Sub hook up - speaker level or line level ?

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nodiak

Sub hook up - speaker level or line level ?
« on: 13 Jan 2007, 08:00 pm »
Currently I'm using speaker level, but am going to get a sub cable and see how line level goes with my gear. Using Rythmik servo sub. Interested in experiences and comments of others with your subs.
One reason I ask is because I've heard going speaker level brings the sonic flavor of the main amp to the subs, for better or worse imo. I use a tube integrated amp and the bass is a bit soft so Ill see if response changes with line level. Any experience/comments on this?
I have a 12' run from amp to sub. Using 10 gauge Blue Jeans speaker cables. Am getting Blue Jeans sub cable.
Thanks, Don

http://www.rythmikaudio.com/servo_product.htm  I have kit option #1.
http://www.bluejeanscable.com/store/subwoofer/index.htm
« Last Edit: 13 Jan 2007, 08:48 pm by nodiak »

Salis Audio

Re: Sub hook up - speaker level or line level ?
« Reply #1 on: 13 Jan 2007, 08:26 pm »
Usually the bennifit is to have a crossover, a good one, before the amplifier so that the speakers are crossed up and sub down. However I bet the bass would be slightly soft with a tube amplifier using speaker level in. You can turn the gain up some but it will be mismatched with the speakers because they dive off huh?

Do you have a pre-amp with sub out or something?

nodiak

Re: Sub hook up - speaker level or line level ?
« Reply #2 on: 13 Jan 2007, 08:52 pm »
DOS, Rythmik is a powered sub. It has choice of speaker level or line level hook up, which is great. Haven't tried line level yet but will have cable in a week or so. I'm curious to find out if it changes the sonics.
No problem with xo and level matching, easy to blend Rythmik with mains. A great sub for me and my room.
Don

avahifi

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Re: Sub hook up - speaker level or line level ?
« Reply #3 on: 13 Jan 2007, 11:08 pm »
All things being nearly equal, use the line level inputs instead of speaker level for your subwoofer.  There is no point adding whatever distortion exists in your main power amplifier's bass performance to the signal into the subwoofer.  One amp will almost always be better than two amps' signals in series.

The only contradiction would be if the driving preamp is vacuum tube with a high output impedance trying to drive a long set of interconnect cables to the subwoofer.  That could possibly load down the preamp and affect the overall system performance.

Frank Van Alstine

nodiak

Re: Sub hook up - speaker level or line level ?
« Reply #4 on: 14 Jan 2007, 01:02 am »
Thank you Frank! That's what I needed to know.
This is my first time using a powered sub so I have things to learn. I'll get a long cable for the sub asap, anxious to hear the difference.
Don

bacobits1

Re: Sub hook up - speaker level or line level ?
« Reply #5 on: 14 Jan 2007, 07:21 pm »
Don,
I would be interested in the difference too. I know you have been in the past on the Decware board where this was discussed too. Steve recommends using the speaker connections. I have been using the speaker level connections for 3 years now. The reasoning to keep the Sub better separated from the main speakers using the Sub crossover. I have never had an interconnect cable long enough to try the other way although my Pre does have 2 outputs to facilitate a Sub. I am getting damn good results through the speaker connections.

Let us know what you think. I'm using a HSU VTF3 /MKII Sub.

Den

lcrim

Re: Sub hook up - speaker level or line level ?
« Reply #6 on: 14 Jan 2007, 07:51 pm »
I have been using the speaker level inputs w/ my Adire Rava and Omega Compact Hemps being driven by a Roger Modjeski 13EM7 SET amp (when I bother to turn the sub on.)  This is mostly because it keeps the sub and speakers in phase.  My Eastern Electric Minimax preamp inverts absolute phase.
I too worried about changing the impedance that the amp sees by driving the sub off the speaker level inputs.  Steve Deckert told me that the amount of current required to trigger the plate amp in the sub is very, very low and ordinarily should not be an issue.
I expect that someone will chime in with using a crossover to be certain that the sub only sees frequencies its good at reproducing.  I think you can find these cheaply in varying frequencies but I can't remember where.

nodiak

Re: Sub hook up - speaker level or line level ?
« Reply #7 on: 14 Jan 2007, 07:54 pm »
Den, I'm getting softer bass than I would expect from the sub via speaker level. Gotta be the tube integrated. Also from searching I just discovered my Scott 222c has a 12db @ 20 hz filter in the preamp section! Not OK! I'll go line level in about a week when cable arrives. I like enough synth/etc bottom octave response so the Scott is under scrutiny with it's filter.
Hoping to get the tube sonics out of the sub. Need a 10' or 15' cable, depending on which side of room it's placed. Next to either one of the mains it's location is undetected. 15' distance is best for non audio reasons, will go 10' if that difference matters.
Don

doorman

Re: Sub hook up - speaker level or line level ?
« Reply #8 on: 14 Jan 2007, 08:42 pm »
Is it ok to run a (powered) sub from the speaker terminals of a tripath based amp to the speaker terminals of the plate amp?
                                                                                 Don

nodiak

Re: Sub hook up - speaker level or line level ?
« Reply #9 on: 14 Jan 2007, 09:27 pm »
What amp? Designer would know for sure. Might be a diyaudio question.

doorman

Re: Sub hook up - speaker level or line level ?
« Reply #10 on: 14 Jan 2007, 11:19 pm »
The amp is a "cheapie" from PE.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-784
 Your right, maybe
 I'll contact them!
                                                                              Don

nodiak

Re: Sub hook up - speaker level or line level ?
« Reply #11 on: 15 Jan 2007, 12:47 am »
doorman, I'm just learning, but your sub amp is made for either apparently. I was saying you might want to check with the t amp designers.
Don
« Last Edit: 15 Jan 2007, 04:15 am by nodiak »

srb

Re: Sub hook up - speaker level or line level ?
« Reply #12 on: 15 Jan 2007, 12:59 am »
I believe most implementations of the T-amp have floating negative speaker connections which are not connected to each other, or to ground.

Connecting these to a typical common ground plate amp would result in shorting out the t-amp.

Rhhm

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Re: Sub hook up - speaker level or line level ?
« Reply #13 on: 15 Jan 2007, 02:55 am »
I'm using line level inputs to my Velodyne sub, and I am very happy with the results.  However, I am not using the subs crossover for the full fequency range.

I have hard-wired two 0.022uF V-Cap TFTFs into the inputs of my power amp (GTA SE40 with an input impedance of 100k ohms) to act as a high-pass filters around 75hz (I understand Sonicap Platinums would also be excellent choices for less money, but DO get good caps since they are going directly into the line).  You could also install the caps at the input end of your IC cable.  However, I have heard that if you lower the high-pass frequency so that you are using more of the full range that your speakers can comfortably handle, you will get better much better and seamless sound between the main speakers and the sub.  If, for example, I change the caps to 0.047 uF, my high- pass will be about 35hz.  You can easily calculate your high-pass frequency using the following site:

http://www.carstereo.com/help2/Articles.cfm?id=1

Once you decide on where you want the high-pass frequency, you just set the crossover on the sub to roughly the same frequency.  What you are doing is keeping the full range signal out of the questionable crossover electronics that exist in many subwoofers.  The difference in sound between using my sub's crossover for the full range from using a high-pass filter into my amp (GTA SE40) is startling - better everything!   aa

Obviously, by using this kind of a high-pass filter at the input of the amp, you can't use the speaker outputs of the amp into the sub because the amp is now only handling the frequencies above your high-pass point.


tanchiro58

Re: Sub hook up - speaker level or line level ?
« Reply #14 on: 15 Jan 2007, 05:49 am »
Hi Nodiak,

I agree with Frank and Don. You should have a tube preamp with a second pair output so you can connect to low level inputs of the subwoofer (I use Hsu VTF2 MKII) via a pair of ICs. But in this case I hook it up to a Promitheus Audio TVC passive preamp since my parallel 2A3 SET amp has only 8 watts output. I got a pretty musical deep bass with little hang over (will be fixed) blended well with my custom built vintage speakers over 97dB JBL D131.

nodiak

Re: Sub hook up - speaker level or line level ?
« Reply #15 on: 15 Jan 2007, 06:48 am »
tanchiro58, the Scott 222c integrated I'm using for mains has been an experiment and learning point. i want to stick with it for at least a couple months and use it as a basis for letting me know what else i want, if anything. i had tried gainclone and tested some tube pre's with it. I like that combo and may go back to it, but improving gc and looking for a tube pre mate some more. I basically wanted to rest from searching for awhile, so the Scott - as it has phono, headphone, tone and balance controls.
Sorry to be long winded here just giving perspective on what I'm up to.
As for sub hookup, I'm now pretty much convinced that line level will take the Scotts soft bass out of the equation. Fortunately the Scott 222c has a center channel out that I'm told works well as a line level out to a monosub, like I'm using. So I should know soon. A possible problem is the Scott seems to have a 12db filter at 20 hz, and I'm after getting the full glory of this Rythmik subs 14 hz f3. If the Scott can't do that then I think that will be a deal breaker, and the search for a pre/amp begins again, but slower paced this time.
Don

nodiak

Re: Sub hook up - speaker level or line level ?
« Reply #16 on: 24 Jan 2007, 09:16 pm »
Got the sub cable and have gone line level from Scott 222c center channel to R input of sub.
Works much better. Kept subs level, xo frequency, phase the same. Softness is gone and bass is tight and clean, and at least as deep. Speaker level the sub sounded heavier and softer than the mains alone. Now when the sub is turned on the crisp bass is maintained. This sub system is very nice.
Don