Dual RL-P18 LLT for my 2000 cu ft HT soon

**WillyD** · **05-18-07, 10:32 PM**

Quote:

Jerm357 wrote:

For subwoofer duties would'int we want to be looking at the 20hz - 20khz rating which is 650watts
instead of the 1khz rating?

Of course, and even then that spec is a stretch.

**Blaser** · **05-19-07, 04:31 AM**

Hello guys!

I have decided to use something stronger than the EP. Indeed, the minimum amp. real RMS power will be 1000 W....The question is one for each box or one for both.

**brucek** · **05-19-07, 09:00 AM**

Quote:

For subwoofer duties would'nt we want to be looking at the 20hz - 20khz rating which is 650watts instead of the 1khz rating?

The 650 watt rating is defining the bandwidth over which the total harmonic distortion is at 0.1%
Generally they would define the power bandwidth at the half power points (-3dB) for a given distortion, which would be at 375 watts. But, in this case they have decided to show you that the amp is capable of only losing -0.62dB (-100 watts) over the audio range (20Hz to 20KHz) for a given THD of 0.1%. Seems pretty good to me.

Quote:

Indeed, the minimum amp. real RMS power will be 1000 W....The question is one for each box or one for both.

So, 1000/2 = 500 watts would be fine with you? Let me recommend the EP2500 that can produce 650 watts per channel with 0.1% THD from 20Hz to 20KHz.....

brucek

**Blaser** · **05-19-07, 09:33 AM**

Quote:

brucek wrote:

So, 1000/2 = 500 watts would be fine with you? Let me recommend the EP2500 that can produce 650 watts per channel with 0.1% THD from 20Hz to 20KHz.....

brucek

No, it seems that I was not clear.... sorry!

I mean that I will be using an amp which can output 2000 W. So It can output 1000 W for each box, and this is the optimum for the subs according to Steve's LLT explained article.

But there is a school that says:"more power won't hurt, but can have significant advantages". So if I use dual 2000 W amps (1 for each sub.), the drivers will exceed Xmax (between 20 and 30 Hz) but will not hit Xmec(3.2" peak to peak). But the benefit will be 40 Hz and above. The reason why I am considering this option is that in Ilkka's tests the TC-2000 sub clipped a 2000W amp at 40 Hz:raped:....So what about the RL-p18?

So Is it worth buying dual amps?

**brucek** · **05-19-07, 10:52 AM**

Quote:

So if I use dual 2000 W amps (1 for each sub.),................................
So Is it worth buying dual amps?

4000 watts. Do you have that much power available in wall receptacles?

brucek

**Blaser** · **05-19-07, 12:03 PM**

Quote:

brucek wrote:

4000 watts. Do you have that much power available in wall receptacles?

brucek

Well, 220V * 15A fuse (I have checked) = 3300 W /line from the wall... Is a power factor required to be applied?

EDIT: I have rechecked the electrical pannel and found that the smallest fuse is 15A while any A/C fuse is 32 A....I think this is more than enough!!

Blaser

**05-20-07, 08:59 PM**

I would look at the Crown Xti4000 for a grand. High quality 2x 1200w @ 4ohms would be perfect for that I would think. Just like anything you get what you pay for.

**Blaser** · **05-26-07, 06:31 PM**

Thank you guys! I am about to order the subs in 2 or 3 days

And I have now contacted the box maker to discuss the production steps. We agreed on everything exept the wood type

While I told him MDF will work fine, he informed me few things about polywood (ply-wood):
- Polywood is lighter (front baffle will be made of 3 layers!!), much stronger, cleaner, takes less painting...as he claimed! Also twice as expensive (but don't mind that).

He told me that if I need MDF due to sound issues, so be it (as he doesn't know), but as far as strength, box quality.... weight.... he strongly advises me to use 18 mm polywood (imported from Indonesia).

I need your opinions please to order the enclosures wood.

By the way, the boxes will be CNCed as well as flairs!! No problem

And by the way we have agreed that the boxes should be a piece of art!!

**aceinc** · **05-26-07, 07:48 PM**

Since no one seems to be addressing the stuffing, I'll jump in and provide my two cents.

There is more than one reason to stuff.

The most common reason is to alter the Q of the cabinet. I don't think you're going to need that for this enclosure, as you seem to be letting the cabinet be the size it needs to be. Another reason is to catch & kill high frequencies that might want to escape via the port. Fiberglass is supposed to be one of the better materials for stuffing, but I hate working with it. I prefer polyfill, as it is supposed to be as good as fiberglass and is a lot easier to wok with. I get mine at W*lmart. For a large enclosure such as this you might get "Batting", basically polyfill that will attach nicely to the walls of the cabinet.

One thing to think about with bracing (other than the obvious, strength) using the bracing to discourage standing waves. In a large cabinet such as this you might consider putting your braces assymetrically located, using wider (1"x4" or 1"x6") braces and puting them at angles to the sides of the cabinet.

Paul

**Blaser** · **05-26-07, 09:16 PM**

Quote:

aceinc wrote:

The most common reason is to alter the Q of the cabinet. I don't think you're going to need that for this enclosure, as you seem to be letting the cabinet be the size it needs to be. Another reason is to catch & kill high frequencies that might want to escape via the port. Fiberglass is supposed to be one of the better materials for stuffing, but I hate working with it. I prefer polyfill, as it is supposed to be as good as fiberglass and is a lot easier to wok with. I get mine at W*lmart. For a large enclosure such as this you might get "Batting", basically polyfill that will attach nicely to the walls of the cabinet.

One thing to think about with bracing (other than the obvious, strength) using the bracing to discourage standing waves. In a large cabinet such as this you might consider putting your braces assymetrically located, using wider (1"x4" or 1"x6") braces and puting them at angles to the sides of the cabinet.

Paul

Thank you Paul!!

I will brace for sure!! As well as use either available insulation material

Any thoughts about wood material?

**aceinc** · **05-26-07, 09:45 PM**

Discussing wood material can start a religous war

and don't even start about glues.

My opinion, for what it is worth is I like MDF. If you want to get wild and crazy and you are using double thickness for things like the baffle, use a layer of good plywood laminated to a layer of MDF on the outside. This among other things will give your screws something to bite into.

If you want to deaden the cabinet really well without spending big bucks buy some 1/4" "HardiBacker" and 30# felt (commonly called Tar Paper). Put one layer of 3/4" MDF two layers of 30# felt and 1 layer of HardiBacker together and screw liberally. This will couple additional mass, a second material with different resonances and add damping to the cabinet. It shouldn't cost much but will add a fair amount of work to the endeavour.

**Blaser** · **05-31-07, 07:40 AM**

I ordered the RL-p18 s 2 days ago, and the amp yesterday!!

I should receive them within 10 days. I am already fed-up of

....But, when they come it will be a big

I think my last decision is two boxes around 625L each, 14.5 Hz tine with an 8" flared port for practical considerations.

You can expect my impressions and probably some measurments within 2 weeks

Cheers!

**Blaser** · **06-01-07, 04:32 PM**

Update: Mike confirmed that the drivers were shipped

Thank you Mike for being so prompt in shipping the units as soon as money transfer was performed

I should receive them around June 11th...

For the sake of telling bye bye to my old sub., I performed some listening tests (max SPL at listening position) with music today...

My sub is a Jamo X8 sub, 200W RMS with limiter, 12", (visually) Xmax does not seem to be more than 9mm (maybe even less), 2*3" ports around 40. I blocked a port to lower the tune to be around 34 Hz.

So, I put some good dynamic music (50 cent, Sean Paul, Depeche mode...) and amazingly it could hit 117 db digital RS uncorrected with most of the materials in my 1800 '3 room at listening position (4m) :raped: It seems that I had quite underestimated this sub.. Sound depth was good enough for music, everything was shaking....but I must admit that I never felt the WOTW effects most peoples speak about

Comparing the above with the upgrade that should be performed soon (10 times more power, 2 drivers, 18", competely different Xmax....)

and guess about the results

Can't wait

Edit: I made some more tests and the 117 db was mainly (by ear) between 30-40 Hz (axial room mode), although I have the sub equalized, the room offers lots of headroom at these frequencies.
At higher frequencies where I have dips( above 65Hz) it could only hit 110 db(uncorrected)....Still Great, but I will have some bass traps in the future

**aceinc** · **06-01-07, 05:25 PM**

In case anyone was wondering what the I was prattling on about in an earlier post;

Batting is used in both Quilting, and upholstery. Here is a link to an e-bay sale on some 1-1/4" batting;

http://cgi.ebay.com/Upholstery-Bonde...QQcmdZViewItem

or a more permanent link;

http://storesonline.com/site/490194/...B-CC-1219-ROLL

The advantage of batting is that it can be glued to the walls of the cabinet easily with spray adhesive, and won't bunch up or be pushed around by the air the driver moves.

My suggestion on the bracing is if you are going to brace in the middle of the cabinet with 1"x4" or similar instead of placing the braces parallel to the walls of the cabinet put them at an angle. See the top down view drawing attached. When bracing make the braces a hair bigger than the cabinert width/height so that when you dry fit them they will stay by themselves, but not so big as to distort the walls of the cabinet.

**Blaser** · **06-01-07, 05:43 PM**

Yes, I needed these clarifications!

Thanks Paul!

**Blaser** · **06-01-07, 05:50 PM**

Quote:

aceinc wrote:

My suggestion on the bracing is if you are going to brace in the middle of the cabinet with 1"x4" or similar instead of placing the braces parallel to the walls of the cabinet put them at an angle.

What's the benefit of putting them at an angle?

**aceinc** · **06-01-07, 09:54 PM**

My thoughts are that if braces are needed to reinforce the cabinet and increase the frequency at which the cabinet resonates (as well as reduce the tendency to resonate) placing them as non-symmetrically located as possible and oriented so that they break the cabinet into a number of non rectilinear sections may be beneficial. I can see at least 3 benefits;

1) oddly shaped spaces will discourage standing waves.

2) panels whose braces are assymetrical and oriented "randomly" will tend to have fewer reinforced resonances. In other words if there are multiple panels with the same geometry and bracing they will tend to resonate at the same frequency, reinforcing (amplifying) the resonated sound.

3) reflecting high frequencies at an angle will increase the amount of travel before they will go through the speaker cone, (as opposed to hitting a flat piece of wood and bouncing right back) decreasing their amplitude, and increasing the amount of polyfill they will travel through, reducing their amplitude futher.

These are my ideas, I do not have test data, or other empirical evidence to substantiate them. Perhaps some heavyweights can weigh in on these concepts.

I would not expect a large difference, but with a little effort you may get some benefit.

Paul

**Blaser** · **06-02-07, 03:19 AM**

Paul,

Your thoughts seem very logical... And anyway I think that if the benefits are only minimal, there is no drawback!!

**JimP** · **06-02-07, 05:43 AM**

Regarding standing waves, I have a set of Atlantic Technology speakers (System 8200) where the cabinets have sloped backs that is suppose to help with standing waves.

Would the same design benefit subwoofers?? Any guesses how much slope would be correct??

**Blaser** · **06-02-07, 06:06 AM**

Of course this would help for subs also. I applied such a shape for my car's, but for the monsters I will be building I have to keep the rectangular shape for better utilization of volume and save some space.

I do not think the slope is so critical....remember that all these are hepling factors but not basics IMO...

B Rgds

**planet10** · **06-02-07, 12:56 PM**

Quote:

aceinc wrote:

for what it is worth is I like MDF

I on the other hand, would follow the advice of the cabinet maker, and build the box out of plywood. You want it to be void free (ie Baltic Birch or ApplePly).

Hopefully, without starting a holy-war, i will state my opinion, that MDF is one of the worst materials for building speaker enclosures. I'll put an exclaimation on that by saying that we get MDF for free, yet still go out and buy BB for making boxes.

For a subwoofer this is even more the case. Even staunch defenders of MDF will admit that the extra stiffness of plywood makes it better for subs. Probably the most important characteristic of a sub box is that it not act like a balloon. (another little realized problem with MDF is that it is not air-tight)

The box needs to be braced (and please do not be tempted to put them dead centre -- that is the worst place for them)

The need for stuffing in a sub is debatable, but the rational was covered pretty well in an earlier post. Do take into consideration that it will change the apparent volume of the box, and thus its impact on the box tuning needs to be considered.

dave

**planet10** · **06-02-07, 12:58 PM**

Quote:

JimP wrote:

Regarding standing waves, I have a set of Atlantic Technology speakers (System 8200) where the cabinets have sloped backs that is suppose to help with standing waves.

If you do the math, given the size of even a large sub box, and the frequencies at which it will operate, standing waves are not an issue.

dave

**aceinc** · **06-02-07, 01:25 PM**

Some of the cabinets that are built based on the LLT design defined elsewhere on this site can have dimensions exceeding 5'. Wouldn't this start causing problems around 113hz? Not out of the range of some subs.

Cost is one reason for some of us to be involved in this "hobby" and the difference between 13 ply, void-free BB and MDF can make or break a project.

Regarding MDF being airtight, I use what I believe to be a simple, effective, and low cost option to resolve this;

After the cabinet is built, but before finishing the outside I slop a thick coat or two of latex paint on the inside of the cabinet. To maximize my funds, I only buy "oops" paint from the local Home Depot/Lowes at $5.00 per gallon. I try to get semi-gloss, as this tends to be quite rubbery when dry, my current cabinets that I am building using a design from planet10's Frugal-horn.com web site, have a rather garish purple interior.

Paul

**brucek** · **06-02-07, 01:30 PM**

Quote:

but before finishing the outside I slop a thick coat or two of latex paint on the inside of the cabinet

Doesn't latex breath though? I wonder if an oil based varnish or the like would be better? Don't really know.

brucek

**Blaser** · **06-02-07, 03:41 PM**

Quote:

planet10 wrote:

The box needs to be braced (and please do not be tempted to put them dead centre -- that is the worst place for them)

Thank you for your post

, I just need some clarifications pls
What do you mean by dead center?

Quote:

The need for stuffing in a sub is debatable.

How? Pls elaborate, Do you mean that not stuffing would be acceptable?

Quote:

Do take into consideration that it will change the apparent volume of the box, and thus its impact on the box tuning needs to be considered.
dave

According to the modelling softwares, lining the walls does not change the tune but slightly the FR...Anything wrong with it?

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