Yield Open-Baffle project.

[John Warren]

Tried a number of baffle configurations. From an equalization perspective, this was the most straightforward to correct. With the active network (24dB/oct bandpass with -6dB corners at 60-600Hz) the system will only require a +6dB/oct boost below 300Hz to negate the roll-off, nothing more. The low-frequency corner at 60Hz is to limit driver excursions to acceptable distortion levels given the size of the room and sound pressures anticipated. It also makes the configuration much less sensitive to room placement effects. A large, sealed sub will handle the last couple of octaves.

What makes these designs difficult is that the measurements first require true anechoic conditions to know where and how to apply the active network equalization parameters. In my experience, if the low frequency extension is limited, they can sound very good in a number of room locations.

Note the ETC for the above response! Microphone was M30 Earthworks, on-axis. Analyzer was CLIO FW,

Edited March 14, 2014 by John Warren

[ClaudeJ1]

A k-43 cast frame woofer has a Qts of 0.314 , how does that rate in the open baffle world. what's an example good qts number?

Not good. Look at the Eminence Alpha 15", it's the cheapest and best for OB with the least EQ.

[bracurrie]

I have had my Yields now for almost a year. Whether its hard rock or mellow jazz the speakers have performed beautifully. Bass is full and tight. The Audio Nirvana full ranger images so well that its spooky listening to musicians moving around in some bluegrass recordings.
When I purchased the speakers Justin sent me the passive crossovers that I believe ALK designed according to Dave Harris's active settings. The components tore loose in shipping which made them inoperable so I used an active crossover with Dave's settings to great pleasure.
My good friend Tom Brucker at High Tech Service here in Nashville finally got around to rebuilding the passives and I have been using the Yields with the passives for a week or so now. Wow what a difference.  The sound is more pleasing to the ear. Its hard for me to put my finger on it exactly but maybe they sound balanced.

[bracurrie]

Mdeneen - I tried to implement Dave's recommended 200 Hz low end 3rd order coupled with 400 Hz 1st order for the full ranger in my digital active software but couldn't get there. The passive's use those settings. 

[moray james]

Claude is right a couple of Alpha fifteens per side with no eq and you can make a lot of good sounding bass for very little. ///////there are a lot of OB fans at Pureaudioproject.com lots of experience with the builders there. For those who think that OB cannot compete with box speakers you need to reconsider. Some months back I was at the Toronto CES show with Rachel and Ze'ev in the Grant Fidelity Room. We won three Best Sound at Show awards and a hand full of special mentions. You can contact builders on the Facebook page to get ideas for your own projects. Builders there are working on some interesting projects. Best regards Moray James.

https://www.facebook.com/pages/PureAudioProject/421771601219967

http://www.6moons.com/industryfeatures/taves2014/3.html

Edited January 8, 2015 by moray james

[bracurrie]

 

Mdeneen - I tried to implement Dave's recommended 200 Hz low end 3rd order coupled with 400 Hz 1st order for the full ranger in my digital active software but couldn't get there. The passive's use those settings. 

 

MiniDSP?

The miniDSP is what Dave used. I used one when I ran a analogue pre-amp but because most of my music was in digital I simplified my signal path running one D to A with an Apogee sound card connected to a Mac running Pure Music. If I were to use a miniDSP I would have a chain of D to A - A to D - D to A.

The miniDSP is an amazing piece of gear but if your drivers are super efficient the noise floor is audible during quiet parts. The passive have the effect of pushing the noise floor well below audible even with noisier tube amps.

[erik2A3]

There are quite a few people using open baffles. Along with our split la Scalas, we also use a rear-loaded horn system that uses Lowther PM5A drivers. The PM5A, which is the second most powerful alnico-based driver from Lowther, is absolutely fantastic in an OB configuration. I had contemplated OB loading with Lowthers many years ago, and mentioned here on the forum an idea I had to...and this is going to sound crazy...mount the Lowther to the back of a toilet seat cover (a new one!!!) so that I could quickly and easily experiment with degree of slant. The problem with this is that acoustic roll-off would be at such high frequency that it would be difficult to achieve a good integration with the La Scala bass bin.

So, I made a larger panel out of MDF so that the Lowther would begin to drop out in the range of about 300Hz. I used just a single low-pass choke in series with the LS bass bin, and drove it with a 50 watt SS integrated amp so I could match the gain of the Lowther driver (which in this particular setup would have an efficiency of about 98dB).

It is very difficult to find a woofer fast enough to keep pace with the hair-trigger Lowther full-range drivers, but people have had good success using Klipsch bass bins from both the Klipschorn (which I have also used with Lowthers) and La Scala. In my case, the best sound I got with the la Scala was with the dog house turned around, facing the wall behind the speakers, and wired out-of-phase with the OB mounted main driver. I have not had many, as they sometimes say, 'jaw-dropping' audio moments over the years, but I have had a few; and the sound from this arrangement was certainly one of them.

The overall presentation was not one where image focus was a dominant characteristic. The sound was similar in respect to some large Martin Logan ESLs I once heard. Transient information was instantaneous and very clear, and the la Scala provided clean tight lower mid-bass response that was far better than the Lowther alone in its big back-loaded horn.

I have the OBs I made tucked away for now in a closet......remembering how they sounded as I write this makes it very tempting to set it up again. Lowther America, the primary Lowther distributor in the U.S. has been using OB systems for the English drivers almost exclusively for the past several years. They are a NOT inexpensive drivers, but are extremely good. Nelson Pass is very much a Lowther OB officionado, and has done extensive experimentation with them.

If so inclined, have a look here: http://www.lowther-america.com/page2/page12/page12.html

And here: http://www.tnt-audio.com/shows/burning_amp2012_e.html

Edited January 11, 2015 by erik2A3

[Guest David H]

My good friend Tom Brucker at High Tech Service here in Nashville finally got around to rebuilding the passives and I have been using the Yields with the passives for a week or so now. Wow what a difference. The sound is more pleasing to the ear. Its hard for me to put my finger on it exactly but maybe they sound balanced.

 

I am pleased to see you got the passives up and running, ever more pleased that you like what you hear.

 

Dave

[erik2A3]

Mark

The main reason I was on the lookout for a pair of split la Scalas had to do with my interest in using the bass bin with the Lowthers. A pair became available within a thirty minute drive, and I bought them for $1,000. Once setup, I liked the sound so much on their own, that I just sort of stopped thinking about the Lowther open baffle arrangement.

But one Saturday afternoon, after doing some on-line reading about OBs, I decided then and there to give it a shot; and within about two hours had the Lowther's removed from their rear-loaded horn cabs and mounted on the MDF panels mentioned above.

The 300Hz crossover is just an estimate that's very roughly based on the size of the panel I'm using, which is a bit smaller than the large OB shown on the Lowther America site. I wanted to run the Lowther full-range, with only a low-pass inductor on the woofer, and the value of the iron core choke I happened to have on hand would work ok in that frequency range. My guess is that the actual Lowther roll-off point was in the mid 200cps. This was of course just a quickly done experiment to give me a general idea of how the Lowther would work in an OB configuration. They did not have the same sense of image focus as when they are in their enclosures, but the very clear and open, and the manner in which the room was loaded (with the driver radiating from both the front and the back) was captivating.

There are actually a few OB systems I have seen on the market that were well received, as well as from smaller companies, one of which is Hawthorne Audio.---------> http://hawthorneaudio.us

Edited January 12, 2015 by erik2A3