DBX Driverack as speaker sim/DI ?

kringle77 · #1 08-26-2011, 07:24 AM

For the price of a good mic for your cab, you could buy a used dbx driverack pa. I was thinking that with the 31 band eq, compression, and other filters, you could possibly use it as a speaker simulator / di . It would be a halfway point between a mic or straight di. I like the sound of the jensen mod10-50 speaker for mids and character. Could I just copy the printed frequency response plot for the jensen with the 31 band eq and get a good result? Compression could be used too. I have alot of experience with the driverack pa and have always thought about trying this. I'd run out of my genz benz 9.2 di to the driverack and then out to the mixer.

MNAirHead · #2 08-26-2011, 07:39 AM

I understand what you're going for

I'll be the first on this forum to comment that much of this becomes irrelevant when it's altered by sound guys and their provided gear

------

What you're really describing is a zoom, digitech, or line6

( I do own all of the above mentioned gear )

MNAirHead · #3 08-26-2011, 07:42 AM

Forgot to note. What you're trying to do is almost 180 from the theory of a driverack

A driverack is to opimize speakers to a room's natural tuning - not speaker simulation

kringle77 · #4 08-26-2011, 08:34 AM

Yeah, Im a jerk like that!

Oh, I am the soundman / bassist for my band so, I've got almost as much control as chuck norris.

Passinwind · #5 08-26-2011, 09:35 AM

The DriveRack PA is pretty limited compared to something like this, but if the feature set works for you make sure you get one without the power shutdown problem.

Using a printed infinite baffle frequency response curve is a long way from getting where you're trying to go. At the very least, you should measure it yourself in a cab and with the mic and mic placement you like.

You might try messing with convolution reverb and recording your own impulses of cabs you like. I've only done that at home on my computer, but it's pretty cool.

kringle77 · #6 08-26-2011, 09:55 AM

Thats a bit farther than I would ever go. Cool though.

agedhorse · #7 08-26-2011, 11:57 AM

The DRPA isn't going to help you model the distortion components generated by a speaker, nor the non-linear response that a speaker generates when being driven hard and at different frequencies relative to it's impedance plot.

It's a great piece for it's intended use however.

Munjibunga · #8 08-26-2011, 02:22 PM

Sounds a little complicated to me.

agedhorse · #9 08-26-2011, 04:44 PM

Quote:

Originally Posted by Munjibunga

Sounds a little complicated to me.

You are correct, it IS very complicated, which is why you don't see many programmable speaker simulators on the market.

kringle77 · #10 08-26-2011, 04:57 PM

Well, Im headed out to the gig tonight. I'll be using my new stambaugh attitude bass for the first time, genz benz 9.2, and ampeg 8x10 with six B810 drivers and two jensen Mod10-50 drivers. The only spare mic I have is my trusty shure beta 58. Not my first choice. But, I'll be very close to the drummer so, if there are no problems using this mic, I may well be in the market for a senn 421 or EV re20. We'll see. I like the idea of a really good speaker simulation because I like to remove as many variables as possible at a live gig but, sometimes it is what it is. It's nice to just plug in and go. Happy gigging tonight everyone!

Zooberwerx · #11 08-26-2011, 05:01 PM

Quote:

Originally Posted by MNAirHead

Forgot to note. What you're trying to do is almost 180 from the theory of a driverack

A driverack is to opimize speakers to a room's natural tuning - not speaker simulation

Yessir! The DR is pretty much a GEQ, PEQ, xover, limiter, compressor, delay, and RTA wrapped up in one not-so-easy-to-use package....unless you're willing to read the manual. It's also a great remedial exercise for those who insist on running power amps with the attenuators dimed. You will walk away knowing a lot more about gain structure, though.

Riis

agedhorse · #12 08-26-2011, 05:19 PM

Don't believe the gain strucrure tutorial (and addendum) in the DR manuals. It's verified wrong for any practical application and can lead to some unexpected and bad results in the field.

Zooberwerx · #13 08-26-2011, 05:48 PM

Quote:

Originally Posted by agedhorse

Don't believe the gain strucrure tutorial (and addendum) in the DR manuals. It's verified wrong for any practical application and can lead to some unexpected and bad results in the field.

Please elaborate. I've used the aforementioned tutorial with good results. For that fact, my gear responded exactly as described when following the step-by-step instructions.

Riis

agedhorse · #14 08-26-2011, 07:52 PM

Quote:

Originally Posted by Zooberwerx

Please elaborate. I've used the aforementioned tutorial with good results. For that fact, my gear responded exactly as described when following the step-by-step instructions.

Riis

Having the console clip point the same as the DRPA clip point and the power amp limit point effectively defeats all limiting throughout the system.

Work out a gain structure and level diagram and you will find that the drive electronics will clip at the limiting threshold defeating the limiting action.

This is design electronics and electronics application 101, and when I presented it to the DBX application engineer the ONLY thing he could focus on was minimizing noise floor. He wouldn't even address my findings and kept returning the discussion to noise floor which is a non-problem compared with the lack of limiting for 99.9% of all practical users. I understand that this is the "company line" however.

I have designed plenty of digital and DSP based applications and I am intimately familiar with all of the trade-offs involved. I just developed a hardware modification for a popular DSP speaker processor (not DBX) that in spite of some goofy glitches is a pretty good sounding unit. If they would have addressed some really basic things and understood pro audio input and output standards, they could have had a DSX killer but they shot themselves in the foot. Again, these were documented problems with bone-head easy solution (as far as engineering solutions go) that would have cost maybe $1.00.

kringle77 · #15 08-27-2011, 01:18 AM

Im home from the gig. Man, I haven't used the 8x10 in a long time live. It sounded awsome. The beta 58 worked pretty well. I only used it for some dispersion out in the room. Mic touching screen, center of driver, most of the lows rolled off at the board. I've never had a better bass sound in my in-ears. A bit too much mid-low mids to the front of the house, probably because of the mics proximity effect. I may have to invest in a 421 mic now. Or maybe keep using the 58 and eqing it. Im sure that I'd be missing the distortions, etc that come from micing a real speaker as opposed to mimicing one with an eq. I've got the pa rack at my house now and maybe I'll play around with the driverack anyway.

Zooberwerx · #16 08-27-2011, 07:21 AM

Quote:

Originally Posted by agedhorse

Having the console clip point the same as the DRPA clip point and the power amp limit point effectively defeats all limiting throughout the system....

Point taken....and an excellent description of the procedure. IIRC, the idea is / was to roll in the DR limiters in such a way that they kick in before the power amp limiters do. Our PA demand is rather low so I can't say I've ever seen a limiter activate during the course of a routine gig....with one exception. If we run the "soft knee" option much above 4, we'll see occasional red lights on the DR's ouput meters.

You mentioned "bad results" in an earlier post. Again, exactly what should we be looking for and how can we best ammend the process?

Riis

agedhorse · #17 08-27-2011, 09:54 AM

This goes for all speaker processing gain structure:

There MUST be headroom between the point that the amp limits (or clips) and the point that the weakest link in the drive electronics clips. This difference is called headroom and is the amplitude that the gain reduction of the limiter acts upon when entering limiting. If you want to insure that you can drive the system 6dB into limiting without the danger of clipping then you must have 6dB of drive headroom from which to subtract gain from. You must also be aware of processing anomolies where drive headroom may be taken away from in terms of algorithems and possible hysteresis in compression, and conversions where displays are not as accurate as you might think (this were 2 specific defects in the DSP I mentioned in post 14 and accounted for an ~4dB MEASURED error.

Also, it's critical to verify the numerical incications that the DSP provides and specifically what it's referenced to (dBu, dBv, dBm, dB full scale, or some arbitrary scale), and what the maximum I/O levels really are (the DR series is jumper selectable between +14 and +30+dBu AND the imput and output scaling are independant).

Generally, I recommend 12dB of drive headroom which allows for adequate limiting compliance as well as accommodating possible errors in level/scaling throughout the chain.

I think the DR product manager(s) got way too focused on maximizing the S/N ratio number and forgetting the importance of headroom under real world operating conditions. I don't know why, the product is plenty quiet to worry about specsmanship IMO.

kringle77 · #18 08-27-2011, 11:58 AM

..................anyway. I played around for a couple hours today and I got some great sounds with an eq in the bass channels insert but ended up always prefering the mic'd sound, dead center touching the speaker grill. Is the 421 the mic I want? With the beta 58 I ended up rolling of low end and also 250hz to remove the proximity effect.

agedhorse · #19 08-27-2011, 02:15 PM

421 has a switchable HPF in addition to a very different proximity effect and overall flavor. It may or may not be what you want.

kringle77 · #20 08-29-2011, 07:03 PM

I decided that after about 7 years of 98% DI, Im going back to a mic. I decided to try out a sennheiser e609 and using a graphic eq in the pa rack to dial out the proximity effect and the big bump around 4khz. I've been trying this at home today with my beta 58a and it works great. Those mids and speaker grit just sit in a mix so well and you can actually hear it at lower volumes than a di. If I wanted to actually get low end out of the mic, I'd try an EV re20. I just need mids and highs into the pa for dispersion and let my cabs fill out the low end. I know this is alittle backwards but, it works well in small clubs and gives the pa a lighter load so that everything sounds better. It feels better to have that big rig push behind me.