Should I have mixed the yellow and red rather than combining red with red and yellow with yellow? Yes. Connecting red and yellow to different channels is necessary when only one sub is being used. But it defeats a lot of the benefit that using two subs can provide, because the subs would no longer be able to reproduce low frequency information that differs between the two channels. So as I indicated in my previous post... ...electrically connect left sub red to left sub yellow, and connect that combination to the amp’s left channel +, while connecting right sub red to right sub yellow, and connecting that combination to the amp’s right channel +. And yes, properly connecting a sub or subs can be tricky, as different situations (one sub vs. two; balanced amp vs. single-ended amp; monoblocks vs. stereo amp, etc.) can call for different approaches. Best regards, -- Al |
If by "spliced them together" you mean that the red wire from one sub is electrically connected to the red wire from the other sub, and the yellow wire from one sub is electrically connected to the yellow wire from the other sub, that would be wrong.
That would result in both subs reproducing an identical monophonic signal representing the low frequency content of the sum of the two channels, rather than the left sub reproducing the low frequency content of the left channel signal, and the right sub reproducing the low frequency content of the right channel signal. So you wouldn’t be gaining most of the advantage of having two subs.
But if you just mean that they are physically bundled together, and none of the wires are electrically connected to each other, that would be ok. Or, alternatively, you could electrically connect left sub red to left sub yellow, and connect that combination to the amp’s left channel +, while connecting right sub red to right sub yellow, and connecting that combination to the amp’s right channel +. With the RCA plugs that are connected to the black wires plugged in as I described in my previous post.
Best regards,
-- Al
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Yes. The black wire would be soldered to the wrap-around piece having the little teeth in it (the part of the plug that is closest to the lower left of the photo I provided). The small circle that is further forward and is centered in the middle, which in a normal RCA cable would be used for the signal connection, should be left unconnected.
Also, as you most likely already realize, since you are using two subs the red and yellow wires from each sub would BOTH be connected to the amp's positive output terminal for the corresponding channel. In other words, the red and yellow wires from the sub on the left would connect to the amp's + output terminal for the left channel, and the red and yellow wires from the sub on the right would connect to the amp's + output terminal for the right channel. The RCA plug to which the black wire from the left sub is connected would plug into the amp's RCA input for the left channel, and the RCA plug to which the black wire from the right sub is connected would plug into the amp's RCA input for the right channel.
Best regards,
-- Al
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Fsmithjack, yes, what you said in your last post is correct. And for a typical RCA plug, such as this one (shown with its housing removed) the connection point for the ground shell is easy to distinguish from the one for the center pin once the housing is taken off. In the one shown in that photo it would be the longish part that extends out to the lower left. Best regards, -- Al |
Audiotroy 10-14-2017
Your sub hookup questions should be addressed directly to Sumiko. As the ground for the speakers on a Rel is not like a nomral ground in an electrical sense. the Rel subs read the signal from the amp like an rca cable. Hi Dave, Before I submitted my previous posts about this I had looked at the manual for the Sumiko sub. As can be seen on page 15 the recommended connection of the black wire in the Speakon cable to a "bridged (differential input) amplifier" (which obviously would also apply to a fully balanced amplifier) is to a chassis screw. That is the same as what is recommended by REL for their subs, and will work ok in most cases as I mentioned, although depending on the amp design hum may result in some cases. But connecting it to the ground shell of an RCA input connector, as I suggested, is a better approach that will certainly work well with this amp, given the mention in the amp’s manual that the RCA ground shell corresponds to signal ground. Which would be the case with almost all other amplifier designs as well, aside perhaps for some that have transformer coupled inputs. Fsmithjack, two more points on that subject, the first of which you'll be especially glad to hear: 1)The risk to the resistors that I mentioned, if the black wire were connected to the amp’s negative output terminal, would be much greater with the Magicos than with the Rethms, since the much lower efficiency of the Magicos would result in more voltage being applied across the resistors for a given listening volume. 2)If the subs were connected in that manner the risk to the resistors would arise even if the subs were turned off, since it is the ground path through them that is involved. Regards, and continued good luck! -- Al |
P.S: I just found the following statement in the manual for the X350.5, which was apparently written before the version of the amp which provides a signal ground terminal was introduced: Some powered subwoofers require an audio signal ground reference and their makers may suggest that a black speaker terminal is where this voltage reference might be found. On complementary designs, which would be typical of all power amps produced by Pass Laboratories™, this is an incorrect and unsafe assumption. On all Pass Laboratories™ power amplifiers a reference of 0 volts will be found only at pin 1 of the XLR input or at the shell of the RCA input.
Reference connections for these devices require special consideration when used with our product. If you have such a device, and wish to use it with our product, please contact our Foresthill, California factory for specific instructions.... you have been warned.
Regards, -- Al |
Glad to hear of the good progress! Regarding... I was hooking the subs before to the black terminal. Do you think if I ever hook them up again I should avoid that? I did it with my Rethm’s and it worked good but your info is great info! Assuming that the sub has a three-prong power plug, yes I would avoid connecting in that manner. To explain why, I’ll first mention that in good designs circuit ground (also referred to as signal ground) will often be connected to chassis through a low value resistor, commonly somewhere between 10 and 100 ohms. In some cases circuit ground and chassis may even be connected directly together (i.e., through zero ohms), although that is poor design because it results in susceptibility to ground loop issues. Also, if the component has a three-prong power plug chassis will usually be connected to AC safety ground. So in cases where BOTH the sub and the amp have three-prong power plugs, connecting the negative output terminal of a fully balanced amp to the negative speaker-level input of a sub (which is presumably connected to the sub’s circuit ground in most cases) would result in the signal that is present on the amp’s negative output terminal being sent through some unknown but probably low impedance in the sub to the sub’s chassis, then to its AC safety ground connection, then through the power wiring to the amp’s AC safety ground connection, then to the amp’s chassis, then through some unknown but probably low impedance in the amp to the amp’s circuit ground. Resulting in the circuit in the amp which drives its negative output terminal probably being loaded by somewhere between 0 ohms (a direct short) and 200 ohms. If that value is low enough, obviously the amp may either be damaged or forced into a protective shutdown mode. But even if the resistors are high enough in value to avoid that kind of issue, and to prevent sonics from being affected, one or both of the resistors might eventually blow as a result of having to handle more power than they are rated to handle. I’ve seen a number of cases here where people using REL subs have reported connecting in that manner and getting away with it, presumably because the resistors were high enough in value to prevent a problem. But at best it is not good practice, and as I said it risks overheating and damaging the resistors eventually if not sooner. Continued good luck! Regards, -- Al |
Fsmithjack, thanks for posting the pix. Regarding my previous post, about sub connections, after looking at the second from the last photo I see that you don’t have them connected to the amp. I also see that your amp doesn’t provide the white signal ground terminal I referred to. After looking at some additional rear panel photos of the X350.5 via Google Images, it appears that some X350.5s were produced with that terminal (such as the one shown here), while others (including yours) were produced without it. In any event, if you do end up connecting the subs at speaker-level, as I had mentioned the black (ground) wire from each sub should not be connected to a negative output terminal of the amp, since that terminal has a full amplitude signal on it. Connecting the black wire to a chassis screw might work ok, or it might produce a lot of hum, depending on the design of the amp. But the best approach would be to solder the black wire to the ground shell of an RCA plug, leaving its center pin unconnected, and inserting the plug into an RCA input connector on the amp. Of course, to make that possible without using a y-adapter you would have to connect the Bricasti (or a preamp, if you eventually add one) via XLRs. Good luck. Regards, -- Al |
"So darn bright :( something wrong here...."
"... if this was their sound no one would like them and so many people do!" I’d have to agree that it sounds like something is wrong here. This is probably a long shot, but it seems worth asking: Have you been running the Sumiko subs with the Magico speakers? If so, and if you are connecting the subs at speaker level, have you been connecting the black wire of the Speakon cable to the white signal ground terminal on the rear of the amp, which is where it should be connected? If instead you have been connecting it to a negative output terminal of the balanced Pass amp, which is a mistake that seems to often be made when connecting powered subs to the outputs of balanced amps, I’m envisioning that in combination with the low impedance of the S5 (as opposed to the impedance of your previous speakers) an ultra-sonic oscillation could conceivably result, that would manifest as brightness/harshness. And that kind of effect might account for the sensitivity to the amp’s power cord that you mentioned. Just a thought. Regards, -- Al |
