# Bandpass Build - SQ -- Is it possible?



## mattyjman (Aug 6, 2009)

I have an interest in exploring bandpass enclosures, but I've always been under the impression that 1.) they are really tough to implement correctly, and 2.) not really built for SQ implementations. 

Am I wrong here?

Can i get a loud but clear and defined transient response? 

What considerations need to be made when looking at this type of enclosure? 

How do I model it? WINISD?

Thanks for the help.


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## BigRed (Aug 12, 2007)

I had pwk build me a band pass and it's the smoothest sub I've had in my truck. He will design it based on your dimensions, design goal, and vehicle. It was like 35 bucks for the design. Well worth it. Be warned, he is not the fastest in the world getting them back to u but it will be solid


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## mattyjman (Aug 6, 2009)

^ how did this compare to your w15's ported? loss of sq at all?


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## Bayboy (Dec 29, 2010)

BigRed said:


> I had pwk build me a band pass and it's the smoothest sub I've had in my truck. He will design it based on your dimensions, design goal, and vehicle. It was like 35 bucks for the design. Well worth it. Be warned, he is not the fastest in the world getting them back to u but it will be solid


In one of his vids he explained that his designs may not be what you had originally in mind, but would perform in the way you desired. Did you strictly request a bandpass or did it just happen to be his choice of an optimal design for your vehicle?

Sent from my SCH-I500


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## pocket5s (Jan 6, 2012)

mattyjman said:


> I have an interest in exploring bandpass enclosures, but I've always been under the impression that 1.) they are really tough to implement correctly, and 2.) not really built for SQ implementations.
> 
> Am I wrong here?
> 
> ...


#1 implement as in design? certainly more involved than basic sealed or ported that's for sure.

as for point #2, ask Scott Buwalda  He has 4 I6SW woofers in his G35 in a 6th order bandpass. I have a single I6SW in a 6th order as the center console of my truck. Coincidentally both of our boxes were designed by PWKDesigns. I didn't ask for a 6th order BP BTW, I just said "here is my space, here is the frequency response I want and the music I listen to" and told him any number of HAT woofers to fill that need. A single 6 is what he came up with. Doitor did the same thing and ended up with two 8's in a transmission line.

The outside dimensions of mine total 2ft^3, but that was for my specific requirements. Just guessing at Scott's G35 I'm sure his 4 6's are taking up not a whole more than my single.

I requested a frequency response of 40-60hz and anything outside that was bonus. I got flat from 45hz-68hz with a bump at 38hz and about 75hz, but I cross it over at 60.

I imagine Scott's requirements were far more SQ oriented than mine were, it just so happened the same style of BP fit for him as well. 

While I personally love playing with numbers and designs, I'm glad I spent the money to have mine designed for me. You never know, in your particular vehicle with your subs and your listening requirements, a BP box may not be optimal. Maybe it's a transmission line or a tapped horn or even a basic sealed. 

As BigRed mentioned, pete isn't the fastest in delivery. I paid for the rush service (7.50) and got my design in about 2 weeks. There is a "white" service that I've heard about where you get to the top of the list for like $80 extra but don't quote me on that.


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## pocket5s (Jan 6, 2012)

BigRed said:


> I had pwk build me a band pass and it's the smoothest sub I've had in my truck. He will design it based on your dimensions, design goal, and vehicle. It was like 35 bucks for the design. Well worth it. Be warned, he is not the fastest in the world getting them back to u but it will be solid


price has gone up a bit since then. that or you got a discount  I also paid for the response graph and "rush" service. total was $65 for me.


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## Complacent_One (Jul 2, 2009)

As far as bandpass is concerned with its relation to SQ. I found that two of best sounding prebuilt subwoofer solutions happened to be bandpass. Both of them were produced by Impact back in the 90's. Their Planar-ISO-Bandpass truck box was off the chain, and played relatively flat from about 38Hz-65hz or so, and would fit behind the seat of a truck...that was pretty unheard of!! The second, was actually one of the best enclosures I had heard overall. It was also produced by impact...it was an Free-Air bandpass. If I remember right, it was 3 or 4 db down @ 20hz with a bump at 30 and 70, but relatively flat from 35-60...Pipe organs with that were pretty intense. Very little rattle from the trunk with no additional sound deadener in my 94 civic coupe.

Short answer...with the correct driver choice and proper design, I am pretty sure that you would just need a bit of eq to get some great incar response, plus a decent bump in efficiency to keep up with an HLCD front stage.


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## BigRed (Aug 12, 2007)

I asked for a bandpass box because I wanted to increase the efficiency in the frequency band I would be utilizing.

I may have paid more, it was last year that I had the design made.










please be advised that you will not receive your design fast. my only knock to PWK


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## nubz69 (Aug 27, 2005)

One of the best sounding cars I have ever heard used 2 differently tuned bandpass enclosures. I was considering doing something like this myself but my trunk space is limited and I use it a lot, so I am sticking with sealed.


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## mattyjman (Aug 6, 2009)

so consensus is that bandpass will work for me if designed properly


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## BigRed (Aug 12, 2007)

^^ yes!


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## Bayboy (Dec 29, 2010)

mattyjman said:


> so consensus is that bandpass will work for me if designed properly


I'd submit a order to PWK and see what he comes up with. May or may not be exactly what you think is best. If you want a bandpass regardless, then I suggest fiddling around with some software to see what the results would be (if you know your car's acoustics).

Sent from my SCH-I500


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## mattyjman (Aug 6, 2009)

Looks like these play a fairly limited passband.. is it possible to get something with a flat response from 80 to 30 hz or so?

Also, whaat specs should i look for in a woofers that would do well in a small bandbass box?


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## mattyjman (Aug 6, 2009)

^ anybody?


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## cubdenno (Nov 10, 2007)

I also ordered an enclosure design from PWK for my TC3000 15. I asked for flat in car response 30-70 hertz for my car with maximum efficiency and gave him the amp I was using, and the main music I listen to. I also told him I might upgrade from the 1500 to the 3000 sundown amp. I haven't needed to. He designed me a single reflex bandpass (sealed chamber firing into a ported chamber. In car, it's flat. No ridiculously bloated low end. Musical and loud. Just what I wanted


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## Bayboy (Dec 29, 2010)

The response depends on what driver you use and how much space you are willing to give up. All are connected. Flat may not necessarily be good. You may want flat in the car, but may mean an augmented response to achieve that. The main thing you will need to know is your car's acoustics before you can make any assumptions unless you have a fairly powerful EQ to tailor it afterwards. Personally, I would take a chance on PWK. I haven't heard any bad reviews on any of his designs so far. If he deems you don't need such a complex design then why continue on with it?


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## Patrick Bateman (Sep 11, 2006)

mattyjman said:


> I have an interest in exploring bandpass enclosures, but I've always been under the impression that 1.) they are really tough to implement correctly, and 2.) not really built for SQ implementations.
> 
> Am I wrong here?
> 
> ...


Hornresp is the best program for modeling bandpass boxes. It factors in a bunch of things which are very important in bandpass boxes. Basically in any box with a port, the efficiency and frequency response will vary wildly depending on the length and diameter of the port, where it's located relative to the woofer, and whether or not the port is straight or flared.


Single reflex bandpass boxes are fairly complex; dual reflex boxes are insanely complex. I would argue that the main reason that a lot of BP boxes sound like **** is that they're very easy to screw up. This is true with any box that has a port, but it's not as obvious in a vented box because the vent is only radiating in a narrow bandwidth, whereas a bandpass box radiates over 1-3 octaves.

Single reflex bandpass boxes are arguably the best solution for very low bass in a car. This is for three reasons. First, sealed boxes are more efficient at very low frequencies than vented boxes. (if you're curious why, check out John K's articles on room pressurization.) So for a given box size, sealed boxes will generally give you the most bass in a car at very low frequencies. Second, single reflex bandpass boxes and sealed boxes are the same thing - the only difference is that one has a chamber that rolls off high frequencies and reduces excursion.

The third reason that single reflex bandpass is so good in a car is that the coupling chamber reduces distortion via two mechanisms. First, the chamber rolls off high frequencies, and that reduces 2nd and 3rd order distortion. Second, at the tuning frequency excursion is reduced, and this reduces distortion.


If you're very very clever, it's possible to get very very good transient response from a dual reflex box, but you REALLY gotta know what you're doing. If transient response is important to you, I'd probably look at sealed boxes and tapped horns first; if you tweak the variables it's possible to get very good phase response out of both.

As for the choice of woofer in a single reflex bandpass, that's easy. Just use one that's suitable for a sealed box. Then tune the front chamber to the Fb of the sealed box, and tweak the volume of the chamber to increase or decrease bandwidth and efficiency. Bigger chamber in the front gets you more gain, but also reduces bandwidth.


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## Patrick Bateman (Sep 11, 2006)

Oh - one last thing.

If you want to see some really well done bandpass boxes, check out the boxes that Kef did in the early 90s.

Kef used relatively small drivers and VERY large ports. IIRC, they used two eights in their reference speaeker, with an 8" port. The woofers are physically bolted together to prevent vibration.

This makes a big difference in a bandpass. Big ports help a lot.


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## chithead (Mar 19, 2008)

Could you do a high excursion driver in a single reflex bandpass? Like, a 12W7?


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## Bayboy (Dec 29, 2010)

Yes, if you can handle the required port area which may make the build even more complex. I loathe big boxes.

Sent from my SCH-I500


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## Patrick Bateman (Sep 11, 2006)

chithead said:


> Could you do a high excursion driver in a single reflex bandpass? Like, a 12W7?


Sure, why not?

But for my money, the best reason to do single reflex bandpass is to get low bass out of relatively small drivers.

Bandpass box size will *always* be larger than the equivalent sealed box, because of the coupling chamber.

But excursion will be lower, so if the voice coild can handle the abuse, small woofers start to look pretty good in a bandpass.

The main reason I always use small woofer in most of the weird boxes that I build is because box size tends to get out of hand in a hurry with all of these weird alignments. Even if you use an 8" driver it's pretty easy to end up with a box that will fill up the trunk.


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## thehatedguy (May 4, 2007)

Or you can forgo the ports and use a passive radiator.

Should be noted that Dr. Geddes's home subs are bandpass designs. Single reflex. They used to have ports but he is using a PR now.

Matty, there is a tutioral I can post up on using hornresp to do different enclosures when I get home. It's no winISD, but pretty close in terms of easy to use...and sooooo much more powerful of a program.


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## mattyjman (Aug 6, 2009)

^ please do


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## mattyjman (Aug 6, 2009)

i'm wondering how big of a bandpass box i would have to build in order to get great response from 4 type r 8's... that would be badass


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## mattyjman (Aug 6, 2009)

oh, and patrick, thanks for chiming in on this. i know you have spent a ton of time with less conventional boxes and the like...


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## thehatedguy (May 4, 2007)

Hornresp for Dum... hmm... Everyone  - Home Theater Forum and Systems - HomeTheaterShack.com


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## Patrick Bateman (Sep 11, 2006)

mattyjman said:


> i'm wondering how big of a bandpass box i would have to build in order to get great response from 4 type r 8's... that would be badass


Same size as a sealed box, plus about 50%.

Single reflex is really simple - just design a sealed box and stick a chamber in front of it, plust a port.

Check out the calculators on CarStereo.com - Car Stereo is the #1 Car Audio Online Resource

Note that if the port is too small, you can actually have *lower* efficiency than a sealed box. Which is probably why Geddes went with passive radiators instead of ports.


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## trojan fan (Nov 4, 2007)

mattyjman said:


> i'm wondering how big of a bandpass box i would have to build in order to get great response from 4 type r 8's... that would be badass


My guess would be about 2.5ft^3 to 3ft^3....This is getting interesting....You need to talk to Pete about a design...

You might also want to talk to Scott from HAT


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## mattyjman (Aug 6, 2009)

jason, thanks for the link... i'll have to dig into that later tonight

patrick, the calculator you posted is interesting...

i have a question about that though... on the calculator, it references "gain"... is this the added level of spl that the box adds over being just a simple sealed enclosure... 

so if the results come up negative, or near zero, then you might as well use a sealed enclosure?


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## Patrick Bateman (Sep 11, 2006)

mattyjman said:


> jason, thanks for the link... i'll have to dig into that later tonight
> 
> patrick, the calculator you posted is interesting...
> 
> ...


No, not at all. It simply means you can juggle the variables as you see fit. You can make the sub super efficient at the expense of low bass. Or you can make it play super-low at the expense of efficiency. Or you can get really low bass out of a small driver at the expense of box size.

Hoffman's Iron Law is still, well, "the law."

Up until five years ago I'd never tried some of the more bizarre alignments. For instance, you can seriously tune in ten dB of gain if you want. It seems hard to believe, but true. Years ago I'd read that such extreme alignments would cause the woofer to blow up, but I've never had a problem.

One of the stranger things about bandpass boxes in the car is that you can 'cascade' cabin gain to widen the bandwidth and improve transient response.

Here's how this works:

Let's say you have an 8" woofer that has an F3 of 40hz in a sealed box, and an efficiency of 87dB. Your basic sealed box right?

Now you take that same woofer, and you increase the efficiency by six dB by putting it in a bandpass box that's very small. So now the F3 has been 'pushed up' to 60hz, but efficiency has gone up too. Now it's 93dB efficient. So you've traded efficiency for low bass. *Better yet, power handling has gone up and box size has gone down.* (Because small boxes always handle more power than big boxes, because the smaller volume of air acts as a more powerful spring against the cone.)

Now the cool part, you put that bandpass box in a car, and cabin gain 'kicks in' and drops your F3 down to 40hz, maybe even 30hz AND the rolloff is slower.

By the way, this is exactly how Bill Fitzmaurice's autotuba works, and it's very effective. Theoretically the box is 'a horn' but it's so small it's more like a bandpass box with a really efficient port. 









See how it's really an 8" woofer in a very small box with a very big port?

Of course all of this trickery is time consuming, because you need an SPL meter or at least one of those RTA apps for your phone, and you need a $100 Dayton WT3 to verify that the impedance curve isn't tuned wrong.

That last part is critical - it's really easy to tune the port wrong, and that will cost you efficiency.


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## mattyjman (Aug 6, 2009)

^ what does the impedence supposed to look like if it's tuned right...? is there supposed to be a spike at the tuning frequency of the port? 

otherwise, the efficiency of the box is lost?


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## ErinH (Feb 14, 2007)

alright, I'm retarded...

why must a 6th order box be used? Can you not simply use your active filters to filter what the bandpass would in a sealed alignment?

IOW, what is the benefit of this bulky box over a sealed one with active crossovers that allow you to fine tune the final product rather than be limited to the enclosure's influence?

I'm serious. I know... I'm a nooB.


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## mattyjman (Aug 6, 2009)

^ is this a loaded question ?


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## ErinH (Feb 14, 2007)

Absolutely not. 

I'm never afraid to ask a question. Even if it makes me look stupid. 

I'm serious though. I thought bandpass was good when you didn't have a means to control the driver via electronic filters. So, I'm just curious what it is I'm missing out on. 


Sent from my iPhone. Pardon the grammar.


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## Bayboy (Dec 29, 2010)

bikinpunk said:


> Absolutely not.
> 
> I'm never afraid to ask a question. Even if it makes me look stupid.
> 
> ...


 Greater tradeoffs between bandwidth & efficiency.... Like Patrick state before, it's most impressive when using smaller drivers (10", 8" & even a 6.5"). The 8" is my all time favorite. Built properly and you won't dare believe what size woofer is pushing that amount of sound.


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## thehatedguy (May 4, 2007)

Bandpass also reduces distortion.


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## mattyjman (Aug 6, 2009)

okay, i modeled the box, with 4 type r's with the calculator that patrick posted on carstereo.com ... gave me 1.6 sealed, and .8 vented, with a 54hz vent...

i don't remember exactly what specs as i don't have it open right now, but one thing that i do remember that threw me off, is when i used the port calculator, it suggested a 8" diameter port something like 40" long...

isn't that a bit odd?


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## thehatedguy (May 4, 2007)

Cause the ported chamber is so small.

2 15" 700 gram AE PRs would tune the front chamber to the same frequency.


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## mattyjman (Aug 6, 2009)

unfortunately i don't have the room for 2 15" passive radiators...

how do i get the port down to a decent size?


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## chithead (Mar 19, 2008)

Won't a smaller port diameter reduce the length? But may introduce port noise... especially with four subs. Hmmmm...

What about multiple smaller ports?


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## BuickGN (May 29, 2009)

I had two 12W6s in a bandpass before I went IB. The only reason I went IB was to save trunk space. I loved that setup. Transient response was out of this world. Excursion was unbelievably low at high SPL. It wasn't terribly big. The sealed chamber was 1.2 cubes which was just big enough to fit the subs. They were literally touching each other and had less than an inch behind the magnet. Front chamber was 1.8 cubes and it was vented through the skipass.

Here's the one I copied...

http://i25.photobucket.com/albums/c81/s14biggs/roughenclosure.jpg


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## mattyjman (Aug 6, 2009)

would someone mind helping me out here... i'd like to spend my weekend off building a box, but i feel a little lost. i looked at hornresp and that confused the heck out of me...

can someone model this for me, and let me know what the internal volume, ported volume, and port size(no more than 15" long) for a bandpass box? if i can get flat response from 30 - 80 hz, that would be fantastic

it may be a lot to ask, and i would be willing to compensate for the work if its fairly indepth... the urgency is in the goal to build tomorrow.

please help?!


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## cubdenno (Nov 10, 2007)

Tuning higher yields better efficiency and a flatter response in the area you are wanting "in car". My 15" sub in the single reflex is tuned to around 70 hertz. Was not what I was expecting from Pete. But in car it is awesome. And it sounds so dang good. That might allow you to keep port size down.

Also remember to mount the magnets in the ported side. This was from pete. Not sure the power you will be pushing but the sealed side with the motors mounted there has no air exchange for the heat to escape.


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## trojan fan (Nov 4, 2007)

mattyjman said:


> the urgency is in the goal to build tomorrow.
> 
> please help?!



Patience grasshopper!!!!...all good things take time...You need to talk to Pete and get his opinion....remember one step forward two steps back....measure twice cut once....There is a fine line in getting this box designed for the type output you're looking for


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## mattyjman (Aug 6, 2009)

^ how much harder is building this type of box then making sure you get the internal volumes right? 

what am i missing here? people say these are really tough to build, but if i know sealed volume, vented volume, port diameter and length, then i can play with dimensions and figure out how to build it. 

i figure i'm going to wait probably a month to get the box design back from pwk... in the meantime i cna build a different enclosure, compare the two and keep the one i like best. plus it allows me to finish and get tunes in my car quicker... after all it's only wood.


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## Bayboy (Dec 29, 2010)

The main issue is because of the added filtering, matching the car's acoustics is very important depending on what you are trying to attain. Too often people obsess about low F3hz points when sometimes that is what actually causes "one note" subs. That is an aspect that PWK seems to focus on and it does make a big difference if you ever played with different subs in different designs. If you aren't confident enough to go it alone, then I suggest waiting on PWK to avoid rebuilds.


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## mattyjman (Aug 6, 2009)

i don't think it's a matter of confidence, i was just hoping to get an answer since i can't seem to figure it out. 

here's food for thought... since i have a convertible top, should i be modeling this speaker with cabin gain?


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## BuickGN (May 29, 2009)

JL designed one for me for free. Almost perfectly flat from 30-80hz. There was nothing above 90hz. Maybe you can call the speaker manufacturer. The only info I gave them was the ski pass cutout and the frequency range I wanted.

I know port tuning is way different. I believe mine was tuned around 70hz (going off of a bad memory) which sounds crazy but it played flat and went pretty deep. I don't know how that works but it's a bit different than what we're used to with a traditional ported setup.

I knew nothing about audio at the time but I made an adjustable port that could extend out the existing port. All it seemed to do is limit efficiency in the upper frequencies.

The efficiency was surprising, it was much louder watt for watt than my ported box.


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## Bayboy (Dec 29, 2010)

mattyjman said:


> i don't think it's a matter of confidence, i was just hoping to get an answer since i can't seem to figure it out.
> 
> here's food for thought... since i have a convertible top, should i be modeling this speaker with cabin gain?





No. Albeit there would be a small amount of change from the sub being in the trunk, it depends on how it is implemented into the vehicle. Personally, I would vent the sub directly through a ski-pass or rear deck if possible. With that the trunk will not matter as sound will only be presented into the passenger area.

Being in an convertible, I wouldn't worry about trying to get gobs of extension below 45hz. Depending on the artist you listen to, most common genres are centered upon 60hz for deep bass. Doesn't sound like much, but you would be surprised. 

In fact, I really suggest you contact PWK (if you don't mind paying). It really would be interesting to see what design he would come up with for a convertible.


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## mattyjman (Aug 6, 2009)

venting through the skipass is the only reason why i'm looking at bandpass in the first place... 

you are really pushing pwk... i get it, he designs great alignments... he also take a long time. 

i was hoping someone could give me numbers so we can build something today, but i guess not. (and that's okay, i understand the whole "diy" thing...)


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## Bayboy (Dec 29, 2010)

mattyjman said:


> unfortunately i don't have the room for 2 15" passive radiators...
> 
> how do i get the port down to a decent size?




Labyrinth...


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## Bayboy (Dec 29, 2010)

mattyjman said:


> venting through the skipass is the only reason why i'm looking at bandpass in the first place...
> 
> you are really pushing pwk... i get it, he designs great alignments... he also take a long time.
> 
> i was hoping someone could give me numbers so we can build something today, but i guess not. (and that's okay, i understand the whole "diy" thing...)




Don't get discouraged. Post up some more info and see where it takes you (type of vehicle, music most listened to, etc). If you don't have a problem with measuring & measuring & cutting, then by all means skip PWK. Building a bandpass for 8" subs is not too bad. It's when you get to larger subs it gets a bit cumbersome because small is definitely not one of the benefits of bandpass. 

Play with the design you came up with, then labyrinth the port into the ski-pass. Shouldn't take long to knock a box out. Not as long as it's taking me to change out this damn pinion seal!


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## SSSnake (Mar 8, 2007)

The reason those port tuning freqs sound strange is in a 5 th order bandpass (sealed rear ported front) the port tuning is for low pass not high pass like it would be in a standard rear ported box. 

You can always mock it up in winISD and tune the port/front volume after it is in the car. Keep in mind you want consistent group delay. 

BTW - in a convertible where you are not likely to get a lot of cabin gain a 5th order would not be what I would recommend. You are likely to have too much high bass and not enough low bass (the adding of a front ported enclosure will boost the efficiency around the tuning freq). In a normal sedan 5th order is really good because you get the added cabin gain down low. In a convertible you don't.

Given all of this I would recommend 7 th order, if you go bandpass. They are quite the pain to get right. Soooooo waiting on Pete may be the right solution.


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## BuickGN (May 29, 2009)

mattyjman said:


> venting through the skipass is the only reason why i'm looking at bandpass in the first place...
> 
> you are really pushing pwk... i get it, he designs great alignments... he also take a long time.
> 
> i was hoping someone could give me numbers so we can build something today, but i guess not. (and that's okay, i understand the whole "diy" thing...)


That's why I did it, for the skipass. It got the bass out of the trunk and reduced rattles significantly. 

I wouldn't get discouraged. If you can build your own box, why not experiment. I wish I could help but unless you plan on a pair of 12W6s I've got no adivce (it was only 3 cubes which is not bad for a pair of 12s bandpassed) There are several good websites to learn how they work and the tradeoffs between tuning, efficiency, and bandwidth. WinISD will do bandpasses, not sure how accurate though.


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## trojan fan (Nov 4, 2007)

Hey Matt.....You could try shooting Jim Walters from Alpine a PM and get his opinion on what might work for you......Time is on your side unless you have some deadline


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## mattyjman (Aug 6, 2009)

trojan fan said:


> Hey Matt.....You could try shooting Jim Walters from Alpine a PM and get his opinion on what might work for you......Time is on your side unless you have some deadline


Just a self imposed deadline...... its called "i need music now"


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## SSSnake (Mar 8, 2007)

You can definitely try but like I said the 7th orders are tricky. As Patrick mentioned winISD doesn't really get you that close. For a 5th order you would likely get close enough if you were willing to tune once placed in the car. 7 th orders IMO are a complete waste of time in winISD.


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## SSSnake (Mar 8, 2007)

bikinpunk said:


> alright, I'm retarded...
> 
> why must a 6th order box be used? Can you not simply use your active filters to filter what the bandpass would in a sealed alignment?
> 
> ...


Because physical/acoustic filters increase efficiency/reduce excursion around the tuned freq. lower distortion than electronic filtering.


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## SSSnake (Mar 8, 2007)

mattyjman said:


> would someone mind helping me out here... i'd like to spend my weekend off building a box, but i feel a little lost. i looked at hornresp and that confused the heck out of me...
> 
> can someone model this for me, and let me know what the internal volume, ported volume, and port size(no more than 15" long) for a bandpass box? if i can get flat response from 30 - 80 hz, that would be fantastic
> 
> ...


IMO it is time better spent learning hornresp right now than making sawdust.


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## trojan fan (Nov 4, 2007)

SSSnake said:


> IMO it is time better spent learning hornresp right now than making sawdust.


2x...exactly!!!!.....get all your ducks in line before you move forward with building the box....try to stay away from the repeat performances

Just build something simple and temporary for now until you nail down the exact design you are looking for


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## thehatedguy (May 4, 2007)

What kind of physical constraints are we dealing with?


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## Jroo (May 24, 2006)

I have had several bandpass, all were 4th order. They certainly can be sq, but it is all in the design or rather who designed it. Many of the 4th order designers you see on many forums are very good at getting more of a "spl" out of their bandpasses. They are very loud, sometimes very peaky. When you hear someone say I heard a bandpass and it sounded like crap, they usually listened to one designed this way. The design gets tougher when you want more of sq sound or flat repsonse. It certainly can be done, but not everyone can design it that way. PWK does great work, but just be aware your design more than likely will not end up being a bandpass, which is fine. Based on your woofers and goals bandpass may be shooting yourself in the foot.


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## Jroo (May 24, 2006)

Does anyone happen to have pics or specs of Scott Buwalda's bandpass for 4 I6SW? I have heard about it but never really seen it. I have been looking at the new 6.5 subs from DD and would like to try a 4th order or a 6th order for 4 of them depending on the specs. I want to see Scotts to get a rough idea of size for multilple 6 inch subs.


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## rcurley55 (Jul 6, 2005)

Jroo said:


> Does anyone happen to have pics or specs of Scott Buwalda's bandpass for 4 I6SW? I have heard about it but never really seen it. I have been looking at the new 6.5 subs from DD and would like to try a 4th order or a 6th order for 4 of them depending on the specs. I want to see Scotts to get a rough idea of size for multilple 6 inch subs.


Try here:

New Project Car to Introduce: Scott's G35 - Page 10


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## pocket5s (Jan 6, 2012)

Jroo said:


> Does anyone happen to have pics or specs of Scott Buwalda's bandpass for 4 I6SW? I have heard about it but never really seen it. I have been looking at the new 6.5 subs from DD and would like to try a 4th order or a 6th order for 4 of them depending on the specs. I want to see Scotts to get a rough idea of size for multilple 6 inch subs.


as you eluded to, design is key. In looking at the enclosure in Scott's G35 compared to my enclosure for a single I6SW, his takes up maybe 50% more room than mine. And he has 4 times as many woofers. Ironically both of ours are 6th order too. 

Mine takes up a total outside dimensions of about 2ft^3. But I'm sure Scott's was aimed for a more flat response and his is in a sedan while mine is a truck. That's one thing I think really makes PWK stand apart is he takes the vehicle into account as well as what your goals are.

EDIT: looking at the pics again and doing some rough reverse engineering it looks like his enclosure is roughly 3.5ft^3 internally. Maybe 4, but certainly not more than that, unless there is some funky mirror effects going on that I'm not seeing.


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## Patrick Bateman (Sep 11, 2006)

bikinpunk said:


> Absolutely not.
> 
> I'm never afraid to ask a question. Even if it makes me look stupid.
> 
> ...


Ten reasons to use a bandpass box:


Due to Hoffman's Iron Law, a sealed box and a bandpass with the same bandwidth will have the same footprint and efficiency. In other words, the myth that a bandpass needs a huge box is not true. You simply need to use a smaller woofer, because you can make it play lower in a bandpass. IE, if you were going to use a 12" woofer in a sealed box, you might consider a 10" for a BP.
The excursion at the tuning point is basically nil. So if the voice coil can take it, you can get realllllllllllly loud. This assumes you have a LOT of power. If you don't have a lot of power, I'd probably think twice about BP.
The port and coupling chamber reduce distortion.
You can move the source of the sub, without moving the sub. For instance, you can move the port to the rear deck, where standing waves may give you more gain than they would in the trunk. This can make a significant difference; as much as doubling or even quadrupling amplifier power.

I've been on a 'phase' kick lately, and the group delay and phase curves of all the augmented alignments are kinda scary. It's something to consider if you're building these boxes.

Oddly enough, if you juggle the location of the port, it's possible to get group delay and phase response that's *superior* to a sealed box with some of these strange boxes. It really takes a lot of time in front of hornresp but it's doable.

I think the point above may explain why the Th-Mini is still my favorite sub. It has a very nice group delay curve.


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## Patrick Bateman (Sep 11, 2006)

BigRed said:


> I asked for a bandpass box because I wanted to increase the efficiency in the frequency band I would be utilizing.
> 
> I may have paid more, it was last year that I had the design made.
> 
> ...


That's a tapped horn 

Back loaded horns, vented boxes, tapped horns and dual reflex bandpass are all points on a spectrum, and PWK keeps selling these tapped horns and calling them bandpass. I guess to avoid copyright infringement with Danley Sound Labs.

Actually, on second thought, this could be considered a dual reflex bandpass subwoofer with a port that's series loaded into the front chamber. The difference between BLH, TH, vented, and bandpass is that the latter two are tuned to the helmholtz resonance, and the former two are tuned to the quarter wave resonance. The quarter wave boxes generally have less group delay.


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## pocket5s (Jan 6, 2012)

Patrick Bateman said:


> That's a tapped horn
> 
> Back loaded horns, vented boxes, tapped horns and dual reflex bandpass are all points on a spectrum, and PWK keeps selling these tapped horns and calling them bandpass. I guess to avoid copyright infringement with Danley Sound Labs.


It is? It looks like a 4th order, or a 6th order BP with a really short port (part that goes into the cab of the truck). 

I'm certainly no expert but every tapped horn I've seen the horn portion doesn't drop dramatically in cross section like this one does and then expand again, i.e. where the port looks to be on the left side of the pic, then going into the common chamber. They are either constant or tapered, like what you would think of a "horn" looking like, albeit usually folded.

I'd be curious if PWK actually calls them anything other than an enclosure. He's mentioned specific designs in videos, namely transmission lines, but never said what mine actually was, even after I asked  is "band pass" trademarked?


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## Patrick Bateman (Sep 11, 2006)

pocket5s said:


> It is? It looks like a 4th order, or a 6th order BP with a really short port (part that goes into the cab of the truck).
> 
> I'm certainly no expert but every tapped horn I've seen the horn portion doesn't drop dramatically in cross section like this one does and then expand again, i.e. where the port looks to be on the left side of the pic, then going into the common chamber. They are either constant or tapered, like what you would think of a "horn" looking like, albeit usually folded.
> 
> I'd be curious if PWK actually calls them anything other than an enclosure. He's mentioned specific designs in videos, namely transmission lines, but never said what mine actually was, even after I asked  is "band pass" trademarked?


If you're not selling the box, you can build any of them.

PWK is selling the designs, so he's limited to the following:

front loaded horn
back loaded horn
single reflex bandpass
vented
sealed

I'd say that a transmission line is arguably a BLH with a reverse taper. Danley used to mess around with transmission lines before he switched over to 'real' horns.

These designs are off-limits:

tapped horn (danley sound labs)
dual reflex bandpass (Bose)
triple reflex bandpass (Bose)

Interestingly, Bose has stopped doing both of their patented designs, and they now sell back loaded horns AKA transmission lines.

I can only guess why, but I'll bet they figured out that bandpass boxes are *incredibly* sensitive to driver parameter problems. In other words, if Bose gets a batch of woofers from China where the parameters are off by 10%, it can change the efficiency and response of a bandpass by a noticeable amount, particularly on their crazy-ass triple-reflex boxes.

tapped horns are pretty forgiving of parameter drift because there's no back chamber, no front chamber, and the 'port' is basically the entire enclosure.


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## thehatedguy (May 4, 2007)

I think it is a series tuned 6th order.


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## Oscar (Jun 20, 2010)

thehatedguy said:


> I think it is a series tuned 6th order.


I agree. The rear chamber is ported into the "front", which just happens to bbe shared by both drivers.

One thing to keep in mind when setting the port specs is what was mentioned in this thread as a 'labrynth' port, aka a shelf or slot port. When a slot port shares 3 of it's walls with the enclosure, it couples a helluva lot of additional airmass to the port airmass. In my ported box for my W10GTi, the slot port "acts" as if it was ~1.66x the actual physical length. This made using a large port area AND getting the the required Fb much much more achievable. I verified this by viewing the impedance plot with my WT3.

As far as 6th and 8th order BP boxes are cconcerned, I had read that the bose patents had expired since they were granted in 1985 or so. Anyone who is familiar with patents 'round here?


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## Bayboy (Dec 29, 2010)

While on the subject of different order bandpass, has anyone ever tried one of subsolutions' boxes?


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> I think it is a series tuned 6th order.


I'm going to make a sixth order box for my tweeters.


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## thehatedguy (May 4, 2007)

I will give you props only if it is series tuned 

Which a Unity could do with the mids if you had open basket mids and tapped the back wave into the horn.

Or a planar tweeter/mid could in theory do it as well...


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## cubdenno (Nov 10, 2007)

Off topic sort of, could one port the rear sealed chamber of a horn such as say a tuba home theater. Small sealed enclosure style. Is that rear loaded? Anyway, the Fitzmaurice tuba home theater uses a 12 or a 15. Is incredibly efficient 20-100 hertz. But was curious if one could port lower to extend the low end to say 15 hertz?


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## Jroo (May 24, 2006)

Ive seen a few bandpasses that were designed to play the very low end, but usually with a trade off. From the designs Ive seen that do this, they usually arent able to play much over 60hz. Im sure somebody has a bandpass that does 20 to 100 and I havent seen the home theater you are talking about, but most of the bandpasses I see dont have a range that wide. Even most of the sq systems using a bandpass do something like 30 to 70. I have two 4th order designs one for a set of 10's and one for an 18". The design for the 10's will do 30 to 70Hz and the 18 goes lower but really cant do anything above 60hz.


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## thehatedguy (May 4, 2007)

That's compound loading...has been going on back to the 30s to some degree.



cubdenno said:


> Off topic sort of, could one port the rear sealed chamber of a horn such as say a tuba home theater. Small sealed enclosure style. Is that rear loaded? Anyway, the Fitzmaurice tuba home theater uses a 12 or a 15. Is incredibly efficient 20-100 hertz. But was curious if one could port lower to extend the low end to say 15 hertz?


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## Oscar (Jun 20, 2010)

thehatedguy said:


> That's compound loading...has been going on back to the 30s to some degree.


Yup, one side of the driver is loaded with a horn to increase on-axis sensitivity, while the other is ported to get a few extra Hz out of the low-end. 

Unfortunately, the port contribution won't be anywhere near the horn output level from what I've experimented with on HR and Akabak. You can get perhaps an extra 5 Hz or so (of course it all depends on the actual system design), but unless you make the ported chamber big to make the resonance spike up to horn-like levels, you'll be stuck with a low-SPL port contribution just as it is from a standard vented box.


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## Patrick Bateman (Sep 11, 2006)

Oscar said:


> Yup, one side of the driver is loaded with a horn to increase on-axis sensitivity, while the other is ported to get a few extra Hz out of the low-end.
> 
> Unfortunately, the port contribution won't be anywhere near the horn output level from what I've experimented with on HR and Akabak. You can get perhaps an extra 5 Hz or so (of course it all depends on the actual system design), but unless you make the ported chamber big to make the resonance spike up to horn-like levels, you'll be stuck with a low-SPL port contribution just as it is from a standard vented box.


This is Hoffman's Iron Law rearing it's head again. You can vent the back chamber, but the port is physically small when compared to the horn, so the output of the horn swamps the port, and it's contribution looks like virtually nil.

This improves quite a bit as you use a larger port, a higher tuning frequency, or both.

One of the trippier things about vented horns and tapped horns is that you can juggle the parameters to make the boxes sound 'tighter' than a sealed box. This kinda blew my mind when I first realized it. Because typically a vented box has fairly atrocious phase response and group delay. (Which is the reason they sound 'slow' imho.)

Basically you juggle the following variables and you can flatten out the phase curve:


The output from the rear of the cone is delayed by a few milliseconds because it's 180 degrees out of phase.
The output from the *front* of the cone is delayed by a few milliseconds as it travels down the horn
The driver parameters affect this too; to be specific the qts of the driver changes the phase curve and the group delay
The location of both the horn mouth and the rear port play a part in this. For instance, if the port is close to the mouth the phase curve will be different than if the port is located on the opposite side of the enclosure.

It's a ton of variables, but it's kinda 'neat' when they all slide into place, and you end up with a phase curve that looks like a well damped sealed box.

All of the statements above apply to dual reflex and triple reflex bandpass also; after all they're both in the same family. Basically any box where the front and the rear radiate into the room.


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