Time for a change? What would you do?

[shame302]

Currently i have 2 subs. They do well but I'm sure there is more potential there. They are each passive 7 CUFT sealed enclosures with Kevin's DIYCable 15" DVC Tempest-X drivers. I'm powering both of the subs with a Bash 500. Obviously this is not ideal, but that's as far as the budget would allow. I originally had one sub powered by the Bash but added the 2nd sub to help flatten the room response. I'm satisfied with how they do in both HT and music though, had i a DEQ and perhaps more power i could probably get them to go lower and sound better overall.

Anyway, I'm bored and was thinking about perhaps using one, or both of them in a new cabinet just to try something new/different. I was poking around and sawTHIS thread And was pleased to see the Bill Fitzmaurice Tuba HT mentioned as that designed caught my eye. Space isn't a big issue really as the 2 subs currently there take up quite a bit of room though they use the room well. The space i have is 28"H/24"D/ around 10'wide and idealy i would like to use no more than that space. If it has to be taller than it has to fit between my surrounds so the width shrinks to about 58". Basically it's a small room and the subs are behind the couch, against the back knee wall where the rears are mounted.

Anyway, Just fishing for suggestions and ideas as my experience and knowledge is somewhat limited.

[---k---]

Based on my experience with a pair of RL-P15 subs, both sealed and ported, I think you're short on amp. I initially tried sealed with an amp on par with a Behringer EP1500 and was clipping it. I stepped up to a EP2500 and wasn't clipping it, but needed more power sealed. Switching to ported gave me the output I was looking for at a little expense of quality.

You might want to consider just adding some passive radiators to your current Tempest-X subs. That might be a better experiment. I believe that Kevin uses 500W amps in his model for those and claims bone crushing output. Buy a 4 pack of PRs is probably cheaper than THT.

About the THT, I just mentioned in another thread that I'm thinking about building a THT for my brother. I want to see what all the hype is about. But, I have to admit that I have some serious doubts.

Here is what Bill himself posts:

http://billfitzmaurice.net/THT.html

Take a look at this SPL chart, which compares the performance of a Tempest Classic 15 driver in a sealed and vented box, and when loaded in a 24 inch wide Tuba HT, all three cabinets with corner placement:

From the description of the graph, it sounds like he is saying that this is the predicted in room response after corner loading. Though, the sealed doens't look like it is experiencing room gain, so I'm not sure. I planned on contacting Bill, but haven't got there yet. But, if this is in room, that graph isn't very flat! And it drops like a rock after 25hz. And, I also believe you better have a good crossover in place too, because the response is quite extended. And, the Tuba's cost quite a bit more for plywood. A real hidden cost.

I'm really wondering what the response looks like if it isn't corner loaded. I'm probably not going to be able to corner load it at my brothers, and he has a large room with wimpy wood paneled walls - not likely to get tons of room gain....

I've come to really enjoy my RL-p15 ported sub. I like the fact that it can shake the room with those 18hz sound effects that you can't hear. It is fairly clear and articulate.

But, I guess if you're just looking for that slam/boom between 40 - 60hz, the tuba can't be beat. This is where most action is occurring, so I think people can be pretty impressive.

The biggest problem I have with it is the fanboys at AVS. IMHO (and often wrong) 90% of them have no clue. I haven't read all of the posts, but they seem to be a bunch of nut jobs. I respect Bill. I think he is a good, honest, knowledgeable guy. I think he might just have a different set of goals and objects than some of us crazies here.

We'll see..... My brother will be comparing it to a HTIB, so he won't know the difference. But, I'll have it in my room for a while.

[shame302]

I could def. use more amp. My buddy brought his EP2500 over and it was much louder. Output isn't a "huge" concern for me as the subs are right behind the couch and do very well there but i like that low end extension and that is something i'm super limited on. Still, if i can get a drastic improvement with different enclosures i would certainly be interested even though i have always preferred the "sound" of sealed subs. I'm limited to the "eq" on the plate amp as well. I can keep it from maxing the driver out against the surrounds down low but i cant control a nasty in room peak i have at around 40 ish hrz. Something i have to just deal with for the time being. I was just interested to see if i can use one, or both drivers in another enclosure to get better results. The driver in the corner is about 6db louder than the other one so that's another issue i have to accept for now. Great spot to sit in if you like the bass.

The THT (particularly that graph) boasts quite a bit more output over all despite the dip at 25hrs which is what caught my eye but like you, I'm skeptical. Id have to probably place the horn sideways between my rears though and i don't know how that would effect it.

I could easily throw some P.R.s in my enclosures though. At 7CUFT and sealed, what can i "expect"? I have to admit i don't know much about them and never really considered them. What are the "rules"? 1 per driver or 2? can i upsize to 18"s or is that a no-no.

I won't be able to go with a bigger amp for awhile and i don't want to get one (EP2500 or perhaps the EP4000 depending) without getting a decent DEQ as well.

Basically i'm just jonesing to tinker with something and I'm not funded well enough to do another set of DIY mains atm.

I have been eyeballing Kevin's 21"s as well for the future but certainly not an option for the time being.

[evilskillit]

Well as you can see you can get a lot more low end extension if you went with bigger ported boxes for your current subs. You could play around with modeling, you might be able to go smaller than what I have and still get way better low end extension.

You could also go with passive radiators. Box size would be smaller, extension would be much deeper however nice big PRs arent super cheap.

[ThomasW]

Tempest-X like other high excursion drivers aren't intended for use in horns, and that's why Bill recommends the Dayton DVC15" or similar driver in the THT.

[shame302]

Hmm. What's the difference between the "Tempest classic" and the Tempest-X?

I'm certainly not stuck on a horn but was looking at them as an option. It's looking like dimensionally the THT doesn't really fit my room anyhow unless one, placed sideways would do the trick. I actually like how my enclosures fit in the space they are in. Perhaps P.R. would be the way to go provided hey would work well in that size enclosure. Would they be worth the cost though?

[evilskillit]

tempest classic may have different TS parameters than the tempest x, or maybe tempest x is the tempest classic and tempest x2 is the new one. We'd have to figure it out.

Yeah PR would definitely bear some looking into for low end extension vs sealed. If you go ported, if possible you may just keep the same width and depth and just go taller. After all, were you really using the space above those things anyways?

If you want to go in one of those directions let us know and we'll see what we can come up with.

[---k---]

I had assumed that he was buying the DVC. Which is why I thought some PRs were comparable... Ooops. Old adage true again.


The Tempest classic is very different than the Tempest-X. Just look at the X-max

[ThomasW]

Hmm. What's the difference between the "Tempest classic" and the Tempest-X?

Go to the PE website and look at the T/S parameters for Dayton DVC 15. It was a clone of the Tempest Classic.

PR's need 2.5-3 times more swept volume than the driver. So buying PRs to work with a pair of Tempest-X would be a pretty $pendy investment

[shame302]

Even Kevins P.R.s? Its around 100 bucks each for the 15s, a little more for the 18s

I had assumed that he was buying the DVC.

Nah, Just thinking about doing something different with what i already have or improve it.

[evilskillit]

Yeah. I thought Kevin was blowing out his PRs at about $50 each, but that must have been a different model and it must already be gone . But yeah a general rule for PRs is you need 2 high excursion PRs of the same SD as the driver or 1 if its an order of magnitude or 2 higher SD than the woofer and has high excursion. Could end up costing you over $200 per unit. Which begs the question, how much is a small box worth to you, if you want more low end extension?

[shame302]

Yeah. I thought Kevin was blowing out his PRs at about $50 each, but that must have been a different model and it must already be gone . But yeah a general rule for PRs is you need 2 high excursion PRs of the same SD as the driver or 1 if its an order of magnitude or 2 higher SD than the woofer and has high excursion. Could end up costing you over $200 per unit. Which begs the question, how much is a small box worth to you, if you want more low end extension?

You say they have to be high excursion. Does this mean an Xmax more than the driver itself, as it's a high excursion driver. It's my understanding that i would then be looking at 2 of the 15" PRs or one 18" that kevin offers.

What could i expect from either in my enclosures? Obviously it would be cheaper to grab 2 18" PRs (one for each enclosure), than it would be to buy 4 15" PRs though i would assume the 15" would perform better?

I suppose i could build a ported enclosure, or 2 but then i have alot of waste getting rid of the 2 enclosures i currently have.

[---k---]

Kevin's applications notes for the Tempest:

http://www.diycable.com/main/pdf/TX2Apps.pdf

Designs given:
1) 83L Sealed
2) 141L Sealed
3) 226L Sealed
4) IB
5) 141L, 21hz tune Ported
6) 180L, 19hz tune Ported
7) 340L, 12hz tune Ported
8 ) 100L, 2-15" PR 20hz tune PR
9) 141L, 2-15" PR 20hz tune PR
10) 180L, 2-15" PR, 20hz tune PR

15" PR are $55/ea.


Lots of options there. Lowest cost would be the #6. It is about the same volume box as you currently have. Just cut a hole in it and stick an 8" diameter piece of sonotube, and you'll have a fun sub. I went from sealed to ported. It probably isn't as accurate and flat room response, but it sure is fun feeling the sofa shake.

[stgdz]

I built a THT and got it hooked up over the last week. The thing is an absolute monster in terms of spl/watt. I put it together for around $450 or so but tapered horns are very efficient in getting the most spl out of the watts available/supplied. Since every design has it's drawbacks the biggest one with the THT is that it is huge, the second one is that mine drops off around 20hz but that may be due to my dayton plate amp.

There is some designs that use the shiva-x over at the HTshack. Most of them are tall and skinny. Horns are a different breed though, you can't just go for X-max there are some different parameters that you need to look at. I am happy with mine but good god does my head hurt, I played around with it the entire weekend and now I have a THT hangover.

[evilskillit]

When I say high excursion I'm talking something like Kevin's PRs, the Partsexpress ones don't have enough excursion and you'd need an extra 1 or two of those. But yeah basically 1x 18" or 2x 15" of Kevin's PRs should work fine.

[shame302]

Hmmm.....So:
Keep 'em like they are,
2 15" PRs per sub (need 4),
1 18" PR per sub (need 2),

Or port those suckers. How the heck is one to decide? Worthy of mentioning is this is a pretty even split between HT and music.

All much easier than building a THT that wont fill the available space as smartly. Would a significant gain in spl and or sub 22 hrz extension be realized or would it be marginal? I really don't know how to compare them. FWIW, they do well with music and anything above say, high 20s. I would love to gain more of that "silent" low end bass that you can feel rather than hear without losing out in the upper ranges.

[brent_s]

Shame302, slightly off topic question, but did you modify the rumble filters in your BASH500s? As shipped from P-E, they're f3 is 30Hz with a 12dB/octave rolloff below that...along with a 2dB peak up around 36Hz. Just food for thought...you might find you've been missing a whole octave of extension right there.

-Brent

[evilskillit]

Yeah I forgot all about that, bash amps come with a built in highpass filter that you'll probably want to modify, otherwise porting will do nothing for you.

As for will it be noticeable, yes ported subs definitely have noticeably more bass in the lowest registers. I'd have to model it but apparently you can just put a port in the boxes you already have as they are adequately sized for a 20hz tune, that would work out pretty neatly, be the lowest cost and least wasteful solution as you use your existing boxes and only add a port.

[shame302]

Shame302, slightly off topic question, but did you modify the rumble filters in your BASH500s? As shipped from P-E, they're f3 is 30Hz with a 12dB/octave rolloff below that...along with a 2dB peak up around 36Hz. Just food for thought...you might find you've been missing a whole octave of extension right there.

-Brent

Eh, what now? No, the amps are as they come from "the factory". So your saying they start too roll off at 30hz regardless of what i set the "adjustments" too?

Yeah I forgot all about that, bash amps come with a built in highpass filter that you'll probably want to modify, otherwise porting will do nothing for you.

As for will it be noticeable, yes ported subs definitely have noticeably more bass in the lowest registers. I'd have to model it but apparently you can just put a port in the boxes you already have as they are adequately sized for a 20hz tune, that would work out pretty neatly, be the lowest cost and least wasteful solution as you use your existing boxes and only add a port.

Awesome. If i knew what i was doing i would try that myself, but rather have someone with experience explain it to me, rather than mis-interpret by myself.

[---k---]

. How the heck is one to decide?

I find flipping a coin a very effective method when you your situation.

Once you have built both, then you can wisely choose. Don't listen to people on the internet forums. They are a bunch of crazies!

[shame302]

LOL, Crazy is relative. Perhaps i can port one, compare that to the sealed one and go from there. The "new" price on the PRs are attractive though and i have to admit i think they are "neat-o". Why did he cut his price on them so aggressively?

[1Michael]

Build the ported design, then plug the hole and decide which you like best. If you like the sealed you can then add stuff inside the box to get it to the proper volume.

[evilskillit]

Check this. It is a link to the partsexpress pdf showing the bass boost and cut frequency response of the bash 500 plate amp.

http://www.parts-express.com/pdf/300-752.pdf

You can see from the factory it comes set to cut bass around 27-30hz. This can be modified, you have to take the thing out a change a few small resistors on the board. You can push it as low as 13.9hz, which might make a pretty noticeable improvement for you even with your current sealed configuration.

[shame302]

Not sure exactly what that all means. I know the Bash has a "boost" down low of i think 3db and if i'm right it only happens between 31 and 35 hrz? I guess i'm just not reading things correctly. Is FC a "brick wall" cut off or is that where it is set to begin "rolling off"?
I guess what i need is a better understanding of what all the abbreviations mean. I was under the impression that my subs do in fact go down into the high teens, low twenties but going by the charts, that's not possible. Anywhere i can go that has a good FAQ/explanation of the common terms regarding subs?

My current amp settings:
Gain = probably 65-70% on the dial
Phase = 0
Auto
Crossover =Enabled/ around 60HZ
Q = almost on "high"
Level = 6-8DB
PEQ = 20 HZ
Subsonic filter and EQ = 12 HZ

Basically came to those settings because un-EQ it would max the drivers out against their surrounds sometimes with low bass.

Does room eq work with windows W? How about a Sub modeling software?

[brent_s]

Not sure exactly what that all means. I know the Bash has a "boost" down low of i think 3db and if i'm right it only happens between 31 and 35 hrz? I guess i'm just not reading things correctly. Is FC a "brick wall" cut off or is that where it is set to begin "rolling off"?
{snip}

The boost is created by the rumble filter. The rumble filter is just a high Q highpass filter. It's cutting your signal 12dB per octave below 30Hz. Due to the high Fc and Q (1.2), it's also creating a 2dB bump in the signal centered at 36Hz.

They say a picture is worth 1,000 words. I've put together a comparison for you to illustrate what you're missing. All alignments stay below Xsus with 500 watts.

yellow = Tempest-X in 7 ft^3 sealed, 500 watts stock filter
green = Tempest-X, 7ft^3 sealed, 500 watts, Fc=13.9 Q=1.0
red = T-X ported, 7 ft^3 20Hz tune, 500 watts, Fc=18 Q=1.0

The higher Fc is needed with the ported alignment to protect the driver from unloading below tuning. It's also possible to tune lower, but I didn't feel like running through all of the permuations at the moment. :-)

The modified sealed filter gives you an extra 6.5dB at 20Hz. That's the equivalent of your current pair running together!

-Brent

[brent_s]

Check this. It is a link to the partsexpress pdf showing the bass boost and cut frequency response of the bash 500 plate amp.

http://www.parts-express.com/pdf/300-752.pdf

You can see from the factory it comes set to cut bass around 27-30hz. This can be modified, you have to take the thing out a change a few small resistors on the board. You can push it as low as 13.9hz, which might make a pretty noticeable improvement for you even with your current sealed configuration.

With the 2nd order Sallen-Key formulas, you can actually calculate pretty much any Fc/Q you want. I like to do things the easy way...grab Jack's spreadsheet for the Foster amp. You'll need to unlock it. The cap value needs to be changed to .22 to get values that match the P-E boost chart. Then, just set your desired Q and Fc and out pops the resistor values. Any Q above .7071 will introduce boost...bigger Q, more boost.

-Brent

[brent_s]

My current amp settings:
Gain = probably 65-70% on the dial
Phase = 0
Auto
Crossover =Enabled/ around 60HZ
Q = almost on "high"
Level = 6-8DB
PEQ = 20 HZ
Subsonic filter and EQ = 12 HZ

Basically came to those settings because un-EQ it would max the drivers out against their surrounds sometimes with low bass.

Does room eq work with windows W? How about a Sub modeling software?

Ok, I just reread this part and now I'm a bit confused. Which amp do you have again? The BASH500 or the HPSA500? The BASH500 doesn't have PEQ, but the HPSA-500 does. If you don't have the HPSA, where are the PEQ, subsonic filter, and EQ settings coming from?

The HPSA has a more subwoofer friendly default rumble filter...Fc=18Hz, Q appears to be less than 1 due to no obvious peak in the frequency response, and an 18dB/octave rolloff.

Since this appears to be a surround system, why are you using the xover in the plate amp instead of the processor? The processor's digitally implemented xover is likely much more accurate than the analog circuit in your plate amp. It will also create the necessary complementary lowpass/highpass blend between your mains and subs.

-Brent

[shame302]

I apologize for the confusion.THIS is the amp that i have. I guess using 2 x overs is a bit redundant but never thought much of it. I really appreciate the graph, thank you.

[brent_s]

I apologize for the confusion.THIS is the amp that i have. I guess using 2 x overs is a bit redundant but never thought much of it. I really appreciate the graph, thank you.

OK, that makes more sense. I wondered if it might be the OAudio after I headed down to dinner.

Unfortunately, OAudio has never released the Q/Fc of the various filter settings to my knowledge. Looking at the rumble setting graphs in the owner's manual, I would expect the 25Hz or 20Hz setting to be best for your current subs...with no extra PEQ dialed in. 6-8dB is a lot of boost to dial in at 20Hz...every 3dB doubles the power delivered so if you get a sound in a movie that might ask for 100 watts at 20Hz, your amp is trying to deliver 400+...you can see where that might get out of hand real quick. And that's ignoring the nearly +10dB it looks like the 12Hz setting dials in at 10Hz.

Given the amount of boost present, I think it's more likely what you thought was over excursion by your drivers was actually clipping in the amp. Sitting here playing with WinISD trying to guestimate the Fc/Q of the OAudio filters, I've dialed in some pretty outrageous boost that still should have stayed within the suspension limits of the T-X. I've heard amp clipping that sounded like the driver was making physical impact in its suspension.

Due to the high Q of the OAudio filter and resulting boost, it's not a real good match for ported designs. If you port your cabinets to 20Hz, while counterintuitive, it might be best to use the 25Hz filter setting. It looks like the settings really correspond to the center of the boost peak more so than Fc.

Missed your other questions earlier. Yes, WinISD Pro is a good freeware modelling program that runs under Windows. There's also the Unibox spreadsheet for Excel (OpenOffice Calc still can't quite handle its macros).

RoomEQ Wizard runs on Windows or Macs...it's a Java program so the Java VM is the real requirement. This would actually be a real good place to start to get objective data for your current setup to figure out a path forward. You'll have lots of variables to check...I would start by taking out the PEQ boost and plate xover and step through the various filter settings to see what their naked in room response looks like.

If you've got a xover set in your processor in addition to engaging the plate amp's lowpass, you're doubling your rolloff slope. This will definitely impact the blend to your mains as the processor's highpass is (hopefully) designed to be complementary to its lowpass. The plate xover will then interrupt this balance to some degree. Since xovers aren't brick walls, it'll also extend the reach below the set point where the rolloff becomes audible.

-Brent

[shame302]

Okay, how do you figure out how much "boost" you get from an amp?

I thought the sub sonic "eq" was a cut off point, and the parametric eq serves as to extenuate, up to 12db, a targeted in room "peak"? The Q (high, or low) determined how broad the attenuation occurred? and the regular X-over/eq was a roll off point?

[brent_s]

Okay, how do you figure out how much "boost" you get from an amp?

I thought the sub sonic "eq" was a cut off point, and the parametric eq serves as to extenuate, up to 12db, a targeted in room "peak"? The Q (high, or low) determined how broad the attenuation occurred? and the regular X-over/eq was a roll off point?

Your understanding of the various controls appears to be correct. I read your PEQ "level= 6-8dB" as 6-8dB of boost. I didn't realize the OAudio amp's PEQ only did attenuation. The PEQ on the HPSA amps has both boost and cut range. BTW, most of us would pay to have the natural peak at 20Hz that you seem to be trying to cut. :-) Are you sure you really have a mode there? You may be fighting the boost being introduced by the subsonic filter*. I would expect the 8' mode (typical ceiling height) around 70Hz to be the most annoying, typically...but your double xover around 60Hz may be attenuating that one.

*FWIW, the T-X in 7 ft^3 sealed has a groundplane response that's only -7.5dB at 20Hz with no EQ applied at all. Just like modes, room gain is dependent on room dimensions and I've seen a number of designs that are as much as -10dB at 20Hz end up measuring flat in a room. If you're picking up more then 7.5dB by 20Hz from room gain, combined with the boost from the rumble filter, that could also account for the 20Hz issue that you're trying to tame with EQ. If so, a ported alignment with even flatter extension to 20Hz is going to make the situation worse.

OAudio could label the subsonic filter settings a number of ways...Fc and Peak center being the most obviuos...A/B/C/D would work, too. However, looking at the frequency response graphs of the various settings in chart 1 on p.12 of the owner's manual, the values they use look like the center frequency for the peak induced by the Q of the rumble filter. We know the Sallen-Key circuit used to build most rumble filters induces a peak somewhere above the Fc of the circuit when the Q is greater than .7071. Since the peaks appear centered at roughtly 12/16/20/25, I know Fc must be something lower. FWIW, the rumble filter appears to be a typical 2nd order (12dB/octave) highpass.

I'm simply estimating the amount of boost at each setting using that same chart 1 in the owner's manual. Compare the level around 60-100Hz where all of the curves seem to overlap to the individual curves for each setting lower in frequency. I'd call the base level around 53/54dBr from their chart...suggesting 2-12dB of boost depending on which filter setting is used.

-Brent

[shame302]

Awesome, thanks for the response. I'm not really concerned with the in-room output of the subs down low. I was only trying to attenuate that in order to protect the drivers. I currently have no way to measure anything, but in certain scenes with very low bass the subs would max out against the suspension, or at least it sounded like it. I'd love more usable extension down low. That's why i was considering going with a different enclosure type. If i could get more output by modifying these enclosures than why not, right? Eventually, I would like to get an EP2500 with a decent DEQ. so i can actually measure and EQ the room with some sort of accuracy.

My room is an odd acoustical nightmare. The ceiling vaults from 8' to 10' but drops strait down back to 8'. It's a split level with the wall separating the living room space and kitchen space removed. Behind the rear speakers is the stairwell. Everything is all open.

I'm willing to port one of these enclosures in the name of experimentation. I can always re-seal and stuff the box if i am unhappy. I know an 8" port is the way to go but don't know how long it has to be or where to tune it to.

Does the Port increase output from a sub in those tones that are so low you can't hear them, only feel them, or just the audible ones?

[evilskillit]

We can help you model it up. If nobody else does I will after work today. As for the frequencies that are boosted by the port they will mostly be around the tuning frequency of the port, so if the ports tuning frequency is 20hz then the port will mostly be boosting output in the 15-25hz region, so say output at 50hz will be almost completely unaffected. For all intents and purposes until you get near the tuning frequency it will act like a sealed unstuffed box of whatever size it is. 5-10hz below the tuning frequency things get all wonky and the driver starts unloading at that point excursion skyrockets. However if you tune low and then place a cutoff a bit lower than your tuning you will protect your driver and probably not be able to notice any of the missing frequencies anyways.

[shame302]

Awesome, Thanks! Sounds like a 18-20HZ tune would be they way to go then. :T

[evilskillit]

Using WinISD these are the numbers I got. First graph is spl at 500 watts. Second graph is port air velocity. It looks high on the very low end but you'll have a rumble filter kicking in around 15hz and that will keep the air velocity way down. Next is excursion, which shows why you need a filter kicking before 12-15hz and finally the last graph shows the port output, since you asked.

I'm not sure what your box dimensions are, hopefully that port isn't too long. You can of course use bends, if possible. I modeled 18hz with a 6" port. If you go to an 8" port the port has to be over 50" long. If you tune to 20hz you cut your 6" diameter port length down to like 22". So if around 30" is too long go with 22" for a 20hz tune.

[shame302]

Wow, awesome, thank you.

So, my box is actually 7.5 rather than 7. Not sure how much of that 7.5 is taken up by the driver and internal bracing.

Its 37x24X20 and the entire box is double layer 3/4"

I assume that will require a change the port length?

If i can borrow a 1 1/4" radius, round over bit, i would like to rout the port opening and probably use 6" sonotube or something for the port. If not i have a 3/4 bit but i'm not sure that would be "big" enough.

How do you correctly measure port length? From the inside of the radius, or the face of the box?

Should i make some sort of "flute" at the inside end of the port?

Finally, Should all of the "stuffing" be removed? They are filled pretty much completely with poly-fill.

[---k---]

Measure from the face of the box.

Flute on the inside would be preferable, but is a pain. At the levels and frequencies you're going to get chuffing, you probably don't care about chuffing.

remove most of the stuffing and then add to taste. I believe that Kevin's models do assume heavy stuffing.

[evilskillit]

Sorry I haven't responded, I've been out in the country with nothing but dial-up since Thursday night. This is the first time I've been on-line since my last post.

Usually ported boxes don't use stuffing, you can add it to even out response tho it will attenuate port output a bit I believe. I have a pair of ported boxes that had some nasty resonances and humps in response and I stuffed them heavily. They sound better but overall output is down a bit. Some guys will just jam a pillow or 2 into one end of the longest dimension to try to help with standing waves.

Going up to 7.5cu-ft will actually make your required port length slightly shorter. However the driver, bracing and the port will eat back into that 0.5 cu ft by a little bit. When I get home tonight I could re-figure for 7.25 cu ft. The difference will most likely be negligible.

My understanding is if you flare the end of a port you measure length from the beginning of the pipe and do not include the flare into the length of the pipe.

If you use an elbow measure the length of the elbow by measuring down the middle of it. As for chuffing and port noise I'm guessing if you use a high pass filter around 15hz then this should never be a problem as you're only nearing chuffing velocity in a 6" port at around 15hz at full 500watts of power. The filter will mostly take care of that, and at any less than 500 watts you won't have any problems either.

[shame302]

Thanks. Finally getting back here myself. I really appreciate the input :T Would a 3/4 round-over be effective enough or should i try harder to borrow, or buy a cheaper 1 1/4 bit?

Also considering placement of the port. Likely, i will put the output at one end of each of the subs. I assume its not a good idea to have them facing each other/firing into each other. Other options would be to have the left subs port on its left side and the right subs port on its right side, or both subs have the ports on either the left or right side. I could possibly locate the port on the fronts and use a bend but then i probably wouldn't be able to use sono-tube for the port like i wanted.

[evilskillit]

Having the subs or ports facing each other shouldn't matter, unless they're like 1" apart or something. Otherwise no problems. Mine face each other, tho they are on opposite ends of the room

As for the round over on the port, bigger is always better, but remember you have to subtract that from the port length. The length starts at the beginning of the tube's diameter, no the beginning of the flare. 3/4 is pretty good, don't go nuts and buy a big expensive bit and router that can support it if you're just doing this one job.

[shame302]

Okay, i have 12" now between them and could almost double that if need be. I just didn't really want one of the ports exposed for the kiddies to put crayons and cheerios into when i wasn't looking.....LOL, JK

[shame302]

Okay, I DL WIN ISD Pro. The tempest isn't in the directory. What are the parameters of the driver. The drivers i have are the ones that proceed the Tempest X2 so i doubt the perimeters on DIYCable for the X2 are the same as the drivers i have.

I'm looking to model it with 2 smaller ports vs. the 6" as well as just mess around with the program.

[evilskillit]

Here is a list of downloadable WinISD files for different drivers.

http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/14410-downloadable-winisd-pro-files.html

You'll see tempest X1 and Tempest X2 down in the Exodus Audio section. If its an older Adire Audio tempest you can get the parameters from this link.

http://www.audiojunkies.com/product/99/adire-audio-tempest-15quot-reviews

[shame302]

Awesome! I don't think the program likes my computer much though.

[shame302]

So 2 4" ports plot the same as one 6" within the program for me. Does this sound right?