"inexpensive" open baffle

[knifeinthesink]

Hi all.

Love open baffles, would love to build an Orion or Arvo, but cant spend that much money. Ive looked at other projects, but I havn't seen anything that suits me. I've decided to jump in using some low cost hi value drivers and see what happens. Worst case scenario, I use the drivers for boxed speaker projects that are already well documented. So....

My loudness requirements are minimal, space is medium size (filling the room adequately with some 3" full rangers at the moment, except, of course, there is no bass). Appearances are a complete non issue.

My current plan is to use either two or four dayton da175s in an MTM or MMTMM configuration, partly for cosmetic reasons. Im up in the air about the tweeter but it will be cheap. A dayton tweeter in all likelyhood.

The closest thing to what I have in mind is the linkwitz prototype

Here are my concerns:

1. How to equalize the 6db roll off. Of course I dont have measurements yet so Im not looking for componant values but will eq be a fairly easy thing to implement? I dont know any eq circuits and Im not sure where to get them. My gut tells me to use extra drivers to fill in the frequency range that is down, but Im not sure.

2. Im assuming there will be a hump around 400hz or so and a null a bit further up. Is this going to be a major problem to deal with. I dont really understand how this is dealt with in existing projects.

3. Aside from the excursion limitations, Im not sure if there is anything about the drivers Im looking at that makes them unsuitable for the project.

To be clear, Im not trying to make this the greatest speaker ever built, but rather, to be open sounding, reletively neutral (ie. boxless) and educational. If this works out, Ill refine the design. A pair of 12" drivers will likely be added later on.

Im not interested in buying a digital XO. Ill use parts from a nearby surplus shop while Im experimenting.

I have looked at Linkwitz' site in detail, but the answers to my questions are over my head.

Thanks in advance.

David

[AJINFLA]

State your entire speaker "system" budget clearly. Then the responses can be more relevant and clear cut.

cheers,

AJ

[BobEllis]

AJ has a lot more open baffle experience than I do, but getting bass out of open baffle DA-175s will be a challenge. At only 4.25 mm xmax, there's not a lot of displacement to play with, even if you use 4 per side. Plan on a wide baffle, and even then you'll want to cross to a woofer fairly high.

As long as you realize how limited your output level/bass extension is, it might be an inexpensive way to experiment with open baffles. Add a woofer soon and enjoy it full range.

[knifeinthesink]

thanks for the quick replies.

Budget: Im aiming for something under $300 for now. The project will expand with a proper bass section a la linkwitz h woofer later but thats not part of the current budget.

Im already planning a large baffle with angled sides. Big is ok.

[Dennis H]

Linkwitz's prototype page has some inexpensive projects that will give you an idea what's involved with designing a passive crossover and a passive line-level EQ.

http://www.linkwitzlab.com/proto.htm

[knifeinthesink]

I've looked at those very closely. The questions I've posted are those Im not able to decifer from the available information. Im not interested in that particular project, in part because I dont want to spend $60/driver.

Im already planning to use a fourth order xo between the tweeter and da175 at around 2000 hz give or take a bit. Theres some substantial breakup from the aluminum cones that will need to be dodged. Ill run a proper simulation once Im commited on drivers.

[ThomasW]

How about looking around for a more forgiving driver? Doing that you'll save on the XO parts, and savings could applied to buying better drivers.

[Rene D]

I've been looking into doing an open baffle design as well, if not just something to play with. Found these on the madisound sale page. Looks like something worth playing with. If not just for the fact they're cheaper than dirt!

http://www.madisound.com/cgi-bin/index.cgi?cart_id=2298482.21932&pid=1902

Rene

[AJINFLA]

These were certainly less than $300, including the amps, utilizing the Madisound sale page also.
That's not what I'm recommending however LOL.
I forgot to ask Knife 2 things. Shipping/tax, etc is not included in the budget correct? Can you measure?


cheers,

AJ

[knifeinthesink]

That budget is just a ballpark number, so I could live with spending abit more.

Yes, I can make measurements, although Im inexperienced.

[JRT]

I suggest that you take a close look at John Kreskovsky's NaO Mini sat/sub combination.

http://www.musicanddesign.com/NaOMinidiscus.html

[knifeinthesink]

I wonder if the frequency response for those foster drivers Rene pointed out is accurate. They look pretty well behaved. Seems to good to be true. I think I will buy some though cause they are awefully cheap.

Thomas,

when you say "more forgiving" are you referring to the breakup and low excursion? Can you suggest any drivers? I had a look around and didn't see anything that jumped out at me. Having said that, most peerless drivers I've ever looked at had remarkably smooth FR curves.

[knifeinthesink]

Thanks JRT! I didn't know these existed. I've seen the Nao, but I havn't been to the site in quite a while. I was actually leaning toward exactly that type of design.

[ThomasW]

Thomas,

when you say "more forgiving" are you referring to the breakup and low excursion? Can you suggest any drivers? I had a look around and didn't see anything that jumped out at me. Having said that, most peerless drivers I've ever looked at had remarkably smooth FR curves.

I'm referring to cone breakup modes. It's literally been years since I paid any attention to anything other than metal cones, so I'm out of the loop as to what's popular or even available in the world of paper or poly. Just look for the smoothest plot you can find....

[JRT]

I'm referring to cone breakup modes. It's literally been years since I paid any attention to anything other than metal cones, so I'm out of the loop as to what's popular or even available in the world of paper or poly. Just look for the smoothest plot you can find....

Check out the Nomex cones on the Peerless Exclusive line up, which seems to split the difference between what is often exhibited by metal cones and paper cones. The Exclusives seem to exhibit a little more inband resonance than a good metal cone, but less than is exhibited by many paper cones. And the breakup is a little worse than many paper cones, but much less worse than most metal cones.

I think you will see what I am referring to if you compare the data sheets of the similar sized Seas CA18 paper, Seas L18 aluminum, and Peerless 830883 Nomex.

http://www.seas.no/seas_line/woofers/H1215.pdf

http://www.seas.no/seas_line/woofers/H1224.pdf

http://www.tymphany.com/datasheet/pdf/pl/830883.pdf

[ThomasW]

Check out the Nomex cones on the Peerless Exclusive line up,

Some how I don't think they're in his budget..

[JRT]

Some how I don't think they're in his budget..

There is that ugly "B"-word...

Upthread he indicated some flexibility in that.

[MJKing]

Have you thought about using one of the Fostex full range drivers, maybe a FE-167E, and a 15" HE woofer crossed over someplace between 100 and 200 Hz? Would not be too expensive and I have to believe very nice sounding. I think a full range driver and a big woofer makes a lot of sense. Baffle could be 20 to 24 inches wide by 40 to 48" tall with a pair of hinged wings. Simple, hard to screw up.

[AJINFLA]

Yes, that budget causes quite a bit of difficulty building a dipole. I'm not real fond of the monopole bass with dipole mids solution. Sorry. I need the dipole radiation to extend into the 60's to be musically satisfying.
This would stretch it a bit, but here's my suggested ingredients for such. Keep in mind also, that John K's requires a pre/power combo for the midbass eq, this you could use with your receiver.
These TM-1's http://www.ascendantaudio.com/Arbiter_TM.html are $160 for a set of (4) drivers. A midbass with 11.5mm xmax is more what I would consider "dipole friendly".
A pair of these http://www.ikesound.com/product-product_id/4767
would run you $120. This amp http://www.mcminone.com/product.asp?...Fid=50%2D6266A will set you back $50. Yep, we're over 300 bucks already with no MT xo components, wood, shipping, etc. LOL. But still within reason. More importantly, its a bit future proof if you decided to go fully active, expand your SPL capability, etc.
i.e, add a 2nd midbass (same unit), 2nd subwoofer (ditto), etc.
Where it becomes complicated is measuring and putting all of it together.
I did some sims using Thorstens baffle program, an approx 48"h x 14"w (1200mm x 350mm) baffle might be the way to go. Midbass mounted centered about 40" up(1000mm) yields a (dipole) roll off slightly below 200hz, coupled with the passive 125hz (8ohm) hi-pass on the amp, the (4ohm) Ascendant should roll off steeply enough below 200hz(ish) where the amps adjustable 12db low-pass should give you a reasonable midbass/sub crossover (without having to spend extra $ on XO/midbass eq parts). Far from perfect, but the B word looms large. I'll let your mic decide exactly what frequency to low pass.
The JBL's could be mounted close to the bottom of the baffle (again, Thorsten sim to guesstimate FR, 4' out from wall), say 10" up.
The amp would power both (sides) in mono - wired 1VC each, in series (4ohms), with the 2nd coils left open. The amp has a built in bass boost (5db @ 35hz) that can be adjusted upwards, to say, 60-70hz. I swore there was a tutorial on PE, but I can't find it. Perhaps someone here still has it.
You'll have to do all the real world measurements (like where the dipole peak(s) are) to make it all work LOL, but that's the "DIY" in diy.
Not the greatest speakers on earth, but something I could probably live with.
If I only had about $300 or so to spend. I'm tired now, good night .

cheers,

AJ

[Dennis H]

That budget is just a ballpark number, so I could live with spending abit more.

Well, it looks like SL's proto MT or maybe the MTM would fit in your $300 budget just fine so I'm not clear on why you consider them too expensive. As Thomas noted, when the budget is limited, using forgiving drivers like the Vifa poly cones will reduce your crossover costs. Crossovers can easily cost more than the drivers if you are using unforgiving drivers. If you don't like poly cones, the Vifa paper cones should be a decent substitute with very little crossover modification. Bottom line, if you want good sound, go with a proven design unless you feel qualified to design your own.

[knifeinthesink]

Thanks for the suggestions.

AJ - interesting idea. Those acendant drivers look like a pretty good find. I think Ill try them out but with a different tweeter. Seas tdfc maybe.

[AJINFLA]

I don't know if you've seen these ,http://www.adireaudio.com/Files/DDRDipoleDesign.pdf but the ascendants sweep as much air for less money. I'm not fond of MTM's (or poly's LOL) either, so I'd lean more towards a 2.5 with the SEAS if you want the NaO mini/DDR type design, or better yet use one ascendant and the JBL like I suggested and have plenty of bass for moderate level listening without going anywhere near xmax. Not a party speaker, but for acoustic instruments, etc.
You can always add more of the same drivers & amp as the system grows.
Which it inevitably does :W .

cheers,

AJ

oh yeah, the specs for the JBL in case you hadn't looked http://manuals.harman.com/JBL/CAR/Bo.../GTO_1202D.pdf

[dlneubec]

I just got my NaO Mini's up and running last night. Mine are customized to be MTM's that site on top of stereo subs that I already had. I have to replace an amp, so only one sub is working at the moment, but I should have that remedied early next week.

I've done a little bit of listening and am very, very pleased with what I hear, even with only one of the subs working.

Also, I found John K. is a real pleasure to work with. He's a great guy, who will go the extra mile to be sure you are satisfied.

Here are a couple links to photo's of mine.

Images not available

Good luck,

Dan

[knifeinthesink]

those look nice Dan. I saw pics of them on John K's site.

AJ - I've read some concerns over the health of ascendant audio. Any idea if there is anything to that.

Why dont you like MTMs? I would have gone that route but Im curious to hear what you have to say.

[MJKing]

I worked out an inexpensive OB design for somebody on a different forum earlier today based on my idea posted above.


Full range driver = Fostex FE-167E or 166E, each is 94 dB efficient ($63 each)

15" Woofer = Eminence Alpha series 15A, each is 97dB efficient and Qts = 1.26 ($58 each)

Crossover = Behringer CX2310 ($90)

XLR Cables = six required ($50)

Total Cost = 2 x $63 + 2 x $58 + $90 + $50 = $382 plus wood.


OK, after playing with my MathCad OB worksheet for a few minutes, here is what I get for a response.

http://www.quarter-wave.com/OB_2_Drivers_5_09_06.pdf

This is a 40" tall and 24" wide baffle, looks pretty good to me.

[AJINFLA]

David,

please don't dissuade yourself from something because of my opinion on the matter. I have a strong preference for controlled, uniform radiation in all directions. MTM's have very non-uniform vertical radiation - as do any non-coincident driver arrangements. That is why many here favor very low xo points, whether it be by steep filters (like Jons Cauer) or waveguide low frequency enhancement, or both. I prefer coaxial or coincident driver arrangements, but these too have their own issues. I just choose to make my compromises based on this format. They do not have to be your own.
As far as Ascendants health is concerned, I have no idea.

cheers,

AJ

[knifeinthesink]

I was just curious to hear your argument. I wouldn't go so far as to say I have a preference because I dont know all the pros and cons of each configuration. I confess that being a visual/creative person, part of the appeal of MTMs is the visual symetry. I want to eventually build every common type of speaker configuration so I can say from experience what my prefences are, but Im far from having that experience base to make judgements from. Your explanation was useful in this context.

I like your design suggestion because the XO design problems it will present are about the level I want to be tangling with at the moment. I think I can wrap my head around most of whats important in the XO that would be required. Price is decent too.

I also like Martins approach, but the last speaker I did was something very similar, to very good effect I might add, and I'd like to try something with a tweeter/mid XO for learning purposes.

[knifeinthesink]

One more question. For low sound output levels, do you think I can get away with 7mm xmax with two 12inch woofer in an Hframe. I know its far from ideal but the Dayton DVC 12" drivers are a hell of a deal and, once again, can be used in other projects.

Please keep in mind that Im not as picky as some people here or as I might be at another time. If I run out of excursion once in a blue moon when something blows up in a movie or the whole freaking gigantic orchestra goes double forte in a mahler symphony, I wont be upset. I just want to avoid wholesale failure ;-).

I think for now, Im going to start with a Linkwitz H frame woofer, and use it in tandem with a three inch full range I've been using, which Ill roll off at about 400 hz or so. I've done this before with quite satifying results. Then Im going to tackle the mid and treble. The poly drivers recommended by AJ are a possibility as the value seems excellent but the retailer has so far been difficult to get a hold of so I might pass on them.

2 RS180s might be my choice for a couple of reasons. The quality is there, I can use them to try a whole pile of box speaker projects, the price is excellent, and the excursion, while not as impressive as the ascendant drivers, is still pretty good.

If my dipole project doesn't work out the way I want it too, I can build the Nat P's which I would have built if I just wanted to build a good speaker without experimenting.

Thanks everyone.

[Jonasz]

I think you can use them to start with at least. The original Linkwitz Phoenix woofers used dual Madisound 1252DVC (0.5" xmax p-p) before they were replaced by the more potent and lower distortion Peerless XLS12.

[Dennis H]

I'd go with the Dayton RS. It's only a few bucks more than the DVC and it's a HUGE step up in performance. If money were really tight, I'd take a single RS over a pair of DVC although a pair of RS would still be the first choice.

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=295-464

[dlneubec]

Dennis,

I believe he is talking about the other 12" Dayton DVC, which has 7mm Xmax at $40 each,
SD315-88
not the 12" DVC with 15mm xmax at $110 each
dvc310-88
That would be quite a financial step up to the RS's at $90 extra each.

Dan

[Dennis H]

Ah, gotcha. $33 on sale. :T

[AJINFLA]

The fly in the ointment there is "H-baffle" & "400hz roll off". Those two don't jive.
If you need more displacement than the JBL and don't mind a wider (16") baffle these are tough to beat for the $ http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MEWA:IT
However, 400hz negates the use of the plate amp only, so a passive XO is in the cards. You could use the plate amp (with the 5db@35hz boost) to drive the 2nd coils in mono below 100hz. The low sensitivity might be a good match for the 3".

cheers,

AJ

[knifeinthesink]

Ok. The three inch thing was just a way to get something going while I made up my mind about the rest.

As it turns out, Ascendant audio did call me, and in fact, called three different numbers until they got me because my phone signal broke up and they couldn't quite make out one digit. This removes the major reservation I had about buying their drivers. They were also quite helpful in recommending shipping methods to Canada, which is great since brokerage fees can be a killer if you go with the wrong shipper.

I WILL be buying four 6.5 poly's from them.

Once I have drivers and can make some measurements Ill post. Ill put some thought into the bass issue but it may be less pressing with two 6.5 inch drivers a side with a ton of excursion. I may try linkwitz prototype line leve eq circuit first and then try AJs suggestion, which appeals to my way of thinking.

I think Ill still pick up those $33 12" dayton woofers to play with and if nothing else use them as boxed subs to go with my computer speakers.

[AJINFLA]

I WILL be buying four 6.5 poly's from them.

NPDang (DIYMA) will be posting Klippel data on those units in the near future.
He also has a version of the BG Neo3's for $25 ea. if you wanted to mimic the DDR design. The AA drivers may actually be a better fit for this type design that the Adire, which I wouldn't use that high up. You would have a very light weight speaker system, easy to move 4' out into the room when in use and back closer to the wall when not.

cheers,

AJ

[knifeinthesink]

What's Klippel data?

Ill look over the DDR more closely. It looks interesting.

Im pretty excited about trying these out. If the frequency response is anywhere near as smooth as the graph on the AA website these are going to be a treat to work with.

[ThomasW]

http://www.klippel.de/company.asp

[AJINFLA]

http://www.diymobileaudio.com/forum/showpost.php?p=44906&postcount=1

Greater sensitivity than I expected for a driver with 9mm xmax. Looks quite usable for this application.
If/when these build houses eventually develop (or "borrow") cone technologies similar to Infinity's CMMD (rigid cone with higher frequency breakup, lower xo cost, wider useable range) we will have some outstanding values in drivers.

cheers,

AJ

[knifeinthesink]

very usefull info.

Is the aproximate 5db frequency rise starting at about 600hz and peaking around 1800 hz significant? I would think it would require a notch filter if the driver is going to be crossed over around 2000hz.

The alternative to these would probably be the rs180 crossed 4th order at about 1500hz. Would the AA drivers require a less complicated crossover? My guess is that it wouldn't be much less trouble, and all Im getting is a couple mm extra excursion, with less detail then the dayton drivers.

Is my thinking on track here?

[knifeinthesink]

So...

I thought I'd give an update, since I went on a fun and suprising digression that still follows my original intention.

I happened to find a large number of those monsoon ribbon computer speakers at my local surplus shop. These are the larger wide range drivers, the planar 9s. I bought 8 for $7.50 a piece and duct taped 4 per side to some foam core and what do you know, they sound great. More then great infact. I have one cd of accapella renaissance music that I've owned for 16 years and I've never heard it like this before. Only hitch is thereis no bass below 100hz. None. Ill find some woofers to fill it out.

Anyway, fun experiment.

As for the original discussion, Ascendant is out. Too flaky!

I think its going to be RS180s, some 12" woofers, seas tdfc, and i think Ill nab one of those behringer digital xo things. If it doesn't sound as good as my surplus experiment, which would really suprise me, Ill build one of Jons projects with the rs180s and enjoy it.

[Dennis H]

Those Monsoons are great midrange drivers if you're doing a line array. Too bad they went out of business. Those are basically the same drivers Brian Cheney uses in his recent VMPS designs.

[knifeinthesink]

Had a look at the VMPS site. Intersting.

Apparently the place I got these from bought a couple of skids of monsoon products. Im planning to go back and get more so I can make a longer array later. Not much you can buy for $7.50 at any quality level. Once I get my mitts on a mic pre it will be interesting to see what the frequency response is like on these things.

[jdybnis]

There were a couple different driver models Monsoon made. The first series used in the MM-700/750/1000 speakers are the ones VMPS uses. These are the ones I recommend buying. The other models used in the Planar 7/9/14 speakers are of lower quality. Also in the later series the drivers are integrated into the base. They seem like they would be difficult to mount on a baffle.