Greetings and My First Decent Build

[greywarden]

Hello all I was lurching for all of 5 minutes and decided I had to join!

Earlier this week I ordered (2) Peerless 835004 woofers and (2) Tymphany DU0188 Tweeters, both buyouts. I plan on using the Acoustic Reality Series Crossover and when I found that Passive Crossover Designer 7 implements the Acoustic Reality, I was overjoyed!

This is going to be a long, drawn out build, I'm getting the palm router and speaker wires I need for Xmas and I'll probably be asking quite a few questions.

Anyhow, on to my design. I'm a very big fan of both Tony Gee and Pierre from Mapleshade, so my first set of speakers are going to be leaned back, and I'm going to call it the Slant, creative, I know.

I have a decent amount of woodworking skills brought gained through working with my father since I was old enough to wield a hammer and put nails in a piece of 2x4.

Here is my design:



Now, I have a few questions...

1) After reading up about time alignment I don't believe I'll be adding a wierd lump onto the front baffle, thus the "leaned back" approach. I "leaned" the enclosure back 5 degrees, and now that I'm looking at it, I don't think that will be enough. What are you thoughts/opinions?

2) After toying (read: opening and being dumbfounded) with Passive Crossover 7, does anyone have an FRD or ZMA file for either of my drivers? If not, I suppose I'll have to tack on another few items to my list (any recommendations?) for measuring the drivers.

Thanks!

Channing

[johnnyrichards]

My thoughts on time alignment? I'm not sure, since it cannot absolutely be solved structurally without knowing absolutely your acoustic centers, you will still be making up for it in the crossover. The slanted baffle look is very attractive, however, so there is no reason to not do it as long as you compensate for the "built in" off-axis effects.

[greywarden]

Couldn't you just use the deepest point of the woofer's (the peerless 835004's concave in this respect) cone and the outermost point of the tweeter and angle the front baffle back enough to line them up vertically?

That seems to make since to me. As long as you're listening position is at ear-hieght with the drivers...

[johnnyrichards]

Couldn't you just use the deepest point of the woofer's (the peerless 835004's concave in this respect) cone and the outermost point of the tweeter and angle the front baffle back enough to line them up vertically?

That seems to make since to me. As long as you're listening position is at ear-hieght with the drivers...

Kind of. Acoustic centering is more complex than that, I guess. There are ways to determine it but I don't know them right off the top of my head. I think Curt Campbell has a method that is relatively painless.

[greywarden]

I'll have to look into that.

I have the drivers, and tried my best to measure the tweeter response. The tweeter is the one that Vienna Acoustics uses in a few of their designs with a port behind the tweeter. It has a pretty flat response other than that it slopes down 3-5dB from 3k to 20k, and that's the whole of it's response as well.

I do have a question.

When I'm trying to model a ported enclosure with WinISD pro, I try to keep the cone excursion below the xmax line and I end up with a useless box response. And when I model a closed box, in order to get the cone excursion close to the limit it's twice the volume of my listening room (which just so happens to be very tiny, lol.). What is an acceptable amount of excursion?

[Zero the Hero]

I do have a question.

When I'm trying to model a ported enclosure with WinISD pro, I try to keep the cone excursion below the xmax line and I end up with a useless box response. And when I model a closed box, in order to get the cone excursion close to the limit it's twice the volume of my listening room (which just so happens to be very tiny, lol.). What is an acceptable amount of excursion?

what do you mean by "useless box response"? You can't keep excursion below xmax in a ported system anyway, not under box tuning. At that point the woofer "unloads", just nature of the beast. you want to try and keep the first hump below xmax, the one above tuning.

[fastbike1]

I'd guess you're making an entry mistake. The Peerless in a sealed box should tune to F3 57 Hz in 6 liters with flat response at Xmax. 92 dB. Ported works pretty well in 18 liters. See Lou C's LECBOS.
Use the measured parameters:
Fs (Hz) 45.20
Re (ohms) 3.58
Le (mH) 0.65
Vas (liters) 25.14
Qes 0.325
Qms 4.83
Sd (cm2) 143.1
Xmax (mm) 3

As said, you won't be able to stay under Xmax with ported. You need to keep the excursion frequency below the realistic speaker response (Say less than the -10dB frequency).

I'll have to look into that.

I have the drivers, and tried my best to measure the tweeter response. The tweeter is the one that Vienna Acoustics uses in a few of their designs with a port behind the tweeter. It has a pretty flat response other than that it slopes down 3-5dB from 3k to 20k, and that's the whole of it's response as well.

I do have a question.

When I'm trying to model a ported enclosure with WinISD pro, I try to keep the cone excursion below the xmax line and I end up with a useless box response. And when I model a closed box, in order to get the cone excursion close to the limit it's twice the volume of my listening room (which just so happens to be very tiny, lol.). What is an acceptable amount of excursion?

[greywarden]

Ok yeah, the factory specs are way off from those.

Maybe I'll stick to a sealed design for my first build. It'll be that much easier to build as well.

Thanks for the help/suggestions, guys.

[fastbike1]

True. The values I gave you are the average from several sets of measurements that a number of folks on this board have made.

[QUOTE=greywarden;1671584]Ok yeah, the factory specs are way off from those.

QUOTE]

[greywarden]

Ok, I just made some measurements for the acoustic centers of my drivers and my 5 degree slant will actually be perfect!

[Chris Roemer]

Ok, I just made some measurements for the acoustic centers of my drivers and my 5 degree slant will actually be perfect!

Howdy.

TTBOMK, your physical "time-alignment" will only hold if you bi-amp using active filtering. The inductive and capacitive elements (coils and caps) in a passive crossover introduce phase shifts, both ahead of and behind a zero phase angle. Modern passive XO design uses driver phase data in the model and accounts for it in choosing the filtering elements. You might think that the slanted top/front looks cool (lots of people do), but it most likely won't have as much to do wth phase aligning your drivers as proper filter design.

Chris

[greywarden]

Oh well nvm then, at least it'll look cool...

[greywarden]

Well I worked out a design on WinISD for a 3dB shelf ported design. The Box is coming out to 27.6L dimensions are 20.75"T x 13.5"D x 9"W. Fb is 41.3Hz and the port is 1" x 7.5" x 10.375"L which will share one side with the back of the box.

This is going to be my prototype box depending on how nice the boxes come out

[greywarden]

I'll be getting my wood cut this weekend, hopefully!

On another note, I have a question.

I've decided to make this enclosure the actual enclosure and not just the prototype, finally, and I want to do a round over on all the vertical edges, and not the horizontal edges, then I want to veneer all the vertical sides. I found some "prefinished hickory veneer" (I don't want to frack anything up, with this being my first build). That leaves the visible top and non-visible bottom. For the bottom I'll just paint it black. For the top I'd like to try my hand at a Piano Black finish.

So how would you guys recommend I go about doing that? Paint the bottom, Finish the top, then veneer and line it up at the top, so I just have to trim the bottom?

[greywarden]

Okay, here's my BSC/Room graph. What do I need to do with this? What information can I obtain from this?

[Wolf]

Okay, here's my BSC/Room graph. What do I need to do with this? What information can I obtain from this?

You apply it to the graphs you used in PCD, and then double check your model. I think you have to import the curve to RM, and then apply it, and resave.
Later,
Wolf

[greywarden]

Cool Thanks, I'll work on that, wife had to buy fabric for Halloween Costumes, so the wood will have to wait till next paycheck!

[henrikhegh]

Hi.

The acoustic center a located somewhere around where the coils is connected to the cone. But with a simple mls meassurement, its very easy to find precisly.

You meassure the tweeter, the bass and the both of them i parallel. Then you import the meassurements into eg lspcad. Then you increase the delay in the simulation untill the simulated frequencyresponse matches the meassured one. Then you have your delay, very precise.

The greater the distance to the speaker, when meassuring delay, the better. And the mic has to be between the units (not tweeter height)

(No, spelling is not my middle name, nor in Danish og English)

[greywarden]

Haha, that's fine. I'm not going to time align this one, or at least this cabinet.

I do, however, have an update!

I got my wood cut yesterday! It only took a half a sheet of MDF, so the other half is going towards a sewing table for my wife.

I'm also ordering some box building/assembly items:

Crossover Parts
Gold Binding Posts, Dayton Brand

[henrikhegh]

Hi,

You need to find the acoustic delay, in order to make an valid crossover.