[ritzry2]

I purchased the GR Research Servo Sub Kit 2 (http://gr-research.com/servosubkit2.aspx) a few months ago and I was planning on building my own enclosures but I don't have access to my shop now. I was wondering if anyone here has enclosure MDF pieces or could build them for me to purchase, so I can build my kit. I'll veneer it later. Thanks, Ryan

[ritzry2]

Rythmik is going to apply the kit cost to a completed sub purchase, so I am good. Enclosures are NO longer needed.

A couple other sub related questions I have:

(1) I am considering the following subs from Rythmik: L12, F12G, and F8. I am primarily interested in 2-channel and quality of bass for music, but I will do HT some as well. My room is 16x12 and I am running X-Statik speakers. I plan on purchasing two subs. Which sub will blend best with the X-Statik's? L12 is attractive from its price; if it gives 95% of F12, then that is attractive. And I am not sure how F8, with two 8" drivers, would compare to L12 and F12, with one 12" driver each.

(2) What is the preferred method of connection for subs, for 2-channel? Rythmik documentation recommends using low level input when available while other companies recommend using high level inputs. Maybe there is not a significant difference either way, and maybe the recommendation is specific to the way the sub was designed. It's confusing, though, with lack of consensus.

[mlundy57]

Rythmik is going to apply the kit cost to a completed sub purchase, so I am good. Enclosures are NO longer needed.

A couple other sub related questions I have:

(1) I am considering the following subs from Rythmik: L12, F12G, and F8. I am primarily interested in 2-channel and quality of bass for music, but I will do HT some as well. My room is 16x12 and I am running X-Statik speakers. I plan on purchasing two subs. Which sub will blend best with the X-Statik's? L12 is attractive from its price; if it gives 95% of F12, then that is attractive. And I am not sure how F8, with two 8" drivers, would compare to L12 and F12, with one 12" driver each.

You will get the best results with the F12G. The L12 is an entry level sub and the HX300 amp it uses is very limited compared to the A370 series amp in the F12G. The F12 has an aluminum cone while the F12G has the GR-Research paper cone driver. I have both an F12 and the GR-Version of the F12G (the GR sub kit 2 is an F12G in a custom cabinet). Overall I prefer the F12G version. The F8 is not going to have the low end (below 30Hz) performance of the F12/G. The A370 series amps have more connection options and a lot more flexibility in dialing the subs in than the L12.

(2) What is the preferred method of connection for subs, for 2-channel? Rythmik documentation recommends using low level input when available while other companies recommend using high level inputs. Maybe there is not a significant difference either way, and maybe the recommendation is specific to the way the sub was designed. It's confusing, though, with lack of consensus.

That depends on you preamp, low frequency preference, and connection options. If you want to get the best from your X-Statiks you will want to keep the lowest frequencies (ones they can't reproduce) away from them. You do this with an inline filter between the preamp and power amp for the X-Statiks. If you do this you will have to use the line level inputs of the A370 amps since the speaker outputs are not going to have the low bass frequencies. If your preamp has two sets of outputs this is easy. One set goes to the inline filter then on to the power amp and the other set of outputs go to the subs. If your preamp only has one set of outputs you have to split the signal. You can do this either with Y connectors or by building the filter with a by-pass leg.

[dlparker]

Is Rythmik sending you an enclosure?

[ritzry2]

mlundy57, thank you for this information -- very helpful!

That depends on you preamp, low frequency preference, and connection options. If you want to get the best from your X-Statiks you will want to keep the lowest frequencies (ones they can't reproduce) away from them. You do this with an inline filter between the preamp and power amp for the X-Statiks. If you do this you will have to use the line level inputs of the A370 amps since the speaker outputs are not going to have the low bass frequencies. If your preamp has two sets of outputs this is easy. One set goes to the inline filter then on to the power amp and the other set of outputs go to the subs. If your preamp only has one set of outputs you have to split the signal. You can do this either with Y connectors or by building the filter with a by-pass leg.

I have two outputs: a RCA and XLR out. The A370PEQ has a HPF built into it so, if I get this amp on my sub, I could do the following:

DAC/PREAMP --> A370PEQ LINE IN
A370PEQ HPF OUT --> AMP IN

Does the above make sense?

FYI, I sent an email to Rythmic regarding the low-level vs high-level inputs, and Brian (owner) confirmed low-level is preferred to keep the signal as pure as possible and he provided several reasons why this was the case.

[ritzry2]

Is Rythmik sending you an enclosure?

No, they are not sending me the enclosure. I sent them the kit I had, which was still in its original packing. I am going to purchase a completed sub and then they are going to discount based off the kit price.

[dlparker]

So you're getting one of their stock subs?

[ritzry2]

So you're getting one of their stock subs?

Yes, that's correct.

[mlundy57]

mlundy57, thank you for this information -- very helpful!

I have two outputs: a RCA and XLR out. The A370PEQ has a HPF built into it so, if I get this amp on my sub, I could do the following:

DAC/PREAMP --> A370PEQ LINE IN
A370PEQ HPF OUT --> AMP IN

Does the above make sense?

FYI, I sent an email to Rythmic regarding the low-level vs high-level inputs, and Brian (owner) confirmed low-level is preferred to keep the signal as pure as possible and he provided several reasons why this was the case.

The high pass filter on the A370PEQ amp is noisy. Don't use it. If you have XLR outs you can get the A370XLR3 amp. It has low level RCA and XLR inputs (no high level input and no HPF out). My current preamp has balanced outputs so I"m upgrading my A370PEQ3 amps to A370XLR3s. Got the amps in, now have to get time to build boxes and wire them up.

[ritzry2]

The high pass filter on the A370PEQ amp is noisy. Don't use it. If you have XLR outs you can get the A370XLR3 amp. It has low level RCA and XLR inputs (no high level input and no HPF out). My current preamp has balanced outputs so I"m upgrading my A370PEQ3 amps to A370XLR3s. Got the amps in, now have to get time to build boxes and wire them up.

Got it, thanks! Do you have any recommendations for HPF that would be good start with (e.g. experiment, etc.)?

[mlundy57]

Got it, thanks! Do you have any recommendations for HPF that would be good start with (e.g. experiment, etc.)?

Determine the size of cap you need based on the frequency you want the signal to the X-Statiks to be -3dB at and the input impedance of your power amp. Then get either Soniccap Platinum or Miflex KPCU caps from Danny and build the filter. If you are building a balanced filter you will need two caps for each channel. You will also need XLR connectors. How many depens on whether you are adding a by-pas leg or not.

[ritzry2]

Determine the size of cap you need based on the frequency you want the signal to the X-Statiks to be -3dB at and the input impedance of your power amp. Then get either Soniccap Platinum or Miflex KPCU caps from Danny and build the filter. If you are building a balanced filter you will need two caps for each channel. You will also need XLR connectors. How many depens on whether you are adding a by-pas leg or not.

On the X-Statik page it states that "-3db down is 48Hz for an average room". My amp has an impedance of 8 ohm (or 4 ohm). Using these numbers, the size of the cap would be 414.67 farads. My X-Statiks have the Sonicap and Mills resistance upgrade; not sure if that impacts -3db. And, I am not sure what the ideal frequency cutoff should be. I doubt you want to cutoff exactly at 48Hz but rather higher to give some extra headroom for the speakers. I've never built a HPF; is it as simple as passing a signal through the cap or is it more involved than that?

[mlundy57]

On the X-Statik page it states that "-3db down is 48Hz for an average room". My amp has an impedance of 8 ohm (or 4 ohm). Using these numbers, the size of the cap would be 414.67 farads. My X-Statiks have the Sonicap and Mills resistance upgrade; not sure if that impacts -3db. And, I am not sure what the ideal frequency cutoff should be. I doubt you want to cutoff exactly at 48Hz but rather higher to give some extra headroom for the speakers. I've never built a HPF; is it as simple as passing a signal through the cap or is it more involved than that?

The 4 and 8 ohm you're thinking of is output. The input impedance of the power amp is going to be something like 50kOhms or 100kOhms. It's going to be a kOhm number, not Ohms. You should be able to find it in the amplifier's specifications.

If it were me I'd use a cap size that would would have the input signal -3 at 40Hz, 60Hz, or 80Hz. Somewhere in that neighborhood. You aren't going to get exact. And that doesn't matter. This is not a brick wall type filter. It's a first order filter so will have a 6dB per octave rolloff. What that means is that if the input signal to the power amp is -3 at 80Hz it will be -9 at 40Hz (-3-6=-9) and -15 at 20Hz. The crossover point to the subs will probably be in the 40-60Hz range depending on room gain. All you are trying to accomplish with the filter is keep the X-Statiks from having to deal with low bass frequencies. This will allow the X-Statiks to play louder, cleaner than they would if they were sent a full range signal.

Personally I'd aim for -3 around 80Hz for the X-Statiks but that's just me.

Mike

[ritzry2]

The 4 and 8 ohm you're thinking of is output. The input impedance of the power amp is going to be something like 50kOhms or 100kOhms. It's going to be a kOhm number, not Ohms. You should be able to find it in the amplifier's specifications.

If it were me I'd use a cap size that would would have the input signal -3 at 40Hz, 60Hz, or 80Hz. Somewhere in that neighborhood. You aren't going to get exact. And that doesn't matter. This is not a brick wall type filter. It's a first order filter so will have a 6dB per octave rolloff. What that means is that if the input signal to the power amp is -3 at 80Hz it will be -9 at 40Hz (-3-6=-9) and -15 at 20Hz. The crossover point to the subs will probably be in the 40-60Hz range depending on room gain. All you are trying to accomplish with the filter is keep the X-Statiks from having to deal with low bass frequencies. This will allow the X-Statiks to play louder, cleaner than they would if they were sent a full range signal.

Personally I'd aim for -3 around 80Hz for the X-Statiks but that's just me.

Mike

Thanks, sounds good. I checked the specs and the input impedance is 100kOhms. To crossover at 80Hz, would I need a 19.9nF capacitor? How do I wire this up?

I saw there were pre-built HPF's from Harrison Labs, Dayton Audio, HSU, etc. Not sure what the quality is like.

[mlundy57]

Thanks, sounds good. I checked the specs and the input impedance is 100kOhms. To crossover at 80Hz, would I need a 19.9nF capacitor? How do I wire this up?

I saw there were pre-built HPF's from Harrison Labs, Dayton Audio, HSU, etc. Not sure what the quality is like.

Yes, for 80Hz at 100kOhms it would be .02uF or 20nF. I haven't used any of the pre-builts so I can't say what the quality is like, though I doubt that are using caps in the same quality range as Sonicap Platinums or Miflex KPCU.

[ritzry2]

Yes, for 80Hz at 100kOhms it would be .02uF or 20nF. I haven't used any of the pre-builts so I can't say what the quality is like, though I doubt that are using caps in the same quality range as Sonicap Platinums or Miflex KPCU.

Great. The connection is as simple as: PRE OUT --> CAP --> AMP IN on one RCA Line (Right or Left) and then the other line connects as normal from pre to amp?

For the cap, I found this, Miflex KPCU 0.022uF 600VDC Copper foil Poly/Paper in Oil (http://www.soniccraft.com/product_info.php/miflex-kpcu-0022uf-600vdc-copper-foil-polypaper-in-oil-p-5293)

[mlundy57]

Each channel, right and left, need a filter between the pre and power amps. For single ended (RCA) connections you will need two caps. If you use the balanced connections you will need four caps, one for each of the two hot legs in each channel.

That cap will work.

[ritzry2]

Each channel, right and left, need a filter between the pre and power amps.

That cap will work.

Awesome, I will give it a try. Thanks for your time and guidance -- very helpful!

[Glenng78]

I had a pair of XLRs built by soniccraft. The quality of the product was excellent , and the service was very quick and easy. Just give them your -3 requirements and your impedances, and they will give you some options on caps, and XLR parts and also wire. High grade , mid grade, and lower grade options.
Highly recommended

[PeterPiper]

I was jut about to buy the GR Servo Sub Kit 2 as well.  So to be clear, you are sending the GR Kit 2 to Rythmic and Rythmic is going to use its sub box and install the GR Kit 2 in the box and send it back to you?  Thank you.