15" sub advice?

[Jim Holtz]

I've helped some good friends put together their 1st home theater. It's in a finished basement with a custom built entertainment center. All of the speakers are in-wall.

So, everything is done and they love the speakers. However, we're having problems with the sub. The sub is built into a space in the entertainment center and pointed directly at them. They set about 10' away from the sub.

The sealed sub cabinet is 29"W x 23"H x 16"D with a 1 1/2" front baffle. That should work out to about 125 liters or so. I recommended a RS390HF powered by an Oaudio 500 watt plate amp thinking it'd have plenty of "woofin" ability but I was wrong. It bottoms super easily and we've gone through two drivers, both of which developed the rattle of death after only bottoming a couple times. Yes, we were extremely careful but they just don't seem to be very robust construction.

Here's the problem. They're on a tight budget and have given me no more than $250 to work with to replace the sub driver. This is strictly for home theater "shake" and will be crossed about 60 Hz. or so. The only music that will be played is XM radio for back ground music.

I'm looking for a high xmax 15" driver with a F3 in the mid 30's that'll work in the cabinet that can be purchased for $250 or less. The Tempest-X looks like a winner but it's out of stock until at least February. Any other suggestions?

Thanks for your help!

Jim

[Mazeroth]

That's a bummer about the RSS390HF. Did PE allow them to return it?

I'm in the middle of building an IB with four of the RSS390HF and now you have me thinking I better be very careful with them!

[Jim Holtz]

That's a bummer about the RSS390HF. Did PE allow them to return it?

I'm in the middle of building an IB with four of the RSS390HF and now you have me thinking I better be very careful with them!

PE did accept a defective return without a question on the 1st one and I certainly hope they will on the 2nd. The RS390HF is very musical but after this experience, I think there are better home theater solutions. We had the sub cranked way down and then it bottomed on a scene in Ironman. That was the end of it.

The sub amp was also adjusted to try to eliminate subsonic frequencies too. It was very disappointing. I have a AV-15 MKII that runs circles around the RS390HF. I don't think I could bottom it if I tried.

Jim

[Hdale85]

125 liters seems like a lot for an RS driver? I thought they didn't need that much airspace?

As for other options...

http://www.mach5audio.com/zen/index.php?main_page=product_info&cPath=65&products_id=180

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-420

I'm sure there are other options..but I can't think of any at the moment.

[Blktre]

Actually, if you believe the specs PE they say a 116L sealed box is optimal for the RSS390HF. So I don't know if the extra air space is what caused this to bottom out.

You also have me worried as well. I'm just finishing up a RSS390HF in a sealed 22x22x22. With internal bracing and driver displacement I'm at 125L myself. Im planning to use the FBQ2496 and the Ep2500 in bridged mono. So my output will be alot more than that OAudio. I know for sure the 2496 will need to really be dialed in. But I sure didnt think this driver would blow under my conditions either. Maybe I should go ahead and add some more bracing to get the internal demensions down a few more liters.

Wow. Now Im really worried.

[---k---]

I guess I don't know as much as I thought I did. I didn't think that drivers would bottom in a sealed box, only vented.

[looneybomber]

I have a AV-15 MKII that runs circles around the RS390HF. I don't think I could bottom it if I tried.

Jim

That's the driver I was going to recommend...well, the AV15x or AV15h. I'd have to look to see how each models in a 125L enclosure to recommend one over the other.

You also have me worried as well. I'm just finishing up a RSS390HF in a sealed 22x22x22...and the Ep2500 in bridged mono.

That's way too much power. For an SDX-15, you'll be ok, but that's more than enough power for TWO rss390's.

I guess I don't know as much as I thought I did. I didn't think that drivers would bottom in a sealed box, only vented.

It doesn't matter the alignment, with enough power, a woofer's either going to burn or blow. It appears the rss390 is more thermally capable than it is mechanically.

[Jim Holtz]

That's the driver I was going to recommend...well, the AV15x or AV15h. I'd have to look to see how each models in a 125L enclosure to recommend one over the other.

I love my AV15 MKII. It's extremely clean and very, very robust. The new AV15-X is the closest fit to the specs I'm looking for except that the F3 is 52 Hz. per Unibox. No problem running out of xmax but the F3 is too high.

Jason, a moderator on AE's forum, is a friend of mine and he's trying to get through my head how the actual F3 is much lower than that in a sealed cabinet when you cross at 60 Hz. but I'm not getting it. I don't see how the F3 can go lower because of the crossover.

The next issue is, does John have any drivers availble?

A Tempest-X looks like the xmax I'm looking for and the price range my friends want to be in but I'm not sure how it works in a sealed cabinet and they're not available until at least February unless I could find one that someone wants to sell.

Thanks for your feedback!

Jim

[Jonasz]

Maybe one of the AE AV15?

http://aespeakers.com/shop/catalog/product_info.php?products_id=68&osCsid=9831d221968741942ad26abb0b272560

http://aespeakers.com/shop/catalog/product_info.php?products_id=67&osCsid=9831d221968741942ad26abb0b272560

Oh... already mentioned I see... ops:

[looneybomber]

Hmm, I don't have either driver in WinISD, so I didn't know the F3 was going to be so high. I'll take a look at this F3 thing, but I'm assuming what Jason is talking about is because maybe F3 is based off a point of reference? If referencing from 100hz it could be 3db down at 52hz. If referencing from 60hz, the XO point, it may be 3db down at 45hz (just throwing out numbers). If referencing from 30hz, an abscenely low XO point, it could be 3db down at 26hz.

I've always thought F3 was a static number, but if it's based on a point of reference, it could be dynamic.

[Jim Holtz]

Hmm, I don't have either driver in WinISD, so I didn't know the F3 was going to be so high. I'll take a look at this F3 thing, but I'm assuming what Jason is talking about is because maybe F3 is based off a point of reference? If referencing from 100hz it could be 3db down at 52hz. If referencing from 60hz, the XO point, it may be 3db down at 45hz (just throwing out numbers). If referencing from 30hz, an abscenely low XO point, it could be 3db down at 26hz.

I've always thought F3 was a static number, but if it's based on a point of reference, it could be dynamic.

I did some more modeling in Unibox and looked at the closed box sim. I now understand where Jason is getting the F3 from. Since I'm crossing at 60 Hz. the reference point moves lower which also moves the F3 down to about 39 Hz. While, that isn't really very low, it does get it down to the point where room gain will assist quite a bit. It's also impossible to bottom the AV15-X with 500 watts of power too.

Jim

[Hdale85]

In a sealed box the roll off is going to be rather mild so you're still going to get lots of output well below 39 hz.

[John_E_Janowitz]

Hi Jim,

Responded to your thread on our forum. I think the C15.3 we have left could be a good option for you, although in the useable range, the AV15H will give you more output per a given input power. Check the reply there and feel free to post anything back on here you wish.

John

[looneybomber]

I did some more modeling in Unibox and looked at the closed box sim. I now understand where Jason is getting the F3 from. Since I'm crossing at 60 Hz. the reference point moves lower which also moves the F3 down to about 39 Hz. While, that isn't really very low, it does get it down to the point where room gain will assist quite a bit. It's also impossible to bottom the AV15-X with 500 watts of power too.

Jim

Jim, the AV15x, SDX15, eD 16Ov.2, MJ-18M, and even twin Titanic 12's model very similar below 50hz. That's just the nature of sealed enclosures.

If your friend wants to use a bigger amp later in the future, you could get the SDX-15 with it's greater power handling and excursion, but it is over budget.

[Blktre]

That's way too much power. For an SDX-15, you'll be ok, but that's more than enough power for TWO rss390's.

Im pretty sure the FBQ2496 will be able to keep things under wraps. But, I will look at the other drivers you mentioned for Jim as well.

[cjd]

There is a rumble filter in place, right?

Ironman has some wicked low content, won't take the tiniest bit of power to run a driver out of excursion. The RS390HF is probably NOT built for this kind of a beating, but more for "musical" reproduction. Or, if you like, more sane bass output below 10Hz. Yes, I said below 10Hz.

[Rick Craig]

I've helped some good friends put together their 1st home theater. It's in a finished basement with a custom built entertainment center. All of the speakers are in-wall.

So, everything is done and they love the speakers. However, we're having problems with the sub. The sub is built into a space in the entertainment center and pointed directly at them. They set about 10' away from the sub.

The sealed sub cabinet is 29"W x 23"H x 16"D with a 1 1/2" front baffle. That should work out to about 125 liters or so. I recommended a RS390HF powered by an Oaudio 500 watt plate amp thinking it'd have plenty of "woofin" ability but I was wrong. It bottoms super easily and we've gone through two drivers, both of which developed the rattle of death after only bottoming a couple times. Yes, we were extremely careful but they just don't seem to be very robust construction.

Here's the problem. They're on a tight budget and have given me no more than $250 to work with to replace the sub driver. This is strictly for home theater "shake" and will be crossed about 60 Hz. or so. The only music that will be played is XM radio for back ground music.

I'm looking for a high xmax 15" driver with a F3 in the mid 30's that'll work in the cabinet that can be purchased for $250 or less. The Tempest-X looks like a winner but it's out of stock until at least February. Any other suggestions?

Thanks for your help!

Jim

The problem is that your enclosure size is too large for the driver, especially when you add in the equalization.

[Rick Craig]

I did some more modeling in Unibox and looked at the closed box sim. I now understand where Jason is getting the F3 from. Since I'm crossing at 60 Hz. the reference point moves lower which also moves the F3 down to about 39 Hz. While, that isn't really very low, it does get it down to the point where room gain will assist quite a bit. It's also impossible to bottom the AV15-X with 500 watts of power too.

Jim

You lose some output capability in the bandpass region by decreasing the bandwidth via the lower crossover point. If the driver has the excursion and wattage headroom to make up for it then it's not a problem.

[John_E_Janowitz]

The problem is that your enclosure size is too large for the driver, especially when you add in the equalization.

For all practical purposes I don't think you can ever really go too large on a sealed enclosure. Hoffman's Iron law shows that the enclosure volume is going to determine the low end output. Regardless of the enclosure volume, the woofer has the same overall output capability based on the amount of air displaced. What changes is the amount of power required to get to that level.

The following graph shows the output from the AV15H in various theoretical enclosure sizes with 1000W input. Enclosure volumes are .75cf(green) 1.5cf(yellow) 4.45cf(red) 20cf(orange) 2000cf(blue).



There is a point at around 50-60hz where all of these curves come quite close to each other. Where this point is really depends on the Mms, Bl and Cms of the driver. Below that point you can see that the larger the enclosure, the greater the output with the given input power. When you get down under 20hz, the difference is substantial. In the case of Jim's system where it will be used mainly under 60hz, the larger the enclosure the better. Less power for the same output is always a good thing. Above that point is where you see the benefit from the smaller enclosure. As the Qtc goes up, you get a boost in the higher frequencies.

John

[mazurek]

I have 4x 10" RS265HF. I think they have comparable displacement. My arrangement is linktwitz transformed to give second order rolloff with F=20Hz, Q=0.5. I also have a first order highpass on the woofers at 10Hz. The first order highpass at 10Hz does help to cut down on killer excursion.

I wouldn't want my system to play any louder (but that may be because the subs were calibrated flat to the remaining system). I see why you might try to get more low frequency out of the system though, my system just starts to give the feel of those physically tangible pressure waves of very low bass. But when I visited my friend Mazeroth's house with an infinite baffle in a small room, his did better. My high tech displacement gage (watching motion blur of blue tape on driver) says that I better not equalize the system any lower in frequency at the volume levels I listen to.

Its too bad, I don't know of any cheap off the shelf boxes that provides equalization that low in frequency. Maybe someone else knows.

I'm rolling around the idea in my head of highpassing my system at 40Hz and getting 4 18" drivers to play all those frequencies that I can't here but are an awful lot of fun.

EDIT: Oh, you went through two drivers, you don't have a sub with two drivers. In that case, you need more displacement or a smaller room.

[Rick Craig]

For all practical purposes I don't think you can ever really go too large on a sealed enclosure. Hoffman's Iron law shows that the enclosure volume is going to determine the low end output. Regardless of the enclosure volume, the woofer has the same overall output capability based on the amount of air displaced. What changes is the amount of power required to get to that level.

The following graph shows the output from the AV15H in various theoretical enclosure sizes with 1000W input. Enclosure volumes are .75cf(green) 1.5cf(yellow) 4.45cf(red) 20cf(orange) 2000cf(blue).



There is a point at around 50-60hz where all of these curves come quite close to each other. Where this point is really depends on the Mms, Bl and Cms of the driver. Below that point you can see that the larger the enclosure, the greater the output with the given input power. When you get down under 20hz, the difference is substantial. In the case of Jim's system where it will be used mainly under 60hz, the larger the enclosure the better. Less power for the same output is always a good thing. Above that point is where you see the benefit from the smaller enclosure. As the Qtc goes up, you get a boost in the higher frequencies.

John

I based what I said on both experience with the Dayton driver as well as looking at the excursion of drivers in lower "Q" enclosures.

[brent_s]

Something doesn't sound quite right with killing two 390HFs using a 500 watt amp in that enclosure. Does that enclosure have any stuffing that might be increasing the effective volume? Have you checked for air leaks?

The Reference subs are reported to have 20ish mm of suspension travel. WinISD shows the 390HF above 4.5 ohms impedance down to 15hz in that enclosure. Where was the rumble filter set? Even with no filter, the Oaudio shouldn't be able to exceed Xsus down to 10hz in 125 liters, although it would qualify as abuse if done repeatedly. Assuming the impedance model is accurate, the described alignment should start hitting Xmax just below 30hz with around 250 watts delivered with required power to Xmax dropping with frequency at the same time potential delivered power is increasing as impedance drops, but I just don't see Xsus induced damage unless the 390HF build house pulled another undocumented spec change on PE like the RS28 ferrofluid mishap.

You mention 1.5" baffle. What are the rest of the walls made of? Assuming .75" material the rest of the way, I'm getting 4.7 ft^3 (133 l) gross. Not a huge difference, but it does lower the necessary power to reach Xmax and Xsus.

Were there any in room frequency/spl measurements done? What do your friends consider loud? Even 250 watts should yield 102dB @ 1m ground plane at 20hz up to 110db @ 40hz. Inroom at 10' likely being the same or louder. Assuming it's balanced with the mains, that would be plenty of output in my book. Measuring during real world blow 'em up soundtracks with all 5.1/7.1 speakers engaged, I start to get uncomfortable around 100dB peaks...distance to front mains and sub is 11-12.5'.

Just anecdotal regarding the RS drivers durability, but I have a 315HF, rated at the same 14mm of Xmax as the 39HF. I've also got an SVS 12.2 driver from a friend who upgraded to the 12.3...reportedly the same driver offered by TC Sounds as the db500 spec'd at 20mm Xmax, 34mm Xsus. In identical ported enclosures their SPL and frequency responses measured identically (I literally just swapped each cabinet into the same spot), but the SVS driver actually started making distressed noises at the low end of the sweep before the the 315HF did as power was increased.

-Brent

[Bukem]

Have you considered the CSS SDX15? This model is quite popular in The Netherlands? LINK
The Xmax is double that of the Dayton Audio RSS390HF-4.

I am currently modelling a sub based on the RSS390HF-4 as well. The bottoming out does worry me a tad since I plan on using a linkwitz transform to arrive at a Qt of 0.500 (or 0.577 which is better?). I intend to use two drivers so that will help somewhat to reduce travel of each cone. Strictly music, moderate listening levels.

I would appreciate it very much if you guys could provide me with some advice on the matter. The way I see it there are three options:

1. Two separate sealed subs, each in a 60 L enclosure (Q=1.17 unassisted) transformed to Q=0.5 with a gain of 14.76dB and Fp of 17,55 Hz (instead of 20Hz which results in a negative k factor).
   
2. A single lightweight sub made of 400mm diameter 1m length PVC tubing with a driver on each opposing side of the enclosure. A classic push-push configuration. Single shared volume of 120 L, Linkwitz Transform as above. Factor of concern: 1st standing wave of 345/(2*1m)=172.5 Hz
   
3. A traditional (heavier) single sub of 30L with an isobaric mounting of the two drivers.
   Linkwitz transform as above.

I have included a response graph for various possible LT alignments + cone excursion. I noted 20mm has been mentioned above but the datasheet lists 14mm for Xmax. What should I use?

Best regards,

Bukem

[NEO Dan]

Why not put a MJ-18M in there, it's olny $155 delivered. You won't be able to bottom it