Power amplifier for subwoofer

 

Bronze Member
Username: Wasserman12

Post Number: 49
Registered: Jul-06
Hi-
I've been offered a great deal on a set of NHT superzeros and the sw1s subwoofer. However, as the subwoofer is not powered, I think I will have to get both a power amplifier and a cross-over or build a cross over- is this correct? My receiver is from before subwoofers were common and therefore has no output for one. However, I understand that I can run a signal to the sub from the preamp out. I would then connect the pre-amp to a power amp designated for the sub? Is this right? And where does the cross-over fit in? Also, does the cross-over divide up the signal such that the monitors are not receiving the frequencies that are going to the sub, and does this result in more efficient use of my amps power than sending both the full signal?

Thanks for the help-
 

Gold Member
Username: Nuck

Post Number: 5215
Registered: Dec-04
Eugene, you need only a plate sub amp. Readily available from partsexpress.com

Plug and play
 

Gold Member
Username: Nuck

Post Number: 5216
Registered: Dec-04
Open the sub and check for a crossover.

Or name and model here so we can check...
 

Bronze Member
Username: Wasserman12

Post Number: 50
Registered: Jul-06
Nuck- thanks for you response-
The sub is an NHT sw1s. I can get four superzeros and the sub for $200. As I said before, i don't have subwoofer capability now, but at that price, I figured I oughta snatch that stuff up in case I want to use one in the future. The other thing is, I live in an apartment and I don't know if I oughta subject my downstairs neighbors to the bass a subwoofer could provide.
That aside-
I would prefer to use a power amp for the sub, instead of a "plate sub amp," if only because i can get one more cheaply, and I could potentially use it for other things. Are you at all familiar with the NHT subs? I read an incredibly glowing review of the NHT's and the reviewer suggested buildign a cross-over for them. Would this go between the pre-amp and the subs power amp and the monitors power amp?
Am I making sense?
Thanks again-
 

Gold Member
Username: Hawk

Highlands Ranch, CO USA

Post Number: 1035
Registered: Dec-03
eugene:

Your sub already has a crossover built into it. It is a passive sub, that is, it has no amplifier, but it does have a crossover. The way a passive sub is connected is that your main speaker cables from your receiver is connected to the sub (both L + R), and another set of apeaker cables runs from subwoofer to your speakers. The internal crossover routes the low notes to the sub and everything above say, 120 Hz for example, goes on to the speakers. This crossover point varies from manufacturer to manufacturer.

Before I can suggest a solution to your problem, however, you need to tell me what receiver you have. From your first post, I got the impression that you had a stereo receiver, which is much more limiting in what you may do.
 

Bronze Member
Username: Wasserman12

Post Number: 51
Registered: Jul-06
Thanks Hawk-
Incidentally- did you get that name from Twin Peaks?

I have a luxman R115 receiver. How is this limiting? Also- I read a description of this sub online and apparently it only has one pair of binding posts- how do you connect both speakers to it and then run them out again if this is the case?
thanks for your help
 

Gold Member
Username: Hawk

Highlands Ranch, CO USA

Post Number: 1039
Registered: Dec-03
eugene:

1. Nope--never even saw Twin Peaks, so I don't even know the reference.

2. As for your proposed speaker purchase, you have jogged my memory. NHT actually made the crossover a separate component (a very unusual arrangement, and considerably more expensive), with adjustable crossover points. You would run the speaker cables from the receiver to the crossover inputs and then run speaker cables out of the crossover to the main speakers. My recollection is that NHT and Adcom are the only two manufacturers that pushed this type of solution. This is truly "vintage" stuff, as I would guess most posters on this site have never even seen a passive sub and are no doubt scratching their heads over what we are talking about. Now, personally, I would never even consider buying such a sub without the crossover thrown in or without some assurance that I could get the crossover. Why? Well, when you wire speakers together, you are shooting in the dark with the impedence. One of the important functions of the crossover is to maintain a proper impedence load for the amp; otherwise, you could easily fry the amp.

As a long time owner of a stereo receiver, you probably don't have any idea of the advances made with A/V receivers. One of those advances is in bass management, where a crossover resides within the receiver and the sub is run off of a dedicated pre-amp out to an active sub with its own dedicated amplifier. Typically, you can adjust the crossover point within the AVR or at the sub, or both. You can also independently adjust the subwoofer's sound level, both through the receiver and through the sub's dedicated amp--this is possible since the sub runs off of a pre-out. So, unless your receiver has a dedicated pre-out for a sub, simply adding an amp to drive the sub will be a somewhat pointless act. However, if you do have a pre-out for the sub, I would strongly recommend the plate amp suggested by Nuck. It is designed to drive a sub and will have the necessary controls to adjust the crossover point and level--something you won't find on a regular power amp. Also, they cost only a little over $100, so the cost is not that great. Now, by having a crossover within the receiver, an AVR can also prevent low bass intended for the sub from going to the satellite speakers, thus muddying the sound from the speakers--this is something not easily prevented using a stereo receiver which puts out the full range to the speakers. So, that is what I mean by the use of a stereo receiver can be somewhat "limiting." It does not have these capabilities.
 

Bronze Member
Username: Wasserman12

Post Number: 52
Registered: Jul-06
thanks Hawk-
I'll think on that. However, I don't know what you consider vintage, but I understand that this sub is only about 4 years old.
Thanks again
 

Gold Member
Username: Hawk

Highlands Ranch, CO USA

Post Number: 1043
Registered: Dec-03
I know it is older than 4 years--I thought it was more like 10 years. The current owner may have had it for 4 years . . .

I don't think anyone has made a passive sub for at least a decade--there just isn't a market for one.
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