IB sub driver suggestions

[Rolyasm]

The "box" size behind the speakers is about 2100 cf. Looking for one or two suggestions on current drivers I could use for this project. Either 15" or 18" and would like to be under $700 total for the drivers, if possible. Thanks for any suggestions.

[---k---]

4-Pack Tempest-X

http://www.diycable.com/main/product_info.php?products_id=659&Cid=ccc102f7f546840a80dfb784a2eb956d

Ask Kevin for his secret price on a Face amp while you're there.

[Kevin Haskins]

Mention the IB forum and you get free shipping too. The F700-TS bridged would drive a 4-pack easily.

[Concillian]

2x Fi 18 IB drivers are a better value, I think. I don't think overall performance is very different when comparing 4 Tempests to 2 Fi 18 IBs... the Tempests seem to model with a very slightly shallower rolloff resulting in about 1Hz lower F3 point.

Amping looks similar, both would be 2x2-ohm or 1x4-ohm, and Tempests hit xmax at 20Hz with ~300 W x 4 speakers, and the IBs hit xmax at 20 Hz with about 500W x 2 speakers.

So the Tempests are probably very slightly better, but 2 Fi 18's is about 2/3 the cost of 4 Tempests.

[ThomasW]

The Tempest-X have XBL^2 technology and a VERY low Le compared to the Fi IB drivers. This means lower distortion and a smoother transition between the sub and the mains.

Roly,

How far is the listening position from the IB and how loud is this IB supposed to play?

[Rolyasm]

I know this is cheap, but I was thinking more along the lines of a Behringer for the amp, though his amps do look nice. If I could find an amp for $300-$400, such as the EP2500, this would be a much more affordable project. I am trying to keep it around $1,000. I have used two Fi 18"s in a friend's room using the Beheringer, and it seemed to work fine. Looking at the specs I don't think it would have a problem with the Fi or the Tempest? Do you agree? Also, won't I get deeper extension with 2 Fi 18's vs. 4 Tempests? Not ruling anything out, just trying to go with the best option. Would one setup have possibly more mid-range extension vs. the other. My speakers reach 48Hz +/- 3 dB, so it shouldn't be an issue, just don't want any "gaps." Thanks again for the responses.

[---k---]

I have a Behringer. Thomas has been recommending it for years. It will be plenty good, if that is what your budget allows. The Face is nice enough that Thomas recently purchased one. And CJD the tempest 4 pack and the Face amp. So take that for what it is worth. There is a thread here where Thomas offers his thoughts on the Face.

Just note that the "special" price on the Face amps is reportedly ~40%.

[---k---]

How far is the listening position from the IB and how loud is this IB supposed to play?

What??? You think he may need 8 Tempest drivers??? :B

[Rolyasm]

Sorry, I was just responding while you were answering, Thomas. The listening room is appx. 23 ft. long with the first row of seats about 12 feet from the front of the room where the speakers will be. Don't need to shatter any eardrums, just some solid bass. Loundness, not sure, maybe 110dB at peaks, but that is kind of a guess.

[ThomasW]

If the goal is cheap go with the Fi's

As I already posted the Tempest-X with it's much lower Le will give a better transition between the IB and the mains.

BTW what happened to your other IB?

[Rolyasm]

My IB is working great. Thanks to you all. This is for a buddy. I love mine, as do my friends, and now they all want one too. I don't think $660 for the tempests and $300 for the amp is too much. If this is what you recommend. I will check on the amp prices before I go with the Behringer. Thanks

[ThomasW]

Amp deal

http://www.musiciansfriend.com/product/Nady-XA900-Pro-Stereo-Power-Amp?sku=482052

[Kevin Haskins]

What is the Sd & X-max of the Fi 18"? Also...what is X-mech? I'm not seeing it on their web site, the one reference to an 18" has an Sd of 1210 cm^2 which would translate to a small surround.

[cjd]

Mention the IB forum and you get free shipping too. The F700-TS bridged would drive a 4-pack easily.

Hey, when did this happen?!

F700 ROCKS a 4-pack. Man, watching those move with loooow frequency content is scary though.

Electronics heating up for the first time make an interesting smell too.

C

[JoshK]

Just for curiousity sake... I have a pair of Avalanche 15"s and a Crown K1. Do you think the Crown would drive a pair of A15"s with one channel and a pair of Tempest X's with the other channel OK (in IB)?

I guess I could do some modeling with SL's worksheet, or unibox or something similar for max power needed, xmax limits, etc.

I've been making slow progress on refinishing my basement, but when it is done I am going to install the 15"s in a floor mounted IB.

[ThomasW]

Just for curiousity sake... I have a pair of Avalanche 15"s and a Crown K1. Do you think the Crown would drive a pair of A15"s with one channel and a pair of Tempest X's with the other channel OK (in IB)?

Sure no problem. The K1 has input level adjusters so not a big deal to match the output levels of the drivers.

[Kevin Haskins]

Who is that Storm Trooper in your avatar Josh?

[Concillian]

The Tempest-X have XBL^2 technology and a VERY low Le compared to the Fi IB drivers. This means lower distortion and a smoother transition between the sub and the mains.

Not quite sure where you're getting this, Fi lists the Le for the 18 IB lower than the 15 Tempest-X... Unless the Fi drivers measure significantly different in actuality from their listed specs (which I doubt it'd be that far off).

You may be thinking of the SS RL-P 18s which have insane Le, I didn't see any show stoppers in the Fi 18 IB T/S.

[Concillian]

What is the Sd & X-max of the Fi 18"? Also...what is X-mech? I'm not seeing it on their web site, the one reference to an 18" has an Sd of 1210 cm^2 which would translate to a small surround.

**************URL removed by moderator****************is where the T/S info is listed. They don't put their IB drivers on the site, you have to go through email.

[ThomasW]

Kevin has the T/S parameters. He's a member of two forums where these drivers have been extensively discussed.

[Kevin Haskins]

Kevin has the T/S parameters. He's a member of two forums where these drivers have been extensively discussed.

Actually, I didn't until I hunted them down yesterday afternoon. I looked on his web site and couldn't find them. I participate in the lot of threads but I don't get around to all of them. :

[Kevin Haskins]

Not quite sure where you're getting this, Fi lists the Le for the 18 IB lower than the 15 Tempest-X... Unless the Fi drivers measure significantly different in actuality from their listed specs (which I doubt it'd be that far off).

You may be thinking of the SS RL-P 18s which have insane Le, I didn't see any show stoppers in the Fi 18 IB T/S.

The listed Le of our drivers is pretty meaningless information. It tells you the inductance of the coil @ center @ 1K. What is important about inductance is how it changes with coil posisition, frequency and power and how symetric that change is in relation to the rest position. Its a complex beast to understand. The importance of making it linear is the same as getting the BL flat. You want the effects to be the same on the outer stroke as on the inner, otherwise you create non-linear distortion.

There is also a flux modulation effect, as you increase power you get back EFM in relation to the size of the coil. This effect is opposite the normal BL field so its a type of compression. It also sets up eddy currents and a potential difference in the motor. Shorting rings are a way to short this field and lower these inductive effects but it requires spacing them appropriate to the task and designing them with the necessary thickness. You want the Le effects to be symetric on both sides of the available stroke and the only way to achieve this is to be able to model these effects. In other words, you have design the motor in such a way to take into account the Le effects throughout the range of motion of the voice coil, frequency and with different power levels. If you don't have the ability to model all of those, then you are shooting in the dark when trying to minimize Le effects.

[JoshK]

Who is that Storm Trooper in your avatar Josh?

I stole it off someone else in an unrelated forum. I thought it was funny and it reflects the fact that I don't take myself too seriously.

[---k---]

I find it very disturbing.

[Kevin Haskins]

My kids like it but they don't know what they are looking at.

[Dennis H]

Fi lists the Le for the 18 IB lower than the 15 Tempest-X

I couldn't find that spec on their website. Aside from the in-depth comments Kevin posted, it's important to understand that Le by itself doesn't mean much. Le/Re is the important number. Fi lists Re (and presumably Le) for a single coil, either 1 ohm or 2 ohms nominal. Kevin lists Re and Le for the two 8-ohm coils in parallel or a 4-ohm nominal load. So the Tempest could have either 2x or 4x the Le of the Fi and still have the same Le/Re which is what matters.

[Kevin Haskins]

Scott's probably using a 2" VC. I haven't looked carefully. For an IB specific driver you don't need the BL because you want a fairly high Qtc. That is the only reason you could have fairly low static Le on an 18" driver. The Le on our 18" driver in the prototype stage is much higher than the Tempest-X. Its a larger 3" core and we aimed for a driver that could be used in reasonably sized ported or sealed alignments also, hense the larger coil to get the extra BL and better power handling.

We also have a DPL-15 in the proto stage. Its using a 2.4" VC but its static inductance is extremely low. It also uses and XBL^2 motor and AlCu inductance shorting rings to linearize Le. It works a lot like the Scan Speak SD-1 motor technology. It has a little more Sd than the Tempest-X and probably 2-3 mm less X-max. Because the Sd is larger the total displacement is pretty much the same. It will only be about 18lbs and the motor structure is much smaller than the Tempest-X. Cost should be VERY reasonable with a projected cost of $100 shipped (about $25/L of displacement) and it will have very good power handling, even though it doesn't require much to get to full power. It should be the ultimate IB/dipole 15" driver.

I'll write up a technical paper on Le someday. Its a topic that isn't very well understood by most of the DIY community. I'm no expert but I have access to a couple that can sharp-shoot my paper.

[Johnloudb]

I'm modifying a stereo pair of old Nelson/Reed subs. They are dipole and have four 12" woofers each, volume of 127L (4.5 cf). They used EQ to flatten the response - anyway I'm going to make them sealed. I'm just trying to decide on a the woofers. Two woofers per box.

Both of these 12" would work, does 12" epic have lower distortion? Worth $1200 for 4?

Epic 12" (dual 4ohm version)

Dayton 12" HF 4ohm

[Rolyasm]

Thanks, the Tempest 4 pack arrived yesterday. Heavy beasts. I'll let you know how they sound.

Roly

[Rolyasm]

Wiring the IB

Just got the basement finished and we are ready to wire the subs. Again, using the Behringer 2500 with 4 Tempest X. Here is how I thought I would do it.

http://www.crutchfield.com/learningcenter/car/subwoofers_wiring.html?imageID=4DVC%5F4%2Dohm%5F2ch

I think that will give me 2- 8 ohm loads. Any suggestions? Should I try to wire to get a little more boost and go for a 4 ohm load? Any diagrams are helpful. The Tempests are dual 8 ohm voice coil.
Thanks.
Roly

[collo]

Each channel: Two drivers in series, each having their coils in parallel giving 6.8ohms.....extracting around 600w / channel from an EP2500

Aussie writeup on Tempest-X / EP2500 IB

[Dennis H]

Each channel: Two drivers in series, each having their coils in parallel giving 6.8ohms.....extracting around 600w / channel from an EP2500

Aussie writeup on Tempest-X / EP2500 IB

I think it's better to wire the coils in series and the drivers in parallel like Roly's link. There's a theoretical risk of setting up a resonance near Fs with the drivers in series if the T/S parameters aren't identical. John K did a paper on it. It's probably not a big deal in the real world but why take the risk when it's possible to wire the drivers in parallel with the same overall impedance?

[WillyD]

The Le on our 18" driver in the prototype stage is much higher than the Tempest-X.

Is this the Maelstrom you're referring to? Cause I don't see how it could be much higher. Its great as is!

[Dennis H]

High Le (or more properly Le/Re) is a BAD thing....

[WillyD]

Are you replying to me? I am aware of that. The "much higher" in my post come from his statement of the prototype having much higher Le than the Tempest. The Maelstrom has a pretty low Le. It has a ratio of .28 vs the Tempest-X's ratio of ~.246.

[Rolyasm]

Just to clarify. So I am connecting a positive on coil 1 to the negative on coil 2, on each speaker. On Crutchfields...

http://www.crutchfield.com/S-qy3uOBuFqOE/learningcenter/car/subwoofers_wiring.html?imageID=4DVC%5F4%2Dohm%5F2ch

I see that they have the negative amp channel going to the negative of one speaker, and then from that negative to the other speaker's negative. So far so good.
However, they have the positive amp going to the negative terminal (the one that is wired to the postive on the other voice coil)? Shouldn't the amp's positive go to the positive on the speaker, and then from there to the other speaker's positive? Thanks for any help.

Roly