My ported subwoofer

[t.antony]

Started work on damping the sub. I am planning to use fiberglass cross members 6mm thick, 1 inch wide and placed about 4 inches apart on all the 5 inner surfaces. The shallow cavities made by these will be filled with fiberglass putty increasing the effective thickness of walls to 1 inch.

Here is a pic of the cross members being made from multiple layers of fiberglass mat

 

[captrajesh]

Started work on damping the sub. I am planning to use fiberglass cross members 6mm thick, 1 inch wide and placed about 4 inches apart on all the 5 inner surfaces. The shallow cavities made by these will be filled with fiberglass putty increasing the effective thickness of walls to 1 inch.

Do you think these would give the sub the rigidity it requires? IMO, MDF bracing would be a better option.

 

[t.antony]

Do you think these would give the sub the rigidity it requires? IMO, MDF bracing would be a better option.

Fiberglass is many times stiffer than MDF so it will aid in pushing the panel resonances high (much above the crossover frequency). Also it makes the joints between panels very rigid thus helping in reducing panel deflections.

I am not in favor of MDF cross braces since it would require many braces to effectively lift the panel resonances, these braces will also reduce the volume significantly and I have not accounted for that in my design.

Fiberglass sandwitch worked well for me in my MTM project. I am experimenting to see if I could get acceptable results with a rigid internal cavity.

 

[vasishta.sushant]

You guys talk greek. Would someone care to explain ? That thing sure looks good but I realize that a lot goes behind the scene as well.

 

[captrajesh]

You guys talk greek. Would someone care to explain ? That thing sure looks good but I realize that a lot goes behind the scene as well.

Hi Vasishta.sushant,

Not sure whose posts you find as Greek but as your post is coming right after my exchange with T.Anthony, I'm assuming it could be those that you are referring to. It would be better if you could point out so that the posts can be elaborated.

 

[sonicbliss]

Can you explain the rationale behind this suggestion. Why should I eq the sub and how will it help in better integration with my MTM's?

The measured steady state in room response at the listening position is very ragged. Earl's method helps in to even out the response. Here is the documented proecedure for a single sub Bass Integration Guide Part 1 | Hifi Zine

It might help if you could explain a bit about your current setup. What do you use as your mains and have you tried out any of the setups that Geddes recommends?

I dont have a system yet, but I am starting a build soon based on multiple bandpass subs using Earl Geddes method. Its too early to talk about the mains but they will definetly be running fullrange as recommended by Earl's method.

In order to not hijack this thread, the Earl Geddes method has been moved to this new thread http://www.hifivision.com/diy/20482-sub-setups-using-dr-earl-geddes-method.html#post282925

Sonicbliss

 

[t.antony]

The measured steady state in room response at the listening position is very ragged. Earl's method helps in to even out the response. Here is the documented proecedure for a single sub Bass Integration Guide Part 1 | Hifi Zine




I dont have a system yet, but I am starting a build soon based on multiple bandpass subs using Earl Geddes method. Its too early to talk about the mains but they will definetly be running fullrange as recommended by Earl's method.

In order to not hijack this thread, the Earl Geddes method has been moved to this new thread http://www.hifivision.com/diy/20482-sub-setups-using-dr-earl-geddes-method.html#post282925

Sonicbliss

You seems to have done good research on Geddes, keep us updated about your project as it evolves, some WIP pictures would be good.

 

[t.antony]

Internal damping with fiberglass putty is complete, The cab must be weighing close to 20kg now.

 

[Kittu]

Update please.

 

[Decadent_Spectre]

Where did you get the one end flared PVC pipe?

 

[t.antony]

Kittu,
The state of the sub is more or less the same - being a bit lazy about the fiberglass finishing . I am exploring other finishing options this time.

Decadent_Spectre,
It's a regular PVC pipe. The flare is made by heating one end and then pressing against a spherical object.

 

[Jaybe]

Antony,

Do you think this Driver can lend itself to Biamped Sub Woofer ? In such a case what will be the implications on the enclosure ?

Jayant

 

[t.antony]

Antony,

Do you think this Driver can lend itself to Biamped Sub Woofer ? In such a case what will be the implications on the enclosure ?

Jayant

Do you mean using a sub per channel? There are no implications on the enclosure dimensions, but depending on the acoustic cutoff of your main speakers, you need to adjust the xover frequency and level.

If your mains is a ported design, F3 is a good starting point.

 

[t.antony]

It seems like I have to start afresh on the cabinet again... :sad:

The sub enclosure got damaged in a minor fire incident at my friend's fiberglass workshop. Luckily nobody got hurt or no major damages to property.

 

[t.antony]

Here is the construction plan for this sub. This plan was hidden in another thread so posting here as well for better visibility.

Front panel is made of two sandwiched sheets

For the port, use a pvc pipe with inner diameter close to 9cm (3.5 inches). Length of the port is 12 inches.

There are no cross braces hence damping of all the panels is mandatory. Use bitumen roofing sheets up to 5mm thick on all the internal surfaces.

Other possible options for damping the panels are
1) Ceramic tiles
2) Bitumenized felt

Stuffing of the internal cavity with Dacron/glass-wool is not required

More details on driver and amplifier procurement are available on this thead - http://www.hifivision.com/diy/22681...s-driver-available-locally-12.html#post348811

 

[anilva]

It seems like I have to start afresh on the cabinet again... :sad:

The sub enclosure got damaged in a minor fire incident at my friend's fiberglass workshop. Luckily nobody got hurt or no major damages to property.

Antony,

This is not good news. Fire accidents are always dangerous. I am not sure whether fibre glass is inert to fire...anyway good that nothing untoward has happened. This gives you an opportunity to build a better cabinet I guess. There is always a silver lining.

Cheers.

 

[t.antony]

I am not sure whether fibre glass is inert to fire...

I haven't seen a finished fiber glass sheet catching fire, on prolonged exposure to fire, the resin in the sheet will char away emitting (toxic?) fumes leaving aside the glass fibers. In this case some wood shavings in the workshop caught fire and the it quickly spread across the room.

This gives you an opportunity to build a better cabinet I guess. There is always a silver lining.
Cheers.

I am not planning to build the same enclosure again, considering more efficient designs like tapped horn for this driver. Initial simulations with hornresp looks promising.

 

[spirovious]

Any update with this project?

 

[t.antony]

Here are some interesting sims on hornresp for this driver. With corner loading predicted spl is well over 100db!

The 19Hz tapped horn is 5 meters long and predicted spl is +100dB up to 60Hz
28Hz one is 3.5 meters long and predicted SPL is at 105dB! and it looks like it can be crossed over 100Hz.

 

[gp_freak]

Hi Antony, i am very much interested in building a DIY sub. Infact i used your thread as the reference thread before i took the jump.

With a 70 litre box and tuned to 25 Hz, F3 is 44.06 HZ. Also i have taken the Xmax of this Sub to be 7 mm. Approximately at 125 watts, the SUB reached 7mm linear excursion.

Also the SPL level below 50 HZ rolls of at a very steep rate. Now my question is, why not use a JBL sub at 3.5 K or Infinity reference sub which is availbale at 4.5 k. The only downside i see in using these cars subs is that it requires minimum twice the amount of amplification power of the Peerless sub.

I understand that similations are only for reference and I am a NOOB in Audio and this is my very first post here. Please pardon my ignorance