My first crack........

[503Timber]

.....at going OB.

So I have a wild hair to try open baffle..... I can't seem to find the answers I'm looking for, or at least written in a way this simple mind can comprehend. I have tried putting numbers into the WinISD program and 2 other calculators and have come up with a hand full of different responses......none of which I am sure are right.

So here I come for help

I have 2- 2'X4' 3/4" 9ply oak sheets on hand. I'd like to do a simple baffle using these.....no side panels or anything. I have all the hardware needed.

What I don't have is confidence in my math. I didn't know how to represent this tweeter in the network (or if I can even use the same software for regular cabinets). CTS / Motorola KSN-1005 Flush Mount Piezo Electric Super Horn Tweeter</font>

This is the woofer I am working with Tip Top Electronic Supply - Search Results for B20FU20-54F

I have a Parts Express gift certificate of $50 for the project (lets figure $40 and $10 for shipping) I just need whatever xover parts.


I've recapped speakers before but this is my first attempt at something from scratch so I appreciate the hand holding. To the best hand holder through this project..... I will donate $50 to diyaudio.com in your name.

I realize these aren't great parts but they are what I have around. I do also have a 10" woofer from a Cizek Model 1 and the Peerless tweeters from them as well if that's a better place to start?

[chris661]

Hi,

The woofer you have linked to won't put out much (if any) low frequencies on an open baffle, unless you're prepared to add eq.

Open baffles generally need a high Qts (meaning the driver has lots of output around resonance), so the bass losses due to a dipole system are overcome to give a reasonably flat response. The low Qts of the driver you have linked would suggest it would normally rely on a resonant enclosure (ported box) to lift the bass output.
As dipoles are so lossy, you're also going to need more than 0.1mm of Xmax, especially if you decide to eq the low end.
In short, not a great woofer choice. If you have a pair of those 10"s, that'd be a better place to start: there are many people using a 15" per side on open baffles, so if you could get hold of something of that sort of scale, you've a much better chance of decent LF extension. [edit] The Eminence Alpha/Beta 15s are commonly used. Some prefer the Alpha for the higher Qts, others prefer the Beta "because it comes equipped with a magnet".

Scroll down for a section on piezo tweeters (ie, a circuit to integrate them - they're not very good just used on their own).
Single Driver Website

Chris

[Pano]

What Chris said!

There are a lot of trade-offs that need to be made to go "boxless". Most folks simply won't make those trade-offs - and consequently their OBs don't sound good.
To get it right you will need some combination of the below:

• Big baffle
• Large speaker surface. Think 15", 18", 21" or a bunch of smaller drivers
• Big inductors
• Lots of power
• High QTS woofers
• Time and experimentation

You don't need all of those things, but always some of them. FWIW, my first OB was made from a CTS woofer and horn pulled form an old console. Worst sounding speaker I ever made. Truly awful. But it was a start!

I invite you to have a look at this thread for some ideas: http://www.diyaudio.com/forums/showthread.php?t=110583

[503Timber]

Thanks for the response.....

I was afraid of that with the woofer. They will be in a smaller room that now has Fostex FE127E's in small BR cabinets and I also have some Pardigm Focus v.3.......both produce enough bass for my taste if that helps......I may get enough bass with that 8" and if not probably the 10".

Without knowing the specs on the 10" where do I start? Maybe the Peerless tweeter and the 10" from the Cizeks are a better option all together? I could get a parts list from the original xovers and maybe we could "diy" something together from that......it can be a "pennyless project"

[chris661]

As a thought,

You have a pair of FE127E.
If you were to use those on an open baffle, you'd have a lot more flexibility on crossover frequencies, but matching the woofers up may present more of an issue: a 10" driver is still fairly small for OB use, unless you're prepared to bi-amp (to account for sensitivity differences), and push them (in excursion) pretty hard.

Chris

[Pano]

The Pioneer 8 could make a great OB wide midrange on a small-ish baffle. But you would need bass support. That's not a bad way to go.

[503Timber]

I thought about using the Fostex but I want to put those in Brynn or Gabriel cabinets one day.

The idea of the Piezo with whatever woofer appeals to me for simplicity. My pre has two outs so adding sub is an option.

[ra7]

You should go with the B20 in the baffle, may be near the top of the baffle and then see how much bass it is producing. If it is enough for you, don't bother with a woofer. If its not enough, you can always add an alpha15 near the bottom of the baffle.

But make sure your baffle is at least 2' W x 4' T.

[Pano]

How big a baffle can you do? If it's just for lower mids up, then it does not have to be huge.

[503Timber]

My ply is 2' X 4' 3/4" oak......I believe it's 9 ply. I'd like to use them as is. I may route the edges.

Good point ra7......there will be a lot of room to add a sub near the bottom later.

How far from the top should I mount the B20.....tweeter above or below (I've seen both) On OB, does the mounting point effect xover values? I was hoping to throw some inductors, caps and maybe a resistor on a wood board and call it a day