BillFitzmaurice.info

ecut1 wrote: Can I space the tweeters a bit further apart or will that result be negative?

I'd space them 2 1/2 to 3 inches on center. At the distance you'll be using them at you won't have any lobing issues. I don't with mine.

Well, that's a relief! I re-spaced them at 2.5" and 3". I guess I'll go with 2.5" because I'm at 80% or more of the length. Do you think it'll be worth it to upscale the cabinet 10 inches in order to get the extra drivers in or is this just plain overkill?

One more question regarding the impedance...

I'm probably going to build the crossover at 4000Hz. Looking at the impedance charts these drivers look to run at about 14 or so ohms at that range. From the plans I learn that with 8 drivers in series/parallel it will cut that in half. I should be safe with a receiver that can run at 6 ohms, correct?

Thanks again for chiming into this thread and helping me out!

I like pics like that. It's when you start to get all excited about the build process. Once I start seeing "drivers on or in wood" that's when it starts becoming real for me.

Ecut1, would you mind posting some detailed pics of those tweeters? I have the old style that were on 6x9 frames, and they look ugly. I would consider offing them for the ones you obtained. They look really nice to me. Thanks in advance.

ecut1 wrote:Well, that's a relief! I re-spaced them at 2.5" and 3". I guess I'll go with 2.5" because I'm at 80% or more of the length. Do you think it'll be worth it to upscale the cabinet 10 inches in order to get the extra drivers in or is this just plain overkill?

I would.

One more question regarding the impedance...

I'm probably going to build the crossover at 4000Hz. Looking at the impedance charts these drivers look to run at about 14 or so ohms at that range. From the plans I learn that with 8 drivers in series/parallel it will cut that in half. I should be safe with a receiver that can run at 6 ohms, correct?

Where the amp loading is concerned you consider the nominal impedance, not that at the crossover. That said, my TLAH are 4 ohms used with a 6 ohm AVR and I haven't had a problem, because they're so efficient that they don't draw much current. Or to be safe you can go nine drivers and end up with the total being the same as one when wired as series/parallel triplets.

miked wrote:I like pics like that. It's when you start to get all excited about the build process. Once I start seeing "drivers on or in wood" that's when it starts becoming real for me.

Mike, yes I'm very excited to get this project going!

DJPhatman wrote:Ecut1, would you mind posting some detailed pics of those tweeters? I have the old style that were on 6x9 frames, and they look ugly. I would consider offing them for the ones you obtained. They look really nice to me. Thanks in advance.

Here are some more detailed pics. There's not much info about them online. What I found is they are made by audax and were used in a Harman Kardon "Festival 80" - some sort of an all in one retail box surround sound system I think. I paid $36 (shipped) for a "tray" of them which was 49 tweeters. I bought them from Apex Jr.

Bill Fitzmaurice wrote:Where the amp loading is concerned you consider the nominal impedance, not that at the crossover. That said, my TLAH are 4 ohms used with a 6 ohm AVR and I haven't had a problem, because they're so efficient that they don't draw much current. Or to be safe you can go nine drivers and end up with the total being the same as one when wired as series/parallel triplets.

One more thing I'm concerned about is a topic from a thread I read about the sensitivity of the two lines matching (this thread... http://billfitzmaurice.info/forum/viewt ... it=apex+jr) I was excited to find that thread but it ended without updates as the project went on.

With either 8 or 9 drivers should I be concerning myself with the sensitivity of the driver line vs the tweeter line? In that thread gene had figured he needed to use 16 tweeters. Doing the math wouldn't be a problem for me if I understood more about what I was figuring. Once again, I may be thinking it through too much.

I like how these are coming on, can't wait to see your opinions on the sound.

Lots of distractions today but I did get started.

ecut1 wrote:Lots of distractions today but I did get started.

...and we have liftoff!

It was nice of you to post the VERY accurate dimensions of your tweets as well as what you paid/where purchased. Way to help the community!

miked wrote:
...and we have liftoff!

It was nice of you to post the VERY accurate dimensions of your tweets as well as what you paid/where purchased. Way to help the community!

Hey, I'm a deal hunter... when I find something I have to share it!


A little more progress happened today but I only had about two hours to work on them.
I have a question... I'm going to mount the drivers and tweeters from the inside so I rounded the holes over with a 1/4 round bit as it explains in the plans. However, I do have enough room to probably use my 3/8 round over bit. If I do that will it help the sound, hurt the sound, make no difference, etc? I think it would help the tweeters look like they're not buried so deep in there, it might make it look better.

I'd use the 3/8, it will help the high end a bit. The hole in the baffle acts as a resonant pipe, the smaller the hole the lower the resonance, damping the high frequency response.

Cool, I'll hit it with the 3/8 bit. Thanks for the info. There should be plenty of room between the drivers for a 3/8 round over.

Another thing I could do at this point in the game is countersink the tweeters by running a straight bit all the way up and down the tweeter line to reduce the baffle thickness to a half inch. That would bring the tweeters forward and thin out that pipe. It would be fairly simple and quick to do on the router table. Would it be worth it?

ecut1 wrote: Another thing I could do at this point in the game is countersink the tweeters by running a straight bit all the way up and down the tweeter line to reduce the baffle thickness to a half inch. That would bring the tweeters forward and thin out that pipe. It would be fairly simple and quick to do on the router table. Would it be worth it?

It may or may not be worth it, but can't hurt.

ecut1 wrote: One more thing I'm concerned about is a topic from a thread I read about the sensitivity of the two lines matching (this thread... http://billfitzmaurice.info/forum/viewt ... it=apex+jr) I was excited to find that thread but it ended without updates as the project went on.

With either 8 or 9 drivers should I be concerning myself with the sensitivity of the driver line vs the tweeter line? In that thread gene had figured he needed to use 16 tweeters. Doing the math wouldn't be a problem for me if I understood more about what I was figuring. Once again, I may be thinking it through too much.

Hey. I have not updated due to not being able to have time to get things done. I'm actually planning on finishing the build in a few weeks. I cnc cut out a piece of old ply to test fit everything when I was at the wood shop this weekend. I'm waiting on the good half inch plywood to come in that I plan on using. I'll post some updates and play with one the week of december 8th. I am going to measure using a calibrated mic and it will be using an active passover/minidsp to see how it does.

Hmm, I may just wait to buy my crossover components. Would you mind sharing your data with me once you get your crossovers figured out?

This is what I was going to order...