WinISD pro to simulate 6th order bandpass subwoofer

[christophorus]

Hi guys,
I just played around with WinISD pro to simulate 6th order bandpass subwoofer for in car use. Please have a look for driver spec, box volume and result graphs below.
I put system input power =40w and series resistance= 1 ohm.
I add lowpass (butterworth, n=2, fc=120Hz).
The SPL graph looks so good, but I rather worried with group delay (27,595ms at 23,31Hz).
Do you see any flaws with this sim result? can I get a better sim result than this?

I'm waiting for your comment before I start wood working.

Thankyou in advance for your help.

Chris.

[Cro maniac]

The car will boost your subwoofer's frequency response, and you will get a big hump in the 35-45 Hz region. Ok if you listen mostly to hip-hop.
Otherwise, I would suggest an earlier and no so steep rolloff of the box response to get flatter in-car response.

[Volenti]

I agree, adjust the enclosure so instead of the bandpass having a flat top shape it slopes up with increasing frequency, the attachment shows this more clearly, red is the bandpass curve while green is sealed.

The rising response blends in with the cabin better and the high tuning of the second chamber (70hz-80hz is common) reduces group delay and increases efficiency.

I've used this style of response curve for almost every BP enclosure ever since I discovered it.

[christophorus]

Hi Cro Maniac and Volenti,
thank's for your quick response.
I followed your suggestion and did a sim as you can see below.
rear chamber tuned to 16Hz.
front chamber not change = 63Hz.

green line = original sim.
yellow line= improved sim.

SPL (40w input power) @30Hz decrease -3dB from the original sim, is it enough to flatten in car SPL response?
Group delay also looks better (22ms @20Hz) it's OK or not?

But I rather confuse with Maximum SPL graph, it shows that max SPL at 63Hz (101dB), does it mean I will get big thumb at 63Hz and hear very weak sound below and above this peak?

Does SPL graph show real behaviour of the sub (minus room gain)?

thank's
Chris.

[christophorus]

Hi,
I did another sim, instead of lowering rear chamber tuning freq, I raised up front chamber tuning freq to 75Hz ( see graph below - blue line), I get 2 dB more SPL average, which is better for SQ, this one or the one above?

thank's
Chris.

[Cro maniac]

The last curve is about as good as it can get with that box. The curve should be more steeper to match car cabin gain properly, but now you wont have such a huge peak.
I see a problem in tryng to fit such a long port in 45liter rear chamber.

But I rather confuse with Maximum SPL graph, it shows that max SPL at 63Hz (101dB), does it mean I will get big thumb at 63Hz and hear very weak sound below and above this peak?

You should not worry about that. That graph only shows that if you intend tu play frequencies (not music) through this sub (SPL competition), you should get maximum result at 63Hz because port tuning reduces cone excursion at that frequency. It tells you nothing about how your sub will play in real life.

Have you consider other types of boxes considering you are leaning towards SQ setup ?

[christophorus]

Thank's cro maniac,
I will use 2 - 5cm dia. rear port with length=51,2cm, since my box dimension = 60x30x30cm (50x30x30 rear chamber and 10x30x30 front chamber) it will fit inside the box.
What do you suggest for better SQ with this driver? The constrain is box dimension.

Thank's.
Chris.

[Cro maniac]

What do you suggest for better SQ with this driver? The constrain is box dimension.

Ultimate for SQ in car is closed box with Q in range 0,6-0,8. (5-10 liter box) But since you have a 10" driver you might find that the closed box gives you less SPL than wanted. So, vented box of about 15liters tuned to 25Hz should give you pretty flat non boomy in-car response with maximum SPL capability half way between closed and bandpass box. It still leaves you with fitting a long port in small box problem thou.

[christophorus]

Hi cro maniac,
are you sure vented box only needs 15liters? it's so small (30x30x16,67cm)!
and the port is very long (262cm)! and the SPL graph (see below - yellow line) has very steep curve with peak at 80hz, doesn't it become one note sub which is common in bandpass box design?
I made another vented box sim, the box dimension is exactly the same with my bandpass sim (54liters), tuning freq.=18Hz. SPL graph is the red line on the graph below, group delay and rear port velocity is slighly better than bandpass, what do you think? is it still become a boom box?
which one of the 3 modeled sim here is the best for SQ?

thank's
Chris.

[noodle_snacks]

A series resistance of 1 ohm is far too high unless you are planning to passively cross over the driver with an inductor or similar, otherwise series resistance should be very small.