Senior Project: Chimera, 3 headed beast

[cjd]

I'm confused how does that allow people to see the crossover components..

Maybe I'm thinking about it wrong..

You don't HAVE to put the speaker ON it. So for show'n'tell, leave the box out. When you get it over and have approval factor concerns, the "show it off" box disappears into the tower design. But you don't have to re-mount or go through any extra pain, it's just designed to work that way.

C

[cjd]

Here's what I've found, as bizarre as it seems:

Resolution in the woofer-mid range matters a little, but not as much as it seems it should, as long as the phase data is accurate driver to driver. It WILL hide things, so there may be less of an ideal response than it at first seems, so it's not the preferred way to work the data.

I've arrived at this conclusion after working a couple different crossovers through live measurement AND full sim processes (based both on measured data and data provided by other folks). In this case, there could be a 3-4dB dip either above or below 600Hz hidden in the resolution, but even with that this ends up being within the normally accepted +/-3dB. So, yes: it's not good enough. Yet, it is.

C

[Blazin]

You don't HAVE to put the speaker ON it. So for show'n'tell, leave the box out. When you get it over and have approval factor concerns, the "show it off" box disappears into the tower design. But you don't have to re-mount or go through any extra pain, it's just designed to work that way.

C

Ahhh I see.. well I guess I'll decide when the components come in and I get a feel for the sizing.. they should be able to fit in the cabinet.. its rather large compared to most designs on here.

[cjd]

Ahhh I see.. well I guess I'll decide when the components come in and I get a feel for the sizing.. they should be able to fit in the cabinet.. its rather large compared to most designs on here.

Yeahhhh. remember who you're talking to. I'm sure Paul and Ryan can fill you in.



C

[Dave Bullet]

Blazin,

Probably too late if you've ordered the parts, but I think L3 is redundant. ie you already have Lbsc to shape the lowpass on the midrange, so not sure why you need L3 (ie. a 2.5mH inductor won't do much if a 1.3mH inductor has already "cut" the slope for you).

David.

[Blazin]

Blazin,

Probably too late if you've ordered the parts, but I think L3 is redundant. ie you already have Lbsc to shape the lowpass on the midrange, so not sure why you need L3 (ie. a 2.5mH inductor won't do much if a 1.3mH inductor has already "cut" the slope for you).

David.

Thanks, I just tried that out.. negative.. causes all sorts of issues.. the Lbsc and Rpara attenuate a hump i was getting at about 900Hz.. resistor alone? sure, adding the inductor keeps it a bit 'flatter'.


CJD -> True. haha.. well they'll be here wednesday anyway.. so no biggie.

[Dave Bullet]

Removing the 2.5mH might affect phase too.....

I was also going to suggest going electrolytics for all caps. Especially for larger cap values if you want to keep this to a tight budget. If you are worried about power handling to the mid - you could parallel the caps (ie. 2 x 44uF to get the 22uF you need).

Cheers,
David.

[BobEllis]

When paralleling caps the values are additive. To get 22 uF you'd parallel two 11 uF caps.

[Blazin]

Haha yep.. maybe he meant.. 'parallel' them aka series them due to the nature of caps.. hah

[Dave Bullet]

Um yeah - 11uF caps.... My maths must have been absent yesterday ops:

[Blazin]

What wattage non-inductive resistors should I be using?

[cjd]

10+W on the tweeter or in zobels is generally plenty.

Were you using any to pad the mid, (or woofers) you might need to consider higher wattage, particularly anything on the woofers. On the woofer you can probably get away with an inductive resistor, actually. It's unlikely to add enough inductance to make a difference.

[Blazin]

Alright, I got a set of 10W 1Ohm resistors.. Guess I'll use those God they are big.

[Blazin]

Wow ok so built the crossover.. installed.. works.. sounds..

Sounds good!

Used some random songs to test and it sounds great.. DMB is so clear.. and songs with bass.. wow! Bass is not over powering and amplitude of the drivers appear to be matched well.. just a quick walk around ear test.. on axis, 30*,60* all sound similar..

I can already tell they are not very sensitive, but maybe its just distortionless audio.. (since "loud" is distortion)

I'm gonna measure these things soon to get a final impedance and freq resp for the system.. see how well I did..

[Blazin]

Finishing ideas:

Front -> Bedliner
Sides -> Vinyl Laminate from PE, Red Maple http://www.partsexpress.com/pe/showd...number=261-620


I got a comment from my roommate yesterday, "Wow man these things are not like home speakers they are DJ speakers."

Alright, so sure they are.. haha but his point was valid in my design mind.. these are not your typical 'narrow' width 'long' length cabinets.. they are nearly matched at 15" wide and 16" deep I feel that covering them in a standard finish would look a bit odd as they look like stacked cubes.. 42" H x 15" W x 16" D

What do you guys think..? perhaps all bed liner? -my prep skills do not warrant piano gloss.. black.. nor is it a preference of mine..

Thanks!

[cjd]

Bed liner can look quite good.

[Blazin]

How do most people apply? Aerosol or Roll on.. I need a good source for it too.. $7/spray can is pretty steep.

[Blazin]

Crossover Pics:

Tweeter



Mid



Sub

[Blazin]

Finished!

[Blazin]

Update, added finished enclosure pic.. need to do final impedance/fr testing tomorrow

[stangbat]

Nice to see the finished product. Good work.

[Dave Bullet]

Good work Blazin. Give yourself a pat on the back.

Assuming you gated correctly when taking individual driver measurements and are consistent with mic placing - you'll find final measurements will be very very close to your sims.

I also suggest you take some in room (farfield) measurements at various distances. Also a measurement with mic at listening position and speakers in final position with both speakers playing mono. You'll probably need to smooth this data.

Also suggest you take some harmonic distortion sweeps (in SW - new signal, sine wave, frequency at 1 power) at probably 2 metres (to get better driver summation for your 3 way).

David.

[ThomasW]

Hurray!!!

[Blazin]

Good work Blazin. Give yourself a pat on the back.

Assuming you gated correctly when taking individual driver measurements and are consistent with mic placing - you'll find final measurements will be very very close to your sims.

I also suggest you take some in room (farfield) measurements at various distances. Also a measurement with mic at listening position and speakers in final position with both speakers playing mono. You'll probably need to smooth this data.

Also suggest you take some harmonic distortion sweeps (in SW - new signal, sine wave, frequency at 1 power) at probably 2 metres (to get better driver summation for your 3 way).

David.

Final room placement isn't exactly determined as of yet.. I have rather small rooms for such large speakers.. ie they'd be close to back wall


I plan on doing on axis/off axis (30-60*) measurements tomorrow...

Room pictures







For reference, the farthest side of the tv cabinet has about 16-17" next to it in width.. I could fit the speaker there.. but it'd prolly create quite a bit of bass in such a tight area.. oh well hah

[Blazin]

Uh so.. how am I supposed to be measuring these to provide full 20-20K FR?

Impedance measured.. looks good, will post later.

[Dave Bullet]

[QUOTE=Blazin]Uh so.. how am I supposed to be measuring these to provide full 20-20K FR?

2 ways:
1. As I mentioned- do a farfield in SW. Farfield observes the start marker (ie. before the impulse) but sets no end marker. You therefore get no gating and all the room reflections etc... This is what you are hearing in your own particular room which is more important than what the speaker produces. Don't be surprised if frequencies below about 200Hz are like a rollercoaster (room modes).

2. Do a gated farfield (as you would for measuring individual driver responses) - say at 1m, then splice in the nearfield response of the woofer and do a port merge as Jay's SW manual describes.

Cheers,
David.

[Blazin]

Alright.. yea the farfield data looks like ass.. the gate looks good though.. gotta merge in the port response.. take it too.. oops.. but looks good..

[Blazin]

Measurements:

[Dave Bullet]

Dang - you've done pretty damn good. :W The FR response looks great to me (esp. 50 - 200 Hz). Your placement in room must be great.

Big pat on the back to ya!

David.