Subwoofer Tests - Fall 2007

**chengbin** · **10-22-07, 08:52 PM**

I doubt the TC has such an extended upper bass

**Sonnie** · **10-22-07, 09:06 PM**

I give up...

**Peter Marcks** · **10-22-07, 09:11 PM**

Quote:

Ilkka wrote:

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.

A few minutes after I originally posted, I looked up the dimensions of the Conquest and did some calculations on my own regarding port tuning. I came to the conclusion that it would be very unlikely for the Conquest to be tuned below 20Hz with both ports open.

At or slightly above a 20Hz tune, it would have 2x the port cross-sectional area vs triple 3.5" ports, and even just a tad more than that vs dual 4" ports.

Still, not quite an LLT though

**mojomike** · **10-22-07, 09:11 PM**

C'mon Ilkka. Confirm our ignorance and give us the answer.

**Ilkka** · **10-22-07, 09:11 PM**

There are partially correct replies but not a fully correct one.

**Ron Temple** · **10-22-07, 09:24 PM**

Just to keep my mind off the lady with Alzheimers that just came to my door...PB13sealed and SB12Plus...total guess.

**noah katz** · **10-22-07, 09:27 PM**

If people are assuming these have the most extended LF response, perhaps that's incorrect; some of the subs may have tioo much and give a bloated low bass.

That would leave whatever subs have the inverse of the response of whatever room Ilkka is talking about, which makes it a **** shoot.

**Peter Marcks** · **10-22-07, 09:27 PM**

Quote:

Ilkka wrote:

There are partially correct replies but not a fully correct one.

I'll take a stab: the top graph is the sealed PB13U, and the bottom is the sealed DIY LMS-5400.

**Ilkka** · **10-22-07, 09:31 PM**

Quote:

Peter Marcks wrote:

I'll take a stab: the top graph is the sealed PB13U, and the bottom is the sealed DIY LMS-5400.

Close but no cigar, as you Americans say.

**jmcomp124** · **10-22-07, 09:33 PM**

Quote:

Ilkka wrote:

I noticed that I haven't posted any teasers yet.

Well here we go. A few frequency responses that I really like (for small/mid-sized rooms). Can you guess which ones they are (they contain a very subtle hint)?

Neither of them has any 'external' EQ.

My guess...
The first graph is the LMS-5400 sealed.
The second is the JLf113.
You said no external EQ, which does not rule out JL's built-in internal EQ.

**Peter Marcks** · **10-22-07, 09:36 PM**

Quote:

Ilkka wrote:

Close but no cigar, as you Americans say.

Sorry, flip what I had said: the top graph is the sealed DIY LMS-5400, and the bottom graph is the sealed PB13U.

**rossandwendy** · **10-22-07, 09:42 PM**

Quote:

Peter Marcks wrote:

A few minutes after I originally posted, I looked up the dimensions of the Conquest and did some calculations on my own regarding port tuning. I came to the conclusion that it would be very unlikely for the Conquest to be tuned below 20Hz with both ports open.

At or slightly above a 20Hz tune, it would have 2x the port cross-sectional area vs triple 3.5" ports, and even just a tad more than that vs dual 4" ports.

Still, not quite an LLT though

According to what Chad Kuypers told me in a recent telephone conversation, the Conquest is tuned to less than 20hz, but I'll leave it to him to share the exact frequency if he so chooses...

Ross

**Ilkka** · **10-22-07, 09:42 PM**

Quote:

Peter Marcks wrote:

Sorry, flip what I had said: the top graph is the sealed DIY LMS-5400, and the bottom graph is the sealed PB13U.

We have a winner! Peter has just won a bag full of bragging rights on all HT forums.

**Peter Marcks** · **10-22-07, 09:45 PM**

HAHA, thank you thank you

Cheers to myself, Ilkka, and the Ferrari driver from Finland who took the world championship crown by 1 point from McLaren

**Ilkka** · **10-22-07, 09:45 PM**

Quote:

rossandwendy wrote:

According to what Chad Kuypers told me in a recent telephone conversation, the Conquest is tuned to less than 20hz, but I'll leave it to him to share the exact frequency if he so chooses...

Ross

Hi Ross,

You have a Conquest? A simple measurement could give us the exact tuning frequency. Do you have a mic/RS meter and know how to use the Room EQ Wizard?

**rossandwendy** · **10-22-07, 09:58 PM**

Quote:

Ilkka wrote:

Hi Ross,

You have a Conquest? A simple measurement could give us the exact tuning frequency. Do you have a mic/RS meter and know how to use the Room EQ Wizard?

Hi Ilkka,

First let me say how much respect I have for the work you do in conducting the subwoofer tests and really appreciate the great info you freely share with the community!

Yes, I do have a Conquest, but have yet to learn or use REW and would need to get an external soundcard for my laptop and probably a decent mic (only have an RS analog meter). Perhaps I will do this when I get back from vacation in earl/mid-November.

Cheers,
Ross

**SteveCallas** · **10-22-07, 10:12 PM**

Quote:

noah wrote:

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)

Nah, I disagree with both statements. If you want anything resembling a flat FR in a small enclosure, it helps to start off with a really low Q so that the EQ needed isn't extreme. A small enclosure won't provide much damping, so you need to get it from the driver's suspesnion. Use a high Q driver in a small sealed enclosure and you've just made it very difficult to achieve any low end linearity in FR. Also, really low Q drivers don't work all that well for low tuned ported designs, as the low end gets too peaky.

**noah katz** · **10-22-07, 10:13 PM**

If you have any way to generate freq, you can get quite close by using a low level and feeling for the lowest woofer excursion while lightly touching it.

**Ilkka** · **10-22-07, 10:15 PM**

Quote:

SteveCallas wrote:

Nah, I disagree with both statements. If you want anything resembling a flat FR in a small enclosure, it helps to start off with a really low Q so that the EQ needed isn't extreme. A small enclosure won't provide much damping, so you need to get it from the driver's suspesnion. Use a high Q driver in a small sealed enclosure and you've just made it very difficult to achieve any low end linearity in FR.

Steve,

You have it backwards. Low Q driver will start to roll off higher and has less deep bass output.

Quote:

Also, really low Q drivers don't work all that well for low tuned ported designs, as the low end gets too peaky.

That's correct.

**noah katz** · **10-22-07, 10:26 PM**

"If you want anything resembling a flat FR in a small enclosure, it helps to start off with a really low Q so that the EQ needed isn't extreme."

Try modeling it and you'll find otherwise. Start with any driver you like, then lower Q by decreasing Mms or increasing BL (which you can do by lowering Qes).

A guess part of what you say is true; in a really small box you'll need to use a high Q driver, but the EQ will need to be extreme becuase it will need to overcome the back EMF of the driver on top of the extra box air stiffness.

"Also, really low Q drivers don't work all that well for low tuned ported designs, as the low end gets too peaky."

Try the same modeling experiment as above and you'll see that as Qts increases so does low end peaking.

**SteveCallas** · **10-22-07, 10:29 PM**

If I'm graphing a TC3k 15" with a .261 Qts in 70 liters (small) to achieve a .537 Qtc, and an old Adire Brahma 15" with a .474 Qts in 70 liters liters to achieve a .818 Qtc, the TC3k sub will have a stronger low end for a given amount of power, as the low end is more sensitive. The Brahma will have a flatter top end.

**Ilkka** · **10-22-07, 10:35 PM**

Quote:

SteveCallas wrote:

If I'm graphing a TC3k 15" with a .261 Qts in 70 liters (small) to achieve a .537 Qtc, and an old Adire Brahma 15" with a .474 Qts in 70 liters liters to achieve a .818 Qtc, the TC3k sub will have a stronger low end for a given amount of power, as the low end is more sensitive. The Brahma will have a flatter top end.

You can't compare two totally different drivers. That's because also other parameters affect the FR. Use the same driver but only change the Qes value. Unibox comes very handy.

**SteveCallas** · **10-22-07, 10:47 PM**

Quote:

noah wrote:

Try modeling it and you'll find otherwise. Start with any driver you like, then lower Q by decreasing Mms or increasing BL (which you can do by lowering Qes).

Hmm, increasing Bl, decreasing Qes, and decreasing Qts seems to round off the top end a little and give me more overall sensitivity.

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