03-Oct-2021, 09:16
Connection-wise, yes. Subwoofer crossover disabled, yes.
However, the low-pass frequency/slope setting for the mono line outs on the Experts is a variable, as is the low-level gain on the subwoofers. They will all interract with each other, and the "best" settings are going to be a function of your main speakers, room, and tastes.
So getting them "right" is an iterative process, and slightly hampered by the configurator/SD card process to change the first two settings. In your case everything is doubled, but I think it's very likely you'll want the same settings for both subs both on the Experts and on their plate amps, so that makes it somewhat easier.
So here's how I made it easier for myself to establish the rolloff frequency for the Experts - using a software signal generator I played specific frequency tones into the main speakers alone to understand the nature of their rolloff in-room, listening for volume by ear. (I have a measurement microphone and RTA, but I trust my ears)
In my case bass is very full, clean, and even from 40hz down to 27hz; below that there is steep rolloff. This suggested a steep (4th order) low-pass filter would be appropriate on the Expert, specified at approximately 27hz. So I set this up on the SD card and played a 20hz tone, using this to adjust the low level gain on the subwoofer to make the 20hz tone the same level as the 27hz. I then went up and down in frequency over the crossover again to check for evenness, and made further adjustments to the level. I identified that there was a slight "hole", a relative quietness, at 27hz, so I went through the configurator process again to raise the crossover point to 30hz and repeated the above calibration and checks, noting that the response was now smooth over the 26hz-30hz region. For different speakers, if they needed more help in the 30-40hz region, I might have gone to a 3rd-order or 2nd-order filter here instead.
I then listened to a couple of tracks that I find very revealing of low frequency evenness. These are not tracks with overwhelming subsonics - it's easy for those to sound impressive. The best for this purpose are those with some subsonics and also substantial musical detail in the 40hz-120hz range - the range which is so easy to ruin with an incorrectly set up subwoofer, causing mush and boom, which is far worse than having no subsonic bass at all. Another small adjustment to subwoofer low-level gain resulted from this.
Then I lived with the settings for a few days, as it does take a while to get used to the changed bass. Perhaps further adjustments. I've found that if I get the crossover setting right, I tend to want to increase the low level gain to enjoy the delicious bottom octave, whereas if I get it wrong I tend to want to reduce the gain to stop the 40hz+ region being damaged.
A couple of further points to make:
The REL crossover goes very low, but is not a steep rolloff and my mains are unusually capable in the deep bass. My previous mains have been less capable here, and the REL crossover suited them better than it does the A5s.
Considerable care is needed when playing bass sine tones into the system, because it represents a sustained stress situation which is unusual in music (except for a sustained 32ft organ pedal note). So I suggest starting at very low volumes (e.g. -60 on the Expert volume) and increasing to a moderate volume - I find that's enough to check evenness. Amps and woofers will work hard, so bear this in mind and don't unnecessarily prolong the test!
However, the low-pass frequency/slope setting for the mono line outs on the Experts is a variable, as is the low-level gain on the subwoofers. They will all interract with each other, and the "best" settings are going to be a function of your main speakers, room, and tastes.
So getting them "right" is an iterative process, and slightly hampered by the configurator/SD card process to change the first two settings. In your case everything is doubled, but I think it's very likely you'll want the same settings for both subs both on the Experts and on their plate amps, so that makes it somewhat easier.
So here's how I made it easier for myself to establish the rolloff frequency for the Experts - using a software signal generator I played specific frequency tones into the main speakers alone to understand the nature of their rolloff in-room, listening for volume by ear. (I have a measurement microphone and RTA, but I trust my ears)
In my case bass is very full, clean, and even from 40hz down to 27hz; below that there is steep rolloff. This suggested a steep (4th order) low-pass filter would be appropriate on the Expert, specified at approximately 27hz. So I set this up on the SD card and played a 20hz tone, using this to adjust the low level gain on the subwoofer to make the 20hz tone the same level as the 27hz. I then went up and down in frequency over the crossover again to check for evenness, and made further adjustments to the level. I identified that there was a slight "hole", a relative quietness, at 27hz, so I went through the configurator process again to raise the crossover point to 30hz and repeated the above calibration and checks, noting that the response was now smooth over the 26hz-30hz region. For different speakers, if they needed more help in the 30-40hz region, I might have gone to a 3rd-order or 2nd-order filter here instead.
I then listened to a couple of tracks that I find very revealing of low frequency evenness. These are not tracks with overwhelming subsonics - it's easy for those to sound impressive. The best for this purpose are those with some subsonics and also substantial musical detail in the 40hz-120hz range - the range which is so easy to ruin with an incorrectly set up subwoofer, causing mush and boom, which is far worse than having no subsonic bass at all. Another small adjustment to subwoofer low-level gain resulted from this.
Then I lived with the settings for a few days, as it does take a while to get used to the changed bass. Perhaps further adjustments. I've found that if I get the crossover setting right, I tend to want to increase the low level gain to enjoy the delicious bottom octave, whereas if I get it wrong I tend to want to reduce the gain to stop the 40hz+ region being damaged.
A couple of further points to make:
The REL crossover goes very low, but is not a steep rolloff and my mains are unusually capable in the deep bass. My previous mains have been less capable here, and the REL crossover suited them better than it does the A5s.
Considerable care is needed when playing bass sine tones into the system, because it represents a sustained stress situation which is unusual in music (except for a sustained 32ft organ pedal note). So I suggest starting at very low volumes (e.g. -60 on the Expert volume) and increasing to a moderate volume - I find that's enough to check evenness. Amps and woofers will work hard, so bear this in mind and don't unnecessarily prolong the test!
1000 Pro / Magico A5 / REL Studio III
