Flex Your PCD Mettle:

[gmannel]

Re: Flex Your PCD Mettle:

OK great - as to the baffle I would front flush mount the WG, and rear mount the woofer? 3/4" difference as w/ the Deluxe? Do I need to passively High pass the whole box say at 60 or 80Hz or just let the miniDSP do all that(which as of now I know nothing about). In it's eventual HT setting(hopefully will work as a decent center channel) control will be from the AVR's Audyssey MultiQ XT32.
I am only building one(for now, maybe the would be decent surrounds as well? Was going full height LA for surrounds but who knows).
Have lots of 9 ply 1/2" BB on hand so was thinking would laminate to 1", or could use 3/4 MDF. A 1 cf box is small so whatever is best.
In building this, I also want to learn, so to that end I have acquired a Cross Spec Labs calibrated Dayton mic, and a Tascam 122MkII "sound card" to plug into a laptop. What would yall suggest I load up on the laptop to do measuring, modeling, polar maps, etc and any other essential hardware?
Finally, would the miniDSP be a permanent xover, or do I make a passive one from the final DSP settings?

[Pete Schumacher]

Re: Flex Your PCD Mettle:

OK great - as to the baffle I would front flush mount the WG, and rear mount the woofer? 3/4" difference as w/ the Deluxe? Do I need to passively High pass the whole box say at 60 or 80Hz or just let the miniDSP do all that(which as of now I know nothing about). In it's eventual HT setting(hopefully will work as a decent center channel) control will be from the AVR's Audyssey MultiQ XT32.
I am only building one(for now, maybe the would be decent surrounds as well? Was going full height LA for surrounds but who knows).
Have lots of 9 ply 1/2" BB on hand so was thinking would laminate to 1", or could use 3/4 MDF. A 1 cf box is small so whatever is best.
In building this, I also want to learn, so to that end I have acquired a Cross Spec Labs calibrated Dayton mic, and a Tascam 122MkII "sound card" to plug into a laptop. What would yall suggest I load up on the laptop to do measuring, modeling, polar maps, etc and any other essential hardware?
Finally, would the miniDSP be a permanent xover, or do I make a passive one from the final DSP settings?

Baffle question: yes, like the Deluxe.

Your receiver will do the 80Hz HP function in the final setup, so you won't need one on your design.

The BB is excellent material, but I'd think that a sandwich with it and MDF would be great. Use the BB underneath to act as the base for the mounting hardware, and use the finished MDF surface for your paint/veneer.

Holm Impulse is a nice little freebie package that will allow you to get all your measurements.

I'd opt for a passive XO once finished. But that's just me.

[dtruck]

Re: Flex Your PCD Mettle:

Does anybody have any thoughts on this measurement (DE250 on the QSC waveguide)? Mine is red, Zilch's is green. As you can see, there is a significant difference in the crossover region (note the 2dB/line scale)...



Brandon's measurement seems to split the difference, partly:


By the way, somebody should really change the png and gif requirements to no size limit and 30-100kB. Uploading graphs as jpg files is worse quality and takes 5-10 times as much space, but it's the only option right now.

[gmannel]

Re: Flex Your PCD Mettle:

Thanks. Why the Deltalite 2512 and why such a small and sealed box? (remember I'm learning here) And stuff it w/ what?
Do the WG and CD need to be enclosed or can they be mounted on an open baffle shared w/ a sealed woofer box below or can a 1 cf box hold both drivers?
Recommended driver spacing? Same as Deluxe?

[dtruck]

Re: Flex Your PCD Mettle:

I think I can answer most of this while I see if anyone has any answers for me .

Thanks. Why the Deltalite 2512 and why such a small and sealed box? (remember I'm learning here) And stuff it w/ what?

I won't speculate why Pete suggested the driver or that volume in particular, but you might as well go sealed because using it for HT with an 80Hz highpass, there is no need to stretch the bass response. 2 ft³ would be the conventional .707 optimum damping. 1 ft³ would only be a little different, especially with heavy fill (stuffing). You can use whatever you like. Maybe a layer of fiberglass on the walls and then some poly fill. Remember, we're talking 1 ft³ interior volume after subtracting the volume of the driver, and bracing, and the waveguide (if mounted in the same volume).

Do the WG and CD need to be enclosed or can they be mounted on an open baffle shared w/ a sealed woofer box below or can a 1 cf box hold both drivers?

The waveguide does not need to be enclosed, but the benefits of isolating it from the woofer are small to none. As I said above, it's 1 ft³ after whatever you put in the box.

Recommended driver spacing? Same as Deluxe?

You are missing something rather important here. All of the work is already done for you: Delite 12 :D

[gmannel]

Re: Flex Your PCD Mettle:

OK - the Delite is in that trap PA box which is bigger than the above recommended 1 cf enclosure but closer to the 2cf mentioned, so just build a box to roughly the same dimensions as that trap box or even a little taller to get closer to 2cf?
Ordered the WG and CD just now. Woofer soon but awaiting any other input on that particular driver or other recs.
Is it a straight forward process to build a passive xover after getting exactly what you want w/ the miniDSP - eg do the DSP settings readily translate into a passive design? Or, as the DSP is not expensive and enough amp channels to bi-amp are already here, is staying bi-amped and active OK?

[bwaslo]

Re: Flex Your PCD Mettle:

If you already have the DSP, a source that has preamp level controlled outputs and the amps, I'd stay with that. Only downside is the neverending temptation to mess with it.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Does anybody have any thoughts on this measurement (DE250 on the QSC waveguide)? Mine is red, Zilch's is green. As you can see, there is a significant difference in the crossover region (note the 2dB/line scale)...



Brandon's measurement seems to split the difference, partly:


By the way, somebody should really change the png and gif requirements to no size limit and 30-100kB. Uploading graphs as jpg files is worse quality and takes 5-10 times as much space, but it's the only option right now.

Zilch did not have the WG on a flush baffle, but on the trapezoid knock down. There are large protruding edges on the trap enclosure, which have a detrimental effect on diffraction.

[donprice]

Re: Flex Your PCD Mettle:

Here's mine. DE250 on QSC waveguide measured at ~42" at bottom of waveguide/top of woofer. I tried to match your gating value. I believe this was collected with the speaker in my entertainment center which has a baffle edge ~1-1.5 inches tall.

Why is your impulse response squiggly?

[bwaslo]

Re: Flex Your PCD Mettle:

Check your alignment of the driver to the throat of the waveguide, might be off-center.

I don't know why yours doesn't show the dip at 1200Hz, though. Does it change if you move the time window out?

[gmannel]

Re: Flex Your PCD Mettle:

Would this be a bad combo for lobing or other issues?
A line array of 4 of these:http://www.parts-express.com/pe/show...number=290-507,
or 6 of these:http://www.parts-express.com/pe/show...number=290-542,
w/ the QSC/250 combo on top, as a center ch behind an AT screen?
xover miniDSP, bass covered by LR line arrays and TubaHT sub.

[gmannel]

Re: Flex Your PCD Mettle:

Or 8 of these:http://www.parts-express.com/pe/show...number=295-342?

My LR MCLAs are the 4" version of this same driver so the match would be natural.

So any downside to a EconoWave LAY

[dtruck]

Re: Flex Your PCD Mettle:

Check your alignment of the driver to the throat of the waveguide, might be off-center. I don't know why yours doesn't show the dip at 1200Hz, though. Does it change if you move the time window out?

No, I do start to get a ripple as I move the gate out, but it does not line up with the ~1200Hz dip. I have messed with the throat a little, and it seems to only effect much higher frequencies, but I'll be investigating more today.

Here's mine. DE250 on QSC waveguide measured at ~42" at bottom of waveguide/top of woofer. I tried to match your gating value. I believe this was collected with the speaker in my entertainment center which has a baffle edge ~1-1.5 inches tall.

Why is your impulse response squiggly?

Thanks for posting it! Any chance you saved it as an frd/txt file? Your impulse is also squiggly (and inverted, by the way), as is Zilch's. Why mine is a little more uniformly squiggly, I do not know . Could be the lack of a protection cap on mine? I don't have anything big enough to use for that, although I guess I could try to create one from some electrolytics wired up in series-parallel with a film bypass... maybe I'll try that now.

[donprice]

Re: Flex Your PCD Mettle:

FR txt file attached.

Yea, I noticed it was inverted...

[donprice]

Re: Flex Your PCD Mettle:

Would this be a bad combo for lobing or other issues?
A line array of 4 of these:http://www.parts-express.com/pe/show...number=290-507,
or 6 of these:http://www.parts-express.com/pe/show...number=290-542,
w/ the QSC/250 combo on top, as a center ch behind an AT screen?
xover miniDSP, bass covered by LR line arrays and TubaHT sub.

Why not stick with something simple like a single Deltalite 2510 or 2512?

An MTM with a pair the Delta 8 and a 18Sound XD125 looks appealing...at least to my untrained eye.