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Old 19th September 2018, 08:33 AM   #11
KaffiMann is offline KaffiMann  Norway
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OH!
I am sorry, there is a peak at the low end, my sim was wrong.
I had somehow written 6,4ohm dc resistance instead of 5,1ohm.

I will revise the simulation.

Edit:
At any rate, it was just intended as an indication that the goal is possible, I do not have any intention of using the Faital Pro 12FH530, it was just a random driver that seemed to give "ok" results. I would rather pick a driver with different values.
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Last edited by KaffiMann; 19th September 2018 at 08:43 AM.
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Old 19th September 2018, 09:21 AM   #12
mbrennwa is offline mbrennwa  Switzerland
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Originally Posted by KaffiMann View Post
It is not so easy to use bass reflex as "Type of design", I am not familiar with AJ horn, but hornresp and MJK's excel sheets are good, use horn simulation software, do not use bass reflex software. It is a slot port design.
If you want I can try and get an Akabak simulation going to verify, but I got so consistent results from hornresp that I stopped verifying, it may take some time to do this, have not used it for some years.

And I like to have the combined phase from port and driver together, it is hard to get good (PROPER!) results with bass reflex software.

Edit:
Do you mind posting the data you entered into AJ horn? Maybe the dimensions are different?
AJ Horn does the "generalised transmission line approach". It links the different box units by their acoustic impedances to model the system. It is not the "classical bass reflex equation" program. I attached my inputs and the outputs (SPL at 1m, sum of driver + port, free space).

The box input screen may look a bit funky when your brain is wired to bass reflex. It works by linking the driver to a box with a volume of 59 L, and this box is then linked to a tube (44cm² cross section, 10cm long). The tube looks like a "horn" on the input screen, but it really is the bass reflex port.
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File Type: png monkeybox_faital12FH530_driver.png (13.0 KB, 444 views)
File Type: png monkeybox_faital12FH530_box.png (10.7 KB, 440 views)
File Type: png monkeybox_faital12FH530_curves.png (15.7 KB, 442 views)
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Old 19th September 2018, 09:40 AM   #13
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by KaffiMann View Post
OH!
I am sorry, there is a peak at the low end, my sim was wrong.
I had somehow written 6,4ohm dc resistance instead of 5,1ohm.

I will revise the simulation.
I just tried AJ Horn with 5.1 Ohm (correct, black curve) and 6.4 Ohm (wrong value, red curve). The difference is not very large. I believe the difference between our simulations is somewhere else.

If you could provide your 5.1 Ohm simulation I will ask the developer of AJ Horn about his opinion on this.
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Old 19th September 2018, 10:11 AM   #14
Luke is offline Luke  New Zealand
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Why is a clone midrange $1K for a pair? Are the VOLT VM752 really so good?
Is it a good idea to have two of the Fane Sovereign Pro 10-300 4 ohms in series, that will likely go low.
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Old 19th September 2018, 10:40 AM   #15
KaffiMann is offline KaffiMann  Norway
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mbrennwa:
The port I used for simulation is over 36cm long, not 10cm. And it's 33,1cm wide (divider in the middle for bracing) * 4cm tall, so 132,4cm2. It is not only tuning frequency that is important, but how the port behaves at tuning frequency.

Anyway. Using a Beyma SM212 the results are much better, group delay can be lowered to a very nice value. 400hz and maybe even up to 700hz should be just fine, if you can place some damping material on the right locations.
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Old 19th September 2018, 11:17 AM   #16
Think is offline Think  Netherlands
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IMO it is better to use a closed sub @home as the room gain will amplify the lowest freqencies the most. BR, horns, TL and bandpass boxes have a steeper rolloff at the bottom, which makes them prone to booming.
Put the closed sub in a corner and if it is boomy, move it along a wall untill the sound is ok.

In general they are way more monkey proof.

Last edited by Think; 19th September 2018 at 11:38 AM. Reason: typo
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Old 19th September 2018, 11:51 AM   #17
KaffiMann is offline KaffiMann  Norway
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Think:
It's not a sub, but a 3 way speaker suited for stands or shelves, IE not floorstanding.
Previously I had the same misconception you seem to have, that ported enclosures are inherently boomy because they function on the principle of resonance in relation to volume. This is not right, every single type of design can be done "wrong", it does not have anything to do with the type of design, but the implementation.

I set out to "prove" that you can not get a ported enclosure to sound good. I proved myself wrong and am now a convert.
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Old 19th September 2018, 02:07 PM   #18
mbrennwa is offline mbrennwa  Switzerland
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I set out to "prove" that you can not get a ported enclosure to sound good. I proved myself wrong and am now a convert.
What's the trick to make bass reflex sound good, not boomy? Some say that comensation of the upper impedance peak using an LCR circuit does the trick, but maybe there's more to it.
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Old 19th September 2018, 02:10 PM   #19
mbrennwa is offline mbrennwa  Switzerland
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Originally Posted by KaffiMann View Post
mbrennwa:
The port I used for simulation is over 36cm long, not 10cm. And it's 33,1cm wide (divider in the middle for bracing) * 4cm tall, so 132,4cm2. It is not only tuning frequency that is important, but how the port behaves at tuning frequency.
Oh man... thanks for pointing out this stupid mistake. I guess there was a reason for my earlier comment that I am not very good with those simulation tools. I will try again this evening.
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Old 19th September 2018, 02:12 PM   #20
KaffiMann is offline KaffiMann  Norway
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Hahah! No worries, I had a *facepalm* moment myself when I noticed I had put the wrong parameter in hornresp. :-D

Can we call it even?

Regarding port loading:
Yes, there's more to it. Important to keep group delay as low as possible (completely ignored in commercial designs), often a port will cause lots of phase wrap at resonance, have to be mindful of that in the design.
Also think about the distances between the driver membrane and the internal sides of the enclosure and what frequency modes can be excited, it is easier to use dampening material to reduce high frequencies than low frequencies, just like with filters.
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