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All British 3-way Open Baffle HELP thread

PastTechFan

PastTechFan

Super Member
So, here's pics of my (new to me): B&W DW13/4s, and Richard Allan CG10Ts, with some (earlier pick up) Super 3 tweeters.

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You know where I'm going with this.......!

Here's the plan:

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All credit to Troels Gravesen. It's his OBL-11, and homage to Brigg's Wharfedale SFB/3.

Now I've never built a speaker in my life. (No, I did make one in Industrial Arts class in 1968 using a 10" Jensen in maybe a one cubic foot sealed cabinet. So...., that was disappointing. Where'd the sound go?)

I'll post what little info I have on these drivers later (including some T/S info). The big DWs are ex-B&W DM70s. The RAs are new to me thanks to Audiozaz. My first pair of full rangers. Lovely sound. The Super 3s are quite polite. Never heard one outside of a cabinet. All are said to be about 92db. Which is good cuz, except for my 150wpc Adcom monster, I'm somewhat wattage challenged. Hope to use 12 -17 wpc tube amplification.

I'm planning a passive crossover. Not enough amps etc for active. Maybe cross the LF at 4-500 Hz, and the HF at about, what, 8 Khz?

Looking forward to comments, critique, suggestions, but we pretty much have to work with what I've got. No new drivers. This is all vintage, all British and, comparatively cheap. That is to say, I got some relative bargains (OK, the DWs were my personal best "scroe"!), and there ain't much more in the budget. Could maybe swap some EPI tweets in if that would help. I have those too.

Did I mention I don't fully know how to read a frequency output graph? OK, I get the X and Y axes, but why does an open baffle have a 6 Db slope (all by itself)? Fools rush in. :D

I have a buddy I hope will do the woodchopping. If these things come out sounding great then, GREAT! If not, I'll (further) re-purpose the b*ggers. I've considered cramming the DWs into my W90s, for some serious "pistonic" action. And I've got a few cabinets I can stuff (empty W60s, and some Utah Heritage SC1s).

But I've got to try the OB thing first. My audio assemblage of found objects.
 

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I posted some info on the woofers in a separate thread here.

http://www.audiokarma.org/forums/showthread.php?t=586634&highlight=dw13

They were in a sealed cabinet of approximately 105 liters (3.75 cubic feet?), described as an "infinite baffle". Somewhere I got the impression that a speaker suited for "infinite baffle" would be fairly suitable for open baffle. Hope I'm halfway right.

Here's the T/S parameters I grabbed from a german website (attached to my other post). This is for a (later?) version called the DW13/70BX. (for Bextrene?)

Fs (Hz) - 35.8

Qms - 9.42

Qes - 0.74

Qts - 0.68

Vas (litre) - 87

RMS (ohm) - 2.33

Mms (kg) - 90

SPL (dB) - 89.16

Bl - 10.01

Re (ohm) - 2.33

Now, the thing is, my 2 drivers measure 6.9 and 7.3 with my DMM, so is Re low? Also, my drivers aren't Bextrene, and they have been refoamed. So maybe these parameters have nothing to do with mine.


B&W crossed over at 400 Hz. Will post a copy of the (tiny) B&W service info on their crossover when I'm back at my 'puter.
 
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Three way OB's can be tricky at least for me they were.

I tried tri-amping but ended up bi-amping and running the tweeter off the mains with an active crossover. Now days I use just a main FR driver and woofers.

The part's cost of building a high quality passive crossover can exceed the price of an active crossover and amp for bass duty. Not to mention the effort required in building one that can only be used for one system.

An H-frame configuration can give excellent bass without taking up the floor space required of wide baffles.
 
Hi PG, thanks for your interest,

I've been following your progress on OBs for quite a while. Your H-frames look really interesting. I may eventually go that route, but hoping with the wider baffle, to keep the build very simple. So far, I haven't worried too much about WAF. More of a "proof of concept thing" just now (as cubdog would say). Truth to tell, I just want to hear some OB. Have only heard boxes, and these things on the bench in free air.

The Richard Allan 10" FRs sound especially nice.

Here's link to Audiozaz's thread about these very units:

http://www.audiokarma.org/forums/showthread.php?t=332390

he measured the t/s (average) as:

Re: 7.35 ohm
Fs: 37.5 Hz
Qts: 0.54 - (One driver has 0.50 and the other 0.59)
Vas: 114 liters -
Sd: 293cm^2
BL: 7.6 N/A - extrapolated by WinISD
SPL 92.3 dB/W/m - extrapolated by WinISD

The factory specs claim a range for the CG10T from 40 to 15K:

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Audiozaz posted some test results:

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In a PM, he suggested the following for the RAs in OB:

"Extra bass support is a good idea for these on an OB. I've never made any serious attempt at it, but I'd probably try to take the Xover point a bit lower for the CG10T, maybe down to 150Hz-300Hz with a 3rd order slope. As for the high frequencies, they make a solid ~8kHz on-axis. A small horn tweeter could be brought-in first-order around 10-12kHz I surmise. If going with a dome tweeter, maybe somewhere between 3kHz-6kHz would be a better spot."


I thought I could get a bit more out of the DWs, up to 400, but maybe not. I haven't yet listened to them together with the RAs (with a choke on the DWs).

Here's the B&W crossover info: 9.2 mH choke in series, with a 30 uf cap in parallel. If my googling is correct, this is a 2nd order Linkwitz-Reilly crossing at about 300? I can't make the B&W values make sense at 8 ohms. Maybe I shouldn't care.
 

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I'd suggest putting those 10's on a piece of ply or cardboard and listening to them naked for a little while and get use to their sound and where the other drivers help is needed.

If you don't listen all that loud, you might get away with not filtering them at all and just augmenting the lows and the highs. If so....then you might be able to just have a high pass on the tweeter to roll those in above that about 10-12k area.

Then for the lows, beg or borrow a subwoofer amp that has adjustable freq control and find where you want to roll in the bottom end. See if that really agrees with what you'd expect from the charted response.

With a few days of listening, you should be able to have in mind your targets based on what you like and hear in your room.

If you run into an active crossover and have multiple amps you could go that way. Even that doesn't have to be real hard. Can be a sub amp separately for the woofs and a high level crossover or HP filter for the tweets. Or all the way to 3 separate amps and full crossovers at each cross if you want to go that way.

But the efficiency differences are going to be key to getting the different drivers to work together.

EV3
 
Progress....

Well, no baffles yet, but I scrounged a couple of used crossovers, and used part of one to run the 3 drivers with a bit of filter.

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Used a 5.8 mH choke on the DW13s for a (1st order) lowpass roll-off at 220 Hz. Put a 100 mfd cap on the (full range) Richard Allans, for a 200 Hz high-pass, and a 4mfd for a 5000 khz highpass on the Wharfedale Super 3. A good start. Then, I put pots (not L-pads yet) on the RA and the tweet.

A close up my cobbled together bits!

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On the other channel I'm running a New Large Advent.

Wow! I can't believe the bass I'm getting in free air. The 3 loose drivers (together) hold their own quite nicely with NLA.
 

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Yeah, I know. Thanks for stopping by. (Tough audience) :D

SLOOOOW progress. Too much stuff to do. Gettin in the way of fun.

Even my wife likes the sound!. :yes: The Richard Allans are really nice.
Maybe another story when she sees the size of these things. Maybe eventually do a tri-amp active thing with H-frames a'la Poultrygeist at some point. Make little bitty baffles.

Big baffles first! Next week? Hope so. Even rough cuts.
 
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I like off the wall speaker design.

I've been working on a pair of 'cheap' acoustics from the shack and opened them up (secret stuff here).. to capture the woofer reflex mid's. the woofer is a solid as if it was still acoustic. These are smaller bookshelf but the diff is big when you go to hifi vrs. acoustic suspension stereo but my A speakers in this set up are acoustic suspension and I'm testing outdoors in the screened in porch.

I'm also trying to achieve an open speaker system more like an open frame but this will require larger enclosures. Like a speaker inside a speaker enclosure.. much like a modified console wall system but just the speakers. Another thing is to consider the room furniture. Larger wooden built in book shelves are frigging great enclosures! top shelves; mids and tweeters and bottoms for the lower mids and basso. Place simple wooden boxes with open backs on the shelves. Hell, all kinds of audio response capabilities!

One key I have found is I think I'm going for separate tweeter sections or a combo like 16+khz and above.. I want that sweeping transition.
 
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UPDATE Finally!

Sooo... in the intervening period I've learned some things.

First, despite the assurance of my master-carpenter and cabinetmaker buddy, I can't freehand circular jigsaw cuts. (Although I can make holes.)

Second thing, these big B&W woofers DO make bass. And the Richard Allans SING! Third thing, the FR (mid?) is too far away from the LF. Still, it sounds great!

So, as "proof of concept", this has been a great success! Still, I'm almost ashamed to show my first amateur OB attempt, after admiring so many of the others I've seen. But, "no pictures, it didn't happen", I know. So, without further ado..., mounted on 49" x 27" 3/8 masonite, my first OB build:

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I've only built one (although I cut two at once). I'm running it in mono (or stereo together with an Electro-Voice EVS-15B). I'm already planning my next pair, again 3/8 masonite, but 49" wide, by 33" high. I'm thinking a WIDE baffle, but with the speaks in a vertical (centered) alignment. With FR slightly offset.

Here's my rudimentary crossover.

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Just for fun, I'm bi-amping. Running the woofer with one (150wpc) channel of an Adcom Gfa7500, with a 5.8 mH choke, for a low pass at 220 Hz. The Richard Allan and Super 3 tweet are run from my Planar SR 2100. The FR has a 100 uf in series, to try to keep out stuff below 200. Finally, the tweet has a 4uf motor run, to come in at 5 Khz. I've got an Lpad on the FR and tweet, but I'm running the tweet wide open.

Not sure about my cross points at all, but I'm loving the sound of this thing. Now I can't wait to build one right!

Next time, I'll submit my speaker placement for AK comment before my cuts.
 

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Looks like a really cool project! Do those drivers need to be mounted on the back of the baffle? I always cover my shoddy circle cuts by mounting the drivers to the front of the baffle.

I know others have mentioned it but getting an active crossover and a couple amps (even a cheap avr from Craigslist or something) will make the whole process much easier and IMO will sound better. You could even get away with a 2 way (behringers are <$150) and a handfull of caps and resistors to dial in the tweeter and just run it off the mid amp. HF caps are cheap and quality inductors and caps alone for the low-mid xover will be more than an active xover and a cheap amp to to power the bass plus you'll have the flexibility to tweak it becaise you likely won't get it right on the first try and have to spend another $100+ on new caps and inductors!
 
Hi k-

Given the shape of the cast baskets, I don't think I could front mount these, except maybe with standoffs, especially the Richard Allans.

For my next build, I will definitely be using a circle jig, if only home-built. These will only ever be workshop or garage speakers. Although my wife says they sound good, she's not the slightest bit interested in seeing these things in our living space. Thankfully, my Wharfedale W90's have won her heart, and they play in the living room.

I think I'll go active at some point, but I'll have to cull the herd at some point, before there's any more audio. Amps, (or receivers) I've got, although (except for the mighty Adcom), each one wants some TLC of some sort or another (hence why they're in the basement).

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The current crossover bits are surplus items, and really just there to get some sense of the sound of these things. I especially don't want too much excursion on the FR (mid). Briefly ran it without an L-pad and cap, and it pulsed in and out on a funky bass line so much it scared me! Little bitty upgrades in the works for now. Easier to bring into the house/justify in the budget. (Likely "false economy", I know.) :scratch2:
 

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Hey man!

Uh, yeah I see what you mean about the whole hole jig needfuls. Personally, I'm really glad that you posted it. It's great when someone builds a speaker or restoration or whatever and posts something about it. You know the ones? "I built a super mega Honk 9000!" And there's a few pictures of the final product. I need to see the steps in between, the mistakes. The mistakes guide me to a good solution, nearly every time.

I went looking for some masonite today to make my jig, no luck yet. Stock was kinda funky, not right. I'll keep looking.

Biggles
 
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