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Double check: Bass Reflex hole for 10L 80-3000hz top -> just 1,2cm length? Position?
Double check: Bass Reflex hole for 10L 80-3000hz top -> just 1,2cm length? Position?
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Old 16th April 2019, 11:17 PM   #11
Ron E is offline Ron E  United States
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Quote:
Originally Posted by HimG View Post
why you would not count an the 1,7 correction value? You suggest it'll be more?
With an oppening of 50cm^2 i would get around 5cm port length in bbox, so that would clear my confusion. ..but why is bbox suggesting 19^2 than ?¿? Programm fault?

Is the "port has to be 1/3 to 1/4 size of sd" rule
I would not count on an end correction of more than 0.8. Measure Fb and cut it off if too long. Bass box is not always correct.

The rule is to keep port velocity less than 17 m/s. This other rule is maybe a simplification of that. I mostly hear it in car audio circles
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Old 17th April 2019, 12:41 PM   #12
TBTL is offline TBTL  Germany
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You could add a level dependent bass boost to reach down to 80 Hz at low sound pressure levels, which is reduced when the speaker is asked to play at high levels. This way you get both some bass and a high SPL, though not at the same time.


To give you an idea, an Anchor Explorer 6000 battery powered 6.5" PA speaker has about 12 dB of boost. Port area is 12 cm^2 (2 ports of 28 mm diameter, 28 mm length) and amplifier power output is 60 W.

Last edited by TBTL; 17th April 2019 at 12:53 PM.
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Old 18th April 2019, 01:31 AM   #13
ICG is offline ICG  Germany
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Location: I had a Déjà Moo - I've seen that BS before!
Quote:
Originally Posted by Ron E View Post
I input parameters as given by the original poster. They are reasonably consistent. I don't have time to research a driver that someone did not identify.
The brand, power, size and other details were given. It took less time to search for it than to enter the parameters into the simulation. But more importantly, the parameters are NOT consistantly. If you compare them with actual drivers, the VAS and Sd and spl are not in any way explainable. The search for the drivers put out a 6" driver to be closest of every parameter and the parameters posted appear to be manufacturers specs vs. self measured, which usually leads to different parameters because of the measuring circumstances and -erros on it but being conclusive anyway. That's why I asked several times if it's that driver. An 8" driver with 94dB/1W/1m and a Vas of 4,8l is not conclusive for a 7/8" driver that got a Xmax of 3 or 4,3mm, that's the data of a pure midrange driver of maybe 1 to 2mm Xmax and a massive motor which isn't capable of anything in the bass. I've searched and the 6" is the single driver which is even close to the posted parameters. If you'd rely on the posted parameters, it looks more like an atificial combination of parameters and the lack of actual information (driver type+model), size, circumstances and nothing actually being found on a search for these hints just towards a trollpost.

Quote:
Originally Posted by Ron E View Post
Efficiency is not tied to driver size alone..and strongly tied to Fs.
eta=9.6e-10*fs^3*Vas/Qes =9.6e-10*109.4^3*4.8/0.62=0.009745 SPL(2.83)=112.1+10*log10(0.009745)+10*log10(8/3)=96.24
That applies to well above the fs. Here it is explained clearly in easy to understand terms:

pressure - Why do lower frequency need more cone excursion? - Physics Stack Exchange

In the bass it's only Vd, the peak displacement volume which is Vd = Sd x Xmax (or cone surface x excursion). Or in other words, it is exactly only dependent on the excursion and the membrane size in the bass. And that's what's in question here since you can't use any of the spl advantage above it.

Quote:
Originally Posted by Ron E View Post
See above.
Indeed, see above.

Quote:
Originally Posted by Ron E View Post
wrong - the sim calculates excursion limited SPL. The SPL produced by the max input power chart. I mentioned using a highpass in my first post as I recall
You also wrote that it needs 50W/8 Ohm despite the simulation stating 135W and most amps being incapable of delivering the needed current at the 3 Ohm of the driver, as I recall.
I also mentioned that the assumpted data you've based the simulation on are wrong and that the driver isn't capable of the power the simulation is based upon.

Quote:
Originally Posted by Ron E View Post
My (linear ) sim predicts what is in the vent sizer, roughly 113dB In free air, there will be spreading loss of ~6dB
Your simulation is based of inconsistent parameters and the assumption that a driver being capable of 94dB in the mid-range got the same spl in the bass despite having way too less membrane surface for both specs at the same time. If it would exist, it wouldn't be available at the price of a PRV driver.

Quote:
Originally Posted by Ron E View Post
To get the right numbers in baudlines calculator you need to enter 14/2.54/0.83 as driver diameter.
While that is true, none of the 7/8" drivers got of PRV Audio would match the parmeters posted in any way and just the 6" even come even close to it. To get 125dB at 80Hz out of a 6" or even a 8" driver is physically impossible at 3 or even 4,3 mm excursion and 125W rms. Please show me any 6" or 8" speaker which is capabel of 125dB/1m at 125W at 80Hz in a 10l enclosure at the price of a PRV driver.

125dB/1m? Yes, possible. 80Hz possible? Yes. 125dB/1m at the same time at 80Hz with 125W? No, that's definitely not possible. You'll find even 115dB are really hard to achieve. You'll find that 115 dB SPL max at ~250W at 8" is the most you're likely find and that these use around 30l. In 10l? Uhm, well, show me?
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Last edited by ICG; 18th April 2019 at 01:33 AM.
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Old 23rd April 2019, 08:02 AM   #14
HimG is offline HimG
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Quote:
Originally Posted by TBTL View Post
You could add a level dependent bass boost to reach down to 80 Hz at low sound pressure levels, which is reduced when the speaker is asked to play at high levels. This way you get both some bass and a high SPL, though not at the same time.


To give you an idea, an Anchor Explorer 6000 battery powered 6.5" PA speaker has about 12 dB of boost. Port area is 12 cm^2 (2 ports of 28 mm diameter, 28 mm length) and amplifier power output is 60 W.
Yeah, thats what i‘m ending up with i guess. Looking for the dimensions of other 6,5“ boxes is a good tip, i guess i‘m staying with the ~19cm^2 bbox suggests if these commercial 6,5“ boxes also just got 12^2 cm reflex diameter. I would maybe start without any port lengh and would test it through screwing aome wood from the back on the port in maybe 1cm steps making it longer and longer and compare if it gets better or worse. I guess i will stick to the 2cm slice over the 17cm at toe bottom instead of the 5x5 square next to the tweeter, or does someone would chose this option over the bottom slice for a top like these? For me without experience the bottom slice option seams to be the one where less things could go wrong because its centered and widely spread.
Gonne create some saw dust tomorrow i guess.
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