Generally speaking and all things being equal, does an amp have to work harder to reproduce say a 50hz note than it does to reproduce a 95hz note?

Yep.

I would say so also.



Johnny

I thought so. But now I'm even more confused. I'm trying to understanding my RX-DT680 and I'm thinking that the best way to figure this all out is simply to talk it out. So here it goes:

Since it takes more power to produce lower frequencies than it does higher ones, I can't figure out why Panasonic's RX-DT680 does so well, extremely well actually, producing those low bass notes but at the same time distorts the higher bass notes. How can this be?

Oh and on a side note, I read on youtube that the RX-DT 690 has 90 watts while the RX-DT680 is rated at 57 watts. Is this true? I thought they both were rated at 57 watts.
Thanks!!

Hey oldskool just wanted to ask if you would be doing a review of the RX-DT680 anytime soon.

I hope to get enough time to do a bunch of reviews including the 680 soon. We will be having some changes in our house that will allow more time after January 12, 2009.

Somewhere in this forum it is written that the RX-DT 690 has less actual bass than the RX-DT680.The DT690 is a 3 way design while the DT-680 is a 2 way design.Given this you would think that the 690 is upmarket from the 680 and would have better bass.I'm not sure about the rated power of a 690.

If oldskool does a 680 review I hope he compares it to some classic era boxes,especially in the area of high frequency presence.I find the 680's highs to be pretty configurable with some EQ band adjustment.It can sound either polite or closer to an old school box to my ears if so desired.It's an amazing box!

I picked up a 57 watt 680 yesterday and the sound is INCREDIBLE

-gsbadbmr

quote:

Originally posted by gsbadbmr:
I picked up a 57 watt 680 yesterday and the sound is INCREDIBLE

-gsbadbmr

Congrats man!! You're right, overall the sound is incredible. Especially the low bass, it belts out the low tones with ease. I love watching the speakers move violently when say a 45hz note or lower comes rushing through. To really appreciate how serious it is with the low bass you have to stand at a distance, (perhaps upstairs, while the box is downstairs) to see just how well the bass carries.

On the back of the speaker cabinet it has the following information regarding Impedance:
High 8ohms
Low 2.7 ohms
Yet on the back of the unit itself it gives a range:
High 8 - 16ohms
Low 2.7 - 8ohms
Why is this?

This Panasonic uses a quad-amp design, each speaker has its own amp. It has a strong amp for the mid-woofers (about 6 watts per channel) and a smaller one for the tweeters (2 watts or something). They both run with the same voltage but the current of the bass amp is higher due to lower impedance.

This bi-amping design has advantages over conventional amping when the box is pumping near full volume as the highs still come clear while the bass is at its limit. A stronger (bridge) amp with a simple crossover would also do a good job in those


The listing on the back should be near the jacks where you can connect external speakers.

The speakers on the 3pc Panasonic RX-DTs are bass reflex designs. Bass reflex designs are tuned to certain frequencies, & so will reproduce those frequencies at a higher volume without distortion. Perhaps the tuned frequency for the RX-DT speakers is at the low-bass end, so it can thump out that, but handles mid-bass less well.
Remember, boomboxes are always a sonic compromise...

Also, it could be that the mid-bass distortion is due to resonances in the speaker cabinets?

quote:

Originally posted by Panabox:
[QUOTE]Originally posted by isolator42:
The speakers on the 3pc Panasonic RX-DTs are bass reflex designs. Bass reflex designs are tuned to certain frequencies, & so will reproduce those frequencies at a higher volume without distortion. Perhaps the tuned frequency for the RX-DT speakers is at the low-bass end, so it can thump out that, but handles mid-bass less well.
Remember, boomboxes are always a sonic compromise...

Also, it could be that the mid-bass distortion is due to resonances in the speaker cabinets?

The distortion of the midbass, I've noticed, follows the same characteristics whether I'm listening via the headphones or the unit's speakers themselves. When I put my ear to the porthole, all of the bass, low, mid, and high has a distortion-free sound. It's very clean. When you put your ear to the speaker is where the distortion is heard. It's the darnedest thing trying to figure this thing out. Why oh why can't it play the midbass as cleanly as it does the low bass at higher volume. If anyone has a bass CD, listen to it and play it as you turn the volume up (leaving the S-XBS on 10) and you'll begin to hear the midbass distort at around volume 3. I don't know how exactly but it's got something to do with the internal design. It's as if the amp has a weak spot near the midbass frequencies or something.

quote:

Originally posted by Echoes:
This Panasonic uses a quad-amp design, each speaker has its own amp. It has a strong amp for the mid-woofers (about 6 watts per channel) and a smaller one for the tweeters (2 watts or something). They both run with the same voltage but the current of the bass amp is higher due to lower impedance.

This bi-amping design has advantages over conventional amping when the box is pumping near full volume as the highs still come clear while the bass is at its limit. A stronger (bridge) amp with a simple crossover would also do a good job in those


The listing on the back should be near the jacks where you can connect external speakers.

6 watts per channel? Is that high, average, or low for a boombox?

It's a guess. And it's high.

Boomboxes run on batteries. A set of D-cells can, depending on their quality and freshness, deliver less than 2 amps continously. The voltage breaks down when the woofers do their thing. You can see that when power LEDs dim etc. and you hear the sound distort sooner than on AC.

Often, boomboxes that use like 8 D-cells (12V) run with more (say 16V idle) when AC is connected to have more output power at home (and in the store). The Kaboom is a good example. No D-cell can deliver the 5 amps this boombox consumes. So power output on batteries is limited.


With a set of 10 D-cells and standard amp design (no digital), i don't think more than 12 watts RMS is possible.

quote:

Originally posted by Panabox:
The distortion of the midbass, I've noticed, follows the same characteristics whether I'm listening via the headphones or the unit's speakers themselves...

Well, that's weird. I'm all out of suggestions...

Does anyone here have a bass CD with various freq. and own an Rx-dt680 to see what I'm talking about?

Calling all electrical engineers and technicians: Is it possible for an amplifer to have the power and the ability to reproduce the lower more powerhungry low bass notes more cleanly than it does the less powerhungry higher bass notes? If so how?

quote:

With a set of 10 D-cells and standard amp design (no digital), i don't think more than 12 watts RMS is possible.

Didn't Panasonic's c300 have 30watts RMS while still running on batteries? I remember reading this somewhere on an antique radio site somewhere.

I think the c300 is about 15 watts per side RMS. I have the service docs--if you are interested I can look up the IC chip number.

I too have heard various things about the c300's amps. Including that the circuit contained a step-up converter to increase the voltage to the amps. Nope--direct connection to the batteries (or AC transformer).

quote:

Originally posted by analogboi:
I think the c300 is about 15 watts per side RMS. I have the service docs--if you are interested I can look up the IC chip number.

I too have heard various things about the c300's amps. Including that the circuit contained a step-up converter to increase the voltage to the amps. Nope--direct connection to the batteries (or AC transformer).

Thanks for that! At some point, I will probably take you up on that offer. But currently I'm trying to understanding the basics of science and sound. In general, is it possible for an amp to cleanly produce lower bass notes while at the same time distorting the higher bass notes? If so what would cause this? Because unfortunately this is exactly what the DT-680 does and it dosen't make any sense to me. It's the one blemish on this otherwise spotless bbx. Thanks in advance!

You can get 2x15watts from a 15 volt supply with a good BTL design, but your average D-cell can't deliver the required current of 4 amps for a longer time.

Panabox, that sounds like a damaged speaker to me. Check the foam surrounds if present. Maybe it's even a problem in the equalizer or preamp section or the box is designed to sound like that.

I think what you are talking about is "intermodulation distortion" (I hope I got the spelling right).

Basically a woofer oscillating (vibrating) to a lower frequency will impose that lower frequency to some degree on the higher frequencies the woofer is also being asked to produce (at the same time). Generally, the longer the woofer "throw," and the lower the natural woofer resonance frequency, the worse the condition is.

So, it is the speaker distorting the high notes, not the amp. Probably a quirk in this bbx's design and one you may have to live with.

I don't think the speaker is damaged, because you note the bass is cleanly produced.

I just read your note about this happening on headphones too. If the bass is sufficiently boosted, then you could get intermodulation distortion on headphones too.

It all depends on how sensitive your ears are to this type of distortion...and how high the bass is boosted (either natural to the recording being played, or thru the bbx's eq, or both).

Yup, i agree with you that the sound distort and it really spoils the otherwise excellent sound of the system. Mine unused for quite sometime now coz no parts for the power ic.I am sure the distortion comes from the circuit design. Maybe they have improved it on the latter model 690. But hands down, the cassette player is excllent. Ease of recording. If Panasonic release this unit with cd/mp3, i bet it will sell like hot cakes. I will be the fisrt to buy..

I got the 690, it sounds awesome. no distortion even at maximum. Someone did mention to me that bass sounds better on the 680, but I think it's because the 690 actually has "squakers(mid-range)" so the mid-range makes the bass sound less. The RX-DT75 has better bass then the 690 for sure.

quote:

Originally posted by peter griffin:
I got the 690, it sounds awesome. no distortion even at maximum. Someone did mention to me that bass sounds better on the 680, but I think it's because the 690 actually has "squakers(mid-range)" so the mid-range makes the bass sound less. The RX-DT75 has better bass then the 690 for sure.

Really? i never would have guessed that the DT75 had more bass than the DT690. So would you also say the DT75 (which also has "squackers") has more bass than the DT680?

quote:

Originally posted by Hoyhoysum:
Yup, i agree with you that the sound distort and it really spoils the otherwise excellent sound of the system. Mine unused for quite sometime now coz no parts for the power ic.I am sure the distortion comes from the circuit design. Maybe they have improved it on the latter model 690. But hands down, the cassette player is excllent. Ease of recording. If Panasonic release this unit with cd/mp3, i bet it will sell like hot cakes. I will be the fisrt to buy..

I agree. I too think that the distortion is due to the circuit design. My speakers are fine. All of the DT680's I've heard do this. I was hoping that some of the techs and engineers on this board could help pinpoint the culprit within this circuit design. Any engenieers or techs on here have a hypothesis?

quote:

Originally posted by Echoes: "...or preamp section or the box is designed to sound like that."

You may be on to something here "designed to sound like that". What qualities within a circuit design would be necessary to allow the mid bass to distort and not the low bass? And even more interesting, why would Panasonic opt to design their "Platinum Series" with the unbecomming flaw of distorted midbass?

The DT-680 at full volume distorts but in my opinion you can't hardly tell.

quote:

Originally posted by ford93:
The DT-680 at full volume distorts but in my opinion you can't hardly tell.

Depending on the freq. of the bass, you're right. But play a track like "Whoop there it is", at full volume, and it becomes a lot more noticeable. But play a track with good low and high bass, and not much mid bass, and the distortion is much less obvious. Play a track with a combination of all three frequencies of bass, and you're left being impressed and disappointed at the same time. I'm like "Why Panasonic did you allow this? Fix it! It's like having a lexus with lots of torque but hardly any horsepower argghhhh"

Hi-I thought "Sound is Round" wouldn't a square or oval (e.g.6/9) distort by in theory because it's geometric shape?
Do these square speaker distort under full throttle like more then the round speakers?
Just a theory I've heard and noticed to some degree myself.
I don't have a Panasonic boombox other than my single speaker boombox.Would like to get a really good one someday.
Have a great one-GB.

quote:

Originally posted by ghettoboom777:
Hi-I thought "Sound is Round" wouldn't a square or oval (e.g.6/9) distort by in theory because it's geometric shape?
Do these square speaker distort under full throttle like more then the round speakers?
Just a theory I've heard and noticed to some degree myself.
I don't have a Panasonic boombox other than my single speaker boombox.Would like to get a really good one someday.
Have a great one-GB.

Again I don't think it's the speakers in regards the DT-680's distortion. I honestly think it's in the circuitry. Because the speakers distort less with the lower freq which move the speaker more. Whereas the higher frq which move the speaker less cause most of the distortion. The speakers are doing's its job, it's the amp that's slacking.

I can't wait til oldskool does his review. He's so thorough and I always learn a lot.
Oldskool your knowledge on these boards is much appreciated!

quote:

Originally posted by Panabox:
I can't wait til oldskool does his review. He's so thorough and I always learn a lot.
Oldskool your knowledge on these boards is much appreciated!

Thank You! And like I said, one more week and I'll have more time on my hands after some changes in our household take place.

Okay, so I've been playing my Dt-680 for quite some time since I recently bought it off ebay and I've noticed that the sound has actually improved. It distorts the midbass a lot less. Maybe I just needed to play it a lot to get the internals un-idled or something. I remeber someone on here saying that one of the best things that you can do is to play it a lot.
I must say, that this DT-680 has got to be the best sounding box on the market. I think it has more bass than the kaboom. It's deeper if you ask me. But what's also simply awesome about this box besides the features is how the Eq seems to handle the different settings quite well, even at loud volume. The S-XBS is no joke! It has a nice warm sound, and does an excellent job at keeping it's composure even when the volume is cranked. Panasonic hit a home-run with this box!!