Need help building a subwoofer box.

[JohnnieB]

Here is a video of a couple 4" sub's they claim goes down to 25hz. I don't know the specifics of the build nor will I try and formulate a guess. I'm not offering an argument for or against either TLS or Gary. Its simply a video that came to mind when I saw this thread.

 

[Gary147852]

I don't know about that vid. The port looks bigger than the drivers. I'm sure with these drivers port velocity will be very low. And from looking at the enclosure it was definitely Intended for 2 much larger drivers.

 

[TLS Guy]

Here is a video of a couple 4" sub's they claim goes down to 25hz. I don't know the specifics of the build nor will I try and formulate a guess. I'm not offering an argument for or against either TLS or Gary. Its simply a video that came to mind when I saw this thread.

I have analyzed that video. This is total BS.

These are the drivers used.


The Fs is 65 Hz, and Qts is 0.66. So we have a high Q driver driven below Fs. So what you are largely hearing is resonance and flutter. Yes flutter on your bottom. You can hear the sound of the driver being driven way beyond its mechanical limits.

There is frequency doubling, quadrupling and eightupling!

The harmonic products at 100, 150 and 200 Hz are 24 db above 25 Hz.

So that is a completely bogus post, and practically useless.

 

[rojo]

OP, if you really want a small bass module, get this 6.5" Tang Band and put it in an 8" x 8" x 12" box (internal dimensions). Add a 1.5" dia x 7 3/4" long tube, and you'll end up with a tiny, well-controlled unit with an F3 around 34Hz.

Or, since they're cheap and most 4-ohm stable mono or bridgeable amps would be overkill, a dual driver option might make more sense. Two of those drivers opposed in a 10"x12"x12" enclosure with a 1.5" dia x 3 1/3" length port would have a similar F3 without much increase in size, but you could wire it in series for an 8 ohm load. (Just bear in mind that the wattage gets divided between the drivers in series, so a 100 watt amp becomes a 50 watt amp.)

Or a pair of these 4.5" drivers in a box with internal dimensions of 6.5"x6.5"x10" and add two 0.75" dia x 7 1/3" length ports, and you'll actually have response pretty close to the single 6.5" driver option I suggested first -- just with a few dB less output. Unfortunately, this config will probably put you over the $200 mark once you buy an amp and all the cabinet components.

In any case, there's one thing all those drivers offer that your current one doesn't, which is a set of published Thiele-Small parameters.

 

[markw]

Yes flutter on your bottom.

I've always enjoyed this.

...wait, what? We're talking about speakers here?

 

[TLS Guy]

I've always enjoyed this.

...wait, what? We're talking about speakers here?

 

[TheWarrior]

This subject isn't actually open for debate, there's a pretty solid foundation for science in this hobby. Me thinks AB and Gary would greatly benefit from expanding their horizons and purchasing the Loudspeaker Design Cookbook or one of several other great options out there.

 

[Gary147852]

This subject isn't actually open for debate, there's a pretty solid foundation for science in this hobby. Me thinks AB and Gary would greatly benefit from expanding their horizons and purchasing the Loudspeaker Design Cookbook or one of several other great options out there.

I've read loudspeaker design 201. The only thing about having a scientific foundation is that you need data (ts) with out that you just have to rely on more primitive methods. Now I absolutely think he should buy another driver and build an enclosure based around that. But that's not what he asked. He is simply trying to breathe new life into old gear (which I can totally relate to). Another point is that he should practice his enclosure making skills, preferably by making a box for his current driver if it's not perfect then oh well, it's not like he dropped a fortune on it. But he will have gained some much needed experience so that when he decides to get a new driver that he can properly design a box for it will come more easily for him.

 

[markw]

I've read loudspeaker design 201. The only thing about having a scientific foundation is that you need data (ts) with out that you just have to rely on more primitive methods. Now I absolutely think he should buy another driver and build an enclosure based around that. But that's not what he asked. He is simply trying to breathe new life into old gear (which I can totally relate to). Another point is that he should practice his enclosure making skills, preferably by making a box for his current driver if it's not perfect then oh well, it's not like he dropped a fortune on it. But he will have gained some much needed experience so that when he decides to get a new driver that he can properly design a box for it will come more easily for him.

Well, he asked a technical question and got the best answer possible: the truth.

If you can provide a better answer as to he can achieve his design goals, then feel free to weigh in. Simply building a better box that will never satisfy his desire is an exercise in futility.

Now, if he wants experience in woodworking skills was his primary goal, then I would agree with you.