Driver replacement for Swope sub???

[Chris Roemer]

Re: Driver replacement for Swope sub???

Just as though you ran a measurement tape right down the middle of the curve.

[pastorola]

Re: Driver replacement for Swope sub???

Just as though you ran a measurement tape right down the middle of the curve.

Yeah that sounds logical. Thanks for all helpful input.

[greyson]

Re: Driver replacement for Swope sub???

Yeah that sounds logical. Thanks for all helpful input.

If you go with the RSS210HF-4, I can send you the CAD plans that I have for a slightly modified Pony. I made it a bit taller (30") and less deep (13" or so) to lift up the Overnight Sensations MTM I will have sitting on them. Word of caution, though: I haven't cut them nor assembled them yet, and I haven't finished the bracing. However, it should help you get a better idea of general layout and internal volume size with bracing, amplifier, and port added to them.

I'm hoping to get the panels CNC routered before the end of the year.

greyson

[pastorola]

Re: Driver replacement for Swope sub???

If you go with the RSS210HF-4, I can send you the CAD plans that I have for a slightly modified Pony.
greyson

Hey, that's really nice! However, I just decided to go with the Swope as designed by Paul Carmody but modified to host the Dayton RSS265HO-4. Just making the port slightly longer, everything else kept the same.

But thanks for a kind offer.

/Ola

[pastorola]

Re: Driver replacement for Swope sub???

Mind made up. I'm building the Swope sub with the Dayton RSS265HO-4.

However I can't find the exact numbers for the driver placement in the baffle. Anyone???

[pastorola]

Re: Driver replacement for Swope sub???

Help needed!

In the middle of building now. I am using Paul Carmody's original dimensions but I am using the Dayton RSS265HO. Will finish assembly of cabinet tomorrow or the day after.

Question; how long should I make the port??? I have recieved a couple different suggestions in this thread... Longer port will "steal" volume, right? I have the option to move back the piece holding the plate amp that's mounted 3/4" into the cabinet, if I need to compensate for volume that a longer port is "stealing".

[Chris Roemer]

Re: Driver replacement for Swope sub???

I'd like to help, but can't find a link to Paul's Swope sub anymore. I can assume you're using about a 32L cab w/a 3"id Precision Port, is that correct? And a plate amp w/NO boost, or are you going with a BASH?

Under those assumptions, I'd make your vent about 22 inches long.

[pastorola]

Re: Driver replacement for Swope sub???

I'd like to help, but can't find a link to Paul's Swope sub anymore. I can assume you're using about a 32L cab w/a 3"id Precision Port, is that correct? And a plate amp w/NO boost, or are you going with a BASH?

Under those assumptions, I'd make your vent about 22 inches long.

I found the Swope sub HERE

And yes, Yung 300 W plate amp w/NO boost.

22 inches? fbov suggested 25 inches for 35L cab, and jsr suggested 29 inches for 30L cab...

[pastorola]

Re: Driver replacement for Swope sub???

The internal volume for Paul's original cab, which I am copying, is about 42L before you subtract driver, port, brace, partial double baffle and plate amp volumes. Right?

[fbov]

Re: Driver replacement for Swope sub???

The thing about ports is that it's a matter of taste, not precision!
- too long tunes the box lower which improves bass extension, especially when considering room gain
- too short tunes higher, which gets boomy to my ears, but "punchy" to some folks.
- it's always easier to shorten a port that it is to lengthen it, if you leave enough room for a saw...
- A 1" change in a 25" port length is hard to hear, like 0.4Hz change in box tune and 0.3Hz change in F3.

Here are some calculations:
- you have a box with 18x21.75x9.5" external dimensions
- 3/4" MDF walls, with a double baffle and 3/4" recess for the amp gives 16.5x19.5x7.25, for 38.2L
(I'll ignore the brace as the double baffle is not full length in Paul's cut-away.)
- A 3" ID port, 26" long, subtracts 3.33L, so you're at 34.9L before the driver

How big is the driver? The magnet alone is 1.3L, so let's double that, leaving us 32.3L, so let's say 32L. Here are some options:

Port length / F3 / F10 / peak?
26" / 24Hz / 19Hz / none
23" / 24.4Hz / 20Hz / none
20" / 25.3Hz / 21Hz / none
17" / 26.5Hz / 22Hz / [email protected]
14: / 27.5Hz / 23Hz / [email protected]

As you can see, from 20" to 26" not much changes in response, so the ideal tune really depends on something we haven't discussed, the amp's low-end or infrasonic filter. Ported boxes will exceed X-max easily at frequencies below tune, so many amps include a filter to limit power below 20-30Hz. I can't find any documentation on the Yung's filter (not the "low pass" knob that limits the sub's high end), so I suggest using the longest port you can, to try and push the tune below the amp's filter onset and protect the driver.

I'll note that PE's 300W BASH rolls off nicely below 20Hz, protecting Paul's design when using a 25" port. It's an easy test with a frequency generator, available in freeware measurement software like Room EQ Wizard. Drop the frequency and at tune (24-32Hz in this example), the driver will move very little, but there will be lots of bass from the port. Go lower and see if the driver excursion picks up. If it does, you're not tuned low enough. If it doesn't, you can cut a little off, but I've always liked a very low tune as it gives great low bass when room gain is added in.

It's up to your tastes!
Frank

[jsr]

Re: Driver replacement for Swope sub???

I assumed a net internal volume of 30L. Different volumes will change port length required for a specific tuning. I couldn't find dimensions so I just used 30L since I recalled seeing that in one of Paul's posts.
Like Frank said, get in that area and play around to see what you like. You'll find room layout and placement will have a likely more dramatic impact than trying to hit an exact tuning.
The Yungs supposedly had a "30Hz" filter but someone tested it and found it to be 3dB down at 21Hz or so. A few Hz higher than a Bash default. Like the Bash, the Yung can be customized by changing a couple of resistors.
For these lengths, a slot port would be easier to manage. So maybe a test box using an external port to fine tune and use most of that test box to complete the final box later using a slot port.

[pastorola]

Re: Driver replacement for Swope sub???

Hey thanks for that input!

I have the cabinet almost finished, and a 3" pipe that is long enough to cut into different length, no problem. I cut the internal brace to fit as a port holder/stabilizer. I'll play around today a bit before I glue on the final panel.

[pastorola]

Re: Driver replacement for Swope sub???

I assumed a net internal volume of 30L. Different volumes will change port length required for a specific tuning. I couldn't find dimensions so I just used 30L since I recalled seeing that in one of Paul's posts.
Like Frank said, get in that area and play around to see what you like. You'll find room layout and placement will have a likely more dramatic impact than trying to hit an exact tuning.
The Yungs supposedly had a "30Hz" filter but someone tested it and found it to be 3dB down at 21Hz or so. A few Hz higher than a Bash default. Like the Bash, the Yung can be customized by changing a couple of resistors.
For these lengths, a slot port would be easier to manage. So maybe a test box using an external port to fine tune and use most of that test box to complete the final box later using a slot port.

What are the tuning then for 22, 25 and 29 inches for a 3 inch port tube?

And where can I find how to customize the Yung? Don't know if I'll ever do that, but knowledge can't be bad...

[jsr]

Re: Driver replacement for Swope sub???

I'll do that on Monday of you can wait. I'm not at work today and I don't have a computer at home.

I think the yung info is in a large thread on diyaudio if I remember right (but I have horrible memory). A Google search should find that thread. Look for a large thread. The info is toward the last several pages. Difficulty is about the same as the Bash. I think actually a bit easier as I recall the board the resistors are on are easier to access then on the Bash.

[pastorola]

Re: Driver replacement for Swope sub???

I can wait. No sweat. Wife wants some stuff taken care of in the garden, can't understand such crazy wishes right now, but who am I to judge