Flex Your PCD Mettle:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

50dB down across the spectrum . . . both show very good linearity. And 1% distortion below 100Hz is really nice.

[Zilch]

Re: Flex Your PCD Mettle:

50dB down across the spectrum . . . both show very good linearity. And 1% distortion below 100Hz is really nice.

As you suggested earlier, the room is clearly an element in these distortion measurements; it's no coincidence that the peaks in the LF occur precisely at the room mode nulls here.

[Looks like Deluxe could benefit from the 2 kHz notch filter, as well.... ]

[Pete Schumacher]

Re: Flex Your PCD Mettle:

As you suggested earlier, the room is clearly an element in these distortion measurements; it's no coincidence that the peaks in the LF occur precisely at the room mode nulls here.

[Looks like Deluxe could benefit from the 2 kHz notch filter, as well.... ]

Well, the difference is that the Deluxe version has a lower sensitivity, and benefits from the low shunt resistance keeping the impedance peaks under control. The resonance filter would make almost no difference.

The larger shunt resistor on the higher sensitivity version results in more impedance variation, and benefits from smoothing the impedance a lot more.

[coctostan]

Re: Flex Your PCD Mettle:

Tweeter level will need to come up at least 4dB. That means dramatic changes to values to keep the same transfer function, only raised. Flattening the woofer transfer function is another matter. Changes there are even more substantial.

I'm going to suggest a starting point for you. I used Zilch's plots, but ignored everything below the baffle step.

Here's the PCD sim, and it looks really nice, to me anyway. In the top plot, you see driver responses, power response (waveguide not included), and the tweeter reverse null. It seems the forward axis is straight ahead on this one, and there's nothing wrong with that I would assume.

I gotta say you are too damn nice. Thank you very much. I will use that as a starting point. I'm sure it would be great as is.

[900SS]

Re: Flex Your PCD Mettle:

Having listened to 2 of the 3 woofers I would go with the LF in the trap box alignment if I did not already own the HO. That being said my trap boxes have arrived and I am actively looking for simple way to bring the volume to about 2.2 cu ft.

Recognize first that these have been whirlwind rounds of loudspeaker design with no opportunity for extended quality listening anywhere outside ZilchLab.

The highs are the same, because they are all mated with the same compression driver/waveguide combination in the same cabinets crossed flat within a few dB in the same region.

The mids are very similar and a step up in clarity and dynamics, in general, from the lower-efficiency drivers with which I am more familiar in the EconoWave format. I'd certainly have to do more rigorous A/B listening to distinguish among these three in this respect, and against others to ascertain whether there is, in fact, an Eminence sound character, and what that might be.

On the low end, there are easily discernable differences, with the caveat that I am using all of them in this same small (1.6 cuft) vented alignment tuned to 30 Hz, and paying no attention whatsoever to how each might be optimized. All are being played under the same conditions, on the wide test stand you see in the pics, at least 1m away from all boundaries, 2m to the side and rear, typical.

Given these conditions, I am hearing what Dennis's models suggest, basically:

LF will play extended bass with EQ assist, and would probably not need that with boundary reinforcement as a full-range system without sub(s). HO and DL try but can't pull it off, and need subs or a more optimum low frequency alignment as others have suggested above. Recognizing that most home theater installations incorporate subs, either of the latter two would be well adapted to this use.

Also significant in the results thus far is that in this small vented alignment, neither HO nor DL have a major efficiency advantage over LF; their 100 dB sensitivity is measured midband, and we give much of that up in the course of normalizing their respective performances to the region of 100 Hz.

Though I haven't tried it myself yet, I expect Dennis is also correct in suggesting that LF would do as well closed-box in this respect as the others could do vented in this small box size. Does this mean that LF is the slam-dunk driver of preference? Nope, merely that there is plenty of fun yet to be found in discovering how well these three woofers might perform in alternative alignments.... :D

[Zilch]

Re: Flex Your PCD Mettle:

Having listened to 2 of the 3 woofers I would go with the LF in the trap box alignment if I did not already own the HO. That being said my trap boxes have arrived and I am actively looking for simple way to bring the volume to about 2.2 cu ft.

We'd certainly like to see how you "customize" the trap kit cabs....

[NEO Dan]

Re: Flex Your PCD Mettle:

Also significant in the results thus far is that in this small vented alignment, neither HO nor DL have a major efficiency advantage over LF; their 100 dB sensitivity is measured midband, and we give much of that up in the course of normalizing their respective performances to the region of 100 Hz.

I've been looking at the DL2515II for HT use with a 80Hz HPF, I think it's got the extra low end you are looking for at 100 Hz. Do you think you could get a good DI match at 12" vertical spacing?

[NEO Dan]

Re: Flex Your PCD Mettle:

I just wanted to add that I am looking at using the BMS 4550 CD in this combo. Has Zilch measured the 4550 on the QSC horn? :D

[Zilch]

Re: Flex Your PCD Mettle:

I've been looking at the DL2515II for HT use with a 80Hz HPF, I think it's got the extra low end you are looking for at 100 Hz. Do you think you could get a good DI match at 12" vertical spacing?

Sure (I think), by lowering the XO frequency to ~1 kHz like JBL 4430, the font of all of this. Can we also achieve a usably tall forward lobe at a 12" c/c distance? Dennis's sims suggest it's possible, but you can see in the Deluxe verticals and Brandon's No Quarter measurements that we're getting near the limit at 10.5". That's about the minimum achievable with a 12" woofer and the 152i waveguide. Wayne uses shorter horns in his Pi-Speakers and still spaces them as wide as 12" with 15" woofers and gets it done, obviously, and he pays more attention to this than just about anybody.

I just wanted to add that I am looking at using the BMS 4550 CD in this combo. Has Zilch measured the 4550 on the QSC horn? :D

Have all that, and can do it, of course, but I sure wish others would get more into this game to validate my own work. Getting the verticals down took some experimentation, but a little trig and a constant mic distance is all that's required using the Zilchster's protocol.

I think the major difficulty in making 152i work with a 15" is not DI or forward lobe, as it'll certainly play down to 1 kHz with a suitable driver like BMS 4550. It's system pattern control needs more investigation, which means build it and measure the polars. As Wayne suggests, the system may be more "forgiving" than we might presume from looking at the elements individually.

I've just stuck with 12" to date because it's been difficult enough to make that happen, and the desired result for HT mains is achievable without moving to 15", necessitating more compromises. If I want "big boy" bass extension, I think I'd just add a second 12" run in "0.5" mode in floorstanders not unlike my test stands, which are JBL 4894s:

http://www.jblproservice.com/pdf/Array%20Series/4894A-90.pdf

[Pete Schumacher]

Re: Flex Your PCD Mettle:

I've just stuck with 12" to date because it's been difficult enough to make that happen, and the desired result for HT mains is achievable without moving to 15", necessitating more compromises. If I want "big boy" bass extension, I think I'd just add a second 12" run in "0.5" mode in floorstanders not unlike my test stands, which are JBL 4894s:

http://www.jblproservice.com/pdf/Arr...s/4894A-90.pdf

It's just that when you put the AE Speakers TD15S into the equation, there's just no combination of 12s that could plumb the depths in that way in a VERY LARGE enclosure. :eek:

But a pair of 3012LF would put up one heck of a fight.

[Dennis H]

Re: Flex Your PCD Mettle:

I like the looks of the 15" Deltalite. It's only about a dB more sensitive than the 12" at 80-100Hz but it has a smoother impedance curve and the breakup peak up high isn't as bad. You only have to lower the XO about 10% to get equal lobing and the cone is a bit deeper, helping with AC alignment.

[Zilch]

Re: Flex Your PCD Mettle:

But a pair of 3012LF would put up one heck of a fight.

:D

[NWCgrad]

Re: Flex Your PCD Mettle:

Out of curosity, what modifications to the X-over does one need to do to add a second 3012LF to a build? I can do the woodworking but not the engineering!

This design just keeps getting better! The box developed by Augerpro (No Quarter's [25" H x 16.5" W x 12.25" D, tuned to 40Hz] modded into a tower for an additional 12" driver for L and R mains, coupled with standard No Quarter boxes for center and rears should make a formidible HT rig for a "reasonable" build cost.

I plan on using the standard DE250 and 3012LF drivers in the QSC waveguide (I have three in hand). Can't start cutting wood till summer - will probably change mind 10 times between now and then. :D

[Zilch]

Re: Flex Your PCD Mettle:

Out of curosity, what modifications to the X-over does one need to do to add a second 3012LF to a build? I can do the woodworking but not the engineering!

Connect the two woofers in parallel and an inductor in series with the "helper."

[Pete'll tell us the appropriate value, based upon an empirical determinaton made with his build.... ]

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Connect the two woofers in parallel and an inductor in series with the "helper."

[Pete'll tell us the appropriate value, based upon an empirical determinaton made with his build.... ]

Better yet, i'll just model it!!! ;)


Update

I gotta say, a TWW doesn't look as good from a vertical polar perspective. But if the .5 woofer is placed above the tweeter, things smooth out nicely from a power response point of view. Both WTW and TWW have smooth horizontal off axis.