RX-DT680 has more bass than other models.....? Let's see

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woodz93

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I was going to centralize my findings on my google site but hey... put it here, the content is protected to just the users here and I get another point for posting! (I might just move my RX-DT680 restore info here as well)...

So anyways, I read this forum and stereo2go and I get a majority saying that the DT680 has 'most' bass of the RX-CT and RX-DT series... so I decided to do a little test here.

I have done this process for my HT setup, not to mention I had friends do something similar in car audio soundoffs back when I was younger. Still, it ain't a definitive guide. I could have missed something, or not done something right. Did this experiment to the best of my knowledge. Here goes!

Equipment Needed:
a)My laptop that is running a program called TrueRTA http://www.trueaudio.com, real time analyzer for tuning audio gear. The free version will do for this test.
b)The mic is from my Onkyo Integra 5.9, it comes with all the Onkyo/Integra units for auto calibrating your soundstage
c)RX-DT680



For the microphone, I had to go into windows and turn off mic boost and set its level to 50. In TrueRTA, I had to setup input to L channel only, and in 'Spectrum Analyzer' I chose 'hold peak' as this will result in the program reading only the highest output levels and not show a fluctuating graph. So in a silent (seriously... as in no ceiling fan running, most electronics off, windows closed...) room, running TrueRTA yielded the following curve (no other adjustments was made beyond plugging in the mic and fixing the boost)

Now to setup the test environment. There are two scenarios, I will explain each one:
1. Solid Ground
In this instance, we test 2ft away with the unit sitting right on the floor. Having it sit right on the floor introduces some things, but in a nutshell - putting a speaker in direct contact with solid dense ground without any decoupling of any sort can amplify sound! (maybe that's what some want...) The mic is isolated from the ground, as you probably listen to the unit with your ears toward it and not your ears touching the ground...

2. Isolated Ground
This scenario is identical to the previous one, except the RX-DT680 is now placed on a damping material (a blanket). Simulates putting your box on grass or other surface that will absorb a good chunk of the energy from the speakers.


3. Test Source
a. Downloaded a pink noise mp3 file (VBR, 13MB) and burned it to CD. http://www.archive.org/details/TenMinutesOfWhiteNoisePinkNoiseAndBrownianNoise
Pink Noise is audio recorded within the range of 20-20KHz (simple explanation)
b. using the unit, recorded the pink noise onto a cassette (Fuji DR90 Normal Bias). WHY? Simple - doing this in theory will record the pink noise at the frequency range of the heads within the unit, so we can get a feel of the frequency response of the tape heads.

Testing Procedure
IMPORTANT: S-XBS setting to 0, equalizer settings are FLAT.
a)For the CD, I pressed play, hit 'Go' in TrueRTA, and ramped the volume from 0 to 2.5 max, held it for 20 sec.
b)For the cassette, I pressed play, then in TrueRTA pressed 'Go' (avoids registering the clicking of the tape mechanism), and ramped the volume from 0 to 2.5 max, held it for 20 sec.

I did both these tests for each scenario, for a total of 4 tests.

Results (Solid Ground)
CD:

Cassette:


Results (Isolated Ground)
CD:

Cassette:

Conclusion
Midrange performance was better when you put the unit straight on the ground. Then again, I think most boomboxes back in the day were positioned that way. Notice the dropoff in midrange performance when you isolate the box. As far as the high end response, I didn't tweak that part that much, pretty much most mics I plugged into the soundcard of the laptop cut off at around the same point, but if you follow the existing curve before the sudden dropoff you can see that the CD has better high end response than the cassette (duh). For the cassette, the dropoff is around the 10KHz mark.

In all the charts above, we see that there is a peak that occurs around 120Hz.
All things being equal(that is, if your boombox amplifier is still ok, your model has 4x4PDS, S-XBS, and is rated 30W in the Platinum Collection Catalog), the better bass on the 680 is due to, not surprisingly, the speakers. The peak also demonstrates that the speaker enclosure (bass reflex) is tuned to resonate around that given frequency (Note:The mic graph without any noise shows the sound level go up around the same point; so it appears there was some resonance from the room or mic or both, that occurred in that range. Nonetheless, the test graphs shows the bass response increasing at around 250Hz, which means that the tuned frequency of the box may have peaked at around 120Hz or lower..)..

It is possible that the tweeter on the 690 ruined the setup, as the port on the 690 is skewed compared to the port on the 680 (bass reflex enclosures are finicky about ports, them being too short/long/elongated/misplaced can have adverse or positive effect on bass output of a given speaker.)
See pictures to compare the ports (the pics aren't mine, just using to illustrate the difference in ports):

Assuming the speakers are the same, then internally the volume should be the same as well as the port cubic space, which it appears isn't quite true, as the 690's port is bigger than the 680.


So perhaps if you ran the speakers on the DT680 on the 690 you would get the same result, and again, all things equal, the other models sharing the same speakers as the 680 will, for the most part, sound just as good as the DT680..

I hope that sheds light on things, and again... this isn't a definitive test! Trust your ears - if they are happy, then so is the listener :-D
 
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Fatdog

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That's really cool, woodz. Do you have additional boomboxes to compare graphs with?
 

woodz93

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Fatdog said:
That's really cool, woodz. Do you have additional boomboxes to compare graphs with?
I don't :sadno: I figured I outline the process so others can try it out. One thing that differentiates the 680 from the 690 is the speakers and that is how I came to my conclusion. :-) Some love their CS780 or CT990 and they have the same speakers the 680 does.
 

woodz93

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Terry said:
Excellent work woodz93.

All I know is that my 680 kicks some serious (B)ass when it comes to comparing it with my other boxes. Every collector should have one.
:agree: I think my wife was going to get me a Sony MHC EC909iP until she found out I was online a lot trying to find a RX-DT680.. I'm glad I got it, there is room to tinker with it and IMHO, it more than holds its own against most of today's limited market of boomboxes. You can get sound rivaling a shelf system with the portability of a boombox :w00t: Just trying now to keep it alive for as long as I can...
 

panabox1

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woodz93 said:
So perhaps if you ran the speakers on the DT680 on the 690 you would get the same result, and again, all things equal, the other models sharing the same speakers as the 680 will, for the most part, sound just as good as the DT680..

I hope that sheds light on things, and again... this isn't a definitive test! Trust your ears - if they are happy, then so is the listener :-D
I tried putting my dt680 speakers on my dt690. Still the dt680 sounded better than the 690 in the bass department. Somehow the electronics in the dt690 just fail to reproduce the lows like the dt680 does regardless of which speakers and despite the fact that the dt690 is rated at 20watts more. The dt680 is just a better, bassier sounding box than the dt690. I wish someone could dissect the two to explain why/ how this is the case. One thing I noticed is that the dt680 goes down to 100hz on the eq slider in addition to the SXBS control whereas the dt690 only goes down to 330hz on the slider in addition to its SXBS control. So that may account for the dt680's extra depth in the bass department too. I still can't figure out the extra 20watts tho. .
 

woodz93

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panabox1 said:
woodz93 said:
So perhaps if you ran the speakers on the DT680 on the 690 you would get the same result, and again, all things equal, the other models sharing the same speakers as the 680 will, for the most part, sound just as good as the DT680..

I hope that sheds light on things, and again... this isn't a definitive test! Trust your ears - if they are happy, then so is the listener :-D
I tried putting my dt680 speakers on my dt690. Still the dt680 sounded better than the 690 in the bass department. Somehow the electronics in the dt690 just fail to reproduce the lows like the dt680 does regardless of which speakers and despite the fact that the dt690 is rated at 20watts more. The dt680 is just a better, bassier sounding box than the dt690. I wish someone could dissect the two to explain why/ how this is the case. One thing I noticed is that the dt680 goes down to 100hz on the eq slider in addition to the SXBS control whereas the dt690 only goes down to 330hz on the slider in addition to its SXBS control. So that may account for the dt680's extra depth in the bass department too. I still can't figure out the extra 20watts tho. .
I see that this topic had some discussion on stereo2go (are you Panabox there?), and for myself hearing everyone say that the dt680 has more bass had a say in which unit i wanted to get. Like you, I am wanting to find an answer to this discrepancy, so with your observations combined with mines let's see what we can figure out. :-)

As far as watt rating, I think for now we can just assume it is for powering the midrange/tweeter combination. I will leave out power in this equation as we are trying to figure out sound quality. Bass takes a lot to reproduce, and judging from the performance of the dt680 we can deduce that power definitely isn't lacking, perhaps the Panasonic people decided to throw in a few more watts to match the tweeter they added...

I had no idea that the lowest slider was centered at 330 Hz. This is a critical observation to coming to a conclusion. If you can (don't want to be bossin' anyone around), can you test this scenario:

a. dt690, left side connected to a dt680 speaker
b. dt680, right side connected to a dt680 speaker

now with both units equalizers flat, s-xbs at 0, play a tune that you love to hear on the dt680 on both units one at a time, first with the 690 ('hear the rest, then hear the best' theory), then the 680.

If my hunch is correct... they will both sound equally good. One more thing, again since you have both units on hand... do you think the elliptical port on the dt690 speakers have the same 'airspace' within it as the port on the dt-680 speakers?

Thanks a lot - boggles me too that the 'higher' model doesn't sound nearly as good as its counterparts :-/
 

panabox1

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woodz93 said:
panabox1 said:
woodz93 said:
So perhaps if you ran the speakers on the DT680 on the 690 you would get the same result, and again, all things equal, the other models sharing the same speakers as the 680 will, for the most part, sound just as good as the DT680..

I hope that sheds light on things, and again... this isn't a definitive test! Trust your ears - if they are happy, then so is the listener :-D
I tried putting my dt680 speakers on my dt690. Still the dt680 sounded better than the 690 in the bass department. Somehow the electronics in the dt690 just fail to reproduce the lows like the dt680 does regardless of which speakers and despite the fact that the dt690 is rated at 20watts more. The dt680 is just a better, bassier sounding box than the dt690. I wish someone could dissect the two to explain why/ how this is the case. One thing I noticed is that the dt680 goes down to 100hz on the eq slider in addition to the SXBS control whereas the dt690 only goes down to 330hz on the slider in addition to its SXBS control. So that may account for the dt680's extra depth in the bass department too. I still can't figure out the extra 20watts tho. .
I see that this topic had some discussion on stereo2go (are you Panabox there?), and for myself hearing everyone say that the dt680 has more bass had a say in which unit i wanted to get. Like you, I am wanting to find an answer to this discrepancy, so with your observations combined with mines let's see what we can figure out. :-)

As far as watt rating, I think for now we can just assume it is for powering the midrange/tweeter combination. I will leave out power in this equation as we are trying to figure out sound quality. Bass takes a lot to reproduce, and judging from the performance of the dt680 we can deduce that power definitely isn't lacking, perhaps the Panasonic people decided to throw in a few more watts to match the tweeter they added...

I had no idea that the lowest slider was centered at 330 Hz. This is a critical observation to coming to a conclusion. If you can (don't want to be bossin' anyone around), can you test this scenario:

a. dt690, left side connected to a dt680 speaker
b. dt680, right side connected to a dt680 speaker

now with both units equalizers flat, s-xbs at 0, play a tune that you love to hear on the dt680 on both units one at a time, first with the 690 ('hear the rest, then hear the best' theory), then the 680.

If my hunch is correct... they will both sound equally good. One more thing, again since you have both units on hand... do you think the elliptical port on the dt690 speakers have the same 'airspace' within it as the port on the dt-680 speakers?

Thanks a lot - boggles me too that the 'higher' model doesn't sound nearly as good as its counterparts :-/
Sorry man but I gave the dt690 away. But I do remember doing the test u suggested, the only difference was I had all the bass adjustments set to max instead of neutral and zero. In that test, the dt680 siide sounded, bassier and stealthier than the dt690 side. I did this test with both units and each time the dt680 speakers sounded better and deeper.
I think Panasonic did away with the 50hz adjustment the dt680's SXBS controlled while the dt690 's SXBS focused more around the 100hz whereas the dt680 already had an eq slider for that. Plus I think the dt680's speakers where more equipped to handle the dt680's added bass extension.

Also the dt690 cabinet was slightly smaller.
 

woodz93

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panabox1 said:
Sorry man but I gave the dt690 away. But I do remember doing the test u suggested, the only difference was I had all the bass adjustments set to max instead of neutral and zero. Int that test, the dt680. Side sounded, brassier and stealthier than the dt690 side. It did this test with both units and each time the dt680 speakers sounded better and deeper.
I think Panasonic did away with the 50hz adjustment the dt689's SXBS controlled while the dt690 's SXBS focused more around the 100hz whereas the dt680 already had an eq slider for.
Ok no probs. Shucks I should asked you to give the unit to me! :sad: At any rate, with what you have told me, I reviewed the graphs and this is probably the best I can come up for you (or anyone else who is wondering).

Conclusion (revised based on Panabox1's observations)
My conclusion now is two parts - Unit based and Speaker based. here goes:
Speakers:
(see illustrations in first post)
As I had highlighted, the tuned frequency of the RX-DT680 is centered around 120Hz or lower. This means the enclosure internal mass + port size are tuned to this range. The only way that the DT-690 speaker could achieve this is with a port with identical port dimensions.. Looking at the images, suffice to say that the ports are not identical, but bigger on the DT-690. Consider the following article:

http://www.ehow.com/how_7829141_tune-bass-reflex-speakers.html

In a nutshell.... different port size, different tuned frequency. Judging from the look of the port on the DT690 it does appear the port is bigger and from most people's observation of lack of bass, that can be summed up as the tuned frequency of that enclosure having gone up into the midbass region, away from the 120Hz range..

OK, so we establish that the tuned frequency of the DT680 is in the neighborhood of 120Hz and lower... now the next part.

Unit:
(refer graphs in the first post)
Let's start with what the DT680 has going for it. The lowest equalizer is centered around 100Hz. This is big, as by doing so you can potentially add +10dB to the range where the speaker enclosure's boost is. Turn on the the S-XBS function, and we can see that the upward curve starting around 250Hz can indeed skyrocket to high levels in the range of 120Hz - 50Hz. Hence the enhanced bass response.

The DT690... let's say that the S-XBS function is still centered around 50Hz. The speakers do not already have a frequency tuned in the region of the lowest equalizer (330Hz). In fact, that is the second slider on the DT680! So what would the frequency response of this box look like? I don't know, but what I do know is that the 120Hz boost provided by the enclosure specifications no longer exists. No 100Hz boost, coupled with an out of tune enclosure, gives the unit no bass advantage. So if the S-XBS is still around 50Hz, it don't matter - the speaker may as well reproduce those lows but the midrange / tweeter volume will overpower it, depending on where the boost has moved to.

Again, this is not definitive, it's based on my experience with car subwoofer enclosures as well as having friends who do this kind of stuff. Let me know if anyone has additional info I should consider :-)
 

Ghettoboom767

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I have a DT-680 and these are amazing!
If this indeed reproduces bass down to 100hz.then that's amazing
for a Boombox considering most home 12" woofer speaker systems
if they're good quality will reproduce down to around 25-30hz and
that's for good quality amps and speakers fir home use.
Yes 100 Hz is amazing for a battery powered Boombox!! :thumbsup: :yes: :-)
Cool test man! :yes:
 

woodz93

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Ghettoboom767 said:
I have a DT-680 and these are amazing!
If this indeed reproduces bass down to 100hz.then that's amazing
for a Boombox considering most home 12" woofer speaker systems
if they're good quality will reproduce down to around 25-30hz and
that's for good quality amps and speakers fir home use.
Yes 100 Hz is amazing for a battery powered Boombox!! :thumbsup: :yes: :-)
Cool test man! :yes:
100Hz is around the threshold for speakers this size, although I have been able to clip them on occasion. Try for example the song 'Rain' by Madonna. Turn up the XBS and the 100Hz. The speakers show distress at around 6-7 because of the rumbling bassline that starts off in the first few seconds of the song. This song makes the box work!

There are other things that could potentially make this bugger bump louder. I have been busy but I am contemplating adding damping material to the speaker enclosures and adding filling to the enclosures. Room placement I found is also very important - I haven't graphed it, but if you want to bump this loud n clear give it a couple inches behind it. Better yet, position it in the corner of the room, at listening level, with space behind and to the side of it. Flush up against the wall is a no-no for most speakers. I have it on top of the dresser, away from the wall by about that much inches. The other day I was bumping Mayer Hawthorne's 'The Walk' in the bedroom and a friend came over saying 'Turn down your home theatre system, geez!!' and was dumbfounded that it was just a 680 on a shelf in my room. Now I know what Panabox1 was talking about.... :w00t:
 

panabox1

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The 680 definitely gets down lower than 100hz. Thes boxes produces AWESOME low frequency sounds. To get the best sound download the EQu app on your iPhone or iPad and lplay it through your 680. Sounds great!! I have the lowest frequency on that app cranked to the max everything after that is set low. As a general rule the 32hz ( or what ever the lowest setting on a graphic equalizer) must always be twice as loud as the remaining frequencys. That deep rumbling bass sets the parameters for my soundstage.
 

TMR

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just an fyi.. i have both of these units.. and the RX-DT690 main woofers are 6 ohm as apposed to the RX-DT680 woofers which are 2.7 ohms.. therefore the RX-DT680 speakers should sound louder and should have a higher SPL rating.. the DT-690 tweeters are also 6 ohms while the DT-680 tweeters are 8 ohms.. just some usefull information..
 

woodz93

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TMR said:
just an fyi.. i have both of these units.. and the RX-DT690 main woofers are 6 ohm as apposed to the RX-DT680 woofers which are 2.7 ohms.. therefore the RX-DT680 speakers should sound louder and should have a higher SPL rating.. the DT-690 tweeters are also 6 ohms while the DT-680 tweeters are 8 ohms.. just some usefull information..
Yes, the impedance definitely plays a role here. I am still curious how the 690 would sound with the 680 speakers connected to it...
 

panabox1

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woodz93 said:
TMR said:
just an fyi.. i have both of these units.. and the RX-DT690 main woofers are 6 ohm as apposed to the RX-DT680 woofers which are 2.7 ohms.. therefore the RX-DT680 speakers should sound louder and should have a higher SPL rating.. the DT-690 tweeters are also 6 ohms while the DT-680 tweeters are 8 ohms.. just some usefull information..
Yes, the impedance definitely plays a role here. I am still curious how the 690 would sound with the 680 speakers connected to it...
I've tried it, and the 680 still sounds better. The 680 has a wider frequency response than the 690 whether the 690 has the 680 speakers or not. It hits far deeper notes that the 690 doesn't even try to hit. This is evident with or without computer measurements.
 

mellymelsr

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panabox1 said:
The 680 definitely gets down lower than 100hz. Thes boxes produces AWESOME low frequency sounds. To get the best sound download the EQu app on your iPhone or iPad and lplay it through your 680. Sounds great!! I have the lowest frequency on that app cranked to the max everything after that is set low. As a general rule the 32hz ( or what ever the lowest setting on a graphic equalizer) must always be twice as loud as the remaining frequencys. That deep rumbling bass sets the parameters for my soundstage.
...if you really want the best tailored sound an mp3 player can offer get a little Sansa Clip Zip and get the Rockbox download. I have never heard anything that even comes close to the awesome sound it produces...(I have an Ipod touch and Cowon J3 and it beats them both although the Cowon is very close)
 

woodz93

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panabox1 said:
woodz93 said:
TMR said:
just an fyi.. i have both of these units.. and the RX-DT690 main woofers are 6 ohm as apposed to the RX-DT680 woofers which are 2.7 ohms.. therefore the RX-DT680 speakers should sound louder and should have a higher SPL rating.. the DT-690 tweeters are also 6 ohms while the DT-680 tweeters are 8 ohms.. just some usefull information..
Yes, the impedance definitely plays a role here. I am still curious how the 690 would sound with the 680 speakers connected to it...
I've tried it, and the 680 still sounds better. The 680 has a wider frequency response than the 690 whether the 690 has the 680 speakers or not. It hits far deeper notes that the 690 doesn't even try to hit. This is evident with or without computer measurements.
Thanks for the input again :-) While it is true that lower impedance speakers have higher SPL, this is mainly due to the lower ohms drawing out more power from the amplifer. Additionally, Panabox1's results show that the equalizer settings on the 680 plays a big role here. I love how this unit sounds! And that sound just carries throughout the house (a friend thought it was my home theatre - try finding a boombox that can fool someone on that level :lol: )
 
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