What Enclosure For These Drivers?

[thetubeguy1954]

I have a pair of TC Sounds 15” Woofer that were designed especially for Jon Lane of Jon Lane Design. I've been told by the man I bought them from that they were modeled after an Altec design. I'd like to make a pair of matching subwoofers using these drivers.

They have cast four-legged frames, 3.5" flat wire coils, heavy copper Faraday motors with underhung geometry and precision machined gaps, vented poles, hard paper cones, cloth surrounds, flat lead-in wires woven into the rear suspension. Xmax is 10+ mm. They're supposed to be a pretty much no-holds barred, medium-to-high sensitivity 15" drivers. There designed TS specs are:

NomR: 12 ohms
Revc: 9.2 ohms
BL: 25.75 TM (!)
SPL: 94.25 dB
Qms: 6
Qes: .27
Qts: .25 ik
Vas: 355 litr.
Cms: 350 uM/N
Mms: 130 Gm.
Fs on these is under 25Hz.
===============================
The ACTUAL LAud TS measurements are:

‘A’ ‘B’
Fs: 24 Hz Fs: 24 Hz
Qt: 0.268 Qt: 0.284
Re: 9.5 Ohms Re: 9.5 Ohms
Qe: 0.268 Qe: 0.294
Qm: 9.460 Qm: 8.888

So can anyone help with enclosure type and the basic dimensions for making these a pair of subwoofers?

TIA.... Thetubeguy1954

[GM]

Hmm, no Altec I'm familiar with, but it's academic. With a relatively high Fs for true sub duty and too high a Vas (assuming it measures ~the same as spec'd) for a semi-reasonable box size, a large corner loaded EBS alignment tuned to ~16 Hz is about the smallest cab that will 'get down' with any authority, so do you have two corners relatively near the mains and how big can you handle?

GM

[thetubeguy1954]

Hello GM! Yes I have 2 corners open behind and fairly close to my main speakers. How large of an enclosure are we talking about?

Thetubeguy1954

[GM]

Greets!

Well, not as big as I guessed assuming the factory Vas spec, though the differing Qts specs combined with a lack of measured Vas forces me to use the larger of the two, so 'only' ~9.3 ft^3 net/16 Hz which means a long vent to keep vent mach low at 10 mm Xmax in 1/2 space. In 1/8th space it can theoretically be reduced, but I prefer to view it as increasing the driver's power handling beyond the calc'd 1/2 space 300 W/driver since even dual corner loaded they can't get to DD/DTS reference down low without more power due to their low Qts.

A simple MLTL helps us a bit though since its length reduces the vent's:

L = 60"
CSA = 281.95"^2
zdriver = at top
zport = at bottom
dport = 6"
Lport = 17"

All dims i.d. and approximate. Line one side, top, and back with either 1" acoustic fiberglass insulation or minimal polyfil (~37 oz) or similar stuffing its entire length. i.e. just enough to keep them from sounding hollow.

Assuming a typical <80 Hz XO point, fold it in half to place the driver, vent at floor level for max coupling and half of the required bracing is already done assuming 19 mm Baltic Birch plywood is used.

If a much higher XO point or low order slope is used, leave it unfolded and locate the driver down 24.25" i.d. from the top to get it around the same height as the mains speakers.

GM

[Ron E]

Vented box: each woofer
200 liters
1x 8" diameter vent, 20" long - or 4x 4" diameter vents.

These will easily take 250 Watts above ~20Hz - should be loud enough for ya.

[thetubeguy1954]

GM & Ron E, I'm very new to DIY and metric conversion. That said in an effort to determine how big the 200 liters enclosure you suggested is in square feet. I went online and used a metric conversion calculator.

I discovered that 1000 liters is 1 cubic meter or 10.76 cubic feet! I quickly realised 200 liters is 1/5 of 1000 liters. Which in turn also means I'd need 1/5 of 10.76 square feet which is 2.152 square feet!

So unless I've made a mistake in these calculations ---{which is certainly possible}--- I'm looking at an enclosure with approx internal dimensions of: 2.15' x 1' x 1' or a tad larger at 1.5' x 1.5' x 1'. But it seems that sqeezing in a 20" long vent is difficult unless I use a 90 degree bend.

GM does 9.3 ft^3 translate to 3.05' x 3.05' x 1' with a 6" diameter and a length of 17"?

I'm also curious as to how you both came to different dimensions using the same driver parameters?

Thetubeguy1954

[Ron E]

You don't need a converter, just google and plain english:
http://www.google.com/search?hl=en&q...=Google+Search

square feet is an area measurement
volume is measured in cubic feet (or liters )

Otherwise, you can remember that
1 foot = 0.3048 meters
cube both sides
1^3 ft^3 = .3048^3 m^3
--so:
1 ft^3 = 0.0283168466 m^3

divide both sides by .028....

35.3146667 ft^3 = 1 m^3

so 1/5th of a cubic meter (1000 liters in a cubic meter) is about 7 cubic feet.

Speaker design is an exercise in balancing tradeoffs. I chose different tradeoffs than GM. That doesn't mean that his design is wrong or mine is right, it is just different.

[Ron E]

Heres the curves you get with my design.

The deeper you try to push the bass, the higher the excursion above tuning is. This should mechanically handle ~250W above tuning - I don't know what your aims are or what the real power handling of the driver is. To arrive at an "optimal" design I would want to know amplification, and what your goals are.

BTW, a regular cookbook approach would give you:
Small/Margolis: 100 liters, tuned to 35Hz - F3 of 41Hz, F10 of 29Hz
Keele: 130 liters, tuned to 32 Hz - F3 of 37Hz, F10 of 26Hz

Mine gives F3 of 33Hz, F10 of 22Hz.

F3 is the half power point (-3dB)
F10 is the psychoacoustic bass cutoff (-10dB)

With vented boxes that you intend to pound on, it is best to use a subsonic filter. If you do that, you might consider a 6th order box - this driver would likely do that well. Look for Bullock's $10 book for formulas.

[thetubeguy1954]

Hello Again Ron! You stated that you don't know what my aims are or what the real power handling of the driver is.

I also don't know what the actual power handling of the driver is either. I'm running a pair of CarderSound Madisons aka Sachiko on the Frugel-Horn site. These are 8" single full range drivers loaded into a double BLH and are 96dB efficient. My amp is a Mastersound Reference 845 integrated SET @ 40W/ch.

So what's my aim? Well I'd like to add some real bass from 80-100Hz and lower that would blend well with my speakers. I listen ---{90% of the time}--- to smooth jazz & jazzy new age. However every now and then ---{10% of the time}--- my roots come out and I listen to prog rock like Yes, Marrilion, Starcastle, Genesis, Shooting Star etc.

Hopefully that give you a better idea of what I'm attempting to accomplish. Oh yes I should mention I'm not 100% committed to using the TC Sound woofers because I also have an 18" Hartley woofer. Maybe using the Hartley would be a better idea?

Thetubeguy1954

[Ron E]

Well, you have 4 data points there. If space is of more concern than bass, you might want to go with the smaller box. If you want the deepest bass possible with no concern for space, you might consider my design or GM's recommendation - although I haven't simulated his TQWT's or TL's. 40 Watts from a tube amp? I'd say you aren't worried about power handling .

The higher output impedance of the tube amps would give a higher effective Q so you would need to modify the designs (mine assume zero output impedance) Generally box size goes up and tuning frequency goes down.

If I were you I'd look at an active crossover and using a crystallized sand amplifier for the bass. Then you can match sensitivity and you don't have to worry about driver impedance in the crossover.

No experience with Hartley's.