Troels TJL3W and L26ROY subwoofers

[vankovich]

Back when I was living in an apartment I built a set of Troels Gravesen's TJL2W ribbon version using Aurum Cantus G2si Ribbon Tweeters as a substitute for the JP1s. These were later modified into the TJL3W by reworking the cabinet and crossovers and adding a driver. The speakers were great for an apartment setting since they were very articulate at relatively low level without unduly disturbing the neighbors. Since I moved into my own house I find that the speakers a bit constrained at higher volumes and not quite up to some program material that contains sustained low frequency notes along with a troublesome node at 50 hz.
After some reading on the web and some consideration, I am thinking about doing the following:
1. Sealing the ports on TJL3W and using a Line Level passive 2nd order high pass filter to roll off the low end somewhere between 125 to 200 hz
2. Build 2 subwoofers using Seas L26ROY drivers and either have each:
a: Sealed with a Linkwitz Transform alignment.
b: Sealed with the dedicated Seas passive radiator ( smaller box)
I have the following equipment at my disposal,
Behringer DEQ2496, Rane ME60 (originally used in other projects and to tame movie soundtracks when living in my apartment. A recently acquired DBX 234 active crossover (I would like to avoid using the high pass)
Dayton EMM-6 measurement mic
Amplifiers: Anthem Statement P2, Emotiva XPA2, also a Music Reference RM9 that requires repair (hum)
Room is 21L x 12W x 8'2"H not including attached kitchen
Ideally I would like to get the sound as close to flat as possible or with a BBC tilt without having to overly rely on electronic manipulation on high pass, be able to play a bit louder and be able to sustain low notes without compression. Although I use this secondary for home theater, my primary concern is music
So Members, is this a viable way to go, and given the choice of which version sub you would build a: or b:, Which one and why?

[vankovich]

Well, Not that I know what I am doing but only in a somewhat vague sense, Why not. I decided to purchase 2 Seas L26ROY drivers (on the way). I decided against the passive radiator / ported version and decided to mount them in a sealed box made of 1" or 0.75" baltic birch plywood measuring roughly 20"H x 12" W x 16" D with 1.5" oak and 1" plywood bracing. I toy with the idea of purchasing a couple of Dayton Audio SWC2-CH 2.0 ft³ Subwoofer Cabinets from Parts Express but found their footprint of 17" x 16" excessive thus prompting me to build my own. Let me be understood here as I have a general knowledge in loudspeaker design but not a specific or specialized one. Being somewhat challenged in math, a lot of what is said is lost in translation. So my first time use of winISD, I looked at the parameters of the L26ROY and found that a box of about 40 liters would flatten the roll off and gain 2db at 30Hz as oppose to the 20.7 liter one, I looked at the phase and group delay and found a gentle slope on both, considering this to be a good thing (having no idea whether or not). If I increase the size of the box beyond 40 liters it was to less and less effect. I suppose this is where the term efficiency comes in effect (please correct me if I am wrong).

The Stuff I Really Don't Know!
The Linkwitz Transform.
My understanding of this is to take the roll off of a driver, measure and equalize this , add gobs of power and wallah! lots of low bass at a trade off of maximum volume.
So can I use a analog equalizer to accomplish this? Perhaps a Rane ME60?
I read that it can easily be done in the digital domain using either a Behringer DEQ2496 or a MiniDSP with the appropriate plugin but I tend to lose it when terms such as bi-quad filters are toss about and enter the fray.
Any shared knowledge or advice would be appreciated as I plunge headlong into the dark.
Its getting late, I'm getting sleepy, more questions to follow,
Cheers, Vanko

[sreten]

Hi,

Your woofer used sealed simply doesn't need an LT, perhaps some
low bass boost passively added, but that all fairly straight forward.

A classic LT takes a driver with higish Q in a box far too small, e.g.
the Peerless SLS10", Qts-0.59, Vas-76L , Fs-33Hz. SL uses this in
a 15.4L box, giving Qbox = 1.57 and Fbox = 75Hz, horrible.

The LT creates at dip towards the peak and boosts bass below that



correcting for a woofer with peaked response (Qp = 1.21) and early roll-off (Fp = 55 Hz), to obtain a response that is 6 dB down at 19 Hz and with Q = 0.5

Here the new target is q=0.5 at 19Hz, so -6dB at 19Hz. note the
loads of bass boost required, near 18dB. for your driver in 40L
there is no peak to cancel, and you only a boost of 6dB at 20Hz
to get very near the aboves target.

rgds, sreten.

[David Gatti]

I'm using a couple of L26ROYs in my subs and couldn't be happier.

The original intention was to put together a line-level passive EQ (between pre and power amp) but as they are located in a corner I havent really found this to be necessary.
I'll probably get around to it some day when I have the time.

[Toaster]

They seem to work well in 40 litres sealed, for example: Clearwave Aria 10. The link to the measurements page on the Clearwave site doesn't seem to work at the moment, but when it was available, the FR used near the floor as with the Aria 10s showed good bass extension even without EQ. As sreten suggests a relatively small amount of EQ would give excellent bass extension in room without too much impact on power handling. Nice drive unit!

[vankovich]

This is very good news indeed, my gratitude to all that responded, my intention is use my DBX234 (24db per octave) for the low pass only, and a passive line level high pass filter for the TJLs. Testing the TJLs full range with pink noise reveals big bump at 50Hz and a deep null (-10db for both speakers averaged at 160Hz). Taking advantage of this null, I would assume this would be the ideal crossover point for the high pass filter or slightly higher. Given that I am going to block the ports on the TJLs, the amp that will them drive them will be
the Anthem P2 with input impedance of 18 Kohms, to employ a second order passive filter would require >50Kohms ideally. I have no idea how to make this work because my electrical knowlege is limited to screwing in the light bulb and knowing batteries are polarized. I can easily solder the parts together but selecting the parts and values leave me mystified. Here is where I really could use some help.
Cheers,
Vanko

[vankovich]

I receive my L26Roy drivers and begun construction of the sub-woofer cabinets. To my pleasant surprise I found a single sheet of 5' x 5' x 1" Baltic Birch Plywood was more than enough material for the 2 sub-woofers. Additionally I purchase (4) 30" x 1.5" x 1.5" red oak stock for the battens. I contracted out the cutting of the panels to a friend at work since I do not have access to a table saw. Otherwise I located, drilled, countersunk, chop sawed, screwed and glued all the pieces together. A shout out is deserved for the SPAX fasteners I used since I removed and reinstalled their screws several times without a single failure. The bracing used was to be as simple and effective as I could make it using the tools I had at hand, I'll add 2 more braces on the front baffle board above and below the woofer. I am awaiting supplies from Parts Express before I begin the finishing process in teak veneer. Overall size of each sub will be just under 20"h x 17"d x 12"w not including feet. I still working on the line level passive high pass filter. I may go the Marchand route with an XM46.
Cheers,
Vankovich

[mayhem13]

If you don't have an amp already to drive these, might i suggest a Behringer iNuke with DSP. You'll be able to near simulate an L/T with the onboard DSP and they'll be enough power to drive the LF boost to flat. Great choice of drivers BTW!

[vankovich]

Hi All ,
I finished the final bracing for the baffle with the remnants of the cut-up baltic birch. Rather then cut holes I cut corners but I am pleased with the results considering the extant of the bracing wasn't in the grand design, more or less just evolved. My Emotive XPA-2 will be the amp driving these,
supplying 500 watts a channel at 4 ohms, the signal will be sent first to my DBX 234 X-over (low pass only) then into a Rane ME 60 equalizer and finally the XPA-2. I still haven't got around to the high pass but would prefer a second order passive line level filter for TJLs, they being driven by the Anthem P2 amps. Any help here would be greatly appreciated. I did putty the screw holes and sanded the box flush with the exception of the front baffles which are awaiting the t-nuts from Parts Express,
funny thing it took me less time to build the boxes then it takes to get parts from "Parts Express". Pics are of the boxes sanded and braced, I'll do a final sand once the baffles are installed.
Cheers, Vanko