Flex Your PCD Mettle:

[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.

[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.

[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?

[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?

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?

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:

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:

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.

[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.

[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:

Design recomendations

Using the B&C DE250-8 1" + QSC PL-000446GP Replacement Waveguide Horn for HPR152i (or different if you rec)
and bass is covered by 15" Dayton Titanic Tuba HT 24"
and the LR are MCLA w/ 16 each http://www.parts-express.com/pe/show...number=295-338
What would ur rec be for the woofer in a 2 way single center channel speaker and what crossover point - could do w/ biamped miniDSP as well as a passive
I like Dayton Ref drivers but pro OK if better.

That guide/tweeter combo is begging for the or Deltalite 2512 in a sealed, stuffed, 1cf enclosure.

[gmannel]

Re: Flex Your PCD Mettle:

Design recomendations

Using the B&C DE250-8 1" + QSC PL-000446GP Replacement Waveguide Horn for HPR152i (or different if you rec)
and bass is covered by 15" Dayton Titanic Tuba HT 24"
and the LR are MCLA w/ 16 each http://www.parts-express.com/pe/show...number=295-338
What would ur rec be for the woofer in a 2 way single center channel speaker and what crossover point - could do w/ biamped miniDSP as well as a passive
I like Dayton Ref drivers but pro OK if better.

[Zvuchniak]

Re: Flex Your PCD Mettle:

........... the method I think you're describing is a fairly accurate simulation in bass impedance with an extrapolation based on Le into the midrange.

Quite right. I thought that is what you're looking for.

Regards

[dtruck]

Re: Flex Your PCD Mettle:

Zvuchniak, thanks for the offer, but what I need is a precise impedance curve in the midrange, while the method I think you're describing is a fairly accurate simulation in bass impedance with an extrapolation based on Le into the midrange.

I already performed the measurement method that you linked to, and it matched physical measurements - that's in the AK thread linked in my post above. However, my frequency responses are still a little suspect, IMO, so the project is somewhat on-hold while I try a bunch of things to identify and reduce any flaws in my impulse measurements. I may have a post on here regarding that tonight if I don't get anywhere new..

[Zvuchniak]

Re: Flex Your PCD Mettle:

I think they will be, someday. Btw, bwaslo, if you were to download my PCD files, you would find "TD15M_bwaslo_shifted_down.zma". I am using your impedance measurement divided by 2 as a stand-in until I get a real one.

If you tell me internal box volume and tuning frequency, i can calculate your speaker impedance based on that and TS parameters using Frequency Response Modeler.

If you want

Use Jeff Bagby's guide how to measure so we can use it in PCD knowing it will work. Download it from here:

http://www.box.net/shared/ouxjjsx0m8bs00cil5iq

[bwaslo]

Re: Flex Your PCD Mettle:

Well, you can blame me if there are problems, then!

Using a 4 ohm driver is what I wanted to do, but not what I had. It will give you about another 3dB in sensitivity (not efficiency, but if you use a class D amp, it comes to about the same thing). A little T-Amp would even do well.

I found that it all works best with the speakers up on stands, so the woofs are several ft off the floor and the tweeters are at ear level. And of course, toe-in. Plan to spend a lot of time listening to music when you get them done, and for your friends to tire of hearing about your speakers.

[dtruck]

Re: Flex Your PCD Mettle:

I think they will be, someday. Btw, bwaslo, if you were to download my PCD files, you would find "TD15M_bwaslo_shifted_down.zma". I am using your impedance measurement divided by 2 as a stand-in until I get a real one.