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

31K views 182 replies 19 participants last post by  Blaser 
#1 ·
Final design not completed yet, but I will go for 2 boxes 550-600 L effective, 16 Hz tune, 8" or 10" port, powered by EP 2500, dual 2 ohm configuration.

I am not that good in woodworking, so I am only making the design on paper, but will have the job performed by a carpenter.

I have some variables I would like your advice about:

- MDF or not? If MDF, 16mm, 18mm, or 22 mm? Front baffle will bear both the driver and port.
- Is bracing a must? Never read that anybody made an enclosure without bracing, but I did that for my 4cu ft car sub. and it is rock solid and working very very well, I can even stand on it... no problem. Of course at least the port will be internally supported.
- Insulation: Is it a must? If yes, is 1" fiberglass ok? Should the volume be taken into consideration? I never read someone did...

Your inputs are highly appreciated.

Blaser
 
#2 · (Edited)
Quick note:

Don't get a carpenter to build your speaker cabinets, get a cabinet maker. If you do find a good craftsman, don't be suprised if he takes offense to the term carpenter. They are two totally different trades, and require different skills.

Also don't get a cabinet maker to build your house.

I use a combination of 3/4" (18.75mm?) and 1-1/2" (37.5mm?) MDF for subs. Bracing depends on cabinet size and design. Generally large flat surfaces will resonate at a frequency generated by the sub. On these surfaces bracing in beneficial.

Paul
 
#7 ·
Quick note:

Don't get a carpenter to build your speaker cabinets, get a cabinet maker. If you do find a good craftsman, don't be suprised if he takes offense to the term carpenter. They are two totally different trades, and require different skills.
Well, maybe I used a wrong word, I meant a good craftsman:bigsmile:. Anyway, while I am not skilled with my hands, I will witness all the job, and make sure everything is as per design. Nothing to worry about.

Thank you!
 
#3 ·
Others?
 
#11 ·
Well would like to be able to hit 125 db or more uncompressed in my room if I wanted to.:cunning:

Do you guess what will be my next thread? "Want to soundproof my HT, as the neighbours called the police yesterday":bigsmile:

Blaser
 
#8 ·
Yes, amp will be loaded dual 2 ohm configuration, two boxes, each one will have a single driver D4 (wired in parallele).

I am nevertheless open to suggestions.

Blaser
 
#9 ·
Well, being big has the advantage to be asked to contain much less pressure than small sealed enclodures, if we :reading: still beleive Pressure=Force/Area. But concerning the front baffle, I intend to have a big hole in it 8 or 10", and this will be pretty close to the driver....:dontknow: .
 
#10 ·
Can anyone comment about the insulation and best MDF thickness 16, 18 or 22? Are there better alternatives to MDF?

Blaser
 
#13 ·
The only solution would be a cubicle inside my room I think.... But that's out of topic for the moment.

Blaser
 
#14 ·
When I play with your figures in WinISD I find the RL-P18 D2 model with the 2 ohm coils in series for 4 ohms total and 750 watts per channel from the EP2500 seems to give the most reasonable results (with my limited knowledge).

Much more power than that and the excursion and velocity seem to get a bit too large.

If I use a 550 liter box (19.423 cu.ft) with a 16Hz tune and a 21.27" single flanged 8" port combined with 4 ohms driven from a EP2500 (750watts) I get the following results. Having two boxes would be 6dB more SPL output I suppose.

SPL
Green Oscilloscope Line Text Slope



EXCURSION
Goes a bit over Xmax at full power. Don't think that's greater than Xmech though.
Includes a 1st order 10Hz electronics rolloff filter.
Oscilloscope Green Text Line Slope


AIR VELOCITY
Exceeds the 17 m/sec 5% rule, but is only 7.5% max at full power.
Green Oscilloscope Text Line Slope



I played with the box a bit with a front vent.
Seems like a big box. I'm not too use to using BoxNotes, so it was an experiment for learning.
Don't know if it's realistic. Seems correct.
The only box resonance that seems a concern is a quarter wave one at 86Hz. I wonder how important these resonances are. Takes a lot of playing around to minimize them and still get a sane box.
Anyone else use this program?
Text Font Line Number Screenshot


brucek
 
#15 ·
According to my recent readings, the EP-2500 is likely to produce the 750W you mentioned (Bruce) only with the dual 2 ohm configuration (in real world). I am even wondering if I should reconsider the amp choice:dunno: .

Concerning the port velocity, I will kill this 26m/s limitation by using a 10" port, 80 cm long, but in a 600 L effective enclosure:R .

I wanted to ask about the insulation, what's the material to be used, and where.

I also wondering if carpetting the outside of the box is similar to insulation?

Thanks for your highly appreciated efforts Bruce!!:clap:

Blaser
 
#16 ·
the EP-2500 is likely to produce the 750W you mentioned (Bruce) only with the dual 2 ohm configuration (in real world). I am even wondering if I should reconsider the amp choice
Well, the spec says 750 watts into 4 ohms (which is the resultant Znom of the dual 2 ohm coil driver wired in series). So the one amp in stereo would do both boxes. This doesn't seem like too bad an amp..... good bang for the bucks. Others would cost much more.

Text Line Font Number Parallel


Concerning the port velocity, I will kill this 26m/s limitation by using a 10" port, 80 cm long, but in a 600 L effective enclosure
Yep, that seems to work. I stayed away from the 10" when I was messing around since it would demand the port is mounted vertically because of its long length and I was attempting to get a front mount (for no good reason). There's nothing wrong with a vertical mount (I don't think)....

brucek
 
#25 · (Edited)
Well, the spec says 750 watts into 4 ohms (which is the resultant Znom of the dual 2 ohm coil driver wired in series). So the one amp in stereo would do both boxes. This doesn't seem like too bad an amp..... good bang for the bucks. Others would cost much more.

View attachment 3062


brucek
For subwoofer duties would'int we want to be looking at the 20hz - 20khz rating which is 650watts
instead of the 1khz rating?
 
#17 ·
My boxes should have internal dimensions about 110 cm * 90 cm * 65 cm. The front baffle will be 65 * 90 cm, So I have 110 cm length to place the vent, with 80 cm I can have 25-30 cm for the port to breath. The closest walls to the port will be the side walls about 20 cm from each side.
 
#18 · (Edited)
Yes Bruce, the Ep 2500 is rated 750 into 4 ohms, but I do want a configuration that can get the most out of the subs...(not that I will crank it loud all the time.... I have neighbours, but want to have this options) i.e 1000 watts for each sub min or more. The dual 2 ohm configuration should do this according to the EP-specs specs, but I have read here in this very forum and at AVS that the EP-2500 as a sub amp would not produce that much even at dual 2 ohms configuration. Here's a link
http://www.avsforum.com/avs-vb/showt...&&#post9598876

From the other side, here is my room responce, my room has some cancellations above 70 Hz, and doesn't support frequencies above 40 Hz that much, this is why I am looking for a strong amp. Fortunately the FBQ 2496 is here to manage things below 40 Hz.

Another thing I noted and I am very happy about is that: dual subs along the front wall will cancel the lateral room mode effect, which will let anyone seated have the same bass experience.

I am wondering how the ButtKicker BKA1000-4 compares to the EP-2500!??

Blaser
 

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#19 ·
You can see the effect of the room on the subwoofer responnse here. Of course my sub is brickwall below 30 Hz, but the room is negatively affecting above 65 Hz.
 

Attachments

#21 · (Edited)
So are there any more powerful options than the EP-2500 for the same price (brand new) approx?

Blaser
 
#23 ·
I have read that the bigger the box, the less is the need for stuffing. How true is that?
 
#24 ·
Hi all,

I am about to order the drivers and amp(s), and I need your opinions about 2 things:

1- What's "better": one 2000 W amp for both drivers, or 2000 W amp for each driver, I have both possibilities, but bearing in mind that in case of dual 2000 W amplifiers, the driver will be exceeding its Xmax, but would not bottom out (20 to 30 Hz range).... but the benefit above 40 Hz is appreciated.

2- Tuning frequency: I would like to use 10" port, and the front baffle will support both the driver and the port. The baffle dimension is 90 cm * 65 cm,

I am quite concerned with the 90 cm (height) as:

90 cm - 46 cm (driver) - 25cm (port) = 19 cm (less than port diameter) also some clearance (+ insulation) should be left after the driver (I think about 7-8 cm total) which will only leave about 11 cm from the nearest wall. Is this expected to affect the tuning frequency? How much?

Blaser
 
#27 ·
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.
 
#28 ·
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.

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
 
#29 ·
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?:R

So Is it worth buying dual amps?
 

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#31 · (Edited)
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
 
#33 · (Edited)
Thank you guys! I am about to order the subs in 2 or 3 days:yes: And I have now contacted the box maker to discuss the production steps. We agreed on everything exept the wood type:scratch:

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:jump: And by the way we have agreed that the boxes should be a piece of art!!:T
 
#34 ·
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
 
#35 ·
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!!:T I will brace for sure!! As well as use either available insulation material:)

Any thoughts about wood material?:scratchhead::eek:rder:
 
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