Which (sub)woofer?

[djsixbillion]

So, I have a now-orphaned P.E. plate amp, which I believe puts out 270 watts @ 4-ohms. It's the one they don't seem to carry any longer, with a nifty remote for level and xo frequency. Anyhow, I'd like to build up a sub with this amp, for mostly HT duty (I have a separate 2-ch system). What drivers/enclosure type would you gurus recommend to best utilize this amp?

Single 15, vented, tuned to 20hz or less?

2 12's, vented, tuned to ?

Thanks!

[ThomasW]

Budget?

Desired SPL?

Max box size?

[djsixbillion]

Budget? Well, let's say $300 or less for drivers?

SPL, I'm not so sure, this will be going in a pretty small room (13x12, with 10 foot ceilings), so I don't think it should be too hard to get some good volume, and I do like to watch films at or near reference level occasionally. Let's say peaks of 100 db or so at 20 hz? Is that a reasonable expectation?

The box can be fairly large if need be. I'm thinking of building it as a stand for my center channel, which is placed underneath a front projection screen, so the max height for the sub enclosure would be 20" or so, but it can be as wide as needed.

Thanks, and let me know if you need any more info!

[djsixbillion]

Also, if it matters, I have a Behringer DEQ2496 for equalization...

[Kevin Haskins]

Budget? Well, let's say $300 or less for drivers?

SPL, I'm not so sure, this will be going in a pretty small room (13x12, with 10 foot ceilings), so I don't think it should be too hard to get some good volume, and I do like to watch films at or near reference level occasionally. Let's say peaks of 100 db or so at 20 hz? Is that a reasonable expectation?

The box can be fairly large if need be. I'm thinking of building it as a stand for my center channel, which is placed underneath a front projection screen, so the max height for the sub enclosure would be 20" or so, but it can be as wide as needed.

Thanks, and let me know if you need any more info!

Assuming your seating position is 2.5-3M your goal is easily achievable. Your amp may be the limiting factor with only 250-270W but at the listening postion a single Tempest-X in the large box tuned to 18Hz with a 8" port gets you about 112db @ 20hz using only 250W of power. That is figuring in a little power compression, port non-linearity, Cms/BL non-linearities etc... In other words... you should get within spitting distance of that number if your not measuring in a null. Oh... shouldn't be in a null with the size of your room.

[djsixbillion]

That sounds like plenty o' bass to me. Would that Tempest-X be a better choice for this amp than, say, a Dayton RS 15"? I'm going to be ordering some stuff from them soon, so it would be nice to get the free shipping.

What kind of rough box size would I be looking at for an 18 hz tune?

[ThomasW]

Box size for either will be about the same...

http://home.comcast.net/~klone-audio/page30AS-15-1.html

The Tempest-X with it's much higher Xmax for only a few dollars more is IMO a better long term investment. All you need to add is a bigger amp and bam!, instantly you've got a better sub.

Now I'm not saying the PE driver is bad, it's just the price doesn't buy nearly as much displacement.

[Kevin Haskins]

That sounds like plenty o' bass to me. Would that Tempest-X be a better choice for this amp than, say, a Dayton RS 15"? I'm going to be ordering some stuff from them soon, so it would be nice to get the free shipping.

What kind of rough box size would I be looking at for an 18 hz tune?

Your limitation is power. The Dayton RS 15 looks like a nice driver but I'd probably pick the DVC 15 over the RS simply because its cheaper, has about the same usable stroke (if not a little more) and its made by Eminence for PE.

The Tempest-X is in an entirely different class. More linear motor, more available excursion and it is targeted towards large box alignments. You won't use all that capability with 270W but you would get more linear output compared to either of the Dayton drivers. In a 12 cubic foot box, 8" port and tuned to 16Hz you get 112db @ 20Hz in the listening position. The Dayton doesn't have the excursion to support that output. In that alignment with 270W the Tempest-X is hitting 40mm of P-P cone travel around 25Hz. Your at 74% of the usable linear stroke of the Tempest-X and over the maximum available linear excursion of either of the Dayton's assuming they would work in the same alignment (they won't, probably work better in smaller enclosure sizes than 12 cubic feet).

[Kevin Haskins]

Box size for either will be about the same...

http://home.comcast.net/~klone-audio/page30AS-15-1.html

The Tempest-X with it's much higher Xmax for only a few dollars more is IMO a better long term investment. All you need to add is a bigger amp and bam!, instantly you've got a better sub.

Now I'm not saying the PE driver is bad, it's just the price doesn't buy nearly as much displacement.

Wow.... nice build. I need to get my CNC machine up an running. Just not enough time in the day...

[Dennis H]

The Dayton RS 15 looks like a nice driver but I'd probably pick the DVC 15 over the RS simply because its cheaper, has about the same usable stroke (if not a little more) and its made by Eminence for PE.

Not even close. See Monte Kay's tests. The 12" RS (same motor as the 15") has lower distortion than everything he tested including a 12" TCSounds. The only limitation is the shorter Xmax which, as Thomas says, makes the Tempest-X a better buy if you can handle the big box it requires.

[Kevin Haskins]

Not even close. See Monte Kay's tests. The 12" RS (same motor as the 15") has lower distortion than everything he tested including a 12" TCSounds. The only limitation is the shorter Xmax which, as Thomas says, makes the Tempest-X a better buy if you can handle the big box it requires.

What percentages? I'm not real concerned if one has 5% and another 7%. Its just not an audible difference at these frequencies. THD should also be interpreted based upon the type of distortion components. I can live with relatively higher amounts of even order, the odd order products are more of an issue.

[ThomasW]

Kevin,

You're supposed to argue in favor of using your drivers.... :B

Regarding the PE's Eminence built Adire 'clones'; in the last couple years I've brought in a few of these to replace damaged units for friends. For some reason the build quality on the more recent ones I've seen is marginal. One was DOA, another had something loose rattling under the dust cap. So compared to the new RS drivers I can no longer recommend the IB-15, or DVC-12"/15".

[Dennis H]

What percentages? I'm not real concerned if one has 5% and another 7%. Its just not an audible difference at these frequencies. THD should also be interpreted based upon the type of distortion components. I can live with relatively higher amounts of even order, the odd order products are more of an issue.

Well, you'd need to look at Monte's page to get the full picture. He uses Praxis and does the Linkwitz-style 3-tone measurements so there are a lot of graphs to look at.

I know you're busy so just picking 2 graphs, RS 12" vs original Shiva (closest to the DVC that he tested), driven with 10V in free air, mic near the dustcap, 40Hz center tone. I'm converting from dB to % in my head so don't shoot me if I get it wrong.

Shiva, 2nd 5%, 3rd 1%
RS, 2nd 1%, 3rd .3%

http://www.mfk-projects.com/woofers.htm

[Kevin Haskins]

Kevin,

You're supposed to argue in favor of using your drivers.... :B

Regarding the PE's Eminence built Adire 'clones'; in the last couple years I've brought in a few of these to replace damaged units for friends. For some reason the build quality on the more recent ones I've seen is marginal. One was DOA, another had something loose rattling under the dust cap. So compared to the new RS drivers I can no longer recommend the IB-15, or DVC-12"/15".

Hmm... Eminence has always been pretty good. I'm surprised to hear that.

I figure selling one driver makes little difference, especially if I have to lie to do it. :W

[Dennis H]

Just to be clear I wasn't talking about Kevin's drivers at all, just the RS vs. DVC. I'm sure Kevin's is much better than the DVC.

[Kevin Haskins]

Well, you'd need to look at Monte's page to get the full picture. He uses Praxis and does the Linkwitz-style 3-tone measurements so there are a lot of graphs to look at.

I know you're busy so just picking 2 graphs, RS 12" vs original Shiva (closest to the DVC that he tested), driven with 10V in free air, mic near the dustcap, 40Hz center tone. I'm converting from dB to % in my head so don't shoot me if I get it wrong.

Shiva, 2nd 5%, 3rd 1%
RS, 2nd 1%, 3rd .3%

http://www.mfk-projects.com/woofers.htm

I won't shoot you. ;-) I'd rather see finished system THD measurements, broken down by components. Thats where the rubber meets the mat. The single tone can miss trends that you might see in a broader band sweep. I'd also like to see measurements at several different power levels and as you near the limits of the driver.

They clearly have someone who knows how to linearize the inductance designing their motors though. That and the old Shiva is a 10-11 year old design. It didn't have a flat BL curve nor any consideration for inductance changes over the usable stroke of the driver. Eminence has been using a Klippel since those days and their motor designs are much better than the old Shiva or the DVC motors.

[ThomasW]

Over the years, the Adire clones I've seen from PE have never had the fit-n-finish of the 'real' thing. I know it makes no sense given they're all from Eminence, but that's my experience.

The new RS series are a totally different story, their fit-n-finish is amazing. Anyone else would be selling them for double PE's pricing.

That said, I think your Tempest-X is a better option for those wanting best 'bang-for-the-buck', since it would take 2 of the RS-15"s to come close to the same performance.

[Kevin Haskins]

Over the years, the Adire clones I've seen from PE have never had the fit-n-finish of the 'real' thing. I know it makes no sense given they're all from Eminence, but that's my experience.

The new RS series are a totally different story, their fit-n-finish is amazing. Anyone else would be selling them for double PE's pricing.

That said, I think your Tempest-X is a better option for those wanting best 'bang-for-the-buck', since it would take 2 of the RS-15"s to come close to the same performance.

Their source is the same people building my EX-6.5. They do a good job on the details. They don't have a lick of design talent though.... someone else designed that driver and it looks like they did a pretty good job on basic Le, BL & Cms curves.

Maybe Eminence is outsourcing those or more likely, PE sent one to China and had it copied. That would account for the difference in build quality if they went with the lowest bidder. ;-)

[Dennis H]

someone else designed that driver and it looks like they did a pretty good job on basic Le, BL & Cms curves

I think the RS tweeter is designed and built by Usher. It wouldn't surprise me if they were involved in the woofers too. They have plenty of experience copying Skanspeak drivers so they know something about good motors.

[Kevin Haskins]

I think the RS tweeter is designed and built by Usher. It wouldn't surprise me if they were involved in the woofers too. They have plenty of experience copying Skanspeak drivers so they know something about good motors.

That is what I was thinking too. There is someone at Usher that understands what they are doing. They just don't copy, they have changed and improved upon some of the motor designs and that requires someone who understands the physics involved.

The Usher mid-bass units look very good (motor wise). I wouldn't be surprised if PE didn't contract out the RS series to their engineering team.

[djsixbillion]

So, it sounds like the Tempest 15" is probably the way to go, but it sure likes large enclosures. I'm pretty sure I want to stick with a ported design since this will not be used much for music, but would it be too much of a compromise to use say a 6-7 cubic foot box, still tuned to 18hz or so? I did some quick sims in Unibox, and it looks like this will reduce the output at 20 hz by about 2-3 db compared to an 8.5 cubic foot box, but it would be much easier to move!

[ThomasW]

would it be too much of a compromise to use say a 6-7 cubic foot box, still tuned to 18hz or so? I did some quick sims in Unibox, and it looks like this will reduce the output at 20 hz by about 2-3 db compared to an 8.5 cubic foot box, but it would be much easier to move!

Using a box that size is fine, remember that Unibox doesn't factor in room gain, so you'll be getting some 'free' output down low....

[Mark Seaton]

Over the years, the Adire clones I've seen from PE have never had the fit-n-finish of the 'real' thing. I know it makes no sense given they're all from Eminence, but that's my experience.

Last time I checked, the IB/DVC 15 & 12" are still made by Eminence. It is important to note that these drivers are not really clones, but more akin to lesser, similar looking siblings of the Adire Shiva/Tempest drivers which they were meant to undercut in price. Particularly with the 15", the DVC & IB drivers use a 2" VC whereas the Tempest used a 2.5". Despite the coil overhang being similar, the overall performance is noticably different. While not the only difference, the most significant is found in the suspension.

Back to regularly scheduled number crunching... I agree the Tempest-X sounds like a good choice here.

[ThomasW]

Last time I checked, the IB/DVC 15 & 12" are still made by Eminence. It is important to note that these drivers are not really clones, but more akin to lesser, similar looking siblings of the Adire Shiva/Tempest drivers which they were meant to undercut in price.

Hi Mark,

Yep we know.....in this instance the word 'clone' was being used figuratively not literally....

[---k---]

Yep we know.....

Thomas, you must be using the royal for of we. Ye forget that not all of us have been around the block as many times as yourself.

[ThomasW]

Ryan the discussion about this was primarily between Kevin and myself. That's the 'we' I was referring to..