Can someone explain to me what causes some units to distort as bass and volume increase. Is there any mod that can be done to address this?

add a larger amplifier, more power, or use - to replace your speakers with more modern - more efficient , higher spl-sound pressure level , speakers. to get more sound out of underpowered systems

To put it simply, lower quality amplifiers become unstable and are unable to clearly maintain certain frequencies at increased volumes. Low quality speakers can also be a culprit. Sometimes adding better speakers can help but if the amp cannot produce "clean" sound at higher volumes, then the best speakers in the world won't help. So the answer to your question is "maybe" it can be improved with better speakers but not always. Modding the electronics part is not happening except for possibly adding caps to the outputs but again, if the amp is crappy, then its a waste of time.

quote:

Originally posted by Panabox:
Can someone explain to me what causes some units to distort as bass and volume increase. Is there any mod that can be done to address this?

This is far more complicated that just switching amps etc.

You need to take into account limitations of the box. The speakers may appear to be the easiest part but here are some things to consider:

1. What is it your trying to get distortion out of? Is it a powerful component unit (JVC PC55) or large powerful box (Conion C100F)? Powerhouses like these are often easy to resolve since the speakers are usually inadequate for the power built into the units. Keep in mind impendance and sensitivity will affect output if you were to switch speakers.

2. Power ratings? What are they and is it lower than the speaker being driven. Every amplifier will go into a stage known as clipping. Once it hits this stage the sound will distort badly. Usualy the bass is the first to go and you'll have a more screechy loudness than clean.

3. Case/Cabinet design? Most spekaers perform better in an enclosure. This is why quality component boxes will generally always sound better than a single piece unit. It's a natural advantage. But not always in all situations. When a speaker is restricted to movement i will operate tighter and have less opprtunity to throw beyond its means when pushed. This is why the Toshiba WX-1 is so rich sounding. It uses a passive radiator design with a small woofer which when you see it you'd say 'No F'in Way!!!". But that's what good design does.

The bottom line is this, there are a lot of factors to consider and calculate. Even the power supply comes into play. The amp will run out of steam as well if it's starved for juice.

This list is but a few.

with james and bash --

and panabox -- do understand that these are only portable boomboxes --
and they pretty much ALL distort at loud bass levels --and much sooner if you keep your loudness switch on --

the only OEM stock boxes i ever heard that can REALLY by run up loud and clean are these two panasonic lines ::

their bi-amp platinum series --
and their commercial boxes :: rx-a5 and rx 6400

another distortion type is amplifier distortion, its when the input signal gain forces the output signal to exceed the limits of the power supply rail that feeds the amplifier. It literally "clips" the upper and lower part of the sine wave which becomes audiable distortion.

This is the most common type.

Also poor driver quality like stamped frames that vibrate when the driver moves also adds distortion to the signal.

Anything that is loose or rattles can add distortion.......the list goes on and on.

Thanks guys, maybe I'm being too critical. The reason why I asked is because I own a Panasonic RX-DT680. Don't get me wrong, this thing has some serious bass. In fact, it's the deepest hitting unit I've heard for a portable. But as the volume increases beyond 4.5, some of the midbass and mid vocals begin to distort. But the speaker movement hasn't even began to reach its max. In fact if I continue to turn it up, the mid frequencies continue to distort, but the low bass comes through just as strong and clean. It's just hat the bass has to compete with the distortion of the mids. I can't figure that one out. And I'd like to somehow address this. But again,if the volume is kept at 3 while the S-XBS is at its max and the 100hz in the middle, this unit is flawless and will fool many into believing that its a mini home system. It's just that as the volume increases, steam starts to escape from somewhere. Maybe if the woofers didn't have to play the role of reproducing both vocals and bass, this problem wouldn't exist.

quote:

Originally posted by kittmaster:
another distortion type is amplifier distortion, its when the input signal gain forces the output signal to exceed the limits of the power supply rail that feeds the amplifier. It literally "clips" the upper and lower part of the sine wave which becomes audiable distortion.

And that clipping is bad for both the amplifier and the coil of the speaker(s) so in fact driving a box to it's limit is a big nono

quote:

Originally posted by Eddy:

quote:

Originally posted by kittmaster:
another distortion type is amplifier distortion, its when the input signal gain forces the output signal to exceed the limits of the power supply rail that feeds the amplifier. It literally "clips" the upper and lower part of the sine wave which becomes audiable distortion.

And that clipping is bad for both the amplifier and the coil of the speaker(s) so in fact driving a box to it's limit is a big nono

quote:

Originally posted by Panabox:
Thanks guys, maybe I'm being too critical. The reason why I asked is because I own a Panasonic RX-DT680. Don't get me wrong, this thing has some serious bass. In fact, it's the deepest hitting unit I've heard for a portable. But as the volume increases beyond 4.5, some of the midbass and mid vocals begin to distort. But the speaker movement hasn't even began to reach its max. In fact if I continue to turn it up, the mid frequencies continue to distort, but the low bass comes through just as strong and clean. It's just hat the bass has to compete with the distortion of the mids. I can't figure that one out. And I'd like to somehow address this. But again,if the volume is kept at 3 while the S-XBS is at its max and the 100hz in the middle, this unit is flawless and will fool many into believing that its a mini home system. It's just that as the volume increases, steam starts to escape from somewhere. Maybe if the woofers didn't have to play the role of reproducing both vocals and bass, this problem wouldn't exist.

You may have a progress loudness volume knob. After around 40% the loudness circuit is disabled. Also, get a pair of medium to studio headphones, how does it sound there? That will help elimate if its a limitation of the amps or speakers.

Here's from the manual of the RX DT-680:

output: speaker; low; 2.7-8 ohms.
high; 8-16 ohms.

On the CD section the s/n ratio: 95dB (1KHZ)
Dynamic Range: 86dB
Frequency Response: 20Hz-20kHz

On the tape section Frequency Response:
Normal tapes: 20-16000Hz
Cr02: 20-17000Hz

I'm thinking of getting some new speakers they are at 35 watts RMS/ 70 watts Max, 8 ohms *Re: 6.4, 86db and frequency range 45-5,000 Hz. Is this ok to use on the DT-680 I know that most boomboxes rate around 20-30 watts total my DT-680 states 57W but thats power consumption. Sorry Panabox for Hi-jacking your thread this could be of help to you too.

quote:

Originally posted by kittmaster:

quote:

Originally posted by Panabox:
Thanks guys, maybe I'm being too critical. The reason why I asked is because I own a Panasonic RX-DT680. Don't get me wrong, this thing has some serious bass. In fact, it's the deepest hitting unit I've heard for a portable. But as the volume increases beyond 4.5, some of the midbass and mid vocals begin to distort. But the speaker movement hasn't even began to reach its max. In fact if I continue to turn it up, the mid frequencies continue to distort, but the low bass comes through just as strong and clean. It's just hat the bass has to compete with the distortion of the mids. I can't figure that one out. And I'd like to somehow address this. But again,if the volume is kept at 3 while the S-XBS is at its max and the 100hz in the middle, this unit is flawless and will fool many into believing that its a mini home system. It's just that as the volume increases, steam starts to escape from somewhere. Maybe if the woofers didn't have to play the role of reproducing both vocals and bass, this problem wouldn't exist.

You may have a progress loudness volume knob. After around 40% the loudness circuit is disabled. Also, get a pair of medium to studio headphones, how does it sound there? That will help elimate if its a limitation of the amps or speakers.

Good Idea! I'll try that. Oh an ford93 no prob man! I'm all up for good ideas.

Be careful with the speaker selection guys. That bi-amped setup will restrict you on a couple of fronts.

The DT-680 and others like it have the crossover basically built into the amp section. (Highs driven to the 8-16ohm side, lows to the 2.7-8ohm side.) If you replace the bass side with a higher resistance speaker (say 6-8ohms) you will lose output volume and have to work the amp harder to achieve the desired volume. That is the reason they can get as loud as they do because of the low impendance the woofer has. The mid-tweet isn't as bad because the higher frequencies are easier to push.

The other problem you may encounter is that the system is balanced so that the amps are acting in unison on the volume level output. A change in speakers may affect this dramatically.

Is there a modification or a known replacement that can be done to the amp of the 680? Because I've noticed that as the volume is cranked, whenever the bass (especially the hard mid bass) notes hit, the power light dims and those notes distort. Perhaps if there was more power to add or free up as the volume increases, the distortion could be minimized greatly.

quote:

You may have a progress loudness volume knob. After around 40% the loudness circuit is disabled. Also, get a pair of medium to studio headphones, how does it sound there? That will help elimate if its a limitation of the amps or speakers.

I tried the headphone experiment and discovered the culprit. It's not the speakers, so it must be the amp. Listening through the headphones, I experienced the same acoustical characteristics that I heard through the units speakers. As I crank the volume with the bass up (headphones or not) it starts to distort (almost like a spitting or "beepboxing" sound instead of smooth solid bass notes as when the volume is at 3 or 4.

quote:

Originally posted by oldskool69:
Be careful with the speaker selection guys. That bi-amped setup will restrict you on a couple of fronts.

The DT-680 and others like it have the crossover basically built into the amp section. (Highs driven to the 8-16ohm side, lows to the 2.7-8ohm side.) If you replace the bass side with a higher resistance speaker (say 6-8ohms) you will lose output volume and have to work the amp harder to achieve the desired volume. That is the reason they can get as loud as they do because of the low impendance the woofer has. The mid-tweet isn't as bad because the higher frequencies are easier to push.

The other problem you may encounter is that the system is balanced so that the amps are acting in unison on the volume level output. A change in speakers may affect this dramatically.

sorry for butting in! but i'v been serching arround for replacement woofers for my panasonic rx-dt75, the few 8cm woofers that i found,where 8ohm.Is it possible to get woofers this small,that are 2.7ohm?
Regards
Jack.

quote:

Originally posted by oldskool69:
Be careful with the speaker selection guys. That bi-amped setup will restrict you on a couple of fronts.

The DT-680 and others like it have the crossover basically built into the amp section. (Highs driven to the 8-16ohm side, lows to the 2.7-8ohm side.) If you replace the bass side with a higher resistance speaker (say 6-8ohms) you will lose output volume and have to work the amp harder to achieve the desired volume. That is the reason they can get as loud as they do because of the low impendance the woofer has. The mid-tweet isn't as bad because the higher frequencies are easier to push.

The other problem you may encounter is that the system is balanced so that the amps are acting in unison on the volume level output. A change in speakers may affect this dramatically.

So I would have to get woofer speakers that equavalent 2.7-8ohms not 8ohm and up?

Guys, I'm thinking that maybe the culprit is the amp, not the speakers. Maybe try hooking up 680 speakers to a home unit (careful though, I wouldn't crank it up), and seeing the level of distrtion it lacks then.

P.S. I am not a technician, not even close. So take my advice with caution. Please.

quote:

Originally posted by ford93:
So I would have to get woofer speakers that equavalent 2.7-8ohms not 8ohm and up?

That would be your best bet. Also check the sensitivity. A higher dB sensitivity rating will offset some of the resistance gained by using a higher ohm speaker load. (2.7ohm speakers are a hard find off the shelf.) It's a lot of math to figure it out but check your DT-680 speaker specs and work off of those to ensure that you go above the manufactured (original) sensitivity specs if a higher ohm speaker is used. That's the simple method. Keep in mind that a 1dB increase in sensitivity is like adding a third more power to your amp in a sense because the speaker will play louder at the same volume levels as the originals. Also beware, this will not neccesarily equate to more bass, etc. It all depends on the frequencies the speaker is designed to produce and the cabinet it's in.

I checked the manual it does not mention anything petaining to sensitivity on the speaker section. Like I mention before on the CD playback it states S/N ratio at 95dB (1KHZ) and Dynamic range at 86dB. Would this help into what type of speakers I should look for?

I know that the speakers I was interested are 35watts to 70watts max at 8ohms 86dB then it also saids *Re 6.4 not sure what that means unless it is that it goes down to 6.4ohms?

Unfortunately the S/N ratio is at measured playback on test equipment.

The 6.4 would be the dip the speakers would take resistance wise under load it sounds like. Most speakers operate within a given range of resistance so that sounds correct.

You may be able to find out what the originals are via the web. I'm curious myself so I'll look as well. I don't think 8ohms is a problem as long as you get good sensitivity.

quote:

Originally posted by oldskool69:
Unfortunately the S/N ratio is at measured playback on test equipment.

The 6.4 would be the dip the speakers would take resistance wise under load it sounds like. Most speakers operate within a given range of resistance so that sounds correct.

You may be able to find out what the originals are via the web. I'm curious myself so I'll look as well. I don't think 8ohms is a problem as long as you get good sensitivity.

Besides the actual speaker replacement, is there an actual component (such as an amp) within the unit itself that can be replaced to help deliver more power at the higher volumes. Or what about a pre-amp. How do those things work. Could that be added if there was room?

quote:

Originally posted by Panabox:
Besides the actual speaker replacement, is there an actual component (such as an amp) within the unit itself that can be replaced to help deliver more power at the higher volumes

Unfortunately, no. The amps are built into the main section behind the control board that houses the EQ, LCD, etc. Plus, you have to consider the power supply, heatsink, and resitors and other items in the circuit as well.

There is no direct replacement that is more powerful that I know of that could possibly be suited to this box because of its design (bi-amped). And once you step into that kind of modding, you really get away from what makes it special in the first place IMHO. Panasonic really got it right with this one with "maybe" the exception of raw power and loudness. And as with most electronics by the time this was made, not freindly to modification.

Speakers would be the safest and best bet to "get more" out of it. Other than that, I would not get into the guts or you could risk upsetting the dynamics of that bi-amped setup. It is already a fantastic sounding box. And even though I agree it loses steam as you wind it out and have stated the same before on this site I would not change a thing. On the inside at least.

quote:

Originally posted by oldskool69:

quote:

Originally posted by Panabox:
Besides the actual speaker replacement, is there an actual component (such as an amp) within the unit itself that can be replaced to help deliver more power at the higher volumes

Unfortunately, no. The amps are built into the main section behind the control board that houses the EQ, LCD, etc. Plus, you have to consider the power supply, heatsink, and resitors and other items in the circuit as well.

There is no direct replacement that is more powerful that I know of that could possibly be suited to this box because of its design (bi-amped). And once you step into that kind of modding, you really get away from what makes it special in the first place IMHO. Panasonic really got it right with this one with "maybe" the exception of raw power and loudness. And as with most electronics by the time this was made, not freindly to modification.

Speakers would be the safest and best bet to "get more" out of it. Other than that, I would not get into the guts or you could risk upsetting the dynamics of that bi-amped setup. It is already a fantastic sounding box. And even though I agree it loses steam as you wind it out and have stated the same before on this site I would not change a thing. On the inside at least.

Thank you! I'm really learning a lot from you. I guess the thing is is that this unit really does excel. I mean it's got a depth to the sound that I have yet to hear from any other box. It's just that it sounds so go that to turn it up even at only 4.5 (on some bass heavy music) and to start hearing distorted mid-bass start to "spit" completely contrasts the smooth solid sounds that were only a few volume levels down. If there was someway I could address this as the volume increased, this unit could pass for a home system easily. It's that good! Do you mind telling me a bit about pre-ams and how they work? If this is a do-able route, I wouldn't mind converting the battery housing into a space for that if that were possible. Thanks again oldskool69, I'm starting to develop a healthy respect for your feedback.

Well, I'd be careful about developing a respect for anything I say, ask Redbenjoe!

About the only thing you might accomplish with a pre-amp is boosting the signal from the inputs. Which means you'll distort faster. You'll also need to keep in mind the specific millivolts each circuit (CD/TAPE/TUNER) is designed to feed to the amp. You will not want to exceed this as you may create unwanted noise or worse. As noted before, what you want to do here is a mighty task even for seasoned veterans. (Not so much that it's difficult for them to assemble a circuit, it's just getting the results (sound) right will make you pull your hair out. I have a freind who is an audio engineer for theatres and even after 25 years he says it's a pain in the a@@. )

And speaking of getting it right, I went bonkers just changing speakers on my Sanyo C9. Testing, experimenting, on and on, and that was just a speaker swap!

that c9 speaker swap was totally respectable !!
and well worth the bonkers

quote:

Originally posted by oldskool69:
Well, I'd be careful about developing a respect for anything I say, ask Redbenjoe!

Wait a minute, are you saying you respect Ira's opinions?

quote:

Originally posted by Fatdog:

quote:

Originally posted by oldskool69:
Well, I'd be careful about developing a respect for anything I say, ask Redbenjoe!

Wait a minute, are you saying you respect Ira's opinions?

Well, I've been a bit delirious of late, but hopefully sound advice has been given otherwise.