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

[Blaser]

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

[aceinc]

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

[Blaser]

Others?

[Sonnie]

Sounds like a pretty serious project.

[brucek]

Dual RL-P18 LLT

When you say Dual RL-P18........dual 2 ohm configuration, do you mean two boxes with one D4 driver in each, or two boxes with two D2 drivers in each?

brucek

[Owen Bartley]

Blaser, those are going to be some pretty big boxes, so you may not want to double up the thickness of the front baffle, but I would definitely put some cross bracing in there.

[Blaser]

aceinc wrote:

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. 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!

[Blaser]

brucek wrote:

When you say Dual RL-P18........dual 2 ohm configuration, do you mean two boxes with one D4 driver in each, or two boxes with two D2 drivers in each?

brucek

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

[Blaser]

Owen Bartley wrote:

Blaser, those are going to be some pretty big boxes, so you may not want to double up the thickness of the front baffle, but I would definitely put some cross bracing in there.

Well, being big has the advantage to be asked to contain much less pressure than small sealed enclodures, if we 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.... .

[Blaser]

Can anyone comment about the insulation and best MDF thickness 16, 18 or 22? Are there better alternatives to MDF?

Blaser

[Blaser]

Sonnie wrote:

Sounds like a pretty serious project.

Well would like to be able to hit 125 db or more uncompressed in my room if I wanted to.

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

Blaser

[Sonnie]

It's hard to sound proof the ultra low stuff, but it can be made to sound like distance thunder with thick walls. 125db should be no problem in that small of a room.

[Blaser]

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

Blaser

[brucek]

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



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.


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



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?


brucek

[Blaser]

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 .

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 .

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!!

Blaser

[brucek]

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.

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

[Blaser]

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.

[Blaser]

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

[Blaser]

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.

[Exocer]

One person reported the BKA to be Equal to or superior to a single channel of an Ep2500 @ 4ohms. As it should be.

[Blaser]

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

Blaser

[WillyD]

So are any more powerful options that the EP-2500 for the same price (brand new) approx?

Not really.

[Blaser]

I have read that the bigger the box, the less is the need for stuffing. How true is that?

[Blaser]

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

[Jerm357]

brucek wrote:

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.

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?