Missing bass punch on Quest?

[Agosto]

Hi

I own my Quest II since new and - perhaps it is me getting old - I am getting frustrated with the bass reproduction of my speakers. In particular, I am missing the "punch" which perhaps was there earlier but now it sounds more like banging on a plastic bucket. I had the bass speakers tested and refurbished by a company in Florida recommended by ML to no avail. Could there be an issue with the crossover? Any recommendation? Needless to say the associated amplifier and sources have not changed. Thanks a lot!

 

[JonFo]

Based solely on age, it is possible the capacitors in the crossovers need replacing.
I recall we had several threads here of folks upgrading / replacing the caps on their passives, some even specific to the Quest. Look in the DIY subforum.

Of course, if you are technically inclined, you could go the active crossover route, which results in much better sound overall, as you can move up the XO point a bit and let the woofers handle more of the bass and deliver more mid-bass 'punch'.

 

[lifespeed]

Are you sure you don't have Request II? I don't find Quest II specs on ML's website. The woofer specs and crossover freq are different from my Quest z so probably not appropriate to suggest the same replacement driver. You might ask ML for their suggested replacement if you think yours aren't good anymore.

Also it doesn't hurt to post what you're driving them with.

 

[Agosto]

lifespeed, my apologies: I meant to write "Quest Z". Any feedback on your woofer swap? I am driving the Quest Z with a Mark Levinson 333. Thanks!!

 

[Agosto]

JonFo

thanks for your suggestion re capacitor upgrade. I already did this and at this point I do not want to go active. Your link to the DIY forum helped a lot!!

 

[lifespeed]

I looked up your Mark Levinson 333 amp, it is impressive. Never hurts to include a link in your posts for lazy readers. It is every bit as powerful as the Parasound JC5 I use, if not more so. So an underpowered amp wouldn't be suspect, except it's an old amp. Dried out capacitors in the power supply could limit it's ability to source instantaneous current, but this is just a guess. Do you have the possibility to swap out for a different, suitably powerful amp to see if your bass improves? It would seem the first step is to confirm which component you should be looking at as the source of the problem. It may be your amp is fine, but unless you start swapping components you don't have a good way to know. Have you ruled out obvious problems like an undersized 120V circuit or speaker cables?

You could blindly replace the drivers with the Dayton Audio DCS305-4 12" Classic Subwoofer 4 Ohm, Parts Express #295-204, and you might well be correct. Drivers do get old and it would cost only $200. I did hear an improvement when I replaced my OEM woofers with burned out voice coils (bad amp took them out). I wouldn't say it was night and day, but they're noticeably better.

What about your room? Before I added 4" thick rock wool absorbers on the wall behind the listening position, the bass was boomy (peaks), which by definition are accompanied with troughs in the frequency response. It could really rattle the walls at the right frequency, but peaky response like that is not a good thing.

Are your expectations realistic, or are you comparing Quest Z low frequency extension to a system with a subwoof? Even with the replacement drivers, these things barely go down to 24Hz. I think the factory spec is 28Hz.

I guess I'm just suggesting to take a step back and look at everything, and troubleshoot. Then replace the woofers if you think it makes sense.

 

[Agosto]

Thank you for your detailed response. I probably should have been more descriptive in my posting but let me tell you that I tested the speaker with different amps and the room acoustics has been the same since many years. I already replaced the electrostatic panels with great effect and I upgraded the crossover with new and better capacitors. I guess my question to you boils down to this: Do the Dayton replacement woofers have a better defined bass than the originals? You mentioned an improvement („noticeable better“). Do dynamic speakers lose their physical ratings (e.g. magnetic flux) over time? My speakers were manufactured in 1993....
Thanks again!

 

[patounet]

OK, I agree about the "bass punch" lacking on Quest Z or Request or Prodigy. I made a lot of tests about the crossover and tried to find better capacitors. I spent time and much money replacing chimical capacitos by Mundorf MKP capacitors, even 330uF value as big as a Coke can and very expensive. Yes It works better, punch increases, especially if you use two capacitors in a parallel mounting... BUT... the level of bass becomes too high, it spoils the ESL reproduction as if the crossover frequency had changed. The Martin Logan loudspeaker becomes nearer a dynamic speaker, do you want that ? And if you put - even a small resistor value - to decrease that, the bass becomes amortized. If you use an other trademark capacitor than the original one, even with the same value you do not have the same sound. This means that Martin Logan set up the loudspeaker with a specific capacitor model and trademark. You will become crazy trying different capacitors. So I ordered Martin Logan new original capacitors that they had in stock. And I forgot... Sorry to tell you that. Don't go on this way, changing the capacitors. But try some other cables or electronics with tighter bass, or go to the new ML series 11A, 13A or 15A. Regards from France. Some shots of new capacitors in my Prodigy crossover attached.

 

[lifespeed]

Do the Dayton replacement woofers have a better defined bass than the originals? You mentioned an improvement („noticeable better“). Do dynamic speakers lose their physical ratings (e.g. magnetic flux) over time? My speakers were manufactured in 1993....
Thanks again!

Yes, the Dayton woofers have a better defined bass. I'm not completely sure what the aging mechanisms are for a dynamic driver. I know permanent magnets can weaken over time, and the "spider" voice coil suspension can wear also.

How the drivers will sound to your ears in your room is hard to say, but it isn't the most expensive audio experiment to try.

 

[lifespeed]

If you use an other trademark capacitor than the original one, even with the same value you do not have the same sound. This means that Martin Logan set up the loudspeaker with a specific capacitor model and trademark.

Capacitors have non-ideal characteristics such as Equivalent Series Resistance (ESR). I would expect a good engineer to account for this and other parameters in their design.

 

[spkrdctr]

When you have tried everything and are still in doubt. Buy a new pair of whichever model you like. I can say that many times a new pair of speakers will sound so much better than a 20 year old pair. I fixed speakers for a living many years ago. Technology of drivers has come a long way. After 20 years it's time to buy new. In my most humble of opinions. OK, very humble.

 

[lifespeed]

When you have tried everything and are still in doubt. Buy a new pair of whichever model you like. I can say that many times a new pair of speakers will sound so much better than a 20 year old pair. I fixed speakers for a living many years ago. Technology of drivers has come a long way. After 20 years it's time to buy new. In my most humble of opinions. OK, very humble.

Are you suggesting new drivers, or a brand new pair of floor standing speakers? New drivers would seem to be a completely valid suggestion.

 

[Agosto]

Thank you all for your valuable feedback.
Patounet: I principally agree with you that a change in capacitor can bring along side effects due to individual capacitor specifics. However, in case of the Quest Z bass crossover - which is a quite simple filter - I fail to see any negative impact. And even if, I would not expect this to have an influence on the bass „punch“, more so on the filter characteristic. I also changed the capacitor in question based on a recommendation from ML.

Lifespeed: I guess you are correct: I am going to try the Daytons. Quite affordable...

Spkrdctr: I concur with you assessment that technology has advanced since the 90s, however, I am currently not in a position to shell out money for a new set of speakers. Valid comment, though.

 

[R.I.P]

I agree with Lifespeed important to trouble shoot prior to replacing woofer. Try inter changing interconnects and if your source was acquired in 1993 then your source may cause poor bass performance. You must rule out all possible causes of poor bass performance other than woofers. If you do not troubleshoot, after expending effort and expense you may end up with the same bass sonics from new woofers.

 

[rawatch]

I own a pair of quest z speakers I replaced the woofers with the peerless also bypassed the crossover and used the minidsp hd Biamp the speakers what a huge difference adding a sub made it world class

 

[Mirolab]

I've often thought of going active DSP crossovers on my SL3 woofers, but concerned about the latency introduced to the woofer only. I've read that the MiniDSP latency is 1ms, which is like locating the woofer 1 foot behind the ESL panel. This should not be much issue down at 120 Hz, but the SL3 crosses over at 250 Hz, so 1ms is about a quarter wavelength. Integration might be difficult, unless I put DSP on the panel too.

 

[rawatch]

I am running the woofer 80 to 300 and the panel 300 and up with the Minidsp hd

 

[Agosto]

So I ordered the Dayton woofers after ruling out any other problem area (source, crossover). Unfortunately, the bass did not improve - marginally perhaps.
@lifespeed: I forgot to respond to your amplifier suggestion re old capacitor etc. I had the Mark Levinson fully serviced and upgraded two years ago at a ML repair center. Quite expensive but they did a thorough job. So I can rule out the amplifier. I also checked speaker input signal strength with a signal generator and a scope. No drop at low frequencies.
Not sure where I will go from here...perhaps I am going to re-position the speakers but I doubt that his would significantly change the picture.

Any suggestion for music material with a known good bass punch?

 

[Chops]

Do dynamic speakers lose their physical ratings (e.g. magnetic flux) over time?

I was hoping I would have been able to see and answer this before you went out an purchased new drivers. But the quick and simple answer is "No".

Other than a completely blown voice coil, the only other thing that can cause a woofer to go bad or sound "off" is a sagging suspension (spider and surround). But then you would clearly be hearing the voice coil rubbing on the pole piece, not a completely different sounding bass like you are describing.

Permanent magnets are just that, permanent. They lose a tiny bit of flux over time, but that's a very very long time, or in extremely high heat situations, neither of which is the case with your Quest Z's. And you can't just throw any random driver in there willy-nilly as their T/S parameters are totally different and will throw off the specs of the crossovers.

When exactly did you start noticing this change in the bass? At that time, did the speaker locations change at all? Were there any new furnishings added or removed from the room at that time? Did you listening position change at all at this time? Was there any new gear or cables added to the system at this time?

Clearly, we can rule out the crossovers, amplifier and woofers. I hope you reinstalled the original woofers. And just in case you are concerned about the suspension sagging, you can always rotate the drivers 180 degrees when you reinstall them.

Just as a side note, I had my 22 year old SL3's open a couple months back. I removed the 10" woofers and took a good look at them. No hint of sagging at all, though I did reinstall them rotated 180 degrees just because.

Suggesting music with good bass punch probably won't help you much if you're not already familiar with the music and how it's supposed to sound in your system. You would have no reference to go off of.

Can you give us a run-down of the rest of your stereo equipment, and possibly approximate age? Do you have any tubes in your system?

 

[Chops]

I made a lot of tests about the crossover and tried to find better capacitors. I spent time and much money replacing chimical capacitos by Mundorf MKP capacitors, even 330uF value as big as a Coke

I can't help but notice the four electrolytics on the right side of the crossover network. I imagine the two larger ones in the corner are probably for the woofer, if not all four of them along with that resistor. If so, it looks like you replaced everything BUT those.

Also, I have done countless cap and resistor upgrades on countless loudspeakers over the years, and I never encountered any ill side effects from doing so as you have mentioned.