Another thought...Sub's yes here.

13

Comments

  • RuSsMaNRuSsMaN Posts: 17,995
    edited September 2003
    And to add Troy, a lot of these guys can hear a BIG difference between different SS amps, remember? So not only would they be running a different brand on their sub(s), but a probably a different class too (Class a-a/b vs d).

    Where should the gain be set? To your taste, or the way the recording was meant to be heard? How can you even determine the latter?

    To each his own, I'm not afflicted with gottaberightus like another member is, but I think from a purist standpoint - ie critical listening - adding a sub probably does more harm then good.

    Cheers,
    Rooster
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
  • VR3VR3 Posts: 23,371
    edited September 2003
    Since I am strictly 2 channel right now, and have been for almost a month. I feel I should comment as I agree with alot that has been said.

    I have heard many speakers, and the only speaker I have heard that did not need a subwoofer during music was indeed the Wilson Audio X-1. The X-1 had ungodly amounts of bass. Especially at higher levels. Were talking concert levels of chest pounding, your clothes are gonna leave you type bass. Truly awesome bass there.

    However, I have noticed with mine, my Dad's, and others - that most speakers (unless a subwoofer is built in) requires a subwoofer to really experience the music. I have not heard many full range speakers so far, the SRT would be one (but it had subwoofers built in).

    Anyways,
    I play my RTi70 on large, with the M&K running with it. I have the M&K crossed over at 65hz (which is where I like it, because at anything higher than that, I could tell where it was and the M&K was doing to much for my musical taste). But I run the M&K relatively hot, which for the M&K is about right on with the music. So I run it at about 70% on the volume knob, and 0db Subwoofer Gain on the receiver. Since my system is currently not plugged up to DVD Players or VCRs then this suits it fine and does not bottum out at all, or if it does - it does not bother me as I can not hear it.

    I will say this though, the RTi70 has killer amounts of bass for not having a subwoofer built in. I have turned them on alone, and if I had about 250 watts pushing them...anything above 40hz would easily satisfy me (as they do now, even with a 100).

    Some people though, enjoy their speakers without a subwoofer (mainly because they feel they are getting what they want out of their music (which is good and all) but I will say that most music I have heard, basically needs a subwoofer, some way somehow).

    Why do I say that? Well music is dynamic, I notice the midrange tightens up, becomes cleaner, more dynamic. The top end also becomes smoother. So really, unless you have killer amounts of power (this is my opinion) the bass needs to be backed up, some how.

    But then again, what do I know? I'm a kid, that is talking from what he has heard and plainly is speaking on opinion and that is all. So I will shut up now...
    - Not Tom

    Vr3Mods.com ///// Version3Audio.com

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • Loud & ClearLoud & Clear Posts: 1,538
    edited September 2003
    Troy and Russ have made some great points again on this issue, and I'm assuming this issue is strictly a two channel setup debate; there's no denying what a sub brings to home theater.

    Well, I'd like to add this: with some speakers, like my 55i's, the benefit of additional extension, and additional slam, isn't worth the sacrifice I feel you make in terms of the overall continuity of the musical picture; anything disjointed, or ill-timed gives me a strange look on my face; a puzzled, slight frown. Maybe there's a sub out there that can be made to completely disappear with them, but they'd have to do just that, and like Troy said (paraphrasing) "that ain't easy." Other speakers, like with my 35i's, I'm willing to sacrifice some of the overall continuity because they *require* additional extension and slam.

    I think a lot of this is about compromise, as well as perception and interpretation. I know what I like, and I trust that the same can be said for everyone else here.

    Two Channel Setup:

    Speakers: Wharfedale Opus 2-3
    Integrated Amp: Krell S-300i
    DAC: Arcam irDac
    Source: iMac
    Remote Control: iPad Mini

    3.2 Home Theater Setup:

    Fronts: Klipsch RP-160M
    Center: Klipsch RP-160M
    Subwoofer: SVS PB12NSD (X 2)
    AVR: Yamaha Aventage RX-A2030
    Blu Ray: Sony BDP-S790
    TV Source: DirecTV Genie
  • mantismantis Posts: 15,374
    edited September 2003
    LOOK,
    out of Mantis handbook,being RIGHT,and all that stupid crap is exactly that.Get over it.........

    I'm not about any of it.Actually I'm real tired of hearing it.Read my posts like anyone elses,OPNION.Thats what I bring.Audio and video for that matter is loaded with it.Agree?Lets all get over it.


    As far as why I started this thead is to get opnions of others and how they feel.Use one or not,it's something to think about.Getting a sub to match is golden.

    Troy did make some good points with matching.How hard is it to get the lower end to match????I personally think it's not as cridical as I once did.Over time experience pays off.Listening to differnet sub's with different speakers in differnet rooms teaches you alot.

    2 channel is what the orignal question was about.I know alot of you do it.As most of you know I'm a multichannel guy and have been for years.2 channel is very sadisfying and I believe adding the right sub with a given pair of speakers just adds that last bit of foundation.I own the Lsi15s and use them for 2 channel.I love them without a sub,but adding in sub's does change things.It seems to add weight.Remember correctly blending the sub so it is felt and not heard.Thats my goal.

    Right now I'm in full demo mode(like I'm not any other time but...)a sub is what I wanna bring home.REL is the standard(mine anyway not yours..opnion remember please)The Velodynes are really a hell of a sub comp[any and I'm digging in each and every day.They are truely musical but so far not better then REL.They do however have more output for theater and shaking the room abilities.No boom but force that hits you in the chest.I like it.

    The other thing I'm kicking around is using 2 different systems for music and theater.REL's are perfect for dual usage systems,but 2 channel by itself has a certain soft spot in my newly hearted heart.

    I really don't wanna argue with any of you,even Russ and Troy.I'd much rather talk about this.So for the record I was out of line with some of my comments and I apolize.

    Dan
    Dan
    My personal quest is to save to world of bad audio, one thread at a time.
  • madmaxmadmax Posts: 12,438
    edited September 2003
    Let me point out MY opinion in one more way. When you are listening you should be able to close your eyes and pretend you are someplace else listening to the performance. Now here is the hard part: can you be at a performance, close your eyes and pretend you are in your livingroom? Keep in mind I am not talking about being at a rock concert where everything is coming from a PA system. I am talking small venues where you are hearing each instrunent. For example, the bass guitar is coming from his cabinent, the lead is coming from his (I don't know, Marshall cab), the singer's sound is coming from his little stage monitor, and one example I like a lot, the B3 organ is coming from a few leslies sitting around the room. Oh yea, the drummer is sitting somewhere and you can tell where his different drums and cymbals are sitting and they sound live. Is this so hard? For me it was until I started really listening. Of course you have to hear a few small bands live as well. ...If you hear a stereo when you close your eyes and try to pretend, well, you have not made it there yet...
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • TroyDTroyD Posts: 12,638
    edited September 2003
    I'm feelin' ya there Chuck.....agree 100 percent.

    All I'm saying is that is a rather daunting task.

    BDT
    I plan for the future. - F1Nut
  • madmaxmadmax Posts: 12,438
    edited September 2003
    In my case, a pair of sda-srs, two manly amps, an age old luxman CD player, the right room and this or that interconnect and speaker cables. Not that BIG of a deal in my opinion. Yea, I went through a lot of equipment to get to that point but given e-bay pricing it all came around at about 3 grand. OK you could add the turntable and stands, magic brick and other useless stuff and add five times as much, but you don't have to... I am appalled at what a lot of people spend on their systems to get, well, SUBstandard performance. We all go through it but in the end you figure it out. At least I hope to.
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • TroyDTroyD Posts: 12,638
    edited September 2003
    Jeeze, Sean, don't get all Oprah on us. It's your rig, do what you want. That goes with out saying.

    I gotta ask though, do you keep a dictionary and thesarus handy when you post? Reading your posts is like reading the op-ed page of the New York Times. ;)

    BDT
    I plan for the future. - F1Nut
  • mantismantis Posts: 15,374
    edited September 2003
    ATC,
    when you get your system up and running,I'd like to read what you think the difference is when running a sub and not.

    Your going to like how REL can be setup.If it gives it to yeah,let me know.
    Dan
    My personal quest is to save to world of bad audio, one thread at a time.
  • faster100faster100 Posts: 6,247
    edited September 2003
    Here go's... to say what you like or me or someone else.. is like what ever! It doesnt really matter in the end, if you like a sub then use it.. I would guess someone saying they don't use one wouldnt change the way "you" feel.. So is their a right and wrong? sometimes, But not when it comes to speakers and subs or lack of one. matching is good, but not with everything.. so let each other live and learn and try, after all we all really dont know what people are trying and not posting about. They tend to post what people like to hear posts about.... what "everyone" else is into or likes or what is in, at the moment.

    I like asking questions and take some of the answers lightly.. some to heart, depends on the source.

    The whole Mantis, troy, Russ thing is typical club polk stuff and at times is tiresome and most times is funny and interesting to say the least.. everyone agree to disagree that you all don't like each other and move on, I certainly have tried to stay out of the fray as of late..


    on track again, I like a sub, most all the time.. sometimes i run it hot AND sometimes neutral.. although my house is getting rewired and my rig has been unhooked.. and yesterday i had just my mains running on large no sub, and it had quite a bit of bass.. i was surprised largely at the bass these 70's produced.. now was it below 25-35 htz? I don't know, i don't care, It sounded good.. how can you enjoy the music if you worry about what they are playing at? just enjoy i say..
    MY HT RIG:
    Sherwood p-965
    Sherwood sd871 dvd
    Rotel 1075 amp x5
    LSI15 mains
    LsiC center
    LSIfx surround backs
    Lsi7 side surrounds
    SVS pb12/plus2


    2 Channel Rig:

    nad 1020 Pre-amp
    Rotel 1080 stereo amp
    Polk sda 2B
    kenwood grunt Tuner
    realistic lab 450 TT
    Signal cable IC
  • Frank ZFrank Z Polk-a-dweeb Posts: 5,967
    edited September 2003
    #1) I owe everyone an apology for going off half cocked! I will do my best to not let it happen again!

    #2) Sorry to see Russ and Troy gettin the blame for my behavior. My fault not theirs. **** at me please, spare the innocent.

    #3) I'm finally going to take own advice and engage the ignore feature so I don't go stirrin' the pot again.

    Again, Sorry for the useless out bursts, perhaps I need a vacation.

    Please continue.
    9/11 - WE WILL NEVER FORGET!! (<---<<click)
    2005-06 Club Polk Football Pool Champion!! :D
  • TroyDTroyD Posts: 12,638
    edited September 2003
    Jeeze, what's with all you Oprah Windbag-watchin' mofos? El Christo, put down the Little Debbie snack cakes already.

    Frank, Russ, Me....Dan hates us all the same. WE don't have a receiver that cost as much as a good used Toyota but we DO have full surround rigs (although they aren't wired with Kimber 8tc) not to mention houses to put them in. ;)

    Have a beer, be happy, press on.

    BDT
    I plan for the future. - F1Nut
  • faster100faster100 Posts: 6,247
    edited September 2003
    so who else is oprah there Troy? LOL

    you guys all argue like ya married or something,
    MY HT RIG:
    Sherwood p-965
    Sherwood sd871 dvd
    Rotel 1075 amp x5
    LSI15 mains
    LsiC center
    LSIfx surround backs
    Lsi7 side surrounds
    SVS pb12/plus2


    2 Channel Rig:

    nad 1020 Pre-amp
    Rotel 1080 stereo amp
    Polk sda 2B
    kenwood grunt Tuner
    realistic lab 450 TT
    Signal cable IC
  • Frank ZFrank Z Polk-a-dweeb Posts: 5,967
    edited September 2003
    Just tryin' to do right.
    9/11 - WE WILL NEVER FORGET!! (<---<<click)
    2005-06 Club Polk Football Pool Champion!! :D
  • mantismantis Posts: 15,374
    edited September 2003
    Troy,

    let me try this thing..

    1)
    Frank, Russ, Me....Dan hates us all the same.
    Not true,I don't hate Frank.I would like to know what it is he has for me.You???You know why I don't like you.It has nothing to do with your gear.It's your attitude.You can be cool one minute and an **** the next.Russ........easy always half cocked.2 faced maybe....shame as I was starting to actually like Russ.We would talk off the forum and seem to get along just fine.But in here he wears a different shirt with me for whatever reason........
    You guys just can't let the past be the past.

    2)
    WE don't have a receiver that cost as much as a good used Toyota but we DO have full surround rigs (although they aren't wired with Kimber 8tc) not to mention houses to put them in.
    So why is this comment made Troy?Enjoy stabbing people when there down?Do you feel like a bigger man now Troy?My house...**** YOU DUDE.I'm going threw legal problems and every **** thing.LAST TIME STOP JOKING AROUND WITH MY HOUSE IT ISN'T **** FUNNY UNDERSTAND THAT?????????????????And why do you bring up my receiver.So what it costs what a good used car costs.All the speakers you own,I'm sure they all cost more then my receiver does.I can't figure out why that matters so much to you Troy.I can afford to own why the hell not?If I was into Carver then I would own that.
    The wire thing..use whatever wire makes you happy.So what I like Kimber Kable.My system is down right now due to the up coming move.When ever it comes.My family and myself are going threw a very tuff time with the builder and the Township.I can't seem to get this thing to work.I wanted to get out along time ago but the wife has her heart set on this house.

    Tired of talking with you Troy.I'm done with you.I won't be commenting on your posts anymore so hack all you want.I want nothing do to with you.That thing Frank talks about the Ignore feature,I 'm getting that in effect so we can avoid each other.

    Broken record here..........
    Dan
    My personal quest is to save to world of bad audio, one thread at a time.
  • TroyDTroyD Posts: 12,638
    edited September 2003
    Ten bucks says it isn't............

    Hmmmm, I thought the occupancy permits were a done deal? I dunno if three years of hassle is worth a spec house.

    Lemme think, I got 1175 in the mancave rig, wire and IC's included. In HT, I got 1825 in speakers, amps, receivers, sub. Pretty much everything but the TV. Might be a little more or a little less, just off the top of my head. I probably got another five or six hundred in other misc. gear I suppose.

    BDT
    I plan for the future. - F1Nut
  • Dr. SpecDr. Spec Posts: 3,780
    edited September 2003
    The two threads over at the sub section on that privately recorded Church Organ music really bring into focus one example of what we are talking about for music and the need (or lack thereof) for a subwoofer.

    This is a really well recorded disc of 20 organ church movements with full blown extension WAY below 20 Hz. The dynamic range has not been limited in any way, and the sheer amount of energy in the 15-20 Hz region is mind blowing. If this were a commercial release, it would have to have the equivalent of the Telarc 1812 "Digital Cannons" warning.

    Anyway, it was great fun playing with this recording yesterday and this another examples of a really beautifully recorded music disc that would be a total bass washout on the 15's or even the 25's. I had to plug a port on the PB2+ to get it to respond with total authority on this disc; it's that deep.

    Here's a ditty on how it was recorded:
    The recordings were made with AKG mics (three of them) with omnidirectional capsules installed. They were about 15' from each other across the front of the churches for a total width of about 30' , at a height of about 10'. I used a proprietary microphone preamp/mixer (only one exists) which is one of the secrets of how these recordings sound so good. The signal was sent to a modified Sony DAT recorder and captured at 48Khz/16 bit. The audio was digitally imported into ProTools and sample rate converted in non-realtime at the highest quality setting which takes about 8 hours of number crunching on a fast computer for this amount of material. The tracks were edited in ProTools before burning onto CD.
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • mantismantis Posts: 15,374
    edited September 2003
    Doc,
    SVS gives you port plugs with there Sub's????Thats intresting.I noticed a huge difference in the Dynaudio line when using port plus.We used them mostly when the speakers HAD to go closer to the wall then we would have liked.This plug was made out of foam.Worked very well.I like the tightness.

    One day I will get to hear/feel your sub.

    Does that read right??
    Dan
    My personal quest is to save to world of bad audio, one thread at a time.
  • Dr. SpecDr. Spec Posts: 3,780
    edited September 2003
    Dan:

    Yes, the PB2+ has three 4" flared (on both ends) ports. You get two port plugs to alter the tune points on the sub.

    The anechoic chamber tune for the sub is as follows:

    Anechoic:
    3 ports open 25 Hz
    2 ports open 20 Hz
    1 port open 16 Hz

    With typical room gain, this translates into a real world extension of:

    In-Room:
    3 ports open 20 Hz
    2 ports open 15 Hz
    1 port open 11 Hz

    My own in room measurements verify this. In fact the SS filter setting actually kicks in several Hz lower than the listed value to accomodate for room gain.

    The 32 foot pipes on this organ provide a 16 Hz fundamental, so I plugged a port to get maximum power in the 15-20 Hz region.

    I left the SS filter at 16 Hz, which essentially allows the sub to extend even lower than the tune point would suggest - to about 13 Hz in-room. Mismatching the port configuration and the SS filter setting is called a "non-conventional tune" and increases the potential to bottom the drivers by allowing them to operate below the enclosure tune point, but the PB2+ is so understressed in my size room I don't worry too much about it.

    Here is an actual in-room FR sweep of the PB2+. I'm running the yellow line tune for the organ recording, and you can see the curve swell and peak in the 14-17 Hz region - smack dab in the middle of the 16 Hz note for the 32' organ pipe. You can imagine how impressive this sounds in a 2000 ft3 room. You are welcome to come over any time for a demo.

    Doc

    PB2FR2.jpg
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • RuSsMaNRuSsMaN Posts: 17,995
    edited September 2003
    Great data Doc, I'm a little confused though. I thought closing ports would raise the tune point?

    I mean, the more ports open, the lower the tune?

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
  • Dr. SpecDr. Spec Posts: 3,780
    edited September 2003
    No, it's the other way around. Here is the other graph of the "conventional" tune points (i.e., SVS recommends these for the best combination of extension and woofer protection).

    There are actually 6 tune configurations for this sub (shown by # of ports open and SS filter setting).

    3/25 (conventional - SVS recommends)
    3/20 (non-conventional)
    3/16 (non-conventional)

    2/20 (conventional - SVS recommends)
    2/16 (non-conventional)

    1/16 (conventional - SVS recommends)

    My room is medium sized, so I run mine in the 3/16 tune for almost all applications (except the church organ music where I went 2/16).

    You can see the 3/16 non-conventional tune (green line, 1st graph) peaks at 22 Hz and allows the sub to naturally roll-off with room gain and play down into the mid teens.

    In comparison, in the 3/25 conventional tune (blue line, 2nd graph), you can see the SS filter very sharply ramps the response at 21-22 Hz. The 3/25 tune is for plaster cracking playback levels in large rooms where maximum protection of the woofers against bottoming is required.

    The 1/16 tune trolls to a disgustingly low 11 Hz, but the overall output is limited by only one one port being open. I do not prefer this tune for any application.

    Ed

    PB2FR1.jpg
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • Strong BadStrong Bad Posts: 4,216
    edited September 2003
    All I can say is Doc...I have got to get me one of these SVS Subs!

    What is the biggest difference you've noticed between the original design (the tall round subs) and the newest line (the traditional box type sub)?

    How do they compare musically? How about all out with a movie going in 5.1?

    John
    No excuses!
  • madmaxmadmax Posts: 12,438
    edited September 2003
    So why does a smaller port (one rather than 3) lower the resonant freq of the box?
    I don't understand that one. :confused:
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • RuSsMaNRuSsMaN Posts: 17,995
    edited September 2003
    I don't get it either Chuck.

    I would think the fewer ports, the higher the tune, and higher max spl.

    More ports, lower tune, and lower max spl.

    I've been trying to make sense of it for 2 days. Not saying I don't believe Doc, I just can't get it to make sense to *me*.

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
  • Dr. SpecDr. Spec Posts: 3,780
    edited September 2003
    The box subs and the cylinder subs sound identical if they have the same driver (ISD, Plus, Ultra) and tune point.

    The box subs with dual drivers of course outdo the single cylinders in terms of overall SPL.

    For example, Tom V of SVS recently stated the PB2-ISD tuned to 20 Hz (one port plugged, two ports open) will match or even slightly exceed a 20-39PC+ tuned to 20 Hz (all three ports open) in the 16-25 Hz range. Above 25 Hz, the PB2-ISD beats the 20-39PC+ by 3-4 dB due to its greater driver surface area.

    As far as the tune points and the port plugging, HSU is the same way with the VTF-2 and VTF-3. The proof is in the pudding with the graphs, and I know no one is doubting me. But I can only answer this tonight because I have all the port and enclosure tuning equations on my home PC.

    Each port has the same length (probably about 25"). Each port has the same surface area (4" ID = 12.6 in2 not counting flared ends). And the internal enclosure volume is constant (for the purposes of this exercise anyway). The enclosure exterior dimensions are 18x25x28 (or thereabouts). The internal volume (taking into account wall thickness and drivers, and amp, etc.) is probably around 9,500 in3 or 5.5 ft3 (rough guess here, could be a bit less).

    If anyone has the equation that will dicate the tune point for a vented enclosure, you can input the port length and port area and enclosure volume for all three ports open, for two ports open, and for one port open and see what happens.

    Burdette might have it handy; he just built his sono-sub and we crunched a bunch of numbers to calculate the tune point. WinISD will do the same thing, I just don't have any of this stuff at work. In fact, come to think of it, the thread where Mark and I calced out some tune points might have the equations posted. Anyone want to do a thread search?

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • madmaxmadmax Posts: 12,438
    edited September 2003
    With my program increasing the port size lowers the resonance freq. It may be that they are already at the lowest response most people would choose with the ports plugged and are digging even deeper when the other ports are open. Given that, if you lower the res freq even more (by opening the ports) the response is drug even lower at the expense of not being flat. That is the only logical conclusion.
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • VR3VR3 Posts: 23,371
    edited September 2003
    A sealed enclosure hits lower than a ported enclosure. But not quite as loud.

    Here is my guess, when you plug the port, more air pressure is put on the woofer to make it exstend farther, slower, almost in a way, flooding the driver. It also increases turbulance in the single port. So if you hit 16hz, the driver would have major air flow all inside the enclosure, with massives amounts of air gushing out of the single port
    - Not Tom

    Vr3Mods.com ///// Version3Audio.com

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • madmaxmadmax Posts: 12,438
    edited September 2003
    Actually some benifits of a sealed sub are that you control extension below the resonant freq and after you hit the res freq it is a steady slope of 3db per octive thereafter. If your room is the right size then it starts making up for this loss. It is also very easy to eq in a larger area since you know the curve.
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • Dr. SpecDr. Spec Posts: 3,780
    edited September 2003
    This formula is from "The Loudspeaker Design Cookbook".

    Lv = ((1.463 x 10^7) (R^2) divided by (Fb^2)(Vb)) – 1.463R

    Where:

    Fb - is the tuning frequency of your enclosure in Hertz.
    Lv - is the length of your port in inches.
    R - is the inside radius of your vent tube.
    Vb - is the internal volume of your enclosure in cubic inches.

    In our case for the PB2+, the (estimated) values are:

    Fb = to be calculated
    Lv = 25" (fixed)
    R = 3.46" (3 ports open); 2.82" (2 ports open); 2" (1 port open)
    Vb = 9500 in3 (fixed)

    Remember, if the vent length is fixed, all you are varying is the port area when you plug a port.

    To calculate the "equivalent radius" of three 4" diameter vents, you need to use the forumula A=piRR. The area of three 4" vents is about 38 square inches, so the "equivalent radius" of a single vent with the exact same surface area would be 3.46" (i.e., a 7" diameter vent). The equivalent radius for two 4" vents is 2.82" (i.e., a 5.6" diameter vent). Of course there is no need for an equivalent radius for a single vent.

    Solving for Fb:

    27 Hz (3 ports open)
    22 Hz (2 ports open)
    16 Hz (1 port open)

    Whaddya know? The laws of physics and mathematics still apply!

    My guessimates on the PB2+ vent length and internal enclosure volume must have been pretty close since the numbers crunched out pretty close to the actual tune points.

    Class dismissed.

    Doc
    "What we do in life echoes in eternity"

    Ed Mullen ([email protected])
    Director - Technology and Customer Service
    SVS
  • madmaxmadmax Posts: 12,438
    edited September 2003
    I tried WinIsd again and I guess when you change port diameter it is automaticly changing port length making it hard to get a handle on port diameter while keeping the length the same and what it does to box res. Thinking after a few beers is ruining my evening here :D
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
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