Question for SteveCallas or other sub gurus.

**Mattlock** · **07-05-07, 10:32 PM**

Steve (and others)

In my zeal to learn more about DIY subs and eventually building my own, I had pretty much decided on a Mach5Audio IXL 18.4 but I saw Steve's comment in another thread:...

"Ok, the Mach 18 would be able to offer more output with a similar FR, but you'd need to go significantly larger, around 450 liters. Personally, considering that this driver can't do much below 20hz, I don't think the size is justified."

My goal is to get my sub (movies only) down to 14hz range (based on other suggestions) but now questioning this based on the above comment. (unless I am totallying off here)

Here's a little background:

Room Size: 24x14x8.5, shoebox shape in basement. (pics attached)
Current Sub: SVS PB12 (which I really like...this is all I've known...total newbie)

Initial Thoughts: Sonosub with IXL 18.4, tuned to 14hz with EP2500 amp and feedback destroyer. Plenty of room for large sonosub. I do have an adjcent room but not sure that an IB coming from the right of viewing area would make sense (maybe totally wrong here) see pics.

Budget: like to stay under $1000..preferably closer to $750.

Any suggestions/thoughts?

**anidabi** · **07-06-07, 02:39 AM**

Not sure what are you aftar at. You want IB or sonotube sub? With that budjet you wont get not much of an IB I am afraid. Well maeby with ridiculousli cheap smaller drivers, you could.

Anyway, if you want to go with in the sonotube direction with 18" driver, here is a graph with SS RL-p18D4, EE 19Ov.2 and M5A IXL-18.4

If I would be you I'd probably go for the pair of Elemental designs 19Ov.2 drivers. Those drivers need a lot less volume in a box than IXL, but also needs a lot more power per driver(around 850w in that simulation). 19Ov.2 costs 195$, so its even a bit cheaper than IXL.

**vitod** · **07-06-07, 04:01 PM**

You don't need such a huge enclosure. This is based on 350l tuned to 15hz using 800w.

**anidabi** · **07-06-07, 06:01 PM**

Quote:

vitod wrote:

You don't need such a huge enclosure. This is based on 350l tuned to 15hz using 800w.

Okay, I had completely different parameters than they have on the mach 5 audio site. Don't remember where I got them, but it was before the driver was published. Now I have the correct parameters, but those differ a bit from yours. I had to manually set the SPL so that the QTS and QES would be correct, so thats why in my parameters SPL is 2dB lower than yours. One point thought, you have wrong QMS, it should be 5,59.

This simulation is with the correct parameters.

Okay, back to the subject. 8" port is just too long for a 400l enclosure, the port resonance will be way too low, around 160Hz.

**SteveCallas** · **07-06-07, 11:06 PM**

Based on what is available right now, I'd get the SS RLp-18 or FiCar Q18. I still don't have any idea which is the lower distortion driver, but they model very similarly.

650 effective liters, 13-14hz tuning, 8" diameter port, ~1000 watts. Instant success.

**mrogowski** · **07-07-07, 10:51 AM**

Hi Matt,

Check this thread out - about half way down:
http://www.avsforum.com/avs-vb/showthread.php?t=854905

Here's a nearfield measurement for you to ponder - IXL-18.4 in 260l enclosure tuned to 17Hz:

What you see is the driver and port output without any room effects. It wouldn't surprise me if you did the same tests on the drivers that Steve has mentioned, that the results would be similar.

Best,
Mark

**Mattlock** · **07-07-07, 11:21 AM**

Quote:

SteveCallas wrote:

Based on what is available right now, I'd get the SS RLp-18 or FiCar Q18. I still don't have any idea which is the lower distortion driver, but they model very similarly.

650 effective liters, 13-14hz tuning, 8" diameter port, ~1000 watts. Instant success.

Thanks Steve....at 650 liters I may be limited on height...not sure....

**Mattlock** · **07-07-07, 11:24 AM**

Quote:

mrogowski wrote:

Hi Matt,

Check this thread out - about half way down:
http://www.avsforum.com/avs-vb/showthread.php?t=854905

Here's a nearfield measurement for you to ponder - IXL-18.4 in 260l enclosure tuned to 17Hz:

What you see is the driver and port output without any room effects. It wouldn't surprise me if you did the same tests on the drivers that Steve has mentioned, that the results would be similar.

Best,
Mark

thanks Mark for the info.

From a Newbie's point of view how will my experience differ from 12hz (per Steve) to 17hz? (Does my chest feel it more

? ) Just trying to figure it all out. My only reference point is my SBS PB12 which is probably 20hz+.

**mrogowski** · **07-07-07, 11:50 AM**

Well, pictures are always easier to interpret than words so if I have them I use them.

So, take the chart I posted and move the yellow curve from its current peak of 17Hz to 12Hz. Note however, that the curve itself is broad (low Q) and covers a significant range to begin with.

The IXL will do well in a 350 litre cabinet tuned to 14Hz. I think what folks here are saying is that you would get a couple of extra db's at the ultra low frequencies if you went with the SS. Its up to you if that justifies the added cost.

Best,
Mark

**Mattlock** · **07-07-07, 12:54 PM**

Quote:

mrogowski wrote:

Well, pictures are always easier to interpret than words so if I have them I use them.

So, take the chart I posted and move the yellow curve from its current peak of 17Hz to 12Hz. Note however, that the curve itself is broad (low Q) and covers a significant range to begin with.

The IXL will do well in a 350 litre cabinet tuned to 14Hz. I think what folks here are saying is that you would get a couple of extra db's at the ultra low frequencies if you went with the SS. Its up to you if that justifies the added cost.

Best,
Mark

Thanks Mark. I'm just trying to interpret the graph into real life experience....guess I have to just listen to tell.

**SteveCallas** · **07-07-07, 01:14 PM**

A small enclosure with an 18" driver is going to limit you in a few ways - first with low end sensitivity and second with proper porting. A 350 liter enclosure tuned to 14hz using an 8" port will need to be ~50" long, which will very likley result in an audible resonace and make it extremely difficult to actually fit inside the enclosure. I wouldn't recommend using a 6" diameter port for an 18" driver, not unless you want lots of compression down low, in which case you shouldn't even be going ported.

High excursion 18" drivers in ported enclosures with low tunes need LARGE enclosures. If you want to keep it a little smaller, that's fine, just be sure to raise the tune accordingly. The best place to start is to express how large you are actually willing to go - a solid number.

**mrogowski** · **07-07-07, 01:55 PM**

A 6.5" diameter tube can be used in smaller enclosures (smaller, what a word, heh) with little detrimental effects. Tube length isn't such an issue. Making a mock flare on the end would be needed to achieve this though.

You can get 6.5" diameter concrete tubes for cheap - they call them "6+" tubes.

I agree Steve. What size of enclosure are you willing to live with Matt? 500 - 600 litres would be simply awesome if you can live with the girth of the enclosure.

Matt, since you already have a sub, the only way to really focus on your goal would be to run some sine waves thru it. If you can hook your computer up to your system, download a shareware sinewave generater and push that sub into the nether regions - watching the volume of course. Either that, or pull some tone files off the net and burn them to a CDROM.

Here's a link to a shareware sine wave generator:
http://www.nch.com.au/tonegen/index.html

Best,
Mark

**brucek** · **07-07-07, 02:07 PM**

Quote:

shareware sine wave generator

Or you can simply use the signal generator in REW.

brucek

**mrogowski** · **07-07-07, 02:53 PM**

Nice...

**SteveCallas** · **07-07-07, 05:07 PM**

Quote:

mrogowski wrote:

A 6.5" diameter tube can be used in smaller enclosures (smaller, what a word, heh) with little detrimental effects.

A flared 6" diameter port will compress and chuff with high excursion 15" drivers, so you are just asking for plenty of compression with a high excursion 18". What ends up happening is that port output ends up getting stifled and the resulting FR at higher levels becomes very similar to that of a sealed subwoofer. If one is willing to live with that type of a compromise, they may as well just use a 15" driver or seal the 18" driver, cause they aren't able to reap all the benefits of the ported 18". This is truly a case of go big or go home.

**Mattlock** · **07-07-07, 05:09 PM**

Quote:

mrogowski wrote:

A 6.5" diameter tube can be used in smaller enclosures (smaller, what a word, heh) with little detrimental effects. Tube length isn't such an issue. Making a mock flare on the end would be needed to achieve this though.

You can get 6.5" diameter concrete tubes for cheap - they call them "6+" tubes.

I agree Steve. What size of enclosure are you willing to live with Matt? 500 - 600 litres would be simply awesome if you can live with the girth of the enclosure.

Matt, since you already have a sub, the only way to really focus on your goal would be to run some sine waves thru it. If you can hook your computer up to your system, download a shareware sinewave generater and push that sub into the nether regions - watching the volume of course. Either that, or pull some tone files off the net and burn them to a CDROM.

Here's a link to a shareware sine wave generator:
http://www.nch.com.au/tonegen/index.html

Best,
Mark

Mark and Steve,
Here's a pic of my space. If I stay under the surround I am capped at 68 inches however, if I move to the right I can go up 74+ inches but my width is limited to 32 inches unless I can talk my wife into letting me move the lamp.

So with that in mind...what would you recommend? (btw..Steve since the Mach5Audio IXL 18.4 is about half of the Soundsplinter 18 inch..is it still better to get the SP?)

**SteveCallas** · **07-07-07, 05:54 PM**

Quote:

...unless I can talk my wife into letting me move the lamp

Oh man, you're in it deep. Talk the wife into letting you move a lamp? Snap out of it and break the lamp in two pieces over your knee if you so desire.

Quote:

(btw..Steve since the Mach5Audio IXL 18.4 is about half of the Soundsplinter 18 inch..is it still better to get the SP?)

Based on your comments, you'd have no chance of building two such subs, so you need to get the most out of it. The FiCar Q18 and RL-p18 both displace the same amount of air, which is more than the Mach5, and the Q18 is cheaper than the RL-p, so I'd get the Q18.

**Mattlock** · **07-07-07, 06:39 PM**

Quote:

SteveCallas wrote:

Oh man, you're in it deep. Talk the wife into letting you move a lamp? Snap out of it and break the lamp in two pieces over your knee if you so desire.

Based on your comments, you'd have no chance of building two such subs, so you need to get the most out of it. The FiCar Q18 and RL-p18 both displace the same amount of air, which is more than the Mach5, and the Q18 is cheaper than the RL-p, so I'd get the Q18.

Okay....consider the lamp broken !!!!!!!. I'll go with the FiCAR Q18. Where does this put me on a size if I want to get down to 12-13hz range? I'm also thinking of a Behringer EP2500 amp (in case I want to add a 2nd later) and a feedback destroyer (based on others' suggestions)

I saw another post where you recommended "625 effective liters with an 8" port that is 25" long being fed with 800-1000 watts". Sounds like I can get this in my space.

thanks again (I'm slowly learning this stuff)

**mrogowski** · **07-07-07, 07:44 PM**

Quote:

SteveCallas wrote:

A flared 6" diameter port will compress and chuff with high excursion 15" drivers, so you are just asking for plenty of compression with a high excursion 18". What ends up happening is that port output ends up getting stifled and the resulting FR at higher levels becomes very similar to that of a sealed subwoofer. If one is willing to live with that type of a compromise, they may as well just use a 15" driver or seal the 18" driver, cause they aren't able to reap all the benefits of the ported 18". This is truly a case of go big or go home.

Hi Steve,

While I agree with you regarding the chauffing issue, this can be minimized with the right procedures. I disagree with the port compression however. You are basing your theory on maximum power handling of the driver. The driver can reach nowhere near its maximum power handling at such low frequencies. Therefore, no port compression will exist.

Best,
Mark

**mrogowski** · **07-07-07, 07:52 PM**

Quote:

Mattlock wrote:

Okay....consider the lamp broken !!!!!!!. I'll go with the FiCAR Q18. Where does this put me on a size if I want to get down to 12-13hz range? I'm also thinking of a Behringer EP2500 amp (in case I want to add a 2nd later) and a feedback destroyer (based on others' suggestions)

I saw another post where you recommended "625 effective liters with an 8" port that is 25" long being fed with 800-1000 watts". Sounds like I can get this in my space.

thanks again (I'm slowly learning this stuff)

Hi Matt,

I'm sure you will be happy with the Q. Fi churns out some real nice stuff.

Best of luck with your project!

m

**SteveCallas** · **07-07-07, 09:16 PM**

Quote:

mrgowski wrote:

I disagree with the port compression however. You are basing your theory on maximum power handling of the driver. The driver can reach nowhere near its maximum power handling at such low frequencies

I've postulated no theory, I'm speaking of fact. Ilkka has stated that in his testing of the TC 2000 LLT, which is a 15" driver using a 6" diameter port, that port compression appears at elevated levels. We will see this for ourselves when he posts the data. A Q18 or RL-p18 displaces more air than a TC 2000 15", therefore, there will be more compression. Additionally, he didn't have any issues with power handling around tuning, trouble arose above tuning in the 20-30hz region.

A 6" diameter port will limit what a high excursion 18" driver can achieve, threfore, a large enough enclosure must be used to allow for a large enough port.

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