subwoofer design problem

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I am making a subwoofer for a very high excursion 15" subwoofer driver called 15"HE manufactured by TC sounds
( )This subwoofer must be flat to around 20Hz.
This subwoofer will be used for music, so which type of enclosure is best...ported or sealed?

TCsounds 15"HE Theiele/small parameters

Fs 25Hz
Qts .24 ?20% (I have no idea what '?20%' means)
Vas 132 Litres
Xmax 3 inches peak to peak
SPL 90 ?2dB
Sd 732cm2

There were some problems when designing a sealed enclosure for this driver. The enclosure volume came out very small at 17.2 Litres with a qtc of 0.707 However, the bass-cut off Frequency (F3) was too high at 73.7Hz I want much lower bass than this There must be something wrong

There were also problems when designing a ported enclosure for this driver. The enclosure volume came out small at 33Litres. However, F3 was too high at 47.93Hz. The tuning frequency was also too high at 37.93 Hz. I want a subwoofer that is flat to around 20Hz

Is there a minimum port diameter with a driver that has a Xmax this big? ( 3 inches peak to peak )

all this tech jargon is blinding me
First off, what enclosure design program are you using? I dont think that some of those numbers sound right. Also, have you seen the vas for this driver?! 132 liters! This is far beyond the reach of most DIYers for in home use, and it seems that this is strictly a subwoofer designed for in car use. Also, these drivers were designed to be used with a minimum of 500 watts power in mind. It seems that this driver was designed for high SPL output, rather than to go low. Their other 15 inch driver seems to be a far superior choice for in home use, which even still has a vas of well over 200 liters! Not only is it unlikely that you will make this driver linear down to 20 hz, but it is unlikely that you will have success in designing an enclosure, unless you have the driver specs measured, due to the shoddy +- 20% measurements that are given.
Here ya go.....

Well what do they say "been there, done that". :) This design is optimized for the HE15 in the smallest possible ported box. Tuning is 18.56Hz, I don't recommend tuning any lower.

If you have LspCAD or BassBox Pro 6, I can email you the model files, if I remember where they are.....

We found the published HE-15 T/S parameters are somewhat 'optimistic', as compared to our measurements of the drivers we received. But the driver still performs quite well. The Fs is really in the 28-29Hz range after extensive break in. The efficiency is closer to 84-86db in most enclosures.

You will need parametric EQ with any alignment. The driver has a pretty good size hump around 70Hz due to the VC inductance, (see the CLIO measurements page on the Klone project site for specifics). A Behringer DSP110P is a good inexpensive choice

I'm working an a klone of the Krell MRS. Will be using 2 BluePrint 1503. These are for all intents and purposes identical in performance to the HE15.

BTW, If you deside to go with a sealed box seriously consider using a Linkwitz Transform circuit to optimize the performance in a smaller box

The AS-15 Project

An externally hosted image should be here but it was not working when we last tested it.

[Edited by ThomasW on 10-27-2001 at 01:50 PM]
reply to super: First off i dont think these drivers are not just for car use. This is becuase they are used in the $28000 Krell Master Reference Subwoofer, the stryke project, and a "PR" subwoofer in the website below:

For sealed enclosures, I am using a program called 'AJ Sealed Designer'downloaded from
For ported enclosures, I use the website java calculator at:
I cannot use WinISD because it does not list the tc sounds driver in the database.

You are right, the other 15" driver is much easier to design..but it has only 2 inch peak to peak Xmax.I prefer the 15"HE because it has 3 inches Xmax. I can think of no other driver that comes this close in extreme excursion.
Note: I like ultra exursion bass drivers that go low and can anyone suggest any other driver that can compete with the 3 inch peak to peak Xmax TC sounds 15"HE?
(The NHT 1259 with 26mm peak to peak Xmax does not qualify)
Lastly, are u saying that it is impossible for me to make enclosures for the TC sounds drivers without special equipment because their parameters are not accurate enough?

Reply to thomas: HOW CAN U TUNE THE VENTED BOX TO 18.56hz WHEN MY READINGS SAY THAT THE TUNING FREQ for your stryke 15"HE driver should be 29.95hz? Is there something wrong?
And what is a parametric equaliser?? This is getting really technical

The Krell MRS uses a drivers similar to the HE15 that yes are made by TC-Sounds, but they have a less sophisticated design. Here's a pic of an open MRS so you can see their drivers. These are actually closer in design to the BP1053 but with a smaller magnet structure

'Topless' Krell MRS
An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

Stryke HE-15
An externally hosted image should be here but it was not working when we last tested it.

Understand that the tuning of a ported box has nothing to do with the T/S parameters of the driver. The tuning is purely a function of the size of the box, combined with the size of the port and nothing else. The T/S parameters are needed only if you want to 'model' the performance of the driver in the box.

Now do you own a HE-15? If not, I doubt that you'll be able to buy one since the second special purchase was several months ago, and these aren't 'stocked' by Stryke

If you don't own a HE-15 take a look at the 1503 from These have almost identical performance to the HE-15, are much cheaper and are in stock.

Enter the T/S parameters into WinISD. Or for a more accurate model if you have MS Excel download a copy of Unibox from and enter these HE-15 T/S parameters, they are from our testing. Chose 18 or 19Hz as the Fb for the design.

Fs: 28.5 Hz
Qms: 6.0
Qes: .345
Qts: .326
Vas: 106.7 L
Re: 6 ohm
BL: 27.3 Tm
no: .529%
1W SPL: 86 dB
Cms: .145 mm/N
Mms: 257 grams
Rms: 7.0 kg/s
Xmax: 22.85 mm
Sd: 720 cm^2
Vd: 6.5L total
PEmax: ~ 2000W

A parametric EQ is one that has variable frequencies and bandwidths instead of fixed ones like a 1/3 octave EQ.

If your now completely lost I'll help design a cabinet if you own a driver, either the HE-15 or BP-1503.

Hope this helps.....


[Edited by ThomasW on 10-27-2001 at 10:53 PM]
Nope..i havent bought the 15HE
I've decided to go with a vented this a wise decision since the sub will be used for music...not home cinema
lve actually seen the BP1503 before. I thought it was one of those poor quality cheap drivers because of the dramatic price difference..stryke 15HE- $1000 BP1503-$219
what makes the BP so cheap? Can it produce clean bass to 16Hz? If so..i choose the BP..its so much cheaper

If you are saying the tuning of the ported box has nothing to do with T/S parameters, then what is the tuning freqenency used for?
Also...are there any guidelines or reasons that say which frequency you should tune the box to?

My aim is to build a subwoofer that can produce bass with good, strong and clean output to 20Hz..16Hz is even better because it can compete with pipe organs

F3 for the BP1503 is 37.6Hz----does this fulfil my aim?
Fb for the BP is 33.26Hz-----does this fulfil my aim?

Both frequencies are in the thirties...does this mean that it has limited output in the low 20Hz region?

Do you have more specs for the BP? The site does not list its nominal power rating, its Le (so-called Equivalent Voice Coil Inductance), and its "series resistance"
(all this technical jargon and mumble jumble).

[Edited by pkgum on 10-27-2001 at 11:39 PM]
A vented enclosure can generally go lower than a sealed enclosure, but will tend to trade off "tightness" or speed in the lower octaves. Because of this, several music-only subs are sealed. However, if you want to go deep, I'd stick with the ported enclosure, and often, there is a minimal difference if a quality driver is used. (I use my ported SonoSub for music and HT alike, and found it to outperform many sealed commercial designs, including Velodyne and REL, using only a single Shiva driver)

Also, would you be willing to consider using stereo subs? I've often found that using two drivers that have similar performance to the bigger brother or more expensive drivers can often outperform the "bigger brother" when two drivers are used. If you were able to get your hands on the HE15, its not unlikely that you will get better performance out of two BP1503's, because each driver will only have to do half as much work, thereby decreasing distortion. Heck, for only $219 per driver, you could build four subs for the price of one! The odds of that one driver outperforming 4 drivers of comparable specs is highly unlikely. GRollins, for example, uses SEVERAL 12 inch subs (a LOT more than four), and achieves disgusting SPL's well into the 16hz range and beyond, despite using fairly inexpensive drivers. (Dayton Titanic drivers if I recall correctly)

As for things that make one driver cheaper than another, well, there are several things. Power handling is probably one of the biggies. There is also the amount of material that goes into making the cone, and also the quantity that the drivers are manufactured in. However, whether theres $800 dollars worth of difference is up to you. Personally, I'd go with multiple subs using the more inexpensive drivers.

[Edited by Super on 10-28-2001 at 12:05 AM]

When the Stryke HE-15 preorder sales are offered the cost of the HE15's are approx $400ea. I paid less for my 2 because I bought in a presale a year ago December. My understanding is that there may be a few HE-15's available for $425ea

The $1000 'list' price is because Audiobahun the German company that buys the largest number of the drivers from TC-Sounds and sells them for $1000; told TC-Sounds that if Stryke stocked and sold the HE15 for $400 as a regular stock item, there would be legal trouble.

The BP10503 don't use custom designed parts and aren't built as a special order item. They use high quality stock off the shelf parts assembled properly. Also they don't have an aluminium cone and dust cap, double spider, or VC leads woven into the spider. So unlike the HE-15 it's not audio jewelry, but it's a very good driver at a very good price.

I dare say that in a A/B comparison (HE-15 vs BP1503) it would be very difficult if not impossible to tell the difference in a shootout. Understand I own both these drivers so I do speak from experience.

Note neither of these drivers will go down flat to 16Hz. They both do fine down to approx 18-19Hz though.

As I stated before the tuning frequency is related to the box not the driver. But you can't randomly choose an Fb and have any driver work well there. That's why both the HE15 and 1503 should be used in a vented box tuned to between 18-19Hz

Here is a copy of the DUMAX testing done on a BP1053

An externally hosted image should be here but it was not working when we last tested it.


It's important to look closely at the specs of these high excursion drivers. They have a Vd greater than 6 liters, that's equal to multiple 12"s. And they have power handling abilities that are correspondingly high as well. They certainly aren't for everyone's taste. But if a 'portable' sub having the ability to play at rock concert SPL's day in and out is needed, these will do the job. BTW, the sound quality of the AS-15 design is extremely good. I built one of the Stryke cubes with the PR's and wasn't impressed.

Also having 12-12" drivers isn't something exclusive to GRollins. This is my primary sub, a dozen Shiva IB config, just about 2yrs old. It's about 7db down at 10Hz from a reference level output of 100db. Max output is around 130db@20Hz. Measurements were made with a calibrated B&K 4133 using a CLIO system

An externally hosted image should be here but it was not working when we last tested it.

[Edited by ThomasW on 10-28-2001 at 01:22 AM]
some questions...

My aim is to build a subwoofer that can produce clean strong bass to around 18Hz

F3 of the BP1503 enclosure is 37.6Hz----is this alright?
Fb of the BP1503 enclosure is 33.26Hz-----is this alright?

Both frequencies are in the thirties...does this mean that the subwoofer has small output in the low 20Hz region?

To thomas: How did you know that u should tune the BP1503 enclosure to 18-19Hz?
Are there any guidelines as to what frequency i should choose to tune the vented enclosure?

You said the tuning of the ported box has nothing to do with "T/S parameters" (tech jargon), then what does the tuning freqenency indicate?

You said the tuning of the ported box has nothing to do with T/S parameters, then what is the tuning freqenency used for? What does it indicate?

As I've stated, Fb indicates the frequency the box with its port is tuned to. Think of a ported box as something similar to pop bottle, and you're blowing across the top. If the size of the box, combined with the diameter and length of the port are tuned to 18Hz, when you blow across the port a 18Hz tone is produced. Now this is a bit over simplified.....

Fb = Enclosure resonance (usually for bass reflex systems), in Hz
F3 = -3 dB cutoff frequency, in Hz

To better understand this go to the 'Calculate Your Vent Length' section of the website you're using for ported designs
Now type in quantity of ports =1
Enter volume of enclosure =8 ft3
Enter desired tuning frequency = 8Hz
Enter desired port diameter =6"

You'll get a port length of 25.01".

This is how you tune a box to 18Hz without having or using any T/S parameters. Now I'm not suggesting that this is how to design a sub. It's just an example of how to tune a box.

All woofers roll off as the frequencies drop. The port in a reflex design only serves to add some additional boost around the tuning frequency (Fb). Where as a sealed box rolls off at a fixed rate.

Depending on the amount of room gain, EQ will most likely be required to get flat response from any sub down to 18Hz.

You might want to pick up a copy of "The Loudspeaker Design Cookbook" by Vance Dickason. This is a good book to get a grasp of the what/why/how of speaker design.


[Edited by ThomasW on 10-28-2001 at 09:37 AM]
Thomas: Just a quick note. I'm well aware of the 12 Shivas Dancing project. I was just referring to multiple drivers in separate cabinets, for a true stereo setup, not necessarily a multi-driver isobaric setup. Sorry for the mistunderstanding :)

Also, I am aware of the displacement of these drivers. However, I think that the use of multiple high quality drivers can be more linear in lack of distortion when EQ'd properly than a single driver being pushed harder.

I certainly agree that multiple drivers in theory are better than one of the high excursion 15's. But I was quite surprised as to how clean the high extension drivers are, even when driven to extreme SPL's. The big IB is of course the best sounding sub I've ever heard, regardless of cost or construction constraints. It's not real 'mobile' though :)

This woofer seems to me an unity for bass reflex for car SPL use, as Super said. It seems to me you really want to use this unity as well.

So, why don't you use this woofer in a bandpass configuration? Using this configuration some negotiation with volume, efficiency and f3L and f3H is possible. Many computer programs can calculate the best frequency response for you.

Should I trust the T/S parameters on the DUMAX report or the different parameters on the blueprint website.


F3 of the BP1503 enclosure is 26.06Hz...does this mean that the finished subwoofer guadually has small output in the tones below 26Hz? But according to thomas this subwoofer should have good output to 18Hz, but the F3 for the enclosure is higher, at 26.8Hz.
They say that in ported enclosures the output drops sharply below F3. Note..The F3 is calculated using the report thomas supplied


Bandpass enclosures are beyond my reach. Theyre harder to make and need more time than ordinary vented enclosures. I like my design to be SIMPLE

A ported cabinet must be tuned to 18Hz, to get output at 18Hz, forget the F3.

Sorry but I don't have the time or patience to give an extensive online tutorial in basic subwoofer design.

Consider doing one of 2 things, either trust the info I'm giving you, or purchase a good loudspeaker design program that shows the effects of ROOM GAIN on the performance of a sub. I suggest LspCAD $150.

Here's a plot of the Styke cube measured by Tom Nousaine. As the plot shows the HE-15 will have good output to 18Hz. This is VERY similar to what you would get if you build the ported AS-15 design

An externally hosted image should be here but it was not working when we last tested it.
Should I trust the T/S parameters on the "DUMAX" report or the different parameters on the blueprint website.


F3 of the BP1503 enclosure is 26.8Hz...does this mean that the finished subwoofer guadually has small output in the tones below 27Hz? But according to thomas this subwoofer should have good output to 18Hz, but the F3 for the enclosure is higher, at 26.8Hz.
They say that in ported enclosures the output drops alot below F3. Note..The F3 is figured out using the DUMAX report that thomas supplied
maybe I can help :)

Thomas is right, the resonant frequency of the box does not have anything to do with the driver. You could put any driver in an existing ported box with a particular resonant frequency and it [the box] will still have the same resonant frequency. The T/S params. on the other hand are used by humans/simulators to construct a mathematical or computer model of the driver unit. They also guide you in designing an appropriate box... given your design goals such as (maybe) maximally-flat response.

There is no one "correct" Fb to which your ported box should be tuned -- this should have been mentioned in your book. Ultimately, it will depend on your design goals, which in turn is usually dictated by your listening room's acoustics. If you have calculated an Fb of 33.26Hz, it could be that your book is recommending an SBB4 alignment or maybe it [the book] is based on an enclosure-loss-less set of equations (or something else). The Loudspeaker Design Cookbook that ThomasW has mentioned discusses the SBB4, SC4 and QB3 alignments to name a few. It really is a good book.

Regarding your urgent question. No, not necessarily -- it simply means that the BP1503 on an IB or sealed box will roll off a bit early. But this is where the BP1503's huge Xmax comes in to assist it in going as low as 18Hz. With more amplifier power and a Linkwitz Transform circuit, the BP1503 can go low and loud with sound quality to boot. is a great link for box simulators including my beta program (I know, that's a shameless plug :D ) and a Linkwitz Transform spreadsheet.

A good program to approximate your room's acoustics is Adire Audio's version of lspCAD, which can be found at You can use it to plot your room's effect on the sound.

Good luck :)


DUMAX testing is the most accurate loudspeaker testing available.

Also please STOP fixating on the F3. All drivers and alignments roll off. ROOM GAIN helps boost the lowest frequencies. Also you will need to use a parametric EQ to get flat response to 18Hz from the ported enclosure. Linkwitz-Transform circuits are designed for use with a sealed box, they allow adjustment of the Qtc. BTW Look at the before and after EQ CLIO plots on the AS-15 project website. These show how the frequency response is effected by the equalization

FIY, the design team that created the AS-15, (this being JonMarsh and myself) have 75 years of combined loudspeaker design experience. Yes, that does mean that we're old f*rts :) and we certainly know what we're doing!

The AS-15 design, built either with the HE-15 or BP1503 is designed to be the best performing high output 15" ported sub available. There are no compromises what so ever in this design.

Jon is making complete set of AutoCAD drawings for the AS-15, we will post them to the website for download. It will be a couple of weeks before they are completed.

That's all for tonight

[Edited by ThomasW on 10-29-2001 at 02:48 AM]
For now i had made my own basic sub

Vb = 2.953cb.ft (bracing, driver displacement, and damping not included yet)
F3 = 26.06Hz
Fb = 18Hz according to thomas

Port diameter = 8 inch (since programs says that minimum port diameter is 7.85inches)tuned to 18Hz
port length = 135.73 inches....there is something wrong..can anyone tell me what to do
What's wrong is that you can't make the box any smaller than about 6.5-7 cu ft NET internal volume. And you need to use a 6" dia flared port not a 8" dia one

Did you read the text in the AS-15 project page?. It states the size of the box, the diameter and the length of the ports. And the CLIO testing proves that the design functions at the desired Fb of 18.56Hz.

Making any changes in the design will result in a sub that doesn't perform up to the full potential of the HE15/BP1503


Just to avoid any further confusion. The Lightning Audio port flares are the only 6" dia flares available. They need a pipe that has a 6.25" OD for a good fit. The PVC pipe I used has a 6.25" OD and 5.75" ID, so for software modeling purposes use 5.75" as the diameter of the port. The 22.5" long port PVC tube combined with the length of the 2 flares gives a total port length of 25.5". That tunes the AS-15 box to 18.56Hz.

Note, a nominal 6" dia port with flares, will flow virtually as much air as a 8" diameter port without flares, and it can be much shorter.

[Edited by ThomasW on 10-29-2001 at 12:56 PM]
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.