MLTL for "Hemptone" FR8? Pretty Please.

[G]

Would someone be kind enough to run a sim on the "hemptone" FR8 mounted in a MLTL? The specs are below. I realize the cabinets will be large but I'm hoping not too large.

Specifications and Small Signal Parameters
Voice Coil Impedance: 8 ohm
Resonant Frequency: 40 Hz
Frequency Response: fo - 20k Hz
Sensitivity: 93 dB SPL (Average 500 - 2.5 kHz, 1w, 1 meter)
Rated Power: 45 watts
Program Power: 90 watts
Magnet Weight: 566 gr (20 oz)
Net Weight: 1.5 kg (3.3 lb)
Fo: 40 Hz
Re: 6.2 ohm
Qts: 0.45
Qms: 3.5
Qes: 0.53
Vas: 88 Liter
Mms: 12 Gram
Xmax: 1.9 mm
No: 1.10%

[tinitus]

I think Scott has shown one in a BIB thread, and if i recall correctly it is HUGE, or maybe it was GM ?
But theres also Scotts BVR "spawn, BRUCE"(Planet10), if its been tested ?

[VadimB]

Hi Gavin,

The T/S parameters you have are from the manufacturer. Here is what I've measured on the drivers I have - see attached picture. The pair measured pretty close to each other.

I've tried to model MLTL for them, but did not like it. I don't remember all the details at this point. The model is on my home PC - will look it up when I get home. I think the main problem was - it required a heavy BSC attenuation, which kills the efficiency. I end up with the horn, that doesn't need the BSC at all and is about 95dB efficient. The box ended up smaller than MLTL. You can read about the design here:
http://www.e-speakers.com/pdf/vadim-infopack.pdf

[Scottmoose]

I knew someone was going to ask this...

One quasi MLTL. 14.5in wide, 8in deep, 48in tall (internal dimensions). Zdriver 10.25in. Port 2in up from the base on the front panel, 3in diameter, 3in long. Stuff 0.2lbs ft^3 from the top 24in down. Increase the port length to 4in to roll things off a little more. As we've gone wide-baffle with this, it's unlikely to need much in the way of baffle-step compensation, if any at all. Step-point occurs at 285Hz (assuming 3/4in material is used for a 16in wide baffle, external), which should be rapidly countered by room-gain, particularly if positioned near a rear wall. If they're pulled out a ways into a big room, and it bothers you (unlikely I suspect, then parallel a 2.6ohm resistor with a 1.4mH inductor in the hot lead, which shouldn't cripple efficiency too badly. BTW -give the edges a decent round-over -at least 1in.

Using the manufacturers claimed T/S parameters gives the following FR.

Scott

[Scottmoose]

And using the above measurements supplied by Vladim (thanks for that) the same cabinet gives the attached. Both are rolled off to compensate for room-gain BTW, as I always do. I can't see much that's bad about either to be honest. Port velocity stays well below the mach, so no noise, the FR is smooth, impedence isn't too bad, plenty of sensitivity.

Of course, the slight downside is that they're not exactly small boxes, but as they're wide baffles, which are best near rear walls & corners anyway, they shouldn't be too obtrusive either with a little creativity.

[VadimB]

Scott,

Using a wide baffle for this driver seems like a very good idea. AFAIR, I've modeled 12" baffle for MLTL and it looked worst. Also, I probably used the term BSC a little wrong. On top of usual baffle step, this driver has a rize in response from about 800 Hz to about 3kHz - all of it's own. I've used BSC term, because you can fight both of those in the same way.
The far-field FR of the driver mounted in my horn is attached. Please, disregard anything below 500-600 Hz.
By adjusting the size of the CC and horn damping, it was possible to mate a response of the horn mouth to the direct radiation from the driver, to end-up with some resemblance of a flat overall FR.
Another problem I remember with MLTL for this driver, was excursion, limiting the input power to a few watts anywhere below 100-80 Hz. Did you check your sim for that?

Vadim B.

[GM]

Greets!

I see Scott's been busy, but I started this in the wee hours waiting on the 'Sandman', so might as well post it:

First things first, Qts = 0.461 and Sd is unrealistically large to reach a 12 g Mms, so like the previous version, this one likely has a considerably higher Fs than listed. Fortunately that's not normally a big deal with a TL or MLTL......

Max flat MLTL:

L = 57.5"
CSA = 144"^2 (recommend 15.25" W x 9.43" D)
zdriver = 21.48"
vent = 5" dia. x 2.5" near/at the bottom

Sim is with minimal damping around driver and if 'boomy' in-room, either more damping and/or a longer vent can be used to roll it off. At 8", it sims identical to this one: http://www.diyaudio.com/forums/attac...amp=1175270122

GM

[Scottmoose]

Nice... wish I could get 'em as good as that without damping. I try nbot to go above 0.25lbs ft^3 now. Kills dynamics.

Excursion on mine was within Xmax to ~41Hz. Below that it rises a little, but nothing to get too worried about given our acuity drop-off. As sensitivity is fairly decent, it shouldn't be too much of an issue. I prefer horns myself, but not everyone likes / wants them, (as evidenced by the request) so I reckon the MLTL is the next best option.

[VadimB]

Excursion on mine was within Xmax to ~41Hz.

Scott, is this at 1W input power?
What happens if you increase power to 10W?

Vadim

[GM]

Greets!

Yeah, for sims I try to limit it 0.2 lbs/ft^3 to just below the driver, though for high Q drivers have to use a bit more and for drivers that require really large vents, then a more labor intensive ML-horn is preferred since its vent harmonics decay faster. Still, none of these will handle much power, so for the 'headbangers' who don't mind the limited LF of a live rock, etc., concert, a boosted mid-bass is the 'Hot Ticket':

GM