MFW-15: Ported vs Horn - AVS Forum
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post #1 of 16 Old 06-28-2013, 07:25 AM - Thread Starter
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I don't have the screenshot here, but I was playing around in Hornresp, and the MFW15 in a 7 cubic foot ported (22hz tune) enclosure actually came surprisingly close to the horn F20 model. Wondering if I am doing something wrong in hornresp, or is the MFW that good with ported? I checked and they were both at 0.5 pi..
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post #2 of 16 Old 06-28-2013, 09:27 AM
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First, don't model in 0.5 pi, the results tend to be a bit optimistic.

But, to answer your question, yes, simulations of an MFW in a proper ported cabinet get close to the F-20.

That's really not surprising, as the driver was designed to be used in a ported cabinet tuned near 20 Hz.

However, in the real world, you'll find that ports will start to compress with higher power, and while horns do too, it isn't as bad.
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post #3 of 16 Old 06-28-2013, 10:16 AM
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Quote:
Originally Posted by diaz View Post

I don't have the screenshot here, but I was playing around in Hornresp, and the MFW15 in a 7 cubic foot ported (22hz tune) enclosure actually came surprisingly close to the horn F20 model. Wondering if I am doing something wrong in hornresp, or is the MFW that good with ported? I checked and they were both at 0.5 pi..
I can't say with respect to the F20, but the THT ranges from 6 to 10dB higher. If it didn't there wouldn't be much point in the added size and complexity of the horn.

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post #4 of 16 Old 06-28-2013, 12:55 PM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

I can't say with respect to the F20, but the THT ranges from 6 to 10dB higher. If it didn't there wouldn't be much point in the added size and complexity of the horn.

Maybe I entered something wrong?

Here are my parameters, grey shows the ported MFW, and the black is the F20 - both 2.0 pi:

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post #5 of 16 Old 06-28-2013, 01:32 PM
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Simulations are only part of it. Remember, the F-20 measured a bit better than it simulated. I measured ~95 dB at a meter with 2.00 volts.

As far as the ported sim? Things look OK, except that the port is far too small for a 15.

Sd/2 is about you should aim for in a sub, Sd/3 as a minimum. You're less than Sd/5.
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post #6 of 16 Old 06-28-2013, 02:06 PM - Thread Starter
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Thanks, ill adjust the port volume smile.gif
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post #7 of 16 Old 06-28-2013, 04:34 PM - Thread Starter
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now I'm wondering if I'm not getting the combined output of the horn and the speaker.for some reason I can't get combined output when I select front-loaded horn.

Does hornresp include both speaker and horn mouth spl output?
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post #8 of 16 Old 06-28-2013, 05:56 PM - Thread Starter
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Ok found the huge factor... the ported MFW does awesome up to about 25 watts, where it hits Xmax extremely early under 20hz. It needs a really steep HP filter which completely kills any response up to about 23-25 hz.

The sealed cabinet inside the F20 though, would require about 300watts to reach the xmax. At this point you are looking at much more dB output.
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post #9 of 16 Old 06-28-2013, 06:52 PM
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Quote:
Originally Posted by diaz View Post

now I'm wondering if I'm not getting the combined output of the horn and the speaker.for some reason I can't get combined output when I select front-loaded horn.
There is nothing to combine, the only output you get from a front loaded horn is the horn output.

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post #10 of 16 Old 06-28-2013, 09:17 PM
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"I don't have the screenshot here, but I was playing around in Hornresp, and the MFW15 in a 7 cubic foot ported (22hz tune) enclosure actually came surprisingly close to the horn F20 model. Wondering if I am doing something wrong in hornresp, or is the MFW that good with ported? I checked and they were both at 0.5 pi.."

i performed a similar comparison just a few days ago
and got similar results. the spl advantage of the
horn is only marginal at the bottom end. a ported cab
vs. a tht only gives up about 1db in sensitivity at 30hz.

the high sensitivity advantage of the horn comes toward the
top end of the response. max spl is a little different story.
the horns have about 5-6db advantage there where the ported
is excursion limited (the 30hz ballyard) for a ported cab
close comparable to a tht. the same would be true for the
f20, but a little lower in frequency. like lilmike noted,
horns don't have port compression or chuffing to worry
about, which is another advantage.

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post #11 of 16 Old 06-29-2013, 06:05 AM
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Quote:
Originally Posted by LTD02 View Post

horn is only marginal at the bottom end. a ported cab
vs. a tht only gives up about 1db in sensitivity at 30hz.
If you got that result then your THT model isn't accurate. That aside, sensitivity alone doesn't tell the entire story by any means. The difference in excursion between the two is major, and the difference in THD greater still.

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post #12 of 16 Old 06-29-2013, 06:30 AM
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Quote:
Originally Posted by diaz View Post

Ok found the huge factor... the ported MFW does awesome up to about 25 watts, where it hits Xmax extremely early under 20hz
That's just an inherent weakness of a ported cab. To put it simply, an octave or so above the tuning frequency, the ported enclosure acts like a large sealed enclosure. Approaching the tuning point, the port takes over and excursion drops. Below the tuning point, the enclosure neither fuctions as a sealed enclosure (like it does above tuning), or like a helmholtz resonator (at tuning point), but instead acts like a box with a big leaky hole in it. There's nothing to resist the speaker cone's movement. That's why folks talk about getting a highpass filter to protect the driver.

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post #13 of 16 Old 06-29-2013, 09:31 AM
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"If you got that result then your THT model isn't accurate."

i used the model that you posted on your website bill, but in 2pi space with 1 watt, not 2.83v and 0.5 space.

model up a ported enclosure, tune it to have a peak in the low corner and you will see.

"That aside, sensitivity alone doesn't tell the entire story by any means."

i agree. that is what i was talking about with max spl. higher with the
larger horn.

"the difference in THD greater still."

isn't thd kind of irrelevant for subwoofer frequencies?

it seems the threshold for audibility is rather high
for thd in subwoofer frequencies, something like 50-100%
before it is detectable with program content.

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post #14 of 16 Old 06-29-2013, 09:51 AM
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top plot: tuba ht model with 2.83v 0.5 space
bottom plot: my guess of tht with 2.83v 0.5 space



tht dialed down to 1 watt and 2.0 space



7 cubic foot ported enclosure with similar low corner also 1 watt and 2.0 space
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post #15 of 16 Old 06-29-2013, 02:10 PM
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Quote:
Originally Posted by LTD02 View Post

"If you got that result then your THT model isn't accurate."

i used the model that you posted on your website bill, but in 2pi space with 1 watt, not 2.83v and 0.5 space.
I don't post models on my website. Any SPL charts I post are measured, not modeled.
Quote:
it seems the threshold for audibility is rather high
for thd in subwoofer frequencies, something like 50-100%
before it is detectable with program content.
It's quite audible at even 5% when you're hearing above bandwidth harmonics.

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post #16 of 16 Old 06-29-2013, 05:14 PM
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"I don't post models on my website. Any SPL charts I post are measured, not modeled."

i'm not sure where i got it from, but it was definitely from you.

you mentioned that it was the old tempest driver and the that dayton dvc385-88 is
essentially the same.

i modeled up the dayton dvc385-88 and got exactly the same thing that you posted.

i see that you discussed the tht model several years ago on audio asylum.




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