Confused NooB

[cpap pro]

Have a 2.1 cu/ft sealed box from a dead 15" downfire MTX PS15 sub. Suggestions as to which Parts Express 15" Sub driver and plate amp would work as a rebuild?

[johnnyrichards]

The 15" HF with some boost from the 300 Watt BASH.
The 15" "Classic" with some boost from the 240 Watt Dayton amp.

2.1 cubic feet is kinda small for a lot of 15" drivers, unfortunately. A better bet might be to either contact MTX for a replacement, or even better would be to cut a new baffle and install a 12" driver in there.

[philiparcario]

it is a down fire so buy a piece of mdf and make a cutout for a 12 inch dayton rss315 sub


http://www.parts-express.com/pe/show...number=295-444

if you can not do the cutting nikbrewer can cut you a mdf suqare with his cnc router


http://techtalk.parts-express.com/member.php?u=5472

nikbrewer
the inside hole needs to be 11 1/8 inches the square should be the same size as your sub box.

16 inches if that fits. cut two 3/4 inch ones and stack them. and take the feet off and reattach. you will get a better sub. nik can even do a round over so it will look good.

[WWWJD]

Hey, I'm gonna jump in here as another confused NooB, cause I have a question of a more fundamental level that parallels this topic..

Regarding enclosure size: It was said that the enclosure may be too small for the 15", and I guess looking at it from a T/S perspective, it would be... but...

What about power handling? Wouldn't the smaller box bump up the power handling of the driver? I would assume that if the user goes with a smaller enclosure, then the resonant point of the system will be higher, but in a sealed alignment, the only thing this is really going to change is excursion limitations on the bottom end.

The reason I ask, is that I'm designing a sealed subwoofer utilizing the RSS210HF; after searching, I've seen people using anything from 1 cubic foot sealed up to a couple cubic feet vented; with no comparison in between. On one thread in particular, I believe Darren K. stated that the recommended sealed volume for this driver was a mere 0.4 cubic feet. This pushes me in the direction of believing that T/S just doesn't matter for sealed subs as much as keeping the Power handling up.

Am I just rambling and hopelessly confused? or is there something to what I'm assuming?

[stangbat]

Is it a good idea to use the formula PE supplies to check if a sub should be used down or up firing? I've never mounted a driver in either configuration so I'm just bringing this up.
http://www.parts-express.com/resourc...nt-up-down.cfm

According to the formula, the 315HF is okay for down firing. The 390HF is not and neither is the 15" Classic. I haven't checked the other 15" subs, but I'm guessing that any of the 15" models won't make <5% sag and may not be a good candidate for down firing. Any comments on how accurate this formula is for figuring such a thing?

[philiparcario]

Hey, I'm gonna jump in here as another confused NooB, cause I have a question of a more fundamental level that parallels this topic..

Regarding enclosure size: It was said that the enclosure may be too small for the 15", and I guess looking at it from a T/S perspective, it would be... but...

What about power handling? Wouldn't the smaller box bump up the power handling of the driver? I would assume that if the user goes with a smaller enclosure, then the resonant point of the system will be higher, but in a sealed alignment, the only thing this is really going to change is excursion limitations on the bottom end.

The reason I ask, is that I'm designing a sealed subwoofer utilizing the RSS210HF; after searching, I've seen people using anything from 1 cubic foot sealed up to a couple cubic feet vented; with no comparison in between. On one thread in particular, I believe Darren K. stated that the recommended sealed volume for this driver was a mere 0.4 cubic feet. This pushes me in the direction of believing that T/S just doesn't matter for sealed subs as much as keeping the Power handling up.

Am I just rambling and hopelessly confused? or is there something to what I'm assuming?

assuming all t/s are correct an under sized box goes boom boom boom or a one note wonder. link for free box calculater and more


http://www.mh-audio.nl/spk_calc.asp

I am going to talk about sealed and your sub
rss210hf
fs is 28
vas is 1.14 cu ft
qts is .5 ideal box with a q of .707 is 1.037 cu ft
f3 is 39.6hz in that box
if you make a small tight box see what happens use a q of .9 instead of a q of .707
your f3 changes to 41.82hz in the small box of .46 cu ft
this becomes boom boom boom to your ears


look at the thumbnails look at the freq charts. smaller box will make a rise in the sound the redline in the frequency graph. the one on the right has more boom in the tighter box. boom shows as the redline going higher then o db. it is not a bad thing some of the time. that boom can help with a bad room response.
so a tighter box lets more power but you lose some extension in your case 2 or 3 hz 39.6hz vs 41.82hz for your f3 and if you look at the f6 on the charts it is more noticed. the ideal box is an f6 of 30 and the small box is an f6 of 35hz. some people fix all this by adding more power and eq. for me and my ears I have never heard a sub in a tiny box with a ton of power and eq that I liked. That does not mean anything at all to anyone but me. some people swear by power /eq/ small box. I have owned and got rid of all of them. i go with ib and fullsized sealed boxes for sub. that is my taste in subs

[cpap pro]

The 15" HF with some boost from the 300 Watt BASH.
The 15" "Classic" with some boost from the 240 Watt Dayton amp.

2.1 cubic feet is kinda small for a lot of 15" drivers, unfortunately. A better bet might be to either contact MTX for a replacement, or even better would be to cut a new baffle and install a 12" driver in there.

MTX does not service this sub any longer and will not provide any tech info on the dead amplifier. The woofer itself is still good but it is rated at 2 ohms. Thebest MTX would do was that if i sent them the driver and amp, they would sell me a SW1515 for $400.00.

[cpap pro]

Have a 2.1 cu/ft sealed box from a dead 15" downfire MTX PS15 sub. Suggestions as to which Parts Express 15" Sub driver and plate amp would work as a rebuild?

Now here is a silly thought....if i can find one, put a 15" passive radiator on the bottom downfire position and put a 12" front mount sub driver????? Huh? Huh?

[Mark65]

You might have something there, but I'm not sure if a single 15" PR is enough for a 12" driver, though....maybe a 10"? The Triska runs an 8" driver with two 8" PR's, so you have double the area. I don't know enough to know if that's critical, but I know that it's important to have enough area in the PR. I'm not awake enough to do the math for double the swept area of a 10 or a 12 vs a 15, but you certainly could, if the idea appeals to you.


Mark

[brianpowers27]

You might have something there, but I'm not sure if a single 15" PR is enough for a 12" driver, though....maybe a 10"? The Triska runs an 8" driver with two 8" PR's, so you have double the area. I don't know enough to know if that's critical, but I know that it's important to have enough area in the PR. I'm not awake enough to do the math for double the swept area of a 10 or a 12 vs a 15, but you certainly could, if the idea appeals to you.


Mark

Let's assume a 12" has 11" of area and a 15" has 14" of area

Area = sqare(1/2d) * pi
12" = 5.5*5.5*3.14 = 94.985
15" = 7 * 7 * 3.14 = 153.86

The 15" has 63% more area. The next question you should be asking yourself is in regards to how the box it tuned, with a PR. Keep in mind that the x-max of the PR is also a critical factor in PR sizing.

Unibox is the tool I have used in the past, to model PR setups.

[Mark65]

Let's assume a 12" has 11" of area and a 15" has 14" of area

Area = sqare(1/2d) * pi
12" = 5.5*5.5*3.14 = 94.985
15" = 7 * 7 * 3.14 = 153.86

The 15" has 63% more area. The next question you should be asking yourself is in regards to how the box it tuned, with a PR. Keep in mind that the x-max of the PR is also a critical factor in PR sizing.

Unibox is the tool I have used in the past, to model PR setups.

What he said.

So, following that, if a 10" woofer has 9" of area:

4.5*4.5*3.14=63.585, and your 15 is more than double that. Of course you're right, Brian, tuning and xmax are critical as well, floggings for me for forgetting that.

Mark

[Brent_S]

Downfiring a PR is generally a bad idea. Lots of moving mass with a floppy suspension doesn't yield long term service.

As a general rule, PRs should have at least double the displacement of the active driver. You could use a 12" PR with a 12" driver, if the PR had double the Xmax.

The 315HO looks good with an AE PR15-1050 in ~2 ft^3. This will give you a ~20Hz tune. With the rumble filter in the BASH-300, you're looking at an f3 of 20hz. From memory, WinISD sims ground plane at 1m as 105dB or better above 20Hz. This is actually one of my future projects; currently running the 315HO sealed (see my gallery for nearfield measurements) and have a PR15-1050 sitting in my project closet from when AE had it on sale for $50 last year.

The 390HO will give you a .7ish Q in 2 ft^3 sealed. The 500 watter that's currently on sale would probably be a good match. I think the 390HO's on the borderline of being a good (relative term) candidate for downfiring. WinISD put it's sag at 4.7%, IIRC. I'm not a fan of downfiring as it can never be truly good for the driver, but some are less effected than others and there are situations where it's unavoidable due to constraints that are more important than the last few millimeters of Xmax or potential longterm durability.

Just a reminder that not all drivers of a given size have the same cutout diameter and mounting hole location. For example, the 390HO requires a 1/4" larger cutout than the DVC15 and had a larger overall frame diameter, but both are 15" drivers. Hardly an insurmountable problem, but a caveat so that you don't limit your search based on a possibly incorrect assumption.

-Brent

[cpap pro]

Here is a 3rd possibilty for a solution-Get one of the 250W plate amps (original was rated 200 per sales info) and since driver is 2 ohm, put a/or several high watt wirewound resistors in series with the driver(the resistors themselves could be wired in paralell to attain specific resistance and dissapate more heat) so total resistive value would be 4~8 ohms. Is this doable since the driver is already apparently made for the downfire design.

[cpap pro]

Let's assume a 12" has 11" of area and a 15" has 14" of area

Area = sqare(1/2d) * pi
12" = 5.5*5.5*3.14 = 94.985
15" = 7 * 7 * 3.14 = 153.86

The 15" has 63% more area. The next question you should be asking yourself is in regards to how the box it tuned, with a PR. Keep in mind that the x-max of the PR is also a critical factor in PR sizing.

Unibox is the tool I have used in the past, to model PR setups.

If a 10" driver is available, i'd use it if it calculates out.....

[brianwalter]

If the driver is good, why don't you just bring the amplifier into an independent service center and get it repaired or at least get an estimate for repairing it. Another option would be to buy a pro-sound amp and drive it with that. Most decent pro amps will drive a 2 ohm load.

Brian Walter

[cpap pro]

If the driver is good, why don't you just bring the amplifier into an independent service center and get it repaired or at least get an estimate for repairing it. Another option would be to buy a pro-sound amp and drive it with that. Most decent pro amps will drive a 2 ohm load.

Brian Walter

MTX has no service centers that will service it any longer and does not have or will not provide schematics for the amp