BillFitzmaurice.info

I touched upon this in another thread, but thought I should not derail that one and so I am posting here instead.

I see all over this board that it is recommended that the DCX should be the first box of electronics that you should buy (if going the DEQ/DCX route, as opposed to the DBX route). From what I have found on my DEQ, I am questioning that logic (oh no!)

The DEQ can RTA, crossover (yes it can!) and limit. The DCX can crossover (very well), limit, but cannot RTA, only EQ and even if you have a curve, it only has a few bands of parametric EQ that you can apply, so you will never get your tops sounding as good as they could sound.

I therefore wonder why the DCX is recommended first, as it seems to do less than the DEQ - admittedly it shines in the crossover and limiting sections, but it's EQ lets it down. The DEQ can make your BFM system sound as good as it should sound, although setting the crossover function (via high cut and low cut on the Parametric EQ) is a bit more fiddly, it can still be done. Is what I am trying to say is that the DEQ does the DCX's funtions better than the DCX does the DEQ's functions (as there is a certain amount of overlap in what each unit can do).

I'd be interested to hear your thoughts on this one. I am so glad I never bought a DCX and am thinking that other members may prefer to take the DEQ route as it eliminates the need for the 2 box solution. Please try to find fault, as I'd be interested to hear them in case I have overlooked anything. As I mentioned in the previous post, the only thing I am unsure about is the actual type of filter on the high cut and low cut functions, but having done a listening test, I believe them to be LR filters

How does the DEQ perform crossover?..there's only stereo out and aux out?..how is it limiting the bands independently?

Quite simply: the first item you buy is by necessity a crossover for sound quality and to protect your tops, and you must have a brick wall limiter to protect your subs. Ergo: DCX2496, DriveRack or DS2/4 or whatever you find.

You've heard it a million times but just for reiteration A CROSSOVER IS NOT THE SAME THING AS PULLING DOWN EQ . 24 dB down per octave is exactly that (24 dB one octave below crossover, 48 dB down two octaves below etc...). The best EQ gives you is ~-20 dB at a given frequency range. Let's say for arguments sake that you have a 30 Hz band on your EQ and you pull it all the way down. at 15 Hz the signal will be hardly attenuated while the crossover will have almost completely eliminated it.

Thus, buy DCX/crossover, then proper EQ when funds allow. If that happens to be all at once so be it, but I haven't had the luxury of running RTA and I've survived with basic placement and 3 bands of parametric on the DCX.

No! (I think)... The deq has high and low shelving filters, and then it has high and low cut... These remove all frequencies below/above the filter at 12dB an octave. Join 2 together and you have a 24dB slope all the way down
It also has a limiter
Can someone please check my workings actually on a DEQ to confirm I haven't missed anything.
Note... This would only be for a mono setup... L doing subs and R doing tops. For a stereo setup a DCX would indeed still be required (or an amp with a DSP attached to the DEQ's aux out (which is what I have iNuke w/ dsp
)

escapemcp wrote: setting the crossover function (via high cut and low cut on the Parametric EQ) is a bit more fiddly, it can still be done.

No, it cannot. That's not how a crossover works, and you should not do so.

Bill Fitzmaurice wrote:

escapemcp wrote: setting the crossover function (via high cut and low cut on the Parametric EQ) is a bit more fiddly, it can still be done.

No, it cannot. That's not how a crossover works, and you should not do so.

I knew this would be coming, so I tried to spare him .

Bill Fitzmaurice wrote:

escapemcp wrote: setting the crossover function (via high cut and low cut on the Parametric EQ) is a bit more fiddly, it can still be done.

No, it cannot. That's not how a crossover works, and you should not do so.

Bill, I am sorry to do this and question you, but I am going to have to call you on this. I believe my theory is sound, so I have tested it below for you (and all) to see (and replicate if you so wish).

I am not another potential builder who wants to know if his Solobaric Kicker will work in an Otop because "they are the same shape" I have stuck rigidly to the plans. I have used the recommended drivers (albeit, not the premium ones ). I have been using a high pass filter (on my iNuke) for my Otops set at 100Hz with a 24dB/octave slope.

I also have belief in my DEQ as a high-pass filter (shouldn't have really said crossover, as that implies 2 separate ranges, separated by a central frequency), so I set about testing, as if it can be heard, it can be measured.

So to test:
I hooked up my DEQ and iNuke NU3000DSP. I bypassed the DEQ, and engaged the HPF on the iNuke at 1kHz with a 24dB/oct slope. This would be my control as I know this is the filter that is required for my Otops, but I did set the frequency high, so that I could go a long way down the slope, for some proper triple figure dB reductions. I then got some test tones, all made in Audacity at 0.8 volume and with all the same settings. I played the 2kHz tone and set it to as close to 40V as I could (measured on the amp's outputs). I then played the test tones going down in frequency and recorded the voltages that they produced. I then turned off all the filters on the iNuke, and set my DEQ. I used 2 identical parametric filters set to low-cut (turn the bottom little wheel clockwise all the way when on the PEQ screen). I set the frequency to 1.02kHz (it wouldn't let me hit 1kHz bang on, but close enough for this test). I then repeated the tones and measured the voltages again. Finally, I removed one of the low-cut filters on the DEQ, just to see what it would do. Here are my results:
As you can see, the double low cut filter on the DEQ is producing practically the same filtering as the 24dB/oct filter on the iNuke. The reason I ran 2 filters was because when I did a listening test before, I could hear no difference between a 12dB slope on the iNuke and a single Low-cut filter on the DEQ, so 2 I reasoned, would make 24dB (although I was pretty unsure if it would work when I did it).

As I said before, I don't like to contradict Bill, as he is the heart of this place (really?! ) and I very much appreciate all he has done for my carpentry skills and my rig and this forum. I can understand Bill's reply, as he must get sick of Timp's (& others) eternal questions on possible alternative drivers or other theoretical theories! This is something I have actually tested and I believe it to work. The only thing that I have thought that might cause problems with this is the phase of the signal, and I don't know how this would affect it, and I am unable to measure this.

So do I have a point please? Or is there something I have massively overlooked, because I am struggling to find it... if I'm right, then great, and if I'm wrong I'd really like to know why, because that would mean I am massively misunderstanding something!!

Thanks for your time Bill, all of it, because thanks to your many nights designing speakers, I now have a kickass rig which blows everyone else's out the park (except for everyone else on here of course ). I very much appreciate your inputs and always enjoy reading your responses. Apologies for the comeback, but I am hoping you can see my reasoning. If I am correct in this then it could help someone else on here and that's why I am sticking my neck out in the hope I can add something back into this great forum that I have got so much from.

Many thanks,

Aidan

Interesting. I'll eat my words. I think the less of the day is you may be able to hp/lp with the deq this way but since I don't have a deq could someone explain how you can limit with one? Escape mentioned that it could but I'd like confirmation. For my uses I bought the right tool (dcx) but for those that need more eq than processing it appears that the deq is a winner. I did however get a great deal on my dcx so no regrets

The limiting is in the dynamics screen. It has almost the same interface as the limiter on my iNuke. If I am right, then this really opens up a much cheaper way to get started, as the cost of processing can put people off. It is probably less intuitive than the DEQ/DCX combo, but you can still get done what needs to be done. A cheaper cost means a few more people will be dragged down into the BFM addiction with us and that means more plans sold for Bill... everyone wins!!

Hey, I have even noticed that I could use it to sum my sub & monitor channels. Using the width function you can send both channels to one side. If you use the aux out for the tops and set the I/O for the aux so that it is connected just after the GEQ/PEQ module (which is BEFORE the width module), then the summing wouldn't affect the tops. Only issue with this would be that the sub and monitor channels would run through the GEQ/PEQ module, so you wouldn't be able to EQ the sub separately around the crossover frequency, and the monitor would have to take the tops' EQ settings (not an issue if using identical speakers for L, R and monitor).

escapemcp wrote:As you can see, the double low cut filter on the DEQ is producing practically the same filtering as the 24dB/oct filter on the iNuke.

Great now take a look at what a swine sweep through that mess looks like. And for more giggles see what the phase response is doing also.

Don also nailed it, multiple power amps require multiple channels of discrete bandwidth.

escapemcp wrote:This is something I have actually tested and I believe it to work.

So take all that filter theory crap of the last 100 years and toss it out the window because Bristol's got this one?



If you need to go any cheaper than a single DCX....well...

Radian wrote: And for more giggles see what the phase response is doing also.

Yes, I mentioned this, as I was unsure how it would affect it, which is why I am asking you guys.

And if you have any links, or even google search terms to explain this, I'd appreciate them. I'm still learning (aren't we all???) and so some good pointers of what to look would help greatly.

I don't have SMAART....yet.

But all you need to do is run your suggested filters in VST and take a listen for yourself.

On my MacBook, I've downloaded a program called "Play" that utilizes all of the Mac OS X built-in VST (DSP) modules.

That and a good set of headphones and your personally set to explore the many facets of good vs bad sound.

The problem with the logic of the original topic is that it's putting the cart before the horse.

The round-about way of doing things as described above is the result of using the wrong tool for the job.

Both are a requirement for pro sound, but you can apply EQ in many places along the signal chain...you only apply the crossover filters once, right before the power amps.

Everything needn't be all under one roof either. You can acquire RTA in a standalone device if need be. You can EQ the signal upstream if need be (on the laptop, decks, or mixer for example).

Without digressing too much into definitions... There are at least two major processors in any given system. An active crossover filter network controls the power amps...it affects the power response of the system. EQ is used for tailoring the frequency response of the signal.

escapemcp,

First up, congratulations on your resourcefulness. If you hadn't explained how you achieved what you did and the results, I wouldn't have believed it.

My problem is this: this thread has already got somebody (who has yet to start building) thinking from the outset they only need a DEQ, and not the DCX.

I would like to say that was not your intent, I know you're trying to learn as we all are, but in some ways this also is a justification for not using the right tool for the job.

What you have missed is the intended purpose of the Dynamic limiter. Yes the Dynamic limiter also exists on the DCX. The "brick wall" limiter section of the DCX however does not appear in the DEQ.

The intended purpose of the Dynamic limiter is to control a narrow band of frequencies and limit them when they reach a set threshold.
If you know a certain frequency is going to cause feedback at a certain gain point, you can set the dynamic limiter so that it's gain never exceeds that point at that frequency or narrow band of frequencies. This produces less interference on overall sound, because if you EQ'ed that frequency right out, or used the FBD to pick it up, it may be detrimental to overall system sound/response.
Dynamic as a word in terms of music is often used, we all have favourite songs that go from soft to loud and back again. As an engineer or system operator we have to control certain problems and this is the function of the dynamic limiter, often only seen in dynamic songs.

What you have done with the Dynamic limiter is something much broader, and isn't that functions intended use.
Sure, you're results are good
Luck perhaps?

The other thing though, is you have to be aware, especially in forums like this, that something seen in black and white is gospel, simply because that person knows not enough, or perhaps nothing at all.
So perhaps it may have been better if you had posted it up as a theory...

Very interesting thread.

Getting ready to build in the next week, and cant decide which unit I'll grab first. I'll end up with both I expect