Using subs with SCM19A

ATC & other manufacturers design parameters, technical queries etc
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Using subs with SCM19A

Postby highstream » Thu Dec 06, 2018 11:36 pm

In order to keep the weight and cost of adding a pair subs to SCM19A's, I picked up a pair of barely used JL Audio e-110's earlier this year that I'm finally about to install. The speakers are driven from a PS Audio Directstream dac, so no separate preamp. The downside of the weight/cost issue is that the JLA's have unbalanced (RCA) inputs/outputs. That basically gives me two ways to hook them up:

- series: RCA's to the subs, crossover, RCA/XLR adapter to the 19A's.
Upside: lets each speaker do what it's best at; Downside: completely lose XLR benefit for ATC's

- parallel: separate runs from the dac to each speaker, adjusting only the subs' xovers
Upside: ATC's get XLR advantage; Downsides: ATC's still full range, Directstream's output impedance is substantially increased with XLR & RCA outputs being used

Which option would you think would likely return the best SQ?

Eventual alternative: Use the parallel method and add something like a DSPeaker Anti-Mode 2.0 before the speakers; it has XLR ins/outs and also DSP. Another possibility would be the CR-1, an excellent xover but is three times the cost and without digital room adjustment capabilities.

Thanks,

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Re: Using subs with SCM19A

Postby MattSPL » Sat Dec 08, 2018 11:22 am

Hi highstream,

I would invest in a minidsp umik-1 microphone(£100) and download Room EQ Wizard software which is free. You will be able to measure the frequency response of your speakers and subs in your room as well as loads of other useful features.

Will you be able to move the subs around the room at all? You will need to get the subs and speakers time aligned, otherwise you can introduce a smearing of the bass which will take away from the ATC’s articulate sound. If you introduced one of the crossover options you mentioned above, you could add delay to the speakers that way if necessary and also remove any room mode peaks.

Do you have the cables to try different options of connecting everything up?
I’ve run speakers full range and just adjusted the sub to suit for years. You can get good results with this, but the last few years since getting the Umik-1 I have added a crossover and removed the lower bass from the speakers. I now cross the speakers and subs at 50hz and it’s the best integration ive had so far.

Cheers
Matt
Sony BDP-S790 > Matrix Quattro Dac > Digidesign RM2's with SB Acoustics drivers > 2 x DIY Dayton Audio UM18-22 Sub

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Re: Using subs with SCM19A

Postby highstream » Sat Dec 08, 2018 12:30 pm

Thanks Matt. Hadn't heard of the miniDSP. Looks like a bargain ($75 + shipping in the States). What xover are you using? JL Audio's CR-1 is reputed to be excellent but is also pricey. It makes a lot of sense on the face of it to run through a xover of some kind, even if only that of the subs. The latter was my original thinking. It's just that the weight/cost factors ruled out getting the better subs with XLR ports. That's where the idea of getting the DSPeaker Anti-Mode 2.0 entered, although some users have reported flattening of sound from their main speakers with that unit. Aside from that, searching around PS Audio forums some more, it appears, contrary to my OP, that increased impedance is not normally an SQ problem using the DirectStream's XLR and RCA outputs, at least with shorter runs (mine are 1.5m max).

The photos linked below show the elongated structure of my living room (leading to dining area behind the camera). As you can see, there isn't much space behind the center A-V stand and none on the right. The speakers were set up for listening on the close viewing end of the sofa. Hence, my plan has been to put the subs next to the 19A's, to the inside. That loses optimal placing, but should gain with optimal timing.

https://1drv.ms/f/s!AqsCKHVTj0ydnCmxvrqg_cfAq-LQ

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Re: Using subs with SCM19A

Postby MattSPL » Sat Dec 08, 2018 12:59 pm

I use a BSS fds334T. It’s a speaker management system used in live sound setups and nightclubs. I run a pair of xlr cables from my Dac into the BSS and then fun xlr’s to my speakers and subs from it. Ive been told that these type of EQ’s are detrimental to the sound quality, but I’ve listened with and without this in my system and can say it is much better in the system. This is my living room, not a treated music room, so it’s possible if you’ve a studio or good room, such a device may show some ill effects to the system sound.

I have added 2.5ms delay to my speakers to align with my subs and a 50hz high pass filter to the speakers to remove the bass below that. As my speakers are 2 way, this helps greatly by freeing up the mid/bass driver and it’s amp and has improved midrange resolution and enabled the speakers to play much louder on bass heavy material. I also applied a filter at 91hz and 130hz to remove peaks in the bass. I have a nasty peak around 40hz in my room but that is now taken care of by adding a filter there in the subwoofers amp software. I use an inuke600dsp with 2 DIY subs.

There is a lot of work in measuring and properly EQing the setup, it takes practice to know what adjustments cause what results, but it’s part of the hobby for me. I usually get a good base result quickly, then make adjustments over a weekend, then often leave everything for a month or 2 before fine tuning more once I’m familiar with the sound.

Minidsp have just released this https://www.minidsp.com/products/stream ... series/shd
It’s actually a Dac too, but can be fed an Analogue signal from your Dac and just used as dsp to feed the speakers and subs separately. Looks like a great bit of kit, but ideally you’d want to try one first.

Edit: Thanks for the pictures. I would definitely get the Umik-1 and measure your room as I’m sure even slight differences in position of speakers and subs would make big differences.

Cheers
Matt
Sony BDP-S790 > Matrix Quattro Dac > Digidesign RM2's with SB Acoustics drivers > 2 x DIY Dayton Audio UM18-22 Sub

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Re: Using subs with SCM19A

Postby highstream » Sun Dec 09, 2018 10:43 am

Thanks for the info. The BSS fds334T is a discontinued model and is a rack mount. I wonder if the miniDSP 2x4 Balanced model doesn’t essentially do the same thing, i.e., work as a DSP and crossover with balanced ins/outs. It’s only 48 Hz sampling though, which limits it for playing some better audio files. They don’t have a mixed output version until the more costly 4x10.

As for the umik-1, I’m not seeing yet how I’d attach it for volume control how from my Win 7 latop to the dac, as the dac does not have RCA inputs, but only optical, coax (used), XLR, USB, 2xI2S (one in use). I can use an adapter to XLR, but would that change anything in the umik’s results?

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Re: Using subs with SCM19A

Postby MattSPL » Sun Dec 09, 2018 11:11 am

The minidsp 2x4 would do a similar job to my BSS unit. The newer minidsp unit I linked in my last post would be better and includes auto room calibration too.

The umik-1 connects to your pc with a usb cable and then you feed your Dac with a usb cable from the pc to generate the frequency sweeps from the REW software.
Sony BDP-S790 > Matrix Quattro Dac > Digidesign RM2's with SB Acoustics drivers > 2 x DIY Dayton Audio UM18-22 Sub

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Re: Using subs with SCM19A

Postby highstream » Sun Dec 09, 2018 4:22 pm

My desktop PC with extra USB ports is not nearby, hence my query, which I’ve raised with miniDSP.

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Re: Using subs with SCM19A

Postby MattSPL » Sun Dec 09, 2018 4:43 pm

highstream wrote:My desktop PC with extra USB ports is not nearby, hence my query, which I’ve raised with miniDSP.


I think a multi USB port adapter might work.
Sony BDP-S790 > Matrix Quattro Dac > Digidesign RM2's with SB Acoustics drivers > 2 x DIY Dayton Audio UM18-22 Sub

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Re: Using subs with SCM19A

Postby highstream » Sun Dec 09, 2018 5:23 pm

Perhaps a 3.5 mm headphone to XLR cable would be a solution.

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Re: Using subs with SCM19A

Postby MattSPL » Sun Dec 09, 2018 7:10 pm

highstream wrote:Perhaps a 3.5 mm headphone to XLR cable would be a solution.


Yes, that might work.
Sony BDP-S790 > Matrix Quattro Dac > Digidesign RM2's with SB Acoustics drivers > 2 x DIY Dayton Audio UM18-22 Sub

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Re: Using subs with SCM19A

Postby 1ATC4NAL » Mon Dec 10, 2018 7:24 pm

Highstream:

I've been using a miniDSP 2x4 for a few years as a crossover between powered 20s and 2 15" subs.

The 2x4 (I bought the single ended version) is pretty easy to use and set up. FWIW, as I understand it ATC prefer to "correct" outside of the digital domain. While that might be better - I had a C4 with 5 10A speakers and it was amazing - the 2x4 makes for a good result, too.

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