Complementary Subwoofers

[MacKevin]

Like a lot of you I've been looking to increase the bass in my LaScala's. I've now given in to idea that I need a subwoofer. To save space I want to build two subwoofers that I can place under the LaScala's. I'm hoping that they fit the same foot print and do not exceed 2" tall and have a complementary db output and throw. I was wondering if anyone has came accross such a subwoofer before. I really want to build these so if anyone knows of a design that fits that spec I am very interested.

Thanks

Kevin

[capo72]

----------------

On 6/20/2005 7:29:45 AM MacKevin wrote:

I'm hoping that they fit the same foot print and do not exceed 2" tall

----------------

2 inches in height is gonna be tough. Heck using 3/4" MDF is gonna eat up 1 1/2" Someone makes an inwall sub (2 10" drivers I believe. That would be 3 1/2" to 4" deep. If you mean 2 feet then your options are wide open.

Jeremy

[tofu]

im pretty sure he meant 2 feet

[formica]

He could have also meant 12" ... and just a typo. I agree that the options are almost limitless for 24" tall (ie: 8ft3 box under each LaScala)

[DrWho]

A budget would be nice too...I'm picturing 2 tumults per side powered with two thousand watts

that would be about -3dB @ 20Hz and 123dB maxSPL

[mike stehr]

"A budget would be nice too...I'm picturing 2 tumults per side powered with two thousand watts

that would be about -3dB @ 20Hz and 123dB maxSPL"

A friend of mine has two of these in ported 16 Hz enclosures, it takes 2500 watts per side to get 125 decibels @ 20 Hz using a Termlab meter.

It takes like two or three seconds to trigger the meter, and a level of 120 Db.

The Peavey amps used were pretty much fully clipped with the Tumults at full wang to get that 125 Db number.

Dunno what sort of home you have, but two Tumults at those power levels are earthquake simulators in a pad.

That's a lot of power if you think about it.

[DrWho]

You're right...4 tumults and 5000 watts would be more appropriate

[colterphoto1]

oh, sorry I misread, I thought someone was giving away complImentary subwoofers at no charge. sorry.

Michael

[MacKevin]

Now that I have returned to what I hoped would be useful info, imagine my suprise when I discovered that most of you have checked your brains for the summer. Yes you be correct, I meant 24" but I could accept 28" and the budget would be the price of the drivers, JBL pro 18" or 15" I hope, plus wood and hardware. I'll take care of the amp and active crossover.

I hope this helps to put this discussion back on course.

Oh PS I am sending you the complementary Subwoofers in the mail now, just sit by you mailbox everyday and wait for them, because they will be worth it.

[Colin]

DIY Parts Express Titan III $700!

[formica]

Ok, forgive me if I post info you already know, as I'm unfamiliar with your knowledge when it comes to subwoofers.

First off, I find 24" too tall for a sub you will place underneath your LaScalas as it'll raise the tweeter level too much Total cabinet height would be close to 5 feet. I even find the Khorns to be already maxed out in terms of height and it's only 52" tall. If we start with this number... you'll get a 16-1/2" (to 18") sub box, which will accept a 15" driver.

So the way I figure it you'll need a 15" driver that will work well in a ported 5.5ft3 enclosure. I'd recommend just one driver per side, simply because 5.5ft3 isn't large enough for two common subwoofers and still get good bass extension.

There aren't any pro JBL drivers which attract me at the moment, as most are optimised for SPL with reduced bass extension. Since you will be using these in the home in a subwoofer rather than in a bass bin, sacrificing a little SPL for Hz seems like a good idea. You will find many pro drivers are limited by the same design optimisations, with an occasional exception like the 18" McCauley that John Warren used for his sub... but it quite expensive and requires a HUGE enclosure.

There are several new DIY subwoofer drivers coming out in the following months, but selection is a little limited at the moment. Being in Canada, it complicated the selection even more.

- Adire Audio: The discontinued Tumult would have functioned well in that combination (one Tumult per side in a 5.5ft3 box tuned to about 19Hz... will give you a F3 of about 18-1/2Hz)) The new Adire Audio Tumults are not yet available.... but they have several Canadian distributors.

- Acoustic Elegance: The AV15... may be less powerful that the Tumult but it is more efficient. They are currently available from the US with flexible shipping. (one AV15 per side in a 5.5ft3 box tuned to about 19Hz... will give you a F3 of about 20Hz)

- Parts Express: The Dayton Titanic can also provide good results without breaking the bank, but Part's Express isn't flexible when shipping to Canada. I didn't get around to modeling this one...

- Etc...

You should try out a couple of drivers in WinISD (freeware) subwoofer modeler, and get a feel of what will work best for you.

In any case, LaScalas really need a subwoofer to shine, you can't go wrong in adding one.

Rob

PS: I'll be waiting for that free sub to arrive...

[DrWho]

Here are some links to get you started:

http://www.acoustic-visions.com

http://yellow.mynethost.com/~bv126368/shop/catalog

The Tumult would be my favorite choice and it'd prob be the last time you ever bought a subwoofer. The reason they are "discontinued" is because Adire Audio is changing the way they do things and they're coming out with a completely new lineup for all their drivers. They've been "coming soon" for a while now, but I can't imagine it taking that much longer.

The AE AV15 would be my second choice followed closely by the Dayton. The AV15 has a flatter response and can be used in bigger cabinets tuned lower if you ever felt like improving their performance. The Dayton has more power-handling but the mechanical limitations for both are pretty much the same (The dayton will be about 1dB louder). I've never heard either so can't comment on their musicality or watever. I believe the AV15 is much cheaper though.

Another option I would consider would be putting two AE IB15's loaded isobarically into each cabinet ($100 each). With room gain you'd get solid output down into the teens (where the other ported drivers would be distorting due to exceeding x-max). Sealed cabinets are also generally considered to be more musical sounding and they're incredibly much easier and cheaper to build. The only downside here is less max SPL than the other options available.

[jorjen]

Sheeesh, and I thought by the thread title someone was giving away free subwoofers.

[MacKevin]

Thanks for your reply, it kept me busy most of this evening. To be honest with you the Subwoofer design that I am most interested in building is along the lines of this

It seems to capture all the "OLD Man Ideas" that I have. Low distortion rigid cone, ported enclosure, front loaded driver, and tuned to about 25Hz. If anyone knows to plans for a subwoofer design similar to this one with either a 15" or 18" driver I am very interested.

Kevin

[DrWho]

----------------

On 6/22/2005 8:06:55 PM MacKevin wrote:

Thanks for your reply, it kept me busy most of this evening. To be honest with you the Subwoofer design that I am most interested in building is along the lines of this

It seems to capture all the "OLD Man Ideas" that I have. Low distortion rigid cone, ported enclosure, front loaded driver, and tuned to about 25Hz. If anyone knows to plans for a subwoofer design similar to this one with either a 15" or 18" driver I am very interested.

Kevin

----------------

Well here's a design you might be interested in...instead of using ports, it uses passive radiators which allow lower tunings with less compromises. A port needs to be rather large for the lower tunings in order to keep the air velocity in the port low enough to not be audible. In a PA setting (like the pictured sub was intended for), port noise isn't as large of a concern because it's not audible above all the crowd noise. Granted a port with a larger surface area can be used, but it would also require a large increase in length as well. You simply can't fit a port tuned this low inside a cabinet this size while also keeping the port noise at an acceptable level. So all that said, I would propose using passive radiators instead which are entirely identical in concept and application. So instead of a mass of air, it's the mass of a diaphragm (just like klipsch uses in their reference sub lineup). I hesitate mentioning all this though because you want an "old man idea" approach and I didn't want to be misleading and make it seem like a passive radiator isn't "old man" - It very much is the exact same thing, but with some added benefits for this kind of situation. The only downside is that it's a bit more expensive.

Ok, so here's the design:

AE Speakers AV15 ($180 x 1)

PR15-700 ($70 x 2)

Grand total for both lascalas is $320 x 2 = $640 + tax/shipping. Add another $60-$100 for the construction of the cabinets depending on what kind of finish you go with. The iron on laminates at partsexpress look interesting.

The cabinet should be 18" tall with the same dimensions as the lascala (so basically 18x24x24), which yields close to a 6 cubic foot internal volume. Mount the active driver on the front of the cabinet and then mount two passive radiators, one on each side. With this setup you're looking at a tuning of 21Hz, -3dB @ 19Hz and a max SPL of 110dB @ 20Hz / 115dB @ 60Hz for just one side. With both running it'd be 116dB @ 20Hz / 121dB @ 60Hz. And then with room gain you'll get even better numbers.

As far as powering the suckers, all you'll need is an amp capable of 400 watts into 8 ohms per channel (or 200 watts bridged mono into 4 ohms if you wire them in parallel). I am curious as to what you already have in mind...

Anyways, the grand total comes to about $1000 (including amp), which I feel is a great bargin considering the performance you'll get. If you don't like the AV15 driver, then you can swap it out for a Dayton Titanic 15" MKIII and get almost identical performance. I wouldn't recommend any "better" driver for this setup otherwise you start running into the excursion limitations of the passive radiators. But who needs more than 120dB anyway?

Here's how the two drivers model up:

Pink = AV15 _____________________________________ Blue = Titanic

[formica]

Ok, I'll add a couple of additional points to put you in the right direction. The actual shape and aesthetics of the enclosure is entirely up to the builder... the only critical items are:

- Driver (and it's T/S parameters)

- Enclosure's internal volume

- Port tuning:

1) the port's length and cross section area if a vented

2) the PR's T/S parameters if using a passive radiator

That is why our suggestion do not include actual plans... just global designs. It would be a good idea to understand "Hoffman's Iron Law" which relates the three basic characteristics of a bass box: the efficiency of a woofer system (1) is directly proportional to its cabinet volume (2) and the cube of its cutoff frequency (3) ie: the lowest frequency it can usefully reproduce.

Hoffman's Iron Law

So you already have an approximate volume. Since this will be used in a home, you aren't "overly concerned" with efficiency as you would be if using them in a commercial array, so it's safe to assume you can sacrifice efficiency for bass extension.

----------------

On 6/22/2005 8:06:55 PM MacKevin wrote:

It seems to capture all the "OLD Man Ideas" that I have. Low distortion rigid cone, ported enclosure, front loaded driver, and tuned to about 25Hz. If anyone knows to plans for a subwoofer design similar to this one with either a 15" or 18" driver I am very interested.

----------------

I see no problem with a front loaded driver and a slot port. Depending on the driver you choose, you should have enough enclosure volume to fit a convention port tuned to ±20Hz without port noise. You can wrap the port inside the enclosure like Klipsch does with the Klipsch KW-120-THX

As for the "low distortion rigid cone"... Technically, all subwoofer cones are rigid whether they use treated paper, aluminium, carbon fibre, etc... but I have the feeling you are referring to the pleated cloth surround? Or perhaps the spider construction? ... In either case I feel you are incorrectly judging a book by it's cover. You need a driver that performs well as a subwoofer and not in just a bass bin... so you need to looks at it's T/S parameters.

A basic variable is the driver's Fs (resonant frequency) which needs to be low to minimise distortion at low frequencies you'll be asking from it. You'll also need sufficient Xmax (excursion) to allow the driver to reproduce these same frequencies without bottoming out. Pleated cloth, in general, is used in drivers with tooo high a Fs and small Xmax to achieve respectable output as a subwoofer.

I do agree that pleated cloth surrounds look nifty though. For appearance, you may want to use the PartExpress Dayton as it uses a treated paper cone and looks more discrete compared to the AV15's aluminium cone. If you go with either one, make sure you get it shipped USPS to avoid high brokeage fees UPS charges with std shipping. I know Acoustic Elegance will do that for you (I've order 7 drivers so far from them to Canada) but for the Dayton you'll have to get it from Kyle at Acoustic Visions rather than through PartExpress... as he can send it to you by the method of your choice.

I built my subwoofer to match my Cornwalls and uses a AV15 driver in a 6.5ft3 enclosure tuned to 19.5Hz. I opted for tall and narrow, but that's up to the builder.

Later...

Rob

[DrWho]

----------------

On 6/23/2005 12:36:43 PM formica wrote:

I see no problem with a front loaded driver and a slot port. Depending on the driver you choose, you should have enough enclosure volume to fit a convention port tuned to ±20Hz without port noise. You can

wrap the port inside

the enclosure like Klipsch does with the

Klipsch KW-120-THX

----------------

When I modelled the driver, the lowest air velocity I could obtain in the enclosure was about 40 m/s...I've read that the goal is to at least be under 20 and the ideal is around 10m/s.

I was actually talking to Deon from klipsch the other day about all the subwoofers he's built and he was telling me how the bent port in the Ultra lineup was actually a compromise. He originally wanted to go with a passive radiator system, but the sales guys didn't want to have to put up with training their dealers on how to set it up (they didn't want to deal with the old "how far from the wall?" question). He said something along the lines that a properly tuned PR system is way better than a severely compromised ported enclosure, but in the end he had to make the compromise.

Nevertheless, that's not to say that the ultra lineup sounds bad or anything. I have a feeling that introducing a bend in the port would throw the calculated tuning off a bit, which would then require the ability to experiment and manually tune the port (unless somebody can model how a bend affects the tuning). The way I look at it, why introduce something that would requiring tweaking out a flaw when you could just go ahead and do it a good way to begin with.

Btw, the reason I mentioned to go with a 6 cubic foot cabinet is because changing the volume of the cabinet also changes the tuning at the same time...which also affects the excursion of the PR's as well. Anywhere between 5 and 8 cubic feet gives you something to work with...the larger cabinet digs deeper, but also sacrifices max SPL. 6 cubic feet just seemed to be a happy medium (and it only raises the mains by 18 inches, which brings you to just 1" taller than the khorn).

[colterphoto1]

That looks a LOT like an EV TL bin, used for PA systems for years. EV freely distributes the plans. There is a model for their 12, 15, 18 woofers. I think they use the series EVM-??L, which is a Low frequency PA driver, NOT a guitar speaker. Not sure of the response, but in the port, there is a removeable panel which can be used to de tune for a lower response at slightly less efficiency and smoothness.

TL606 seems to ring a bell for the 15" model.

Michael

[JohnA]

Dr Who's design will do what you need. A pair will not be too much.

I use 2 VMPS Larger Subwoofers (also available in kit form) powered by an Acurus A250 (400+ wpc into the 4 ohm VMPS). Each is in the corner behind my La Scalas. They are -4 db in my room at 16 Hz. They are a low distortion design with a 15" passive radiator and 2 active woofers. I do NOT have too much subwoofer. In fact, the subs do well to keep up with my La Scalas when they are cranked. I could use another 1000 wpc to be sure.

[formica]

I did notice a tendency in Deon's PR ported creations... but I do believe both methods have their advantages and disadvantages.

----------------

On 6/23/2005 5:46:27 PM DrWho wrote:

... properly tuned PR system is way better than a severely compromised ported enclosure

----------------

OTOH, a properly tuned vented system is way better than a severely compromised PR enclosure is also true. Both an open vent and a PR can produce very good results when done properly... and both suffer from sensitivity to proper design.

As with balancing the size/extension/efficiency... porting has it's own (less defined) series of compromises. While a vent may additionally run the risk of "port noise" the PR system suffers from the mechanical characteristics of the drone as well as it's excursion limitation.

----------------

On 6/23/2005 5:46:27 PM DrWho wrote:

I have a feeling that introducing a bend in the port would throw the calculated tuning off a bit, which would then require the ability to experiment and manually tune the port (unless somebody can model how a bend affects the tuning).

----------------

I think that unless you can properly measure your specific drivers' T/S parameters, you'll require a "tuneable system". BTW, I seem to remember some testing that showed that if the ratio of the mass of air vs- the x-sectional area of the port remained the same, it's tuning remained almost unchanged... with or without simple bends.

In any case, no free lunch... but both can work.

Rob