RL-p18 Sonotube thoughts...

**bnw** · **07-24-07, 09:25 PM**

Hi guys,
First post over here. I'm currently looking at doing the RL-p18 in a
27 cu.ft. sonotube (30"x 66") less port and driver volume. I might do two since I have the extra piece of tubing, with both driven by an EP2500.
What are the guru's thoughts on tuning or the volume for that matter. -Steve

**SteveCallas** · **07-24-07, 09:46 PM**

~650 liters and a ~13hz tune using an 8" port is golden. That would be 28" tube that is 70" tall - 30" would work, but just make sure you can comfortably fit it through your door...seriously.

**Sonnie** · **07-24-07, 09:54 PM**

You might need some more structural support for your home as well...

**bnw** · **07-24-07, 09:59 PM**

Hi Steve,
Your pics were my inspiration for this project.
Are you saying this driver doesn't want more than a 650l enclosure? I'm totally new to this and WinISD is still leaving alot of questions. Likewise as to go with the D2 or D4 and how it relates to if I go with dual towers, which right now I'm leaning towards. For duals, should I be looking at a different driver? (IXL 18.4, fi Q18)

**bnw** · **07-24-07, 10:02 PM**

That hasn't gone without thought...

**SteveCallas** · **07-24-07, 11:23 PM**

Sure, you can go with more volume and a lower tune if you want, or vice versa, but I find ~650 liters and ~13hz tune to be the best balance of FR, headroom, extension, an low end protection. It's tuned low enough that you will get the earth shaking lows while still having enough headroom to give you reference level playback capability in room from nearly 10hz on up with just on driver and a decent amp. The natural FR has proven itself to mesh very well with typical room gain. Also, on the tune again, it's low enough not to be called upon with music playback, but it really delivers the goods for movies - just what one would hope for, very versatile. Whether using the Avalanche 18, FiCar Q18, or the RL-p18, the ~650 liter ~13hz tune design results in the most balanced single driver subwoofer design I've yet to see.

I would define your budget first, then pick out the drivers.

**bnw** · **07-25-07, 11:01 AM**

Thanks for the insight Steve. My budget was around $1000, but its more about not having ANY regrets. Certainly $1500 would not kill me. I'm all about quality. The sub will integrate with my B&W DM605 S2's with built in powered subs. So with that said, would the RL-p18 still be your driver of choice? Also I've seen chatter about some othe Berhringer product that provides protection from overdriving. Is this what you mean by "low end protection"? What would my port legths be with the 650l or 750l tune?

Alot of questions, I know. And REALLY appreciate everyones help while I get my legs under me. -Steve

**brucek** · **07-25-07, 02:40 PM**

Quote:

What would my port lengths be with the 650l or 750l tune?

Using an SS RL-P18 D2 with the coils in series for 4 ohms.

With a 13Hz tune........

650 litre with 8" port = 28.92"
700 litre with 8" port = 26.44"
750 litre with 8" port = 24.29"

Here's WinISD with 700 liters at 13Hz with an 8" port, one end flared at 26.44".
I added an electronics 1st orfder rolloff highpass at 10Hz and 1000 watts to produce 120dBSPL...

I don't know, the velocity seems a bit high, but a lot of the builds of these LLT's seem to have over the allowed 5% and 7% speed of sound maximums, but no one complains about any port noise. I guess this is because of the large ports.... steve?

Transfer.jpg
Excursion.jpg
Air Velocity.jpg

brucek

**Jerm357** · **07-25-07, 02:51 PM**

Can you post up the SPL graph at 1000w?

**brucek** · **07-25-07, 03:10 PM**

1000 watts at the driver......

Remember there's a 1st order highpass on this at 10Hz....... pretty typical.

If you add room gain to this, I think that's a pretty perfect response....

SPL.jpg

brucek

**bnw** · **07-25-07, 03:18 PM**

So how do I prevent that over excursion below what looks to be about 12Hz?

**brucek** · **07-25-07, 03:42 PM**

Well, remember that's the velocity at 11.8Hz with 1000 watts. Not likely to happen.....

The graphs show you don't exceed 7% = ~23m/sec speed until 600 watts at 11Hz....

Steve will pipe in shortly to straighten this out better for you.

brucek

**Mattlock** · **07-25-07, 11:08 PM**

Quote:

SteveCallas wrote:

~650 liters and a ~13hz tune using an 8" port is golden. That would be 28" tube that is 70" tall - 30" would work, but just make sure you can comfortably fit it through your door...seriously.

I'm also looking at a 650 liter setup probably with the Q18. Locally I can get 24 or 30 inch tubes. Going with 30 inch what height am I looking at?

thx

**bnw** · **07-26-07, 06:59 AM**

Looks like 60 1/2" with a 1" recess on the top and bottom for the end caps would be almost exactly 650 liters

**bnw** · **07-26-07, 10:56 AM**

Quote:

brucek wrote:

Well, remember that's the velocity at 11.8Hz with 1000 watts. Not likely to happen.....

The graphs show you don't exceed 7% = ~23m/sec speed until 600 watts at 11Hz....

Steve will pipe in shortly to straighten this out better for you.

brucek

I'm talking about excursion, not port velocity. Am I mis-understanding?

**bnw** · **07-28-07, 07:43 AM**

??? guess its vacation week...

**SteveCallas** · **07-28-07, 11:20 AM**

The matter of LLT excursion below tuning has been a hot topic for some time - mainly because people who don't have any experience with one have creative imaginations

(by no means you, I am referring to old debates on other forums). Simply stated, nobody who has a built a LLT has ever experienced any bottoming due to below tuning playback of real material. You ca find a detailed explanation why in my LLT Explained thread, but to sum it up, most electronics start roling off in the teens or single digits. Add up the rolloff of your dvd player, processor, amplifier, and an EQ unit if you have one in the chain, and you gain protection from the lowest of lows. Additionally, the levels required for your to reach overexcursion at such low frequencies are rarely if ever reached. Also, xmax is a parameter in which the excursion is essentially "behaved", but there is also xmech, the physcial travel limits of the suspension, and in high excursion drivers, it can be quite large, 40mm+. Lastly, if Ilkka's experience translates well to other high excursion drivers, then the suspension itself will gradually start to resist extreme movement beyond xmax. Combine all these things and a few others, and you are safe from having to worry about bottoming a LLT below tuning with actual material.

If you keep increasing the level on somethng like a 5hz sine wave though, then yeah, you will likely bottom and damage your driver assuming you don't fry the voice coil first.

Ok, budget of $1000-$1500. Subtract $300-$400 to start with for the amp, and another $200 for enclosure materials. Assuming you have the space for it, you should be able to go with your choice of dual RL-p18s, Q18s, or, if you want to save the most, Mach5 IXL18s.

**bnw** · **07-28-07, 03:03 PM**

Thanks for relieving my concerns Steve. As for choice of driver,
HOW COULD I NOT support SoundSplinter with all they do here?
Still not clear if I should go D2 or D4 assuming the EP2500. I have multiple sub outs on my prepro so, I was thinking i could either do separate channels and a pair of D2's or Bridged mono and D4's in parallel or D2's in series. This is where I'm really struggling to understand.

**brucek** · **07-28-07, 03:49 PM**

I'm not a fan of a 2 ohm load. I prefer to see a sub have a 4 ohm load.

This means the D2 with the two coils in series.

This means with one EP2500, you can drive one channel to each sub for 750 watts each, and/or eventually get another EP2500 and put each amp in bridged to drive each 4 ohm sub with 2400 watts.

But that's just my thoughts on it - others may disagree.

brucek

**bnw** · **07-29-07, 08:49 AM**

Hi Bruce, thanks for explaing that, and if I'm now getting my arms around this resistance thing, one more option would be to do the two D4's in parallel, right?
I see there's a difference in specs between the D2 & D4. Any advantage to either.
I guess getting D2's, I can always just use the independently and still have that 4ohm load, which I can't with the D4

**Blaser** · **07-29-07, 09:57 AM**

Bnw,

IMO the choice on the driver's configuration will depend on how many amps you want to use. 1 or 2. Also, there is no noticeable difference between the D2 and D4 drivers, the difference in specs should not disturb you that much, they model pretty identical.

My advice to you (I am an owner of Dual RL-P18, LLT) is to get the max of any amp you will get (i.e use them bridged), "you can never have enough headroom". You may use one of the following configurations:

- 1 amp.: 2 D4 drivers to be connected to represent an 4 ohm bridged load to the amp.

- 2 amps: 2 D2 drivers to be connected to represent 4 ohm bridged load/speaker to each amp. (best configuration if you use the ep2500 amp.

If you use 8" ports tuned low enough....never think about shuffing or compression

you will be too busy and afraid about your sofa moving and everything rattling so loudly....and that is if you dare to fire them at 120+ levels

But you will never hear anything coming from the ports. I even ask myself if the ports are really contributing a lot on program material

...each time a put my hand in front of them....no air at all

FYI, I am experiencing sight blur (believe me) if I send more than 122 db or so...and I don't even think about air speed or excursion at that moment

Good luck!

**bnw** · **07-29-07, 10:32 AM**

Hi Blazer,
When I think how insane this all is, I'm tempted to say "Only In America", but the I see how this community has members in Egypt, Austrailia, etc. What a cool way to come together.

So, sorry to be so thick. Can I do two D2's with one amp for now (separate channels) then go bridged mono when/if I get a second amp?

**brucek** · **07-29-07, 10:42 AM**

Quote:

So, sorry to be so thick. Can I do two D2's with one amp for now (separate channels) then go bridged mono when/if I get a second amp?

That was my suggestion above - it gives you more options. Each sub enclosure will stand alone at 4 ohms total (using a D2 in each enclosure with the voice coils in series). You can use a stereo amp with each channel feeding a 4 ohm sub.

Then later you can add a second amp and have both amps bridged to 4 ohms, each feeding its own 4 ohm sub...

brucek

**Blaser** · **07-29-07, 10:52 AM**

Quote:

brucek wrote:

That was my suggestion above - it gives you more options. Each sub enclosure will stand alone at 4 ohms total (using a D2 in each enclosure with the voice coils in series). You can use a stereo amp with each channel feeding a 4 ohm sub.

Then later you can add a second amp and have both amps bridged to 4 ohms, each feeding its own 4 ohm sub...

brucek

Yes Brucek

Agree with you! if he wants to start with a single amp with the propability to add a second one later

**Blaser** · **07-29-07, 10:58 AM**

Quote:

bnw wrote:

When I think how insane this all is, I'm tempted to say "Only In America", but the I see how this community has members in Egypt, Austrailia, etc. What a cool way to come together.

Yes HTS is great...and Egypt has other things than just the pyramids

You propably forgot to mention Finland and Danemark

Quote:

So, sorry to be so thick. Can I do two D2's with one amp for now (separate channels) then go bridged mono when/if I get a second amp?

This is blessed by Brucek, and therefore by me as well

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