Subwoofer Tests - Fall 2007

**mojomike** · **10-20-07, 09:09 AM**

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SteveCallas wrote:

Lastly, I'll never be a fan of the concept of reducing port area to achieve a lower tune - that's about as backwards as you can get. The low end numbers look nice in the lower tuning modes, but the onset of audible chuffing becomes that much more of a reality.

Steve, the port limitations don't seem to be a problem at the 15hz tune. You'll notice that there is very little loss of efficiency in this tune compared with the 20 hz tune. I haven't seen any port chuffing in either 20 or 15hz tuning. As for the 10hz mode, I doubt a single 3.5" port could be sufficient. There is a marked loss of efficiency in this mode and I'm sure it's underported here. Chuffing here could be a problem, but it should only show up with very low frequencies.

**Ilkka** · **10-20-07, 04:13 PM**

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Peter Marcks wrote:

The Conquest must be tuned somewhere in the 15Hz area (give or take 1-2Hz).

Sorry but I don't agree.

When looking at the external measurements, the internal net volume can't be much more than around 240 liters (1" walls, 2" baffle, bracing, driver, ports). That means 15 Hz tuning would require around 2 meter long ports!

I'm guessing that the Conquest is tuned much higher, maybe around 20-22 Hz.

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Exocer wrote:

wow, just wow. Can't wait for Ilkka to get his hand one one...

I will test them as soon as Chad gets some 230V amps.

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Just out of curiosity, ~ what tuning point could one achieve from plugging one of the Conquest's ports?

If assuming native is ~22 Hz, then single port would be ~15 Hz.

**Ilkka** · **10-20-07, 04:21 PM**

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WillyD wrote:

And what the PB13 can do for its enclosure size/porting solution doesn't impress me. It is a pretty big sub as far as commercial subs are concerned. Around 200gross liters, right?

The net internal volume of the PB13-Ultra is around 120 liters. So it's more than twice smaller than the 270L LLT.

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The qusi-LLT isn't that much larger than the PB13. About 3ft^3 larger, eh?

I've seen them both in reality. Believe me, the 270L LLT is MUCH larger (footprint of course is pretty similar).

When I saw the PB13-Ultra for the first time (and still), I actually thought it looked really small. It's much smaller (height) than, say, the older PB12-Plus/2.

**chengbin** · **10-20-07, 08:26 PM**

IIkka, do you mind putting the f113 driver in a large enclosure such as the size of a PB13U and test it? Thanks. I'm sure the result will be very interesting.

**DLS** · **10-21-07, 02:42 AM**

Quote:

chengbin wrote:

IIkka, do you mind putting the f113 driver in a large enclosure such as the size of a PB13U and test it? Thanks. I'm sure the result will be very interesting.

I was just thinking about the same idea

13w7 driver in PB13's type of design.
Having working with the 13w7 car audio driver (I would guess this one in fathoms is similar), maybe big LLT won't work well in terms of SQ. But something like 130-150L tuned to 20 or below Hz may be a pleasant surprise

**SteveCallas** · **10-21-07, 12:51 PM**

If a driver is designed to work best in a small sealed enclosure, that typically means it has a very low Qts, which means it won't work well in a large ported design, as the low end will be way too peaky. If you make the enclosure just the right size for a low frequency tuning, you end up with not enough volume to use proper porting.

**DLS** · **10-21-07, 02:05 PM**

Quote:

SteveCallas wrote:

If a driver is designed to work best in a small sealed enclosure, that typically means it has a very low Qts, which means it won't work well in a large ported design, as the low end will be way too peaky. If you make the enclosure just the right size for a low frequency tuning, you end up with not enough volume to use proper porting.

Actually, if my analogy with the car version of W7's is right, then Qts isn't that small at all - 0,448. I could guess its a little over 100L VAS is no good for ''real'' LLT, but simulations shows pretty good results in let's say 150L. In this case Fb could be 20 or even less Hz and the graphs looks good, no peakyness. The port area I think would be almost enough while keeping the first port resonance high enough not to be a concern.
The only thing I have doubts about is the acceptable level of GD.
I'll do some modeling to check again if the old calculations I've done for this driver confirm my thoughs above.

**WillyD** · **10-21-07, 02:40 PM**

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I'm guessing that the Conquest is tuned much higher, maybe around 20-22 Hz.

Thats what I thought as well.

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The net internal volume of the PB13-Ultra is around 120 liters. So it's more than twice smaller than the 270L LLT.

Wow, I had no idea that it was only ~120liters net. Kind of hard to believe!

**chengbin** · **10-21-07, 03:42 PM**

Quote:

SteveCallas wrote:

If a driver is designed to work best in a small sealed enclosure, that typically means it has a very low Qts, which means it won't work well in a large ported design, as the low end will be way too peaky. If you make the enclosure just the right size for a low frequency tuning, you end up with not enough volume to use proper porting.

That's not true. if JL wanted to, they could of build a enclosure that allows the driver to extend flat to 5Hz!! But they didn't because it would be inappropriate. http://home.jlaudio.com/pdfs/AbsoluteSound.pdf. Read the last page. I think if some DIYers wanted to, they should be able to get it to extend flat to 10Hz easily. Then measure it, the results will be very interesting.

**Ilkka** · **10-21-07, 04:12 PM**

Sorry guys, I'm too excited (and drunk

) because of Kimi's World Championship (Formula 1 to all of you Americans

) that I can not answer to your questions right now. I'll tackle them tomorrow.

Forza Kimi!! Forza Ferrari!!

**ISLAND1000** · **10-21-07, 05:43 PM**

Listen to him . . . . . "he's too drunk" !! Our test man . . . . too drunk!! What's this world coming too . . . . and who's this KIM person . . . . . have WE given her an OK?

I dunno Ilkka . . . . . we might be looking for your replacement soon . . . . . craigsub, you still out there???? LOL

**Ilkka** · **10-21-07, 06:03 PM**

Quote:

ISLAND1000 wrote:

Listen to him . . . . . "he's too drunk" !! Our test man . . . . too drunk!! What's this world coming too . . . . and who's this KIM person . . . . .

http://www.formula1.com/
http://www.ferrariworld.com/FWorld/fw/index.jsp

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have WE given her an OK?

Her???

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I dunno Ilkka . . . . . we might be looking for your replacement soon . . . . . craigsub, you still out there???? LOL

**SteveCallas** · **10-21-07, 07:03 PM**

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That's not true. if JL wanted to, they could of build a enclosure that allows the driver to extend flat to 5Hz!! But they didn't because it would be inappropriate.

Yeah, ok

If they piled on enough EQ to get their sub flat to 5hz, max headroom while staying flat to 5hz would be well under 90db - what's the point in that?

Quote:

Actually, if my analogy with the car version of W7's is right, then Qts isn't that small at all - 0,448. I could guess its a little over 100L VAS is no good for ''real'' LLT, but simulations shows pretty good results in let's say 150L. In this case Fb could be 20 or even less Hz and the graphs looks good, no peakyness. The port area I think would be almost enough while keeping the first port resonance high enough not to be a concern.
The only thing I have doubts about is the acceptable level of GD.
I'll do some modeling to check again if the old calculations I've done for this driver confirm my thoughs above.

20hz tuning and a 4" port is not a LLT, far from it. And maybe I'm out of the loop, but I don't believe JL has ever released the TS parameters of the driver used in the sub in question.

**chengbin** · **10-21-07, 07:11 PM**

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SteveCallas wrote:

Yeah, ok

If they piled on enough EQ to get their sub flat to 5hz, max headroom while staying flat to 5hz would be well under 90db - what's the point in that?

I'm very sure they mean without EQ boosts, but like incredibly large enclosures with multiple ports tuned really low, or other ways to boost bass without EQ.

**DevilDriver** · **10-21-07, 07:40 PM**

From what I have been told, the driver used in the Fathom and the Gotham employs a similar motor to the W7 with more BL, more excursion, and more power handling (probably via a larger coil). If that's the case (without too much mass), that would push the Q down a bit and make it more suitable for a small, sealed enclosure.

But no, I've never seen any measured parameters. Maybe someone should take theirs out and test the driver itself, thoroughly.

**SteveCallas** · **10-21-07, 08:03 PM**

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I'm very sure they mean without EQ boosts, but like incredibly large enclosures with multiple ports tuned really low, or other ways to boost bass without EQ.

That's not gonna happen. I'm using a 7' tall, 650 liter enclosure with an 18" driver, and there's no way even that could be tuned and stay flat to 5hz. The port length would be far too long, and no driver can displace enough air to naturally stay flat that low.

You'd need multiples of drivers in a SLLT as wel as some potent room gain. Or even more drivers in an IB and plenty of EQ.

**chengbin** · **10-21-07, 08:16 PM**

Is there any EQ boost on the F113? I don't think so, but I'm not 100% sure.
BTW, that's a HUGE sub you're using. WOW. The PB13, with "only" 120 liter enclosure, is very big to me. 600 liters, my...

**chengbin** · **10-21-07, 08:28 PM**

How do you calculate the length and width of a port for a certain frequency?

**mojomike** · **10-21-07, 08:47 PM**

Quote:

chengbin wrote:

Is there any EQ boost on the F113? I don't think so, but I'm not 100% sure.
BTW, that's a HUGE sub you're using. WOW. The PB13, with "only" 120 liter enclosure, is very big to me. 600 liters, my...

You can bet that the f113 has built-in EQ boost. Woofers in relatively small sealed boxes will have a natural roll starting fairly high up. For the f113 to have a flat response to below 20hz, it must have EQ. It is part of why it need such a powerful amp.

**DLS** · **10-22-07, 01:29 AM**

Quote:

SteveCallas wrote:

20hz tuning and a 4" port is not a LLT, far from it. And maybe I'm out of the loop, but I don't believe JL has ever released the TS parameters of the driver used in the sub in question.

150L, 16Hz Fb, 5" port - that's what I had come with some time ago. F3 is 26Hz, FR looks good and smooth

.
And again I'm asuming the car and home versions of W7 being identical.
Actually, Steve, maybe that's not a "real" LLT, but doing such designs I'd never happen to run into your theory (exellent work btw

) since recently.

**noah katz** · **10-22-07, 01:44 AM**

"If a driver is designed to work best in a small sealed enclosure, that typically means it has a very low Qts, which means it won't work well in a large ported design, as the low end will be way too peaky."

A driver optimized for sealed has a higher Q for two reasons:

1) High Mms (which raises Q) will be needed to get a reasonably low Fc

2) Being a single-mass system, it will be overdamped with low Q; vented systems need extra damping to control the second mass (port air/PR)

**chengbin** · **10-22-07, 04:13 AM**

I thought so too. Does the Gotham have EQ boost? It has the same FR as the f113. Is the gotham just 2 W7 13 drivers in an enclosure? If it is, then why is it 3 times the price of a f113?

**Egil** · **10-22-07, 05:27 AM**

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chengbin wrote:

I thought so too. Does the Gotham have EQ boost? It has the same FR as the f113. Is the gotham just 2 W7 13 drivers in an enclosure? If it is, then why is it 3 times the price of a f113?

If I remember correctly, the Gotham has different drivers.

EQ boost? Yes.

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