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View Full Version : Finally porting the Tang Band 6.5's...need help/ideas



ItalynStylion
02-12-2008, 07:38 PM
I've had my current setup for a while and I've been REALLY satisfied. Right now I've got 4 Tang Bands in 1 cube sealed (pictured bellow). They sound great but they can't keep up with my Focal 165V1's and porting will help solve that :D

http://i17.photobucket.com/albums/b75/ItalynStylion/SubStuff/Sexy001.jpg



So I've run the numbers through Unibox using the following TS parameters...
Tang Band-W6 1139
Fs 38.00 Hz
Re 3.60 Ohm
Qms 2.65
Qes 0.47
Sd 140.0 cm2
Vas 12.0 l
Xmax peak 13.00 mm
(Le) 1.35 mH*(wth is LE and where do I get this number?)
(Le2) 0.00 mH
(Re2) 0.00 Ohm
Nominal Power 78.0 W



Hoping that all is accurate; let's move on to the fun stuff!

The recommended net volume is 1.7 cubes, but I've found that by increasing the volume to 1.94 I can extend my low end extension. If I tune to 34hz the response is VERY flat. Pic bellow of the FR graph.

http://i17.photobucket.com/albums/b75/ItalynStylion/SubStuff/ResponseGraph.gif

What size port tube should I use? I was thinking a 4" precision port would be fine but the chart says to use one 6" minimum :eek:
Will I be cool with a single 4?

ItalynStylion
02-12-2008, 07:48 PM
Here is a picture of my trunk before I did the box that is bolted to the IS300's rear deck. I was planning to build a box that sits between the wheels. My initial idea is to face the subs and port straight up and have the amp mounted to the face of the box that is closest to the trunk opening.
(PS: the amp is a sorta large so that is going into the design plans too)

http://i17.photobucket.com/albums/b75/ItalynStylion/Stock%20IS300/trunksetup001.jpg

BrianChia
02-12-2008, 08:08 PM
Le is a measurement of the inductance of the voice coil. It's not really too important for enclosure design.

If you're trying to achieve a flat response curve, keep in mind that the you will be getting an in car boost of typically 6-12db/oct that you should to account for.

This may be helpful:

http://linearteam.proboards12.com/index.cgi?board=winisd&action=display&thread=1087022128

I really like the look of the old enclosure, by the way.

ItalynStylion
02-12-2008, 08:20 PM
Le is a measurement of the inductance of the voice coil. It's not really too important for enclosure design.

If you're trying to achieve a flat response curve, keep in mind that the you will be getting an in car boost of typically 6-12db/oct that you should to account for.

This may be helpful:

http://linearteam.proboards12.com/index.cgi?board=winisd&action=display&thread=1087022128

I really like the look of the old enclosure, by the way.

Thanks, I like it too and it's going to be hard to give up even though it is for the better.

So when you say the in car gain will be 6-12db/oct; does that mean all throughout the frequency range? I want fairly flat response because this is an all out SQ car rather than an SPL car.

Any advise on the port size?

BrianChia
02-12-2008, 08:31 PM
Your car acts as an enclosure so it begins to boost output below certain frequencies. This is known as the transfer function of the vehicle. It acts like an inverted high pass filter and depending on the size of the car it may start anywhere from 70-100+hz. The larger the vehicle the lower the frequency before the transfer function starts to take effect.

This graph shows a good example of a modeled vs. actual response due to the transfer function of the vehicle.

http://www.diysubwoofers.org/projects/car/sub3/images/freq_resp.gif

This graph (purple line) shows the transfer function of the vehicle:

http://www.bcae1.com/images/gifs/leap07.gif

The summed responses of the measured transfer function and the modeled anechoic response (as calculated in UniBox) will be the actual in car response.



If you read the link that I posted above, you can learn to use WinISD Pro to approximate an in car response by applying a filter to simulate transfer function.

I actually just played around with the 6.5" TBs in WinISD and a 4th order bandpass looks like it would work well, although the enclosure would be fairly large.

ItalynStylion
02-12-2008, 09:55 PM
I've never used WinISD. I downloaded it but I haven't tried it out yet.

I'll play around with it a little later.

ItalynStylion
02-13-2008, 12:48 AM
This may be helpful:

http://linearteam.proboards12.com/index.cgi?board=winisd&action=display&thread=1087022128

I really like the look of the old enclosure, by the way.


Ok, I read that and I have no idea what it's telling me to do. I've found my driver in the database but I have no idea what do do....but I'd like to learn if you could explain it

ngsm13
02-13-2008, 12:51 AM
I would go too large... they're only 6.5's...

How much power are they getting?

nG

hazardous0388
02-13-2008, 12:51 AM
man....that install is ****, dont ruin it =(

ItalynStylion
02-13-2008, 10:04 AM
I would go too large... they're only 6.5's...

How much power are they getting?

nG

Are you saying that you wouldn't go too large?
They are getting 75rms each.

ItalynStylion
02-13-2008, 10:11 AM
man....that install is ****, dont ruin it =(

I know I know....but honestly I'm running into a problem.

I want to set m gains right and use the full voltage of my headunit. My eclipse has 8volt pre outs and the volume maxes at 80. I tuned so that 70 was pretty much my listening max; this meant I had the gain up on the subs with the non fade set really low and I had to set the Focal's gain almost all the way down to balance them. This made the Focal's sound really anemic because the gain was so low. I need to port and get my subs on par with my front stage so I can get the best SQ out of the system.
(hope I explained that right)


The ported box I make wont be plain so don't worry. It will be just as **** I promise ;)

ngsm13
02-13-2008, 01:00 PM
Are you saying that you wouldn't go too large?
They are getting 75rms each.

Yeah, I'd go with the 1.7-1.9 and tune ~36hz...

Single 4" Aeroport. Subs towards the rear, port towards side, amp on top.

Win!

nG

ItalynStylion
02-13-2008, 01:04 PM
Yeah, I'd go with the 1.7-1.9 and tune ~36hz...

Single 4" Aeroport. Subs towards the rear, port towards side, amp on top.

Win!

nG

Why not face the port the same direction as the subs?

TeamPlayers
02-13-2008, 03:23 PM
subscribed

BrianChia
02-13-2008, 03:49 PM
Yeah, I'd go with the 1.7-1.9 and tune ~36hz...

Single 4" Aeroport. Subs towards the rear, port towards side, amp on top.

Win!

nG

Probably a bad choice if you want to maintain SQ.

I ran up a sim on a 4th order design which was nearly as flat as a sealed setup but about 4-6db more efficient.

BrianChia
02-13-2008, 04:54 PM
Here you go, I modeled 3 different alignment with predicted transfer function. To do that I added a Linkwitz-Transform filter. The corner frequency F0 of 80hz was just a guess. The actual corner frequency is determined by the speed of sound / 2 * (the longest internal length of the cabin) or =c/2l. The filter Q of 0.707 creates an effect like an inverted 2nd order Butterworth filter.

As you can see the ported box produces a nasty peak and has severely reduced low end extension. This is typical of most ported boxes used in cars. The 4th order and sealed give the flattest response because the roll off of sealed enclosures is roughly equivalent to the inverted slope of the transfer function, thus summing equally to a flat response.

All 3 curves show predicted SPL at 300 Watts of power.

http://img405.imageshack.us/img405/4783/incarresphq2.png

ItalynStylion
02-13-2008, 07:49 PM
^wow, thanks for doing that!

The 4th order response curve looks MUUUCH better than the others. I have my Focal's crossed over at 80hz though; would there be any way to get that nearly flat response from 80hz down?

PS: I don't even know what a 4th order band pass is but I can look at those response curves and know what's what i want. Can you explain this to me? I can build anything so construction is not a problem ;)

BrianChia
02-13-2008, 08:54 PM
A 4th order bandpass is basically a sealed enclosure that fires the subwoofers into a ported chamber. The ported chamber acts as a low pass filter cutting off frequencies above tuning the same way that a ported box acts as a high pass filter.

See this page for more details:
http://www.diysubwoofers.org/bnd/4thorder.htm

http://www.geocities.com/f4ier/subsimPictures/4obp.gif

Of course everything comes with a price. The 4th order box I modeled was 2.5 cf in the rear chamber and 1.0 cf in the front chamber, with the port tuned at 65hz. We can compromise some if you fill the rear with heavy poly-fill, and get by with about 1.5-2.0 cf. The larger the sealed chamber is the lower it will extend with flat response. The front chamber can be ported around 68-70 hz to increase the passband up to around 75hz. If you are running active high passes for the mid-woofers, then it should be easy to drop the high pass down to 70 hz or so to match.

ItalynStylion
02-13-2008, 10:07 PM
****, it sounds cool but I don't know if I'm ready to give up that much trunk space. I was hoping to get out around 2 cubes.

If I did do the ported box that I had listed before and tune to 35; what will do you think that the cabin gain will compensate for the sharp drop off that happens around 36hz?


Oh, and a build log will follow all of this indecision for those that care...

ngsm13
02-14-2008, 01:47 AM
Why not face the port the same direction as the subs?

You going to make your enclosure that large?

nG

BrianChia
02-14-2008, 03:26 AM
You going to make your enclosure that large?

nG

He could use an elbow.

ItalynStylion
02-14-2008, 09:24 AM
You going to make your enclosure that large?

nG

The enclosure would be right about 1.94 cubes tuned to 34hz. With a 4" precision port it would only have to be 11.3 inches. That's not that long.

its_bacon12
02-14-2008, 09:27 AM
A 4th order bandpass is basically a sealed enclosure that fires the subwoofers into a ported chamber. The ported chamber acts as a low pass filter cutting off frequencies above tuning the same way that a ported box acts as a high pass filter.

See this page for more details:
http://www.diysubwoofers.org/bnd/4thorder.htm

http://www.geocities.com/f4ier/subsimPictures/4obp.gif

Of course everything comes with a price. The 4th order box I modeled was 2.5 cf in the rear chamber and 1.0 cf in the front chamber, with the port tuned at 65hz. We can compromise some if you fill the rear with heavy poly-fill, and get by with about 1.5-2.0 cf. The larger the sealed chamber is the lower it will extend with flat response. The front chamber can be ported around 68-70 hz to increase the passband up to around 75hz. If you are running active high passes for the mid-woofers, then it should be easy to drop the high pass down to 70 hz or so to match.

in theory they should do as you described, but in reality, 4th order bandpass boxes really are designed for output at a very narrow frequency band, but could gain up to 12 db at those frequencies..

if you're up to it OP and want to try a bandpass, look into 6th order. covers a much wider range.

ofcourse, i would suggest a ported box where you can get as close to a qtc of .707 to get the best response. mess around with winisd to see what kind of things you come up with

its_bacon12
02-14-2008, 09:32 AM
^wow, thanks for doing that!

The 4th order response curve looks MUUUCH better than the others. I have my Focal's crossed over at 80hz though; would there be any way to get that nearly flat response from 80hz down?

PS: I don't even know what a 4th order band pass is but I can look at those response curves and know what's what i want. Can you explain this to me? I can build anything so construction is not a problem ;)

i doubt you would notice a difference between ported and 4th order bandpass in that situation.. personally, i hate the sound of 4th order bandpass, even if done right.

if you want some more help on them though, talk to 80inches he was into them for a long time and recently decided ported was for him.

BrianChia
02-14-2008, 09:37 AM
in theory they should do as you described, but in reality, 4th order bandpass boxes really are designed for output at a very narrow frequency band, but could gain up to 12 db at those frequencies..

if you're up to it OP and want to try a bandpass, look into 6th order. covers a much wider range.

ofcourse, i would suggest a ported box where you can get as close to a qtc of .707 to get the best response. mess around with winisd to see what kind of things you come up with

The trick to getting flat frequency response out of a 4th order bandpass is to utilize the "peakiness" of the design to match the transfer function of the vehicle. In other words, I'm well aware of the narrow frequency and it can be used as an advantage to balance out the cabin gain. The response curves I posted above are ALL with transfer function AREADY factored in. The anechoice response of each would be drastically different. You would see a large peak on the bandpass and a -12db/oct rolloff. The ported box would look flat. The sealed would rolloff by -12/db but without a peak, hence the similar profile to the 4th order but with less output. A 6th order would only complicate the peaking problems associated with the regular ported box.

Also, ported boxes don't have QTC :fyi:.

ItalynStylion
02-14-2008, 09:40 AM
i doubt you would notice a difference between ported and 4th order bandpass in that situation.. personally, i hate the sound of 4th order bandpass, even if done right.

if you want some more help on them though, talk to 80inches he was into them for a long time and recently decided ported was for him.

Well I think in this situation a ported box will work best for me but I still need to learn about the other enclosure types. I'll probably end up reading a bunch of his threads.

its_bacon12
02-15-2008, 09:03 AM
The trick to getting flat frequency response out of a 4th order bandpass is to utilize the "peakiness" of the design to match the transfer function of the vehicle. In other words, I'm well aware of the narrow frequency and it can be used as an advantage to balance out the cabin gain. The response curves I posted above are ALL with transfer function AREADY factored in. The anechoice response of each would be drastically different. You would see a large peak on the bandpass and a -12db/oct rolloff. The ported box would look flat. The sealed would rolloff by -12/db but without a peak, hence the similar profile to the 4th order but with less output. A 6th order would only complicate the peaking problems associated with the regular ported box.

Also, ported boxes don't have QTC :fyi:.

my bad.. i was taught by someone to get the qtc as close to .707 as possible in a sealed box, then make a ported box with the same internal volume after all displacements for best results..

yeah the 6th order would make life alot more complicated for him.. unless you plan on researching a lot and doing some test trials to your vehicle, just do something simple. i doubt you'd be able to pick the difference if both had that kind of response in car anyway

its_bacon12
02-15-2008, 09:03 AM
and it was way too early for me and i was hungover when i typed that :(

Megalomaniac
02-25-2008, 12:13 PM
hmm 1.7 cubes.

Why not run a single 10 or a 12 and have it under a cube and a half....?(perhaps that new mag might be a good idea or the shallow BMs)

TPABlazer
02-25-2008, 03:01 PM
hmm 1.7 cubes.

Why not run a single 10 or a 12 and have it under a cube and a half....?(perhaps that new mag might be a good idea or the shallow BMs)

This is the dillemma that I'm running into. 2 7 inch subs ported sounds pretty good, albeit a little peaky, but I'm around 1.5 cubes with it all said and done. I could have easily done a slim 10 or something of the sort and used up the same amount of space. Would I get the same output? Thats the question.

mobeious
02-25-2008, 04:36 PM
why not rebuild the rear deck so u have the subs fireing up toward the glass with the port inbetween the subs pretty much same concept u have now but with the subs up instead of back

Megalomaniac
02-25-2008, 08:13 PM
why not rebuild the rear deck so u have the subs fireing up toward the glass with the port inbetween the subs pretty much same concept u have now but with the subs up instead of back

he doesnt want to cut into the lexus

Kil4Thril
02-25-2008, 09:34 PM
What about using a couple of PR's on each side? You could get the size down considerably, and still get low tuning.