Tapped Horn For Car

[Brian Steele]

Originally Posted by mwmkravchenko

Now the volume is 24" x 20" x 9" no what about 71 litres or 2.5 cubic feet. Quite a bit smaller than my last layout. The last one was 25 3/4" x 30 5/8" x 9" or 116 litres (4.1 cubic feet)

Whoa - that's a huge difference.

Mark, if you have the time (and the spare wood!), it might be interesting to find out how the Trio8 TH compares to a vented, 4th order or 6th order BP alignment with the same drivers that occupies the same or less net volume.

[mwmkravchenko]

Hi Brian.

You come up with the box design and I will knockt off. I have some other jobs to do. Bipole surround, fullrange using EL70's and SDX7's, and a UNHORN4 using TRIO12's. So get in line buddy!

Your idea will not take to long. But save the time and read Geedes paper on bandpass designs. I read it so long ago, but if I remember correctly he only got 7db gain from the box. This should get close to 9db gain. Rember this is not a tapped horn but a bandpass/horn hybrid (I think anyway).

That's my trick for making such a small box work at such a high efficiency at least according to the modeling. Now I have another prototype to play with.

Mark
Mark

[Brian Steele]

Originally Posted by mwmkravchenko

You come up with the box design and I will knockt off. I have some other jobs to do. Bipole surround, fullrange using EL70's and SDX7's, and a UNHORN4 using TRIO12's. So get in line buddy!

LOL. Trio12s, eh? I better not add to your workload then - 'cause I'd LOVE to hear your feedback on those drivers . The only ones more interesting specs-wise is the Earthquake SWS-12X with its published 31mm Xmax, available at around the same price from SonicElectronix - see Earthquake Sound SWS-12X (Black) (sws12x) 12" Subwoofers Car Subwoofers Car Audio Car Audio, Video, & GPS Navigation - Sonic Electronix . It's shallow profile should provide a bit more flexibility wrt box design, and it is more efficient, but whether that 31mm Xmax spec for such a shallow driver is actually realistic is another matter .

Originally Posted by mwmkravchenko

But save the time and read Geedes paper on bandpass designs. I read it so long ago, but if I remember correctly he only got 7db gain from the box. This should get close to 9db gain. Rember this is not a tapped horn but a bandpass/horn hybrid (I think anyway).

I typically avoid designing high-gain bandpass alignments in any case. What's the target F3 point of your Trio8 design, btw, and it's 2*PI passband efficiency?

[mwmkravchenko]

Hi Brian

2Pi is 93 db

Low end is 30hz highend is 110hz.

Mark

[mwmkravchenko]

Hi Brian

The TRIO12's and the specs are conservative. It is a very well made driver. And price wise I think it is cheaper.

As for the Earthquake driver I've ran it through WinISD and Driver Parameter Calculator and it doesn't fair so well. Over stated SPL to begin with as 2.83 volts is more than 1 watt through 6 ohm nominal impedance.

Mark

[Don Hills]

Mark,
I've converted your picture to an AkAbak script. The result is encouraging. See the attached images. One shows AkAbak's sound pressure measurement with the drivers at maximum rated power (200 watts each), the other shows the impedance curve.

The lowest impedance is 3.2 ohms, so a 2 ohm capable amplifier rated at 300 to 400 watts into 4 ohms would be suitable.

The system is power limited down to 26 Hz, below which it is excursion limited. Based on the driver Xmech figure it should handle up to about an 80 watt amplifier without excursion damage, but a high pass filter will be essential if you want to run high power.

I'm looking forward to the in-car and in-lounge measurements.

[Brian Steele]

Originally Posted by Don Hills

Mark,
I've converted your picture to an AkAbak script. The result is encouraging. See the attached images. One shows AkAbak's sound pressure measurement with the drivers at maximum rated power (200 watts each), the other shows the impedance curve.

Damn - that looks nice. 2*PI or 0.5*PI? What's the output look like at 2.83V?

[mwmkravchenko]

Now this is encouraging! Thanks for taking the time to work this out Don. And for posting your findings. I may not be completely crazy after all eh?

After David McBean made it possible to export the Hornresp data directly to AkaBak it became much easier to get the crazy program to work. I thought for a couple pf days when I was working how to lay this out so that I could respect the actual driver placement. None to easy of a task mind you. But I think this is the best setup I can come up with.

The box is dry and I will have some time this weekend to mess around with it and take measurements. I'm expecting this one to really behave itself. It is crazy to think that the lst box with the block moving around in the end had quite a visceral impact when used in room. This one with no obstructions should be a real butt kicker.

Can't wait! Just gotta get me some closed cell weather stripping tape. Then I can fold up the top on the box and take it for a test spin.

My boys both commented on the more open and articulate sound with the previous box. I missed the real bottom end I never really got out of it. I was hoping for gut smacking 30 hz. But when I got close I thought it was a design compromise that robbed me of my prize. An ill place block of wood will get you every time! No more quicky jobs. This has to work the first time. I had a hell of a time taking the box apart. So this one is put together like a cabinet maker should. ( right the first time!)

Mark

[mwmkravchenko]

Hi Brian

I've got one phrase for you.

In the immortal words of gollumn:

Miiiine!



Mark

[mwmkravchenko]

Here are some figures Brian. Maximum power is first.

Mark