Q45's loudspeaker design/build thread

[Q45]

I was just thinking that my idea of a nice speaker face with rounded off edges is seriously lacking one consideration.

That type of speaker face will mean the drivers will be open. Open to anything. Open to such things as my little girl pushing on the woofer with her finers or worse, poking things into the speaker.

That woofer will look like one big button to her, and she is obsessed with buttons. She recently pressed EVERY single button on the inside of my Infiniti Q45 in some sequential order unknown to me, and set the cars stereo system into a cycling mode from Tape to CD to Radio to OFF over and over. I couldn't shut it off.

Should I 86 the open baffle idea and go with a flat face and make a grill cover?

[ThomasW]

Downfiring subs are the best way to protect against little fingers and pets.

[Openly Baffled]

Ah... It's so nice to not have rug rats, urr, uhh, I mean kids.

[cjd]

Dunno. I never destroyed any speakers as a kid - my dad just sat me down and taught me an acceptable way to press on them. (push carefully at the glue seam for the dust cap, and not too hard but gently).

C

[Q45]

See, that's one of the things I like about this forum. You can get almost as many comical, non-technical, commentary type answers that are of no help at all, as you would the techy, helpful answers.

You never know what you're gonna get!

On my Infiniti car club forum I was actually repremanded and scrutinized for constantly throwing out my comedy without any point or direct relation to the topics. :F

I thought it was some funny shizel myself. Eh! Wadda-ya-gonna-do?! :huh:

My woofers don't have dust caps, so I guess it's really just the surround foam that could be open to damage. I'm using a mid & a tweeter that have mesh covers, so I'm covered there.

AHH, what could go wrong? :nuke: I'm sure it'll be fine.
Just have to watch her, right? :baby: :grab:

[Q45]

Driver alignment

Would it ever be acceptable to have the woofer & mid out of alignment on the baffle layout?

For instance, on a 3-way tower, say the 8" woofer is dead-nuts in the middle at the bottom, 5" mid slightly offset to left of center line in the middle of the cab, and the tweeter above that back on center.

Perhaps even throwing the port offset to the right of center on the same plane as the mid.

I know this question lacks the specifics of the drivers and cab volume, but I'm just wondering if there is a standard solid rule that says these drivers need to be in alignment.

I see tweeters offset from center on 2-way towers all the time, bt I have yet to see a 3-way tower that doesn't have all the drivers lined up.

[---k---]

You can offset the mid. In my Khanspires, you'll notice that the mid is offset 0.25" and the tweeter is offset 0.5". It actually helps with the baffle diffraction to them offset. I beleive this is so there isn't as much cancelation at the overlapping frequencies.

If you go to the FRD's website, you can download the Baffle Difraction Simulator (BDS) Spreadsheet and play around with differnt baffle layouts and see how the offset affects the frequency response.

http://www.pvconsultants.com/audio/diffraction/downloadbds.htm

Just be sure to watch the off axis response as well as the on axis.

[ThomasW]

Threads merged...

Lets keep all the questions regarding this project centralized in one thread. That way people don't get lost and everyone can easily see what's been asked and answered.

[Q45]

Threads merged...

Lets keep all the questions regarding this project centralized in one thread. That way people don't get lost and everyone can easily see what's been asked and answered.

UH-HUH! :idea:

So it's like some kinda organization deal here huh? ;lx

Tanks-maan! ;x(

[Q45]

You can offset the mid. In my Khanspires, you'll notice that the mid is offset 0.25" and the tweeter is offset 0.5". It actually helps with the baffle diffraction to them offset. I beleive this is so there isn't as much cancelation at the overlapping frequencies.

If you go to the FRD's website, you can download the Baffle Difraction Simulator (BDS) Spreadsheet and play around with differnt baffle layouts and see how the offset affects the frequency response.

http://www.pvconsultants.com/audio/diffraction/downloadbds.htm

Just be sure to watch the off axis response as well as the on axis.

Wow, that was probably about as close to a "YES" answer as you can get.

I like that! Jokes are good too. But I like the simple "YES" & "NO" answers almost as much.

[Openly Baffled]

See, that's one of the things I like about this forum. You can get almost as many comical, non-technical, commentary type answers that are of no help at all, as you would the techy, helpful answers.

You never know what you're gonna get!

Sorry. I was just thinking out loud. Plus, I'm not one for kids. LOL

[---k---]

Wow, that was probably about as close to a "YES" answer as you can get.

I like that! Jokes are good too. But I like the simple "YES" & "NO" answers almost as much.

That almost sounds like you are complaining that I gave you the tools needed to understand how much offset is good and how much is bad.

Though, I'm sure it was just a bad attempt at humor like the rest of us.

[Q45]

That almost sounds like you are complaining that I gave you the tools needed to understand how much offset is good and how much is bad.

Though, I'm sure it was just a bad attempt at humor like the rest of us.

"Bad attempt"??!! :M

Actually, no I was happy to get a direct answer. Thanks.

[Q45]

Sorry. I was just thinking out loud. Plus, I'm not one for kids. LOL

Yeah well..... I at one time "wasn't one for kids" either.

You know what I also "was not one for"?

Condoms!

But I was one for drinking.

See how life is?


Ya see, there are 2 kinds of people in this world, man.....

People who use birth control.....

And parents!

Her endeth the lesson. ;x(

[Q45]

Almost forgot to post my latest question at hand, I was so enthrawled in all this comedy and schooling.

I received my X-overs from PartExpress last nigh...

Yes, I bought the pre-made ones. So what! It's just a fun starter project with my kid and I didn't feel like messing with X-overs on this one. I wanted to focus on the cabinets.

I gotta tell ya, these things are freakin nice! Nicer than anything I could have glued down to a piece of wood and soldered together.

Anyway, the thing is the X-over is huge! I have the space in the woofer section but I was just thinking that the X-over will be probably 5"-7" from the back of the woofer magnet. The Cerwin Vega woofers are 200wRMS drivers, with very large magnets on them. Although they do have a rather thick rubber cover encapsulating the magnet.

Is there any problem having the the X-over that close to the woofer magnet?

[ThomasW]

This is one of those question where you already know the answer.....

In an ideal situation the crossover is located away from any of the magnets inside the box, unfortunately that's frequently impossible (just look at how most retail speakers are built)

So located it as best you can with regard to the woofer's magnet. Usually we try to shoehorn the XO near the tweeter when that's possible.

[Q45]

This is one of those question where you already know the answer.....

In an ideal situation the crossover is located away from any of the magnets inside the box, unfortunately that's frequently impossible (just look at how most retail speakers are built)

So located it as best you can with regard to the woofer's magnet. Usually we try to shoehorn the XO near the tweeter when that's possible.

Thanks man.

Yeah, the tweeter/mid compartments just aren't an option due to size. Not to mention I really liked the idea of the woofer compartment cuz that's going to be really the only area of future accessibilty to the inside of the cabinet once the veneer has been completed.

So I guess that's my answer as you said.

I just wanted to check to see if there was any hardfast rule to keep the XO away from the woofer before I start finalizing assembly of the cabinet. Cuz I could change dimension still if I had to.

Thanks again.

[Openly Baffled]

Yeah well..... I at one time "wasn't one for kids" either.

You know what I also "was not one for"?

Condoms!

But I was one for drinking.

See how life is?


Ya see, there are 2 kinds of people in this world, man.....

People who use birth control.....

And parents!

Her endeth the lesson. ;x(

LOL! :rofl:

[JonP]

Is there any problem having the the X-over that close to the woofer magnet?

I wondered about that as well, since not just the magnet but a steel frame (or steel anything else) near by has the potential to become a "iron core" and raise the inductance.

So, I got a Jantzen air core inductor I had laying around, took it to work and measured it on our $1K pro LCR meter while playing around with different distances and magnet or steel pieces.

Surprisingly, you didn't get much change of value (about 1% change) until you got to 1-1.5" away from the metal, on the open end of the coil (flat to the open end). You could get closer than that with the metal not on the axis of winding. (flat to the edge of the coil) A lot closer than I expected. Magnet and steel frame were not different in effect.

(here's the short answer you were hoping for...) :W
So, if you keep >1.5 inches away, it shouldn't have a noticable effect.

[Q45]

I wondered about that as well, since not just the magnet but a steel frame (or steel anything else) near by has the potential to become a "iron core" and raise the inductance.

So, I got a Jantzen air core inductor I had laying around, took it to work and measured it on our $1K pro LCR meter while playing around with different distances and magnet or steel pieces.

Surprisingly, you didn't get much change of value (about 1% change) until you got to 1-1.5" away from the metal, on the open end of the coil (flat to the open end). You could get closer than that with the metal not on the axis of winding. (flat to the edge of the coil) A lot closer than I expected. Magnet and steel frame were not different in effect.

(here's the short answer you were hoping for...) :W
So, if you keep >1.5 inches away, it shouldn't have a noticable effect.

Cool. Thanks.

It turns out I'll be about 4.5" from face of X-over to back of woofer magnet.
So hopefully that is a sufficient amount of space between.

[Q45]

So I have my cabinets for the most part assembled now and have the hole for the woofer cut on 1 cabinet and X-overs installed.

I was thinking I'd like to give a test of how the woofer sounds before I cut any more holes for the mid, tweeter & port. Just in case I want to make any changes.

Can I just install a resistor across the terminals of the X-over in place of the mid & tweeter? Assuming yes, does the value of the resistor for this testing necessarily make any difference?

[ThomasW]

There's no need for any resistors on the M/T circuit as long as the amp sees the load of the woofer.

[Q45]

Just as a follow up on my newbie minnie tower project....
The towers are for the most part constructed.
They're approx. 22"Hx11"Wx10"D
2 Dividers with openings cut to basically add strength and separate the woofer, mid & tweeter sections. I used Dayton shielded mid & tweeters just for convenience.
I used a pre-built 3-way X-over from Parts Express and just through in a 2.5 x 5"L port.

I lined the entire interior with dampening material from PartsExpress and stuffed the box with Acousta-stuff.

Everything is done except for the final front baffle and veneer.

Honestly, with my new Onkyo SR505 Receiver these speakers sound great. Considering I just used pre-built X-overs and didn't really use much more than some basic math to determine cabinet volume to match the Cerwin Vega "Car subs" I already had.

But I will say, they are not as good as I thought they would be. But what is weird is that they sound way better as Home Theater speakers than music speakers. But whatever, it was a good project for my son and I to do together.

Oh yeah, and the best part that I actually worried and posted about before?...

The day I brought the speakers in from the garage and set up in the living room to test, my 2 year girl stuck her fingers in through the openings of BOTH tweeters and pushed the dust caps in. So now the tweeters are all dented up.

Oddly enough my son did the exact same thing on a car speaker install AND my last home speaker project back when he was about the same age 12 years ago.

Huh?! That's right baby.... THE CIRCLE OF LIFE!

[Hdale85]

Well using a pre-made cross over with speakers that weren't designed for them (not sure any drivers are designed for those xovers?) You really can't expect too much. Sometimes you get lucky and they get close to the specs of the crossover but usually not so. A crossover really is not very hard to wire up. Designing is another thing but if you use a design listed here I'm sure you could figure it out quite easily and if not lots of people here to help. Although I will say a 3 way is quite a bit more complicated to wire up then a 2 way speaker I made a few mistakes on mine but easily fixed.

[Q45]

Well using a pre-made cross over with speakers that weren't designed for them (not sure any drivers are designed for those xovers?) You really can't expect too much. Sometimes you get lucky and they get close to the specs of the crossover but usually not so. A crossover really is not very hard to wire up. Designing is another thing but if you use a design listed here I'm sure you could figure it out quite easily and if not lots of people here to help. Although I will say a 3 way is quite a bit more complicated to wire up then a 2 way speaker I made a few mistakes on mine but easily fixed.

No, I hear ya on the X-overs. I actually built the cab to match the woofer and then after buying the X-over, I bought drivers to match the spec's. of the X-over as closely as possible.

Honestly I think you're right, I probably should have just built my own X-over cuz it's the 1 thing my kid was bummed we didn't build ourselves. He really wanted to do some soldering. But hey, next 1 right?

Is there any problem with the dust caps on the tweeters being dented inward? Does it affect sound at all? Cuz I heard the sound before toddler damage and after, and I don't hear any diff.

[Brian Bunge]

It shouldn't affect the sound, but you can use a vacuum cleaner hose to pull the tweeter domes back into shape. I had to do this a couple of times after having nieces come over to visit.

[Q45]

I did all my cuts for the drivers and 1 thing I noticed is the Dayton tweeters we ordered don't have that much of an overhand from the face plate to the magnet, if you will.

So basically we cut the hole big enough for the magnet with a little to spare but yet still have a little meat of the MDF for the screws to screw into, but in doing that we noticed the way the terminals on the tweeters are situated you basically have to kinda push them in a bit to fit in the hole. When you do that the terminal actually touch the magnet.

I'm assuming that ain't good. Should we wrap the magnet in electrical tape or perhaps just cut little notches on each side for the terminals?

Maybe having the + & - terminals both touching the magnet might explain why the tweeter seems so much louder and out of place than the other drivers?

Either that or it's the other rather obvious fact that I used the factory built Parts Express / Dayton X-overs, no?

[JonP]

It shouldn't affect the sound, but you can use a vacuum cleaner hose to pull the tweeter domes back into shape. I had to do this a couple of times after having nieces come over to visit.

Another thing to try, is a piece of tape... Stick it to the area and pull the dent out. If the stickyness is right, it can pop it back. You might have to try different kinds of tape.

[ThomasW]

No the terminals shouldn't touch the magnet.

Seems to me shorting the terminals against the magnet would decrease the output of the tweeter not increase it.

Standard practice is to make notches the wood for the terminals.

[Q45]

Paper back Vaneer

I rec'd. from Parts Express the Band-it paper-back vaneer. No instructions really, other than a few lines on the back of the box.

It states to apply contact cement to both surfaces, let dry thoroghly and apply wax paper to prepared surface. It then states to carefully slide wax paper out from between the bonding surfaces. Or something to that affect.

Has anyone done this?

I'm a little confused on the wax paper, sliding it out from between part.

Can anyone clarify or provide suggestions that they had success with?

Can't you just apply contact cement to both surfaces, let dry for a bit until tacky and then roll the vaneer down on to the cabinets?