I am now interested in the bass reflex Pi Speakers. I had originally intended to go with my other design, which was actually pretty good, but it costs heaps for what it does. So at the moment I have two JBL 2370A horns and P.Audio PA-D45 compression drivers on them sitting around. I think using them in a Pi Speaker would be very nice :-). The Eminence stuff doesn't cost too much here at all in Australia, so getting an Eminence woofer seems good. Very low distortion and linear response is important to me. I can actually get some JBL 2225 baskets and then recone them with some aftermarket recone kits and it will cost about AU$580 including postage costs for a pair. A pair of new Eminence Delta 15's would be a little less than that, but not by much. Do you think the 2225 will have lower distortion than say, Eminence Delta or Omega series? Which would you reccomend?

I dont want a box massivly large either - actually, I would prefer a tower. This is of course for HiFi use - which out of the Studio, Thermionic, and Theater series would you reccomend?

The Pi Speakers website states 126db maximum SPL for the Theater series 4pi bass reflex using the 15" motor. At this 126db level (very very loud of course!) how are the distortion levels like?

Dont want to go any of the Pi Horn designs - way to big :P.

Whats the external dimensions on the Theater 4pi? I hope its not TOO big! (as you see I've heard a lot of stuff about Pi Speakers sounding very nice, but are massive!).

I realize the bass reflex pi speakers dont use high freq horns.... but I assume they can be used in them anyway with a different crossover (Have not actually built my 1KHz crossover yet, because I planned to build the enclosures first). What sorta crossover would you reccomend then for this setup?

*Gets excited about Pi's*

Thanks!
Adrian

Thanks for th like a 4pi. Specs are as follows:

Fs=42Hz
Re=5ohm
Qms=5.36
Qes=0.28
Qts=0.27
Vas=131L
Mms=125g
Sd=900cm^2
BL=24.2 Tm
Le=2.15mH
Xmax= 5.5mm (length - gap height /2 method).
Pe= 700Wrms (pink noise tested). Has 4" VC.

Its designed for use from 30Hz to 2Khz, but they have reccomended max frequency of 800Hz (probably because of cone breakup modes). The graph provided by them with the driver in a 125L box tuned to 50Hz shows response flat to about 1.5Khz then drops off heaps, and on the other end it shows flat down to about 200Hz then gradually goes to -8db at 50Hz. A better box would give more bass extension of course. There are other models like the 15W1200 with actual reccomended max limit of like 1.8KHz, but have smaller xmax, ~3mm, but other t/s specs essentially pretty similar.

It has two copper rings (DDR, Doudble Demodulating Rings) for decreased harmonic and intermodulation distortion, and also DSS (double silicone spider) for increased linearity. Power compression is 3.4db @ 700w. It has heaps of cooling through channels between the basket and magnetic faceplate, and also more air vents in the back plate. I actually use the 18" 18LW1400
Eighteen Sound driver in a bass reflex box for my sub, and it is very good. Do you think the 15LW1401 or 15W1200 above is suitable for something like the Professional Series 4pi speakers? The great thing is I can get these Eighteen Sound parts for great prices from Active Audio, less than what an Omega costs here in Australia (then again 99% of US-made speakers cost HEAPS more in Australia).

Wouldn't crossing at, for example 1.6KHz present rather severe cone breakup modes on the 15" woofer? Like, I know these high quality parts present less of a problem, but the fact would still remain. So I guess my qustion is, is there an audible artifact of cone breakup near the crossover frequency using these sorts of 15" drivers, or is it not noticable?

BTW: I've heard the word "parallax" being thrown around heaps. What does it actually mean?

Thanks!
Adrian

I also said thanks for the plans, but I guess that didn't show up either :P I hate netscape navigator, so unreliable.

:-)

As for the different woofers. I can attest that even the budget Delta 15 sounds more realistic than my ScanSpeak 8" which is one of the worlds best according to all who covet or own it. You can't really make a bad choice with the 15's. Just bass acording to your taste. But if you like a lot of material with really deep bass the Delta sounds way better than it's graph would let on. My next Pi will use an Omega, I just have to hear this thing. I love the idea that instead or rising respose at breakup range, it just rolls off at crossover. Thats crazy! It is Wayne's favorite Eminence in the midrange and it uses a small box. I will not likely get to own a JBL based Pi for money reasons, but The recone thing can have varying results. It's really down to how good the tech is and with what parts. Hmmm scary.

Good luck with them

Thomas

Thats ok, you dont sound negative at all :-) And yes, if I do decide to go the Pi route, then I'll be using mostly different parts, except for the crossover and JBL horns I guess. But I do think the Eighteen Sound drivers are very good, and I enjoy the 18LW1400 a lot which I have.

As for knowing my stuff... I can say that for subwoofers anyway. Not so much multi-way designs, but hey, I'm gettin there! I've had my share of crappy subs from bad designs of my own, but not anymore (not to say I'm a complete expert of course!). If the Pi speaker I build does sound real bad, then at least theres stuff to be learned :-) But I dont think I could go too wrong choosing parts that I know are good. Besides, I wont cut or purchase a thing until I am certain that it will perform well. I know one person who uses the 15LW1401 from 70-300Hz, William Cowan uses this in with his Unity Horns, and apparantly they work very well too.

Then again... I might indeed go the Eminence Delta route. The 15LW1401 I think costs about AU$420... but the Eminence Delta 15 costs just AU$225. So thats quite a saving, especailly because I'd be needing a pair. Do you think I would be disappointed with the Delta's? I have scanspeak 8's too, so I am looking for an good/noticable improvement over these.

Not sure if I'd go the reconed 2225 way. I know they say specs of aftermarket recones are very similar, but thats just taking the manufactures word for it, which most of the time isn't a good thing to do :P

Thanks!
Adrian

The delta is a great woofer, especially factoring in cost. Since you have a Scan-Speak 8" we share a similar reference. I will say that the delta sounds similar at low volumes, and they both have a full midbass when up against a wall or corner. but since the delta is so much bigger and has to move so little even at high volumes, the phrase that comes to mind is effortless slam. The 8's that I have are the stiff paper woofers so they break up terribly in the mids. It is impossible to compare the two above 500 Hz as the deltas sound great even at crossover. Oh! and believe it or not, the delta is only about 50 % heavier.(not bad when you are 4 times bigger) If I had your sub I might aim for something with less bass than a delta, something more for high output midbass/midrange.

The omega still looks good for you, but I understand about the cost. The woofer you spec'd in another post also looks real strong, but I can't see how they get it in a box larger than 2 cubic feet.(as per BoxPlot) It looks like a great driver to use with your sub crossed around 60 to 90Hz, because it starts rolling off fast at 50 Hz. It looks to be a real high power midbass, and it does seem similar to an omega 15, but lower Q and higher gauss (not a bad thing). Thats a big bad motor. It looks good in a small box too, 2 cubic feet and a port 4" by 3.5" long.

Does Eighteen Sound make a hot 15" with similar specs, but without the double spider? That adds a lot of moving mass and is likely the reason they say to cross at 800. (mass rolloff) Might save you some money too. It isn't really necessary for midbass duty unless you will really pound these things HARD. If your compression driver can do 800 or 1000, it might be ok though. It does appear from the specs and the presence of copper shorting rings that they are doing quality stuff. (just a guess since I havent ever even seen or heard one, but makes sense) If you get the double spider ones, break them in like you are trying to blow them up! I use to sell some double spider car woofers, and most of the customers amps were not capable of moving all that spring tension real well. (I was the service guy so It became my problem, 1 hour on the 1200 watt mono block usually freed them right up)

As for break-up on big drivers, it varies a lot. All drivers break up, It's just where and how bad. Paper is usually friendly and it generally sounds even better than it measures. If you were using kevlar, carbon or glass you would want to cross an 8" about 1000Hz 3rd order. any higher and you would need a notch filter also. Paper self damping, and some drivers like the omega do not show ragged or rising response before mass rolloff. I am not saying that it doesn't have break up, but it has a strong motor and it doesn't have spikey or rising response above 1000Hz (or anwhere else for that matter). How often do you see that? Thats got to tell you something. It seems very controlled in all of the usual behaviors. It's a shame about trade laws and tariffs really. It appears you will have good parts from Eighteen Sound though.

P.S. If you find more info online (graphs, pictures) for eighteen sound let me know. I am not getting much from what I have found.

P.P.S. Take all the Omega stuff with a grain of salt. I have the hots for them right now, and I do not even own any yet. You must admit they have insanely well behaved frequency response in the crossover area compared to just about anything else period.

Let me know how it goes,
Thomas

The 15W1200 has a -3db point of about 85Hz in PiAligned cab, which is really a bit too high I guess. The Omega 15 in a PiAligned cab has a -3db point of 65Hz. Both drivers though are capable of over 120db - the Delta seems the only one with less SPL output. Omega costs AU$570 though..... Unless I provided some equalization in the highpass crossover (sallen key) which would bring down the -3db point a bit, but I dont 'really' want to do this.

Looks like I got a lot of deciding to do, GRR!