Where has my bass gone? :-(

[foxysounds]

My main system sounds overbright - way too much trebble and not nearly enough bass. It definitely hasn't always been like this but for various reasons it has had very little use over the last few years so I don't know when the problem might have occurred. During that time I've moved house twice. After the first move I had no bass at all which turned out to be because the surrounds for the bass cones on my JPW AP2s had disintegrated. I replaced and repaired them myself (there's a thread on that here somewhere but the forum search doesn't seem to be working at the moment) after which I could hear bass again and was very pleased with myself but it's possible that the balance was all wrong due to a botch on my part and some confirmation bias was stopping me from realising it.

It's also possible that the problem lies elsewhere entirely. Worn out components in the cross-overs for example or a problem with the amplifier.

I measured the impedance across the woofer input on the speaker (I have them biwired) and it read pretty much exactly 7ohms but when I did the same across the tweeter input I couldn't get a reading. I don't really know why. I was able to get a reading directly across the tweeter (bypassing the crossover components) but that's fairly meaningless because I was interested in finding out what impedance the amplifier was seeing.

Yesterday I needed to test a new stylus I had bought for my record deck and the only amp I have with a phono stage is the one in my main system. Knowing this was very top heavy I took the tape out from my main amp via a very long interconnect to an input on my second system and listened there. This sounded fine. My second system, like my main one, has a Marantz amp and JPW speakers (see my signature for full details). Unlike my main system however, the second one has tone controls and I did notice that I had the bass set at +4db and the trebble set at -2db which is something I had obviously done when I set it up and then completely forgotten about. I swapped the amp from my second system into my main system and listened both with the EQ settings I normally use on my second system and with it flat. It still sounded too bright with the EQ flat but didn't sound too bad with my normal settings. I'm still not completely convinced that it was right though and these kinds of changes take too long for really meaningful AB comparisons anyway.

Right now I'm just completely confused. None of this seems to make any sense and I don't know what to do next. I could move my speakers from the second system (JPW gold monitors) into my main one and listen to that but the gold monitors are so much smaller than the AP2s that there's no way I could expect as much bass from them anyway so I'm not sure what I would learn.

I'm willing to spend money on the right thing to fix this problem but I'm reluctant to chuck money at it blindly. Replacement woofers for the AP2s are still available (made in the original factory with the original tooling despite these being 30 year old speakers!) but at £150 a pair it's an expensive thing to try if I can't be sure that's the problem.

I would really appreciate any advice on how to figure out what on earth is going on. I don't have a background in electronics but I do have a little knowledge from my degree in Physics and I have a decent multi-meter which I'm not afraid to use if there's anything that needs measuring.

Many thanks in anticipation,

Simon.

[struth]

first thing is to go back to basics. single wire them and links on. then work yourself though the pieces ... amp speakers cables til you hit on the issue....your lucky you have another system to work with. if possible try and try them in the good system if the initial rewire doesnt work in main system.. ie move stuff to good system bit by bit til the bass goes

[Macca]

Is it too toppy with a CD as well? Budget belt drive turntables like your Dual are not the best for delivering solid bass and Audio Technica cartridges can sound a bit thin too.


Assuming the problem exists with CD as well, first thing is check your cabling, are you connected right? Wiring out of phase will cause that problem.


If that's not the issue then it could be a combination of factors. I like the AP2, very good small speakers with a good balance, can't see them being the problem. Chord speaker cable can sound a bit toppy depending on the rest of the system, you could try using a thicker speaker cable. And speaker positioning, are they in free space or up against a wall? Get them closer to a wall will reinforce the bass frequencies at the expense of open soundstage.


Last resort: QED interconnects can also sound a bit thin, you could consider replacing those.

[foxysounds]

first thing is to go back to basics. single wire them and links on.
Hi Grant. Thanks for the response. The AP2s have two sets of binding posts but don't come with links. Instead the two halves of the crossover are connected by wires inside the speaker. To biwire them you have to open up the speaker and cut those wires. The wire length is only just sufficient so once cut they can't easily be rejoined. Instead what I did was swap the connections so that the wires I've been using for the woofers were driving the tweeters and vice versa. Having done this on both speakers and listened again it made no discernible difference but ...


if possible try and try them in the good system
... the good system is single wired. However, trying them in the good system is a good idea so I'll need to fashion some links. I have some spare semi-decent speaker cable I can use to do this. I'll give this a try later today.

Thanks again for your input.

Simon.

[foxysounds]

Is it too toppy with a CD as well?
Hi Martin and thanks for your input. Yes - I tried multiple sources and the same problem exists with all of them which is why I suspect the speakers or amp.


first thing is check your cabling, are you connected right? Wiring out of phase will cause that problem.
Sorry - I should have mentioned in my original post that I had already checked for this and ruled that out.


I like the AP2, very good small speakers with a good balance, can't see them being the problem.
These speakers definitely have sounded very good in the past but I've done a repair on the bass drivers as I mentioned in the original post. They're also very old now and I know that some electronic components can age badly which is why I wonder about the crossovers.


Chord speaker cable can sound a bit toppy depending on the rest of the system, you could try using a thicker speaker cable.
The Chord cable is in my second system which sounds fine. The cable in my main system is QED Original Biwire. I'm pretty sure that's the exact same cable I was using when I last heard my system sounding really good so unless cable deteriorates (which I don't think it does) then I can't see that being the problem.


And speaker positioning, are they in free space or up against a wall?
They're fairly close to a wall. The original reviews of these speakers recommended keeping them well away from walls to stop the bass getting out of hand. Definitely no sign of that at the moment :-( However, your comment does make me think about room acoustics generally. It could be that the room is very bright sounding. If I fashion some links and then get these speakers on my second system which is in a different room then that could be an interesting test.


Last resort: QED interconnects can also sound a bit thin, you could consider replacing those.
Once again, I'm 99% certain I was using the same interconnect when I last had it sounding really good so this seems very unlikely. I don't have any other hifi interconnects to try it with either. I could consider replacing the interconnect with something which would sound more beefy - especially if I can pick something up second hand. That way if it makes no difference I could sell it on without too much loss. As you say, it's probably a last resort but is there anything in particular you recommend?

Thanks again,

Simon.

[hayche]

Have you walked all around your room? Is bass stronger anywhere in the room? You could be sat in a null

[Macca]

Hi Martin and thanks for your input. Yes - I tried multiple sources and the same problem exists with all of them which is why I suspect the speakers or amp.


Sorry - I should have mentioned in my original post that I had already checked for this and ruled that out.


These speakers definitely have sounded very good in the past but I've done a repair on the bass drivers as I mentioned in the original post. They're also very old now and I know that some electronic components can age badly which is why I wonder about the crossovers.


The Chord cable is in my second system which sounds fine. The cable in my main system is QED Original Biwire. I'm pretty sure that's the exact same cable I was using when I last heard my system sounding really good so unless cable deteriorates (which I don't think it does) then I can't see that being the problem.


They're fairly close to a wall. The original reviews of these speakers recommended keeping them well away from walls to stop the bass getting out of hand. Definitely no sign of that at the moment :-( However, your comment does make me think about room acoustics generally. It could be that the room is very bright sounding. If I fashion some links and then get these speakers on my second system which is in a different room then that could be an interesting test.


Once again, I'm 99% certain I was using the same interconnect when I last had it sounding really good so this seems very unlikely. I don't have any other hifi interconnects to try it with either. I could consider replacing the interconnect with something which would sound more beefy - especially if I can pick something up second hand. That way if it makes no difference I could sell it on without too much loss. As you say, it's probably a last resort but is there anything in particular you recommend?

Thanks again,

Simon.

Just try anything other than the QED, it shouldn't really make any difference but sometimes these things can surprise you. Otherwise, if you're confident this particular set of components used to sound good then I guess a fault in amp or speakers is the only thing left, although I don't know what sort of a fault would cause a lack of bass but otherwise sound fine. I've had more faulty bits of kit over the years than Amstrad and that's never one I've come across, maybe someone else here has?

[fatmarley]

You didn't replace the electrolytic capacitors in the crossover with polypropylene did you?

I have AP2s here and I agree with Martin regarding the balance. New bass drivers are worth it imo.

I'd try your JPW gold monitors just to see if they have an even frequency response. If they don't sound right then you know the problem is elsewhere.

[Pigmy Pony]

Have you walked all around your room? Is bass stronger anywhere in the room? You could be sat in a null

Yes, there is a very obvious null in my room. speaker position is important, but so is listening position.

[foxysounds]

Have you walked all around your room? Is bass stronger anywhere in the room? You could be sat in a null
Hi Howard. I've encountered this before (a very extreme case on one occasion) but the bass seems to be pretty evenly absent in this room.

[foxysounds]

You didn't replace the electrolytic capacitors in the crossover with polypropylene did you?
No - I haven't touched the crossovers - they're completely original. Could an ageing capacitor could cause a lack of bass?


New bass drivers are worth it imo.
I certainly haven't ruled out replacing the bass drivers - I just want to test out the cheaper options first :-)

Thanks,

Simon.

[foxysounds]

I do. The capacitor in the crossover blocks DC so you can't read DC resistance.
In which case I would infer that only the tweeter part of the crossover contains a capacitor (since I was able to read the resistance across the woofer) and as the woofer seems to be the problem, not the tweeter, that would suggest that the capacitor is not the problem.


When you repaired the speakers, did you replace the surrounds? Is it possible they have perished and become stiffer than when they were new? Are they foam? Rubber?
Yes, that's exactly what I did. The original surrounds had perished. I can't remember what the replacements are made of but it was only about 3 years ago so I doubt that the replacements will have perished. They certainly look to be in fine shape.

[foxysounds]

I got home from work too late today to do any listening tests at sensible volumes so I spent some time making some links so that I can use the AP2s single-wired. Tomorrow or Wednesday evening I should have time to move them onto my second system in the other room and see how they sound in there. Thanks again for all the input everyone. It's much appreciated.

Simon.

[walpurgis]

No - I haven't touched the crossovers - they're completely original. Could an ageing capacitor could cause a lack of bass?


I certainly haven't ruled out replacing the bass drivers - I just want to test out the cheaper options first :-)

Thanks,

Simon.

It's unlikely that a failing capacitor would curtail bass. If there is a cap in the bass side of the crossover, it will likely be one in parallel and if it failed only the filter slope may change, not the general output level through most of the bass range.

If the bass drivers were faulty, you'd probably hear odd noises from them or they wouldn't work at all. It's just possible that coil windings have shorted across reducing output, but I've never actually come across this, let alone on two drivers simultaneously. If you have a meter, measure the coil resistance, it should be somewhere around 4 ohms or slightly more.

[fatmarley]

Just reread the thread and the fact you use quite extreme eq on the other system makes me wonder about your hearing. Could be worth getting your hearing checked out if you can't solve the problem with component swops.

[struth]

Yup getting the speakers into other room with links on is best first step. If still no bass then it would point to speaker fault Try the second set In the other room where no bass was as well. It should have some if speaker is at fault. None again would point toward you. Then you need someone with decent hearing to do same test

It's slow but methodical wins the day

[struth]

Another quicky if not tried yet would be to switch the two big speakers round. Move the left one to the right side of room. If one driver is issue you should hear it change

[Pigmy Pony]

Hi Simon,

Probably a stupid question this, but I'll ask it anyway:

Could it possibly be something to do with the cone surrounds fitted? Could they be a bit on the stiff side? Also, do they perhaps need a kind of 'running in' period, while they loosen up?

[walpurgis]

If the cones have what appears to be the full range of back and forth movement it's unlikely there's a problem.

[fatmarley]

Hi Simon,

Probably a stupid question this, but I'll ask it anyway:

Could it possibly be something to do with the cone surrounds fitted? Could they be a bit on the stiff side?

Quite possible. I remember years ago reading Classic Speaker Pages and a common complaint was finding foam surrounds with the correct compliance to fit Acoustic Research speakers. With a stiff surround, people would complain about a lack of bass.

[foxysounds]

In post #10 I suggested the surrounds might have stiffened up. The OP seemed to dismiss that idea.
I said it seemed very unlikely because it was only about 3 years ago that I replaced them. However, it's not impossible. It also might be possible that the replacement surrounds were never very good (or that I botched the repair) and that the fact that after replacing them I thought things sounded great again was because any bass sounds way better than no bass at all, combined with confirmation bias and my possible inclination to put any remaining imperfection down to the fact that I was never able to set things up properly in the flat I was in at the time.

I have now found the thread in this forum where I came for advice when the original surrounds disintegrated. Unfortunately many posts seem to be missing from the thread including the one where someone gave me a link to the supplier of the surrounds :-(

My week is filling up with other stuff so apologies that I haven't had a chance to try everything that has been suggested yet. I do intend to get to it. I remain grateful for all the input.

Regards,

Simon.

[foxysounds]

Hi again.

Yesterday I had a chance to try move things from room to room and try out many combinations. I won't list all the combinations I tried and my thoughts on each - instead I'll skip to my conclusion which is that there is bass coming from the AP2s but it doesn't have the punch that I believe I remember it having. Subjectively I hear more bass from my DT770 Pro headphones and my car audio system* than I do from the AP2s. Also the balance between the bass and the trebble is not right to my ears - the trebble is a bit forward and harsh sounding in a way I don't remember from before. The Gold Monitors are not producing more bass than the AP2s, in fact they are producing slightly less, but given the size difference between these speakers I would expect more from the AP2s. The AP2s sound a bit fatiguing. Speaker placement does not appear to be the problem.

One thing I wasn't able to try with the AP2s was alternative speaker cable. The cable for my second system is routed behind and through bookcases which would have to be emptied to free it. However, I did try the gold monitors with the cable from the AP2s.

It has been a few years now since I've had this set up properly during which time most of my listening has been on my car system during my lengthy daily commute so it is possible that to an extent I have just got used to and now prefer the sound of that system but I'm also obviously suspicious that the AP2s are not giving their best since my repair.

I have a number of possible options for next steps and I think I'm going to try several:

Buy a second hand pair of speakers to use as a comparison. The Gold Monitors are not very useful in this respect because they don't have sufficient bass extension. I've seen a couple of possibilities on eBay including a pair of B&W DM602 S3s. If I don't like them I can sell them on again for little loss. Ideally I'd compare them first with a mint pair of AP2s but the odds of finding such a thing are very small indeed.
Buy some different speaker cables as a comparison. I see from another thread that there are very cheap cables that at least one member of the forum swears by so it would be foolish not to try them.
Shorten my current cables. At the moment my speaker cables are 10m long each side because of a room I had them in years ago. I could comfortably halve this now. The extra coiled up cable cannot be helping. Previously I've balked at this because it means losing the shop-fitted banana plugs on one end but I expect any benefit to be gained from them is lost from 5m of extra cable.



I'm looking forward to trying new things!

Thanks again,

Simon.

*Stock 2004 Honda Civic speakers but with a replacement Pioneer head unit of my choosing.

[Macca]

I think you should try different speakers first. The B&W 602 are pretty good if you can find some for a ton or less. I wouldn't pay more than that. There's a zillion second hand speakers out there, it's a buyer's market.

[fatmarley]

I had Gold monitors and I thought they had good bass for a sealed box speaker. I really don't think it's a speaker problem although a ported speaker would probably help. Smaller sealed speakers usually have a hump at around 100hz to give the impression of more bass. A good ported speaker will have a more linear low frequency response down to cut-off (More output in the 50hz to 70hz range) but the lows usually drop off much faster. Subjectively a ported speaker often has more thump but that obviously depends on the speaker.

I'd be surprised if the harsh treble came from the speakers. You can buy brand new tweeters for about £15 each to rule that out. Do any of your cables have silver in them? That can give harsh high frequencies. A Quad 306 has good punchy bass, clean mids and very smooth highs. They only cost around £200. Couple that to a little bear passive pre amp off ebay for £25 and then all you need is some extra interconnect cables. Flashback sales do copper RCA cables that sound pretty neutral to my ears.

I personally don't like B&W 60X speakers and much prefer tha Kef coda 8. They have much better integrated and smoother treble and the mids are more open. Bass is good but wont be as tight as the AP2.

[foxysounds]

Thanks everyone - the problem is now solved. I took my AP2s with me to Sevenoaks Sound & Vision in Cambridge this afternoon and compared them to a couple of other pairs of speakers. I came away with a pair of B&W 685 S2s. I've spent a couple of hours this evening listening to them and I'm really pleased with the sound even though they're not even properly run in yet - a big improvement on the AP2s.

Of course I still don't know for certain whether new bass drivers for the AP2s would have improved things but sadly I can't buy the replacement bass drivers and then return them if I don't like them so to spend £150 trying that out was a bit of a risk. In the end I spent a lot more than that but at least I knew I'd solved the problem at the point that I parted with my cash.

The people at Sevenoaks were very helpful and accommodating. All in all, a good day :-)

Simon.

[Puffin]

Could it be that after the new surrounds were fitted the position and neg connections were inadvertently swapped on one speaker.

[fatmarley]

Could it be that after the new surrounds were fitted the position and neg connections were inadvertently swapped on one speaker.

Got to be worth checking. Also worth checking that the enclosures are perfectly sealed with no air leaks.

[Puffin]

Got to be worth checking. Also worth checking that the enclosures are perfectly sealed with no air leaks.

POSITIVE.....not position....didn't see that when I posted!

[AJSki2fly]

Hello Simon

Reading though the thread it sounds like you've tried most of the obvious. so here are a few not so obvious that might be worth trying. Systems don't usually just loose bass.or other frequencies.

1. Bass can be elusive if the room causes reflection and cancelling standing waves. What I mean about this is if the room is a tricky shape then the positioning of the speakers and where you sit may be critical. My listening room is 22 foot by 12 foot and have to have the speakers 62" from the wall and then I have to sit about half way down the room for the bass sweet spot or at the other end with curtains drawn to stop reflections.

2. Please don't take this the wrong way but have you really lost bass or have your ears? If you have a modern mobile download a dB meter that can measure levels across the frequency range. alternatively there is a very good bit of free software call REW which you can measure you speakers output accurately. you could download a free hearing test software.

I hope this may shed some light

Regards

Adrian

[foxysounds]

Could it be that after the new surrounds were fitted the position and neg connections were inadvertently swapped on one speaker.

No - I tested that. The speakers are biwired so it's really easy to invert the phase on a single driver without re-opening the boxes. They are definitely in phase.

[foxysounds]

1. Bass can be elusive if the room causes reflection and cancelling standing waves.
Hi Adrian,
Yes - I know. However, as I posted previously, moving around the room produces very little difference in perceived bass and for there to be a pronounced bass trough somewhere in the room you would expect a peak elsewhere and I can't find one. Also, my new speakers are sounding distinctly more bassy in the same position.

Please don't take this the wrong way but have you really lost bass or have your ears?
Well, I hear the bass just fine in my other systems so Occam's razor suggests my ears are not the problem :-)

Cheers,

Simon.