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Subwoofer for small space?

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sMASH
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Re: Subwoofer for small space?

Postby sMASH » November 8th, 2020, 7:57 am

Brian Steele wrote:
nervewrecker wrote:passive radiator?


Nope. A passively-assisted sealed alignment is basically a sealed design with a large capacitor in series with the woofer. Choose the value of the capacitor right, and you can end up with a nice boost at low frequencies. It can also help to reduce the "boom" of a high-Q box (which is what can happen if you shoe-horn a driver into a small box). The disadvantage is a bit of loss in efficiency (not peak SPL output - that's set by Xmax), but power is cheap these days.

You can read more about the technique at the link below, where I provided a worked example (and I might actually end up building that example for a project that I'm considering at the moment).

https://www.diyaudio.com/forums/subwoof ... ments.html
I was reading up on motors, and this sounds similar to how they need a capacitor to get them to Start. It charges and discharges with the coil in the magnetic field, but with a delay, in the pattern of a hysteria loop.
So I gather that it causes some kinda electricsl resonance in the circuit. So u can tune to get a frequency being targeted with fall off on either side, like a typical q curve.

So it should be like a equalizer adjustment, where u can decide the frequency.

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Re: Subwoofer for small space?

Postby kavaninho » November 8th, 2020, 8:05 pm

OffshoreMarketing wrote:
kavaninho wrote:
OffshoreMarketing wrote:Passive radiators around forever have them on my Polk audio systems from the 80s


check out the soundfire Sm-8 sub available at jdm master it’s a shallow mount 8” 300 rms nice output and response


Anybody in here uses soundfire, I'll like to know where they stand? Never heard a soundfire sub myself but this seems to be some mass alibaba buy that was brought in locally.


I Use them all the time seeing that i am the dealer “mass alibaba buy “ seems to be the talk going around.
I will say this much they are built by the same factories that build for plenty of the “best” brands ppl praise here.


I'm well aware of what is the trend.
I can call about at least 5 brands (but choose not to list here) that people glorify locally that are direct purchases from those Chinese build houses. Consumers must keep in mind they are purchasing a product that has little to no technical support from the vendor. That being said, some of the products are capable of actually doing well. I'm not bashing the Chinese manufacturing here as they just provide a solution based on their customer request.

Seeing "Engineered in the USA, Made in China" on a packaging would seem to be a lie as well.

I have no problem if someone decides to take up a business venture and distribute their "own" equipment brand. However, if the intent is to ship the cheapest thing available in the name of "my speaker is $100 less boidanboi", this will cripple the industry as the stuff will only get more inferior. Mind you, this would be the same industry that was once the said business owner's hobby.

I hope Local car audio don't get into that downward spiral. But I'm beginning to think its too late.

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Re: Subwoofer for small space?

Postby OffshoreMarketing » November 9th, 2020, 8:42 am

kavaninho wrote:
OffshoreMarketing wrote:
kavaninho wrote:
OffshoreMarketing wrote:Passive radiators around forever have them on my Polk audio systems from the 80s


check out the soundfire Sm-8 sub available at jdm master it’s a shallow mount 8” 300 rms nice output and response


Anybody in here uses soundfire, I'll like to know where they stand? Never heard a soundfire sub myself but this seems to be some mass alibaba buy that was brought in locally.


I Use them all the time seeing that i am the dealer “mass alibaba buy “ seems to be the talk going around.
I will say this much they are built by the same factories that build for plenty of the “best” brands ppl praise here.


I'm well aware of what is the trend.
I can call about at least 5 brands (but choose not to list here) that people glorify locally that are direct purchases from those Chinese build houses. Consumers must keep in mind they are purchasing a product that has little to no technical support from the vendor. That being said, some of the products are capable of actually doing well. I'm not bashing the Chinese manufacturing here as they just provide a solution based on their customer request.

Seeing "Engineered in the USA, Made in China" on a packaging would seem to be a lie as well.

I have no problem if someone decides to take up a business venture and distribute their "own" equipment brand. However, if the intent is to ship the cheapest thing available in the name of "my speaker is $100 less boidanboi", this will cripple the industry as the stuff will only get more inferior. Mind you, this would be the same industry that was once the said business owner's hobby.

I hope Local car audio don't get into that downward spiral. But I'm beginning to think its too late.


Ammm so where u want the subwoofers to be made USA? None of the local brands I am aware of are producing inferior goods and I have yet to here a person complain about price vs performance yet. SoundFire has no buisness in competing with price btw but it’s fair.

China probably produces 90% of car subwoofers and the ones that are assembled in the USA are just that made in China but it together in USA

Engineered in USA and made in China is not a lie I can tell u for a fact some maybe not all actually do r&d before producing a final product.

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Re: Subwoofer for small space?

Postby kavaninho » November 9th, 2020, 9:09 am

That's great to know the intent is not a "price battle". As I said, I have no issue with the chinese manufacturing.

Will surely try the soundfire whenever opportunity arises.

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Re: Subwoofer for small space?

Postby Brian Steele » November 9th, 2020, 10:09 am

Building them in China isn't an issue.

Quality control is the issue. Like when someone orders a subwoofer driver of specs A, the manufacturer sends a sample that matches the specs, and then when the buyer orders in quantity, what is received are subwoofer drivers that look like the sample but are entirely off-spec.

To avoid this, the buyer should test random samples of the received drivers to see if they're within spec (short break in period and then measured by DATS or a similar tool), and the contract should be written to ensure a refund (or no payment) for any received drivers that are out of spec.

Drivers from the following sources always seem to be close to or meet published specs in my experience:

Infinity
JBL
Eminence (or any company with Eminence as the OEM for their drivers)
Alpine (except for one instance re rated power handling)
Parts Express (with a few exceptions)

It would be very nice if every driver came with a "birth sheet", similar to what's provided with many car audio amplifiers :).

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Re: Subwoofer for small space?

Postby OffshoreMarketing » November 9th, 2020, 1:26 pm

Brian Steele wrote:Building them in China isn't an issue.

Quality control is the issue. Like when someone orders a subwoofer driver of specs A, the manufacturer sends a sample that matches the specs, and then when the buyer orders in quantity, what is received are subwoofer drivers that look like the sample but are entirely off-spec.

To avoid this, the buyer should test random samples of the received drivers to see if they're within spec (short break in period and then measured by DATS or a similar tool), and the contract should be written to ensure a refund (or no payment) for any received drivers that are out of spec.

Drivers from the following sources always seem to be close to or meet published specs in my experience:

Infinity
JBL
Eminence (or any company with Eminence as the OEM for their drivers)
Alpine (except for one instance re rated power handling)
Parts Express (with a few exceptions)

It would be very nice if every driver came with a "birth sheet", similar to what's provided with many car audio amplifiers :).


I agree there is another local brand that does not even come with a spec sheet with their products which makes no sense to me. Problem with every driver being independently tested is hard thing to get done tbh esp in China. That being said the more professional factories tolerances and quality control are much better so specs should not differ as much

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Re: Subwoofer for small space?

Postby Strugglerzinc » November 10th, 2020, 9:40 pm

This is a request for clarification from those of you who understand these things more than i do.

I have modeled 2 subs in WinISD in a 1cuft ported box for 36Hz

JL 12TW3-D4 and Pioneer TS-SW3002S4

The SPL curves are as follows, JL red and Pioneer green with a less than 1dB difference at 40Hz.

Capture.JPG


To my eyes, they seem very similar and not what i expected based on price and brands. Are there other curves i should be looking at (although all seem similarly close) or other parameters i should be varying? Or is it that these two are so similar?

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Re: Subwoofer for small space?

Postby kavaninho » November 10th, 2020, 10:24 pm

^I'm not sure if you inputted the TS correct there. I had the 12TW3 in my WinISD database and the plot is no where as misaligned in your screen shot. Verify the TS against the manual.

Sure there are other plots to looks at, however, try to flatten those responses first.

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Re: Subwoofer for small space?

Postby Brian Steele » November 11th, 2020, 8:59 am

Oh boy, where to start.

1. Efficiency at low frequencies is largely a function of box size and tuning

2. WinISD is an inaccurate modeler for car audio designs. It does not take "cabin gain" into effect. Nor does it accurately model the effect of Le, or the effect of "semi-inductance".

3. The mantra for car audio subwoofer design is - design for power-handling, fix FR with EQ.

4. To design for power handling, make sure that driver does not exceed Xmax in the passband (that region above Fb, the resonance frequency) for up to at least 1/2 of its rated power. In other words, if given a driver with 200W power handling and 12mm Xmax, when trying to come up with a good box design for it, make sure that box design does not have it exceeding 12mm Xmax when fed with 100W. If you're planning to feed the driver with more than its rated power handling, use that input power instead (e.g. planning to use a 500W amp, make sure Xmax is not exceeded @250W).

5. A 36 Hz Fb is a bit high for a 12" subwoofer design for car audio use, unless you're designing for SPL. Try 30~32 Hz, or even sealed (but see note #4 above).

6. Make sure that you have good EQ :) (see point 3).

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Re: Subwoofer for small space?

Postby kavaninho » November 11th, 2020, 12:29 pm

I did not even know people use point 3 above as an approach. I guess if you have capable DSP you can. IMO usually the more EQ and "DSP capability" you require after your system was built indicates poor decisions in the earlier stages whether it be driver selection or system design.

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Re: Subwoofer for small space?

Postby Strugglerzinc » November 11th, 2020, 5:37 pm

kavaninho wrote:^I'm not sure if you inputted the TS correct there. I had the 12TW3 in my WinISD database and the plot is no where as misaligned in your screen shot. Verify the TS against the manual.

Sure there are other plots to looks at, however, try to flatten those responses first.


All parameters are verified from the manuals for both.

I'm not concerned with anything except the similarity between the two as my brain says they shouldn't be so close.

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Re: Subwoofer for small space?

Postby Brian Steele » November 11th, 2020, 9:07 pm

kavaninho wrote:I did not even know people use point 3 above as an approach. I guess if you have capable DSP you can. IMO usually the more EQ and "DSP capability" you require after your system was built indicates poor decisions in the earlier stages whether it be driver selection or system design.


That advice was shared with me years ago by someone who used to work for Infinity audio, and what he said makes sense. Even now, most people use box design programs that don't take all the necessary details into consideration (one of the biggest being the transfer function of the car's cabin), so it's best just to design for power handling and fix the response with EQ.

This is a worked example - this is a dual-driver offset transmission line design using 6.5" drivers that was considering for my daughter's car. The grey line is the 2PI predicted response of the build. The red line is the predicted response at the driver's position when the car's transfer function is taken into consideration. Not the flattest, is it? I might build that and fix the response with EQ - or just go for a sealed 10" design instead.

2020-11-11.png

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Re: Subwoofer for small space?

Postby Ted_v2 » November 14th, 2020, 9:39 pm

i own the sub that nerve show in the video, the sub is rated 350rms. i have 500 going to it, sounds amazing for inside the vehicle. its just right for a daily. in a ideal world i would of liked it to be ported for a little more output on the lower ranges, but overall its really great. i have a 2 way active setup with it, soon to be 3 way

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