Ported vs Sealed, lets open this can of worms. lol

[Eric D]

For those reading this thread and also trying to sift out all the useful info amongst the dick waving...

http://www.diyaudio.com/forums/multi-wa ... ouser.html

http://www.oocities.org/f4ier/vented.htm

http://www.stereophile.com/content/dyna ... asurements

There is a bit of extra info in those links, but you should be able to get the concepts of impedance curves and what information they convey to an enclosure designer.

[shawn k]

Can you please re-read my post except this time use an open mind about it, and don't just automatically look for ways to be right and me be wrong.

In the case you mention I would not port the box, I would run it sealed. If it is too small to be ported, then it would not make much sense to try.

Using an impedance curve to validate tuning is a technique AUDIO ENGINEERS use all the time. I don't expect you to understand it, nor do it yourself. But, if you don't understand it, that does not make it wrong.

But what if the driver doesn't lend itself be used in a sealed enclosure!?(yes that is a possibility) Building the enclosure before hand (blindly that is) with absolutely no prior information is just a waist of time. Unless that is, you just want to simplify the install and "hope" that it sounds good (like a prefab or even "recommended" designs)

So in other words, you would prefer to "hope" that you can "make the enclosure work" after it's already built. I'm sorry man, but that's really what it breaks down to.

I understand what you are "trying" to explain, and even if you "think" it's a valid option, it's not the "ideal" option. Just because you "worked for Rockford" doesn't make it right.

Oh and btw, WinISD provides you with the impedance curve for the driver in the enclosure that's being plotted...... AND IT'S FREE!!!!

[ttocs]

hey eric can you compair a "projected" impedence curve and then the real world measurement for comparison? Would love to know what kind of %err we are talking about.

[Eric D]

Can you please re-read my post except this time use an open mind about it, and don't just automatically look for ways to be right and me be wrong.

In the case you mention I would not port the box, I would run it sealed. If it is too small to be ported, then it would not make much sense to try.

Using an impedance curve to validate tuning is a technique AUDIO ENGINEERS use all the time. I don't expect you to understand it, nor do it yourself. But, if you don't understand it, that does not make it wrong.

But what if the driver doesn't lend itself be used in a sealed enclosure!?(yes that is a possibility) Building the enclosure before hand (blindly that is) with absolutely no prior information is just a waist of time. Unless that is, you just want to simplify the install and "hope" that it sounds good (like a prefab or even "recommended" designs)

So in other words, you would prefer to "hope" that you can "make the enclosure work" after it's already built. I'm sorry man, but that's really what it breaks down to.

I understand what you are "trying" to explain, and even if you "think" it's a valid option, it's not the "ideal" option. Just because you "worked for Rockford" doesn't make it right.

Oh and btw, WinISD provides you with the impedance curve for the driver in the enclosure that's being plotted...... AND IT'S FREE!!!!

Well, I would not build an enclosure without knowing what woofer is going into it. As a rule-of-thumb I put low mass coned drivers with smaller x-max in ported enclosures, and high mass coned drivers with larger x-max in sealed ones. It is just a rule-of-thumb, but feel free to use it against me as I know you will. I got this rule-of-thumb from Vance Dickason, ever hear of him?

Did I ever say my method was ideal? It happens to be the method I prefer to use, which is my opinion, nothing more. I can't say my way of doing things is any more ideal than you can say yours is, so why argue that?

Your are 100% correct, that because I "worked for Rockford" does not make it correct. However, since Rockford and EVERY other audio engineering company out there use this method, that is enough for me to consider it correct.

The WinISD impedance curve will not be representative of the enclosure in a vehicle, only open field. Not really of much use from a car audio standpoint.

[ttocs]

I would love to see the projected impedence curve, vs the open measurement(out of car) and the in-car

[Eric D]

hey eric can you compair a "projected" impedence curve and then the real world measurement for comparison? Would love to know what kind of %err we are talking about.

I am sure I could, but for the sake of time I won't. I have cut back on audio to the point where most all of my stuff is boxed up and never used. Couple that with my lack of woofers and test boxes, and it won't be happening from me.

I do know that a modeled open field impedance curve has pretty much nothing in relation to an actual tested closed field curve. Can I prove it, no I can't.

Do I even care to prove it, no I don't. I am confident that anyone who reads through this thread will get all the information they need to draw their own conclusions, and that is really all that matters to me. Proving someone wrong might gain me a bit of personal satisfaction in the short term, but presenting what I know, and having people perform their own research on it, then drawing their own conclusions, and going away knowing something they did not to begin with, is worth far more satisfaction in the long run.

[Eric D]

It is kind of a pain in the ass, but anyone with an AC current DMM and a second AC voltage DMM can get an impedance curve.

Hell, in one of the above links I posted there is a discussion of other ways to find tuning, such as port velocity peaks.

With two DMMs, one can measure the voltage and current at different frequencies (from a test CD for example), and then plot out the points by hand. This is exactly what my LMS does, it just does the work for me, and does it quickly with a sine sweep.

http://www.linearx.com/products/analyze ... LMS_01.htm

[audiophyle_247]

OK then, I have no problem amending my statement to 70% instead of 90% if it gets you and I to agree on something.

Yes, again we agree on something.

Yes you can just build a box and then port it, and tune it. There are two ways to do this. One is to calculate it. If you know the volume of the box, and you know what you want to tune it too, you can setup a formula to converge at the loss of volume from the port, along with the specs of the port getting you the proper tuning.

The other option is the one I choose. I run an impedance curve. I stick a port in the box with the cross sectional area I want (most often driven by the install itself, and how the port will look cosmetically), then use an arbitrary length. I run an impedance curve on the box with the woofer, and with it in the vehicle. This gives me the exact tuning of the enclosure. I then have to either make the port longer to tune lower, or shorter to tune higher. It is not all that difficult, and it is not all that time consuming either. The beauty is I get exact results, and I also get to use my $1,000 analyzer which otherwise does not get used often enough.

While I understand how that would work, it is a much slower method and impossible to do on anything other than a round port design. Tell me how that works with a slot vent

You can devise a formula to converge where tuning & port length will meet, however there is NO certainty or likely hood it will be anywhere close to the tuning freq you want unless the box was built huge or prior calculations were done. You are stuck at that freq being your lowest possible, whatever it ends up being, and if it's not low enough you are SOL.
There is also the fact that box volume and port freq are only a small portion of the bigger picture.
A sub in 1cuft tuned to 30hz will sound vastly different than it would in a 4cuft box tuned to 30hz, not to mention sub B can be vastly different than sub A when used in similar boxes. Just because you got an uncalculated box to your desired tuning freq still doesn't mean it's going to perform as well as it could. It also does nothing about port sizing or air velocity, so while you could technically get any box volume tuned to any freq, I doubt a sub will like that straw sized port even if it's tuned to 20hz. Even manufacturer recommended port sizes are inadequate and will suffer horribly at high volume. (further reasoning behind my avoiding them).
All of that would explain to me why you never had great results at Rockford with ported enclosures (your words in the other ported thread that started this one). Not a bad thing, just using the tools available at the time. We are all guilty of that, however I happily adopted using modeling software.

It is now obvious to me you are more into car audio than I am, as you seem to have made it your career.

And this tells how little anyone knows about anyone on the internet. While I do have a significant history of car audio and installation, it was my career. I am actually in my final year of getting my masters degree........ In Architecture
Took me a while to realize I needed a solid future. I still rely on installs to pay my bills, but after working for myself for the last 4~5 years its gonna be hard starting over & having to take orders again. Lol

You have made a very important point in this whole thread though, and it is this...

Years of doing shit wrong doesn't make you better than me at anything other than f**king shit up. (which I'll gladly give you rep for)

This is a quote I agree with 110%. You could not be more spot on. Now, I don't know you all that well, but I really hope you don't actually fall into the very point you have made.

I am now pretty sure you are an installer by trade (assuming so from your recent posts), and in my experience over the years, 90%+ of installers fall into the point you made. When you start doing something wrong from the beginning, and do it for years, that does not make it right.

I don't have respect for installers based on technical skill. Unless they have some more formal education, being taught on the job and then doing the same tasks over and over does not make them right at what they do. However, where I do have tons of respect for installers in in the realm of creativity. Some guys can build works of art nearly beyond comprehension. Their attention to detail, and the clean outcomes of their projects are awe inspiring.

Again we agree on things, and I absolutely live by that adage. That & "anyone who has never failed, has never tried anything new", by good old Albert Einstein. (that's actually my sig in my email, and several forums)
My attention to detail borders on OCD and my drive to be the best even more so.
I find it comical that you can enjoy such "works of art" and surround yourself with engineers. I find most engineers to be unimaginative and dull. (again most, not all)
I think if you were to build a box after modeling it, you would really see where your past practice had been failing you.

I read an interview with Dave "Fishman" Rivera some years ago, where he talked about how little his technical knowledge was. I am pretty sure that anyone who knows who I am talking about agrees he is one of the most creative car audio guys ever. But, being creative does not make him a technical authority.

He put an aquarium in a car, what's his other claim to fame? I think to truly create something one must have a full understanding of what they are doing; you cannot push boundaries if you have no idea where they lie. He never struck me as being a real creative person, then again none of the guys on the TV shows do either. DIYMA has some inspiring works of art though, and some of those guys are "only" hobby installers.


& correct me if I'm wrong, but unless anyone on here wants to hire someone, WTF do credentials have to do with anything important? Could Shawn's history somehow add any more truth to what he is saying? (about the topic, I don't care about the personal squabbles)
I would like to see this thread turn around, so let's all get along a bit better here. I don't want to have to bother Stipud or other mods about "trimming some fat" in this thread, but we really could do without the last 2 pages. Lol

[ttocs]

he could be richard clark, he could be dick clark, who would you expect to get better advice on audio from? When someone give instructions, advice, or help on the net it is nice to know if its richard or dick we are talking too....

Eric was pretty much spot on with his earlier guess at what his credentials are. Probably why he didn't want to post them but dunno.

[shawn k]

he could be richard clark, he could be dick clark, who would you expect to get better advice on audio from? When someone give instructions, advice, or help on the net it is nice to know if its richard or dick we are talking too....

Eric was pretty much spot on with his earlier guess at what his credentials are. Probably why he didn't want to post them but dunno.

So what you're saying is, you will only accept advice from some famous audio engineer whom would never have any intention of ever joining a "phorum"?

Well, I'll fully admit that I'm no Richard Clark, or Dave Navone, or Jim Fosgate, or Vance Dickason, or Robert Zeff or any other of that caliber. But guess what... You will never see any of those guys here conversing with us. So if those are the only guys that you will listen to (which is essentially what you're saying), then why don't you just sit back and keep your mouth shut? Is it really that important to you that you have to argue over something that you have so little knowledge of?

[ttocs]

wow, somebody sure is sore all of a sudden. Yes shawn that is exactly what I am saying if it is richard or dick clark giving the advice shut the hell up. How do you read between the lines so well?

somebody is awfull touchy he couldn't make that education or shop work and had to fall back to installing. I know it gets old after 10 yrs and takes all the fun out of your hobby when you do it full-time....

[audiophyle_247]

he could be richard clark, he could be dick clark, who would you expect to get better advice on audio from? When someone give instructions, advice, or help on the net it is nice to know if its richard or dick we are talking too....

My point is, it doesn't fucking matter who he is, it will not change the validity of his statements.
The only thing it will change is your willingness to listen, which is your own damn problem.

You question the validity of any statements here, then go do a little research of your own & come back to prove people wrong. Nothing stopping ya, so go on & drop some fact bombs of your own.

[shawn k]

somebody is awfull touchy he couldn't make that education or shop work and had to fall back to installing. I know it gets old after 10 yrs and takes all the fun out of your hobby when you do it full-time....

High class right there.. really classy man

For the record (but not that it really matters):

I "chose" to leave college in favor of becoming an installer, however ill advised you may think that decision was. And yes, I did create and open my own business only to have it go under in less than a year. I promise you that if you had even the slightest inclination how much effort, dedication, and patience it takes to single handedly open your very own business, then you would NEVER use that as ammunition to personally attack that person who has lost that business! You just have no idea man!

Finally, my hobby/carrier of car audio is by no means "old" to me. I'm not sick of it, I'm not tired of it, in fact I'm just as enthusiastic about it as I was in the very beginning! It is truly my passion, and I don't forsee that ever changing to be completely honest.

[ttocs]

didn't say it to hurt you as much as to knock you off your high horse in hopes we might see eye to eye. After reading your your experience we are not that far apart and I would still score erics exp above my own. You have been in the biz for a while and spent some time with the modelling programs but I still think you are putting too much faith in them while conviniently ignroring all those things we agree would throw the projected graph off. Its nice when in a perfect world that we can put some numbers into the pc and it just knows more about the laws of phisics then god himself and can tell you exactly how it will sound. You keep telling me to see what small adjustments can do to the graph, but to ignore all those small things that would throw it off.... You can't have your cake and eat it too. What kind of % err do you think that you get from the projected to the real-world measurements and at what point would that %err be too high?

[Eric D]

Wow, it seems I missed a lot overnight.

I will do my best to catch up.

-Slot ports. They work the same as round ones. They have a cross sectional area and a length. I don’t understand why adding or removing length on a slot port is any different than doing it on a round one? I must be missing something. Since I often use one wall of the enclosure as the edge on a slot port, it is really less work adding and subtracting from a slot than a round one.

-You can devise a formula which will be spot on. I don’t know how far they have taken you in architecture, but I am sure you have covered limit theory, and Calculus-1, which covers derivatives. Using these tools you can come up with a converging formula to calculate a port length. Now, don’t jump to any conclusions here, I am not saying everyone should go and do this. I am just pointing it out as a possible method. I personally won’t do this when I can just use an impedance curve.

-So car audio WAS your career, but it still pays the bills? Sounds like it went from a career to a job. Either way, glad to see you are moving on beyond it.

-If you have an issue with me appreciating installers creative skill, then good for you. I won’t argue you on it, and I won’t stop appreciating their creative skill either.

-As for credentials, you need to take that up with Shawn. He made the point that he would post his credentials. He used this as some sort of threat to get us to back down, as if he is some authority and we really don’t have a right to disagree with him.

-And on the topic of credentials, if they don’t matter, than Shawn needs to stop quoting famous audio people to try and prove his points. Or am I missing it, and only Shawn is allowed to use anyone’s credentials to his advantage?

[stipud]

Well this thread is going... good... ...

Scott, if you please... I don't think Eric needs you to back him up on everything. Unless you have something relevant to the topic to add, beyond arguing semantics (i.e. "you said this, I said that"), please refrain from posting. We really don't need more ad hominem in here; data keeps it interesting. Shawn and Eric, let's just drop the whole credentials thing, as well as bringing up past disagreements. You can do that in PM if you want.

For the record, I agree with audiophyle for the most part. You guys argue that modeling a subwoofer is useless, but I disagree. While you are correct that you can't model exactly what the sub will sound like in the car, without knowing the transfer function, the model still gives you a TON of good data. It's quick and easy too! You suggest using the manufacturers specs... for sealed boxes I tend to agree, but I've found that ported suggestions can be hit or miss. PG for example seems to occasionally have absolutely terrible ported box designs, such as recommending ludicrously small, chuffy port sizes (I've seen a 1.5" diameter port?? WTF). I've modeled these boxes before, and you can see that the port velocity goes through the roof near the tuning frequency, which indicates that it will probably chuff. However, you can use the recommended tuning as a guideline to make a bigger box with a bigger port, which WON'T chuff. You can even compare these boxes to each other, which is quite possibly the BIGGEST reason to use modeling: comparing boxes to each other. So you can't model exactly what it will sound like, but when comparing boxes you can see which ones will be louder at certain octaves, and this will be more or less true in the car as well, regardless of the transfer function.

[shawn k]

No problem man.

My apologies for getting out of line!

[shawn k]

And for the record, I agree with you and audiophyle about the benefits for programs like WinISD. All in all, that's exactly what we were trying portray before all of this got out of line.

[Eric D]

OK then, so back to the original point of the whole thread?

I still argue that ported boxes are not better than sealed boxes, and sealed boxes are not better than ported ones.

Each has its applications, and everyone is entitled to their own choice of going with sealed or ported.

Why am I so wrong with my beliefs on this?

[audiophyle_247]

Wow, it seems I missed a lot overnight.

I will do my best to catch up.

-Slot ports. They work the same as round ones. They have a cross sectional area and a length. I don’t understand why adding or removing length on a slot port is any different than doing it on a round one? I must be missing something. Since I often use one wall of the enclosure as the edge on a slot port, it is really less work adding and subtracting from a slot than a round one.

Then maybe I misunderstood your process, because it sounded like you build the enclosure and then tune a port for it if its big enough. How do you do that when a slot port is typically PART of the enclsoure? Do you build a box with a hole and then start adding baffles on the side to create a port? I assumed you just made a box, drilled a large hole and by altering the length of a PVC pipe fine tune the box to where you wanted it.

-You can devise a formula which will be spot on. I don’t know how far they have taken you in architecture, but I am sure you have covered limit theory, and Calculus-1, which covers derivatives. Using these tools you can come up with a converging formula to calculate a port length. Now, don’t jump to any conclusions here, I am not saying everyone should go and do this. I am just pointing it out as a possible method. I personally won’t do this when I can just use an impedance curve.

Yes, I am well aware of derivatives. I think maybe we are on different pages here. When I design a ported box, I pick the subs and then the port area necessary for the best performance without noise. Typically port areas need to be huge for the best performance and lowest air speeds at high volume. At this point, with sub & port area being fixed, you need to calculate for how much the volume decreases as your port increases and work out where that lowest freq lays on that curve. (which should be at the bottom of an upward facing parabola) In this manner, you are restricted to that lowest point as being the bottom of your tuning ability, UNLESS you start to shrink the port area as well. As you shrink port area its length (or tuning if length stays constant) goes down further, however air speeds will climb, port compression will climb, port noise increases, and distortion increases. So in my unwillingness to sacrifice performance I cannot simply rely on getting a "low enough" port freq, I need to calculate it all out ahead of time.

-So car audio WAS your career, but it still pays the bills? Sounds like it went from a career to a job. Either way, glad to see you are moving on beyond it.

Never a job, and only a career by technicality. Car audio has taken a backseat to school work, but Im still deeply involved with car audio.
More like getting paid to play, because music and building things are passions of mine. I moved on to build much larger enclosures, ones that house people instead of woofers. lol (although there are a LOT of architects who design things outside of buildings & structures) My MAA degree will open a lot of doors not just in Architecture, because it is a design degree there is actually quite a bit I can do with it.

-If you have an issue with me appreciating installers creative skill, then good for you. I won’t argue you on it, and I won’t stop appreciating their creative skill either.

You constantly refer to engineers for how things should be done right, and that mentality typically looks past "art" (form) to get to function as the priority.
Aint nothing wrong with it, and its great to be able to appreciate a work of art, I just found it unexpected.

Thank you Stipud for keeping the peace. (& agreeing with me lol)

[audiophyle_247]

OK then, so back to the original point of the whole thread?

I still argue that ported boxes are not better than sealed boxes, and sealed boxes are not better than ported ones.

Each has its applications, and everyone is entitled to their own choice of going with sealed or ported.

Why am I so wrong with my beliefs on this?

You are not wrong, and I thought I addressed this line of thought in the very first thread.
If space is not an issue, ported can offer SO much more than sealed.
The only negatives to a ported enclosure are
1. Ported can have higher group delay (BUT so will Sealed when EQ is added to bring up its performance)
2. Ported takes up more space (& this is the biggest issue)
3. Higher degree of difficulty to design & construct so it works as designed.

I have a sealed box in my car right now, I just dont love it like I do some of my ported designs, but it doesnt mean is sounds bad. (just not good enough )

[Eric D]

I think you should add one more negative to a ported box...

4. Not as "tight" of sound.

The only problem with my number 4 on your list is "tight" is pretty obscure. It is also pretty subjective. All I know personally is there is a difference in sound to a sealed box, that I generally prefer (although not all the time). My favorite set of home speakers happen to be ported, but my best set of home speakers are sealed.

-I generally decide if the box will have a slot port or a round one prior to building, and once decided, it is not changed. This would be for cosmetic reasons more than anything. In a lot of situations, certain port placement and port size does a lot for the look of the overall installation. I then work from there. I realize this is a backwards approach to doing things, but it works quite well, and since it seems most people are stuck on cosmetics as much as performance, everyone wins.

-I started college with the idea I was going to major in art, not engineering. When I finally realized I personally would not be very successful with an art degree, I switched to engineering, which was my second interest. I am sure very few engineers start out in art, so I am an exception to the rule. This has had some payoff for me in the way of industrial design. Putting engineering and art together has its uses.

[audiophyle_247]

I think you should add one more negative to a ported box...

4. Not as "tight" of sound.

The only problem with my number 4 on your list is "tight" is pretty obscure. It is also pretty subjective. All I know personally is there is a difference in sound to a sealed box, that I generally prefer (although not all the time). My favorite set of home speakers happen to be ported, but my best set of home speakers are sealed.

-I generally decide if the box will have a slot port or a round one prior to building, and once decided, it is not changed. This would be for cosmetic reasons more than anything. In a lot of situations, certain port placement and port size does a lot for the look of the overall installation. I then work from there. I realize this is a backwards approach to doing things, but it works quite well, and since it seems most people are stuck on cosmetics as much as performance, everyone wins.

-I started college with the idea I was going to major in art, not engineering. When I finally realized I personally would not be very successful with an art degree, I switched to engineering, which was my second interest. I am sure very few engineers start out in art, so I am an exception to the rule. This has had some payoff for me in the way of industrial design. Putting engineering and art together has its uses.

Your number 4 IS my number 1, lol.
Accuracy & "group delay" are essentially one in the same. & with the port tuned very low the areas with the greatest delay shift downward with the port & can actually go unnoticed if done well.

[stipud]

The tightest setup I ever owned was a ported pair of Xmax 10's, tuned to 30Hz. Same exact box on my (original) Ti10's was absolutely terrible... sloppy, slow, etc. BassBox showed a massive difference in group delay, so that's what I attributed it to. The Ti's on the other hand sounded fantastic sealed, while the Xmax 10 sealed was awfully thin sounding, lacking significantly in the lowest octave. So in my experience I agree with Eric... low mass, high tuned drivers are usually better in ported setups, while high mass, low tuned drivers are typically better in sealed. There are of course many exceptions to that rule, but in general for average consumer subs, it seems to ring true.

Personally the advantage of ported (more bass) is not something I need. In fact, even with my sealed box I turn the sub gains down to blend better with the front stage. The RSDC is designed to play nice and low as-is, and I have used my RTA to verify a near flat curve in my 1.25cuft sealed box. Porting at this point would give me more bass, which I don't need, and would throw off my flat response. So for me, in my install, sealed is the right choice.

[Eric D]

So it seems a lot of us are on some common ground for a change.

Now, I have a question regarding box modeling.

Using box modeling you can design a box for what tuning you want. However, to get a model of the system's output you need to plug in the T-S parameters of the driver used, and then compute...

Am I right so far?

Now, here is the question...

Where do you get the T-S parameters when a lot of subs don't have published specs, and the ones that do are often not correct?

I would advocate you need something like the Dayton Audio woofer tester to get these numbers, but I am more curious what you guys who are into modeling are doing.

(I am considering getting one of the Dayton Audio woofer testers for some home speaker development, and any more uses for it will justify its' cost to me)