1. OCAU Merchandise is available! Check out our 20th Anniversary Mugs, Classic Logo Shirts and much more! Discussion in this thread.
    Dismiss Notice

Subwoofer not very loud

Discussion in 'Audio Visual' started by neRok, Dec 16, 2021.

  1. neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    I've got an old 12" car sub in a sealed box, and I have just tried hooking it up to an amp, but it's not very loud.

    I've connected it to the amp correctly (bridged it as per the instructions, and connected LFE RCA to correct input), and the amp is meant to do 130W into 8 ohms. The subwoofer is 12", 300W RMS, 2x 4 ohm coils I wired in series for 8 ohm, and 88.1dB sensitivity.

    If I have the sub amp on like 80% volume, it's making bass, but the little yamaha I was using before with its 8" ported woofer and 75W RMS is louder at only 30% volume. Any idea what the problem could be? Maybe just too insensitive at too low power?

    If I didn't wire the coils up in series but did parallel instead (I did this part weeks ago, maybe I had a brain fart) that would be a 2 ohm load, and would that have just caused the amp to blow? I will consider pulling the speaker out if there are no other options, but don't want to right now, it's old wood and who knows how much life the holes have left in them.
    Edit: Don't think it's that, as I just hooked up the multimeter and it flickers between 7 and 8 ohms, as expected.
     
    Last edited: Dec 16, 2021
  2. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    Yer, I think it just takes a lot of power to get humming. I've now hooked it up to a bigger plate amp that does 240W into 8 ohm, and it's pretty good at 40%. It does pull nearly 3x the power from the wall though (vs the yamaha).

    It needs a bigger box, and I wonder if that will help?
     
  3. Stooge007

    Stooge007 Member

    Joined:
    Aug 22, 2006
    Messages:
    12,070
    Location:
    The Shire, Sydney
    are you sure it's wired up in phase to the rest of your speakers?

    does the plate amp have a 180* phase switch to test? if not, try switching the positive and negative speaker terminals and see if that makes a difference

    box size and also whether it should be ported or sealed ultimately depends on the Thiele Small parameters, do you happen to have them?

    is the current box just a pre-fab 1 cubic foot sealed enclosure?
     
  4. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    I tried switching the terminals with the smaller amp and it didn't seem any different.

    And the plate amp does have a 180 phase switch, but it doesn't make much of a difference.

    The other speakers are bookshelfs with HPF enabled in the receiver, so they shouldn't be conflicting (it certainly sounds very flat with no sub).

    And yer prefab, and I just measured it up, ~27L, so yer 1 cubic foot.

    Code:
    Thiele-Small Parameters
    Fs(Hz)       28.8
    Vas(l)       79.5
    Qts       0.392
    Qms       3.2
    Qes       0.446
    Bl(Tm)       10
    Mms(gr)       145
    Cms(mm/N)   0.211
    Rms(kg/s)   8.09
    Le(mH)       0
    Re(Ohm)       1.7
    Sd(sq.mm)   51472
    Vd(l)       0
    X-max(mm)   0
    X-mech(mm)   0
    
    General Parameters
    Diameter (inch)       12
    Max Power(W.)       600
    RMS Power(W.)       300
    Number of Coils    2
    Impedance Z-Nom(Ohm)   4
    Reference efficiency η0(%)   0.41
    Sensitivity(dB) 1-W       88.1
    Sensitivity(dB) 2.8-V       94.9
    
     
    Last edited: Dec 17, 2021
  5. mtma

    mtma Member

    Joined:
    Aug 12, 2009
    Messages:
    6,180
    What are you using to evaluate the sub output? What's your crossover point? Is the x-max not advertised or did you just not fill in that data to the table?

    Bandpass subs have particularly high efficiency right where they are tuned, sealed subs have comparatively low efficiency however are more versatile through a wider range. Also the output of a sealed sub is directly limited by the x-max of the driver unit. Which is why HT sealed setups often end up with some twin 15's or more, though these will also fullfill the sub-bass like nobody's business.

    Maybe, if where it's lacking is in the rolloff region of the current box. A larger box will free up some more output down low (at the expense of the peaking output around the rolloff)

    It won't free up any output where the sub is currently theoretically flat according to the T-S parameters. That's down to the driver.
     
    Last edited: Dec 17, 2021
  6. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    My ears. This is hooked up to my PC, gets used for music and games (and both at the same time).

    Whatever the receiver does. The manual doesn't have any values. [Edit: found it, says 90Hz]. I'm currently using the single LFE output. Maybe I will try a full stereo output, because...
    The plate amp (old jaycar AA0508) additionally has a variable crossover from 20 to 160Hz, and I've settled on 50Hz. It also has a 6dB bass boost at 35Hz, which has probably influenced my 50Hz selection (to reduce the boosted frequencies over 50Hz back to normal).

    BTW I don't know if one of the RCA input pairs is unfiltered for LFE input. Looking at this circuit diagram, which I am no expert in reading, it looks like it just merges the 2 inputs (signals go through R15 and R16 and join before C13), so that's a no. So maybe I should try the 2 RCA input with the plate amp (the small amp I used previously only needed 1 input as per the manual, so I used the LFE).

    jaycar AA0508 1 of 3.png

    It's an old Jaycar CS2279. That info is just a copy-paste of some website I found in the past, must have been this one. I haven't found any more data. Even an old catalogue PDF I found has the same info as that website.

    Anyway, I've been using the sub for the last 2 days and it sounds better - it just needs so much power. It's at about 45% on the dial of the plate amp, which makes it better than the little yamaha. Over 50% it starts to sound a bit too speaker like (if that makes sense). I listen to metal which is a bit different in its bass delivery vs music with doof doof, and this might be a factor. The little yamaha might be better at lower volumes (more impactful), but it doesn't keep up at moderate to loud.

    Edit: Just used phone app sound meter and a tone generator website, got the following results, which seem decent (consistent enough) apart from the big dip around 60Hz.

    Hz dB
    40 50
    50 54
    60 47
    70 67
    80 66
    90 69
    100 63
    110 60
    120 62
    130 64
    140 68
    150 69
    160 62

    Edit2: Also tested some random frequencies above 400Hz, and the bookshelfs are doing anywhere from high-40 to 70dB's. So, this room isn't very good, but the sub is in the ballpark. Maybe it's even a smidge loud, lol, because I'm guessing if the room was better and treated, those frequencies making high 60dB's and above should really be down in the 50 range.

    Edit3: 2xRCA is no-go because my receiver doesn't have any RCA outputs when using digital input, and I don't have any splitters for the LFE. Perhaps it doesn't matter anyway, based upon that wiring diagram? And I noticed whilst testing the 2xRCA that the bookshelfs are still making some bass. It is audible at 80Hz but quiet (like 30dB), and barely audible at 70Hz, so it's not a very aggressive crossover in the receiver. Edit: Found in the manual, it sends 90Hz and below to LFE.

    Edit4: Oh man, there's so much to this. I tested at 110Hz and 60dB, flicked the phase switch, got like 66dB lol. But actually I flicked the switch to 180 yesterday arvo, so now its back to 0 where it was originally. And then I tested the 70Hz and below freqencies, and yer they were all in the 50dB range vs 60dB range for the rest of the spectrum, so I raised the volume to like 60% and lowered the crossover to 40Hz. CBF doing any more right now as I'm going out later and want to play some games first, so I will test it like this for now.
     
    Last edited: Dec 18, 2021
  7. mtma

    mtma Member

    Joined:
    Aug 12, 2009
    Messages:
    6,180
    Test phase first right on the crossover point (90Hz), this is where the speakers are interacting the most.

    If you're combining plate amp and receiver the situation is a bit different because the crossovers may not quite match in the same location. If for example you have a 12dB/oct on one side and 18dB/oct on the other side the frequencies where you should cross them will be theoretically split out from one another.

    The plate amp RCA lineouts also seem to be high-passed, so maybe you could try feeding that into the receiver (with the receiver in full range mains).

    Single big dips and humps will be room modes or drivers fighting one another for phase. You can check out a room mode calculator and you're bound to find those all over place pretty close to where they're predicted to be. For the time being ignore stuff mid frequencies and above, that's not the problem of the sub's.

    Regarding using a phone to look at sub readings, it's typical that they won't really record levels in the bass region well, most likely the sensitivity cut-off will begin somewhere in the 50-100Hz region. So if you use a level reading from a phone to check and match levels you have to keep the frequency up.

    I would probably first set the levels to match for the mains and subs nearfield (10cm away from the drivers at a frequency where you're expecting it to be flat, but try not to be on a room mode), note the sub level setting, then move to setup listening position levels from there. From there, it just depends on what your goal is as to where to head for the next change.

    By the way if you find that the crossover settings from all the hardware is still a limitation and have a multichannel soundcard, you can mess around with everything with Equaliser APO which will let you adjust everything with DSP precision of control.
     
    Last edited: Dec 18, 2021
  8. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    Yer I might give that a crack. It will mean using the PC's DAC which is often worse, but the PC is new, whilst the receiver is probably pushing 15 years old, so it might not be that good anyway?

    I was thinking about EqAPO too. Will an onboard soundcard have enough capability? I do have an old soundcard, but its also pushing 15 years old. I was originally thinking of doing the sub out from the PC, and still digital to the receiver, but I imagine there would be audio-delay problems in this case? Maybe EqAPO can handle that?
     
  9. mtma

    mtma Member

    Joined:
    Aug 12, 2009
    Messages:
    6,180
    EqAPO doesn't really care about what sound card you're using, if it's working with a WDM driver it should work with it. The CPU does the work.

    EqAPO won't let you do multi card routing and stuff. Generally yeah you don't want to do that due to delay issues, particularly if you're crossovering the phase delays involved are tight compared to buffer lag - also you can get funky issues with unsynchronised audio clocks that you wouldn't normally notice.

    As for age, I wouldn't really count that as a downer, if it's good it will keep being good, it might just not be cutting edge or FOTM. My Onkyo SE-200PCI is probably about that age now, definitely the problems are drivers and the PCI part, audio wise it's still the same card.
     
  10. Audionut

    Audionut Member

    Joined:
    Mar 7, 2006
    Messages:
    1,540
    Location:
    4610
    EAPO will use the CPU for processing.

    That. Won't. Work.

    If you somehow manage to get the signal from two outputs simultaneously, you won't get sync. Each audio device has it's own clock rate, and they vary.

    --------

    You can't compare one system to another in the manner in which you are. Each sub has different sensitivities, their amplifiers have different input sensitivities, etc, etc.

    ---------

    You should only ever have one crossover. A crossover introduces delay and impacts phase. The receiver should be matching the sub and the mains. Adding the additional crossover from the plate amp is doing more harm then good. I would set the plate amp at the highest frequency available to minimise it's impact.

    The wrong way to skin the cat. This is creating a null in between the sub (50hz xover + 90hz xover) and the mains (90hz xover).

    I would turn the plate amp xover to the highest frequency as mentioned previously, and use EAPO to EQ the bass boost. Ideally, if possible, you would disable the bass boost from the plate amp. EQ also effects delay and phase. EQ at 50hz and then other EQ to correct the first 50hz EQ is ugly.

    Waste of time. The phone app uses A-weighting which is useless at low frequencies, and the inbuilt microphone has it's own roll-off at low frequencies. You're only going to chase your own tail.

    Use a proper mic (comes with measurement data of the mic response) and proper software.
     
    Last edited: Dec 20, 2021
    modernshoggoth likes this.
  11. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    Good info, thanks. I need to get a UMIK microphone, it's been on my todo list for a while, also for my main stereo.

    And the soundcard is out, I just checked and its PCI, whilst my mobo is X570 and doesn't have a slot.
     
  12. Audionut

    Audionut Member

    Joined:
    Mar 7, 2006
    Messages:
    1,540
    Location:
    4610
    If you have any sort of interest in that thing, it's well worth the money. REW is free which is a bonus.
     
    JSmithDTV and neRok like this.
  13. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    I'm back onto this. You might have seen my recent thread where I ordered and returned a calibration mic? Well I have ordered a UMIK-1 now, so it should arrive in the near future, and then I can get stuck into that side of things.

    But actually, I spent a lot of the weekend reading into the various options for putting together a complementary system, with regards to where filtering is happening (DSP on PC, DSP in signal chain, DSP in smart digital active speaker, and/or analogue crossover circuits), where the DAC is happening (a device, or in digital active speaker), where the amplification is happening (amp vs active speaker - analogue or digital), and what is being amplified (the speaker as a unit, or each driver individually). I am very intrigued by the concept of doing everything digitally, and then driving each driver individually, without crossover circuits. But that is for another discussion.

    To improve my PC sound system in the short term, I have ordered a Topping DX3 Pro+ DAC that is also a preamp (so has volume nob) and a decent headphone amp (handy). This means I will have 2 output (L+R), and no LFE for the sub, so crossover points cannot be controller by EqAPO (only fine tuning). The speaker amp I will be using (Emotiva UPA-2), and the sub amp I mentioned previously (old Jaycar plate amp), both have RCA pass-through. However, the Emotiva is presumably full signal pass through, whereas the plate amp does appear to have a high pass filter, which might be a win. Therefore I am wondering if DAC -> Jaycar Sub Amp -> Emotiva Speaker Amp is the way to go. And to decide this, I have been trying to suss out what the Jaycar amps circuitry actually does.

    I don't really understand what circuit components do, but I just did some reading on filters and the calcs for them, and I can follow a lot of the layout, so I think I am half way there. Here is what I have worked out so far;

    amp-id.png

    So it seems the RCA pass-through signal;
    1. comes in on the left
    2. goes through a low pass filter for safety (brown area, and which I calc'd at 338kHz, but I bet the schematic is wrong and its meant to be be 33.8kHz)
    3. goes through a 2nd order high pass filter at 138Hz (light blue area)
    4. goes through another high pass filter (dark blue area), 1st order. The capacitor is labelled 4.7/50, which I don't know what that means? Is it variable? Actually, as I write this, I wonder if it is divide, which gives 94pF, which makes it a 36.0kHz high pass filter? Shouldn't it be a low pass filter then, for safety?!
    5. goes out at the top right
    So, it seems to have a 2nd order high pass filter at 138Hz...? Except I don't know what the orange resistors are in step #2? But they affect both the exported signal, and the one use internally, so probably not important?

    Now for the actual sub signal. The amp has the following features I need to ID;
    • On the amp itself is the power switch (on/auto/off), and the phase switch. I think I have found both of those circuits, in the pink area (maybe the on/off area also has other stuff in it though?).
    • Somewhere in the amp is a 6dB bass boost at 35Hz. I haven't looked into what layout of components is able to do this, so I have no idea where/what it will look like.
    • The amp also has a "breakout board" with volume nob (min-max) and frequency nob (40-170Hz). Going to it are 2 black wires, 1 white, 1 red, 1 green, and 1 grey "wire" that seems to have a white and black wire in it.
    But for what I have worked out so far, the signal path is;
    1. same
    2. same
    3. signals merge to mono in green area, but what is the purpose of the resistors?
    4. goes through a 2nd order high pass filter at 27Hz (purple area). I guess this is also a safety filter (helps prevent extreme excursion).
    5. Signal splits out to;
      1. Phase switch area (top pink). Is this then the main signal off this page?
      2. Blue-Grey area which is unknown (has a diode?), and then the bottom pink area which contains the "power" switch. Is this all just auxiliary stuff?
    I've got the other 2 pages on different PC, haven't had time to retrieve and review them yet, and to see where all those circuits at the bottom right lead to. But am I on the right track so far?

    And one more thing that has me scratching my head. The breakout board has IR receiver, and the remote (which I don't have) has Up/Down buttons for the same Volume and Frequency. How would this work? Are the knobs actually little motors that can turn themself to match the inputs from the remote? Because otherwise, which would have priority?! Here's a picture I found of the front of the breakout board. Does it give any indication to the question of "can the knobs turn themself?"

    20210910_122557.jpg.64dc162998e26863f263d30a1149f2c0.jpg
     
    Last edited: Jun 14, 2022
  14. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    Did a bit more research late last night.
    • Found a post confirming the purple high pass filter.
    • Found some generic info on merging 2 channels to mono, and you "must" use resistors to do so, which confirms the purpose of the green area.
    • Checked the circuit for the breakout board (detailed below), which confirms the blue-grey and on/off pink area are not on the main signal path (unless they interact in the amp circuit, haven't checked).
    So on the breakout board I can see the variable low pass filter, and the volume adjustment. And I think it has motors like I guessed. I'm not sure how the knob/remote circuitry actually adjusts the filter or volume though?

    bb id.jpg

    The question remains, where is the bass boost? I read a little on bass boost circuits (need to confirm), and it said the combination of parallel capacitor and resistor between the op-amp (triangles) output and neg terminal are responsible for boost. My thoughts are;
    1. In the variable volume section on the breakout board, C3 and R6 could be boosting. However, I'm not sure of the purpose of R3 and R4 in this area. Need to confirm.
    2. In the brown section on the main board (looking at the top one), C6 and R12 could be boosting. This area similarly has the unknown R10 (orange)
      • And also, the link I shared yesterday about active low pass filter suggested that C6 would interact with R8 for the frequency spec, but the info I read on boosting suggested it was C6 and R12. So, I'm not sure which is correct right now.
      • May also need to physcially confirm the equipment values in this area.
    I need to confirm the signal path in the amp circuit, but I imagine it is "clean" (unaltered).

    So besides the boost question, the only other question is the dark blue area, if that is actually correct. I will need to (*attempt to) read the actual board to confirm.
     
  15. l_ QuadX_l

    l_ QuadX_l Member

    Joined:
    Jan 11, 2016
    Messages:
    360
    Location:
    48°04'01.8"N 12°51'49.9"E
    [​IMG]
    Sounds like you need a new woofer in your car, mate.
     
    modernshoggoth and JSmithDTV like this.
  16. Audionut

    Audionut Member

    Joined:
    Mar 7, 2006
    Messages:
    1,540
    Location:
    4610
    7.1 sound card. You can use the L+R to drive the woofers, SL+SR to drive midrange, RL+RR to drive the tweeters. Then you just need the amplification, but in the short term (since you seemingly already have 2 channels of amplification), this would have driven 2 speakers with a proper LFE out, rather than whatever the fuck you're looking to do.

    Then when you get the other 2-4 channels of amplification, you simply adjust your digital processing. I'd ditch the DAC and put the $'s into a decent sound card instead. Else, something like this would be better.

    I'm currently running 7.1 through HDMI into 8 channels of amplification to drive a tri-amped 2 channel + 2 sub setup. Digital xover and delay is a wonderful thing.
     
  17. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    That's an option, but I don't like the idea of using PC based DAC for quality reasons (historically on-boards have been bad, and internals can suffer from noise/interference). I also feel like I need a volume nob, because lets say you do 7.1 out straight to amps, and one day a windows update comes out and the drivers "reset" and you unknowingly get smacked in the face with 100% volume - that wouldn't be a fun experience.

    It's just the old school analogue method really. But I need to make sure the values are suitable. Ultimately I'm just a resistor change away from whatever filter value I want.

    It might be temporary too, because I plan to go test some monitors out in the near future. JBL 708P look awesome, and have the specs to match, with DSP in the speaker, and powerfully bi-amped!

    Agree
     
  18. Audionut

    Audionut Member

    Joined:
    Mar 7, 2006
    Messages:
    1,540
    Location:
    4610
    Overpriced raspberry pi's that still don't solve your routing problems.
     
  19. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    Well I've had an interesting time learning how to use KiCAD (does circuit modelling and simulation), and thus wrapping my head around this amps features.

    Starting with the brown area, I was lead astray with an incorrect formula in the link I shared. I calc'd gain=1+15/27, but it's actual gain=1+27/15, so 2.8. I think R8 and R10 are a voltage divider circuit, and R10 also filters with C6? Anyway, the simulation gives the final result. It is a low pass filter at a high frequency, but it does pull down the signal a bit at 10kHz and above, but the amount is quite small (the y axis scale is quite tiny).
    brown area.png

    The blue areas are next, and I was correct on the light blue area being a low-frequency high pass filter. However, the nature of this filter puts a small hump in the upper-bass/lower-midrange. In the dark area, a google search revealed the 4.7/50 is actually a 4.7uF 50v capacitor, which works out to be a high pass filter in the single digit Hz, and so doesn't really affect the signal. I guess it is a safety feature?
    blue areas.png

    So now I've gone and combined these 2 "pass through" circuits (see below). It has a small hump at 200Hz, and it drops off over 10kHz. I now need to research if the scale of these blips is significant, because I don't particularly want this amp "coloring" the signal.
    full signal - pass through.png

    Back onto the subwoofers signal path, the purple area is the subwoofer high pass filter, aka subsonic filter or rumble filter. By its design/values, and with my laymans understanding, the "ramp" is so strong at the calculated frequency that it overshoots soon after (eventually returning to 0 gain), and this overshoot is the bass boost. I also modelled the pink phase switch to see if it was affecting the signal (which is on the graph as red signal, but is under the green signal), but it only affects the phase, as can be seen in the screenshot that has the phase switch activated (because that line off R25 goes to ground).
    purple+pink areas.png

    The variable low pass filter (light green area) works as I imagined, but it does put a small hump into the signal (which may be filtered out or made negligible elsewhere). The values on the knob are much higher than the 0dB level. The screenshot is at 0% knob level = 40Hz on the dial. I guess this is the -3 or -6dB point?
    low pass knob circuit.png

    The volume knob is a head scratcher I don't really understand*. (*actually, it might be because I'm simulating with full voltage, but as you will see in the next one, with a modified signal, it gives predictable results)
    volume knob (with 100n cap) circuit.png

    But putting the volume together with the variable low pass looks like it should, and doesn't change the signal detrimentally. You can see the hump is smoothed off a bit, but still technically there.
    both knobs circuit.png

    And now I'll put all this together in the next post... (I don't know if there's an image limit per post, but will split anyway)
     
  20. OP
    OP
    neRok

    neRok Member

    Joined:
    Aug 19, 2006
    Messages:
    4,322
    Location:
    Perth NOR
    So putting this all together gives a rather large peak to the sub signal. Here's the circuit;
    full signal - to sub - circuit.png

    It's not until the low pass knob is near max that it starts to "plateau" a little. The following screenshots are all at 50% volume, and with the low pass knob at 0%, 25%, 50%, 75%, and 100%.
    1. full signal - to sub - freq=0.0 vol=0.5.png
    2. full signal - to sub - freq=0.25 vol=0.5.png
    3. full signal - to sub - freq=0.5 vol=0.5.png
    4. full signal - to sub - freq=0.75 vol=0.5.png
    5. full signal - to sub - freq=1.0 vol=0.5.png
    So yer, that's a massive bass boost it's got. I'm going to play around with different resistor values next (in the purple area, for the rumble filter), and see what can be done about it. This Jaycar amp is very similar to Part Express model 300-793 from the same era, and the instruction sheet for that sub gives instruction on different resistor values to use, see page 2 here: https://www.yumpu.com/en/document/r...-subwoofer-amplifier-with-remote-control-wes-
     

Share This Page

Advertisement: