DIY open baffle speaker build

[DYohn]

Oct 18, 2013 6:02:47 GMT -5 selkec said:

Sweet looking sppeakers. Can you build me a set? maybe close in the bass bin a little

They are better now, still OB but more closed in. I converted it to a damped U-frame system. I get an f3 of 27.3 Hz. The large woofer is a Shiva. Sure I could build you a set - how's around $10K sound?

[selkec]

Wow your speakers are high end. I have to stick to the poor mans speakers. Lol

[gohantanch]

Oct 18, 2013 9:29:07 GMT -5 DYohn said:

I have several thoughts, but first a few more questions.

1) What is the make/model of the mid-woofer you want to use?
2) What is the make/model of the crossover?
3) What are the widths in inches of the two sections of your baffle design?

Once I know this I will be able to make a few suggestions. But I can already tell you the first one is likely to be that the mid-woof you have chosen is not the best choice.

I was not aware of the Dayton folded ribbon, I will check that out.

Since this is an experiment I understand wanting to keep it inexpensive. So why try such a complex design? There are many ways to experiment with OB that do not involve building a 3-way MTM system.

-edit- I just looked up that Dayton Mini-8 AMT tweeter and it really is not suitable for any use other than as a super tweeter. I would not recommend using it below 7KHz and the output is not listed as anything close to flat until 9KHz. You really need a ribbon with a larger diaphragm to use as a standard tweeter. If you want to stick with an AMT (and I don't blame you they usually sound great) a much better low-cost choice would be the Dayton AMT-2.

Thanks for the update on the tweeter, I'll have to rethink that part. To answer your questions:

1. Pyramid W64 6-1/2" Pro Plus Midbass Woofer
This 6-1/2" poly-mica cone midbass woofer features a foam surround, bumped back plate design, and 30 oz. magnet structure. Ideal for use as a woofer in 2-way systems or midrange in 3-way systems.


PRODUCT SPECIFICATIONS
Power Handling (RMS) 100 Watts
Power Handling (max) 200 Watts
Impedance 4 ohms
Frequency Response 60 to 5,000 Hz
Sensitivity 94 dB 1W/1m
Voice Coil Diameter 1"
Magnet Weight 30 oz.

THIELE-SMALL PARAMETERS
Resonant Frequency (Fs) 67 Hz
Mechanical Q (Qms) 3.72
Electromagnetic Q (Qes) 0.93
Total Q (Qts) 0.74
Compliance Equivalent Volume (Vas)

2. Dayton Audio XO3W-625/5K 3-Way Speaker Crossover 625/5,000 Hz
These 3-way, 2nd-order (12 dB/octave) crossovers were designed with a 3 octave spread between crossover points. Dayton Audio metallized polypropylene capacitors are used in critical midrange and tweeter signal paths. 18 gauge inductors were used to keep DC resistance to a minimum. A unique design feature of the low pass section allows use of 4 or 8 ohm woofers, perfect for building a multi woofer system. The midrange and high pass sections are rated for an 8 ohm load. All components are glued or fastened down to eliminate buzzing and vibrations. The high quality blue PC board uses a back plate for added rigidity and eyelet holes for easy mounting. Available in a variety of crossover points. 300W power handling. Board measures: 11-3/8" W x 4-3/8" H x 2" D. Terminals are 0.205".

3. I have no idea on what the actual dimensions will be. That was really just a quick sketch of an idea that I sent to a friend to see if he wanted to do this with me. Any recommendations are welcome.

as far as why I chose such a complex design, I thought it would be a fun challenge. I was thinking of just one midrange driver but at the price I figured why not.

[DYohn]

When you want to use a pre-made crossover like that you are really limiting your choice of drivers. The first key is the mid to tweet Xover point. You need to use a tweeter that has an fs at least half the designed knee. In this case with the Xover fixed at 5K, that would be fs = 2500Hz or less. The AMT-2 would fit that bill. Now that also means you need a mid with flat extension up to cover that cross. With a 2nd order crossover at 5KHz, that means the mid needs to be flat to about 7KHz.

I would not use anything branded Pyramid even for a beater car that I wanted to sound bad. Seriously, that is not a good speaker for any use other than maybe a paperweight.

You need a mid-woof that reaches to about 7KHz and has a listed sensitivity that is not greater than the tweeter. The AMT-2 is rated at 91db (I assume that is watt/meter) so you need a mid-woof that is 91db or less, and if you plan to use two of them in an MTM arrangement cut that by 3, so the mid-woof should be no more sensitive than 88db/watt/meter.

And lastly the bass woofer. Almost any woofer you use will be able to reach 625Hz but it needs to be 6db more efficient than the mid-woof and tweeter to compensate for baffle losses in an OB system. This means you need a 97db/watt/meter woofer, which limits you pretty much to pro audio offerings for the most part. So, rather than limit yourself to that. use the highest sensitivity woofer you can find that has a high Qts and then I can help you design crossover modifications to lower the mids and tweet to match. Take a look at the Acoustic Elegance TD15H.

Once you have chosen different drivers I'll help you calculate the best baffle width - or you can just go for it and slap them onto any old piece of 3/4" MDF and see what you get.

[gohantanch]

Oct 18, 2013 10:12:14 GMT -5 DYohn said:

When you want to use a pre-made crossover like that you are really limiting your choice of drivers. The first key is the mid to tweet Xover point. You need to use a tweeter that has an fs at least half the designed knee. In this case with the Xover fixed at 5K, that would be fs = 2500Hz or less. The AMT-2 would fit that bill. Now that also means you need a mid with flat extension up to cover that cross. With a 2nd order crossover at 5KHz, that means the mid needs to be flat to about 7KHz.

I would not use anything branded Pyramid even for a beater car that I wanted to sound bad. Seriously, that is not a good speaker for any use other than maybe a paperweight.

You need a mid-woof that reaches to about 7KHz and has a listed sensitivity that is not greater than the tweeter. The AMT-2 is rated at 91db (I assume that is watt/meter) so you need a mid-woof that is 91db or less, and if you plan to use two of them in an MTM arrangement cut that by 3, so the mid-woof should be no more sensitive than 88db/watt/meter.

And lastly the bass woofer. Almost any woofer you use will be able to reach 625Hz but it needs to be 6db more efficient than the mid-woof and tweeter to compensate for baffle losses in an OB system. This means you need a 97db/watt/meter woofer, which limits you pretty much to pro audio offerings for the most part. So, rather than limit yourself to that. use the highest sensitivity woofer you can find that has a high Qts and then I can help you design crossover modifications to lower the mids and tweet to match. Take a look at the Acoustic Elegance TD15H.

Once you have chosen different drivers I'll help you calculate the best baffle width - or you can just go for it and slap them onto any old piece of 3/4" MDF and see what you get.

Thank you so much for all the advice. I will try to find the right products that will still fit into my LIMITED budget. I'll keep you updated.

[garym]

You might check Zaph Audio's site for some fairly comprehensive tests/comparisons of different drivers. Also be sure the woofer's specs apply to OB designs.

Are you planning to use active or passive crossovers? 3-way passive crossovers are difficult to design. Actives are easier, but much costlier (you'll need separate amps or amp channels for each driver). Also, as DYohn pointed out, using pre-built crossovers is never optimum; they cannot take into account the particular response characteristics of the drivers you're using.

Strongly suggest you look for a proven design and build it.

www.zaphaudio.com/

diyaudioprojects.com/Speakers/Cobies/

[gohantanch]

Oct 18, 2013 12:10:02 GMT -5 garym said:

You might check Zaph Audio's site for some fairly comprehensive tests/comparisons of different drivers. Also be sure the woofer's specs apply to OB designs.

Are you planning to use active or passive crossovers? 3-way passive crossovers are difficult to design. Actives are easier, but much costlier (you'll need separate amps or amp channels for each driver). Also, as DYohn pointed out, using pre-built crossovers is never optimum; they cannot take into account the particular response characteristics of the drivers you're using.

Strongly suggest you look for a proven design and build it.

www.zaphaudio.com/

diyaudioprojects.com/Speakers/Cobies/

For a first try I am going to use a pre-built 3-way passive crossover. It may not be optimum but I'm not going for perfection here. Thank you for the links, I will try to gleen whatever info I can from them to help me out. 

Much appreciated!

[gohantanch]

Oct 18, 2013 10:12:14 GMT -5 DYohn said:

When you want to use a pre-made crossover like that you are really limiting your choice of drivers. The first key is the mid to tweet Xover point. You need to use a tweeter that has an fs at least half the designed knee. In this case with the Xover fixed at 5K, that would be fs = 2500Hz or less. The AMT-2 would fit that bill. Now that also means you need a mid with flat extension up to cover that cross. With a 2nd order crossover at 5KHz, that means the mid needs to be flat to about 7KHz.

I would not use anything branded Pyramid even for a beater car that I wanted to sound bad. Seriously, that is not a good speaker for any use other than maybe a paperweight.

You need a mid-woof that reaches to about 7KHz and has a listed sensitivity that is not greater than the tweeter. The AMT-2 is rated at 91db (I assume that is watt/meter) so you need a mid-woof that is 91db or less, and if you plan to use two of them in an MTM arrangement cut that by 3, so the mid-woof should be no more sensitive than 88db/watt/meter.

And lastly the bass woofer. Almost any woofer you use will be able to reach 625Hz but it needs to be 6db more efficient than the mid-woof and tweeter to compensate for baffle losses in an OB system. This means you need a 97db/watt/meter woofer, which limits you pretty much to pro audio offerings for the most part. So, rather than limit yourself to that. use the highest sensitivity woofer you can find that has a high Qts and then I can help you design crossover modifications to lower the mids and tweet to match. Take a look at the Acoustic Elegance TD15H.

Once you have chosen different drivers I'll help you calculate the best baffle width - or you can just go for it and slap them onto any old piece of 3/4" MDF and see what you get.

I revised the drivers to at least get close to your recomendations here is the list.

Fountek neocd1.0 ribbon tweeter
freq. 2,000 hz - 40,000hz
sensitivity   90.0 Db 

Factory buyout 6 1/2" poly cone mid bass 
freq 50hz - 6,000hz
sensitivity 88.3db
Qts .95

goldwood gw-212/4 12" woofer
freq. 28hz - 4000hz
sensitivity. 92.3db
Qts 1.20

[DYohn]

Those are MUCH better choices. Good work. Those drivers should be OK with the pre-made crossover. At least you won't destroy anything and you'll have decent full-range coverage! I won't guarantee how good it will sound, but I will say that Fountek ribbons are good sounding and Goldwood woofers are surprisingly decent.

[gohantanch]

Oct 18, 2013 16:46:35 GMT -5 DYohn said:

Those are MUCH better choices. Good work. Those drivers should be OK with the pre-made crossover. At least you won't destroy anything and you'll have decent full-range coverage! I won't guarantee how good it will sound, but I will say that Fountek ribbons are good sounding and Goldwood woofers are surprisingly decent.

Surprisingly decent is what I'm shooting for. 

[gohantanch]

Oct 18, 2013 16:46:35 GMT -5 DYohn said:

Those are MUCH better choices. Good work. Those drivers should be OK with the pre-made crossover. At least you won't destroy anything and you'll have decent full-range coverage! I won't guarantee how good it will sound, but I will say that Fountek ribbons are good sounding and Goldwood woofers are surprisingly decent.

[gohantanch]

Oct 18, 2013 16:46:35 GMT -5 DYohn said:

Those are MUCH better choices. Good work. Those drivers should be OK with the pre-made crossover. At least you won't destroy anything and you'll have decent full-range coverage! I won't guarantee how good it will sound, but I will say that Fountek ribbons are good sounding and Goldwood woofers are surprisingly decent.

Ok so I'm up late not able to sleep I was mulling over designs for the speakers and this is one idea I came up with. The wider section for the woofer is at close to a 45degree angle with the woofer as low on the section so that the back of the woofer is braced by the bottom of the speaker platform. The mid range/tweeter section will be at a slight angle and will come all the way down to the bottom giving a backing for the woofer to give more surface area for the low end. With two support pieces in the back to brace the whole thing. Above is another drawing of my idea. Of course it's nothing concrete and if you think it's a stupid idea for a design let me know.

[garbulky]

I love it! As you admitted, you are slightly clueless to this stuff - (as am I) - and I commend you for giving this a go. I bet it will be a super fun project. I wish I had the will power to figure these things out. I wish you the very best of luck and am following this thread with interest!

[gohantanch]

Oct 23, 2013 5:01:24 GMT -5 garbulky said:

I love it! As you admitted, you are slightly clueless to this stuff - (as am I) - and I commend you for giving this a go. I bet it will be a super fun project. I wish I had the will power to figure these things out. I wish you the very best of luck and am following this thread with interest!

Haha yeah I am clueless. Luckily DYohn here has been really cool in giving me a lot of pointers and it's beginning to make sense why he recommends what he does.  I'll keep you updated. 

[DYohn]

I recommend against angling the lower baffle like that. The reasons are many, but the biggest is that your woofer is not a subwoofer: it is crossed over at 625Hz. Take a look at this simple graphic and see how much of the musical spectrum is below 625 Hz. If you angle the baffle like you describe, you'll be hearing this off-axis. You want the woofer pointed at the listener, not off to the side or at the ceiling or the floor.

[gohantanch]

Oct 23, 2013 10:57:17 GMT -5 DYohn said:

I recommend against angling the lower baffle like that. The reasons are many, but the biggest is that your woofer is not a subwoofer: it is crossed over at 625Hz. Take a look at this simple graphic and see how much of the musical spectrum is below 625 Hz. If you angle the baffle like you describe, you'll be hearing this off-axis. You want the woofer pointed at the listener, not off to the side or at the ceiling or the floor.

Good to know! Back to the drawing board! Thanks again! 

[gohantanch]

Its been forever I know, but here is a little update. I have all the parts for my speaker, however I've run into the small problem of not having any tools and the basic wood working know how to make my speakers. Its a small bump in the road that I'll just have to work on figuring out.

[lionear]

Electrostatic speakers are "open baffle" designs. The issue you'll face is that bass frequencies radiating from the back will diffract around the baffle and cancel out the bass frequencies radiating from the front. This is not an issue for higher frequencies. You need a box for the woofer so that the back wave is dealt with. Or you need the baffle to be as big as possible - which would make the design more and more like an infinite baffle.

The latest NOLA speakers, which are getting rave reviews, is an open design.

Here's an open baffle design: gr-research.com/obseries.aspx.

[gohantanch]

Mar 13, 2014 10:15:34 GMT -5 lionear said:

Electrostatic speakers are "open baffle" designs. The issue you'll face is that bass frequencies radiating from the back will diffract around the baffle and cancel out the bass frequencies radiating from the front. This is not an issue for higher frequencies. You need a box for the woofer so that the back wave is dealt with. Or you need the baffle to be as big as possible - which would make the design more and more like an infinite baffle.

The latest NOLA speakers, which are getting rave reviews, is an open design.

Here's an open baffle design: gr-research.com/obseries.aspx.

The design I'm not worried about, Its just the actual construction i'm worried about.

[prohobo]

Oct 17, 2013 18:00:22 GMT -5 gohantanch said:

I have been mulling over the idea of building a pair of open baffle speakers. I got the idea from a customer of mine that does it on a grand scale(we're talking $50,000 drivers. Ridiculous!) and I figure I could make a first shot at a pair in the $200-$300 range.

Anyone out there have any experience with them? I am going in pretty blind. I've never done anything like this but I thing it could be fun.

any tips and/or advice would be greatly appreciated. 

I actually went on the same journey - I posted my DIY project on here (check it out):

emotivalounge.proboards.com/thread/24562/speaker-building-journey