Port conversion

[CajunLB]

19 posts and still no mention of lube in a thread named "Port conversion"

Wait until @Danzilla31 comments. He knows his ports inside out with or without lube.

 

[Danzilla31]

Wait until @Danzilla31 comments. He knows his ports inside out with or without lube.

You definitely don't want to get me started on this conversation bro

 

[ryanosaur]

You definitely don't want to get me started on this conversation bro

No.
We do.
Get to it, Homepiece.

 

[TLS Guy]

I'm redoing the cabinet for an RBH SEN 1010.

I was considering ditching their round port and making something just a tad bigger to get a minimal reduction in air speed at the port ... just a thought.

It has a 3" diameter port that is 6" long total and the ends are flared (flares are within the 6" number)

The box it came from is 5500^3" minus the port and a couple of window braces or ~ 3' cubed

If I wanted to turn that into a slot port ... would 2"x5" for a length of 6.35" or so keep the same tuning?

Using this calculator the length for 2 ports of the 2x5" size would need to be 17.81".

Is any of this making sense?

EDIT:

I'm probably gonna reuse the round flared port due to the path of least resistance but wondering ...

Do you have the T/S parameters of those drivers?

 

[Alex2507]

Do you have the T/S parameters of those drivers?

No. I have a DATS Version 2 Woofer Tester toy that I haven't figured out how to use. I played around with it before but had trouble with adding weight or something along those lines. Am I gonna have to figure that thing out?

 

[Verdinut]

No. I have a DATS Version 2 Woofer Tester toy that I haven't figured out how to use. I played around with it before but had trouble with adding weight or something along those lines. Am I gonna have to figure that thing out?

Can you read a brand name label with model number for the driver?

 

[Alex2507]

Can you read a brand name label with model number for the driver?

Surprisingly, no. Let me try a couple of pic's ...

EDIT: I've got the DATSV2 sitting on the desk ...

This is what I started with ...

http://imgur.com/1U45LML

This is what I want ...

http://imgur.com/6kVwHtU

Forgive the blur on that side of the lens. What was on the other side (me) taking the pic right out of the shower, bent over for a better angle right as my girl enters the room ... I think she finally saw me for what I am.

Anyway, the first pic isn't blurry. What I'm doing is buying back those few inches the original sub sticks out past the steel.

All I want to do is replace the pictured port with a slot. That shouldn't require T/S parameters but at the same time I should know how to use this DATSV2 thing already. Otherwise I am no better than Doug.

Slid that in. Yuk, yuk, yuk

Oh and the whole thing started with having all this high density particle board cut into 12" strips and a ton of that Formica and about 2/3 of a gallon of contact cement. So I cut the pieces up in a shop and brought them home to completely drive my girl and my neighbors crazy by setting up shop on our small balcony. I don't play music loud often but that old Makita miter box strapped to the balcony rattles my teeth making cuts.

So back to it ...

 

[highfigh]

Fair enough…

but it would seem you are anti-fun-ctional if you want to leave a flat spot on a wheel!

One set for show (photos), one for go.

 

[highfigh]

Will you be testing the response by starting larger and adding material to reduce the volume as you go toward 5500 in³?

 

[Alex2507]

Will you be testing the response by starting larger and adding material to reduce the volume as you go toward 5500 in³?

All I want to do is replace the pictured port with a slot.

Okay, the truth is I am no better than Doug. The same way I don't know how to use a DATSV2, I don't know how to use REW.

Since we're doing pictures, this is what's going in besides wood bracing to eat up some of that space:

http://imgur.com/uIY1iTX

Hospital flooring and sticky sound panel used around an air handler above a ceiling at a dental school auditorium.

The Salk backdrop ...

http://imgur.com/C6b0RPB

Not all my miters look this good but this one will be most visible:

http://imgur.com/2fbB1VM

EDIT: I bought a fancy Plasti-Cut file just for that miter. Then I got to practice on the other 3 miters before this 4th and final effort. It's been a long time since I did any Formica work.

The scurge of tranquil, multi-family domesticity:

http://imgur.com/eqwdWjz

 

[Alex2507]

I guess I'm past the port conversion question as I cut the hole for the round one only to realize that my brace wants to meet my sawz all ... f^%&.

Mark, I don't know if you recall me wanting to break these drivers up to make two subs? You convinced me that the drivers needed to be in the same enclosure and that their alignment made sense.

We had talked about using a large slotted port vs a small tube on a different alignment. My low output requirement made the small port a contender but certainly not a preferred route to higher output. So what gives with the slotted port being pooh-poohed by these nay-sayers?

I've got a ton of flooring in there and a couple more pieces to go. The foam is used up. Knocking on it just hurts my knuckles and yelling "BOOM!" into the box makes me feel like an idiot. This is taking forever ... maybe there should be a little crying in DIY.

http://imgur.com/RPpOLnP

http://imgur.com/x7mSH7X

http://imgur.com/BS0bB2k

 

[Danzilla31]

I guess I'm past the port conversion question as I cut the hole for the round one only to realize that my brace wants to meet my sawz all ... f^%&.

Mark, I don't know if you recall me wanting to break these drivers up to make two subs? You convinced me that the drivers needed to be in the same enclosure and that their alignment made sense.

We had talked about using a large slotted port vs a small tube on a different alignment. My low output requirement made the small port a contender but certainly not a preferred route to higher output. So what gives with the slotted port being pooh-poohed by these nay-sayers?

I've got a ton of flooring in there and a couple more pieces to go. The foam is used up. Knocking on it just hurts my knuckles and yelling "BOOM!" into the box makes me feel like an idiot. This is taking forever ... maybe there should be a little crying in DIY.

http://imgur.com/RPpOLnP

http://imgur.com/x7mSH7X

http://imgur.com/BS0bB2k

Man JTR subs use slot ports and they're regarded as some of the best subs out there. Why would he use slot ports on subs at that level if they weren't good enough?

 

[TLS Guy]

I guess I'm past the port conversion question as I cut the hole for the round one only to realize that my brace wants to meet my sawz all ... f^%&.

Mark, I don't know if you recall me wanting to break these drivers up to make two subs? You convinced me that the drivers needed to be in the same enclosure and that their alignment made sense.

We had talked about using a large slotted port vs a small tube on a different alignment. My low output requirement made the small port a contender but certainly not a preferred route to higher output. So what gives with the slotted port being pooh-poohed by these nay-sayers?

I've got a ton of flooring in there and a couple more pieces to go. The foam is used up. Knocking on it just hurts my knuckles and yelling "BOOM!" into the box makes me feel like an idiot. This is taking forever ... maybe there should be a little crying in DIY.

http://imgur.com/RPpOLnP

http://imgur.com/x7mSH7X

http://imgur.com/BS0bB2k

Now you jog a senile old man's memory, yes, I remember.

You don't need to add weights. Just measure the T/S parameters on one driver. I can not answer your question without that data.

 

[Alex2507]

Just measure the T/S parameters on one driver.

This work?

http://imgur.com/jqQ85E6

 

[TLS Guy]

This work?

http://imgur.com/jqQ85E6

Yes, that will work! We are entertaining tonight. After Covid my wife is overdosing on invites. I will try and get to it tomorrow.
Those drivers will not dig really deep as Fs is 30Hz.

 

[Alex2507]

Yes, that will work! We are entertaining tonight. After Covid my wife is overdosing on invites. I will try and get to it tomorrow.
Those drivers will not dig really deep as Fs is 30Hz.

It was a pretty close call with the TDTOG thing looming. It took a little doing but I figured since you were asking it might behoove me to make that happen. I'll dig out the other driver for a comparison. Thanks.

Here's the other driver:

http://imgur.com/iuk9OUP

Pretty close, right? I figure their box was close to 3' cubed w/ that 3" wide fluted port of 6" length. I think their claimed F3 was 26 Hz. It seemed to be pretty heavily stuffed, not compressed but full.

It took like 20 tries before I was able to calibrate the leads and impedance. All set to 2 channel CD quality as suggested on PETT. I forgot most of what I knew when I tried using this thing before. My readings of a couple of pee-pee Infinity PS 10 sub drivers seemed so radically different that I couldn't be sure it wasn't operator error ... anyway, here we are again but this time I think I got it.

It wasn't all day spent on this but fo sho it was a good part of it. Thanks for the motivation. Now ... back to the cabinet.

 

[TLS Guy]

It was a pretty close call with the TDTOG thing looming. It took a little doing but I figured since you were asking it might behoove me to make that happen. I'll dig out the other driver for a comparison. Thanks.

Here's the other driver:

http://imgur.com/iuk9OUP

Pretty close, right? I figure their box was close to 3' cubed w/ that 3" wide fluted port of 6" length. I think their claimed F3 was 26 Hz. It seemed to be pretty heavily stuffed, not compressed but full.

It took like 20 tries before I was able to calibrate the leads and impedance. All set to 2 channel CD quality as suggested on PETT. I forgot most of what I knew when I tried using this thing before. My readings of a couple of pee-pee Infinity PS 10 sub drivers seemed so radically different that I couldn't be sure it wasn't operator error ... anyway, here we are again but this time I think I got it.

It wasn't all day spent on this but fo sho it was a good part of it. Thanks for the motivation. Now ... back to the cabinet.

Do you know the max power handling of those drivers? Also knowing xmax would be helpful, in addition to the sensitivity. None of that will affect tuning, but I would have to take an educated guess to get the size of the vent optimal for zero audible port turbulence. We have guests tonight, and we a having 14 for brunch tomorrow. I might get a chance to model this for you tomorrow afternoon.

 

[Alex2507]

Do you know the max power handling of those drivers? Also knowing xmax would be helpful, in addition to the sensitivity.

From the manufacturer:

Frequency Response:24Hz-180Hz (±3dB)
Sensitivity:90dB (2.83V @ 1 Meter
Recommended Power:200-400 Watts

xmax isn't listed. I don't think my Rotel RB-981 will do 200 watts per channel at 4 Ohm. It's spec'ed at 130 watts into 8 Ohm but rated for 4 Ohm speakers (without a power rating).

 

[Verdinut]

From the manufacturer:

Frequency Response:24Hz-180Hz (±3dB)
Sensitivity:90dB (2.83V @ 1 Meter
Recommended Power:200-400 Watts

xmax isn't listed. I don't think my Rotel RB-981 will do 200 watts per channel at 4 Ohm. It's spec'ed at 130 watts into 8 Ohm but rated for 4 Ohm speakers (without a power rating).

The rated output power depends on the Rotel's power supply. In my opinion, it probably won't produce double the wattage than with an 8 ohm load, as would happen with a solid linear power supply. But It will most likely be close to 200 watts with the 4 ohm driver.

I suggest that you verify with Rotel if you want a clear answer. They should be happy to give you a correct answer.

 

[Alex2507]

Slot ports and 90º angles introduce turbulence, thus affecting their efficacy.

... but if the slot port is big enough to overcome the efficacy issue?

why reinvent the wheel when RBH most likely designed the best system they could from the parts in question?

RBH is limited by size to a degree and cost beyond all else. Needing a differently shaped cabinet gave me a shot at making a really inert cabinet which RBH can't do at this price point. I just wanted to change the port over because circles are more challenging than slots. Cutting lines is easier than making circles.

But watch what TLS does with his choices in an alignment based on those T/S parameters. If he reinvents this wheel, I'm building it. The other subs he designed for me are freakin' choice. I finally have the perfect placement for them. Even the girl has been won over by them in their current locations right beside the couch like end tables. We've had a variety of sub solutions for that room, including the RBH SEN 1010. Granted, each cabinet is just over 100 lbs. Whatever the reason ... nothing I've heard sounds like them.

I suggest that you verify with Rotel if you want a clear answer.

It's not that important. I just wanted Mark to know that I wasn't likely to exceed the driver's power handling capabilities with the Rotel.

Why would he use slot ports on subs at that level if they weren't good enough?

It has to be those trade offs Ryan and highfigh were talking about. There must be some sort of rules, if/then type things that make one or the other right in different applications. I haven't read all my books on speaker design yet ...

still no mention of lube

Primal scream
Who put sand in the Vaseline?

In general, talk of lube on the forum is codified to help members maintain relationships with real women.

That cabinet is getting heavy at 80 lbs without panels. If you look at it, it's 3 boxes shaped like a "U". The backs of the driver boxes add up to 16 more lbs. I can pop the panels from either side for now to cut holes, add bracing etc. The Formica-ed top and sides will get Cherry nosing with a front and back caps with some veneer if I ever dig it out of Eddie's garage.

My girl is about sick of it. Like she's good but I don't think she wants to know that TLS is actually Dr. Mark Carter and that he designs speakers when he's not saving Loons, you know? I was almost ready to tell her what TLS meant! Lucky for me, she had someplace else to be and saved me from regaling her with more of what she didn't want to know.