Please help with a H/T sub using RL-P 15"

[warnerwh]

If someone could help me make sure I do this right I'd appreciate it.

I have a box I used for a sealed sub that is 9.0 cuft. It is 36"h x 26"d x 19" wide. These are outer dimensions.

The RL-P will use .21cuft. What the 6" port about 22" long takes up I'm not sure.

The amp is a PE 1000w plate amp.

In WinIsd with a 19.3 tuning frequency and 22" port and 7.5 cuft seems like a good compromise. This could easily be wrong as I've only built one other ported sub before. Besides I have brain fog from these meds I have to take. I know I make way more mistakes than usual and being a newbie figure it would be wise to have someone who knows what they're doing check my guesstimates.

After the large ported sub (24"x3'x4') using 2 of these same drivers I built last Jan I can hardly wait to have one for myself. The other I did for fun for a friend but had no idea what that thing was going to be capable of.

Thanks for any help.

[brucek]

If I use your dimensions of 36"h x 26"d x 19"w and subtract 0.18cu.ft for an RL-P15, and about 0.15cu.ft. for bracing, and 0.35cu.ft for the port, and include double thickness front and the rest of 3/4"MDF, then I get a working volume of ~7.66cu.ft.

With a 6" port at 22" long, the tune is 19.3Hz, as you indicated.

The port velocity looks a little high though at 36 m/s peak even with a 1st order electronics rolloff at 10Hz filter. I used 750 watts of power. The velocity doesn't get down to 8% until about 425 watts. At 750 watts, the velocity is OK when I use RMS instead of Peak for the velocity units. There has been talk that this may be more real world since music etc would be RMS rather than sustained peaks - but I simply don't know. That would indicate you need a larger port of 8", but then the length is un-workable.

Maybe the experts can comment on this........


warner.jpg
warner velocity.jpg

brucek

[warnerwh]

brucek: Thanks for the help.

Why does the port velocity matter? I realize there is the possibility of chuffing but don't know if velocity affects the performance of the sub.

Now I'm more confused than I thought I'd get.

[WillyD]

Why does the port velocity matter? I realize there is the possibility of chuffing but don't know if velocity affects the performance of the sub.

Many ported subs will have port chuffing in a certain frequency range at their highest output level. However, even though it often shows up and 'looks bad' on simulations, many don't notice it because they rarely crank their sub that high or a lot of the program material isn't in that freq. range where the port chuffing is a problem.

And where it affect the performance of a sub is compression.

But you really have nothing to worry about. A 6" port is pretty good for an Rl-p 15. Scores of folks have Rl-p 15s or TC-2000s or even SDXs and don't have any issues with a 6" diameter port.

[warnerwh]

Well I'm glad I have nothing to worry about. The performance is my main concern and I'm still wavering on whether or not to get another driver. If the guy has any more for 180 though I should have taken 2.

Our HT room is only 12x20 but having a bit too much is far better than not quite enough. If anyone thinks that a second driver may be a wise idea please let me know.
Thanks

[WillyD]

That is a killer deal for an Rl-p. Honestly, if you don't mind having another identical enclosure in your HT room, I'd go for it. Of course it'd make more sense if you were using a pro amp...

But one Rl-p tuned to ~19Hz with ~1000W is quite formidable in a overall sense, as you well know.

And I forgot to mention...

The port velocity looks a little high though at 36 m/s peak even with a 1st order electronics rolloff at 10Hz filter. I used 750 watts of power.

The 1000W amp that Warner will be using actually has a 3rd order subsonic highpass filter at 18Hz. Using the 7.66ft^3 and 19.3Hz tuning, it looks like the theoretical peak port air speed would be 30.6 m/s. A bit better. Like I said before, you'll be good.

[warnerwh]

HELP: I made a mistake on the dimensions of my box. This box is 36h x 28d x 19w.
I get 11.00 cubic feet.

My problem is that WinIsd keeps changing the vent tube length to thousands of inches long. Now I think I should tune this sub to 18 or 17. Being as this software problem is probably something I did but don't know what I would very much appreciate help.

If someone could model for me this box with the RL-P 15" or tell me what I am doing wrong to get those super long port lengths I'd be grateful. If you live any where near Portland, Oregon I'd be happy to buy you dinner.

[warnerwh]

My apologies for the error/s. It's some bad drugs from the Doctor and I have no choice but to take them. I'm just saying I'm not as much of a moron as it appears. Thanks!

[brucek]

I made a mistake on the dimensions of my box. This box is 36h x 28d x 19w.
I get 11.00 cubic feet.

If I make the change you specified, (and considering bracing, port and driver), I get an interior working volume of ~8.44cu.ft.

This allows the tune to come down to about 18.5Hz and still keep a port length of 21.88. I think you want to keep at least 6" from the port to the rear wall (if I'm not mistaken).

The air velocity is about the same. I feel it's high, but others don't appear to think so. Hopefully more people can comment on that issue.

warner 2 transfer.jpg
warner 2 excursion.jpg
warner 2 velocity.jpg

brucek

[warnerwh]

Appreciate the info, thank you.
The port will be put in going through the long way(36") so the end distance of the tube will not be an issue. The sub will have to be layed down on the long dimension as my wife said No Way to standing it upright because the top will be higher than the back of the couch. I'm going to put feet on it and make the driver face the floor.

Thanks again. I'm very excited as the driver will be here tomorrow. Now I have to get this heavy box up from the basement some how so it's ready tomorrow.

[warnerwh]

Thank you guys very much for your help. The driver arrived a day early (today) so I'll be getting things going very quickly. Must have taken me all of 3 minutes to line the box with fiberglass after my wife told me there's a large box on the porch.

Now we'll see if I could use another or not.

[brucek]

Now we'll see if I could use another or not.

It will be interesting to see if the response comes near the simulation or not - (if you do some REW response measurements).

brucek

[warnerwh]

You know learning how to use REW is a great idea. I have a laptop now. It seems like I just need a mike like the ECM 8000.

I'll download REW and learn how to use it in my tons of spare time. The dual RL-P 15" sub I'd like to measure also but my friend lives 200 miles away so I can't pop over there whenever I want because my wife would say bad things to me. (How the heck did I ever get into this predicament?) I'd been single for 48 years so adjusting to having input on my life isn't something I've gotten completely used to.

If I need anything besides a microphone please let me know as I'll go ahead and order one. I'd also like to measure the sealed sub I built using a PE RS HiFi 15" in a sealed box. Theoretically it should be 3db down at 30hz without room gain.

The amount of room gain we get would be a good thing to learn about as that will certainly affect the response.

[brucek]

If I need anything besides a microphone please let me know as I'll go ahead and order one.

With a laptop, there usually isn't a line-in connector (only a mic input, that isn't usable for REW), so you'll need an inexpensive external soundcard.

You can purchase a Galaxy CM-140 that combines a mic and meter in one. We have the calibration file for it on the download page.

I'd been single for 48 years so adjusting to having input on my life isn't something I've gotten completely used to.

Yeah, spend money on a soundcard and SPL meter and spend all day running sweep tones through your subwoofer. That will get you points with the wife. Woman love that sort of thing............

brucek

[WillyD]

The air velocity is about the same. I feel it's high, but others don't appear to think so. Hopefully more people can comment on that issue.

\

Hey Brucek, it appears that when you model you still aren't applying the 3rd order 18Hz highpass that is present in the Dayton amp Warner will be using. That lowers the air velocity some. And yeah, it is technically still higher than we'd all like, but thats what most ported 15" owners have to "live" with. I've never read a complaint and I don't believe Steve has. It'd require a pretty strong signal around the Fb, turned up to a high level. I guess in this instance, maybe a movie like Pulse would get the air moving well, but oh well.

[brucek]

it appears that when you model you still aren't applying the 3rd order 18Hz highpass that is present in the Dayton amp Warner will be using. That lowers the air velocity some

Yeah, it definitely makes a difference. I think he should be good. I was concerned that if he changed amps his filter wouldn't be there, but as you say, no one appears to experience much trouble.

brucek

[warnerwh]

I didn't know about adding the filter either. The more time I spend here the more I keep learning on how to do this.

Thus far if there's a weakness I don't know where it is yet. With the sub right behind the couch power is good. Even a nutso like me is content. Having another would be nice but I'd have to come up with some serious ingenuity to get it in there. The driver came yesterday and my wife has made me change it's orientation twice, that's 3 times in 24 hours.

There's nothing better to do than move the coffee table and couch and re orientate a 170lb box, especially being as I only weigh160. Never thought I'd see the day where some woman was telling me what I could do in my own house. This coming from a guy who used to wonder how guys could deal with that crap.