[birkbott]

Birkbott,

You mentioned space concerns. In which way?

OB subs require the ability to pull your main speakers out at least 3' from the wall. Is that possible in your case?

If not, the sealed servos would be the way to go. You can use them as speaker stands, but most likely your speakers and room will sound better if the subs are located elsewhere in the room.

Well it's a typical small-to-medium sized living room type setup so we have the TV mounted on the wall with an entertainment center under it. On either side of that I have about 16"W x 18"D to fit speakers. I had a pair of Spatial Audio M4s in there and as much as I loved them I always felt like the low frequencies were hindered by not having enough room to breathe. When I first got them I thought I could live with it but I found myself missing the low end.

In a previous incarnation I had some sealed bookshelf speakers from Selah and a single sealed SVS sub but I never felt like I could integrate them well and the (perhaps psychological) imbalance of having only one sub bothered me, so I've been thinking about a 2.2 system for a while.

As for locating them elsewhere in the room I doubt that would be possible. My spouse is already at "eye-roll" stage with this project as it is I don't think I could rearrange the living room to accommodate subs in other locations. Also we have small kids so I need to keep things as contained/hidden as possible.

[mlundy57]

As I understand it the A370PEQ amp that comes with the Servo Sub Kit 2 has a built in fixed 80hz crossover if you're using the low level inputs between your pre and power amps.

The only thing I dislike about this setup is that you have to run interconnects from the preamp to the sub amp and then back to the power amp and then speaker wire back to the speakers so it's a lot of back and forth.

I'm considering building some Hypex NC400 monoblocks that can easily fit in the sub amp enclosures or on top of the Encores to get everything closer together. I love the sound of my Schiit Aegir but I'm afraid it will be underpowered for the Encores and I don't think I have room for 2 of them.

The consensus is that built-in high pass filter isn’t any good, dont use it. The A370PEQ3 amps I have been using don’t even have the high pass out. They have two pairs of inputs. One line in and one LFE in.  From now on when I build subs for myself I’m going to use the A370XLR3 amps since my preamp has balanced outputs. You can get the other versions of the A370 amps. Just call Danny and let him know what you want.

[Tyson]

Well it's a typical small-to-medium sized living room type setup so we have the TV mounted on the wall with an entertainment center under it. On either side of that I have about 16"W x 18"D to fit speakers. I had a pair of Spatial Audio M4s in there and as much as I loved them I always felt like the low frequencies were hindered by not having enough room to breathe. When I first got them I thought I could live with it but I found myself missing the low end.

In a previous incarnation I had some sealed bookshelf speakers from Selah and a single sealed SVS sub but I never felt like I could integrate them well and the (perhaps psychological) imbalance of having only one sub bothered me, so I've been thinking about a 2.2 system for a while.

As for locating them elsewhere in the room I doubt that would be possible. My spouse is already at "eye-roll" stage with this project as it is I don't think I could rearrange the living room to accommodate subs in other locations. Also we have small kids so I need to keep things as contained/hidden as possible.

The M4's are nice speakers, but they are nowhere near capable of the bass that dual OB Rythmik subs can put out.  I'd use dual OB subs as stands for the speakers and a nice grill cloth front and back to keep the drivers hidden.

If your spouse is decor conscious, you could paint the speakers white and use some nice colorful grills to make the more room friendly.  I've got my speakers in white with a maroon set of grills, but I think navy blue might also be nice in my setup. 

[birkbott]

The M4's are nice speakers, but they are nowhere near capable of the bass that dual OB Rythmik subs can put out.  I'd use dual OB subs as stands for the speakers and a nice grill cloth front and back to keep the drivers hidden.

If your spouse is decor conscious, you could paint the speakers white and use some nice colorful grills to make the more room friendly.  I've got my speakers in white with a maroon set of grills, but I think navy blue might also be nice in my setup.

I'm into the OB thing, I just don't think I have the space. These would be just about up against the rear wall.

I'm way ahead of you on the white paint thing. I'm planning to use Duratex with a fine roller.  My spouse is on board with that part. I have white, grey, and black grill cloth samples but navy or maroon might be cool too.

[birkbott]

The consensus is that built-in high pass filter isn’t any good, dont use it. The A370PEQ3 amps I have been using don’t even have the high pass out. They have two pairs of inputs. One line in and one LFE in.  From now on when I build subs for myself I’m going to use the A370XLR3 amps since my preamp has balanced outputs. You can get the other versions of the A370 amps. Just call Danny and let him know what you want.

That's interesting, that was my main reason for going with the A370PEQ over the HX300.

It's too bad that high quality crossovers for dual subs are so hard to find and/or expensive.

[mlundy57]

The A370 amps are much more versatile and adjustable then the HX300s. The versatility makes the A370s compatible with more preamps/amps and the adjustability makes them easier to dial in.

[birkbott]

Even at 80Hz the signal is still omnidirectional so driver direction doesn't matter. As an aside, 80Hz is the THX standard crossover point.

The numbers on the crossover dial of the sub amp don't actually correlate to a specific frequency so you can't just set the dial to 80Hz and actually have an 80Hz crossover point to subs. Having some way of measuring the signal is a lot easier than doing it by ear. I use REW.

If you are going to let your speakers roll off naturally, you want to crossover where the speakers are -6dB. With the X-LS Encores that's around 51Hz but could differ due to room gain. If you want to roll them off higher and you have a separate preamp and power amp, you can use an inline filter between the pre and power amp to change the rolloff and thereby the -6 point. If you are using a receiver with bass management, like an AVR, you can use it's bass management to set the crossover point. In this case you would connect to the LFE input on the
sub amp. This by-passes the sub's crossover controls.

Just re-reading this, is there a high pass filter that you think is good quality for raising the roll off point of the main speakers?

[mlundy57]

Just re-reading this, is there a high pass filter that you think is good quality for raising the roll off point of the main speakers?

You build it yourself. It consists of one small cap inline between the preamp and power amp. The size of the cap depends on the input impedance of your power amp and the frequency you want to be 3dB down at. Danny has a link to a calculator in this forum. I’m on my phone so I can’t cut and paste the link here. From the GR Research main page search inline filter. Since the cap size is small a really good cap is not that expensive. For single ended (RCA) connections you need one cap per channel.

[HAL]

You build it yourself. It consists of one small cap inline between the preamp and power amp. The size of the cap depends on the input impedance of your power amp and the frequency you want to be 3dB down at. Danny has a link to a calculator in this forum. I’m on my phone so I can’t cut and paste the link here. From the GR Research main page search inline filter. Since the cap size is small a really good cap is not that expensive. For single ended (RCA) connections you need one cap per channel.

And get a pair of matched value caps if you do to keep both channels the same. 

[mlundy57]

Here's the link to the post about the in-line filter calculator. It's at reply 12
https://www.audiocircle.com/index.php?topic=126480.msg1334315#msg1334315

Here's the link to the calculator
https://www.v-cap.com/coupling-capacitor-calculator.php

[birkbott]

Here's the link to the post about the in-line filter calculator. It's at reply 12
https://www.audiocircle.com/index.php?topic=126480.msg1334315#msg1334315

Here's the link to the calculator
https://www.v-cap.com/coupling-capacitor-calculator.php

Well this just keeps getting more and more interesting.

So this additional cap would be between the preamp and power amp, correct?

The input impedance on my amp is 22k so in order to have -3db at 80hz I would need a cap value of 0.09 according to the calculator. But where does that put the -6db point? An octave lower?

It seems like a pretty gradual slope I wonder about integrating it with the sub slope which is I believe is 12 db/ocatve at it's most gradual setting.

[HAL]

Here is a single pole RC high pass at 120Hz response plot. 

The -6dB down point is about 68Hz.  You can use the fraction Fc*(68/120) to find the -6dB point for a different cut off frequency for the power amp high pass.  Depends on the servo amp setting.  As long as both HP and LP -6dB points match, they should be close.

[birkbott]

Here is a single pole RC high pass at 120Hz response plot. 

The -6dB down point is about 68Hz.  You can use the fraction Fc*(68/120) to find the -6dB point for a different cut off frequency for the power amp high pass.  Depends on the servo amp setting.  As long as both HP and LP -6dB points match, they should be close.

So if I want my -6db at 80hz I would need to start the high pass at around 140hz.

I'm trying to square this with the cap calculator linked above. That calculator solves for the -3db value. Would that be half way between the two? So 110hz?

[Danny Richie]

1. Do you think dual sealed subs would integrate well with the Encores in this configuration given the space limitation?

A sealed servo sub will work great.

And yes, while open baffle is awesome, and kind of the hill around here, you don't have the space for it.

2. Do you agree that the built in 80hz crossover on the A370PEQ should not be used?

Again, don't use that. It is not a high quality cap.

3. If so do you agree that an in-line passive capacitor would be helpful in filtering some of the low-end out of the mains and would this improve sound quality?

Yes. Here is an example of one with a by-pass for the servo sub.



I would go with a .1uF for your amp. That will get you a -3db of 72Hz and allow a crossover somewhere in the 60Hz range or lower. that will be more ideal with these speakers.

4. Do you think one Schiit Aegir will be powerful enough to run the Encores (max 20W per channel into 8 ohms) or should I consider switching to something like the Vidar with more power? Or is there another power amp that you personally recommend for the encores?

It may be fine if you are not far away from them and you don't clip it on them.

5. Do you agree that a 4-pin speakon connection would be a good choice to connect the sub driver to the amp if it's in an external enclosure?

Yes, we use them for that all the time and stock them for it.

We just don't use that type of connector for anything above 200Hz.

[birkbott]

Danny thanks for the great responses as usual. 

[birkbott]

Has anyone ever tried just splicing the cap into the RCA cable?

[Jaytor]

I did this with my cables. I using balanced cables and I cut the cable about 8" from the preamp connection end and spliced in two caps on the + and - leads. I used these little ABS boxes which just snap together around two cable ends to enclose the caps and shield connection.

https://www.amazon.com/gp/product/B07MMMN2JD

- Jay

[birkbott]

This is the box I made. I realized after I had it soldered that I had it backwards so my white rcas feed the right channel an red rcas feed the left. I put a big arrow on top to remind myself which way it goes.

[birkbott]

Well, my plan has been executed:



This is the left channel, there’s an identical set up on the right channel. Didn’t get to listen to them very much but very impressed with the bass extension and evenness of the sound.

[birkbott]

Just need to finish the grills to cover everything up and we’re good to go.