DIY sub

[annunaki]

Properly done slot vents with rounded edges internally and externally perform as wel as the round tubes. The small difference is inaudible. Not to mention, the added bracing benefits the slot vent provides to the enclosure as well. The bracing must be laid out to accomodate the large area the ports take up. With a slot vent it is easier to accomodate bracing.

With the vent mach so low, there will be no issues with vent noise in either case. that being said I feel the slot vent is the better route to go.

 

[treejohnny]

I am very interested in making my own sub. The kappa sub is looking pretty inviting since the volume and such has already been laid out. I have a bunch of 3/4 oak verneer plywood laying around and was wondering if this is taboo? Would it be better to use plate amp or the berringer rack mount amp ? How would one go about making an oval port with flared ends ?

 

[TLS Guy]

I am very interested in making my own sub. The kappa sub is looking pretty inviting since the volume and such has already been laid out. I have a bunch of 3/4 oak verneer plywood laying around and was wondering if this is taboo? Would it be better to use plate amp or the berringer rack mount amp ? How would one go about making an oval port with flared ends ?

You can certainly use your veneer plywood. It is slightly second best to MDF board. I would use a plate amp if you plan to put the amp in the speaker.

If you want a flared port you will need to use the proprietary flared ends. I would not try and make an oval flared port.

Annunaki and I have a disagreement over vent velocity. There is honest debate about whether the vent speed should be limited to 25% or 12.5% of the speed of sound. He obviously favors 12.5%. I think I'm in the majority, but I can't be certain of that.

I would say this, that those velocities will be at high power. Now I'm not a head banger, and at least on my spectral frequency meter in WaveLab, there is seldom high energy below 100 Hz. The issue is the LFE channel on movies. For effect this channel is boosted 20 db for explosions. This can take a lot of power. However I doubt most of us listen to continuous canon salvos and explosions. And for the explosions we do encounter, I doubt a vent speed of just under 30 m/sec will affect them adversely.

For truth in advertising, I have to declare I don't use these type of subs. I favor transmission line loading, so I don't have this issue to contend with directly. I certainly don't plan on giving my lines, and I think that goes for those few of us who favor and enjoy bass from that method of loading.

I do however have these speakers which I built for our lower level living room.

http://mdcarter.smugmug.com/gallery/2424105#127080849

The vent speed on the QB4 reflex speakers is 27 m/sec. I have had them on an oscillator, played large organs at substantial volume and played movie explosions. These speakers have a nice solid bass. I can not hear any vent chuff, huffing or puffing what ever. Certainly you can feel substantial airflow from the port, but I don't hear any additions to the performance from the port. Now this is not a sub, but the KEF B 139 is renowned for producing good powerful clean bass.

So to cut to the chase, would I personally go to the trouble of constructing a slot vent? No, but to each his own.

 

[jaxvon]

I am very interested in making my own sub. The kappa sub is looking pretty inviting since the volume and such has already been laid out. I have a bunch of 3/4 oak verneer plywood laying around and was wondering if this is taboo? Would it be better to use plate amp or the berringer rack mount amp ? How would one go about making an oval port with flared ends ?

Plywood is fine. Just be sure to brace the inside enough to raise the resonance above the passband.

 

[flippo]

Volume

What volume should the box be? winISD says abou 3.9 earlier in this thread 3.024 was stated. I'm going vented with 4 in flared tube.

 

[TLS Guy]

What volume should the box be? winISD says abou 3.9 earlier in this thread 3.024 was stated. I'm going vented with 4 in flared tube.

This is my best alignment.

Name: Kappa Perfect 12 VQ low inst
Type: Standard one-way driver
Company: Infinity Systems Inc.
No. of Drivers = 1
Fs = 22.9 Hz
Qms = 10.29
Vas = 96.43 liters
Cms = 0.323 mm/N
Mms = 176.4 g
Rms = 2.398 kg/s
Xmax = 16.75 mm
Xmech = 25.13 mm
P-Dia = 250 mm
Sd = 491 sq.cm
P-Vd = 0.822 liters
Qes = 0.36
Re = 4.42 ohms
Le = 1.14 mH
Z = 4 ohms
BL = 11.92 Tm
Pe = 400 watts
Qts = 0.34
no = 0.141 %
1-W SPL = 83.65 dB
2.83-V SPL = 89 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box
Shape: Prism, square (optimum)
Vb = 3.024 cu.ft
Fb = 21.38 Hz
QL = 6.563
F3 = 21.58 Hz
Fill = minimal
No. of Vents = 1
Vent shape = round
Vent ends = two flared
Dv = 4 in
Lv = 22.49 in

So the box volume is 3.024 cu.ft with the low insert.

Now the driver volume is 0.072 cu.ft. You will have to add that and the volume of the bracing and the plate amp to the total volume.

 

[flippo]

thanks

would you add or subtract the bracing,amp, and speaker from volume?

 

[TLS Guy]

would you add or subtract the bracing,amp, and speaker from volume?

As I stated in my post you add it. As Archimedes said, an object will displace a volume equal to its own volume. So that volume has to be added back.

 

[flippo]

ding ding the light goes on in my head! I think I wasn't fully awake yet this morning when I asked a stupid question. Thanks again.

 

[TLS Guy]

ding ding the light goes on in my head! I think I wasn't fully awake yet this morning when I asked a stupid question. Thanks again.

No problem.

 

[annunaki]

TLS Guy,

The reason I suggested a slot vent is that you can allow for larger port surface area while more easily "folding" a longer port inside the enclosure.

The advantages to a port with large amounts of surface area are more or less similar to why you prefer Transmission Lines. A port with a large amount of surface area adds additional radiating surface which yields more effortless, efficient output. They also help to rid of port compression issues. One of the reasons you claim the TL enclosures have such nice low frequency extension is directly due to this. Not to mention they are tuned fairly low as well.

As far as vent mach is concerned, the lower the better. However, as long as any port is below audible limits throughout the usable range it should be sufficient. It doesn't mean that it is the best option though.

 

[TLS Guy]

More of resonators and pipes

On thinking about your last post Annunaki, it occurred to me that there comes a point when a resonator with a long duct, which is after all a an open flue pipe, actually becomes a strange pipe in its totality.

These large ducts between five and six feet, will have a fundamental resonance in the 200 to 250 Hz range depending on length. If the crossover to the sub is second order, a not unlikely scenario, then the driver is only 12db down at the duct resonance. There will certainly be enough power to excite the fundamental of the duct and I would think the second harmonic of the duct would have significant output also. That would be between 400 and 550 Hz.

Do you use high order crossovers with your long slot vent subs?

It seems to me that with the work involved in all of the construction, it certainly begs the question as to whether the construction of TL subs should be encouraged a lot more. There seem to be a lot of advantages to going the TL route with these large displacement sub drivers. After Christmas I think I will work up TL alignments for the kappa perfect 10 and 12 and put them out there and see who wants to build one. I have a strong feeling that will be the best performer of all. As you say there certainly will be no issues of vent compression and the range over which the driver would be supported would be significantly greater.

I did a post yesterday that might interest you replying to someone who stated that pipe organs suffered from resonance! So I took the opportunity to link the speaker builder's art back to the ancient art of organ building.

http://forums.audioholics.com/forums/showthread.php?p=346494#post346494

Have a good Christmas!

 

[annunaki]

TLS Guy,

I never use anything lower than a 4th order slope for large slot, vented enclosures. Higher order crossovers tend to allow the sub to "disappear" better into the system and the room.

 

[pdxmonkeyboy]

Not to make this thread go backwards or anything but why did you choose the infinity driver over the dayton? or the rythmic 12" servo sub kit. I thought in an earlier thread you were thinking about the dayton HF driver?

 

[flippo]

driver

Yes I was and I am not totally settled on the driver (I am still in planning stages). The Infinity driver was recomended on this thread that has a lot more experience than myself so I would be a fool to not listen to their advice.

 

[flippo]

bracing

How do you dwtermine the amount of cubic footage that bracing takes since the size and shape can be irregular? Does bassbox lite design software help with this?

 

[TLS Guy]

How do you dwtermine the amount of cubic footage that bracing takes since the size and shape can be irregular? Does bassbox lite design software help with this?

No, it does not. You just have to make a good estimate. It is a pretty simple matter to the calculations. Just round the numbers off.

 

[flippo]

software

just trying to decide if the software is worth it.

 

[flippo]

Sorry to be a pain but another ?

In my planning stages still, how does the JL Audio 12w3v3 4ohm and the 12w1v2 4 ohm speakers match up with the Infinity kappa perfect 12 VQ?

 

[WmAx]

In my planning stages still, how does the JL Audio 12w3v3 4ohm and the 12w1v2 4 ohm speakers match up with the Infinity kappa perfect 12 VQ?

They certainly can not match the optimal response of the Kappa Perfect 12VQ, due to the VQ's easily changed QTS parameters with the VQ function. It is highly doubtful that the w3 matches the linearity of the Kappa Perfect(the Kappa Perfect drivers exceed the linearity of the servo controlled DD drivers used in Velodyne's high end DD series, as verified by credible 3rd party measurements), and even if it managed to, it would not be as versatile in application.

-Chris