"Yield" Open-Baffle

Gothover · « **on:** 28 Apr 2012, 09:17 pm »

Here is my "Yeild" Open-Baffle.

I used a bandpass port design, however retuned the cavity for better bass response, I also made the cavity adjustable for use with different 15 inch drivers.

I went with a 2-way active design, using the Audio Nirvana 10 for the HF section.

I stuck with the Eminence 15A's for now, they sound great in this configuration, very natural.

I am also sticking with the Mini DSP, sounds great, very quiet, and direcly imports R.E.W. (nice feature)

Dave

Gothover · « **Reply #1 on:** 28 Apr 2012, 09:19 pm »

Front and Side

Gothover · « **Reply #2 on:** 28 Apr 2012, 09:22 pm »

Gothover · « **Reply #3 on:** 28 Apr 2012, 09:36 pm »

I am building another set, that I intend to finish in dark walnut. I will post some pics when they are ready.

I wasn't sure I was going to like open baffle designs, but they are incredibly addicting. In fact, I went to a freinds house today, and listened to his high $$$$$$ Ambiance Ref 16's, and thought the bass was boomy and overdone. Probably because the bass section is a ported design, and I am getting used to the planar type bass once again.

Dave

mightym · « **Reply #4 on:** 28 Apr 2012, 09:44 pm »

Interesting project.

Where are you crossing them/what slope?

How did you determine the front chamber vol. for the Eminence woofers?

How low does this extend the bass from them?

Thanks,
John

Gothover · « **Reply #5 on:** 28 Apr 2012, 10:07 pm »

Hi John, I am crossing them at 200hz

18db LF rollof and 6db HF.

My design allows me to add spacers to increase chamber volume.

Dave

opnly bafld · « **Reply #6 on:** 28 Apr 2012, 10:22 pm »

Quote from: mightym on 28 Apr 2012, 09:44 pm

How low does this extend the bass from them?

http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf

Gothover · « **Reply #7 on:** 28 Apr 2012, 10:47 pm »

JohnR · « **Reply #8 on:** 29 Apr 2012, 12:04 am »

Nice

So the woofers are actually on the back of a chamber, with ports directly opposite? I wasn't aware of that.

Ric Schultz · « **Reply #9 on:** 29 Apr 2012, 12:25 am »

If you put EAR SD40AL constrained layer damping material on the woofer frames and also magnet brace both woofs and also brace the baffle with the same brace you will get much, much better bass. I cannot seem to figure out how to make a picture appear here so I will try and load it to my Gallery. The last pic in the gallery shows an alpha 15 in an h-frame with EAR damping material applied and also the magnet is epoxied to a piece of 13 ply plywood which is bolted to 26 ply plywood brace. You can use just one brace for both magnets and curve it around so it also braces the baffle between the woofs and full range. Way better sound! The Gallery also shows an open baffle speaker that also has both Alphas damped/magnet braced and the baffle braced....very crude version.

Gothover · « **Reply #10 on:** 29 Apr 2012, 01:00 am »

Quote from: JohnR on 29 Apr 2012, 12:04 am

Nice

So the woofers are actually on the back of a chamber, with ports directly opposite? I wasn't aware of that.

Yes, I did that for several reasons, primarily for tuning and being able to service the drivers without dissassembling the entire speaker.

Dave

Gothover · « **Reply #11 on:** 29 Apr 2012, 01:31 am »

Quote from: Ric Schultz on 29 Apr 2012, 12:25 am

If you put EAR SD40AL constrained layer damping material on the woofer frames and also magnet brace both woofs and also brace the baffle with the same brace you will get much, much better bass. I cannot seem to figure out how to make a picture appear here so I will try and load it to my Gallery. The last pic in the gallery shows an alpha 15 in an h-frame with EAR damping material applied and also the magnet is epoxied to a piece of 13 ply plywood which is bolted to 26 ply plywood brace. You can use just one brace for both magnets and curve it around so it also braces the baffle between the woofs and full range. Way better sound! The Gallery also shows an open baffle speaker that also has both Alphas damped/magnet braced and the baffle braced....very crude version.

Rick, the EAR is great dampening material, and I agree the rear brace does work great. I decided to research this due to your suggestions, and found that you were absoluely correct, the basket of the Alpha 15A does infact generate its own audible artifacts.

This was easy enought to prove using a stethoscope, or just touch the driver while its playing at moderate levels.

I spent several hours using a magnetic accelerometer and an EVA to measure the baskets vibration, the I switched from the EVA to my osciliscope because I needed greater sensitivity. What I found is most of the vibration is caused by the "for lack of better words" oil canning that occurs at the large flat open area the magnet attaches to, and not the beams.

What I did to correct this was cut 1.5" thick 8"diameter MDF doughnuts to be epoxied to the oil canning area, then I used Max MCR black to fill and permenently attach the doughnuts to the magnet structure, and took measurements again. What I found was the doughnuts were nearly as good as the rear brace I tried, and simple to build.

Dave

Ric Schultz · « **Reply #12 on:** 29 Apr 2012, 07:27 am »

Glad you are experimenting. I would not trust measurements. When I first damped the woofs it was just with the EAR material. Huge improvement. Then we added the first brace in the crude jobbie and then the second brace. Each time a huge increase in sound quality. We did not remove the damping material after adding the braces but I still think the baskets would still ring if you do not use the EAR as well. The only way to know if it would make more difference is to apply it and listen. Using a measurement tool only gives you so much info. Your ears are infinitely better in picking up nuances. However, not bracing the baffle is a mistake. It has to be seriously rigid. A more massive, heavy, constrained layer damped and larger base would also help. The more damped weight the better. A little piece of plexiglass is not a serious base. Of course, you need serious feet as well. The more massive, dead and rigid the baffle and drivers are the more the sound accelerates with speed and low distortion (super transparency!!!). You should only be hearing the cones vibrate....not anything else. Your dognuts....he he....are very cool. Good idea. However, I would not trust they are as good as magnet bracing.

Gothover · « **Reply #13 on:** 29 Apr 2012, 02:25 pm »

Thanks for your input Rick , I certainly agree, the dampening material will definately not hurt anything. I think these baffles are fairly rigid, as they are 5" thick mdf green glued and weigh in in empty at 53 lbs each. The Base is 9/16" plexiglass with 2"floor spikes.

I still like the idea of the rear brace, it's just gets a bit tricky to build, and everything is a tradeoff. I left the wiring exposed so I always have the option of wiring straight to the amp as well, and the binding posts can be used to hold wire hangers.

Thanks for all the input, certainly appreciated.

Dave

nicoch · « **Reply #14 on:** 29 Apr 2012, 05:47 pm »

HI Dave ,great work!

the front load look like a sort of Nelson Pass slot load ?

Ric Schultz · « **Reply #15 on:** 29 Apr 2012, 06:21 pm »

Dave,
If you just want to brace the baffle then you can run trianguated braces up each side. Google the Granada G2 speaker. You could run a similar brace on each side but not all the way up.....just to below the full range. This would be plenty of brace and the full range would not have any cavity resonance to deal with if you ran it all the way up. A heavier base with the braces would add more weight and the combo would be really rock!!! and at the same time not rock. You don't want the speaker to move....just the cones. 5 inches thick......with Green glue.....yikes! This is good!

Gothover · « **Reply #16 on:** 29 Apr 2012, 09:01 pm »

Quote from: Ric Schultz on 29 Apr 2012, 06:21 pm

Dave,
If you just want to brace the baffle then you can run trianguated braces up each side. Google the Granada G2 speaker. You could run a similar brace on each side but not all the way up.....just to below the full range. This would be plenty of brace and the full range would not have any cavity resonance to deal with if you ran it all the way up. A heavier base with the braces would add more weight and the combo would be really rock!!! and at the same time not rock. You don't want the speaker to move....just the cones. 5 inches thick......with Green glue.....yikes! This is good!

That brace I like alot, simple, and effective.

Dave

matevana · « **Reply #17 on:** 30 Apr 2012, 07:11 pm »

Hi,

Can someone please explain the science behind this design? I'm familiar with the concept of multi-volume chambers used with a single port (single reflex bandpass); just not sure what the design objective was here and how it was achieved?

Thanks much!

Gothover · « **Reply #18 on:** 30 Apr 2012, 10:28 pm »

Here is a link to the discussion that got me interested in the CS2.3 clone, that led me to this build.

http://www.diyaudio.com/forums/multi-way/148303-emerald-physics-3.html

matevana · « **Reply #19 on:** 1 May 2012, 12:44 am »

Thanks. I remember following that thread when it first came out, but the take-away seemed to be inconclusive. There were some heavy hitters contributing like Martin King and Earl Geddes, but neither seemed to add credibility to the concept. You commented on your ability to add spacers to tune the port. In your development, have you measured this against the same drivers mounted traditionally on a flat baffle or shallow u-frame? Thanks.