Taking on the Slot loaded OB project...
A couple of months ago I reinstated my AV123 X-Statik and X-Voce speakers. These are a hybrid OB design with sealed woofer sections and the MTM on open baffles. They excel in the natural, uncolored and fast midrange as an OB should. Listening to these again got me thinking about how much I loved the sound of the two previous OB projects I created years ago. These include the huge and ugly Usher Audio D2 "clones" that I made using the same exact Usher 15HM drivers as the D2's as well as the huge and ugly H-frame subwoofers I made 9 years ago using four Pyle PPA15 drivers, two per channel.
There's just something about OB bass that no other speaker design can replicate, other than maybe an infinite baffle setup. I have been longing for another OB project for some time, and listening to these X-Statik's have turned up the heat once again for a project.
As I was browsing around in the Google Images for OB's, I stumbled across the thread on this very forum about Nelson Pass' slot loaded project. It is an extremely interesting design that I feel can be made fairly compact and still produce good results, keeping the same baffle dimensions as NP's, but folding them to make a somewhat narrower frontal area. It won't be a traditional "wing" design either.
I made one post in the NP thread about the fact that I had just ordered twelve 12 ohm 8" Peerless India drivers for this project. They will be here tomorrow sometime. Funny thing about it is that these AV123 speakers of mine also use Peerless India drivers, though the 6" versions with cast polymer baskets. The 8's that I ordered have stamped steel baskets. If these 8's are anything like the ones in the X-Statik, these are going to be some decent little drivers, especially at 5 bucks a pop!
I'm waiting to hear back from Nelson Pass via email about these particular drivers and the slot loaded OB. He's also ordered a few of these same drivers, so maybe he's working on them as we speak and taking some measurements. I hope so.
In the meantime, I'm looking at all my options for the top end. I have looked at Dayton's 8" PS220 and TB's W8-1772. The Dayton is said to have a really screwy freq resp and that it needs a lot of correction circuitry to make it usable. I don't want that. The TB's are really nice units that I have read perform very good as well, but they are a bit pricey at $250 each.
I've also considered going with coaxial drivers such as the 8" P-Audio similar to what Danny from GR-Research uses in his V-2 OB's. I've looked at the Hawthorne Silver Iris 10 as well. This is a good buy as it's $160 as a complete package with crossover per channel. The only issues I have with these are the fact that they are two drivers with a crossover.
I have been a fan of Fostex drivers for several years now as I've had two different ones over the years, the totally stock and well broken-in FE103E's that I still use today and a fully tweaked pair of 107's from Dave (planet10) that I sadly sold a couple years ago.
Anyway, I have just been offered a pair of unused FE206E's from a member on another forum. Even new, these are only $200 a pair and I'm sure I could probably get these from this member for a fraction of that. This is the way I think I want to go, keeping this project as cheap and simple as possible. I would like to get some impressions of the 206 driver from members here as far as how they sound on an OB from say 120-180Hz on up. I think this is were I probably want to run the crossover at, maybe lower, maybe a touch higher.
In keeping things cheap and simple, I can do this project two different ways...
1) Build a 2-way passive line level crossover circuit to pass the signals to the low and high amps.
Pull out my old AudioSource AMP100 and use it on the Peerless woofers, six drivers per channel. That's 50 watts at 8 ohms. More than enough power for these drivers.
I would then use my Monarchy Audio SM-70 Pro to power the 206's. That's another 40 watts per driver. Again, more than enough power.
I could use the Monarchy amp on the woofers and use the new Dayton DTA-1 Class T amp on the 206's which I have tucked away in the closet.
2) Run everything off of the Monarchy amp and just run a typical passive crossover network on the speakers.
Now the Peerless drivers are rated at 91.5 dB at 1w/1m and the 206 is rated at 96 dB at 1w/1m. I'm a little rusty on my series/parallel calculations when it comes to overall efficiency, but I'm thinking somewhere between 96-99dB possibly. If this is anywhere near real world numbers, I would not have to pad down the 206 at all. In fact, I might have to figure out a way of padding down the woofers as it might become too bass heavy.
Oh, one last thing... I do NOT want to use any EQ and keep the passive circuitry as simple and minimal as possible.
Your thoughts please and many thanks in advance! ;)
Those appear to be nice drivers, and at 5 bucks with free freight I couldn't
resist. I'm sure we all will be interested to see where yours go.
Does the 206 go lower in a small sealed box or on OB baffle?
I'm still waiting on a email back from you, hoping you may have some answers about these drivers actually as there's no measurements of them anywhere to be found. I'm sure I can't just go and throw them on the baffle and hope for the best... Although, I have done that in the past with a certain "clone" speaker attempt. :shhh:
So any suggestions on an 8" fullrange driver?
So far, these are options that I have no clue about their sound, and about the price limit I am willing to spend at this point. They range between $50 ea all the way up to about $130 ea.
Audio Nirvana Super 8 Cast Frame
Audio nirvana Super 10 Cast Frame
Wild Burro Betsy
Wild Burro Betsy-K (more efficient)
Visaton B200 - I have this one separate from the list because I'm not sure of the price or where I can buy them. I think they are a bit high though, possibly around $200 each from what I saw somewhere on the net... I think.
Keep in mind, these will be going on an open baffle and crossed over upwards of 100Hz, and possibly up to 200Hz, but I doubt it. I don't want to extend the Peerless woofers to the point of getting the resonance of the slot active.
If you guys have any other 8" fullrange suggestions, please feel free to let me know. As long as the price is within reason, I'm willing to entertain those options as well.
>>> I don't know, but I don't need it to go any lower than about 100Hz at most on an OB.
I don't think any of the drivers you mention will hit 100hz on open baffle.
Some may reach 100hz in a sealed box but i'd have to sim them.
But these two approaches will offer a different type of sound (each having their supporters).
Have you considered going with a smaller Fostex driver?
An 8" driver may be too efficient for your slot loaded bass drivers if you are using a passive style of crossover. If you only need response down to 100-200 Hz then the FE-108E Sigma. FX120, or the FF125WK would all be nice. If more efficiency is needed then consider the FE-126En driver. For more efficiency step up to the 6" versions in the Fostex line of drivers. These will all probably be smoother on the top end compared to the 8" options.
How much efficiency, the slot depth and cavity dimensions, baffle size around the slot, the OB size and shape, and the crossover points need to be calculated carefully to get an optimum balanced SPL response.
I would like to step up to larger drivers this time around to keep the crossover point as low as possible, giving the fullrange driver the lime light.
As far as the slot efficiency, I don't know. There will be 6 drivers in each, rated at 91.5 dB per driver. I'm not too certain what that comes out to once you have them all wired up series/parallel for an 8 ohm load. I recall reading somewhere an estimated 96dB with the Vifa's Nelson used in his OB. I don't know if the Peerless drivers are more efficient or not.
Speaking of which, I just received the Peerless drivers today and two of them have minor damage due to very poor packaging from PE (shocking). On one, the cone is separating from the surround and the other one has a small cut in the surround. One other driver has a few scuff marks on the cone from the top four drivers just bouncing around in the box. After getting off the phone with PE, they are sending three more drivers for free, as well as allowing me to keep the damaged ones.
It has been decided that for the slot loaded woofers, I will be purchasing a pair of Danny's (GR-Research) SA-1 plate amps to power them. These will provide the adjustable low-pass crossover as well as a gain circuit, 20Hz high-pass circuit and more than enough power.
As for the top end, that's still up in the air as to what to go with. Danny has something up his sleeve and I am to call him Monday about it. In the end when I have the money, I will be going with his V-2 top end kit with matching crossovers. But for now, I'll be going with something a little cheaper, actually a lot cheaper. We'll see what Danny has to say on Monday.
Don't wait for me - sometimes it takes me so long that the drivers are no
longer available by the time I have more information.
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