• 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!

Quick measurements of dbx DriveRack PA2 speaker management system

ol_mcdonald

Member
Joined
Feb 8, 2020
Messages
43
Likes
22
Do you think if I get Driverack PA2 to set a crossover for my Sonodyne SM300 and Sonodyne SLF 312 Sub, will I notice any audible transparency loss?
I have used one for a little over a year now and love it. I use it to split signal between 3 amps to my sub and bi amped mains. Silent, totally.
 

birkbott

Member
Joined
Oct 11, 2019
Messages
99
Likes
49
I may have missed it in the original post but what setting did you use for the input switch? I’m assuming in a hifi setting you would use the -10dBV but just want to check.
 

birkbott

Member
Joined
Oct 11, 2019
Messages
99
Likes
49
I may have missed it in the original post but what setting did you use for the input switch? I’m assuming in a hifi setting you would use the -10dBV but just want to check.
I should note that I’m using XLR from a Schiit Freya+ and to NC400 Monoblocks. Based on what I’ve read elsewhere I’ll try with the +4 setting and see what happens. The subs will have to use XLR to RCA adapters but I think that will be ok.

I haven’t had good luck trying to incorporate DSP or pro audio gear into my setup before but we’ll see how it goes.
 

ol_mcdonald

Member
Joined
Feb 8, 2020
Messages
43
Likes
22
Manuals says for “consumer” applications use -10dbV, which is what I use also.
 

birkbott

Member
Joined
Oct 11, 2019
Messages
99
Likes
49
So I got my PA2 last night and so far I am impressed with the sound at the listening position even with just the crossover applied (no EQ) it’s better than trying to run my mains full range with sub support.

My only complaint is that there is hiss at the tweeter when I get close to it. It is not audible at the listening position, however, my system is dead silent without the PA2 in the chain.

I tried toggling the +4/-10 switch but it made no difference.

Does anyone know if there is a global gain setting in the PA2 that will reduce the noise floor? Or can I just expect that a unit like this will introduce some noise?

If that’s the case are there any units like this that don’t introduce noise? I’ve had this issue with miniDSP units as well.

I’m using a Schiit Freya + and NC400 Monoblocks. All XLR cables. My speakers are X-LS Encores so not overly sensitive. Subs are Rhythmik servos via RCA.
 

mdsimon2

Major Contributor
Forum Donor
Joined
Oct 20, 2020
Messages
1,454
Likes
1,838
Location
Detroit, MI
So I got my PA2 last night and so far I am impressed with the sound at the listening position even with just the crossover applied (no EQ) it’s better than trying to run my mains full range with sub support.

My only complaint is that there is hiss at the tweeter when I get close to it. It is not audible at the listening position, however, my system is dead silent without the PA2 in the chain.

I tried toggling the +4/-10 switch but it made no difference.

Does anyone know if there is a global gain setting in the PA2 that will reduce the noise floor? Or can I just expect that a unit like this will introduce some noise?

If that’s the case are there any units like this that don’t introduce noise? I’ve had this issue with miniDSP units as well.

I’m using a Schiit Freya + and NC400 Monoblocks. All XLR cables. My speakers are X-LS Encores so not overly sensitive. Subs are Rhythmik servos via RCA.

The noise performance shown in the tests is rather middling so hiss is not particularly surprising. I assume the Freya is upstream of the PA2 not downstream? A downstream analog preamp could help with noise but you will need a multichannel one which makes things more difficult. Lower gain amplifier would certainly help as well. Otherwise a miniDSP SHD or Flex have better spec'd AD / DA from a noise perspective (much better than the miniDSP 2x4HD / 4x10HD).

Michael
 

birkbott

Member
Joined
Oct 11, 2019
Messages
99
Likes
49
The noise performance shown in the tests is rather middling so hiss is not particularly surprising. I assume the Freya is upstream of the PA2 not downstream? A downstream analog preamp could help with noise but you will need a multichannel one which makes things more difficult. Lower gain amplifier would certainly help as well. Otherwise a miniDSP SHD or Flex have better spec'd AD / DA from a noise perspective (much better than the miniDSP 2x4HD / 4x10HD).

Michael
Correct it’s upstream. I had the SHD on my list but decided to go with this one based on price, I’m able to return it so maybe I’ll give the SHD a shot.
 

mdsimon2

Major Contributor
Forum Donor
Joined
Oct 20, 2020
Messages
1,454
Likes
1,838
Location
Detroit, MI
Correct it’s upstream. I had the SHD on my list but decided to go with this one based on price, I’m able to return it so maybe I’ll give the SHD a shot.

Look at the Flex, much cheaper than the SHD ($550 for balanced Flex vs $1250 for SHD) and has a spec'd analog to analog SNR of 116 dB(A) at 4 V output. Knocking that down to 3 dB to convert from A weighting to unweighted (assuming flat noise distribution) gives 113 dB.

It is unclear what level the tests in this thread were run at (and there will be some noise contribution from the DAC / ADC used) but assuming they were at 20 dBu (7.75 V) the 94 dB SNR measured translates to 88 dB at 4 V for an apples to apples comparison to the Flex.

Needless to say the Flex should be substantially lower noise.

Also what is your source? Do you have a DAC upstream of the Freya? If so you could go digital in to the Flex, skip the Freya and have even better noise performance.

Michael
 

birkbott

Member
Joined
Oct 11, 2019
Messages
99
Likes
49
Look at the Flex, much cheaper than the SHD ($550 for balanced Flex vs $1250 for SHD) and has a spec'd analog to analog SNR of 116 dB(A) at 4 V output. Knocking that down to 3 dB to convert from A weighting to unweighted (assuming flat noise distribution) gives 113 dB.

It is unclear what level the tests in this thread were run at (and there will be some noise contribution from the DAC / ADC used) but assuming they were at 20 dBu (7.75 V) the 94 dB SNR measured translates to 88 dB at 4 V for an apples to apples comparison to the Flex.

Needless to say the Flex should be substantially lower noise.

Also what is your source? Do you have a DAC upstream of the Freya? If so you could go digital in to the Flex, skip the Freya and have even better noise performance.

Michael
Look at the Flex, much cheaper than the SHD ($550 for balanced Flex vs $1250 for SHD) and has a spec'd analog to analog SNR of 116 dB(A) at 4 V output. Knocking that down to 3 dB to convert from A weighting to unweighted (assuming flat noise distribution) gives 113 dB.

It is unclear what level the tests in this thread were run at (and there will be some noise contribution from the DAC / ADC used) but assuming they were at 20 dBu (7.75 V) the 94 dB SNR measured translates to 88 dB at 4 V for an apples to apples comparison to the Flex.

Needless to say the Flex should be substantially lower noise.

Also what is your source? Do you have a DAC upstream of the Freya? If so you could go digital in to the Flex, skip the Freya and have even better noise performance.

Michael
I like the price of the flex but I don’t love the TRS connections. I may try the SHD from a US vendor that has a return policy. I’m really interested to hear if the noise is less or not.

I have a Raspberry Pi via Schiit Modi 3+ (But I have an SU-9 on the way) along with a vinyl setup going into the Freya. I like the ability to switch between the passive/buffer/tube gain on the Freya so I’ll probably keep it in the signal chain.

I just want a clean crossover/EQ and I’m surprised it’s so hard to find honestly.
 

kipman725

Active Member
Joined
Jul 6, 2020
Messages
167
Likes
160
I would guess that the problem is that you have excess gain from your power amps and should introduce some passive attenuation between the PA2 and the power amps. You should aim that a couple of dB below maiximum output of the PA2 the power amp clips. In my system I have 14dB attenuation between my DSP and amplifiers if I didn't have this the noise floor would be +14dB and I hear significant hiss.

I calculate the Hypex amp clipping at 8.24dBu input and the PA2 is rated for 20dBu output so you should put 10dB attenuators between the two, this should be percived as halving the hiss volume.
 
Last edited:

birkbott

Member
Joined
Oct 11, 2019
Messages
99
Likes
49
I would guess that the problem is that you have excess gain from your power amps and should introduce some passive attenuation between the PA2 and the power amps. You should aim that a couple of dB below maiximum output of the PA2 the power amp clips. In my system I have 14dB attenuation between my DSP and amplifiers if I didn't have this the noise floor would be +14dB and I hear significant hiss.
Thanks for this but I decided to return my unit and go with a miniDSP SHD. It’s arriving today so I’ll see how it goes.
 

kipman725

Active Member
Joined
Jul 6, 2020
Messages
167
Likes
160
The SHD is more matched to the amplifier "Max output level: 2V RMS unbalanced, 4V RMS balanced"
 

ol_mcdonald

Member
Joined
Feb 8, 2020
Messages
43
Likes
22
Gain adjustments are easily made and instructions can be found in the manual, page 19 section 3. Aside from that dbx tech is available and helpful if needed. Mine is totally silent with no noise…not a hint of hiss. Just needs proper set up.
 
Last edited:

Alonso28

Member
Joined
Aug 6, 2022
Messages
13
Likes
2
PA2 doesn't have a digital path through it, so analog inputs are converted to digital, processed, and then converted back. There's no way to avoid the ADC/DAC cycle, which means whatever distortion and noise it adds will be added on top of whatever is there at the input. Now, these may add up in different ways, but ultimately, if you put in the output of a DAC that's fairly clean, say 120dB SINAD, you'll likely get, at best, a 94dB SINAD out of PA2. Not that this is a poor result by any means: it's better than most amplifiers can deliver. Some newer dbx models allow all digital processing, without the analog conversion. So you could use a really good DAC after the unit, if you feel that a very high SINAD is a must. Personally, I wouldn't worry about it.
Thank you for all this usefull data! I have a similar question about DACS. I have a home "hifi" system, kef ls50 meta, musical fidelity m6si, an svs sub and bluesound node. I bought the dbx driverack to "correct" the response curve of the system because of my room imperfections. I feel that i lost some details, microdinamics with the dbx ( I feel more details even with the basic DAC inside the Node), do you think its because the por quality of the xlr cables I have now? (im getting good ones), or should I get also a DAC to improve the signal quality going out of the Dbx? Sorry for such a basic question.
 
OP
pkane

pkane

Major Contributor
Forum Donor
Joined
Aug 18, 2017
Messages
3,475
Likes
6,010
Location
North-East
Thank you for all this usefull data! I have a similar question about DACS. I have a home "hifi" system, kef ls50 meta, musical fidelity m6si, an svs sub and bluesound node. I bought the dbx driverack to "correct" the response curve of the system because of my room imperfections. I feel that i lost some details, microdinamics with the dbx ( I feel more details even with the basic DAC inside the Node), do you think its because the por quality of the xlr cables I have now? (im getting good ones), or should I get also a DAC to improve the signal quality going out of the Dbx? Sorry for such a basic question.

I doubt DriverRack would cause some of the issues you're describing. Much more likely that the room correction curves are not done right. I would also not bother with replacing XLR cables, unless you think the current ones are not wired correctly.
 

Alonso28

Member
Joined
Aug 6, 2022
Messages
13
Likes
2
I doubt DriverRack would cause some of the issues you're describing. Much more likely that the room correction curves are not done right. I would also not bother with replacing XLR cables, unless you think the current ones are not wired correctly.
Its like the information the speakers used to deliver, has been slightly but noticeable reduced. Some lack of clarity and definition is percieved, less annoying peaks in some frequencies yes (because of the auto eq), but seems at the expense of clarity. I thought it might be in part because of the very very cheap cables i used, if its not what do you suggest I should do? I was also thinking in a DAC after the dbx Line out. Thank u a lot!!!
 
OP
pkane

pkane

Major Contributor
Forum Donor
Joined
Aug 18, 2017
Messages
3,475
Likes
6,010
Location
North-East
Its like the information the speakers used to deliver, has been slightly but noticeable reduced. Some lack of clarity and definition is percieved, less annoying peaks in some frequencies yes (because of the auto eq), but seems at the expense of clarity. I thought it might be in part because of the very very cheap cables i used, if its not what do you suggest I should do? I was also thinking in a DAC after the dbx Line out. Thank u a lot!!!

First and foremost, if you're using room correction curves, you need to make sure these are set correctly. The automatic routine in DriveRack isn't great, it's enough for quick and simple set up but not meant for critical listening. Also how you enter your corrections and what options you enable in the DriveRack can easily make audible differences. That's where I would look first, before considering anything else like DAC or cables.

I would also double-check that the output is set to the same level with and without DriveRack -- when levels are not exactly the same (can be due to analog or digital components, or both) the result will sound worse for the component that has a slightly lower output.
 

Alonso28

Member
Joined
Aug 6, 2022
Messages
13
Likes
2
First and foremost, if you're using room correction curves, you need to make sure these are set correctly. The automatic routine in DriveRack isn't great, it's enough for quick and simple set up but not meant for critical listening. Also how you enter your corrections and what options you enable in the DriveRack can easily make audible differences. That's where I would look first, before considering anything else like DAC or cables.

I would also double-check that the output is set to the same level with and without DriveRack -- when levels are not exactly the same (can be due to analog or digital components, or both) the result will sound worse for the component that has a slightly lower output.
Thank u again!! What do you mean "when you enter your corrections"? I used the auto eq, then I made some adjustments in the manual section. As it deletes the manual corrections when you go out and in from the auto EQ, I set this adjustments into the parametricEq. I also set the crossover in 65 hz, corresponding near to the roll off from the speakers.
For the out line from the dbx i used HIGH to go into the amp, and LOW (in mono) to go directly into the sub, as it is an active sub. I also chose PASIVE in the dbx configuration.
Should I choose full range and only use HIGh, and then go out to the sub from the amp?
I will check the output levels, do you mean in watts?
 
Last edited:
OP
pkane

pkane

Major Contributor
Forum Donor
Joined
Aug 18, 2017
Messages
3,475
Likes
6,010
Location
North-East
Thank u again!! What do you mean "when you enter your corrections"? I used the auto eq, then I made some adjustments in the manual section. As it deletes the manual corrections when you go out and in from the auto EQ, I set this adjustments into the Eq. I also set the crossover in 65 hz, corresponding near to the roll off from the speakers.
For the out line from the dbx i used HIGH to go into the amp, and LOW (in mono) to go directly into the sub, as it is an active sub. I also chose PASIVE in the dbx configuration.
I will check the output levels, do you mean in watts?

There's a more manual way to measure and enter the corrections that involves a microphone and a PC with some free software to measure and correct. This is more advanced, but is likely to produce much better results. If you're interested in putting more effort into this and getting better results, take a look here:

https://www.audiosciencereview.com/...om-measurement-tutorial-for-dummies-part-1.4/

and here

https://www.audiosciencereview.com/...om-measurement-tutorial-for-dummies-part-2.5/

Matching levels is better done with a multimeter, measuring output voltage at a certain frequency, say at 1kHz, at the speaker terminals or at the output of the amplifier.
 
Top Bottom