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Getting a sub for my Nad 7155

A

Audio_Nub

New Member
Hi all! I’ve browsed these forums for awhile finding answers to my various questions as I attempt to put together a great system for music without destroying my bank account. This is my first post, and I’m unsure if I’m posting in the right place, but here goes!

I have an Nad 7155 with a pair of klipsch r-15m that I really like and another pair that I’m not sure what they are and they’re ok, but the klipsch are way way better. They are a terrible match for each other as the klipsch have sensitivity of 94 and the others are around 88. Will be looking for speakers to pair with the r15 eventually, but that is for another time.

I’m looking to get a sub for this system, and came across the klipsch spl-100 powered unit. I have tried to figure out if powered is necessary for my set up and frankly, all the terminology is a little over my head. So, do I need a powered sub? If not, what do I need in order to make use of an unpowered sub? How do I go about hooking it up?
 
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You are better off getting a powered sub. There's a much better selection, and it's more difficult to match a passive sub to a pair of speakers that it wasn't originally designed for. Additionally, if you can find a subwoofer with a high-pass filter (either on speaker level, or, more commonly, line level connections), you can take the low bass away from your main speakers, which should allow your system to play louder and/or cleaner. Since your amp has preamp out/main in connections, you can wire a subwoofer with a high pass filter between those connections, then adjust the sub as you see fit. You'll just need two pairs of long stereo RCA patch cords.

Many subwoofers only have inputs and not outputs, so those won't give you the same benefit. However, a subwoofer with inputs and outputs but no high pass filter is no better than a subwoofer with inputs only.

Here's a thread with a little more info.
 
swechsler said:
You are better off getting a powered sub. There's a much better selection, and it's more difficult to match a passive sub to a pair of speakers that it wasn't originally designed for. Additionally, if you can find a subwoofer with a high-pass filter (either on speaker level, or, more commonly, line level connections), you can take the low bass away from your main speakers, which should allow your system to play louder and/or cleaner. Since your amp has preamp out/main in connections, you can wire a subwoofer with a high pass filter between those connections, then adjust the sub as you see fit. You'll just need two pairs of long stereo RCA patch cords.

Many subwoofers only have inputs and not outputs, so those won't give you the same benefit. However, a subwoofer with inputs and outputs but no high pass filter is no better than a subwoofer with inputs only.

Here's a thread with a little more info.
Click to expand...

Thank you for your reply, and the link. That is all very helpful information! So the sub I am looking at is powered, and it also has:
- variable low-pass crossover
- phase switch
- line level/lfe inputs.

So it would seem that it doesn’t have any output to return to the mains, and is therefore not going to remove the low frequencies from my main speaker signals, correct?
Is phase switch just a control for the upper frequency limit that the sub will push?
I think I get the gist of low-pass vs high-pass.. filters? But the crossover bit is confusing, I’ve seen it everywhere. Any further illumination would be greatly appreciated!
Thanks again!!
 
A low-pass crossover allows lower frequencies to pass. Similarly, a high-pass crossover allows higher frequencies to pass. Almost all powered subwoofers have low pass crossovers so they don't try to reproduced frequencies higher than they should (the ones that don't are typically designed to work with an external crossover).

Crossover simply means where the frequencies cross over from one frequency to the other. There is always some overlap; if you set the crossover frequency to 80 hz, for example, it doesn't mean that at 81 hz, that frequency will not get sent to the sub. It's a slope, rated in dB/octave, and that slope is part of the design of the sub. Continuing with this example, if the crossover is 12dB/octave (a typical value), then a 160hz signal will be 12dB down compared with the 80 hz signal, assuming they started out at the same level coming from your amp.

There are similar crossovers inside your speakers, although obviously they are unpowered.
 
swechsler said:
A low-pass crossover allows lower frequencies to pass. Similarly, a high-pass crossover allows higher frequencies to pass. Almost all powered subwoofers have low pass crossovers so they don't try to reproduced frequencies higher than they should (the ones that don't are typically designed to work with an external crossover).

Crossover simply means where the frequencies cross over from one frequency to the other. There is always some overlap; if you set the crossover frequency to 80 hz, for example, it doesn't mean that at 81 hz, that frequency will not get sent to the sub. It's a slope, rated in dB/octave, and that slope is part of the design of the sub. Continuing with this example, if the crossover is 12dB/octave (a typical value), then a 160hz signal will be 12dB down compared with the 80 hz signal, assuming they started out at the same level coming from your amp.

There are similar crossovers inside your speakers, although obviously they are unpowered.
Click to expand...

Thanks again for your quick reply!
That concept is a little hard for me to grasp, but I think it’s starting to make sense. So the filter is between the input signal that the sub receives and the action of the woofer, meaning it’s withholding all or a portion of the higher frequencies (depending on whether it has crossover) and only sending the lower end and a sort of sliding scale of the higher lows to the woofer itself. That about it?

In that case then, a sub with a high pass filter and outputs would take the line level signal and remove a portion of the low frequencies before passing it along to the output, right?
 
The 7155 has pre-out/main in. I would get a pair of Y connectors and use those to feed the sub. That way your bass controls and volume controls will work to the sub as opposed to having to go to the sub if you want more/less bass and volume adjustment.
 
teal'c said:
The 7155 has pre-out/main in. I would get a pair of Y connectors and use those to feed the sub. That way your bass controls and volume controls will work to the sub as opposed to having to go to the sub if you want more/less bass and volume adjustment.
Click to expand...
I have come across mention of Y connectors in other posts but I’m afraid I don’t understand how or where I would be using them.

Also would this solution still send full signal with bass to my main speakers? I would prefer to cut the bass to my main speakers to get more clarity at high volumes which is the main purpose of adding a sub to my system. I definitely don’t mind having to control the sub separately, in fact I think I would like to be able to have separate controls as I listen to a wide array of music and many genres have wildly different needs.
Thanks for your reply!
 
Hmm, I may be wrong but didn't NAD build in a simple crossover network for bass control into the 7155? I'd download the manual but I'm not a member of their 'club', or whatever it is.
 
teal'c said:
You use them on the pre-out/main in connections. Yes it sends the same signal as before, only reduced because it's been divided in two.. It's the cheap way.
If you want to spend more money...
This is for automobile, but it still applies.
https://www.crutchfield.com/S-51gSNMbja3o/learn/crossover-faq-car-audio.html
Click to expand...
Ok I like cheaper too lol. And would a powered sub still be recommended in this case? I’m assuming it allows me to get a less expensive unit without the high pass and output?
 
Audio_Nub said:
Ok I like cheaper too lol. And would a powered sub still be recommended in this case? I’m assuming it allows me to get a less expensive unit without the high pass and output?
Click to expand...

I don't have subs in the house. I run Cerwin Vega.
 
Subwoofers should normally be set-and-forget, assuming the aim of your system is accuracy. If you're trying to get massive bass for an EDM party, well that's something else entirely.

Parts Express sells some inline high-pass crossovers for not much money, which is something you could use if your chosen sub doesn't have one built in. Based on the specs of your speakers, the 70hz model would probably work well for you.

The way you would connect it is remove the jumpers on the back of the amp, connect Y cables to the preamp out jacks, connect one side of each Y to a patch cord which goes to the subwoofer. The other side of the Y goes to the high-pass crossover (if you choose to use one), then to the main in jacks.
 
Knucklehead said:
Hmm, I may be wrong but didn't NAD build in a simple crossover network for bass control into the 7155? I'd download the manual but I'm not a member of their 'club', or whatever it is.
Click to expand...
There is no sub out on this receiver. Here's the manual, and here's a pic of the back panel.


533622-nad_7155_am_fm_stereo_receiver_operating_service_manuals_pdf_more.jpg
 
swechsler said:
Subwoofers should normally be set-and-forget, assuming the aim of your system is accuracy. If you're trying to get massive bass for an EDM party, well that's something else entirely.

Parts Express sells some inline high-pass crossovers for not much money, which is something you could use if your chosen sub doesn't have one built in. Based on the specs of your speakers, the 70hz model would probably work well for you.

The way you would connect it is remove the jumpers on the back of the amp, connect Y cables to the preamp out jacks, connect one side of each Y to a patch cord which goes to the subwoofer. The other side of the Y goes to the high-pass crossover (if you choose to use one), then to the main in jacks.
Click to expand...
Haha, that is not the case... these days.
I think I finally get it. Thank you so much for your help!! Getting to this point on my own may never have happened. So much appreciation.

I will do some shopping and find out what ends up being the best solution for my needs, and post here if I have further questions. Will definitely update when I get it all together and working!

Thanks again!

Teal - thanks for the crossover faq link. I found my way there once but it was over my head at the time. It is making much more sense this go around, thanks again!
 
Ok guys, ive decided on the R-100sw sub to go with my system. Again it is going to be paired with r-15m bookshelf speakers. I’m going with the inline high pass configuration and am trying to decide between the 100 hz and the 150 hz high pass. I’m leaning heavily towards the 150 as the speakers go down to 57 and the sub goes up to 120. Is this a good idea?
 
150Hz seems high. With the sub also set with a 150Hz high pass, you might start to hear bass coming from it. That can kill the illusion of sound from the main speakers. In most HT systems, 80Hz is considered the normal crossover frequency, so I'd stick with 100Hz, at the highest.
 
StimpyWan said:
150Hz seems high. With the sub also set with a 150Hz high pass, you might start to hear bass coming from it. That can kill the illusion of sound from the main speakers. In most HT systems, 80Hz is considered the normal crossover frequency, so I'd stick with 100Hz, at the highest.
Click to expand...
I’m splitting the preamp signal and feeding it to the sub and the other half of the split is going through the inline high pass back to the main ins. As far as i know there is no high pass happening in my sub, can you please explain that? Thanks in advance!
 
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