Pictures of my Tri-amped Open Baffles

[Poultrygeist]

The Goldwood is not as highly regarded as the Alpha. If you check out the other forums the majority of H frame builders use Alphas.

[Poultrygeist]

This $189 APPJ/MiniWatt N3 sounds incredible with the Betas. LeRoy, a member here just PM'ed me about how great his N3 is sounding with new tubes. Says it beats his high dollar Rogue.

Small Mini Tube AMP Audio Amplifier APPJ EL84+12AX7B (Original Miniwatt N3) 1set | eBay

[BoJonJovi]

Regarding the 18" GW that is what I noticed as well. I could not find as much on the GW but the Alpha was well covered. Also the few reviews of the GW speaker alone were not great while the Alpha reviews were much better. GW was also more expensive. Taken together it kinda tips the scale to the Alpha.
I have the N3 in my ebay cart but it is going to be a while. I have to finish a few projects first. I am a good starter but a very poor finisher. I am working on that.

[BoJonJovi]

I am planning on pretty much copying your system. I am planning on purchasing the Dayton DTA-100 to run the Eminence ASD1001 horns. What uf capacitor would you suggest for the high pass filter on the ASD's?

I will probably buy the Dayton 150 in the next month or two rather than put the money in crossovers. In the mean time I can be building the speakers.

[Poultrygeist]

The DTA-100 is almost too good for super tweeter duty and would be a good choice for the Betas. I think you've already invested in some class Ds which will probably sound even better than the DTA-100. I went with the DTA-100 as I had it on hand and wasn't using it.

Before spending your hard earned cash on the DTA-100 just to drive the tweets I'd first try running the ASD1001 off the Beta terminals. Your class D amps are much more 4 ohm friendly than my flea tube amps which like a 8ohm load. The PE Lepai t-amp would also drive the ASD1001 which are even more efficient than my Peavey tweets and would be a good bit cheaper.

I'd go with a 1uf cap on the positive tweeter terminal of the ASD1001 but also pick up some .68 uf in case there's more sizzle than you want. You don't need to buy the top shelf caps. I usually go with the audio grade ones one step up from the bottom. Don't forget to buy the wave guides for the ASD1001.

One Dayton APA150 will drive two H-frame Alphas and it could be enough depending on your bass tastes. Maybe get one to start with. If you've got an extra solid state amp with good power you could save a ton using it for the H-frames with two low pass 80hz crossover ( $17 X 2 ). I do this on two of my other systems and don't feel I'm missing anything. FWIW I keep the crossover controls on the Dayton APA150s set at 80hz.

Being of Scottish decent I'm tight and love going cheap and then adding to as I see the need. I bought the Dayton APA150s before I discovered I could use solid state amps with the 80hz crossovers which function as filters and not crossovers. The APA150s do offer more flexibility with their variable XO controls and allow another preout to drive the super tweets independently from but it costs.

You're gonna love the Beta/Alpha OBs. They bring tears to my eyes I kid you not.

[BoJonJovi]

Sounds like a plan and thank you.

Now I need help to understand capacitor selection for this project.

If I understand correctly, a capacitor in series with a driver is a 1st order crossover.

If I connect the betas to the horn in parallel with the capacitor in series between them I should be be at 4 ohms.

If I make the crossover point say 7500 at 4 ohms, the web based crossover generators say I shuld have a 5.3 uf capacitor.

If I run the horn directly from an amp I should have an 8 ohm load. If I cross it at 2500hz as suggested in the PE webpage I should have a 7.95 uf cap. (Recommended crossover: 2.5 kHz, 18 dB/octave)

Also I do not understand the (Recommended crossover: 2.5 kHz, 18 dB/octave), particularly how the 18dB/octave figures in. Is that utilized in some formula?

If I use a 20000 hz crossover point at 8 ohm I get a 1 uf cap. Maybe that is where the crossover should be.
I am not sure I am understanding the 1 uf capacitor selection and if I have any of this right.

Maybe the over 105 temps and all the smoke in Colorado has smoked my mind. Can you help me understand some of this?
Teach me fish.

Speaker Crossover Calculators by V-Cap

[Poultrygeist]

You are reading too much on what others are doing in different systems, getting bogged down in terminology and making it more complicated than it is. Forget all that as mine is much simpler and mirrors a successful build on the DIYaudio forum.

I soldered one end of a 1uf cap to the + terminal of the super horn tweet and the other end to it's hookup wire and that's it. With your horns you can try going up or down a little in cap value but not much. I'd start with 1uf and go down first.

The Betas use no caps or crossovers. The super horn tweets are connected to the two extra terminal tabs on the Betas terminals ( + to + and - to - ) and your amp will see a 4ohm load which class D amps like. You will need to buy blue crimp-on female connectors as all the drivers use the same size.

If you use a single amp for the super tweets you will still use a 1 uf cap on the + terminal and the Beta will present an 8 ohm load.

The Alphas each need a 8 ohm low pass 80hz crossover from PE if you use a regular amp and nothing if you get the Dayton APA150 with built in crossover controls.

If you aren't using a preamp with two outputs then you can still split the CD player's analog output signals and share it between the two amps. If using a third amp ( for tweeters ) the digital signal from the CD player needs to be converted by a DAC to analog before passing it to that amp. The other option would be using the Dayton APA150's preouts to feed the 3rd amp.

In another system I use an old Denon AV receiver ( built in DAC ) which takes the digital signal from the CD player and converts it to analog and drives the OB Alpha woofers.

This build takes 4 to 6 pair of binding posts which can get pricey at PE. I buy mine by the pack at Lowes. They are high quality and designed to be used in keystone wall plates and I just break off the plastic keystone keeper. They accept banana plugs and have a set screw for the hookup wire.

.

[BoJonJovi]

Thanks Poultrygeist
My email signature ends with "I suffer from analysis paralysis".
I pulled the pin and sent my order.
I ordered a set of each of the caps you suggested.

I really appreciate the help.

You have been awesome!

[Poultrygeist]

You are certainly welcome. Let me know how it goes.

[Poultrygeist]

BJ,

You will be driving the 98 db Betas with lots of power although the ratings on those class D amps has always seemed inflated to me. My Sure 100X2 is in reality about 20X2. I drive the Betas with 3.5 watts ( SET running in class A ) which will play them very loud. You probably won't get above 9 o'clock on your class D with the Betas.

The Alphas on the other hand and despite their high efficiency will take lots of power. I know one guy on another forum who drives his H-frames with 250 watt plate amps.

[BoJonJovi]

Any recommendations for baffle size? The dimensions seem to be all over the place.

I have been reading a little bit abut Tone Tubbys and Alnico OB. Not really full rangers but they might make some pretty cool speakers, particularly for blues. Maybe down the road.

[Poultrygeist]

The H-frame dimensions aren't so critical as long as you get the Alphas fairly close to the floor. My H-frames are a cube measuring 17 inches on the insides. 3/4 ply or MDF works well. The baffle is mounted in the center of the cube. The bottom of the inverted T should be the same size as the H-frames. My top baffle is 24 inches high. I used that size as it worked with the half sheet I had on hand.

My Beta is centered about 9 inches down from the top and 7 inches over from the short side. I think it may be better to drop it another 1.5 to 2 inches so the tweeter could then come down to normal ear level depending on the chair you listen in. My chair sits high and I'm tall but you might want to get the tweeter down a little. You can adjust these as you see fit or defer to what MJK uses in his OB papers.

I'm sure you have a router but you may not have a Jasper jig for hole cutting. Buying both sizes is worth the investment but there are probably other options out there that I'm not aware of.

[Poultrygeist]

These OB's have helped me make the leap from high dollar commercial builds with all their hype and bling to what really counts in audio and that's the music. It will allow you to get the highest level of enjoyment without spending a king's ransom. It will not impress with it's looks but it will impress with it's sound. Once you listen to them every box speaker will come off limited, directional, compressed and boxy sounding. I'm so spoiled I keep trying to improve the Tektons ( my last pair of monkey coffins ) which have about reached their point of diminishing returns.

[Poultrygeist]

The 3 way tri-amped OBs look nicer when the lights are low but don't we all?

[Poultrygeist]

[Poultrygeist]

[Poultrygeist]

If using thicker 3/4 plywood or MDF then you should increase all 17 inch dimensions above to 18 inches. The Solenium ST2000 should be Solenium ST200.

[Poultrygeist]

I didn't realize that the $4,000 Emerald Physics CS2.3 open baffle speakers use the same Eminence drivers as these < $400 3 ways............. but the Emeralds aren't tri-amped.

6moons audio reviews: Spatial/Emerald Physics System Review

[Poultrygeist]

A friend at AC built these after being inspired by mine. He's a true craftsman with great wood working skills and loves the sound of these OBs. He went with the more expensive Eminence super tweeters.

[Poultrygeist]

Here's his system. He uses a SET to drive the Betas and dual high power plate amps for the Alpha H-frames. Notice all the matching wood.

[Poultrygeist]

I just ordered a pair of Bohlender Graebener Neo 3 planar tweeters to try with the OBs. I'll need to remove their back cup for them to radiate in both directions. I was reluctant to buy them at first as they are 4 ohm and the Dayton DTA 100 is not recommended for 4 ohm loads. Then I discovered that my Topping TP21 is rated for 4 ohm speakers. I'll swap the Dayton for the Topping which is currenting driving a pair of compression horns on top of the Tektons. The German B&G's I purchased on ebay are shipped from China but what else is new?

Bohlender Graebener Neo3-PDRW Planar Tweeter w/Back Cup 264-735

[Poultrygeist]

In preparation for use in open baffles here I'm prying off the back so these planars can radiate to the rear.

[Poultrygeist]

The planar configuration is the same for front and back but since most people use these in conventional enclosures they ship with backs glued on. They are certainly worth the minor surgery.

[Feanor]

The planar configuration is the same for front and back but since most people use these in conventional enclosures they ship with backs glued on. They are certainly worth the minor surgery.
...

I used this tweeter in a center channel speaker I made a few years back; the result was very good although my speaker is monopole. Removing the back ought to work well, though.

[Poultrygeist]

Good work Bill I know yours sound good. They've gone up in price at PE but I was patient and ordered them from China. Here they are mounted atop the OBs.