a queston for ron p

goingganzo

when you sold your velo ct 120 what did you sell it for? thanks

Bryan

Ron-P

Damn, reaching way back, $250 plus shipping and materials. I could be wrong, it's been a long time.


Peace Out~:D

caseymou

Ron P. you are correct! $250 and I have been pleased with it ever since. Lately, I have been eyeballing your home built sub though. I was wondering where you got the plans for it? It appears similar to the svs.

Ron-P

Glad to hear you've been happy with it. Velo makes some good subs.

I did not get plans for my sonotube sub, I got the idea from the hometheaterforum's DIY section and the people there that built them. They are very similar to SVS. If your looking into building one, the HTF is the best place to start gathering info.

I plan on building a second, a 12" instead of the 15" I have now. I'll probably get started in a month or so. Too many other projects going right now with the house revamp.


Peace Out~:D

Dr. Spec

Hey Ron, let's port this one. You stated you had trouble with some of the vent calcs and that's one of the reasons you went with sealed - I can help you. Venting will turn either your existing 15" or your soon to be 12" into a real powerhouse.

Ron-P

When it comes to porting, I can use all the help I can get. So, you say I can increase the power of my 15" by porting, any recomendations on length, dia.? It would be very easy to top port it.

I do plan on porting the 12" when I build it.


Peace Out~:D

Ron-P

Let me add that the sub is 177L, 20" x 36" enclosure with 6.5lbs. of poly fill.

It is a bit more boomy in the new theater and I like to tighten it up. Will porting achieve this? Also, I'd like to tune it somewhere in the high teens, 17/18 Hz or so.


Peace Out~:D

Dr. Spec

Ron, what is the I.D. of the top plate so we can determine how to fit multiple ports on top. We'll need to leave at least some room for structural integrity - that MDF will fracture if we get too close.

I have the specs for the Tempest 15" driver. This won't be very hard. Port area, port diameter, and port length for a 177L enclosure with a Tempest 15" with a requested tune in the low teens - no problemo. Here's my promise - if you eff it up based on my recommendations, I'll pay for a new top plate and the caulk, screws, and even a little for your labor.

You claim 105 dB at 20 Hz near the woofer? Try more like 110 dB near the ports at 20 Hz after venting. It will rearrange your hairstyle.

As for the boominess, it might be a room mode causing a nasty peak. Run a sweep and plot the FR and you'll know soon enough. I have the software - give me your email address. Venting will probably not fix a room induced peak - placement might, though.

Doc

gidrah

Help me tune a port for a 10" Dayton. I'll probably be going the sonotube route.

Ron-P

Doc, the ID is 20" and the plate thickness is 1.5".

The boominess is room induced. I get about an 8 db spike right in and around 50-55 Hz. I am flat across the board otherwise. I was not sure if changing the charactistics of the sub would change or do away with it. A BFD might be needed, but I like to avoid it if possible.

I don't have much hair to rearrange, but I'm willing to try.

Bring it on bro and thanks for the help.


Peace Out~:D

Ron-P

Hey Doc, do you know what the effect of a flared port vr. a non-flared port is?


Peace Out~:D

RuSsMaN

Slowing down the air gradually, less 'chuffing' (port noise).

Mark, which Dayton are you going to use?

gidrah

I got a Titanic MKII 1002 for Christmas. Totally unexpected. My wife overheard me talking to somebody about building one and BAM!

RuSsMaN

http://www.partsexpress.com/pdf/295-412.pdf

Page 9, box sizes with corresponding port sizes.

gidrah

Thank you kind sir. That's my kind of DIY. I'm too lazy to think, but I can copy like a ****.

Unfortunately I can't do pdf. I've tried downloading AA a few times. I really am a lost cause.

RuSsMaN

1.4 cu ft cab, port 3"D x 19.3" L

In room F3 18Hz

gidrah

What? Now I bet you expect ME to build it.

Thanks once again.

Micah Cohen

Look! It's a great thread! No petty crap here! Loads of great info! I love you guys, I knew you could do it! Keep it up!

The Warden

Dr. Spec

Ron:

I've played with a bunch of different equations and variables. According to the T/S parameters on the15" Tempest driver, your 177L enclosure is a bit undersized for a venting application, however, there is some breathing room (pardon the pun) in these equations.

Because you are only pushing the Tempest with 250W, I can slightly undervent your enclosure, and come up with a reasonable compromise that should still give you a significant boost in SPL and keep a fairly low enclosure tune.

I recommend three 3" ports each 23 inches long. This will give you a tune of 19 Hz and will flow very well considering you are only using a 250W amp.

The ports should be flared at the exit end at least or both ends if you plan on using a higher power amp in the future. A flared port allows a laminar flow of air at higher velocities than a square end, and can therefore be slightly undersized as compared to a square end port without encountering port noise or power compression at high output levels.

One caveat - once you go to a ported enclosure, the driver is no longer "protected" by the sealed acoustic suspension design, an can "unload" below the tuning point. Woofer excursion becomes extreme below the tuning point and bottoming can occur at high playback levels. If you really crank it, I advise the use of a subsonic filter set to 18 Hz or so.

Before you order the parts and get out the saw, feel free to get 2nd and 3rd opinions on my venting recommendations.

Doc

Ron-P

Doc, I chimed in on a thread over at the HTF. Here's a couple of responses...

Ron,

I used your driver specs and the volume you had in WinISD and came up with the port size. I used a volume of 212 L to account for the fill material. I noticed after I posted that you were looking for something around 18Hz. If you want that, it appears that you'll need to increase the port length to around 11 inches.

As for where to get them, I got a 4" flared port from PE for around $15. I plan on using rubber cement or some other non-permament binder so I can re-use them in the future. I'm not sure what the air velocity at the port would be, but the flared should work perfectly.

Do you want an F3 of 18Hz or just good output at 18Hz? If you go with 2 3" ports 11" long you will have a flat response to ~30Hz and an F3 of 22Hz. At 18Hz you will be about 6dB down, F10 is 16Hz. How does this compare to your current sealed rig: It slowly starts to roll off more so ~60Hz with an F3 of 37Hz. At 18Hz you will be about 11dB down, F10 is 19Hz. So by going ported it will give you +5dB more output at 18Hz or an F3 of 15Hz lower. These #'s are not exact but it will give you a good idea of what to expect. Hope it helps.

A 4" flared port 11" long will work nice just like Bryant said but the dual 3" flared ports will have a lower port air velocity. For simplicity reasons, I'd probably just go with the 4".

So, from these responses, it looks like a single 4" x 11" port (or) 2-3" x 11" ports will do the trick. Any comments Doc? Thanks again for your help.


Peace Out~:D

Dr. Spec

I think a single 4" or dual 3" is quite underported considering the xMax and Sd of the Tempest driver. But.....

A single 4" port with a 12" length will get you a F3 of 19 Hz. And two 3" ports with 15" lengths will do the same.

Want a higher F3 of maybe 22 Hz? One 4" about 8.5" long, or two 3" about 10.5" long. Jump to three 3" ports (which I still recommend) and you are at 16.5".

Ask those guys about underporting - the Tempest can move a LOT of air. You are only running 250W. You might be fine with a single 4" or dual 3" at 250W. If you step up to 500+W, the I don't think so.

Do they think three 3" ports is better for 500W? A general rule regarding port air speed is to try to keep it 10 percent or less of the speed of sound; otherwise port noise can become a problem.

Also, I noticed they used 212L as the internal volume. I think they were assuming you gave them the internal volume WITH the fill material included. I think you meant that you had 177L without the fill material, right? Quick calcs show a raw internal volume of around 186L, but with your double thick endcaps and driver, you might be down around 177 w/o fill. Is this right?

Doc

Ron-P

Gotcha.

The guys know that the hollow volume of the tube is 177L but filled with the poly-fill comes out to about 212L.

As for the power I'm putting into it, I'm running the 250w amp at about 1/3 the volume so I'm maybe putting in 90watts or so, far under the 250. It's way over-kill on bass if I pump more power in. Considering the size of the room, I'll most likey never go higher than the amp I'm using now.

Sounds like the 4" port at 12" is the way to go so I'll give that a try first and play around with it.


Peace Out~:D

Dr. Spec

The volume control on the plate amp is not an absolute setting - with sufficient LFE signal strength on the input side, you can definitely push the amp to full power, even at 1/3 volume setting. You might be surprised during loud playback at how much power you are feeding the Tempest.

Anyway, as long as you realize that the Tempest is underported with one 4" port, then you are probably OK up to 200-250W input before port noise and power compression becomes an issue. If you can, flare both ends of the port - this will definitely help when you are underported like this.

Remember, the 15" Tempest can actually take 750W of power, so at that level, utilizing the the entire xMax and Sd, even three 3" ports are slightly underported - that's why I went with my initial recommendation of three 3" ports at 23" - this set-up would have been good up to at least 500W and probably 117dB peaks on playback.

Remember, it's easier to cut port length than add it. :-) Start with 13" and run a sweep in the room and see how you like the FR - it should be flat to 20 Hz, with an F3 of 17-18 Hz.

Finally, don't stuff a ported enclosure like you would with a sealed one. Line the walls lightly (maybe 3" thick) with your polyfill and leave the center free between the driver and the port. You might need to experiment here with the polyfill - you need enough to damp standing waves, but not so much that you reduce efficiency or alter the tuning point.

Good luck and let me know how it goes! I think you'll like the ported Tempest!

Doc

Ron-P

move along...nothing to see here.

Ron-P

Here is an email response from Adire on their Tempest. Looks like I'll go with their recommendation for starters. What do you think Doc? They seem to be going along the same lines are what you are suggesting.

Ron,

Porting will extend the bass response considerably; I'd recommend a pair of
flared 3" diameter vents, each with an effective length of 17" (our FP-3
kits would be a suitable solution). This would tune you to 17 Hz, and
should provide considerably more output than your current subwoofer.

Thanks,

Adire Tech Support

Peace Out~:D

goingganzo

dr.spec do you know anything about slot loaded ports? and what is the diferance between a slot loaded vs round ports? i cant wait till my 15 get to me. so i have to decide if i want to go with slot loaded or round ports. if i doround this is my setup. four 4in ports at 18.22in long. my internal box size is 22 in high by 41in deep by 48in wide. with is 708 liters +the port volume. i dont know how many liters the woofers are. the hights is set and i cant go any bigger but the depth is changable

Dr. Spec

Yep, I'd take two 3" over one 4" all day long. This will flow better with lower velocity than the single 4" and the tuning length is very manageable. Looks like Adire and I are on the same page.

In the event you wanted to fine tune, here's some tuning lengths for the dual 3" set-up:

22 Hz = 9"
21Hz = 10.1"
20 Hz = 11.4"
19 Hz = 12.9"
18 Hz = 14.6"
17 Hz = 16.7"

Remember, woofer excursion skyrockets just below the tuning point. Be careful on stuff that has significant subsonic content - get a SS filter if you will really be cranking it. At moderate levels (105-108 dB bass peaks at the seat), you should be OK w/o it.

Ganzo - A slot port is created using one wall of the enclosure as a wall of the vent. In a slot port, the friction created by the air flow in the enclosure traveling along the enclosure wall makes this type of port effectively longer than it physically is - which tunes the enclosure to a lower frequency. So a slot port will be shorter for the equivalent vent area when compared to a simpler square vent. That's the advantage a slot vent has over a square vent just stuck in the middle of an enclosure wall.

I prefer the flow characteristics of a flared tube vent over a square or a slot port. If you have the room in the enclosure, personally I'd stick with tubes.

Doc

Ron-P

Thanks for all your help Doc. I'll let you know how she hits in a few weeks.


Peace Out~:D

goingganzo

thanks i will stick with the flaired round ports i am also tuneing to 16hz and i have pleney of space. thanks for the advice. ron you think you need more bass so you are adding a 12 to your setup? ron i think the new av12 is of similar design to the svs driver i know it is maid bu the same place

Dr. Spec

Originally posted by Ron-P
Thanks for all your help Doc. I'll let you know how she hits in a few weeks.

Kick ****, Ron. I can't wait to hear your impressions. This will almost be like adding a second sub - I'm expecting a 4 dB increase in output at anything above 30 Hz, and a huge (5-6 dB) increase in output below 30 Hz over the sealed design.

Ed

goingganzo

what that means is that you can actuley feel the diferance. it takes a on average a 3db change to hear the diferance