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Discussion Starter #1
My friends and I would like to build three or four subs. I currently have 2 RLP-15 4ohm drivers and 2 RLP-15 2ohm drivers. I purchased them awhile ago, but had to put the project on hold.
My original idea was to use the 2 two ohm drivers in a push pull configuration like my current M&K MX350 I like the idea of having two drivers in a space saving configuration. I do not want a 5 foot tall sub.
I am concerned that dual RLP’s may need more cabinet volume & power than I would like.

1. Is this a good idea for a sub based on the drivers I have?
2. What is the smallest cubic volume you would recommend for this sub?
3. Would I be better off just to use the 2 two ohm drivers as mono subs?
4. What would the minimum recommended power be for this configuration? I am leaning towards a plate amp.

I appreciate your help.

Matt
 

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Elite Shackster
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Hi leeug.

At first glance these drivers look ideal for this application. I'll take a look later on when I have a some time and run a model for you, from that I can give you some solid recommendations.

Just a quick point of note. A push/pull sub wont save you much space. It'll be smaller than a dual driver ported sub, but it doesnt work like an isobaric configuration. I like the look of the parameters, and the FS and QTS both are favourable IMO. What is your intended application for these though, and is musicality important to you or are you just after pure low end grunt?

Personally, the push/pull alignment is my favoured of all sub types, and as long as you have good quality drivers and plenty of power they will make an awsome sub.

I'll post back in a few hours.
 

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These are good drivers. You can use them in as little as 3cuft sealed for each driver. the range of 3-4.5 cu ft per drive looks good. They do need quite a bit of power to get the most out of them, but a single EP4000 for both drivers should be nice. A simple and realistically sized build would be opposed 15's, one on each opposite side of a 24" cube enclosure which is about 6.2 cu ft for both drives after displacements. You may need an EQ unit like a DCX2496 to boost the lows up a bit.
 

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Elite Shackster
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OK, Ive run a model of this sub.

IMO, your doing yourself out of performance if you limit yourself to plate amps, but if you do use a plate amp then use the Dayton 1000 watt plate amp and wire the dual 2 ohms in series. The 4 ohms will work in series but your reducing the amount of power on tap from the amp to much IMO, and the 2's will work better.

For a movie focused sub then using the drivers with the Dayton amp in a 250 litre cab will give excellent performance for such a small cabinet. If you want the sub to emphasize upper sub bass slam more (which will make it more musical IMO) then reduce the cabinet size to around 180 litres. You will hear more audible bass but will reduce overall spl capability a little. The good news is that you will have loads of headroom when it comes to power handling and driver excursion, but once you EQ the bottom end in (and it's likely you will need to one way or another) the weak links is going to be the amp. At very high levels I reckon the amp will start to struggle a little, and certainly more than the drivers will.

The larger cab will give the deepest sound characteristic, and offer very powerful and very clean low bass. The smaller cab will give a more audible bass character, and a bit more punch and slam, but wont sound quite as clean (which many people actually prefer).

When it comes to dual opposed vs push pull, I would always go push pull, and if you can then get the best of both worlds and use a dual opposed alignment in a push/pull configuration.
 

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Discussion Starter #5
Music performance is important. I want to go as low as possible without sacrificing on the musicality.
 

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Elite Shackster
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I would go around 200 litres then personally, these will sound excellent IMO. What is the reasoning behind going for push/pull may I ask.
 

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Discussion Starter #7
The reason behind push pull was twofold
1. I thought there would be some space saving
2. I read that the inverted mounting cancels even order harmonics-I am not all clear on the real world result, but my buddy can build any design.
The dual opposed push pull sounds interesting. Are those harder to place? I ask because it would be placed in a corner so no matter how we orientate it one driver would be close to a wall. If that was a problem I could go with two front facing drivers if I can keep the height around 35”, as I understand it the push pull is a better design than just having two front firing drivers.
I would be open to using an external amp on this design. If it was a single driver I would want a plate amp, just for convenience sake.
I appreciate your help.

I just looked at your sub-That is Awesome! I would like to do something like that. I assume with the orientation of the driver that back or downward firing is fine in a corner?
 

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Elite Shackster
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Ive found that in the real world the push/pull configuration offers superior performance. I tried both push pull and dual opposed and the PP just sounds like it has more slam, more authority and a little more effortlessness to the sound. Ive tried this with a friend as well and a further 3rd person tried it with his DIY dual driver sub, both were convinced I wasnt talking rubbish and the push pull is superior to a simple sealed twin driver sub. IMHO, the only way to do a sealed sub is push pull, and I prefer this design above all others. A push pull sub with 2kw will have 6db more max spl capability over a single 1kw single driver sealed sub, and the performance increase Ive experience I guess can only be attributed to the harmonics cancellation effects that are documented. Ive also found the sealed PP sub to be the most accurate Ive heard and I cant really say anything bad about the design myself.

The negative design points of sealed subs still exist, and the way around this for us is to use very high quality drivers and lots of power. The driver certainly look the part, and models incredibly similar to my drivers which Ive been simply amazed by. Power wise, I would certainly use more than a plate amp can offer, especially as you need to power both drivers from a single amp. Add to this you get a lot more power for your money with an external pro amp (which can easily be swapped should you wish to experiment), and you ensuring you maximise VFM.

When it comes to size, there are a couple points you need to take note of. A push pull doesnt reduce required volume per driver. Whatever your drivers volume requirements are, the push pull requires this same amount of volume per driver. A twin driver sealed sub (and a push/pull is a sealed design variant) requires exactly twice the internal volume it would for a single driver design. A sealed sub is generally smaller than a ported on though, so you will enjoy size minimizing here.
The other point of note with a push pull design is that one of the drivers has its voice coil external to the cabinet. In order to keep this part (which no body really wants to look at) hidden from view, you need to increase your cabinets overall dimensions to include this rear part of the driver. This is the reason my subs rear driver is placed where it is. It gives me the volume I needed whilst keeping the external dimension as minimal as possible. A true opposed alignment will inevitably lead to the external cab dims having to be increased if you want to hide the rear driver, otherwise you will be able to see it, so its upto you how you would like to manage that part of the design.

IMO, push pull is certainly the way to go, but if you went with a normal push push dual opposed design the overall cabinet dimensions will be slightly smaller. You really need to figure out which is for you in that respect.

When it comes to position in your room, obviously proximity of a driver to boundaries increases the boundary gain effect, and the lower driver in my sub fires directly into the point at which 2 boundaries meet. Ive found my sub in my room enjoys a cracking amount of low end room gain, that once EQ is applied makes it flat to beyond 10hz right upto reference volume on my amp. If anything I could use slightly better power but what I have right now rocks in my room. Having a driver firing into a boundary or two is IMO actually going to help this sub design couple to the room better, and certainly Ive never found a sub fill my room in such an even way, especially after EQ. In short, this design, in my room, has offered me the best performing and most musical sub Ive ever heard to date, and in a package that isnt obscenely huge. I think you could do a whole lot worse than following this design.

Hope that helps with the basics a little, if there is anything else I can help with just ask.
 

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For music I'd suggest you get some smaller drivers and build a pair of subs and place them below your L-R channel. Just seal and you'll have insane performance.
 

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Discussion Starter #11
I do not have the space for the smaller subs by my fl and fr. This sub will be in front corner, and a little a little larger is ok. It will serve for HT and music.
I was going to ask why you did not go with the 90 degree angle on your drivers like the m&k’s but I think you answered that in your post. You like the sub to backfire into the corner which helps to increase the room gain-good thinking.
I will take your advice and go for the 200 liters with an external pro amp. My friend is the carpenter, so I appreciate any other suggestions.
 

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Elite Shackster
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The reason for the lower drivers orientation was a number of factors for me. I wanted to go opposed but the sub would have been too big. With opposed one driver would have fired into a wall and I wanted to do this to emulate the M&K MX5100sf. The way I have it give me the maximum volume for the cab size, it give me a fairly close to opposed orientation to get some cab vibration cancellation, and it fires into 2 boundaries to couple to the room best. It took a while for me to come to the decision to get it that way, but after a fair bit of brainstorming that was the best of all worlds in my book.

This sub really is very powerful, and very accurate. Its incredibly musical and cracking for HT. With almost all subs Ive heard there has always been one drawback or another, but so far Ive yet to find fault with this design. As always, the more power and better drivers you can use the better results you'll get. I think your drivers will produce excellent results and the ends sub will be the best of all worlds so to speak.
 

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Discussion Starter #13
Moonfly, the guys are itching to build. We are going to do the single driver sealed subs first.
What would you recommend for that? The design goal is similar to the push pull. We want the best sub possible for HT without sacrificing musicality.
We want to build 2 single driver subs. We have two RLP-15 4ohm drivers.
 

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Discussion Starter #15 (Edited)

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Elite Shackster
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The O-audio is a good one, and has the low end boost which is perfect for sealed subs. Ive recently built a single driver sealed sub using this amp and it has no problem using all the driver has to offer.

I would recommend a a 100 litre cabinet, although if you would like a deeper cleaner sound there are no problems going up in size if you decide you can. The good thing about this size cabinet is that the driver shouldnt reach anything like xmax so you have loads of headroom.
 

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Discussion Starter #18
We can go larger on the single driver. What is the optimal cabinet volume that you would recommend?
 

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Elite Shackster
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I would go with the 100 litres recommendation. I like to aim for a QTC slightly under .7 to give a slightly cleaner deeper sound, but without hurting the upper bass impact. If you want to play with it you can then add fibrefill to make it sound a little deeper still and tune it to your taste, but I reckon the 100 litre box size would be spot on.
 
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