# An inexpensive way to boost the subwoofer level



## thewire (Jun 28, 2007)

I have amplifiers for my subwoofers with no volume level control. My source is -15dB low from my DVD player making it very difficult to get the proper amount of bass from the subwoofers. This also makes it challenging to measure, but not impossible. I would like to know if by adding an RCA line level control such as the one in the link bellow will allow to me fix the level issues I'm having. The manufactor does not spec the +- of the response or frequency range. They claim that it is a High fidelity device and works for a subwoofer. I would like your opinion on if this is a good deal. I would like to use a power supply similar to or if not the same as the one pictured bellow and to attach it to the board. Will this work well, do I insert this after the BFD or before? Would I be better to spend more on some kind of a used preamplifier or a used Outlaw ICBM? I'm not sure I could afford the ICBM right now. I'm looking to keep it under $100.00. I also have subwoofer amps with line level controls on them (that have some problems and not certain where at) but I'm not sure how to use them to make one. If anyone wants to help me make one from those I can provide pics.

http://www.hometech.com/hts/products/audio/volume/at-litamp.html


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## brucek (Apr 11, 2006)

The product you show (since it appears to use a pair of KA-386 op amps) is a small ~300 mwatt power amplifier, which would be useful to drive a set of headphones (@8ohms).

This would not be a suitable choice, as you require a voltage amplifier (not power) to increase your line level.

I'm confused that a consumer based DVD player would output a line level that was -15dB low. Typical max output +2dBV (~1.25vRMS) consumer line level is fixed from a player. This generally feeds a preamplifier which does little other than reduce the signal through a volume control to allow proper input level to a power amp. How have you determined that your max output level is -15dB to become ~200mvolts?

brucek


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## thewire (Jun 28, 2007)

The analog signal output of the XA2 I have read is 15dB low according to people that own it. When I input the signal of the XA2 subwoofer output into my soundcard and measure the output, the signal reads lower than when the bass management is disabled. If I plug in a different DVD player the level output of the subwoofer is much higher, but I loose the ability to adjust other channel levels. If I used the other DVD player, a Malata n996, the output is normal. When I switch the crossover on my XA2 DVD player from small settings to large, the subwoofer output is increased +5dB but the bass from my other speakers sounds kind of compressed and the level of the subwoofer seems very high. When I setup my system to reference level or -10dB lower, then go to measure in REW, it reads 10dB higher. I have four subwoofers however and by adding each of these I noted a signficant gain, espicially as now the way I have it with all four co-located near the center front wall. The level I get 85dB in REW is a volume level of 3 but I think I accedently had a subwoofer off and it would have been 88dB which is what I had measured before.

I'm looking for any kind of a level control and if there are other features such as a limiter etc thats good too. If I should leave as is also let me know. I will see what kind of peak SPL I am getting or what my subwoofers measure at on a disk. The last time I checked they were 71dB -20dB FS. I canno't lower the other channels that are a minimum 75dB -20dB FS.


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## thewire (Jun 28, 2007)

The 3 setting was with a -18db FS sweep level.


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## brucek (Apr 11, 2006)

> The analog signal output of the XA2 I have read is 15dB low according to people that own it.


A quick look at the spec sheet says the output level is a respectable 2.0V RMS. This is sufficient to drive any amplifier to full output. I'd look for the problem you're having somewhere else other than the fixed output level of your DVD player.

brucek


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## thewire (Jun 28, 2007)

It seems the level is now 76dB since I have done some furthur room treatments. I guess I will be fine then for a lower reference level then. The other speakers now also measure 75dB 76dB before adjustments. Thank you for your input bruce.


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## Andysu (May 8, 2008)

thewire said:


> I have amplifiers for my subwoofers with no volume level control. My source is -15dB low from my DVD player making it very difficult to get the proper amount of bass from the subwoofers. This also makes it challenging to measure, but not impossible. I would like to know if by adding an RCA line level control such as the one in the link bellow will allow to me fix the level issues I'm having. The manufactor does not spec the +- of the response or frequency range. They claim that it is a High fidelity device and works for a subwoofer. I would like your opinion on if this is a good deal. I would like to use a power supply similar to or if not the same as the one pictured bellow and to attach it to the board. Will this work well, do I insert this after the BFD or before? Would I be better to spend more on some kind of a used preamplifier or a used Outlaw ICBM? I'm not sure I could afford the ICBM right now. I'm looking to keep it under $100.00. I also have subwoofer amps with line level controls on them (that have some problems and not certain where at) but I'm not sure how to use them to make one. If anyone wants to help me make one from those I can provide pics.
> 
> http://www.hometech.com/hts/products/audio/volume/at-litamp.html



Easy stick a simple audio mixer in line between the subwoofer output and into one of the line inputs on the audio mixer and then use the output from the mixer to vary the level. I use one myself expect my set-up is not like yours.

The alterative would be the DCX2496 with all outputs been sent to the DCX and there are multiple choices of customizing the set-up without the hassles and worries of possible speaker damage.


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## thewire (Jun 28, 2007)

I have been using my pre/pro to adjust the gain on my subs. Now with the pre/pro handling my crossover duty the subwoofer output from the DVD player is at 0dB instead of -5dB, so I have not had reason to boost the level since doing that. It's lower than the mains the way I have it set in the pre/pro. It seems that everyone worried about damaging their speakers hears some kind of distortion. If I don't hear that should I still be concerned about protecting the speakers if I am already familiar with the required output of the movie title, or if I am just keeping the gain where it has been? I have watched some of the Matrix movies plenty of times with the 115dB peaks going on/off dozens of times a minute and never thought I was worried about the speakers being damaged. 

I always take my SPL meter and measure the start of a movie or I listen to see how loud the quiet sounds are comparred to the loud sounds before I even think about going anywhere from a -10 reference setting (if I expect lots of bass) the standard -4 reference starting point, 0 reference normal listening level, or higher if I am just testing something that I am familiar with. It's my hearing I am more concerned about.


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## Andysu (May 8, 2008)

thewire said:


> I have been using my pre/pro to adjust the gain on my subs. Now with the pre/pro handling my crossover duty the subwoofer output from the DVD player is at 0dB instead of -5dB, so I have not had reason to boost the level since doing that. It's lower than the mains the way I have it set in the pre/pro. It seems that everyone worried about damaging their speakers hears some kind of distortion. If I don't hear that should I still be concerned about protecting the speakers if I am already familiar with the required output of the movie title, or if I am just keeping the gain where it has been? I have watched some of *the Matrix *movies plenty of times with the 115dB peaks going on/off dozens of times a minute and never thought I was worried about the speakers being damaged.
> 
> I always take my SPL meter and measure the start of a movie or I listen to see how loud the quiet sounds are comparred to the loud sounds before I even think about going anywhere from a -10 reference setting (if I expect lots of bass) the standard -4 reference starting point, 0 reference normal listening level, or higher if I am just testing something that I am familiar with. It's my hearing I am more concerned about.



If you what to a listening challenge right here right now. Plug into The Matrix 1999 chapter 4 listen to chapter 4 on repeat mode! After listening for the first scene in chapter, disconnect the fronts and surrounds and listen to chapter 4 again, it’s like an Easter egg surprise.

Yes I’m into listening to the whole soundtrack.

The DCX2496 is my PAL my friend, :yay2: without it would be less entertaining.:gah:










You’ll hear Foley footsteps a cigarette lighter a hand on leather…next to impossible unless you have some tools to go deeper into The Matrix.



















You’ll hear Trinity’s footsteps getting nearer to Neo.


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## thewire (Jun 28, 2007)

When I first tried that scene in my theater all I could hear was the bass in the music and it was very loud and the notes would press against my ears with the voices difficult to hear over the music. I hear all those details yes. I also hear what might be some reflection off the wall next to Neo as he talking for a moment, some music that sounds like it is from the doorway, some ladies laughing, a man saying something. I am unable to watch it on the screen at the moment, only listen. My XA2 has not output a composite signal since I upgraded the firmware so I can't watch on a regular TV with that unless I use a different player but it woln't play my Matrix movie that is HD-DVD.

When I turn off the mains I hear some noise like some small ice cubes rolling around inside a cup from the drive-in at the restuarant. Those sounds (higher in frequency) are probobly over 10dB lower than the sounds from the mains, so I never hear them. The voices sound like they are from the center channel speaker up front.

Edit: Also I could not figure out the memorization to get to repeat mode on my player without looking at the screen.


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## Andysu (May 8, 2008)

Eveing 

About 10db to 15db is about right, depending on the room or other? DCX I’m taking a different approach with experimentation at the moment since the last few nights, options seam limitless until I run out of ideas to try that is.

It’s hush, hush, for the moment until I can get the other idea to work.


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## thewire (Jun 28, 2007)

Andysu said:


> Eveing
> 
> About 10db to 15db is about right, depending on the room or other? DCX I’m taking a different approach with experimentation at the moment since the last few nights, options seam limitless until I run out of ideas to try that is.
> 
> It’s hush, hush, for the moment until I can get the other idea to work.


I remember running out of ideas in my first HT very well. I had tried everything there was to do with speaker placement etc. I learned way to much from that and spent more time researching than actually doing anything to the room. :scratch: If I had as many devices to play with as you have in your HT my head would be spinning. :dizzy:


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