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help wiring up old sub

Discussion in 'Home Cinema & Hi-Fi' started by Cyber-Mav, 7 Apr 2021.

  1. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    so i found this old sub in the shed and tested it with the phone using rca to phono cable and the sub does work.
    no i know i can use it like this with a pc that has sub channel out but how can i use this with a regular tv? i do have a nvidia shield tv connected to the tv so wondering if there is some way to get this hooked up so i can get bass from the sub and the rest of the sound through the tv speakers?
    sub is a philips sw 3800:

    [​IMG]
    [​IMG]
     
  2. NickK

    Capodecina

    Joined: 13 Jan 2003

    Posts: 19,071

    I suspect that it simply takes a standard audio in but better check the manuals.

    If it's a standard audio in, you could use a splitter. Not sure what the impedance is or what impact it would be on the sound but if it's a standard audio in then it's likely not to cause massive difference.
     
  3. lucid

    Soldato

    Joined: 29 May 2010

    Posts: 5,718

    Location: Cheshire

    It's not going to work without an AV preamp to manage the signal.

    The input is mono for.a start, so if you used a imple splitter the you're either losing the left or the right channel unless you put the signal through a stereo to mono convertor.

    That's not the biggest issue though. It's the relative volume of the sub versus.the TV speaker volume, and how you control the signal level when the TV volume is adjusted.

    Say you do get the signal splitting sorted. The signal level from the splitter will be at what the sub sees as close to full volume, so the sub will play loud. Now you're looking for.some way to turn the volume down, so you go to the big knob at the front.

    Okay, now you have the sub playing at a more reasonable level. You then grab the TV remote.to adjust the volume, but the sub's level doesn't change. That's because it's getting its signal before the bits of circuitry in the TV that control volume. This means every time you adjust the TV volume, you'll have to disk about with the sub's own volume control too just to balance the levels. That'll get old real fast.

    To run with that sub and no other gear would need a TV with a TV with a subwoofer out socket. That's a TV which does the mono summing and has control of the signal level, but I haven't seen a TV like that in years.
     
  4. drakulton

    Wise Guy

    Joined: 20 Apr 2015

    Posts: 1,336

    Perhaps you should watch a couple of episodes of Das Boot for some inspiration. [​IMG]
     
  5. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    Odd it works perfectly with the pc. Also whats mono input got to do with it when it's a single speaker in the box.
    Im guessing its gonna be a issue trying to integrate it into a digital audio setup that is hdmi.
    Will have to think of something that's cheap, otherwise just cheaper and easier to get new sub.
     
  6. lucid

    Soldato

    Joined: 29 May 2010

    Posts: 5,718

    Location: Cheshire

    Your PC sound output works differently to the Shield.

    For a desktop system, the sound card will have a 5.1 output. This means that the sub and centre channels come out on one of the three jack sockets. The sound is already processed and split so that the channel for the sub is mono and bass only. Its level is controlled by the O/S. You go to the tool bar, clich the speaker icon and change the level; the PC takes care then of changing all the levels in unison; the centre, the sub, the front stereo channels and the rear stereo channels. All of them change in sync together. The Shield can't do this.

    The fact that it's a single speaker in a box, with ONE connection socket, means it NEEDS a mono signal. That's the whole point.

    For a laptop or other device using just the stereo out from the headphone/line out connector, what you did was hook up a single channel to make the sub respond. If you had a soundtrack where say a tank rumbled from off screen on the left, through centre, then off to the right, you'd only get half of that with the sub wired in to just one of the two stereo channels. Say you wired to the left channel. The sub would rumble as the tank appeared, but as it got to the centre of the screen and headed to the right then the sub would be getting quieter even though the tank is still onscreen. That's because the right channel info isn't getting to the sub. It needs a sum of the left plus right in a mono signal, or you need stereo subs; one per channel.

    It's nothing to do with HDMI. This is simply the fact that you're trying to use bits of kit together that aren't meant to work in the way you want them to.

    Put the Philips sub on the back of a Yamaha sound bar with a subwoofer out socket and it will work fine and dandy. Connect it to an AV receiver with a subwoofer out socket and it'll work just fine. Connect it to the subwoofer channel of a 5.1 soundcard and it'll work. But connect it to anything with an analogue stereo fixed-level signal and you'll get exactly the problems described.

    Go ahead. Try it for yourself. Then when you're sat scratching your head why the level doesn't change with the telly remote and why some sound seems to be missing you can come back and read this thread and have a light bulb moment. "'PING!' Ohhhh..... That's what they meant" :D:D:D

    Incidentally, you'll run in to the same issues with any other sub with the same connection. The sub isn't the issue. It what you're trying to use it with.
     
  7. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    You mentioned a yamaha sound bar, do sound bars in general have sub out which can work with this sub?
    Iv never heard a sound bar most look small so i wondered if they are any better than the tv built in speakers.
    Also iv never known bass to be in stereo.
     
  8. stuman

    Wise Guy

    Joined: 27 Aug 2003

    Posts: 1,971

    Re-read the bit about the tank rumbling.
     
  9. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    but if you only got 1 sub in the room how do you get stereo bass? not like people have 2 subs left and right.
    low frequency sounds being omni directional etc.
     
  10. IanAG

    Wise Guy

    Joined: 5 Nov 2002

    Posts: 1,679

     
  11. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    That doesnt explain stereo bass. The example of the tank is talking about a stereo signal to a single sub but you cant do stereo with just a single speaker. Combined to mono is whats normally done.
    So in your tank example the tank going from left to right how would that work with a single sub? Or does someone move the sub to the other side of the room when the tank exits ?
     
  12. IanAG

    Wise Guy

    Joined: 5 Nov 2002

    Posts: 1,679

    It wasn't meant to explain stereo bass, I am not sure anyone has raised stereo bass before you have.

    Subs are mono as you say, and sub channels are mono for this reason - meaning without a dedicated sub output you would be hacking up an alternative approach to use this sub.

    Your PC has a sub channel out, as lucid stated you would need an AV preamp with a sub output to use with the Shield. If you take a single cable from a stereo output to the single mono input on the sub, you will only be getting half of the bass.
     
  13. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    ok ignore all the stereo mono stuff.

    i see the shield tv has a 3.5mm jack which i think is a output. can i use a 3.5mm jack splitter to send one cable to the tv and one to the sub then have volume on tv a max and sub volume at max then use the shield tv to control overall output volume?
    i see there is a issue where someone changes source to cable box and gets an earful lol but is that doable? i dont know if playing content from shield tv outputs over hdmi or the 3.5mm jack?
     
  14. lucid

    Soldato

    Joined: 29 May 2010

    Posts: 5,718

    Location: Cheshire

    My guess is you're only saying about bass being mono as a routine method because all you've ever experienced is PC speakers and home cinema kits with a single sub and small satellite speakers. That's the sum total of your knowledge, but there's a bigger world out there.

    Have a look at the image below. You're seeing all the equipment in the system. Nothing else if off to the sides or out of shot. Now, given the size of the speakers, do you really think that they don't produce deep rumbling bass?

    [​IMG]


    Here's an image of a different system. This time you're seeing just the front sound stage. The side and rear surround speakers are off shot, but that's less relevant. Do you notice the two subwoofers? That would be stereo subwoofers, wouldn't it? This rather explodes your idea that bass is mono as in "you only have a single subwoofer".

    [​IMG]


    A stereo hi-fi signal is typically two channels of sound with a frequency range of 20Hz to 20kHz. Most simple stereo systems with either larger stand-mounted speakers or floor-standers won't have a sub. The speakers will get the whole frequency range and play down to whatever frequency they roll off at. Roll-off means the point where the speakers volume starts to drop off at progressively lower frequencies.

    The model number of the large black speakers in the top picture is B&W 800 D3. These have a frequency range quoted as 15Hz to 28kHz +/-3dB. At 15Hz the speaker is still producing useful sound, albeit at half the volume level of an octave higher which is 30Hz. This is better than a a lot of powered subs with 8-10" drivers. By contrast, that Philips sub with its 6.5" driver doesn't have a proper specification. The service manual for it quotes a lower frequency of 30Hz, but without a roll-off dB figure then the number is meaningless.


    When it comes to movie sound tracks in domestic audio formats, be it Dolby Digital, DTS, Dolby TrueHD or DTS Master Audio, all five or more main surround channels are also a minimum of 20Hz-20kHz. This means that if you had the room and enough spare cash you could have say three pairs of the £23,000/pr B&W 800 D3 plus their matching centre speaker, and each could get full 20Hz-20kHz audio with no real need for a sub at all.

    The only part of a movie sound track that is both bass and mono is the LFE channel. LFE stands for Low Frequency Enhancement. It has its roots in the 1950-60s when the cinema industry was experimenting with wider screen formats than Academy Standard and exploring stereo and multichannel sound.

    LFE exists because there wasn't enough scope in the existing stereo soundtrack space to increase the bass level to wow audiences. Having an extra track dedicated just to deep bass, with the upper frequency pegged at 120Hz and the lower frequency of 3Hz(!!) meant that the additional volume was on tap when needed for the big explosions and other deep bass effects.

    LFE first appeared in mass market consumer audio with the arrival of Laser Disc and AC3 multichannel audio in the 90s. It was niche market stuff though. DVD and Dolby Digital processing in the late 90s changed all that. DTS followed within 18 months. Suddenly home cinema systems were a thing that people were getting in to.

    It was obvious though that expecting consumers to have floorstanding speakers all round the room was impractical. There was also an issue with amplifier power. There wasn't enough to to do 5 channels of full frequency audio. This is part of the reason why AV amps and AV receivers have bass management. It filters the main channel frequencies to split away the bass and direct it to the sub which is already handling the LFE track. This is how we arrived at the sort of sub/sat systems from which your Philips SW3800 sub came from.

    Main channel bass is not mono. It only becomes mono if the bass management in a processor splits and sums it to a single channel. LFE is the only true mono bass track.
     
  15. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    From what iv read the physics of sound is that higher frequencies are more directional than low frequencies hence why stereo bass as such doesnt work as well as higher frequency sounds do.
    Those expensive setups you shown look good but i still get the feeling they wont pump out bass like what iv heard in car audio with cars using 2x12 or 15inch subs with 1kw rms. But again i dont think stereo bass is a thing in a car since subs are so close to each other.

    What happens if a sub is placed in front of you and one behind? Are those positions superior to having both subs in front left and right?

    I just found the Philips sub in the shed so wondered it i could use it with what i have id like to get away from just using tv speakers.
     
  16. lucid

    Soldato

    Joined: 29 May 2010

    Posts: 5,718

    Location: Cheshire

    I'm not sure you really need physics to tell you what's self-evident from observation, but taking a deeper interest is rarely a bad thing. Lower frequencies are harder to localise.

    In-car versus in-home are two different things, particularly when talking about those in-car demos when some girl sits in the passenger seat and her hair goes wild with the bass. Each to their own. Bass isn't the only reason for those large B&W speakers. You'd really need to hear some large orchestras playing, then listen to recordings played through those and similar large speakers to appreciate all the things they do besides just bass.

    For a pure music system, or one heavily biased towards music, running the subs next to the main speakers helps to anchor the sound and the stereo effect. Again, you'd need to have a listen yourself to appreciate how it changes things.

    Sub position is a huge topic. Balancing multiple subs in a room is a cross between science and black art :D Just plonking two subs down, fore and aft, could well end up with an incredibly peaky response. That is when some frequencies boom out and others virtually disappear. For music and cinema use, the ultimate goal is having a flat and even bass response in as many of the listening positions as possible. That can take a huge amount of work.

    If I just wanted club-levels of bass then a couple of Bose Sound Cannons would do the trick. They're not subtle, but you feel it in your chest like the bass is trying to breathe for you. The best bass though (IMO) isn't 'in your face' all the time. It's there, underscoring everything, huge and bottomless and with the capability of ripping your clothes off should the need arise. But most of the time you're only aware that things have a much grander and effortless scale. It's very seductive, and you only really notice it by its absence when the subs are switched off.

    Your quest to use this Philips sub is your own business. You came on here asking for advice about using it with your Shield and TV setup. We gave you some advice along the lines of "it's not really practical, but here's what you'll have to do", and along the way we've uncovered and perhaps helped you fill in some of the gaps in your knowledge about bass signals.

    I'm still of the opinion that it's not a practical proposition for everyday use, particularly if there is a significant other in the house who is level tach-savvy. As a one-off experiment though it's a bit of fun and might kindle a bit of an interest in getting something better than the TV speakers. There's a wealth of used gear available in the form of soundbars and AV receivers + speakers that could allow you to play without spending too much dosh.
     
  17. Yaayuh!

    Capodecina

    Joined: 5 Nov 2010

    Posts: 21,126

    I like you @lucid

    Just props for lucid man-love. Carry on, as you were.
     
  18. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    What would you say is best value for money on the cheap side of things to get for speakers and sub?
     
  19. lucid

    Soldato

    Joined: 29 May 2010

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    Location: Cheshire

    It sort of depends on what you're aiming at, so the trick is to break your requirements in to chunks, and prioritise the "must haves" from the "would like to haves" which are the things that will stretch any budget.

    You should also be very clear about any restrictions. For example, you could have a stonking stereo system based around an Arcam Delta amp (£60-£80ish) and a decent-sized pair of stand-mount speakers (£80-£120). If I was to set these up.in your living room on some basic stands and feed them from a nice CD player your jaw would hit the floor. 3D imaging, tight bass, great rhythm and pace, totally punching above the price paid and knocking spots off any Currys-bought shelf system you've ever heard.

    But if there's no way in hell you could get 2ft tall speakers past the missus, or the system has to fit in to a small office space, then it's pointless going down that road. A sub/sat system wouldn't sound as good, but if that's what will fit in the room space then you need to be clear about it up front.

    The flip side is I old suggest a s/h set of Logitec Z5500, and whilst that'll fit in a small room and work fine as desktop monitors and handle digital optical and coaxial for DD and DTS and also give thunderous amounts of bass, maybe you've got young kids or difficult neighbours so you've always got to have the sub turned down. That would be frustrating.Maybe you have a decent amount of space and you want the big 3D sounds take effect that the Z5500 isn't up to doing.

    Maybe have a read of this recent thread: https://www.overclockers.co.uk/forums/threads/used-cheap-audio-setup.18923168/
    It starts from a slightly different place than where you're at right now, but the end destination is in the same direction you are heading.
     
  20. Cyber-Mav

    Capodecina

    Joined: 30 Jul 2005

    Posts: 15,469

    Location: Midlands

    Hmm i didn't think i would have had input from someone so clued up as you on this forum. This is the first time iv been on this music side of the forum.
    Let me get some pics for you to show what im working with.