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dbx 1231 Graphic EQ Review

Rja4000

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On the dBx 530 above, the "Q" is set by a ring around the gain knob. (If I'm not wrong)

NSEQ2-Web-1960.jpg


This one is more classic:
You have a center frequency control, then "Q" (width) control, than the boost/cut

Here with 2 channels


(Photo from Millennia web site)
 

Jaxjax

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These things were all but outlawed in the dark days of UK audiophoolery. My take then was that if bass was boomy due to a speaker design issue (some BeeBeeCee legacy models for example), just cutting the bass down didn't cure the issue, it just made it less of a problem. No equaliser would really fix harshness up top either..

Fast forward to today and I was all set to get one to cure a terminal dullness in the sound here. Turns out it was my hearing that needed equalising, not the system, causing the problem and it's 'fixed' for me, at least for now :) Amazing that reflected sound is now far more prominent in a beneficial way, something an equaliser can't fix really.
mmmmmm My experience is that PEQ can fix most anything. I use Pro analog PEQ's because after I measure, I like to twist dials instead of messing with my laptop all the time. Elysia makes very transparent EQ's & they will indeed fix room problems. I actual much prefer the analog pro units over digital & I run DSP active monitors in main. Once I find the problems & correct & then fine tune by ear & it only takes just a bit as a good eq should. Just how I do it & it works for me. I would never run a system without an analog peq, good ones are start at 1k, Drawmer etc, & then they go up up up. to the finely crafted mastering PEQ's.
 

DSJR

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What I didn't understand back then, was that the main UK maker removing tone controls stil had a buffer circuit in the preamp with fixed filters inline. I can't prove it, but I swear these original basic filters reacted with the ultrasonic mush some early CD players fed out down the line. Once the hf filter was replaced with a four pole type, 'digital' began to sound a lot better when played through this maker's amps (less 'hashy,' but of course that's a subjective view with no proper backup...
 

DanielT

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What I didn't understand back then, was that the main UK maker removing tone controls stil had a buffer circuit in the preamp with fixed filters inline. I can't prove it, but I swear these original basic filters reacted with the ultrasonic mush some early CD players fed out down the line. Once the hf filter was replaced with a four pole type, 'digital' began to sound a lot better when played through this maker's amps (less 'hashy,' but of course that's a subjective view with no proper backup...
Speaking of tone controls, I miss the loudness functionality on many new amplifiers. It was more or less a standard function on amplifiers in the past, or?
I know there are new ones that have it, but still.

It's really smart to be able to switch on loudness when playing at low volume. I think.:)


Edit:
There are also those who think it is a pointless function to have.
 
Last edited:

Jaxjax

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hey! great new forum!
pro-oriented gears have two very nice stereo full parametric eqs (a little off topic but we're already talking about analog eq) that I would LOVE to see measured:
Elysia Xfilter (in various "packages", 500, standalone and rack versions) and Drawmer 1974 (only rack version). Both are not "vintage" even they're analogue.
Anyone so kind? :)
I run an Elysia Xfilter in my main & could not be without it or I would send it in.
 

gnarly

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Unfortunately only if you’re using a computer as a source. If you’re not your options are more limited. I use an RME ADI-2 DAC for headphone EQ since I don’t have a computer in my headphone chain, but I’d love it if someone made a dedicated digital-in/digital-out parametric EQ box with a lot of memory slots and more PEQ bands than the RME has.

I almost hate to mention this....a Q-Sys Core110f running QSys Designer software ..... because i hear supply chain issues have disrupted new deliveries out to Q1 2023, and used 110f's have been selling above the list price at $3300. Pre covid, $1250 or so was all anybody had to pay on ebay, with a little patience.
But despite current supply/price issues, i believe it helps to be aware of options like QSys, as I think this is where the DSP market may be heading.

Anyway...QSys is open architecture design. You draw up a schematic on a PC/MAC using QSys Designer, and then the software compiles the schematic into Linux running on the hardware Core110f.

Equalizer capability now.....

graphic:
The Graphic Equalizer provides from 6 bands with 2 octaves per band up to 61 bands with 1/6th octave per band. Each band can be adjusted from -20dB to +20 dB.

flat top graphic parametric:
same band capacity as graphic
(I'll contrast these two types of graphic in a minute...

parametric:
The Parametric Equalizer is a variable equalizer allowing you to individually adjust the Gain, Bandwidth and center Frequency of up to 32 frequency bands. You can also Bypass individual bands. Master controls, affecting all bands, include Bypass, Invert, Mute and Gain. Additionally, you can change any or all of the bands to either a high or low-shelf equalizer.

flat top parametric:
same band capacity as parametric
(will contrast the two parametrics too)

Any of these EQs can have multiple instances in the design schematic. Iow, you can have a bank for varying track tonality, and another one for room EQ, etc.
Each EQ can be mono, stereo, or multichannel.



Ok, here's a screenshot of graphic vs flattop graphic.
I chose 16 two-thirds oct bands for a simple view.....(61 1/6th oct bands makes for one wide screen lol)

Same eqs setting are in both.
Note how the flattop gets rid of the ripple in adjacent bands. And how the phase shift is a bit more gentle.
It's not a big deal, but cool to have i guess.

Qsys graphic EQ examples.JPG



Ok again, now parametric vs flattop para.....this one is more interesting imo....

Settings are not the same, because the two are not trying to do the same task, like in the graphic.
The Parametric is just to show the settings block. Note you can use either BW or Q, which are linked together. Up to 32 bands.

The flattop allows each side of the EQ to have its slope set independently of the other side.
A couple of examples are shown, an asymmetric at 420Hz, and a symmetric flat top at 3.6kHz.

I've found the flattop para works very well for quasi-anechoic speaker tuning like the 420Hz example, and also for tone control when used flattop and shallow side slopes.


Qsys Para EQ examples.JPG



Saved the best for last :)

Any control from the design schematic, from simple overall volume to any of these EQ settings, can be placed onto a control screen on a Win or OS device, that is connected to same network as the Core 110f . You can put any remote control you want on an Iphone for example. And customize the appearance/action of the control element.

I use a touchscreen PC.
Admittedly touch screen faders and knobs are not as much joy to use (for me) as real faders and knobs,
but it's kind amazing how many live sound guys are now mixing shows on tablets controlling their mixer...so i know it's mainly a matter of habit....

Hope this was interesting and not OffT...
 

kongwee

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I saw many of these EQs in small venues to EQ the stage monitors or the house speaker system. I believe that's what they are designed for, not a home "Hi-Fi" system.
Yup, this is what they used for. They can be found in studio too.
 

nagster

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this is really interesting thankyou I'll look into its successors . by the way is it relatively easy to test equipment like this it would be really useful to know if something is producing low distortion or not . what is the minimum equipment required to test gear like this? what level of distortion is considered transparent ? I assumed we should be aiming for around 115db is that to say there are distortion products at 115db below the signal level ?
If you are going to challenge the measurement from now on, we recommend the combination of a personal computer, REW, an audio interface with analog input / output, and a battery-powered true-rms multimeter.
The audio interface shown on the REW page will suffice. A multimeter that specifies the accuracy of AC voltage measurement up to 1kHz is desirable. For example, Fluke 114 can be relieved.
If the absolute value is accurate, the measurement result can be widely used.
For example, when measuring THD + N ratio of -100dB or less, a higher quality generator and higher quality ADC are required, but please consider again when necessary.
 

Chrise36

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mmmmmm My experience is that PEQ can fix most anything. I use Pro analog PEQ's because after I measure, I like to twist dials instead of messing with my laptop all the time. Elysia makes very transparent EQ's & they will indeed fix room problems. I actual much prefer the analog pro units over digital & I run DSP active monitors in main. Once I find the problems & correct & then fine tune by ear & it only takes just a bit as a good eq should. Just how I do it & it works for me. I would never run a system without an analog peq, good ones are start at 1k, Drawmer etc, & then they go up up up. to the finely crafted mastering PEQ's.
Have you tried any of the cheap ones?
 

Jaxjax

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Have you tried any of the cheap ones?
I haven't.
I think if I had to go below the Drawmer I would just stay in digital land as it works just fine too. I just prefer to use the analog units. I've only tried to improve my settings on the Elysia 1 time & landed right back where I started. It will probably not get touched again for a very long time.
 

bYOndo

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Have you tried any of the cheap ones?
the cheap ones AFAIK are only (dual) mono, graphic (not parametric) for the most, like this DBX in the OP. On the cheap land there is a few of full parametric mono (Klark Teknik comes to mind), but as for the graphics ones, even the good ones, I cannot imagine the stress of living with some channel and/or sliders mismatch on my stereo hifi system. Just my 2 cents.
 

Chrise36

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the cheap ones AFAIK are only (dual) mono, graphic (not parametric) for the most, like this DBX in the OP. On the cheap land there is a few of full parametric mono (Klark Teknik comes to mind), but as for the graphics ones, even the good ones, I cannot imagine the stress of living with some channel and/or sliders mismatch on my stereo hifi system. Just my 2 cents.
Even if you run actives there is strong possibility the speakers reft to right channels will not measure the same in the listening position. My interest is about the inherent noise of these devices mostly
 

Scrappy

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Digital EQ introduce the same phase errors. Some are linear phase but they will introduce latency, use more processing and are not so common as of now.
Latency and “pre-ringing” IIRC?
 

Scrappy

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the cheap ones AFAIK are only (dual) mono, graphic (not parametric) for the most, like this DBX in the OP. On the cheap land there is a few of full parametric mono (Klark Teknik comes to mind), but as for the graphics ones, even the good ones, I cannot imagine the stress of living with some channel and/or sliders mismatch on my stereo hifi system. Just my 2 cents.
Having a dual-mono graphic EQ is a great excuse to buy a 3D printer tho...
 

Scrappy

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Nice to see some old analog stuff getting reviewed even if for nostalgia's sake.

I am pretty sure every graphic EQ I have ever seen uses constant-Q filters so you get equal overlap in an octave/log sense. We have one of these at church (may be an earlier model) so I had to set it up. It has selectable +/-6 dB or +/-15 dB boost/cut range though as Amir said the little sliders are difficult to fine-tune. Not really a big deal for general pro use when you are not an anal audiophile correcting every 0.1 dB (like me at home ;) ). Now we have a digital board with built-in EQ (and much more) so I am not sure the old analog EQ is still in use.

I had a Soundscraftsmen (?) equalizer that used passive stages, Ls and Cs... Less hiss, but had to be very careful about hum and noise pick up, and the gain stages were not as silent as today's IIRC. I also had a few consumer units way back when and as Amir said they were usually very noisy. I even built the one that was in Popular Electronics or one of the other magazines back then. Still noisy.
I have a Fostex stereo 10-band with proportional Q, but I’ve only used it on a pair of coax Fostex speakers that desperately needed the smiley face.
 

TomK

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Yup, this is what they used for. They can be found in studio too.
Yup. If you’ve got a good / trained ear then having a decent GEQ in the signal chain for stage monitors can really save your a$$.
 
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