RL-p18 with a Linkwitz Transform... good, bad, or ugly?

Brian Bunge wrote:

Mark,

Hummm.... I think .68 isn't too bad. Is that with or without stuffing? I generally prefer something closer to .6 or so. Let me model it again myself this evening and see what I come up with. I think possibly going double-walled but thinner layers internally might get us a little lower.

I'm still debating on whether to go with dual RS 15" HO's or go with a single, higher excursion driver. Whatever I do, I'll probably have to keep cabinet size down so I'll probably re-use my LT circuit and change out the parts values for the specific design. Thankfully I built it so I could swap parts without having to break out the soldering iron.

That is without stuffing. Did you buy a kit for your LT or complete scratch build?
I will play with the dimensions some more when I have time. I have some room to go a little bigger, if need be.

Exocer wrote:

Can you go any larger? If not, then i'd say you'll be ok.

Qtc with about 200 liters (aka 7cubes) is above a tad bit above .707 You are not entering huge enclosure territory and its starting to make more sense to go ported...unless of course you can swing two rl-p 15's which would LOVE a 7-8cube box.

Could you please clear up to me if you meant 2ea rl-p15's in the same 7-8cubes? -- or 2 separate enclosures each with 1driver and 7-8cubes each?

Thank you.

On the subject of installing T-nuts or similar with the bracing as drawn, something like this can be done. Rout out a rectangular shaped hole 1" x 1 1/2" in the brace then drill a hole for what will be the the speaker mounting screw, from the front of the brace. Drill it large enough to handle the type of insert nut you wish to use. Then glue on a scab piece to cover one side of the cutout, it needs to be fairly long(2-3 times as long as the cutout). This will also reinforce the brace to the front baffle and speaker, since you will essentially be bolting all three together.

[Warmon]

NewbieMark wrote:

On the subject of installing T-nuts or similar with the bracing as drawn, something like this can be done.

Looks that would work fine, but I think the inserts would be easier. BTW, that price on the inserts iis for a pak of 25. In my case, I am going to go with Brian's suggestion of just using the pan head screws PE sells since I already have some on hand.

[Brian Bunge]

The 224L looks fine if you stuff the box. With heavy stuffing (1/2 to 1 lb. cubic foot of airspace) the Qtc drops down to the .61 range. I can't emphasize enough how important it is to have a very sturdy box when using drivers of this caliber.

There was a guy on HT Forum way back when the original Tumult was introduced that came up with a little LT circuit using Rod Elliot's PC boards. He provided the unit completely built to forum members with sockets so the essential caps and resistors could be swapped out should you want to change your LT for a different driver/box alignment. I also bought enough parts to build two more for customers I had at the time. I believe one guy in Philly is still using dual Tumults with the LT circuit in his HT along with some very nice Aerial Acoustics speakers.

RE: screws vs. inserts and machine screws, I like the simplicity of using the course thread pan head screws from PE 99% of the time. If you want the cap head screws that require allen wrenchs to install Madisound now sells actual wood screws with that kind of head so you don't have to go the route of t-nuts or inserts just to get that kind of screw anymore. I'll probably buy some for my next speaker project. That is if I can ever sell my big monsters. I can't believe I haven't gotten any takers yet. I know the price sounds high, but if you had to buy something comparable in the retail world they'd be at least $10K.

[Brian Bunge]

Rob D wrote:

Could you please clear up to me if you meant 2ea rl-p15's in the same 7-8cubes? -- or 2 separate enclosures each with 1driver and 7-8cubes each?

Thank you.

A pair of RL-p 15's look good in one 7-8ft^3 enclosure, sealed. I honestly prefer the single 18" though. Sure the dual 15's will give you more output overall, but require roughly twice the power to do so and also have about the same output at 20Hz as the single 18 does. Basically, the single 18" with 1000W gives you a flatter overall frequency response, with an F3 about 10Hz lower than the dual 15's. This means that there's little to no need for EQ to flatten (ie boost) in room response down low.

You could honestly get away with a 1000W plate amp with the RL-p 18 and be golden!

Brian -- Thank you for the good info.

[Brian Bunge]

Any time!

[NewbieMark]

Some threads just won't die...lol

Sorry I haven't posted anymore on this in almost 2 years now. I have had my plate full and just haven't found the time to work on this project, until now. Shortly after getting all the drivers, amp, fbd, wood and whatnots; our second daughter came along and became the taker of all free time... That being said, here are some pics of the box in progress. Warning...This may take a few weeks to complete(I am working on this just whenever I find the time). The dimensions are close to the original drawings on here. The height has changed to 38(original was 36) and depth to 24.75(originally 26.5).

I guess its been so long I no longer have my post count...

[Bent]

Are you still thinking dual 18" in sealed?

I did a twin 15" Rlp sealed at about 8 cubic feet - Adire ADA 1200 plate amp (rebuilt). and applied about 6 dB of boost at 18 hz with a Q of 1 (eq, not enclosure/system) and I really like it.

[Owen Bartley]

Hey, welcome back! I was surprised to see this thread at the top of the list again. And congratulations on the addition to your family as well! The box is looking good, keep at it when you have the time, and keep us updated.

[NewbieMark]

Thanks Owen
I am starting a build thread for this project, since I have some more pictures.