48 replies to this topic

[SPLvrWAGON]

hello. just want to know your opions on buying a SMD dd1 Distortion Detector

[~Spyne~]

what for?

[SQXPRT]

price?

if it's more than a hundred dollars, then you're better off getting a pocket DSO.

[D34M0N.inc]

http://www.ebay.com...._Test_Equipment

Something like that ^

[TMM]

^^ What they said. DD1 is way overpriced. I didn't know you could get DSOs that cheap, for $66 you can't go wrong for this kind of thing

price?

if it's more than a hundred dollars, then you're better off getting a pocket DSO.

Last i checked they were asking $170 for it and shipping was over $100 to australia. Lol at the suckers who bought one.

Edited by TMM, 19 February 2012 - 03:39 PM.

[SPLvrWAGON]

i like its cheap but is it user friendly. has any 1 bought 1 or used 1 b4 ?

[TMM]

i like its cheap but is it user friendly. has any 1 bought 1 or used 1 b4 ?

Just like using any other oscilloscope (what everyone without a DD1 uses...).


at around 2:30 you can see him turn it up and get some clipping.

[089JAY]

Guy up here has a DD-1 and many people have recommended it, however, I would love to get hold of my own DD-1 and an SMD Amp Dyno.... Might look into that actually...

[aerosport]

Last i checked they were asking $170 for it and shipping was over $100 to australia. Lol at the suckers who bought one.

I guess I'm a sucker then.... I payed $140 and shipping was $17. I'm more than happy with the purchase and the results that came from it.

Just like using any other oscilloscope (what everyone without a DD1 uses...).

I don't agree. The DD1 was a lot easier to use and tell when clipping occured. The oscilloscope I am comparing the DD1 to is a TPI-440.

The way I see it, you buy this one product and your set for life for setting your gains pretty much perfect every time.

[Lunchbox.inc]

my issue, is that it will only telll you if your clipping at 40hz... it's great sfor your more "simple" setups, where if it's not clipping at 40hz, it's doubtful it will clip anywhere else... but for setups like mine, where the subs will rarely see anything as high as 40hz, it doesn't really help...

i am keen on getting one to have a play with however, i do think i could make use of one...

[TMM]

my issue, is that it will only telll you if your clipping at 40hz... it's great sfor your more "simple" setups, where if it's not clipping at 40hz, it's doubtful it will clip anywhere else... but for setups like mine, where the subs will rarely see anything as high as 40hz, it doesn't really help...

i am keen on getting one to have a play with however, i do think i could make use of one...

You wouldn't expect 25 or 30Hz to clip any more than 40Hz because the test tone is full amplitude - yes that means that a 30Hz full amplitude tone is not as loud as 40Hz full amplitude. For all intents and purposes you could set the amp gains at 1khz and it would still be perfect at 40Hz. edit: although that's null and void if you use any EQ or bass boost features.

From an engineering perspective i think i know why they have chosen 40Hz and 1Khz as the two settings - it probably fits perfectly with the DD1's sampling rate and FFT bin size and gives the best accuracy (edit: the DD1 is apparently analog, that would mean two seperate circuits for each frequency, pretty crude and would explain why it ONLY works at those freqs). From a functional perspective i can't see any reason for offering two seperate frequencies other than for people who are so lazy that they don't disable highpass/lowpass filtering while setting their gains.

Edited by TMM, 24 February 2012 - 05:47 AM.

[Lunchbox.inc]

well i personally wouldn't want to run 40hz thru my mids at full noise, lol, but in my instance, which obviously differs from most others, i have my crossovers set at 40hz, and if i could, lower... so a DD1 doesn't help me at all... hahaha

but i do see what your saying, it just doesn't suit "all" setups, alot of burp cars couldn't play 40hz full noise to find their clipping point... just stuff like that...

but what SMD HAS done, is creat an awesome little device that suits 90% of daily installs out there, only issue is the cost, the buy price is decent enough, it's getting it out here than can pose an issue, not sure if they've fixed the shipping on the website...

[TMM]

Drivers can be substituted with resistor dummy loads to set gains, though I can't imagine a multiple thousand watt dummy load would be cheap to build lol - about $5-20 per 100Watt resistor. Could be a good investment for serious SPL competitors though.
If you wanted to put a very specific amount of power to your subs for a burp (say you have a 4000W amp but your sub will only take a 2500W burp) then a dummy load would be the only way to set the gains properly. DD1 would be useless for that, you'd want an oscope so you can calculate the output power.

BigDWiz on youtube benchmarks amps with a resistor load and an oscope. This video gives a good insight into how that works:


He also has a video about the DD1, and as you can see it's pretty much redundant if you have an oscope..


You can set up gains with the amp unloaded - results may vary, it's generally ok on lower powered amps where the limitation is the voltage rail inside the amp. Probably not the best idea for high powered setups where voltage droop is a real issue. In all of Steve Meades videos he sets up amps unloaded with a DD1. I don't really agree with this since his target market is people with ground pounders... He also uses a -10dB tone (on recommendation from Rockford Fosgate) to set the gains on sub amps which is completely wrong and will cause up to 10dB of clipping (A LOT) when the headunit is at full volume. The bass lines in modern recordings are around -1dB peak, so a 0dB tone should be used to set sub amp gains. For mids that are highpassed above 100Hz you can push it out to about -10dB, and -15 or -20dB for tweeters. Clipping isn't very audible in subs, so he probably doesn't realise what he is doing (that and he is big headed and won't accept that his methodology is wrong). I always get the feeling when watching SMD videos that he doesn't really understand the science behind what is going on.

Remember amplifiers don't care for the frequency you are playing. All that setting the gains is doing is making sure that maximum voltage out of the headunit equals maximum voltage out of the amp, not any more, not any less. The only reason you play a test tone to set the gains is so that you (or a device such as a DD1) can 'see' the clipping on the waveform. So you could still use a DD1/40Hz tone to set your gains when low passing below 40Hz. You'd simply need to set your amp to fullpass or raise the crossover point so 40Hz is unfiltered, set the gain, then set the crossover point back to whatever you desire. You could do the same with an amp driving tweeters - disable any highpass, set the gain with the 40Hz tone, and then enable the highpass and plug your tweeters back in.

Edited by TMM, 20 February 2012 - 03:39 AM.

[TMM]

http://www.mobilesou...oming-soon-998/

Good to see others share my thoughts on the DD1.

I've actually been brewing up my own Arduino based Distortion Detector / Amp Dyno. It's fully digital, works for any frequency (although is more accurate at certain frequencies due to hardware limitation), measures all harmonics and noise, not just 3rd order. The Arduino hardware is quite limiting for this kind of thing in terms of the inbuilt 10-bit Analog to digital converter, and 2k RAM. however as a proof of concept it works. With a 16bit ADC and about 32k RAM it would be almost dead accurate.

As it stands i could just put it in an enclosure with a few LEDs instead of a display, work out some auto-ranging circuitry and it would be a DD1. Total cost about $30. If made commerically it would be half that. Presumably the DD1 costs about the same to manufacture - now you know how much mark up there is.

I think something like this could be done under $100ea with graphical LCD and all, but I don't have the hardware know how or financial backing to get a project like this off the ground. Even if i did, i wouldn't bother manufacturing it because i think the market is too niche for something like that.




I've bought one of those Pocket DSO's off ebay and it's a very impressive piece of kit for $65. Just waiting on 8x 4ohm 100Watt resistors (bought 10 off ebay for $30) and i'll be tuning my gains with reasonable accuracy for <$100.

Edited by TMM, 24 February 2012 - 05:48 AM.

[Big_Valven]

$169 for a product with $15-$30 of parts is actually quite normal, and in a niche environment I find it disheartening for people to complain about that. People regularly spend $500+ on devices with <$30 of parts and think nothing of it.

[TMM]

Of course the price has to factor in R&D, however i honestly believe that is an incredibly small margin in this case. R&D would not be more than 1 week for a team of a few people to get a working prototype, plus a few weeks to sort out aesthetics. Compare that to a product like the DSO Nano and look at how much that sells for!
Props to them for finding a product to fill a market that was previously non existant, however i think the DD1 will be short lived at that price. 1st person to get a competing product to market will see that slashed in half.

Even as it stands, $200 will get you a nice Velleman scope like in the above videos with functionality and uses far exceeding that of a DD1.

Edited by TMM, 24 February 2012 - 06:23 PM.

[xMplar]

i have the DD1 and teh Xover calibrator and have a amp dyno coming as soon as they are ready and personally it is so simple a monky could do it put the CD in press play press a button adjust doner repeat same goes for the xiver calibrator even for low system that wont ever see 40hs its perfect as you getting the amps clip point at low and high frequwencys cause you have the frequecy of the subsonic wide opnen its fool proof and as close to bang on as you can get for normal ppl who arent as versed in electronic gadgets as most it perfect hell even if you are its perfect and bang on the money is nothng when it makes a 2hr job take 20mins
Ren
xMplar

[SPLvrWAGON]

sorry for the late reply i couldent use my comp untill i f***en formated it blah blah blah.... trojans n crap !!!!!
any way very interesting stuff being said
what i make of it and correct me if im wrong is that the dd1 is good for systems that hits under 40hz, is quick and simple to use but is way to expensive.
and the dso is great for the price it does pretty much every thing but takes time to learn and tune your system!

[bunny]

sorry to dig up a old thread. Is there somewhere that could teach you how to use a dso to tune your system, I was interested in the dd1 but after hearing people talk down about it I'm not sure. if not is there anyone or anywhere in qld that could tune it for me? I would prefer proper set-up not the turn until distort then turn back a bit I can do that myself.

[barcode]

where are you in qld?

[SPLvrWAGON]

ive bought a dso its pretty tricky at 1st but simple once you know how to.
thing i dont know is, what tones i should play through the system !
and i clamped the probes on the rca cables coming from the head unit and tried to get a clipping signal from the head unit but i can turn it up to the max volume with out it clipping ! do all head units clip ?

Edited by SPLvrWAGON, 09 March 2012 - 04:49 PM.

[bunny]

where are you in qld?

i'm in ipswich so anywhere round brisbane

ive bought a dso its pretty tricky at 1st but simple once you know how to.
thing i dont know is, what tones i should play through the system !
and i clamped the probes on the rca cables coming from the head unit and tried to get a clipping signal from the head unit but i can turn it up to the max volume with out it clipping ! do all head units clip ?

did you get that mini one that was linked in this thread, I don't want to spend heaps just in case i can't figure it out

[SPLvrWAGON]

yeah i bought a dso nano the same that was linked in the tread !!!

[SQXPRT]

Not all head units clip the output at max.

It depends on the tones you play also - some are -10dB, some are 0dB, some are already partly clipped in the recording.

for "SQ" music, it's normal to tune with -10dB tones, as they reflect approximate music level.
for pop/top 10 music tuning, 0dB tones are probably safer to tune with, as the music you play will be recorded "hot" close to 0dB max.

[SPLvrWAGON]

ive made tones using audacity but i dont know what db they are.
ive got a slighty more spl set up rather than sq. but i thumped my system daily. my box is tuned to 35hz
do i make 35hz and 1khz tone at 0db and look for a clipped signal from the head unit 1st ?

[SQXPRT]

1kHz won't help much with the sub bass.

Best to choose a frequency in the mid-part of each speaker's range.

i.e. 30Hz for sub,
200Hz for midbass
1kHz for midrange
10kHz for tweeters.

caution though - running the amp with 0dB sine waves to clipping can cause the smoke to come out.

[SPLvrWAGON]

oh crap so should i use plus 10 db then ?

[SQXPRT]

+10 would be already clipped at minimum volume!!

-10 is better

[SPLvrWAGON]

ok ill try a 30hz - 10db tone for the subs
and a 1khz for the mids ! do i do that also - 10 db ?

how do i create a tone on audacity at - 10 db ?

[TMM]

you aren't going to find the limit of your amp without clipping it lol, it won't make a difference if you supply the amp with a -10dB tone, it just means you are going to have to turn the gain knob more to get there because your signal is weak... And then that also means that when you play music any louder than -10db it's going to clip the crap out of the amp. So use a 0db tone to set your gains. The gain knob is just an attenuator - at maximum it lets the input signal pass through to the amp untouched, and when you turn it down it attenuates the input signal before it is amplified. Having the gain knob turned up doesn't mean the amp is working harder for a given power output.

First put the scope on the RCAs coming from your headunit (with probe set to 1x), play a 0db tone, turn it up and see if it clips. If it starts to clip at say volume 46 out of 50, then you know never to turn your headunit past 45.
Then, turn the gain on the amp all the way down, hook up the RCAs to the amp and put the scope on the output of the amp (with probe set to 10x). Play a 0db test tone at volume 45, and slowly turn up the gain on the amp until you see clipping, then back it off a bit until the signal is clean, and you're done.

Just use common sense when setting gains - stop the test tone as soon as you have the gain set at the correct level. As long as you aren't clipping the crap out of it or running it at max power for an extended period the magic smoke should stay inside Probably best to take that with a grain of salt though - there are probably amps out there that will self destruct before clipping, but i've never met one.

Also it's worth noting that not all amps produce text book accurate clipping. If any irregularity appears on the waveform then you are pushing the amp past it's limit and you need to back it off.

Edited by TMM, 19 March 2012 - 12:46 AM.