet away from the FOH mains) is going to require something a bit more sophisticated than what I am doing today. By the end of the year, I would like to be using SMAART (or something similar) for this purpose. In the meantime, running the DR 260's Auto EQ mode with the RTA mic at a sufficient distance to get a mix of all the drivers in the cabinet should work okay with my existing setup (all JBL SRX cabinets). I wonder what the optimum distance would be? Three meters?
I have been warned against dialing in setups with a DR 260 and programming those numbers into the 4800. Something about different filter algorithms and the like (someone could verify this warning for me).
Right now, using numbers gleaned from the JBL SRX technical specs for cross over frequencies, the sound I'm producing is okay (even if not optimal). Still don't know how to set the thresholds on the limiter. No doubt, phase alignment for drives will have to wait until I get SMAART (or something similar) up and running.
cheers,
Randy Hyde
Kudus to them.
Cheers,
Randy Hyde
Yes that's true but the setups for those speakers IO am SURE are available for the 4800.. I'm sure I saw them in mine, or downloaded them at one time for helping someone out.
The beauty of the 4800 is that it is PURE and neutral and transparent, meaning, unlike the 260, 480, BSS, XTI, it has NO "Sound" but is like a strait wire amp.
SMAART would be a good way to go, as is Praxis, and Spectrafoo (these are probably easier to use?) and a number of other platforms, interpreting the data is the hard part...If you want to get the most out of any of the platforms training would be almost a necessity...
What was that question in the SC section about????you obviously know about System Architect..or was it an OBSERVATION about a LACK of clarity regarding the port? Guess I'll have to go with that one till you clarify.. it's SO very hard to judge inflection in written word... :?
That question was from "randrtech", not "rhyde"
FYI to help determine If SMAART is the correct call for you.
You can purchase SMAART online for $895. SMAART is a bit complicated to use without training (I have run into one or two exceptions to that rule but don't count on it). Training is a 3 day seminar and cost $600. Training probably will not be held in your back yard so assume you will do a bit of driving and stay in a hotel for 3 days..........and miss 3 days of work.
SMAART isn't the cheapest or best program out there but I feel it has the best support and best training program.
If this sounds like a good investment of both time and money, go for it! If you take the training, you will be able to answer 70% of the questions you have asked in this thread.