LLT driver recommendation and modeling...

[Sonnie]

Now that I have sold everything in my dedicated HT and will now have the HT sharing the great room, I figure why not start a small project and build an LLT for the great room.

Currently I am running the Ascend Acoustics Sierra 1's across the front. They are good down to about 60-80Hz. The Onkyo 805 will feed an EP2500. Why did I sell it? That cost me about $50... Unless I don't need that much power, then I could save about $50 and go with an EP1500.




The real key will be WAF... I will have to hide this behind our corner cabinet. She'll have a big enough fit the first time she hears it, but not seeing it will ease the pain some.

The room is very large, 18.5' x 20' x 10'... with very large openings into the remainder of the house.

Here's what I have to work with...







The board you see in the floor is the maximum size I have to work with. I can slide that into the space and shut the door without any sides touching anything in that space. The top is open into the room.

The board is 17" x 22". I can go up to 80" tall, which would ultimately give me up to 13 cubic feet or 368 liters... less internal bracing and port/driver displacement.

The question is whether to go with a 15" driver or an 18" driver. If I go with the 15", I have the choice of firing down or back. The 18" driver would obviously have to be fired back on the 22" back side.

I still have the two 6" PVC pipes that came out of the Behemoth sub... they are about 35" long each.

So... what would you professionals recommend?

[atledreier]

Sonnie wrote:

So... what would you professionals recommend?

I recommend you start padding all that clutter in the cabinet, that will make some infernal racket once you put ANY kind of woofer behind it!

Other than that... Well, with 700-ish effective liters you could probably get away with dual 15"...

[Ricci]

Sonnie,
I'm calculating that you have about 13.5 cu ft to work with. I multiplied 15x20x78 for internal volume. I figured that the rest would be the enclosure walls, port, bracing and driver displacement. If i multiply 17x22x80 I get 17.3 cu ft.

If you are set on a ported set-up it looks like 1 18" or possibly 2 15's. If you went sealed you could maybe squeeze 4 15's, or 2 18's in there.

[Sonnie]

atledreier wrote:

I recommend you start padding all that clutter in the cabinet, that will make some infernal racket once you put ANY kind of woofer behind it!

Very good point. We'll have to glue felt to the bottom of all of the breakable items and add a cushion between the glass shelves and the shelf brackets. Of course it might not be as bad as I am thinking... it will not be touching the cabinet. Everything in the room will probably rattle.

Ricci wrote:

Sonnie,
I'm calculating that you have about 13.5 cu ft to work with. I multiplied 15x20x78 for internal volume. I figured that the rest would be the enclosure walls, port, bracing and driver displacement. If i multiply 17x22x80 I get 17.3 cu ft.

If you are set on a ported set-up it looks like 1 18" or possibly 2 15's. If you went sealed you could maybe squeeze 4 15's, or 2 18's in there.

You are so right... I musta had something in my calculator. 13^ft. or about 360 liters. I definitely want to do ported... probably tuned to about 13-14Hz if possible. I want this to be reasonably priced, so probably just one 15 or one 18 will work for me. I would be nice to try the 18.

Can one of you guys... or someone model an 18 from Fi, CSS and Mach5? Thanks!

[tenzip]

Are you restricting yourself to a square/rectangular shape for a reason? Have you considered a trapezoid that would allow you more ft^3, and fill the space more? I'm thinking like this: ( ascii art)

      _______
    /            |
  /              |
/__________|

It would be a little more complicated to construct, due to the != 90 degree angles, but would let you squeeze out some more internal space, if you need it. You could also get a little more space on the top surface for ports and/or drivers.

And like maverick said, get some kind of removable adhesive for all the knick-knacks. Stick those suckers down, or you'll have a rattle convention. (And your wife wouldn't appreciate them vibrating off the shelf, I'd imagine.)

[SteveCallas]

Sonnie, based on your pictures, it seems that only either the driver or port would be able to fire obstruction free into the main listening area, but not both. It's difficult to say what might happen to your FR with either the port or driver having to fire into that semi enclosed space. If faced with those options, I would definitely mount the driver at the top to get the flattest FR in the more audible ranges. Then I would mount the port at an angle so that it points out into the rest of the cabinet, as close to the top as you can manage without crowding the driver's vent. By doing this, I think you could minimize potential strange behavior - see attached for an idea.

Is there any way you could build it so that the baffle extends over the cabinet with the driver front firing into the room? Or would that cross the WAF line? See attached #2.

[Sonnie]

tenzip wrote:

Are you restricting yourself to a square/rectangular shape for a reason? Have you considered a trapezoid that would allow you more ft^3, and fill the space more? I'm thinking like this: ( ascii art)

      _______
    /            |
  /              |
/__________|

It would be a little more complicated to construct, due to the != 90 degree angles, but would let you squeeze out some more internal space, if you need it. You could also get a little more space on the top surface for ports and/or drivers.

If I need the extra volume, this is not a problem, I can do that.

SteveCallas wrote:

Sonnie, based on your pictures, it seems that only either the driver or port would be able to fire obstruction free into the main listening area, but not both. It's difficult to say what might happen to your FR with either the port or driver having to fire into that semi enclosed space. If faced with those options, I would definitely mount the driver at the top to get the flattest FR in the more audible ranges. Then I would mount the port at an angle so that it points out into the rest of the cabinet, as close to the top as you can manage without crowding the driver's vent. By doing this, I think you could minimize potential strange behavior - see attached for an idea.

Is there any way you could build it so that the baffle extends over the cabinet with the driver front firing into the room? Or would that cross the WAF line? See attached #2.

Yeah... no doubt #1 would have to work, but that limits me to a 15" driver. I would think if bass is omni-directional, it would not matter if I just mounted it up high on the side would it?

[Sonnie]

I could build the trapezoid type enclosure and it would possibly give enough room to do the 18 in the top, but the door opening is only 18". I need to build the box and slide it through the door opening... and I would like to be able to easily remove it if necessary, so I am stuck with 17" max outside width on two opposing sides.

[Sonnie]

I might get away with secretly getting some white speaker grill cloth and open up the bottom back of the cabinet into the room, covering the opening with the white grill cloth. I could probably do the bottom 24" or so and it would not be that noticeable.



then I could do the 18" down low and face it towards the wall or out into the room. I could probably remove the glass door on the front of that cabinet without the wife realizing it right away. None of the other cabinets have glass doors anyway.

[tenzip]

Coffee table sub?

[Sonnie]

No power and signal connections... concrete floor. Behind the cabinet is my only option at this point.

[SteveCallas]

Sonnie wrote:

I would think if bass is omni-directional, it would not matter if I just mounted it up high on the side would it?

Right, but with that area behind the cabinet being so enclosed, the driver or port could partially couple to the air in that space. It may even result in some swooshing noises in a worst case scenario. Prepare for the worst, hope for the best

[Mike P.]

Here's some modeling with the various subs you're considering. All models are based on the EP2500 for input power. Cabinet size is 13 cu.ft. to utilize the available space.

Spl graph shown.

Green IXL-18 13 cu.ft tuned to 15 hz. SS filter at 14 hz. 800 watts input power.
Light blue Fi Q18 13 cu.ft tuned to 15 hz. SS filter at 14hz. 1000 watts input power.
Pink 2x IXL-15 13 cu.ft tuned to 15 hz. SS filter at 14 hz. 1300 watts input power.
Blue SXD-15 13 cu.ft. tuned to 15 hz. SS filter at 14 hz. 1000 watts input power.

[Ricci]

I did some modeling too and I personally think the best option is 2 SDX15's in 13.5 ft tuned to 15.5 or 16hz with one 8"port. They would take every drop of power that an EP2500 has and ask for more above tune. I don't know how easy it will be to fit the port and 2 15" drivers though. You've got a challenging build ahead!

[Sonnie]

I need to use the 6" PVC I have now. I have a pair at 35" long, which can be cut to the appropriate length.

Cost will determine whether I can go with a pair of 15's or one 18.

[Bob_99]

Any thought to doing it over the cabinet? It wouldn't look too bad if done correctly.

IMO.

Bob

[Sonnie]

Yeah... I could probably make it look okay for me, but getting that past the wife might be a very tall challenge. I would rather keep it simple, although I have not completely discounted building two subs, one behind the corner cabinet and another finished box in the rear corner of the room, where I could get a speaker wire to it via the surround speaker wire path. It really depends on the cost of all the drivers though.

[Sonnie]

Ricci wrote:

I did some modeling too and I personally think the best option is 2 SDX15's in 13.5 ft tuned to 15.5 or 16hz with one 8"port. They would take every drop of power that an EP2500 has and ask for more above tune. I don't know how easy it will be to fit the port and 2 15" drivers though. You've got a challenging build ahead!

Did you model those 15's against dual IXL-15's and dual Fi Q-15's.

Also... when modeling different drivers, are not different volumes, port sizes, etc, going to cause each one to perform their best? IOW's, is it not better to compare one at its optimal box volume + port dimensions and power vs. another drivers optimal parameters?

[thxgoon]

Sonnie wrote:

IOW's, is it not better to compare one at its optimal box volume + port dimensions and power vs. another drivers optimal parameters?

Yes, but in your case the volume is fixed. The port length can be changed to find the optimum tuning, though by Mike's graphs they all look pretty good at 15hz. My favorite amongst those is the IXL18.

I really like the idea of making this sub stealthy, nobody will ever know where the bass is coming from. It looks like there is a small area just to the left, could your port fit in there allowing you to put both the port and woofer up top?

[Ricci]

I did compare most of the same ones that Mike did with roughly the same results. The dual SDX's had the most overhead left available, and a nice looking response. I think -6db at 16hz. Dual Q15's had a bit worse looking response than the SDX's and a bit less headroom. They would like bigger enclosures. Dual IXL15's had a nice looking response and more headroom than the 18's(If the SDX's cost too much this would be my #2 pick)The IXL18 had the best looking response imop, but could be over driven by the amp. The Q18 will have more max output than the IXL, but the FR isn't as purdy.

I also modeled a pair of the $155 Mach5 MJ18M's for fun and they weren't too bad either. Ported to 16 or 17hz in 13.5ft. They could use a bigger box but the response is smooth and just rolls off a little more than usual on the lowend. More potential output than 1 IXL18 or Q18.

[Sonnie]

Thanks for that additional info Josh.

thxgoon wrote:

Yes, but in your case the volume is fixed. The port length can be changed to find the optimum tuning, though by Mike's graphs they all look pretty good at 15hz. My favorite amongst those is the IXL18.

I really like the idea of making this sub stealthy, nobody will ever know where the bass is coming from. It looks like there is a small area just to the left, could your port fit in there allowing you to put both the port and woofer up top?

I am not sure I follow you. Why is the volume fixed? Do you mean that max volume is 13^3 and that it cannot go larger?

I also am not sure about the small area part you are referring to. I pretty much have a 17" x 22" rectangle area to work with behind that cabinet. I could do a trapezoid at mentioned, but there is really no benefit. Either way I will not be able to install an 18" in the top firing up. If I go with one 15, I could fire it up and possibly have room for the port firing up as well. But I would rather do one 18 in one box and a pair of 15's in another, if I end up doing two boxes.

[T_trip]

Did you ever decide on a final design? I have similar space constaints and was wondering what you decided on.

Thanks,
Tommy

[Sonnie]

Hi Tommy...

No... I have not decided yet. I got more interested in doing my car and kind of put this on the back burner for a while. I will eventually do something though.

I have just learned how to use WinISD... so now I am beginning to understand this modeling a little better. It will help me with the decision.

[F1 fan]

I haven't been around here lately but what happened to your ML's and monster sub?

[Sonnie]

See... you have been a bad feller...

All gone... gone, gone, gone! I sold everything and tore out the HT in the garage where my car is now parked.

We just have a great room system now.