Author Topic: subwoofer Hi vs Low level connection  (Read 306 times)

Offline jimbones

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subwoofer Hi vs Low level connection
« on: August 19, 2019, 03:49:09 PM »
Just curious how everyone connects their subs. I am connecting using low level RCA's. How are you connected??
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Offline tmazz

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Re: subwoofer Hi vs Low level connection
« Reply #1 on: August 20, 2019, 04:43:27 PM »
That's easy, I don't.

Since I got the Mac amp I simply no longer feel the need to run the subs with the Nolas.

However when I did, I ran them from the preamp level RCAs. The problem with running the subs ona speaker level input is that they sub then has to take on the "flavor" of your power amp. And that flavor may or may not blend in well with the way the speaker was voice, which I would assume was done with the sub's internal amp. Of course, as always, that idea is a good starting point, but a final decision needs to be made based on listening to the sub connected both ways to your own equipment in your own room.

The other thing that always worried me about using speaker level connections to drive a sub is that in doing so aren't you essentially putting the crossover in the sub in parallel with the crossover in your speakers.  And if the amp's output impedance is part of the crossover circuitry, can't changing that impedance by paralleling the amp with the sub change the performance characteristics of the speakers crossover?

HAL and any of our other speaker design gurus, any thoughts on this?
« Last Edit: August 20, 2019, 04:47:36 PM by tmazz »
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Offline jimbones

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Re: subwoofer Hi vs Low level connection
« Reply #2 on: August 20, 2019, 06:17:09 PM »
That's easy, I don't.

Since I got the Mac amp I simply no longer feel the need to run the subs with the Nolas.

However when I did, I ran them from the preamp level RCAs. The problem with running the subs ona speaker level input is that they sub then has to take on the "flavor" of your power amp. And that flavor may or may not blend in well with the way the speaker was voice, which I would assume was done with the sub's internal amp. Of course, as always, that idea is a good starting point, but a final decision needs to be made based on listening to the sub connected both ways to your own equipment in your own room.

The other thing that always worried me about using speaker level connections to drive a sub is that in doing so aren't you essentially putting the crossover in the sub in parallel with the crossover in your speakers.  And if the amp's output impedance is part of the crossover circuitry, can't changing that impedance by paralleling the amp with the sub change the performance characteristics of the speakers crossover?

HAL and any of our other speaker design gurus, any thoughts on this?

Yea PS Audio is sold on high level. Also I meant active sub. The crossover does not apply in this case.
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Offline HAL

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Re: subwoofer Hi vs Low level connection
« Reply #3 on: August 20, 2019, 06:17:54 PM »
I use balanced inputs on the Rythmik amps.  No problems with ground loops. I used the line level inputs before.

One technique with some sub amps with R/L RCA inputs is to use a Y to both inputs from the preamp out.  Increases signal level to the amp. 

If the amp you use has a balanced bridge output it needs to be investigated with the sub amp company.  Some have grounded negative and would likely blow the output stage of the amp. 

Offline tmazz

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Re: subwoofer Hi vs Low level connection
« Reply #4 on: August 20, 2019, 08:21:41 PM »
That's easy, I don't.

Since I got the Mac amp I simply no longer feel the need to run the subs with the Nolas.

However when I did, I ran them from the preamp level RCAs. The problem with running the subs ona speaker level input is that they sub then has to take on the "flavor" of your power amp. And that flavor may or may not blend in well with the way the speaker was voice, which I would assume was done with the sub's internal amp. Of course, as always, that idea is a good starting point, but a final decision needs to be made based on listening to the sub connected both ways to your own equipment in your own room.

The other thing that always worried me about using speaker level connections to drive a sub is that in doing so aren't you essentially putting the crossover in the sub in parallel with the crossover in your speakers.  And if the amp's output impedance is part of the crossover circuitry, can't changing that impedance by paralleling the amp with the sub change the performance characteristics of the speakers crossover?

HAL and any of our other speaker design gurus, any thoughts on this?

Yea PS Audio is sold on high level. Also I meant active sub. The crossover does not apply in this case.

It may not not have a crossover per se, but it at least has to have some kind of low pass filter to make sure only bass signals get to the sub. And that low pass filter is essentially just a crossover that dumps all of the non bass signals instead of passing them on.
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Offline Jack

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Re: subwoofer Hi vs Low level connection
« Reply #5 on: August 20, 2019, 08:28:28 PM »
Using the High Level inputs of a capable sub does not eliminate the crossover in an active sub just the routing method of the input signal.  I have a pair of Rythmik F12 subs in two different systems with one pair hooked up with each method and it changes nothing in how you set up the sub. 
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Offline jimbones

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Re: subwoofer Hi vs Low level connection
« Reply #6 on: August 21, 2019, 05:04:36 AM »
That's easy, I don't.

Since I got the Mac amp I simply no longer feel the need to run the subs with the Nolas.

However when I did, I ran them from the preamp level RCAs. The problem with running the subs ona speaker level input is that they sub then has to take on the "flavor" of your power amp. And that flavor may or may not blend in well with the way the speaker was voice, which I would assume was done with the sub's internal amp. Of course, as always, that idea is a good starting point, but a final decision needs to be made based on listening to the sub connected both ways to your own equipment in your own room.

The other thing that always worried me about using speaker level connections to drive a sub is that in doing so aren't you essentially putting the crossover in the sub in parallel with the crossover in your speakers.  And if the amp's output impedance is part of the crossover circuitry, can't changing that impedance by paralleling the amp with the sub change the performance characteristics of the speakers crossover?

HAL and any of our other speaker design gurus, any thoughts on this?

Yea PS Audio is sold on high level. Also I meant active sub. The crossover does not apply in this case.

It may not not have a crossover per se, but it at least has to have some kind of low pass filter to make sure only bass signals get to the sub. And that low pass filter is essentially just a crossover that dumps all of the non bass signals instead of passing them on.

My point is that it the crossover is active. I haven't measured yet but I presume the input impedance is fairly high on the sub amp. I don't think there and disadvantages per se. 
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Offline HAL

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Re: subwoofer Hi vs Low level connection
« Reply #7 on: August 21, 2019, 05:45:33 AM »
The other thing to think about is that the low level signal has been through less amplification stages than the speaker level.  That usually means more added noise and distortion for the high level outputs. 



 

Offline rollo

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Re: subwoofer Hi vs Low level connection
« Reply #8 on: August 21, 2019, 12:16:04 PM »
  When I used Subs with the Pipedreams I tried Mapleshades suggestion to use speaker wires from amp to sub. Sounded better to me than IC from preamp. Try both ways and listen to difference.


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« Last Edit: August 21, 2019, 12:17:46 PM by rollo »
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Offline BobM

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Re: subwoofer Hi vs Low level connection
« Reply #9 on: August 21, 2019, 03:50:24 PM »
REL suggests that you use the high level taps from the amp to the sub. They say it helps convey the "flavor" of the amp to the sub's which make them blend better with the speaker. I did this for a while with my old speakers and it worked wonderfully.

However, I need to cut off the bottom end of my Apogees to avoid the dreaded bass buzz, so I have an NHT subwoofer crossover. This fits between the preamp and the amp and allows me to cutoff the main speakers at about 80Hz. I then use RCA's from this NHT crossover to my stereo REL subs and can adjust their phase and signal strength and top end cutoff frequency and a few other things to dial them in perfectly.
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Offline jimbones

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Re: subwoofer Hi vs Low level connection
« Reply #10 on: August 24, 2019, 07:20:23 PM »
OK so today I had some time to try the high level input. What an improvement. Before had a lack of bass impact. However, the Wells Audio amp has a strong low end and it really helped using it to drive the sub amp. It made improvement in space, low end of acoustic guitar and even voices sound richer. Yay!!
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