• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

dbx 1231 Graphic EQ Review

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
39,487
Likes
179,768
Location
Seattle Area
This is a review and detailed measurements of the dbx 1231 stereo balanced Graphic Equalizer. It is on kind loan from a member and costs US $499.
dbx 1231 Graphic Equalizer Review Balanced.jpg


Isn't this an attractive box or what? Makes you want to sit there and just play with all those sliders! Careful though as setting them all back to zero is very time consuming. Fortunately there is a bypass button. Connectivity is extensive in the back:
dbx 1231 Graphic Equalizer Review Balanced back panel XLR.jpg

You can even use bare wire if you want!

Note: Harman owns dbx. Our company, Madrona Digital, buys some of their product lines but not these. Still, feel free to read any bias in my subjective remarks.

dbx 1231 Measurements
Let's start with EQ bypassed and input/output of 4 volts:
dbx 1231 Graphic Equalizer Measurements.png


Distortion is at -105 dB which is very good for the class. Don't like the power supply noise but they are at -118 dB so we can ignore them. Turning on the EQ but keeping all the sliders at 0 shows the penalty of the full pipeline:
dbx 1231 Graphic Equalizer EQ Active  Measurements.png


We are right at noise floor of 16 bit audio so not bad still. Here is our signal to noise ratio which is impacted the most:

dbx 1231 Graphic Equalizer SNR Measurements.png


Frequency response is flat in audible band with EQ bypassed:
dbx 1231 Graphic Equalizer frequency response Measurements.png


It is hard to get rid of the channel mismatch due to notches in the gain control with the pot itself being fully variable. Repeatability is hard as well for the same reason.

I was pleased to see it handle up to 9 volts input before clipping:
dbx 1231 Graphic Equalizer THD vs Level Measurements.png


IMD distortion is respectable with EQ bypassed and not too bad with it active:
dbx 1231 Graphic Equalizer IMD Measurements.png


Crosstalk is excellent either way: (better than most amplifiers)
dbx 1231 Graphic Equalizer Crosstalk Measurements.png


I was disappointed to see a rise in distortion at low frequencies:
dbx 1231 Graphic Equalizer THD vs freq Measurements.png


Conclusions
Good to see the word "professional" has a meaning here in delivering a low distortion and noise graphic EQ. My memories of consumer units was that they were hiss factories. Not so here. This is a quality piece with reasonable price to match it for analog lovers.

Note that in general, graphic equalizers are poor at dealing with room modes or speaker correction. You need parametric EQ for that. The dbx 1231 has a lot of bands so you may be able to get close with it but still not an optimal tool.

I am going to recommend dbx 1231 graphic eq if you need such a device.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

Tom C

Major Contributor
Forum Donor
Joined
Jun 16, 2019
Messages
1,105
Likes
960
Location
USA
Thank you for this Amir! There’s been a bit of talk lately about these on the forum, and I expect a number of members are appreciative of this effort.
Nice price, too!
 

Rja4000

Major Contributor
Forum Donor
Joined
May 31, 2019
Messages
1,822
Likes
2,177
Location
Liège, Belgium
This is a review and detailed measurements of the dbx 1231 stereo balanced Graphic Equalizer. It is on kind loan from a member and costs US $499.
View attachment 219631

Isn't this an attractive box or what? Makes you want to sit there and just play with all those sliders! Careful though as setting them all back to zero is very time consuming. Fortunately there is a bypass button. Connectivity is extensive in the back:
View attachment 219632
You can even use bare wire if you want!

Note: Harman owns dbx. Our company, Madrona Digital, buys some of their product lines but not these. Still, feel free to read any bias in my subjective remarks.

dbx 1231 Measurements
Let's start with EQ bypassed and input/output of 4 volts:
View attachment 219633

Distortion is at -105 dB which is very good for the class. Don't like the power supply noise but they are at -118 dB so we can ignore them. Turning on the EQ but keeping all the sliders at 0 shows the penalty of the full pipeline:
View attachment 219634

We are right at noise floor of 16 bit audio so not bad still. Here is our signal to noise ratio which is impacted the most:

View attachment 219635

Frequency response is flat in audible band with EQ bypassed:
View attachment 219636

It is hard to get rid of the channel mismatch due to notches in the gain control with the pot itself being fully variable. Repeatability is hard as well for the same reason.

I was pleased to see it handle up to 9 volts input before clipping:
View attachment 219637

IMD distortion is respectable with EQ bypassed and not too bad with it active:
View attachment 219638

Crosstalk is excellent either way: (better than most amplifiers)
View attachment 219639

I was disappointed to see a rise in distortion at low frequencies:
View attachment 219640

Conclusions
Good to see the word "professional" has a meaning here in delivering a low distortion and noise graphic EQ. My memories of consumer units was that they were hiss factories. Not so here. This is a quality piece with reasonable price to match it for analog lovers.

Note that in general, graphic equalizers are poor at dealing with room modes or speaker correction. You need parametric EQ for that. The dbx 1231 has a lot of bands so you may be able to get close with it but still not an optimal tool.

I am going to recommend dbx 1231 graphic eq if you need such a device.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Hi Amir
Thanks for this review.
Nice to see that here.

For such a device, an important question is: what kind of graphic EQ correction does this one bring ?
Is that a constant Q ? Or a vary-Q ?
A simple frequency response test at 4 levels on the same graph would bring the answer (and measure the amount of correction): for, say, 1kHz, level at 0, 1/2 max, max, 1/2 min, min.

Another big difference between graphical EQs is: if I push, say, 1kHz to max, then cut 1.25kHz to min and 1.6kHz to max, what is my level at 1.25kHz ?
Some EQ will have level at the middle frequency to 0dB, which may be confusing.

(More explanations between constant Q and vary-Q here)
(EDIT: Another interesting explanation here
and here an example of an asymmetric EQ)

EDIT:
An example of "Q check" measurement

Here, the RME ADI-2 Pro fs R. I tried different boost/cut levels with a "Peak" EQ, 1kHz, Q=9.9, at level -12dB, -6dB, 0dB, +6dB and +12dB
As I've fixed the RME's Q, we see very well the effect of a "Constant Q" EQ: The correction bandwidth is larger if you increase Boost/Cut
Some EQ are more or less keeping the bandwidth constant (and therefore vary the Q with level) or do even more complex tricks (like the Proportional Q in Klark Teknik EQs)

2022-07-22 10_20_40-Greenshot.png


Here is what we could get if the EQ is trying to keep the +/-3dB bandwidth constant
Q is now 5.3 at +/- 6dB and 9.9 at +/-12dB

2022-07-22 10_34_48-Greenshot_Crop.png


Some EQ are even asymmetric, using a different profile for boost and for cut.
(picture from Presonus)

AsymetricEQ_Plot.png


So this simple measurement gives us a lot of information...


I've also performed the comparison of the second test I listed:
Alternate max boost/cut on adjacent faders:
Here, still with the RME, I've set 3 EQ to 1kHz -12dB, 1.25kHz +12dB and 1.6kHz -12dB

First with a Q of 9.9 (Max)
2022-07-22 10_46_44-Greenshot.png


then with a much lower Q of 2.0
2022-07-22 10_46_17-Greenshot.png


The different is stunning, isn't it ?

(NB: It would be more "readable" with frequencies centered around 1kHz, so 800Hz, 1kHz and 1.25kHz)
 
Last edited:

DualTriode

Addicted to Fun and Learning
Forum Donor
Joined
Oct 24, 2019
Messages
749
Likes
501
Amirm,

I am glad to see you review this equalizer.

I have been using similar Rane and Klark dn370 equalizers for quite awhile.

It help to select drivers that fairly smooth Frequency Response.

I use JBL 2226 woofers, JBL 2123 mids and JBL M2 waveguides with D2 drivers.

I use a Behringer RTA 61 band thing with a microphone to dial in the sliders.

Thanks DT
 

DanielT

Major Contributor
Joined
Oct 10, 2020
Messages
3,493
Likes
3,018
Location
Sweden - Слава Україні
Amirm,

I am glad to see you review this equalizer.

I have been using similar Rane and Klark dn370 equalizers for quite awhile.

It help to select drivers that fairly smooth Frequency Response.

I use JBL 2226 woofers, JBL 2123 mids and JBL M2 waveguides with D2 drivers.

I use a Behringer RTA 61 band thing with a microphone to dial in the sliders.

Thanks DT
But how do you do when you fix FR with your EQ? It's fixed frequencies you change with a physical EQ, I mean ...hm are you lucky that where you need to change/ fix FR right there you have an EQ band/slider or....well how do you actually do it?

Edit:
Q values are also fixed, right?By the way, I see that Rja4000 in #8 brings up the same things.:)
 
Last edited:

DanielT

Major Contributor
Joined
Oct 10, 2020
Messages
3,493
Likes
3,018
Location
Sweden - Слава Україні
Thanks Amir, but why no test what it's made for, that is: EQing?
Exactly, take a speaker where EQ would make sense . How well does dbx 1231
correct the FR then? How close does it dot, so to say?:)

It might go beyond Amir's test of it itself but it would have been fun to see.
(Don't do it Amir, spend your time on something else:))
 
Last edited:
OP
amirm

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
39,487
Likes
179,768
Location
Seattle Area
Thanks Amir, but why no test what it's made for, that is: EQing?
Do what there? Play with the slides and show that the response changes??? That part is a given. My goal was to see how transparent it is. And I tested that with and without EQ being on.
 
Joined
Dec 11, 2021
Messages
78
Likes
26
excellent these are the sort of reviews I would like to see most they tell us if these older anaolouge products are worth buying
 

Chrise36

Addicted to Fun and Learning
Joined
Dec 23, 2018
Messages
764
Likes
247
Can you try eq any headphones and compare digital to analog eq
 

BeerBear

Active Member
Joined
Mar 9, 2020
Messages
137
Likes
141
Good to see some production gear being tested!

Nice "legacy" product. But, in the digital domain, one can have better "equalizers" for 0.00 $, and without sacrificing space.
I agree, but some people strongly believe that hardware has some "magic sound" that can't be reproduced with software... maybe it's the magic of noise, IDK...
It would be nice to do some tests of this, as much as it's possible anyway, in a controlled/scientific manner.

For such a device, an important question is: what kind of graphic EQ correction does this one bring ?
Is that a constant Q ? Or a vary-Q ?
It's constant Q according to this post: https://gearspace.com/board/showpost.php?p=14356767&postcount=6
 

Rja4000

Major Contributor
Forum Donor
Joined
May 31, 2019
Messages
1,822
Likes
2,177
Location
Liège, Belgium
Good to see some production gear being tested!


I agree, but some people strongly believe that hardware has some "magic sound" that can't be reproduced with software... maybe it's the magic of noise, IDK...
It would be nice to do some tests of this, as much as it's possible anyway, in a controlled/scientific manner.


It's constant Q according to this post: https://gearspace.com/board/showpost.php?p=14356767&postcount=6
I found nothing in the specs or manual about it.

So measuring it would be nice, I think.

Not only you can check if that's actually Constant Q, but also what Q value it is, and what's the maximum boost/cut in dB.
(Some EQ behave differently for boost and cut)
 

DSJR

Major Contributor
Joined
Jan 27, 2020
Messages
1,929
Likes
2,475
Location
Suffolk Coastal, UK
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.
 

PeteL

Major Contributor
Joined
Jun 1, 2020
Messages
2,654
Likes
2,732
Nice "legacy" product. But, in the digital domain, one can have better "equalizers" for 0.00 $, and without sacrificing space.
The fact that it's not aimed at digital only signal chain don't make it a legacy product. It's a current product. Many of us have a mix of analog and digital sources and use an analog preamp. It's kinda nice that it appears to compete in performance of something like a MiniDsP 2X4 Hd when you account the full AD-DA. Many of us don't listen to 24 bit content neither. Graph EQ like that are limitative I admit, but I have to say that if I could find for reasonable price a combination of Analog Parametric EQ and crossover for subs without significant payback in noise and distortion, I would trade my Mini DSP in a heartbeat. It's so much more intuitive convenient, and fun to use. Cool to look at too, you can find now racks nicely enclosed in wood finished chassis that look happily at home in actual living spaces, if you have the room of course.
 
Top Bottom