Need help with port length / size based on my enclosure

11344 Views 80 Replies 7 Participants Last post by muzz, Mar 23, 2015

TX1978

Discussion Starter · Feb 13, 2015

I will soon be embarking on my first sub build, and plan to put the enclosure inside a current wall void. The internal box dimensions that I came up with are as follows; 1.16' wide x 3.256' tall x 2.08' deep. This nets 7.9 cu ft for a Dayton rs5390hf. Don't worry about room between studs. I will handle that.

Since this will be "in wall" the driver and port will need to be on the front face. What size and length port do I need to hit 18 Hz?

Thanks!

61 - 80 of 81 Posts

muzz

· #61 · Mar 14, 2015

I think you misunderstood me.
I need the PORT dimensions in inches, and the net volume of the enclosure after all bracing/port.

EDIT: Ok, so I'm using 8.8ft^3 as the enclosure, I just need the dimensions of the port.

Thanks

TX1978

Discussion Starter · #62 · Mar 14, 2015

22" wide x 1.57" tall x 19.75 deep

These were the dimensions recommended by another user based on 8.8 cu ft volume, earlier in this thread.

muzz

· #63 · Mar 14, 2015

Unless the driver parameters I have are wrong for the RS390HO, At 500W, that driver is past it's XMAX a bit in that huge cabinet
I'm not 100% certain if the SPA500 HP filter is a 2nd or 3rd order, and if it's even a Butterworth Filter , but here are the cone excursions, Blue is 3rd order BW, Yellow is 2nd order BW- both are past XMAX <18hz, and right up against/ just past XMAX at ~ 28hz.
Maybe using that EQ on the amp and cutting a bit around 18-20 will save ya some, but I'd be careful with the power to that driver.
Maybe I don't know how to use Winisd, but here is what I get:

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jamesfrazier

· #64 · Mar 14, 2015

The Dayton will not by pass eq using lfe. Make sure your not boosting the lower signals too much. You are definitely damaging that driver. Those noises at the end sound horrible.

TX1978

Discussion Starter · #65 · Mar 14, 2015

Yikes. Thanks for the help guys.

Maybe the dimensions provided were for an 18" sub?
I could easily open up the mounting diameter and drop a new sub in... But will the port dimensions and box volume still be ok to achieve 17hz?

muzz

· #66 · Mar 14, 2015

Unfortunately, I do not know exactly what TYPE of High Pass filter is used in that SPA500.
I used a Butterworth 2nd and 3rd in that simulation, different types have different slopes.
I don't own a miniDSP, but it seems that it can do Linkwitz-Reilly 4th order, that would limit excursion to below XMAX, at the expense of a bit of low freq. extension.
Lots of folks use the miniDSP to setup their subs.

I purposely bought the iNuke 3000DSP so I could use the DSP to set my own High Pass.

muzz

· #67 · Mar 14, 2015

TX1978 said:
Yikes. Thanks for the help guys.

Maybe the dimensions provided were for an 18" sub?
I could easily open up the mounting diameter and drop a new sub in... But will the port dimensions and box volume still be ok to achieve 17hz?

I just went on to Parts express to get the T/S parameters for the RSS390HO-4, and the parameters I have in the file I already had are different than the ones I just entered manually, including the XMAX, which Parts Express says is 14MM, NOT 12MM...
Not sure where I got that File, but it's different from what I just manually entered.
With that being said,and using the T/S parameters that I just got, it STILL is over XMAX, actually it's worse than it was before.
Both sets say you are over, the ones I just got say you are over worse.
The actually shape of the SPL looks normal with the manually inputted values, the file I had been using had a hump at ~ 20hz
The Dayton UM15-22 is a bit better in that box, it is under it's XMAX limit of 19 in the simulation at 2nd/ Butterworth,Highest XMAX I see is at ~ 18hz, and it's around 18MM, at 3rd order Butterworth it's not even close.... too bad we don't know what type of filter is used......

The Stereo Integrity HT18 18" driver works in that box as well, not even remotely close to it's XMAX of 22.5, and it costs a whole $1.31 more than the RS390 shipped.

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TX1978

Discussion Starter · #68 · Mar 14, 2015

Sounds like the stereo integrity wins since it has a lot more factor of safety as far as xmax goes.

Just to verify, current box dimensions and port volume are acceptable w that driver to play sub 17hz?

muzz

· #69 · Mar 14, 2015

2

Here is the SPL graph with the driver you have, and the SI HT18 in your cabinet- unmodified except for the size of the cutout, the difference in displacement is small, so it won't change hardly anything, and not worth worrying about.
The graph is almost identical, with the HT18 just a tad higher SPL a little higher freq.....you can hardly even see the difference, but the Cone excursion graph below that shows a big difference.
The RS390HO has a 14mm XMAX- which it exceeds at 500W the HT-18 has a 22.5 Xmax, and it's laughing at 500W as far as XMAX
Pink is the SI HT18, Teal is the RS390HO:

Text Technology Line Software Electronic device

Text Software Technology Line Screenshot

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TX1978

Discussion Starter · #70 · Mar 14, 2015

Thanks so much. I owe you some brews

I will post pics of the new driver in a week or so.

muzz

· #71 · Mar 14, 2015 (Edited)

BTW- That's using a 3rd order Butterworth High Pass for both drivers, as I stated a few times, I don't know what type of filter the SPA500 utilizes, but you can see that no matter what the HT18 is laughing.

The only thing is the port is rather slim, the port Velocity for both drivers is almost identical, with the HT18 being very slightly higher....I would have made the port longer and taller myself.
Here is the port EDIT: Velocity you have in Teal, and a 22x3x40" port in Pink- like I said, before the pink was changed it was almost identical to the teal one- just a smidge taller- the tune/box is the same 20.69hz, just a longer and taller port to reduce noise.
Too late to do anything about it without tearing the cabinet down to change it, and most folks say they never hear port noise, so maybe you'll be one of those people- you can google it.
EDITS: General rule- Larger cabs can utilize longer and taller ports to Lower tune and/or reduce port noise, of course the larger port reduces net volume, so you have to account for that, the below chart shows it still at 8.8, and it would be less because of the longer port- at 8.8 NET it would look like below..

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muzz

· #72 · Mar 15, 2015 (Edited)

BTW, You want to order the HT18 D2 for that amplifier!

Wired in series it will present a 4ohm load to that SPA500, which supposedly is 540W(1/3 duty cycle- that's fine) at 4ohms, it doesn't mention 2 ohm loads at all, which means it probably doesn't do well at 2 ohm loading, the D4 in series is 8 ohms, which is a pathetic 270watts with the SPA500.

Get the D2!

TX1978

Discussion Starter · #73 · Mar 15, 2015

Already ordered it, even before you said so. I have played w car audio enough to know that dual 2 ohms wired for a 4 ohm load to match the amp is what I want.

muzz

· #74 · Mar 15, 2015

TX1978 said:
Already ordered it, even before you said so. I have played w car audio enough to know that dual 2 ohms wired for a 4 ohm load to match the amp is what I want.

Cool, no offense meant, just wanted to make sure, and it's better than the alternative.

TX1978

Discussion Starter · #75 · Mar 15, 2015

None taken.
Thanks for your help!

TX1978

Discussion Starter · #76 · Mar 20, 2015

Subwoofer Loudspeaker Audio equipment Electronics Studio monitor

New and improved...at least I hope so. About to start testing it out. Stay tuned!

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TX1978

Discussion Starter · #77 · Mar 20, 2015

Problem solved!

The new driver seems to play lower to the unaided ear. It definitely offers more bass that you can feel. Tested out some scenes in The Dark Night Rises...wow!

Thx intro on another disc has no issues now.

Thanks for the help muzz!

willis7469

· #78 · Mar 20, 2015

Glad to see you got this worked out.

muzz

· #79 · Mar 20, 2015

TX1978 said:
View attachment 86233

New and improved...at least I hope so. About to start testing it out. Stay tuned!

Now THAT'S what I'm talking about! :T

Glad I was able to help TX, enjoy your bad boy!:hsd:

TX1978

Discussion Starter · #80 · Mar 23, 2015

After a weekend of playing around with settings and listening to various movie scenes, I am blown away. The depth this thing adds to movies is unreal! Feeling and hearing soundtracks as they were meant to be is a new experience for me.

Thanks again for all the help!

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