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post #1 of 34 Old 01-05-2014, 06:58 AM - Thread Starter
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This will be my first DIY build. Hopefully others like me can learn from this discussion...

After a lot of searching, I was going to buy a pair of Rythmik FV15HPs for my newly-finished basement HT. But then I stumbled on the DIY threads. After a lot more research, I bought two UXL-18s from the recent group-buy. Now I need to design separate enclosures for them. This is just for watching movies/TV with my family. The loudest volume level on our AVR during movies is -12db,so we don't listen very loud. But I have been told that I need to account for all 8000CF in my basement since it is so open. That is why I chose to go with the 18 inchers. I have also been told that I should go ported due to the large space.

So I have been playing with both winISD for a box enclosure, and a Sonosub calculator for a cylinder. First the box...

The wife definitely has a say here, so I figured a box 30w x 30d x 36h is about as big as I could go. Accounting for the driver (.243cf), bracing (680 cu in. but probably less if I use dowels), and port (approx. 700cu in) I came up with a box about 15.5 CF with a tune of around 12.5hz. The red line is one 6 inch vent at 27 inches, the green line is two 4 inch vents also at 27 inches.








Now for the questions. I plan on powering this with an INuke 6000DSP. I put in the signal strength as 1000 watts. Is that ok? It also shows a first port resonance of about 255hz. I don't know what that means. Is that value acceptable? I attached a graph of the cone excursion as well. I see that it goes above xmax below 11 hz or so. Is that acceptable? I also posted the rear port velocity for the two configurations. I was surprised they are nearly the same. Are those numbers acceptable?

And here is the Sonosub calculation:



It says the 1st port resonance is 191hz. Is that acceptable?

OK, now for some general questions:

Does enclosure shape matter? Box vs. cylinder? Is it just cosmetic, or is there a difference in sound?

Am I tuning these too low at 12.5hz? What do you recommend?

How close to a wall can I place a vent in a box enclosure. In my example, those ports would be 27 inches in a 28.5 inch space. That seems real close.

Should I flare the intake or output side of the vents?

Which would be better - one 6 inch or two 4 inch ports? I thought the two 4 inchers would have lower air port velocity, but it appears the same as the single 6 inch port.

Does it matter which direction I face the driver or ports in the box enclosure? Can I turn a side-firing driver directly at a wall so we just see the finished sides?

Can I put bends in the ports to get longer ports in smaller boxes? I have seen this mentioned before, but all that is said is that "it gets complicated" with no further explanation.

I have read that we all want the smallest enclosure with the lowest possible tune. But it is all about compromises. This is my first stab at designing something decently-sized with a low tune for movie viewing. Do you have any other ported suggestions for a smaller ported, low-tuned enclosure?

Since aesthetics are important to my wife, do you have suggestions for a sealed enclosure? What performance do I lose if I go with smaller sealed enclosures.

Sorry my questions are all over the board. This is all new to me.
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post #2 of 34 Old 01-05-2014, 09:55 AM
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hi, looks like you have really done some good homework preparing for this one.

i'll try to tackle some of your questions:

"But I have been told that I need to account for all 8000CF in my basement since it is so open."

yes.

"I have also been told that I should go ported due to the large space."

in that large of space, the amount of pressure vessel gain will be fairly low, so ported is a good option. pvg tends to kick in about where 1/2 wavelength is equal to the long diagonal of the room. not sure what dimensions your room is, but the long dimension is probably around 40-50 feet or so, which gives a wavelength of 80-100 ft and translates into a wavelength in the low teens (1130 ft/s divided by 80 ft), so for practical purposes don't count on any pvg.

"The wife definitely has a say here, so I figured a box 30w x 30d x 36h is about as big as I could go."

not sure if you have taken a look at the martysub, but it would be something in your ballpark performance wise. a little longer, but narrower and less tall. lots of different flavors of it exist, but the core idea is here:
http://www.avsforum.com/t/1489541/large-ported-dayton-ho18s#post_23711347

"The red line is one 6 inch vent at 27 inches, the green line is two 4 inch vents also at 27 inches."

that is a little small in my estimation. in winisd, put the power that you will use, 2200 watts or so, and then check port velocity. air speed above 17 meters/second is borderline. some subs seem to get away with high velocity and no chuffing, but keeping down air speed is a good first start. 8" diameter round or equivalent slot port is a little better. also, the slot ports in winisd as explained in the marty post seem to overshoot real measured results by a bit. as a result, I suggest a 20% adjustment on the slot port martysub. so if winisd indicates 50" for a given tuning, 40" will probably get closer to the target and 50" will come in a little low.

"Now for the questions. I plan on powering this with an INuke 6000DSP. I put in the signal strength as 1000 watts. Is that ok?"

yes. and then some. go ahead and model at 2200 watts as that is what the amp will do into 4 ohms per channel. the limiter can be used if necessary, but unless running sine waves are very low crest factor content, you should be ok at the higher power level.

"It also shows a first port resonance of about 255hz. I don't know what that means."

first port resonance is the same effect as when you blow over a coke bottle (well kind of). essentially you want the first resonance to be fairly well out of the target passband. for a sub anything over 160hz is probably good. in some cases, lower seems to be ok too.

"Does enclosure shape matter? Box vs. cylinder? Is it just cosmetic, or is there a difference in sound?"

within reason, it does not matter. it can be any shape. no impact on sound.

continued in next post...
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post #3 of 34 Old 01-05-2014, 10:10 AM
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"Am I tuning these too low at 12.5hz? What do you recommend?"

that is a personal preference. some folks can't really detect anything below about 15hz +/-. if you have lossy wood floors, the vibration lower than that may be an effect that you can enjoy a little.

the lower the tune, the more excursion the driver makes, which you can see on the excursion tab. the uxl has pretty big excursion, so 13hz or so would still keep the driver under control at full power. tuning a little higher gives a little more spl a little higher up in frequency where it may matter a little bit more. he other factor is build simplicity. I haven't checked but with something like the martysub, a single slot can tune it to about 15hz or so, iirc, lower then that and it has to bend and go up the back wall. no biggie, just something to be aware of. anything from 12hz-17hz should be fine.

" How close to a wall can I place a vent in a box enclosure. In my example, those ports would be 27 inches in a 28.5 inch space. That seems real close."

for a port, best to leave at least one port height to a boundary. if using a 6" port, 6". if using a 3" tall slot, at least 3". jamming it up can mimic a little longer port, but best not to get too deep into that.

" Should I flare the intake or output side of the vents?"

ideally yes. some empirical data here: http://www.subwoofer-builder.com/port-flares.htm
something like the martysub does ok without roundovers/flares though.

"Which would be better - one 6 inch or two 4 inch ports? I thought the two 4 inchers would have lower air port velocity, but it appears the same as the single 6 inch port."

best to use fewer ports and larger ports. 8" is probably the minimum for the uxl at full power in a low tuned cab. check air velocity at full power (2200 watts or so).

"Does it matter which direction I face the driver or ports in the box enclosure? Can I turn a side-firing driver directly at a wall so we just see the finished sides?"

that is fine. doesn't impact performance.

"Can I put bends in the ports to get longer ports in smaller boxes? I have seen this mentioned before, but all that is said is that "it gets complicated" with no further explanation."

yes. bends do many things from reduce pipe resonance effects to turbulence to effectively lower tuning. all these effects are not well documented, which is why folks say "complicated" with no further details. member neo dan has a sub with multiple bends and measured results. easy button end table i believe was the name of his threads. there were several versions. if you really want to dig into it, have a search on that. i don't recall the links off hand.

"I have read that we all want the smallest enclosure with the lowest possible tune. But it is all about compromises. This is my first stab at designing something decently-sized with a low tune for movie viewing. Do you have any other ported suggestions for a smaller ported, low-tuned enclosure?"

the smaller the internal volume, the longer the port has to be. the lower the tuning frequency, the longer the port has to be. the larger the diameter of the port, the longer the port has to be. all these effects make it impractical to build a small, good performance, low tuned sub, which is why you don't see them.

"Since aesthetics are important to my wife, do you have suggestions for a sealed enclosure? What performance do I lose if I go with smaller sealed enclosures."

a comparison in winisd can be made or there is also a comparison of sealed vs. ported in the martysub link. the amount of spl given up is in the ballpark of 10-12db around the tuning frequency, which is quite a bit.

" Sorry my questions are all over the board. This is all new to me."

excellent homework. excellent questions. excellent post!
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post #4 of 34 Old 01-05-2014, 10:15 AM
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also, at the beginning of the martysub post, there are some testimonials. if you search on each members name, you should be able to find their builds. all of them are a little different. atabea's for example may be more of a form factor for you. maybe not. just looking at some of the other subs might help get some creative juices flowing. member 316 has bass canons which are an extreme case of marty gone wild, and one member had something called the annihilators or something like that which was also kind of interesting, but I'm not sure if it got built.
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post #5 of 34 Old 01-05-2014, 01:13 PM
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I recall Dr Hsu saying that to avoid chuffing the bends in ports must be of a larger diameter than the straight lengths. I wonder if anyone thought about doing a circular, coiled ports, that would conserve space and make for a long port.
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post #6 of 34 Old 01-11-2014, 06:43 AM - Thread Starter
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As you suggested, I am leaning towards a MartySub-type of build. You mentioned that which direction I face the driver will not affect performance. Can you re-affirm that and explain that a bit? I have a hard time understanding how a driver pointing 90 degrees to my seating position won't have less of an impact that a driver pointing directly at my seating position. And on this topic, would I be correct to assume that performance would not suffer if I mount the driver in the center of a long side instead of on the end (keeping the slot port on the end though)?

In the Martysub thread, you mentioned that you ran WinISD with a 2nd order Butterworth@17hz and one parametric EQ @ 16hz q-2.0 gain 3.0. I have no idea what any of those are. Are those filters that can be set up on an amp like the INuke 6000DSP, which I am thinking of buying?

When I place those filters in WinISD at 2200 watts like you suggested, I still show rear air port velocity rising to 32m/sec at tune of 17hz, and 22 m/sec with 1000watts. Am I doing something wrong, or are those values acceptable?

I have also been reading neo-Dan's threads about port bends and easy button end table subs. I also came across this build:

http://www.avsforum.com/t/1484470/it-finally-begins-the-uxl-18-build

I will be really interested to hear how this sounds when it is completed. My wife still isn't thrilled about two Marty-sized subs. If this smaller enclosure works, it may be a good alternative, but I am having my doubts that it will achieve what he hopes, otherwise others would be making similar builds. Something must be missing there?
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post #7 of 34 Old 01-11-2014, 06:47 AM - Thread Starter
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Quote:
Originally Posted by fr8doggr View Post

As you suggested, I am leaning towards a MartySub-type of build. You mentioned that which direction I face the driver will not affect performance. Can you re-affirm that and explain that a bit? I have a hard time understanding how a driver pointing 90 degrees to my seating position won't have less of an impact that a driver pointing directly at my seating position. And on this topic, would I be correct to assume that performance would not suffer if I mount the driver in the center of a long side instead of on the end (keeping the slot port on the end though)?

In the Martysub thread, you mentioned that you ran WinISD with a 2nd order Butterworth@17hz and one parametric EQ @ 16hz q-2.0 gain 3.0. I have no idea what any of those are. Are those filters that can be set up on an amp like the INuke 6000DSP, which I am thinking of buying? I assume that Dominguez and Laudsbach will help with all this when it is time to set it all up.

When I place those filters in WinISD at 2200 watts like you suggested, I still show rear air port velocity rising to 32m/sec at tune of 17hz, and 22 m/sec with 1000watts. Am I doing something wrong, or are those values acceptable?

I have also been reading neo-Dan's threads about port bends and easy button end table subs. I also came across this build:

http://www.avsforum.com/t/1484470/it-finally-begins-the-uxl-18-build

I will be really interested to hear how this sounds when it is completed. My wife still isn't thrilled about two Marty-sized subs. If this smaller enclosure works, it may be a good alternative, but I am having my doubts that it will achieve what he hopes, otherwise others would be making similar builds. Something must be missing there?


With LTD's permission from PM so others may learn...

Hi Nick,

The direction of the driver doesn't matter in subs because the frequencies being produced radiant omnidirectionally (almost perfectly so) and any little bit of difference that there may be is simply reflected off the wall behind the sub anyways.

As a result, you will see subs that fire up, down, or sideways. This one is pretty popular:

http://www.seaton-sound-forum.com/post/the-submersive-original-1000w-1945927

you can see in the pictures how it fires "sideways". That doesn't provide any loss in bass performance at all.

Higher up in frequencies, drivers do radiate directionally, which is why you want your main speakers aimed more or less toward the listening locations.

The first filter is a high pass filter to protect the driver. Under the tuning frequency the driver "goes wild" so it is best to filter out some of those frequencies when uses a ported enclosure. The other one is simply a little EQ boost, which most folks will probably never need.

Air speed will be fine with an effective 3"x21" cross sectional area port, even with the added excursion of the UXL.

As for the size, it is more or less the internal *volume* that matters, so if you want a different form factor, that is possible.

You could do something like this, for example, if you wanted a sub that was tall and wide, but not very deep:

http://www.avsforum.com/t/1493647/the-plasmad-pocket-sub/0_50

Once you select dimensions, I can help ensure the port and tuning is good.
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post #8 of 34 Old 01-11-2014, 07:02 AM
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fr8 and LTD...the above Q&A has been great. Great basic "serious" DIY touchpoints all in one place...or at least a few posts...but right in a row.biggrin.gif

Thank you!


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Quote:
Originally Posted by blah450 View Post

fr8 and LTD...the above Q&A has been great. Great basic "serious" DIY touchpoints all in one place...or at least a few posts...but right in a row.biggrin.gif

Thank you!

+1 I agree, I have a shortcut on my desktop wink.gif

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post #10 of 34 Old 01-15-2014, 04:52 PM - Thread Starter
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OK, another "build" question...

Inside the enclosure, does it matter if the back of the driver is directly across from the ends of round ports or the end of a slot port - like 90 degrees across from them? For example, in the MartySub, the back of the driver is at the opposite end as the beginning of the slot ports. But, I am thinking of a design with the same volume, but in a shorter, fatter box that requires a bend in the ports. The ends of the internal ports ends up directly across from the back of the driver. Would this create an issue? Perhaps a problem with resonance - like blowing across the top of a coke bottle? Or is it best to avoid this design characteristic?
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post #11 of 34 Old 01-15-2014, 09:57 PM
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^^^ OK, another "build" question...

I’m not sure if more than the basic rule here applies "port diameter" but I have built many subs and bought subs where the port ends up behind the driver. Think sono or square sono type enclosures with the vent out the top. Admittedly there could be more to it I dunno? EDIT> From doing a google relating to the subject all seems fine also.

Getting back to slot ports though. I see the reason why we over shoot is because the driver sees the wall of the enclosure extending where the rest of the slot ends. The driver doesn’t know this thus causing our slots to come in long and low as LTD states.

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"Would this create an issue?"

no problem at all.

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post #13 of 34 Old 01-31-2014, 07:28 AM - Thread Starter
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Well, I am ready to build my twin UXL-18 ported enclosures in the next week. My wife would not give approval to the MartySub, so we came to a compromise. I am going to build a square-ish enclosure, around 10cf that will require a 90 degree bend in the port. Exterior dimensions will be 33H x 28W x 28D. This will come close (but not quite) to the output of the Marty, and keep divorce attorneys away..tongue.gif . I ran the numbers in WinISD, but I would appreciate it if others could review them to make sure I am not violating any rules or headed for disappointment and frustration, as I this is my first build.

- Exterior dimensions: 33H x 28W x 28D
- Material thickness is .75 inch MDF with double front baffle
- Bracing will be 1 inch round dowels in window pane pattern - approx. 500 cu/in.
- Port volume will vary depending on selected port height: (2 inch high port equates to approx. 3100 cu/in. 2.25 inch high port equates to approx. 3750 cu/in.) These numbers include adding the .75 inch MDF to create the slot board itself. They also include a reduction of 10% of the WinISD recommended port length. These variables will change the total net volume a bit, varying from 9.7 - 10.2cf. I just used 10cf in my models.
- Driver volume is .243cf.
- The models below were using1200 watts RMS power handling, as per IST's web site.









Do these graphs look ok?
When modeling in WinISD, do I need to change the "series resistance" number? I bought an INuke6000DSP, and was told to wire them to 4 ohms. Should I change the series resistance number to 4?
Also, can someone help me with a cutlist and pictorial display program?
I would appreciate any suggestions and advice.
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Looks good but you can certainly add more power if you like, plenty of excursion left. It’ll cause your air velocity to go up but you should still be good pushing it a little more if you like? If you go larger on your vent it’ll bring your 1st port resonance down lower which you’re as far as you want to go now. If you leave things as they are, from what I know (limited) your looking good fr.

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Looks good but you can certainly add more power if you like, plenty of excursion left.

I agree with steve...smile.gif

It looks like you have plenty of room left to try things with the DSP...I am looking forward to your build!
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post #16 of 34 Old 01-31-2014, 06:16 PM - Thread Starter
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I agree with what you both are saying. I know it can take more power. If I boost the power input on WinISD to 2000 watts, I get over a 2db increase in SPL. However, my rear air port velocity jumps from 18m/s to 25m/s. Is that number something I should be wary of? Should I increase the size of my port to bring that velocity down at high power levels, or is it acceptable? Increasing the port size brings my 1st port resonance even lower. It's pretty low to begin with...
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I hear what you’re saying. 25 AV would be fine real world imo but if you drop a Butterworth filter in at 17hz and add a 1000w see what she looks like.. It’s in the filter tab. You can engage and disengage to see what a difference it makes. Make sure your enclosure stays the same size though.

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Sorry, Steve. Those numbers in my last post were with a HP Butterworth filter already installed at 15hz. Without that, it would be almost 40m/s at 2000 watts. Unless someone recommends changing it, I think I will keep the port at 2 inches, and use the DSP on the Inuke to shape what I need. If I go that high on the power, hopefully I won't hear anything...tongue.gif
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If I go that high on the power, hopefully I won't hear anything... tongue.gif


LOL.. That’s part of what I meant when I said real world.. I know your kind. wink.gif Hey seriously though, I’ll put it up tomorrow and play with it and see if I can just by chance come up with anything just for the fun of it. I have/had my suspicions though (1st p r) and you confirmed them.

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post #20 of 34 Old 02-01-2014, 05:25 AM
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Why is it so rare to see someone using Dsp with ported enclosures? I see folks using things like the MiniDsp or Behringer iNuke for sealed enclosures, but never for ported?

What differences are there between DSP capability on a sealed enclosure versus a ported enclosure? Can you still boost the bottom end with DSP in a ported enclosures?
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post #21 of 34 Old 02-01-2014, 05:41 AM
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"Do these graphs look ok?"

yes.

" When modeling in WinISD, do I need to change the "series resistance" number? "

no. technically, you could try to guess how much it will increase with heating of the voice coil, but I wouldn't worry about it for basic cabinet design.

"I bought an INuke6000DSP, and was told to wire them to 4 ohms. Should I change the series resistance number to 4?"

no. just leave the series resistance at the default value. series resistance in the program gets added onto the resistance of the driver.

"Also, can someone help me with a cutlist and pictorial display program?"

not sure if your design is fully fleshed out. do you plan a recessed driver mount or just mount the driver on the front of the cab?

also, i would increase the port diameter to 3". making it full width with two braces gives 28" wide - 2 edges and 2 slot braces = 25". running the slot to the back of the cab and then up, there is plenty of room to make it 44-48" long. that should be ok from excursion control and give a slightly lower tune. the amp will put out 2200 watts into 4 ohms, so that i what you might want to model at.

my back of the envelope math is coming in just under 11 cubic feet, so your calcs there seem reasonable.

should be a good performer. just final tweaks at this point.

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post #22 of 34 Old 02-01-2014, 06:05 AM
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Quote:
Originally Posted by Martycool007 View Post

Why is it so rare to see someone using Dsp with ported enclosures?

Good question MC...smile.gif

I am using a DCX2496 on my big ported sub and have several filters engaged including a low shelf filter...the box is tuned to 11.5Hz.

I am going to help fr8doggr dial these in his space and plan on running a house curve, some form of low shelf filter and SSF with the DSP on his iNuke 6000.
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post #23 of 34 Old 02-01-2014, 06:08 AM - Thread Starter
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not sure if your design is fully fleshed out. do you plan a recessed driver mount or just mount the driver on the front of the cab?

Yes, it will be a double front baffle so I can recess the driver.

also, i would increase the port diameter to 3". making it full width with two braces gives 28" wide - 2 edges and 2 slot braces = 25". running the slot to the back of the cab and then up, there is plenty of room to make it 44-48" long. that should be ok from excursion control and give a slightly lower tune. the amp will put out 2200 watts into 4 ohms, so that i what you might want to model at.

Ok, now I am confused. If I increase the slot port to 3", my first port resonance drops down to 90hz and a length of 74 inches. That is with 10cf, tuned to 16hz, 2200 watts, 3 slots at 3" x 8.33" = 25". I must not be communicating something correctly.? Is it possible you ran the program with only 2 slots, because if I run it with two slots, I get your numbers above. But the port is effectively only 16.66" wide.
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post #24 of 34 Old 02-01-2014, 08:56 AM
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I’m sure you know about dragging the mouse over the speaker in the box tab and how that changes things? Anyway to answer your question I too could use a tutorial in the matter and will send LTD a PM hoping he’ll step back in. I know what I wanna say..

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post #25 of 34 Old 02-01-2014, 09:42 AM
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cylinder is the strongest per lb, that's why they make submarines that way.

"If Bad Sound Were Fatal, Audio Would Be the Leading Cause of Death."


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post #26 of 34 Old 02-01-2014, 10:34 AM
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I can get 114 1st port res in 11cf 16 tune not messing with the response but that’s a little low 1st pr. 118dB at 20.. I sent a PM to LTD, so at some point he’ll come around.

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post #27 of 34 Old 02-01-2014, 10:52 AM - Thread Starter
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Yeah, I'm coming up with similar numbers to yours, Steve. Thanks.
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post #28 of 34 Old 02-01-2014, 12:08 PM
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when looking at the first port resonance, you have to work with the shorter *actual* port length that reflects the correction factor.

just for example: at 11 cubic feet tuned to 16hz with a 3" x 25" port, it will show 64" long and a first port resonance of 105hz.

but if using a 20% correction factor, the port won't be 64" long for a 16hz tuning. it will be closer to 51" long.

the first port resonance of a 3" x 25" port that is 51" long is 132hz. (you have to go back to the tuning frequency and change it to reflect the adjustment. in this case, 17.7hz gives a 51" long port).

Listen. It's All Good.
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post #29 of 34 Old 02-01-2014, 03:08 PM
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Thanks LTD.. Lets see if I can word this correctly.. When a guy manually drags around the response and then goes back in and sets the numbers, re-enters volume, and tune.. all is good? Hope I’m not derailing your thread fr?

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post #30 of 34 Old 02-01-2014, 03:17 PM - Thread Starter
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Thanks LTD. I do understand what you are saying now. I was not accounting for the correction factor.

BTW, is 20% now the accepted reduction value we are using with WinISD? I have seen values mentioned anywhere from 10% - 25%.

Also, all the discussions of correction values came in the Marty sub, which has no bend. Does the 90 degree bend in my design affect the correction value at all?
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