Please comment on my DIY Bass module plans

[VERTIGGO]

I've been reading like a fiend and I'm pretty excited about building a cabinet, but I haven't seen much about what drivers are made well enough for HT. I see hundreds of woofers on ebay and 99% look like they were yanked from some Joe's trunk.

Anyway, I've been considering an AE AV15-H:
http://aespeakers.com/shop/catalog/product_info.php?cPath=31&products_id=67&osCsid=7677db0c60792fc7ab30062347d47413

Driven by a Behringer EP2500:
http://www.amazon.com/Behringer-EP2500-Channel-Rackmount-Amplifier/dp/B0002KZQ9I/ref=pd_bbs_sr_1?ie=UTF8&s=electronics&qid=1235065662&sr=8-1

And for aesthetic reasons I'd like to go with a down firing sealed compartment similar to the Rubix project (less flashy of course), but according to Win ISD I would get much better LF response with a ported system. Should I modify the Infinity Kappa sticky to my dimensions?

#1 Question: What can I read to learn exactly how to calculate the volume and port size that is best for my build... or are Win ISD's numbers good enough? (I entered AE's data into Win ISD since it was too new to be in their database)

Thanks much!

 

[VERTIGGO]

Here's the concept of what I came up with. WinISD gives it a decent curve, but I have no idea whether I can trust the software or not... Does this look good to anyone?

This is the default WinISD curve for this driver in a ported design:

The odd thing to me is that if I make the box larger, the curve spikes much worse (at about 50Hz), which seems like a bad thing, even if it means more volume... it would seem to me that i need a small box if I want to avoid boomy frequencies.

 

[VERTIGGO]

Alright, well I ordered all the pieces I need, and I've settled on some dimensions, but I'd appreciate some warnings or suggestions before I start hacking up MDF. The inside layer will be 3/4" MDF and the outside 3/4" finish ply. The pvc port will be 8" in dia. and 15.5" long based on an internal 21*29*45 (27405 cui) volume.

As far as I can tell, with a little EQ from the DSP1124 I should be able to squeeze out some decent sound from this:

Any yays or nays? Thanks...

 

[lsiberian]

I will be blunt. I think you will be much more pleased with a Kappa build it has a very linear response and is already a well designed box.

If you want to do an Axis build i'm sure you could get help here. But this build looks bad. There is a huge dip in the response from what I can see. That's terrible. Why waste your effort when the Kappa has a much better curve.

 

[TLS Guy]

I've been reading like a fiend and I'm pretty excited about building a cabinet, but I haven't seen much about what drivers are made well enough for HT. I see hundreds of woofers on ebay and 99% look like they were yanked from some Joe's trunk.

Anyway, I've been considering an AE AV15-H:
http://aespeakers.com/shop/catalog/product_info.php?cPath=31&products_id=67&osCsid=7677db0c60792fc7ab30062347d47413

Driven by a Behringer EP2500:
http://www.amazon.com/Behringer-EP2500-Channel-Rackmount-Amplifier/dp/B0002KZQ9I/ref=pd_bbs_sr_1?ie=UTF8&s=electronics&qid=1235065662&sr=8-1

And for aesthetic reasons I'd like to go with a down firing sealed compartment similar to the Rubix project (less flashy of course), but according to Win ISD I would get much better LF response with a ported system. Should I modify the Infinity Kappa sticky to my dimensions?

#1 Question: What can I read to learn exactly how to calculate the volume and port size that is best for my build... or are Win ISD's numbers good enough? (I entered AE's data into Win ISD since it was too new to be in their database)

Thanks much!

The driver you have selected is no good for home use. That is car only. In a vented box as you have found out it does not reach sub frequencies. If you enlarge the box you have huge ripple. You can not Eq a ported enclosure, as the driver decouples from the box below Fb. This will not only destroy the driver, but does not extend bass and causes huge distortion.

That driver is designed to be in a small sealed box and have large amounts of Eq applied. That will give enough spl for a car, but not a room.

That driver will make a lousy home sub.

My advice is to return it.

You have a pretty good selection of drivers to choose from on my website.

You can tell the driver will be no good for home use as it has a very low Qt.

The only loading that would give deep bass would be a huge exponential horn cabinet.

 

[VERTIGGO]

Ok, I just saw so many home builds with it on here that I assumed it was ok...

The thing is, I'd like to go sort of big, a bit bigger than the Infinity Kappa. I think that is a great design, but I'm looking more into the 15" with 15 cubic feet sort of build.

 

[TLS Guy]

Ok, I just saw so many home builds with it on here that I assumed it was ok...

The thing is, I'd like to go sort of big, a bit bigger than the Infinity Kappa. I think that is a great design, but I'm looking more into the 15" with 15 cubic feet sort of build.

This is a good teaching case.

Here is the driver you selected, in a 3.5 cu.ft ported box. This box gives the maximum bass extension. It requires a port 3" X 12" 50.6 inches long, to get the vent air velocity down to an acceptable 18 m/sec. Yet the F3 is only 45 Hz. So it may be a big powerful driver, but sub driver it is not. I can design a book shelf with that much bass extension.

Here is your driver in its optimal ported enclosure.

Name: Lambda 001
Type: Standard one-way driver
Company: AE speakers
No. of Drivers = 1
Fs = 22 Hz
Qms = 4.46
Vas = 197 liters
Cms = 0.22 mm/N
Mms = 235 g
Rms = 6.7 kg/s
Xmax = 23 mm
Xmech = 34.5 mm
P-Dia = 318 mm
Sd = 794 sq.cm
P-Vd = 1.826 liters
Qes = 0.29
Re = 2.7 ohms
Le = 0.28 mH
Z = 4 ohms
BL = 17.6 Tm
Pe = 1000 watts
Qts = 0.27
no = 0.697 %
1-W SPL = 90.7 dB
2.83-V SPL = 95.5 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box
Shape: Prism, square
Vb = 3.553 cu.ft
Fb = 22.84 Hz
QL = 6.447
F3 = 45.33 Hz
Fill = minimal
No. of Vents = 1
Vent shape = rectangle
Vent ends = two flared
Hv = 3 in
Wv = 12 in
Lv = 50.66 in

The optimal sealed volume for bass extension is 1.5 cu.ft. This gives an F3 of 71 Hz without Eq.

Name: Lambda 001
Type: Standard one-way driver
No. of Drivers = 1
Fs = 22 Hz
Qms = 4.46
Vas = 197 liters
Cms = 0.22 mm/N
Mms = 235 g
Rms = 6.7 kg/s
Xmax = 23 mm
Sd = 794 sq.cm
Qes = 0.29
Re = 2.7 ohms
Le = 0.28 mH
Z = 4 ohms
BL = 17.6 Tm
Pe = 1000 watts
Qts = 0.27
1-W SPL = 90.7 dB
2.83-V SPL = 95.5 dB
-----------------------------------------
Box Properties
Name:
Type: Closed Box
Shape: Prism, square
Vb = 1.496 cu.ft
Qtc = 0.518
QL = 18.84
F3 = 71.05 Hz
Fill = heavy


Now this is a powerful driver, however even without Eq, in a sealed enclosure, its cone excursion is 16 mm out of its total of 23 mm at maximum power.

So you could Eq the driver, starting at around 80 Hz. By 20 Hz you would have to provide 24 db of boost. So that driver takes 100 watts to produce 100db at 100 Hz. It would take 6400 watts to produce 100 db at 20 Hz. That would burn out the voice coil. So in practice the driver would only produce 91 db spl at 20 Hz, using its maximum rated power. I bet it actually would not be quite that good.

So why is this so. Well first of all there is an inverse relationship between sensitivity and bass extension. This driver is of high sensitivity for a sub.

Now a driver has mass and compliance. The mass is the weight on the spring, and the looseness of the compliance the stiffness of the spring. You can tell from the T/S parameters that this driver is on the stiff side, and that is limiting bass extension.

This driver is designed to play loud but not deep. It fulfills the definition of what I think is called a "Blaster".

Now the size of a driver cone has nothing to do per se with bass extension. It is a function of mass and stiffness.

The JL 8" sub on my site, will outperform the driver you have selected in every parameter.

If you want something that plays louder than the perfect kappa 12, and I don't now why you would, you will have to pay the price of JL labs drivers.

This post should become a sticky in the DIY section.

This problem arises continuously. The driver size is the last thing you look at when deciding whether it is any good. Your situation goes to the very heart of that issue.

If you want I can post all the graphs on my website. The data exceeds the limit of what you can post on this site.

 

[VERTIGGO]

No problem (graphs), and thanks so much for the information. I understand the difference between a good driver and a "big" driver now.

I guess I'm wondering why so many DIY's use these drivers. More specifically, you mentioned I wouldn't want more than the perfect kappa, if I can get a decent 15" driver and build a big cabinet, why am I worse off? What about something like this: http://www.avsforum.com/avs-vb/showthread.php?t=1010405

BTW if this is stickied, the subject should be changed so it describes the issue better...

 

[WmAx]

The Sound Splinter 15" (www.soundsplinter.com) is an excellent 15" driver of not much more cost than the AE driver you purchased. I refer to their low cost 15. It is produced/designed by TC Sounds/Audio Pulse - bar none the best/most capable sub manufacturer in the world, technically speaking, based on available third party measurements - they have the best measuring sub driver technology presently known. Now, the low cost 15 is not an example of their best tech - but it's extremely good for the price. I'm just pointing out the ability of TC Sounds. Sound Splinter also has an expensive 15 that used TC Sounds highest end tech (LMS motor), which will produce the highest sound quality possible even at the limits of excursion. Though, it may produce slightly less absolute SPL than the cheaper unit(which is more SPL oriented), it is superior in SQ at the SPL limits. The LMS based drivers from TC Sounds have a near perfect motor; virtually unheard of. It has a motor strength/characteristic that remains almost identical at 1mm vs. 25mm excursion, where as almost ANY other driver has a motor that changes in characteristics largely at different excursions(worsening at more excursion), resulting in distortion and other anomalies at moderate to high excursion/power. The AXIS driver that was referred to earlier is also a TC Sound driver; not using the LMS tech, but a very linear tech, and more geared towards combing high linearity with extreme SPL abilities. Then there is the full blown Ultra-LMS line with uses LMS tech combined with the ability to produce huge SPLs -- but these are extremely expensive and hard to get.

The AE AV15-X driver has some promising parameters. This is different from the one you purchased, however. Also, it's not really proven, measurably, as far as I know. Various TC Sounds drivers have been measured, and have been consistently phenomenal.

-Chris

 

[TLS Guy]

No problem (graphs), and thanks so much for the information. I understand the difference between a good driver and a "big" driver now.

I guess I'm wondering why so many DIY's use these drivers. More specifically, you mentioned I wouldn't want more than the perfect kappa, if I can get a decent 15" driver and build a big cabinet, why am I worse off? What about something like this: http://www.avsforum.com/avs-vb/showthread.php?t=1010405

BTW if this is stickied, the subject should be changed so it describes the issue better...

You would not necessarily be worse off. The point I'm making is that it is the motor system and T/S parameters that count and not the diameter of the driver cone. That only has relevance is so far as the fact the larger diameter cones tend to be heavier than smaller ones, and that there will be a tendency to higher spl. However, when given the choice I will pick to 10" drivers over one 15" as a rule, if I can get as good an F3 and power handling.

Now Chris knows the few drivers around with huge motor systems, that can honestly take the power.

It seems to me that one or two kappa perfect 12 drivers would give all the conceivable spl and bass reach you would need in any domestic environment.

I posted this about a member who had just blown a sub, and this post touches on the consequences of design and driver selection.

Anyhow don't be discouraged, you still do have a large enough selection of drivers to choose from to have a successful project.

 

[lsiberian]

Ok, I just saw so many home builds with it on here that I assumed it was ok...

The thing is, I'd like to go sort of big, a bit bigger than the Infinity Kappa. I think that is a great design, but I'm looking more into the 15" with 15 cubic feet sort of build.

If you have a large room. I think you would be better off with 2 to 4 Kappa's or the Driver Chris suggested.

4 Kappas could probably shake everything off your walls. I don't think you understand the power of a well done DIY sub. As Chris always says there is just no commercial comparison.

Imagine that in a house. You have enough bass to disturb people for a long distance. The thing that makes the Kappas so good is that they are linear and made to have less distortion than many other subs.

 

[annunaki]

Ok, I just saw so many home builds with it on here that I assumed it was ok...

The thing is, I'd like to go sort of big, a bit bigger than the Infinity Kappa. I think that is a great design, but I'm looking more into the 15" with 15 cubic feet sort of build.

Maelstrom-X, vented, 16ft^3 tuned to 15hz. 1000+ watts will have you running to mommy.

This is an 18" driver with a very linear motor design. Warpdrv has two of them running sealed w/eq and is very happy with them.

Running it vented would be downright scary as the f3 in the enclosure I mentioned above is at 14hz-15hz. The SPL is well above 100db at that frequency range. This is crazy output if you have never experienced it before. Did I mention it is still linear at those output levels?

 

[Nemo128]

I'm salivating at the idea of a DYI sub... but I have to rebuilt some WAF...

 

[VERTIGGO]

Well I called AE today and they're building the driver as I write, but I did ask them to switch to the AV15-X, and I have some small modifications that I'll make to the enclosure. In particular, I'll be trimming the size down to around 10 cu. ft. and tuning around 16Hz, and the EQ will pull down any spikes or room gain that I detect.

I'm grateful for the advice about the Infinity, but I'm going to try this build for now.

simon5 modeled several options for me here:
http://www.aespeakers.com/phpbb2/viewtopic.php?f=1&t=1786&p=6177#p6177

 

[John_E_Janowitz]

The driver you have selected is no good for home use. That is car only. In a vented box as you have found out it does not reach sub frequencies. If you enlarge the box you have huge ripple. You can not Eq a ported enclosure, as the driver decouples from the box below Fb. This will not only destroy the driver, but does not extend bass and causes huge distortion.

The AV15H and AV15X are both designed for the home theater/recording industry where you need high amounts of extremely clean output. The AV15H has a 4 layer flat copper coil. It is a very good driver for home theater use, but as it has higher mass and extremely high motor strength it is optimized for smaller enclosures. The AV15H in 5cf tuned to under 18hz with a pair of 18" PR's will give you extremely good extension in a small enclosure. Hoffman's iron law dictates that the smaller the enclosure, the more mass and motor strength you need to get the same output. The drawback is requiring more power to do this.

Not everyone however needs a small enclosure. That is why we have 2 versions of the AV15 now. The AV15X has a 4 layer flat aluminum coil that is less conductive and lighter. Having less motor strength and mass is what you want in a larger enclosure. The following graph shows the AV15X in 10cf tuned to 16hz in yellow and the AV15H tuned to 18hz by a pair of 18" PR's in 5cf.

From 80hz to 15Hz the response drops less than 5dB with the 10cf AV15X. When you factor in any kind of room gain you will have in nearly any room, you'll be fine to under 20hz and often need to pull down the response a little if you want it very flat. You're also capable of around 115dB at 15hz with 1000W input. Cone excursion is still within the 23mm Xmax by a decent amount. The AV15H gives up a little extension but the enclosure is half the size in return.


John

 

[John_E_Janowitz]

That driver is designed to be in a small sealed box and have large amounts of Eq applied. That will give enough spl for a car, but not a room.

That driver will make a lousy home sub.

My advice is to return it.

You can tell the driver will be no good for home use as it has a very low Qt.

The only loading that would give deep bass would be a huge exponential horn cabinet.

For a sealed enclosure you typically want a higher Q driver, not a low Q driver. A low Q driver with a Linkwitz transform or DSP and a lot of power can make a very good home theater subwoofer in smaller sealed enclosures. We do this quite often in recording studios. The Seaton Sound Submersive is the same type of a subwoofer using a pair of 15" woofers in a sealed enclosure. A vented enclosure does give you more output as you have both the displacement of air by the driver and the port summation. The issue though is in balancing output per cabinet volume.

You clearly have not seen much about our drivers or what they are intended to do. We have been making probably the lowest distortion drivers available anywhere at any cost for several years now. Many of our clients are recording studios, companies that build recording studios, high end pro audio companies and high end home theater/hifi companies. Here is a brief list of some of our customers and what they do.

www.evolutionacoustics.com MMThree 15" woofers
www.audiokinesis.com TD12M's for Planetarium system
www.salksound.com TD12H for new open baffle system and upgraded 10" drivers to replace former TC wofoers
www.seatonsound.com 12" drivers for the catalyst that you can see in the following thread here http://www.avsforum.com/avs-vb/showthread.php?t=1094517
www.exigy.co.uk high end recording studios
www.chicagorecording.com subwoofer for Studio 4

Rightbrains Tremor Twins with AV15X, very similar to what was suggested above
http://www.avsforum.com/avs-vb/showthread.php?t=1106988

Recording monitors for Nick Barnett's TraxxSquad Productions
http://www.aespeakers.com/phpbb2/viewtopic.php?f=14&t=701

BaSSlines by dlneubec, inspired by the new Salk speaker. Look at Jeff Bagby's comments on the TD12H on the second page of the thread
http://www.htguide.com/forum/showthread.php4?t=29988

Several building high efficiency DIY main speakers in this thread
http://www.avsforum.com/avs-vb/showthread.php?t=1035126

MTM's using the TD10M's by Owen Columbus from Paradigm
http://www.diyaudio.com/forums/showthread.php?s=&threadid=132884

Most all of these people would be glad to give you their thoughts on the drivers we build. Jeff Bagby claims that the TD12H is the lowest distortion driver he has ever seen in the 30 yrs in the industry and that other drivers can't even begin to touch what it does. The simple reason is our effort to lower inductance, linearize inductance, eliminate flux modulation, and quickly transfer heat away from the VC. We do the same thing in our AV woofers as in the Lambda woofers. You can read about the Lambda motor design here, what it does, and why it greatly reduces distortion.

http://www.aespeakers.com/Lambda001-1.php

John

 

[John_E_Janowitz]

The Sound Splinter 15" is an excellent 15" driver of not much more cost than the AE driver you purchased. I refer to their low cost 15. It is produced/designed by TC Sounds/Audio Pulse - bar none the best/most capable sub manufacturer in the world, technically speaking, based on available third party measurements - they have the best measuring sub driver technology presently known. Now, the low cost 15 is not an example of their best tech - but it's extremely good for the price. I'm just pointing out the ability of TC Sounds. Sound Splinter also has an expensive 15 that used TC Sounds highest end tech (LMS motor), which will produce the highest sound quality possible even at the limits of excursion. Though, it may produce slightly less absolute SPL than the cheaper unit(which is more SPL oriented), it is superior in SQ at the SPL limits. The LMS based drivers from TC Sounds have a near perfect motor; virtually unheard of. It has a motor strength/characteristic that remains almost identical at 1mm vs. 25mm excursion, where as almost ANY other driver has a motor that changes in characteristics largely at different excursions(worsening at more excursion), resulting in distortion and other anomalies at moderate to high excursion/power. The AXIS driver that was referred to earlier is also a TC Sound driver; not using the LMS tech, but a very linear tech, and more geared towards combing high linearity with extreme SPL abilities. Then there is the full blown Ultra-LMS line with uses LMS tech combined with the ability to produce huge SPLs -- but these are extremely expensive and hard to get.

TC Sounds formerly made my drivers back in 2000-2003. Due to some "issues" I ended up having to build drivers in house. I'll just leave it at that.

The "genesis" of LMS was created back then when I proposed to thilo a different approach to get a flat BL curve than was done with XBL.
Here is the original sketch I did in paint before I learned to use any cad programs. In an article by William Burton in 2006 I was credited, along with Thilo and Deon Bearden for the original "genesis" of LMS.

LMS does have the ability to lower distortion created by non-linear BL. This is important at high excursions and at the lowest frequencies. However, higher up in frequency one of the biggest distortion issues is due to inductance variation and flux modulation. This is an issue that is increased with larger coils and with variable density to the windings. While the technology can be great for the lowest frequencies, it has some serious drawbacks at the higher frequencies which you can see by modeling with varied inductance to the driver. You trade one distortion for another. There is no perfect design.

The other drawback to LMS is the variable density coil requires wider gaps. The most common issue with flux modulation is in the air gap itself, so wider gap = higher flux modulation. Wider gap also means you need much more motor to get the same flux in the gap and cost goes up. This is why the LMS drivers are so expensive. If you were to compare the displacement per dollar of one of the large LMS woofers to our AV15's the AV's have much more bang per buck.

In addition to that, everything we build is fully built here in the US. After TC went bankrupt, they plan to do drivers only in China. We use alum cones spun in california, surrounds and spiders made in illinios, coils made in florida, gaskets made in indiana, adhesives made in illinois, steel parts are plated i milwaukee and some of our other cones come here in WI. Even our boxes and packaging are fully done in WI. We machine every piece of steel here in the US, finish all cones here, and assemble everything. All of this is done to keep strict control of not only the assembly but of every component put into the drivers. Every driver is broken in, listened to, and parameters are measured before they ever get packaged.


John

 

[John_E_Janowitz]

The AE AV15-X driver has some promising parameters. This is different from the one you purchased, however. Also, it's not really proven, measurably, as far as I know. Various TC Sounds drivers have been measured, and have been consistently phenomenal.

Take a look at the thread on the Tremor Twins posted above. Also for anyone in the SE Wisconsin area I'll have an AV15 with pair of 18" PR's at the Subwoofer Shootout on Saturday.

http://www.avsforum.com/avs-vb/showthread.php?t=1111483

I'm sure you'll hear some things about the AV15's after that. I'll also have our new TD18H+ driver which has 14mm Xmax and is 98dB 1W for prosound use.

John

 

[John_E_Janowitz]

It seems to me that one or two kappa perfect 12 drivers would give all the conceivable spl and bass reach you would need in any domestic environment.

How much bass people need is always a tough one. People often ask if what they are buying is enough and it's always hard to tell. I have done an infinite baffle system recently with 8 of our IB15's in a large theater room and for most people it would be ridiculous. Others may believe it is not enough. For a large room though, a pair of 12" drivers like the kappa perfects will likely not be enough. There are much better drivers, much lower distortion, lower inductance, better power compression out there.

I do find it somewhat interesting that the AV woofers were stated as "car woofers" when they aren't necessarily intended for that but at the same time the Kappa Perfects clearly are car woofers but they are recommended. Our AV12X has nearly identical motor strength to their "low Q" option while it has about only about 25% of the inductance and 40% more Xmax. It will also have significantly better heat transfer from the coil due to the thicker gap plate and full copper sleeve on the pole to pull heat from the coil quickly.

John

 

[VERTIGGO]

I've been toying with the dimensions again, and at 10 cu. ft. I won't be able to fit the 15" driver and 8" port in a design with those "magic" numbers (.7*1*1.4).

I could go with a similar design as the Tremor Twins... how much does the ratio matter? Isn't it just to ensure that they are different because of resonance?