Looking For A Sub

eric bennett

I HAVE GOT MY SURROND SOUNDSYSTEM ALMOST COMPLETE . I AM LOOKING AT A POLK AUDIO SUD MODEL NUMBER PSW650. ANYBODY HAVE ONE OR ANY OTHER IDEAS.MY SYSTEM SPECS WILL BE BELOW.


RECEIVER:YAMAHA NATURAL SOUND RECEIVER MODEL NUMBER RX-V490.
FRONT SPEAKERS ARE : POLK AUDIO MODEL NUMBER RTA12C I THINK I CAN'T FIND ANY PICTURES ANYWHERE TO CHECK THESE ARE BIG SPEAKERS.
SURROND SPEAKERS ARE: POLK AUDIO S4 BOOKSELF SPEAKERS.


THANKS IN ADVANCE
ERIC BENNETT

MxStYlEpOlKmAn

id look at M&K - SVS and whoever else, POLK subs arnt that good so I have heard. M&K makes very accurate and loud subwoofers, that blend well with polk.

TroyD

If you can, I would look at the Paradigm line of subs. I'm a big fan of them.

I have a pair of RTA12C's and the Paradigm subs blend nicely with them.

Welcome aboard!

BDT

Dr. Spec

Polk makes OK subs, but not great. They lack deep bass extension and output, except for the infamous and now defunct PSW1200. I always thought they "sounded" good, though. I lived with twin PSW350s for a year and I liked them a lot. I never knew what I was missing below 35 Hz, though - until I got my SVS.

IMHO, SVS is the best value in subs going, and I am definitely not alone in this assessment. In terms of extension, flat FR, low THD, and SPL - SVS has NO PEER in each price class. Clean, uncolored, detailed, neutral, very deep, and will rearrange your hair when the source material calls for it. If you are the plug and play type, look at the PCi or the PC+ series.

HSU runs a very close second to SVS in terms of value for the performance. Look at the VTF-2 or the VTF-3.

The Velodyne HGS series is VERY good, but also very pricey. Ditto for the Klipsch RSW series. The Klipsch RSW series badly lacks in bottom octave (i.e., below 30 Hz) extension, but otherwise is just fabulous, especially for music.

Doc

goingganzo

or yyou can buld your self a sub saveings is alot but it takes a weekend to buld and you needsome tools if you buld a sono sub it is the eayset but has a lower WAF of you buld a box type are little more work but dont have the cilinder look to them and the size all depends on the driver you buy if you spend the same as you do on a store bought sub you will get so much in return the sono subs are so easy to make i bult one just waiting for my driver to come
165 for driver
35 for tube
got the mdf free
10 for paint
havent got the amp yet but any where from 110-330 if i get the 330 i get 2 chanels and 500 per chanel

eric bennett

cool thanks for the advise guys where could i look for some of those svs subs.

Dr. Spec

Originally posted by eric bennett
cool thanks for the advise guys where could i look for some of those svs subs.

www.svsubwoofers.com

Internet sales only, 45 day try-out - all you risk is shipping if you return it. SVS Customer Service is tops BAR NONE - replies to email average minutes and hours, not weeks or months.

Check out www.audioenvy.com (or something like that) for SVS owners in your area that you might be able to audtion.

Or post a question at www.hometheaterforum.com. There are thousands of thrilled SVS owners over at HTF. Ones in your area might be willing to accomodate you.

Also, HSU has a 30 day trial period. The best way to go, if you have the coin, is to order an SVS or HSU, and then buy a more well known brand locally and have a sub face-off in your own home.

BTW - ganzo has a point - DIY offers the biggest bang for the buck - you exchange sweat equity for dollars. But many people aren't into DIY, or need a sub RIGHT NOW and might dabble in DIY on the side at their leisure.

Doc

baron

just bought polk psw650 2weeks ago , after doing much
research
all I have to say is the 650 was only
surpassed by subs costing 3 times the price

joe logston

2 psw-650 even sound better that one. the psw-650 is more a musical sub than home theater sub. if set up right, two are harder to set up than one i use speaker connections from receiver to subs to the mains polk rt-7, and use a 15" sub as a lower octive placement sub out of the receivers lfe.

Lsi9

I am a proud owner of a HSU sub...consider it

Dr. Spec

Originally posted by Lsi9
I am a proud owner of a HSU sub...consider it

LSi9:

Would this be the TN1220 or the TN1225?

It's funny, HSU cylinder subs have kinda gotten lost in the SVS craze, but HSU really pioneered the commercial cylinder sub design after it took the DIY community by storm.

I think SVS has improved upon the commercial cylinder sub concept, but both brands are very excellent. It's funny, even Dr. Hsu admits his cylinder series of subs sounds better than his box subs strictly for music.

Regardless, you've got a very nice sub, there. What are you powering it with?

Doc

del44

I've got dual Paradigm PW2200 stacked. Excellent for either HT or music. One would be plenty for most rooms though. Depending on the size of the room. Plenty of bass, and goes really low.

Lsi9

I think its 1220 it is the more expen$ive model (the taller cylinder)...it goes down to a mean 19Hz and still high up on the db...it still surprises me sumtimes after 3 years with it...I run it with the 250 watt HSU outboard subwoofer amp...

eric bennett

HEY EVERYBODY THANKS FOR ALL THE INPUT. I HAVE DECIDED TO GO WITH THE SVS SUBS. I GOT IT NARROWED DOWN TO TWO MODELS BUT I'M NOT SURE WHICH ONE I WANT.
THE ROOM IS ONLY 15 FOOT X 16 FOOT.
THE MODELS ARE 16-46 PCI AND THE 20-39 PCI

THANKS ERIC

Dr. Spec

First, using CAPS is the equivalent of shouting on line - tone it down, OK? :-)

Only 15x16? Assuming an 8' ceiling, that's a damn big room - almost 2000 ft3. I'd look hard at the PC+ line for that size room if you like loud playback for HT. That's a lot of air to move. If you don't play it super loud, then the PCi will be great.

16 vs. 20? Tough call. The amount of subsonic bass on recent DVDs is increasing. If you want to make sure you're getting ALL the absolute deepest bass from your source material, go with the 16. Be aware though that the 16 gives up a few dB in max output compared to the 20 in exchange for the lower extension. In your big room, that might make a difference.

Also, the PC+ is tunable and you can tune a 20-39 to 16 or even 12 Hz in a matter of seconds with the supplied port blocker(s) and the adjustable SS filter. That's why I went with the 20-39PC+ - it's flexible, easy to set-up, and has mondo power - it's the best value in the entire line-up in my opinion.

Doc

MxStYlEpOlKmAn

Id Like to see the Top Of The Line M&K vs. Top Of The Line SVS
im about 70% positive M&K would blow it away!! AHAHHAHAHA! but thats my opinion...lol! *looks scared* plz ol plz dont flame me!!! HAAAAAAAAA!

Dr. Spec

M&K makes a great subwoofer - but it can't run toe to toe with the best (or even the second best) from SVS - not even close.

M&K's best:

MX-5000 MK II
Drivers: (2) 12"
Internal Amp: 400 watts RMS
MSRP $2,899


SVS' best:

Dual CS-Ultra Subwoofers
TC Sounds TV-12 woofers
Samson S1000 amp - 1,000 watts RMS
Better Cables Interconnect
MSRP $2,099

SVS' second best:

Dual 20-39PC+
TC Sounds dB-12 woofers
Indigo BASH amp - 1050 watts RMS
MSRP: $1,650

Twin Ultra's or twin 20-39PC+ will CRUSH the MX-5000 in all measurable performance parameters. No contest - the MX-5000 will take it's puny 400 watts and run and hide under the nearest rock.

Want something even better from SVS that is equal to nearly 4 Ultra's? Check this out:

http://www.hometheaterforum.com/htforum/showthread.php?s=&threadid=111058

SVS is TRULY the BASS AUTHORITY.

Doc

Dr. Spec

Still not convinced?

Even a $549 25-31PCi would run circles around your MX-90.

http://www.hometheaterhifi.com/volume_9_4/svs-25-31-pci-subwoofer-12-2002.html

Doc

MxStYlEpOlKmAn

Man wats dont hold water in a pale full of holes! 2000 dirty wats is nothing compared to 400 wats of clean power! Im not saying SVS is bad or nething, but you just sat there and compared DUAL SVS's to ONE M&K!!! WTF!
- Twin Ultra's or twin 20-39PC+ will CRUSH the MX-5000 in all measurable performance parameters. No contest - the MX-5000 will take it's puny 400 watts and run and hide under the nearest rock. -
WTF IS UP WIT THAT? Im still not convinced that ya'll think these subs are as awesome as yall say, ive heard TWIN mx-90's, they can be heard a block away, and can handle power, and volume, IE - they were played for 14 years at 120-30 db, id like to see those SVS's last that long at that volume! and besides the fact that M&K practically invented the subwoofer...LMAO!

- SVS is TRULY the BASS AUTHORITY. -

So you are saying, it can stand toe to toe with Wilson Audio? if u say yes, i will truly have to just buy a svs and sit here and listen to it, and if it cant even beat my mx90....im gonna sit here and laugh my ****$ off ALLLLLLLLLLLLLLLLLLL night long!

- it's puny 400 watts and run and hide under the nearest rock -
Man wats aint crap, my MX-90 is only like 150 wats! that thing can EASILY fill up a 60 by 60 room at 1/2 volume! And if you dont think ive done this test...ur wrong, i have had to be a dj and i used my subwoofer in a 50 by 50 - to 60 by 60 room, and by far the fact....it was toooooo loud! The mx-90 can be turned up all the way with no distortion, it can play full freq. with no distortion, and if u r going to point out that my driver blew, its probally the fact its so effin old it gave out!

- Even a $549 25-31PCi would run circles around your MX-90. -
that pos dont even hit below 20 hz for god sakes, and by far the fact its a effin down firing sub, all it can do mostly is shake the effin floor and maybe the walls! The MX-90 goes to 10 hz, weighs 80 pounds, 150 wat amp fc aproved, with top quality drivers. I would love to see that 550 dollar sub beat it. I am not saying to some it may sound better, infact to some people, my sub may suck! but im telling u, its one el of a awesome sub for 1400 bucks! and the new MX-125, is effin awesome. that new driver i just receiver is AWESOME! its 20% better in all respect in my opinion, its fuller, deeper, louder - its just better! Its more well built weighing 2-3 pounds more than the old one. Its just a awesome driver.

- SVS' best:

Dual CS-Ultra Subwoofers
TC Sounds TV-12 woofers
Samson S1000 amp - 1,000 watts RMS
Better Cables Interconnect
MSRP $2,099

SVS' second best:

Dual 20-39PC+
TC Sounds dB-12 woofers
Indigo BASH amp - 1050 watts RMS
MSRP: $1,650 -

If i read this right, does SVS need dual's to be good? is one not good enough? man, M&k dont have to recomend 2 to be awesome! AHA! id hate to see two M&k top of the lines paired together....woooooooo! thatd be awesome! SVS is probally a awesome subwoofer, but if it needs tot wo subwoofers to be awesome, then i wouldnt even think about buying it...its like saying he needs a buddy to win a fight! I mean cmon, how in the f*** can u compare 2 subwoofers to 1??? LOL! and by the way, M&K's top of the line is 400 wats, with a 700 wat headroom. I thought Id point that out, just incase you didnt no...

- Want something even better from SVS that is equal to nearly 4 Ultra's? Check this out: -
are you on crack? your gonna think that 4 m&k top of the lines cant beat one, 4 12 inch driver subwoofer? Man, with 4 M&K's you could put one on each side of the room, and have 8 DRIVERS! with a total of 1600 wats, with a 2800 wat headroom wattage, all fc aproved power, all clean wats, no distortion! ANd your telling me ONE sub could beat that? I bet that thing is awesome, but there is no F***IN WAY!

- Still not convinced? -
not really

- Even a $549 25-31PCi would run circles around your MX-90. -
im still laughing.....LMAO!

-MXstyler-4-LIFE-

RuSsMaN

Dude, I don't want to begin to pick that post apart.

One tip, if you are going to rant, get your facts straight first.

Cheers,
Rooster

MxStYlEpOlKmAn

point em out, i wanna no how im wrong...and what im wrong about.....set me straight man, im 13 - i need guidance, guide me away, im all fired up....set my torch, i wanna be corrected

MxStYlEpOlKmAn

ight, i just looked over my post, and all the facts that i listed, that i take as facts - I can back up, there might be things that u took as facts, that i didnt post as a fact...but tell me what im wrong about, and we'll see if u took a quote or opinion as a fact..

MxStYlEpOlKmAn

facts I posted -
M&k invented the subwoofer, well they might not have completely invented it but: In fact, M&K launched the audio industry into the subwoofer era back in 1974. Since then, M&K Subwoofers have delivered the deepest, tightest, and most powerful low frequency reproduction available. - Mksound.com, subwoofer catigory

MX-500 400 wat, 700 plus headroom:
The MX-5000THX Mark II uses M&K's new Active Balanced Push-Pull Dual Drive Amplifier, with the new Headroom Maximizer IV, delivering a very conservative 400+ watts continuous RMS. A high-current power supply and massive oversized transformer give it tremendous reserve energy storage for dynamic headroom well over 700 watts! - M&K sound, more info on MX-5000

The best of SVS i guess:
the specs, on it i see are 4 - 12 inch drivers, dont no freq spons, needs a 5 kilo amp? are those svs subs not powered or something? or do they come with a 5 kilo amp?
MX-500, dual 12's, 400 wat amp, with a 700 wat headroom fc approved power, well below 20 hz....and u say 4 cant beat one of those? ok...

if your taking that I said SVS had 2000 dirty wats, i never said that, i technically quoted a saying, ie: 100 dirty wats is no better than 10 clean wats, ie: if the first wat sucks, why continue? - im just pointing out wats dont matter

I dont need a fact or an opinion to even think that a SVS could beat a Wilson Audio....thats almost kinda funny.

ight, i see one fact i did say that is false, i read the specs and didnt read all about that pci or whatever it is, it does hit below 20 hz, im so sorry...:rolleyes:

water cant be held in a pale full of holes, and i hope i dont have to restate that...lol

thats all the facts that i posted, and i found one that was false, and all the rest, i have done or have heard or have tested, by either me or my dad, and it all comes down to being true, i dont see nemore i need to back up, point out nemore

RuSsMaN

I refer you to my previous post cochise.

Jensen and Bozak were making subs before you were an itch in your daddy's pants. M&K invented nothing. NOTHING.

MX whatever, what, are you quoting stats from a brochure? The entry level SVS are passive, and with proper amplification, for eg, Samson amps, they can be driven properly. No one is bashing your sub, please don't get wrapped up around the axle over it.

What does Wilson Audio have to do with anything posted here? Do you know how much a Wilson sub costs? Do you know anything about them? Hate to say it like this but 'I do'.

Watts DO matter, I dare you to show me a 10 watt powered sub that can hold its own. You CAN'T do it, why? Because it does not exist.

Try not to use other members 'quotes' as your proof. Samson power is clean power, period. I'm not stating that other amps would not fair well, they might. However, Samson is a GREAT choice. What Samson models have you had experience with?

Water, holes, 5 kilos, etc etc. Please rationalize your thoughts and get back to us. Like I said, if you are going to rant (nothing wrong with a good rant), please make some sort of sense when doing so.

Cheers,
Rooster

130 db?, Can I get a PUH-LEASE.

19ram98

Mx, Are you a M&M, oops, M&K salesman? The only other time I have heard such emphatic spewing of that dynamic power b.s. was when I made the mistake of talking to a salesman at CC.

MxStYlEpOlKmAn

Originally posted by 19ram98
Mx, Are you a M&M, oops, M&K salesman? The only other time I have heard such emphatic spewing of that dynamic power b.s. was when I made the mistake of talking to a salesman at CC.

umm, i need atleast 5 more years of age before i could even think of working there......and by the way bub, i copied and pasted that off M&K's site...maybe thats y it sounds like a M&K salesman....:rolleyes:

i was posting stats from whatever link i was given by doc

he said svs was the ultimate in bass or whatever, in that case - it can beat all, statements are nothing - yes i know wilson audio's are very expensive, around 50,00 - 70,000 a speaker, i know they are the BEST in the world.

first off, i never said there was even a 10 wat powered sub, second off, i am saying u can look at wats in ne way. but let me put it this way, id agree with the wat comparison that doc did, if M&K didnt have nothing but 'clean' wats ( i wish i could sleep, but i slept all day....:eek: ....*yawn*

again, i NEVER said ne amps or wats were distorted or dirty, i am cleary going back to the first thing above...i was only talking about how doc was saying SVS was better because of power...ooooo

5 kilowats man, that 4- 12 inch driver svs sub that i was posted to a link, it had a 5 kilowat amp on it or whatever, thats what im talking about....and about the water thing....ahahahah

wats means nothing to me newayz, now i know subwoofers alot of power to be driven loud and right, but in all respects, wats hold no water on which is better.

130 db, ight dont get me wrong, but if u play ur speakers around...lets see here 100-110 db by them selves, and im talking about Klipsch Chorus 1989 models, which by all respects CAN PLAY that loud, and you can not even tell me that the subwoofer can be drained out by speakers, and all respects these are duals. Not singles...since we are talking about dual SVS's...;) , im talking about DUAL M&K's, which together with speakers being played around 100 db a little more, that the subwoofer(s) reach a db rating together of 110-120 db....correct me if im wrong, there are NO ways in reality that a subwoofer can be out played by speakers, unless u have a real trashy sub wit kick arse speakers.....theres no way!

and if u insist, Puh-lease, and a THA-ank you

also, common sense - is the most un-common thing in the world, and i am by far common...

PS: I know this has no point and is probally a waste of time and will start a war! LOL!, but if I am thinking of Jensen of today and Bazooka (?) of today, then i wouldnt even consider that a speaker company....they are both lame-****$ excuse for both a subwoofer and a speaker, the old jensen was good so i hear, but i said they *invented* the subwoofer, i didnt say they tried to make one....lol, i just had to say that - whether they invented it or not man, that launched the era....aha...sorry buts its 1:40 in the morning and im like....wide awake...

-Try not to use other members 'quotes' as your proof.-
I NEVER USED NO EFFIN QUOTES AS PROOF TO NETHING! all i said, if your going to compare wats to something, atleast do it reasonably, 400 clean wats, to 2000 clean wats, i mean its really the same thing, depends on if your gonna use it, i mean i could never picture myself using 2000-5000 wats on nething! LOL! im just saying, doc's comparison by wats holds no ground, it makes either subwoofer no better in the other, its technically like saying if u have 100 dirty wats, it makes it better than 10 clean wats....ya know what i mean now?

-Samson power is clean power, period. I'm not stating that other amps would not fair well, they might. However, Samson is a GREAT choice. What Samson models have you had experience with?-
I bet they are. Im not stating that other amps wont either man! i havnt listened to a samson amp, and besides the fact in my own personal oppinion. I would never buy a passive subwoofer. Period. You know why? and this makes perfect sense to man. If your gonna buy a passive sub with a seperate amp, your pretty much gonna pay twice as much, especially if you get those clean samson amps. If you just skip all that trouble and get a powered one man, it skips the time, hassle, and not to mention money. back to my original statement, i never said samson amps or ne other amps were bad sounding, or distorted, infact i never said nething sounded bad, i was just showing that doc's comparison of wats held no ground. When you read stuff, do you like read half way and think you know what i or others are going to say? because thats exactly what it seems like your doing man. i may not make perfect sense, by dang.

- Mx, Are you a M&M -
ummm....let me see here *takes a chunk out of arm*, id have to say if i was a M&M, id definetely be the crunchy kind, tastes kinda bone-y, i would of guessed that whoever made me put a body in their chocolate mixer, but in other words, hardy har har har!

- b.s. was when I made the mistake of talking to a salesman at CC -
man, according to cc employee's...HAHAHA! subwoofers make no difference! LOL! i went there about a year ago to get a jvc shelf system, and i asked the dude what the difference was between one with subwoofers and one without subs. he said, there was no difference at all, in fact they both sounded the same! LOL! isnt that bs or what?

MxStYlEpOlKmAn

and for s***s and giggles.....
The growling scrape of a contrabass, the visceral thump of a bass drum, or the roar of an explosion from the latest Hollywood blockbuster... Those sounds - more often felt than heard - add the final degree of realism and excitement to the listening experience. Wilson Audio introduces the WATCH Dog powered subwoofer - it's going to change the way you experience reproduced sound.

You may choose the WATCH Dog as a low frequency effects (LFE) speaker for the WATCH Home Theater System, or to dramatically extend the low frequency capability of a two-channel system. Best of all, in a combined home theater/two-channel setup, you can switch effortlessly between those two functions via the WATCH Dog's control module.

The same control panel offers adjustable crossover slope and frequency for both High and Low pass filters. In addition, room-induced colorations and standing waves can be minimized with the WATCH Dog's unique controls for phase and bass equalization. The WATCH Dog is powered by the RMD-400, a very high current 400-watt amplifier engineered by acclaimed audio designer Richard Marsh, and was created specifically to complement the front-firing, ultra long throw 12" driver.

For over two decades Wilson Audio has passionately designed and built audio products that truly redefine the art. Wilson Audio has set the standard for the ultimate in loudspeaker design with the X-1 Grand SLAMM, the MAXX, the WATT/Puppy, and the Cub. The same uncompromised approach in design, materials, and construction continues in the WATCH Dog.

We encourage you to audition the WATCH Dog to hear - and feel - the difference.

Port: Front Firing
Frequency Response: 20-30/150Hz Adjustable
Low Pass Filter: Level adjustable, switchable in/out; 12dB/octave or 18dB/octave
High Pass Filter: Switchable in/out; 6dB/out; or 12dB/octave
Phase: Continuosly variable from 0-180 degrees
EQ: Switchable in/out, +10dB boost to -10dB cut; variable Q from .2 to 2; variable frequency selector from 30 to 150Hz
Finish: Standard Wilsongloss finishes, Custom finishes available at additional cost


Amplifier

Power: 400 Watts
Input Impedance: 56 K ohms single ended, 4 K ohms balanced
Inputs: Balanced and single ended for Right, Left and Processor/LFE
Outputs: Balanced and single ended for Right, Left, High Pass filter outputs

whats that??? 400 wats??? wahh.....does the wilson need to hide too?

MxStYlEpOlKmAn

Originally posted by ATCVenom
[B/]

First, you use the words "fact" far too often. Have you personally done a side by side comparison of the SVS sub-woofer and the M&K? No? How about the flagships both companies have to offer? No? .... didnt think so.

Point is, specs are just that.... letters which leads one to a state of expectancy.
[/B]

ight, your right - havnt done a side by side comparison. Also, if doc gives specs, i can give specs, and i can compare them - just like doc. By the way, isnt SVS online only - well how in the heck am i gonna demo one? lol! im actually kinda scared to demo either of the flagships, heck id be scared to demo duals of them! LOL! my heart might end up being damaged...aha!

and by the way, i technically havnt even posted a fact other than ones i know. Common sense: 4 subwoofers can beat 1, unless you are gonna put 4 100 dollar sony's to a M&K or SVS. You put 4 M&K's to a SVS, you have so much more placement with 4, it'd be impossible to beat them. You could put one infront of you, behind you, and on both sides, which makes the bass sooooooooooo powerful! id be scared to be in that dang room. Common sense: you dont compare two subwoofers to one, but 2 on 2. Seem fair? I think so.

gidrah

The RTA 12s are some mighty fine speakers with quite a low end. If you haven't, I'd try spikes or stands and see if you can improve what is already there. If you have tried or do try and still feel you need a sub, you're gonna need a good one to get much improvement.

The DIY is a nice route. Ron-P (another member) did a sonotube style DIY that ran him under $400. There are also other DIY designs out there. I'll probably be doing a transmission-line sub in the future.
With the in-home trial and reputation the SVS are a good choice.


Mxsty..... The sub in the link only needs a 5Kw amp to drive to distortion. I'm sure much less could be used to drive it under normal conditions. That and the fact that 110dB will make you go deaf mighty fast and result in heart palpitations that will kill you make that a non-issue. The only issue is the fact that a speaker capable of handling such power and providing as much SPL will be less taxxed and thus distort less under normal conditions.

F1nut

Originally posted by MxStYlEpOlKmAn
point em out, i wanna no how im wrong...and what im wrong about.....set me straight man, im 13 - i need guidance, guide me away, im all fired up....set my torch, i wanna be corrected

I like this guy, he's got moxie!

Dr. Spec

God that was fun!

Every regular poster here knows I am normally reserved and stick to the facts and avoid comparos and brand bashing like the plague. It's just not cool.

But I couldn't resist!

MxStYlEpOlKmAn: Comparing brands and saying my dick is bigger than yours is a COMPLETE waste of time. I was yanking your chain and you fell for it hook line and sinker.

The ONLY way to settle any sub shootout is to have an INDEPENDENT, QUALIFIED reviewer test both of them in the same room under controlled conditions.

Doc