designing w/winisd need advice

Hey Guys, I need some expert advice...

I ordered a new Kicker Solo-Baric L5 (square) 10" and I'm playing with WinISD to design the box. I've built several boxes in the past, but never with a software tool. After entering all the T/S info and looking at several different cofigurations, I'm wondering if I'm on the right track and seeing my results for what they are. I'll give you a little info about what I want, then show you what I'm looking at. I'm hoping that some of you that use this software often can give me your opinions or recommendations...

This setup will be for my Nissas Xterra, with a box in the back, facing the back of the truck. I currently have a solo-baric (round) 8" in a small sealed enclosure (about 1 ft^3), and it just doesn't sound right (and might have a bad vc)... The 4 ohm DVC are run parallel, and are being pushed with a JBL BP300.1 mono amp rated at 300 W RMS @ 2 ohm. I bought the 10" because I felt I needed just a little more volume range. I listen to just about everything BUT country, and am looking for a good sub that will give me good, balanced low end, but not necessarily win me any SPL contests. I'm looking for good, not loud or "boomy".

I have set up 4 projects and have been playing around and comparing them. Below are download links to the projects and the driver file if you want to play along, and below that is the Transfer Function Magnitude graph. The colors for the graph are listed with the projects below...

Custom Driver File for S10L5 D4 : <Here>

Project 1 (yellow) - Sealed box, settings left where WinISD put them : <Here>

Project 2 (green) - Vented box, settings left where WinISD put them : <Here>

Project 3 (lt blue) - Sealed box, setting at Mfg recommended max : <Here>

Project 4 (blue) - Vented box, this is the one I have played with and am thinking about building : <Here>

Now, after looking at this, and playing around, and reading the forums, and searching the web, it seems to me that the BLUE line (project 4) looks pretty darn good... Am I on the right track here? I've played with the ports, and the size and the tuning freq, and as far as I've read, I'm looking for a response that is as flat as possible. This one seems really flat compared to the others...

So does this graph tell me "for sure" that this is the box to build? Are there things that may not be shown by the graph that I should be aware of? I'd like to get some feedback before I start building, so any and all info would be appreciated...

Thanks,

Ben

Be sure to consult the cone excursion graph.  Read my WinISD topic stickied on this forum for details.  kfr01 has provided input about this in addition to what I wrote.  I suspect there may be the possibility of overexcursion with that alignment you show in blue.  The default vented green line response also is a likely candidate for overexcursion.  You have to consult that chart with all vented designs.

Otherwise, flat on a graph doesn't necessarily relate to flat in a car environment.  Because cabin gain fills in db in the lower octaves, the graph representation shown with the green line above should, in many environments, actually look closer to your blue line in a real-world scenario.  

Sealed subwoofers have an actual in-car low end output that defies the graph representation...due to cabin gain.  Don't make the mistake of building too much low end into your vented sub.  The addition of the cabin gain may create too much low end response.

Also check the vent length needed to achieve these reponses.  Drivers that model as "best suited for sealed enclosures" usually  need extraordinarily long vent lengths to achieve a halfway decent response.

Cool. Thanks for the reply... I did look at the cone excursion graph, and read a little about filters for that. Wasn't sure if that was common or not...and the port was pretty long, and I was looking at running it in a baffle type configuration...

I'm starting to wonder if I'm going about this the right way... I'm sure the Mfg recommendations are there for a reason.

Ben

dollarlongnecks wrote:

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I'm starting to wonder if I'm going about this the right way... I'm sure the Mfg recommendations are there for a reason.

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No mfg's specs are there for people that are too stupid to do what you are doing.  Seriously you can do wayyy better with WinISD.  You will find constructing boxes with WinISD will give you incredibly good results.  I appauld you effort here and seriously encourage you to continue.  You are definately on the right track.

You can check the excursion against the xmax of your t/s parameters.. with 2 cubic feet for a single 10 you might have some issues.

dollarlongnecks wrote:

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and am looking for a good sub that will give me good, balanced low end, but not necessarily win me any SPL contests. I'm looking for good, not loud or "boomy".

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If I were you, I'd probably drop the box down to about 1.25 cubic feet and port it a bit lower, maybe about ~35hz.  You'd get the same curve without the risk of overexcursion...  and big huge boxes like that do sound boomy.

dollarlongnecks wrote:

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So does this graph tell me "for sure" that this is the box to build? Are there things that may not be shown by the graph that I should be aware of? I'd like to get some feedback before I start building, so any and all info would be appreciated...

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I think you need to keep your box size in line with the mfg's recommendations, but  you certainly do want a curve that looks as close to this as possible.

stevdart wrote:

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Otherwise, flat on a graph doesn't necessarily relate to flat in a car environment. Sealed subwoofers have an actual in-car low end output that defies the graph representation...due to cabin gain.  Don't make the mistake of building too much low end into your vented sub.  The addition of the cabin gain may create too much low end response.

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This is a technically correct statement but I disagree in terms of context... I've had the best results mimicking that flat curve as closely as possible..   I would encourage our OP to try the flattest curve first (the flattest curve he can get out of ~1.25 cubic feet that is), before worrying about something not particularly quantifiable, like bottom-end reinforcement.. with a single 10, the woofer is not going to get "too much" low end response anyway.

Well, I was about to call it quits and just build the largest mfg spec sealed box, but after reading your recommendations, I decided to play around with the size and freq and see what I could come up with. The grey line below is pretty much right to sedate's recommendations. It looks like it mimics the WinISD recommended sealed box quite well (the yellow line). Does this mean I can expect this design to act similar to a sealed enclosure?

It looks like the excursion gets to about 5 mm past xmax at 20 Hz, and all of the ported designs I have played with seem to be very close to eachother. Is this a situation where I would need to consider a sub-sonic filter?

This smaller size should alse be easier to deal with. I was getting worried that the box would take up half the back of my truck...

Thanks again for the help. Hopefully I'll be able to start putting this together next weekkend. BTW, since this box will be ported, do I really need to use 3/4 board? And can I use something like masonite to build the ports?

dollarlongnecks wrote:

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The grey line below is pretty much right to sedate's recommendations. It looks like it mimics the WinISD recommended sealed box quite well (the yellow line). Does this mean I can expect this design to act similar to a sealed enclosure?

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Hmm.  Can't say I'm 100% thrilled with the grey line but it doesn't look terrible.

Okay... if you look at these lines (yellow and grey) acoustically.. they actually look quite different.  The grey line is running +/-3db from about 30-100hz... granted the curve looks a bit steep but in terms of subwoofers that really is a reasonably flat response.  Furthermore, in terms of subwoofer frequencies, while the yellow line does have a similar shape, the response drops off at a significantly higher frequency... down 6db from its peak frequency all the way up at 50hz.  These two curves/enclosures will not sound anything alike at all.

From this point, I'd try to bring up the 30hz intercept a up a db or two... try porting a bit lower than my original recommendations .. maybe ~28hz or so... I wouldn't go with a box larger than 1.25 cft. 

dollarlongnecks wrote:

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Is this a situation where I would need to consider a sub-sonic filter?

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Looking at those graphs, they all look like excursion jumps considerably around 30hz or so.  You might have a subsonic filter built into that amplifier (lots of sub-amps come with an undefeatable sub-sonic filter at 30hz or so).. you should check your owners manuel.  What is the xmax of that woofer you are using? 

dollarlongnecks wrote:

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since this box will be ported, do I really need to use 3/4 board? And can I use something like masonite to build the ports

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I always use 1/2" MDF and fiberglass resin to make my boxes.  I hate 3/4" MDF and I never use it... impossibly heavy.
I've heard the word masonite but I don't actually know what masonite is and I'm too lazy to look it up.  I always use PVC piping to construct my ports.  Slot port boxes are aggravatingly huge.  Try calculating your ports for 1" PVCx3 or x4 ports.  *REALLY* easy to build that way (bore the MDF out with a 1.25" paddle bit and shove the pipe in the hole, seal with silcone) and the ports stay nice and small and low volume.  You might want to sand around the edges of the pipe ... just round them off ever so slightly so they don't whistle.

OK, so I went back and looked, and I actually had the freq at 37 Hz, so I've been playing with it, trying to flatten it out a bit. Because I'm still a little confused about how the graph should actually look, I did a range of frequencies and charted them all together. Below that graph is a close up of the 30 Hz intercept.

So, I would say that the 33-31Hz range looks to be the best of the group? They both sit at about 1dB higher then the original 37Hz graph...

I've checked with my amp manual and didn't see any reference to a sub-sonic filter, so it looks like I'll probably need to find one. The xmax of the speaker is 15.1mm, and nearly all the tuning freqs are getting up above that...

And I'll have to continue to play with the ports. I'm still trying to figure out how I want this sucker to fit in the truck..

Again, thanks for the help. I'm hoping all this work is worth the effort...

dollarlongnecks wrote:

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Because I'm still a little confused about how the graph should actually look

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Well... this is sort of an open question.  The beauty of WinISD is that it tells you how to make it look like anything.  Sometimes this can be very useful.  The general application.. yours.. is to create the 'flattest' curve from ~20 ~100hz.

Here, I would tell you to concentrate on ~30 ~100hz.  I never worry about sub30hz performance...  not much music outside of electronically produced hip-hop and trance really utilizes frequencies this low and trying to shoot for good response that low without a very large diaphram is, unless you are living in a Bose commericial, *very* hard to do.  You are running a 10, the lowest range you should aim for is ~30hz.

dollarlongnecks wrote:

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so I've been playing with it, trying to flatten it out a bit.

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For reference .. *my* bar for considering a subwoofer curve 'flat' is 30-100hz @ +/-3db.

I would consider all of these curves, except the yellow line, 'flat.'

I like the '33hz' line the most, but I think if you actually built all these boxes you find they'd sound all quite similar.

dollarlongnecks wrote:

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so it looks like I'll probably need to find one. The xmax of the speaker is 15.1mm, and nearly all the tuning freqs are getting up above that...

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Hmm.   Notice that the vented enclosures you modeled began to get that jump in excursion right @ the tuning frequency.. the woofer will behave as tho it is enclosed right up until the tuning frequency, where there is a fairly large falloff in the woofer's ability to control itself.  This reinforces other reasons that I think extreamly low tuning frequencies seem to produce the best results.  If you ported right at 33hz, you'd still only have 5hz or so where overexcursion would be a risk.... and even then only at very high power levels.  You'd have to be playing a ~20hz tone at full-tilt boogie .. this is less likely than you might think.  I mean.. don't stick a tone CD in your car and try it obviously, but in terms of ... listening to music... I think you'll be fine.

dollarlongnecks wrote:

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And I'll have to continue to play with the ports. I'm still trying to figure out how I want this sucker to fit in the truck..

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I told you how to fit the port length in my other post above. Get 1" PVC pipe from Home Depot.  It costs something like $3 for 8 feet.  With a 1.25cft box, three 4" sections of pipe will produce a 33hz tune. 

dollarlongnecks wrote:

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Again, thanks for the help. I'm hoping all this work is worth the effort...

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You learned something right?

Great, I'm looking forward to throwing this thing together. Just a few last questions...

Can you give me a little info on the fiberglass resin you use for the box? Is this something you spread on the inside of the box?

And in the relation to the ports, when I look at the air velocity graph in WinISD, it looks like it is way above other recommendations I have read, which was to keep it below 110 fps. Should I try to bring this down?

And yeah, thanks sedate, I've learned quite a bit. Plus, i like all this design and planning stuff, it's right down my alley.

dollarlongnecks wrote:

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Can you give me a little info on the fiberglass resin you use for the box? Is this something you spread on the inside of the box?

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Get it at HomeDepot along with ur MDF...  the smaller size will be more than adequeate... i think its like a quart for $12.  Get an extra tube of hardner.  Get a box of disposable latex gloves. VERY IMPORTANT.  If you get resin on your skin it will not only stick worse than super glue, it will sting and itch like 10 jellyfish... the resin will eat the latex too so change ur gloves if you get any on them.  Get a couple of disposable brushes.

Anyway, its a binary liquid.. a little tube of hardner a the big tub of resin.  You mix like 1oz of resin with 1 drop of hardner, and stir.  It only comes with enough hardner for like 1/2 the tub of resin so grab an extra one while ur there.

Then paint the resin on the inside of the box.  Wait about 20 minutes or so, apply a second coat.  Repeat 3 or 4 times.  This effectively paints very durable plastic onto and into the wood... MDF is a phenomenally good substrate for resin.. very porous...  Let it cure overnight and .. viola! ... ur box is smaller and 25% lighter than a comparable 3/4" MDF enclosure.

The resin will ruin everything you get it on and everything it touches.  Completely unremoveable with anything less than sandpaper.  Handle carefully with lotsa newspaper over your work area.

Oh yea.. it smells and the fumes make gas smell like perfume.  I heard a story about a guy that stuck his head inside his box to make sure he'd gotten the resin in all the corners... and woke up in the emergency room with his head shaved hooked up to an iron lung.

dollarlongnecks wrote:

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And in the relation to the ports, when I look at the air velocity graph in WinISD, it looks like it is way above other recommendations I have read, which was to keep it below 110 fps. Should I try to bring this down

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Hmm... I think you're talking about port noise. I actually use an older version of WinISD that calls port noise 'vent mach' and it didn't have any problems with that configuration...  I really need to start using WinISD alpha that graph you have up there is neato.

I had a 12 for sometime that was in an enclosure almost identical to the one we are talking about .. 1.25 cft.. I don't remember exactly what I was trying to tune it to... something around 30hz.  Anyway I used 3 1" ports that were 4" long and I thought it sounded quite good... no 'chuffing' or any other anomolies. 

Playing with the calculator I have on my computer right now, it tells me this configuration is perfectly acceptable.. actually calculated right about to your number of 110fps.  Generally I try to keep this number below about 150..   Can you point to something that says something different?  I'd take a look.  That graph you have up there isn't something I've seen before, but it does make sense. 

I'm not sure dude.  I tried several other configurations and get the same results.. two 2 inch ports gives me the same air velocity.... so does a single 3" port... but I don't have the nifty graph and it looks like you aren't going to have problems until about 50hz or so..

Point to whatever you've read, I'd like to read it too.  Try graphing a pair of 2 inch ports against that graph above and see what comes out.  Or a single 3" port.. that looks like it would work out to about 11inches.. not unworkable really.

The information I read about the port air velocity came from stevdart's WinISD guide located <here> and copied below:

Vented enclosures, specifically

Possibly the greatest value of this program is that it will enable you to model a vented box.  Some woofers are best as sealed, others are best as vented.  The EBP tells you the story, although it's not always 100% (hint:  Solobaric wants a sealed, but everybody vents it).  The EBP, you remember, appears in the center of the 'New project' box when you first bring up the new project.  It is simply a calculation of Fs / Qes and a number is shown.  The Kappa sub we were looking at above had a 50.7 EBP, which is withing the range of a sealed enclosure.  Higher EBP's generally call for a vented box.  The program determines the best box using this EBP value by default.  But as a working tool, the program allows you to change to whichever you want.

Here is an ID sub from the program's database:  ventedwinisd.jpg  You see the picture of the sound;  there is no peak at all in the response and the low end extension is quite good, with F3 in the 20's.  Most of the reason this sub "looks" like it sounds so good is due to its engineering;  the rest is due to providing just the right mix of airspace and port airspace to the enclosure.  In the pic, you can see the vent diameter of 4" and vent length of 32". 

FAQ:  "WinISD tells me that the port has to be 32" long.  My box is only 18".  Now what?"

This is where you work the program to get the best response for what space you have available.  This box is also specified to be 2.5 cu ft.  If you don't have that much space available you have to make a change there as well.  By default, WinISD will calculate a vent opening at 4.02 inches, which in metric terms is 102 mm.  This is where almost every user of the program will have to make a change.  A larger diameter vent will equate to a longer length, and a smaller diameter vent will call for a shorter length.  Use the 'Rear port air velocity' chart that I mentioned in the beginning to see what port noise looks like:  velocitywinisd.jpg

I have my chart shown set to feet/second and specified to show RMS, not peak, output.  This pic shows a port noise of 55 ft/sec, which is great for car audio because it is 5% of the speed of sound.  You should always keep it at 10% (110 ft/sec) or less.  The vent opening area will determine this noise, so making the vent smaller in diameter will make more noise, which might become unacceptable.  If you are working along with this guide, you will have to give your sub some power in order to get a port noise response.  Select the 'Signal' tab on your working box and input the sub's RMS, or the power that it will be getting, in that block labelled 'Input power'.  Now your port noise chart will jump to attention.

So what do we do with this long port issue?  How do we get a 4" X 32" port in this box?  And what will it do to the overall size of the box?  You see that this program allows you to change to a slotted port...is this the best thing to do in this case?

The port, if inside the box, infringes on the air space.  It has to be calculated as displacement, so the box has to be that much bigger to compensate for this infringement.  I use the cylinder volume calculator on this site to figure volume for a round port tube.  If that port takes up .262 cu ft, that volume has to be added to the box volume, making it now a 2.8 cu ft box...and that's just the inside.  A round PVC port will take up less interior space than the equivalent slotted port because of port wall thickness.  Those 3/4" MDF walls normally used for slot port construction can really add up to some serious displacement.

You have to take all these things into consideration when you finally arrive at what will work for YOUR situation.  Fiddle, fiddle, fiddle.  Try to reduce the air volume and the port length grows, every time!  Make the port opening smaller and the noise grows.  In this example, if I were strapped for room, I would allow the port opening to get small enough so that the port noise chart showed me about 110 ft./sec.  Fiddle...if I change the opening to 3", the port length shrinks to 17 3/4", the net box air space is 2.5 cu ft, the port noise shows at 105 ft/sec.......and I'm happy with that.  The response looks just as great as it did in the first pic and I won't hear the port noise in the car.  Done.  Build it.

Thanks for the info on the resin, that should work out well. I'll continue to play with the port size and placement, I want to make sure I get this right the first time...

dollarlongnecks wrote:

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It sounds awesome... It's really quite a bit better than I thought it would be.

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Woot! 

I'm glad I could help..!