Building the simplest speaker in the world: Open Baffle Single Driver

[li0012in]

I recently got a new place. New place means new speakers...YEAH

 

So, I decided to lean in, take a big leap of faith and went for the simplest speaker in the world- Open baffle, single 12" Aucharm full range.

 

IMG_20170326_172257 by calvin lin, on Flickr

 

The baffle

This baffle was ordered in 20mm thick (thin) finger jointed pine plank. You can say form took over function here...but finger jointed pine are really nice looking. Obviously, the carpenter was ???? on why somebody is ordering this. No reinforcement or stiffening member. Just a plank and a big hole.

 

IMG_20170325_213314 by calvin lin, on Flickr

 

The baffle is 1.2m x 0.6m. Driver cut-out at 0.8m height. I had tried various simulations, XLBaffle, Edge and Boxsim. However, reality is that the 1.2m x 0.6m is about the largest I can go in my tiny apartment. 0.8m for driver is about where I think my ear level will be.

 

Next step is finding some legs to ensure my baffle can stand up...

 

Aluminum leg brackets

Unlike those fanciful projects where wood bracing and leg stand are used, I decided to go for Aluminum leg stands. The reason being this is experimental. I wanted as little throwaway cost as possible, should this project goes wrong. I used 2 pairs of 16 inch Al brackets for the rear and a short 12 inch L bracket to prevent the speaker from falling forward.

 

Measuring and preparing to drill the bracket screw holes...

 

IMG_20170326_174138 by calvin lin, on Flickr

 

Legs assembled...

IMG_20170326_170129 by calvin lin, on Flickr

 

Driver mounting

Having a single driver without any crossover meant that mounting was super duper easy. Although I must say these 12 inchers are quite heavy.

 

Drilling holes for the driver mounting...dremel hard at work... (of course, the procedure was simplified here: Place driver in, do markings, remove drivers, drill holes, add rubber washer, screw on)

IMG_20170326_181654 by calvin lin, on Flickr

IMG_20170326_181149 by calvin lin, on Flickr

 

Done! Test and repeat for second speaker...

[li0012in]

First impression

Setup: PC -> Style audio Ruby 2 DAC -> Pioneer VSX 635S amplifier -> Speakers

As this is a new place which I have not shifted into, I could only make do with whatever I had brought over to kill time. Most entry level equipment will probably outshine what I used. And it was a messy room (which probably helped to damp the room).

 

IMG_20170326_183208 by calvin lin, on Flickr

 

Tone: I was a little surprised. The Mid and High were really good. I have tried multiple single driver setup (Lowther in transmission line/backloaded horn, Loth-x, Omega TS-1) and I always thought that the HF are lacking a little in those. The Aucharm was nothing like that (and I honestly, didn't expect it to be this bright). It sounds almost as if there is a proper tweeter. If I were to Nitpick, it does seems shouty at times.

Problem was in the bass, it wasn't just lacking, it was missing!

Playing with EQ on PC shows that I need compensation of about 3dB at 154Hz, 7 dB at 77Hz. Oddly, there was NOTHING at 55Hz and below. There is some occasional 100-150Hz boom. Weird.

 

Soundstage:These speakers are very sensitive to positioning. As I found out, Toe-in compresses the soundstage and make the speakers very shouty. They are better when almost parallel to the wall. I ended up with a distance of 0.55m from rear wall and almost close to the side wall. My listening position was about 2.2m from the speakers. The speakers sound great inside and outside of the room. The only time it sounds weird is when you are seated down at the golden spot. Three major issues with the soundstage:

1. Lack of height

2. Width, average wide, but it only had left, center, right.

3. Very forward sounding

 

Clearing the room of the items didn't help. Burn in didn't help. Maybe try a proper amplifier? And I did.

 

Second impression- Tube amp power

Reluctantly, I carried my old Opera Consonance M100S plus tube amp to my new place, 20kg? 25kg? Not sure. Anyway, this is a 300B push-pull integrated amp, using 6SN7 as drivers and 12AX7 as input. And WOW. It transformed the speakers.

 

IMG_20170408_133054 by calvin lin, on Flickr

 

Tone: The amplifier change partially cured the "shouty" issue I was having. It is almost not noticeable now. Highs are still great, but because the shout is cured, I am starting to recognize some minor missing detail in the high. Those little details are there, but just seems a little softer than on my system at home.

Bass, much improved. So much that I had to dial down the EQ setting. However, it still wasn't ok without EQ. Bass below 55Hz can now be heard.

 

Soundstage: All issues fixed. The soundstage has moved to behind the speakers. There is decent height. And the speakers practically disappear. Of course, with these fixed, I start to notice the slight lack of soundstage width. The width is good by normal standard, but it is not wide. I am not getting width beyond my speakers. I am suspecting a DAC change will help as I have always been pretty disappointed with this DAC.

Next Step

It seriously needs a pair of helper woofer and these are already ordered. Also ordered inductor of 5.0mH and 7.2mH. The plan is to put the 15 inch woofers are pure helper woofers that comes in at around 100Hz, 1st order. The Aucharm will continue to be run full range. We will see how it goes when the parts arrive next month...

 

[wizardofoz]

here http://www.linkwitzlab.com/What_is_new_at_linkwitzlab.htm has a good amount of info on OB designs and especially on bass issues too

[fishball79]

Those open baffles do look quite elegant in its simplicity... keep us updated when the bass woofer is installed :)

[DIYer Straits]

Yay! Another FAST convert-to-be! Well done.

 

You have to really toe these guys in drastically since the highs will beam narrowly from the whizzer cone.

 

You may also need to put in a Baffle-step compensation circuit based on your in room measurements and the width of a the baffle, to even out your frequency response. This may have caused your slightly recessed highs.

 

Have fun!

[Guest ghemml]

Wah... I saw a 300B amp sia.....

 

Some cheap and dirty way for a woofer to work for bass in open baffle...

use at least a 8mh inductor parallel with a 100uf to 120uf capacitor..

 

And you need a decent amp with decent output wattage

[alsonkguan]

Arh.....open baffle, I have listen to afew from the forumer here, tried it but it wasn't successful as you mention 100hz-150hz that's it. Good luck in trying out a woofer keep us update please...

[wizardofoz]

My OB LX521 or Orions can push the bass...it takes active crossovers and drivers with adequate Vmax capability as OD needs to push much more air to compete with box designs but IMHO sound Sooooo much better.

 

 

Cost a lot more but take up less room than your setup I think

[wechnivag]

Nice open baffle, simple and elegant design. What 15in drivers are you going to use?

 

Sent from my X9009 using Tapatalk

 

 

[Retrotube]

Hi Li0012".

 

Congratulations to you on getting your new place!

 

Not intending to rock your boat, my comment may be slightly out of topic.

I have this to share. I tried several types of 300B's. And in my context 300B tend to sound like a rising slope frequency response. This characteristic gave it a loss of bass type of sound or "shouty"? as you described it. I had an amplifier that can be run on 300B or 2A3 output tubes, with a some re-wiring. I really liked the 2A3 output tube version for its better tonal balance compared to 300B version. As control for this simple comparison I had tried on 2 types of 2A3 and 2 types of 300B, really cheap affordables hehe. For my preference the 2A3 always sounded fuller.  I don't mean you should mod your current beloved amp. Try borrow a friend's amp that uses the 2A3 to see how far it can really go with your OB speakers.

 

I.m also quite curious about your intended subwoofer!

[Guest ghemml]

Rising response is due to baffle loss, or baffle diffraction. Just need a baffle loss filter to EQ it. Simplest way is to add an inductor and a resistor in parallel.

[li0012in]

I had originally bought a sets of 15 inch Suiny Pro (some China OEM) woofers from Taobao, to be shipped into Singapore via Air. Unfortunately, the crazy forwarder shipping cost (as much as the woofers!) meant that I had to forward everything back to my regular sea-shipping forwarder. At this moment, my woofers are still sitting at warehouse in Guangzhou. Will be a while.

 

While waiting, I got yet another set of woofers from another China OEM vendor. Also has been sitting in Guangzhou for 2 weeks now. Haha.

 

Did some simulation with BoxSim using the driver data. My crossover design is really very simple, a single 7.2mH inductor in series with the woofer, i.e. a 2 way 1st order crossover without the high pass cap. Would have added a high pass if the full range was smaller. Not sure if it will work, but we will see.

 

response by slow_poke_driver, on Flickr

 

Green line = Woofer. Blue line = FR driver. Black line= combined. BoxSim simulation also confirms my initial observation that anything below 150Hz will need some help, either via additional driver or some sort of Eq.

 

[Guest ghemml]

You should have got the Eminence 15a which has a high qts for open baffle and its available locally.

[li0012in]

  On 30/04/2017 at 6:32 AM, ghemml said:

You should have got the Eminence 15a which has a high qts for open baffle and its available locally.

 

Any idea who carries the Eminence locally? How much? Could be a backup plan.

 

I had originally considered getting the Eminence Beta 15A. However, the response curve of the Beta 15A shows a 10dB peak at 2KHz region. Wasn't sure how it was going to be with a 1st order crossover, so ended up getting some other driver. Not sure if it will turn out right or wrong. Haha.

[Guest ghemml]

  On 02/05/2017 at 11:21 AM, li0012in said:

 

Any idea who carries the Eminence locally? How much? Could be a backup plan.

 

I had originally considered getting the Eminence Beta 15A. However, the response curve of the Beta 15A shows a 10dB peak at 2KHz region. Wasn't sure how it was going to be with a 1st order crossover, so ended up getting some other driver. Not sure if it will turn out right or wrong. Haha.

 

Try Martin Electronics at Burlington square.

[wechnivag]

Try this too, some drivers in stock.

https://woodworkzsg.myshopify.com/search?page=2&q=Eminence&type=product

 

 

Sent from my X9009 using Tapatalk

 

 

[li0012in]

After two weekends of grinding/drilling/gluing/fastening...finally done!

 

IMG_20170527_141240 by slow_poke_driver, on Flickr

 

Testing out the crossover configuration now. Built photos and details to follow...

 

 

[Calvinlin]

Thread digging and happy to report that the speakers are still with me!

 

Lost my xtremeplace account. Was searching for info on Martin's 2a3 300b...and saw my photos on Stereonet! And I registered a new account anyway because I couldn't view threads without registering! What happened to xtremeplace?

 

Settled on 2nd order crossover in the end. Also had to add U frame baffle for the woofer driver.

 

A few tube amps came and go over the years... Didn't find the correct amplifier. Still searching. The best was a pair of Audiospace EL34 mono blocks, but it just didn't have the finesse or mid range of the SET. I don't know how to explain, it was very musical, very balanced, soundstage was great in depth/width, very good drive, punchy well controlled, sufficiently detailed...but just hifi ish sounding and not natural. It sounded like it was designed for audiophile music to impress at a showroom.

 

5yrs later, I moved, just like any young sinkie who got trapped into BTO at a younger age without thinking. Last photo I had before moving...

 

 

The speakers moved with me to the new place and as usual, super slow to set up. Haven't even got the turntables out of the box 10months later...as you can see, even the laptop for music streaming is still on makeshift rack which used to hole my cable stash. 

 

 

It sure sounded better in my old place. Much much fuller. 

 

And one thing I learned is that toe in is super super super important for these big driver with whizzer cone, otherwise the soundstage is diffused or it can get shouty.