Narrow OB advice, please!

jetpack · « **on:** 28 Mar 2016, 07:10 am »

Hi all.

I’m looking for open-baffle suggestions. I’ve read many threads on the benefits and drawbacks of OB and I am ready to try something serious. (Actually, these will be for a friend, but to keep things simple, I’ll refer to him as “I” in the first person, from here on out!).

I’m taken with the look of BD’s Quasars (dual 15” and an 8-inch fullrange per narrow, tall, and deep (approximating a U) baffle. I realise that tall and skinny isn’t ideal for performance, but it is an aesthetic compromise. Room size is big enough and there is plenty of space to be had behind the speakers. Amps can be anything from a few SET watts, to 30+ watts of push pull pentode, or solid state bi-amping if necessary. I understand the dual woofers will increase the efficiency by a few dB/W/m but will not lower the low-frequency corner. I’m not apposed to using a miniDSP and EQing things flat. I’m hoping to get down to ~30 or 35Hz in-room with no sub. Is this dreaming? Regardless, a full soundstage with plenty of imaging and a bit of mid-bass punch are necessary.

I already have some Fostex 206en drivers that can be donated, or some Alpair 10.3. I have some compression drivers in diy OSWG that might be fun to duplicate for a future upgrade as well.

I’ve searched online a lot, but haven’t found any proven plans for this sort of speaker, other than the bd-design’s one and MJK’s (double H-frame) with AE. Those woofers are out of my budget. I’ve also read MJK’s single 15” white paper and tons about the Manzanita.

Eminence Alpha or Beta would suit the pocketbook, which would also probably stretch to cover the pureaudioproject’s OB-A15se or neodymium OB-A15new if there were a seriously compelling reason to do so. Hawthorne Augies would really be pushing it — and I’m not certain they are financially viable, but maybe. Same for the AE. Perhaps there are some budget JBL that might work…

So, at this point, would anyone please care to offer advice on bass drivers and crossover topology as a starting point?

Many thanks in advance! If there is interest, we’d be happy to post a build-thread.

sonicxtc · « **Reply #1 on:** 28 Mar 2016, 01:11 pm »

I don't have much time, right now, so I'll be brief.
Hawthorne's SSI are excellent drivers and the Augies are a great choice, too for bass. I own
the Hawthorne Trios, so I speak from experience. I recently made a system change and the Hawthorne's readily demonstrated the change in all regards including increased detail, extended HF without harshness and better soundstage. Critically, Darrel is one heck of a guy who is always helpful, straightforward and no BS. I'd suggest you contact him directly for input. Just my 3 cents.

FWIW, maybe you should state your budget range.

Good luck.

jetpack · « **Reply #2 on:** 28 Mar 2016, 04:47 pm »

Thanks for the input sonicxtc.

Regarding budget, I'm hoping that the knowledge of the forum can help me figure out what the appropriate 'sweet spot' might be to get the best bang for buck. The budget definitely won't cover a quad of AE drivers at $1440. The budget will cover a quad of Eminence Alpha 15a at $240.

Other parts of the build (driver for the highs, wood, x-over, etc.) don't need to be factored into the price just yet.

How much power would a pair of Augies per side want? How much EQ would it take to get 35Hz out of them?

Other drivers? I'd still love to hear more thoughts!

mlundy57 · « **Reply #3 on:** 29 Mar 2016, 03:28 am »

I've used both the 8" and 12" GR-Research OB drivers along with the corresponding Rythmik amps (HX300 with 8" and A370PEQ with 12") in different OB builds. These driver/amp combos can play from 20Hz to 300Hz.

The quality of the bass from either combo, while not identical, is exceptional. You can find a lot of info on these OB subs, including different builds people have done in the GR-Research circle.

Four of the 8" drivers and two HX300 amps would run a little over $1,100 while four 12" drivers and two A370PEQ amps would run a little over $1,500.

8" drivers http://gr-research.com/sw-12-08-1.aspx

12" drivers http://gr-research.com/sw-12-08fr.aspx

Mike

jetpack · « **Reply #4 on:** 29 Mar 2016, 04:49 am »

Thanks mlundy57. I wasn't aware of GR-Research, but I've had a look into them now.

I'm wondering if I've actually asked exactly the wrong question. Perhaps I should choose the xover point and let the required woofer response drive my search.

So, are there any strong opinions about the best crossover point for a 2 X 15 + widerange/fullrange? I understand that the higher the large drivers go, the more they beam. Surely someone has worked out the best way to keep the dispersion pattern good and the sweetspot wide while maximising the potential of both woofer and fullrange. I don't need high levels; this is just for a living room.

Thanks again for the suggestions so far and for any further advice!

JohnR · « **Reply #5 on:** 29 Mar 2016, 05:27 am »

You asked for a proven plan, did you see the MJK one here: http://www.quarter-wave.com/Project08/Project08.html

jetpack · « **Reply #6 on:** 29 Mar 2016, 05:58 am »

Thank you JohnR. Yes, I'd seen that. I'm not keen on the aesthetics of H-frame woofers.

I was originally hoping for an easy (lazy!) well documented, cheaper version of the D.B. Quasar. Maybe there isn't such a thing and I have to try and start oiling the brain. I have a calibrated mic and miniDSP. If I thought there was a good chance at success, I could piece together something around separates. Ground rules at this point are skinny and tall with a couple of 15s per side. I was hoping for an upgrade path on the mids and highs, starting with some fullrange I already have and leaving it open for others later on.

The problem is, it is a lot of money to invest if I'm not confident in the final outcome. I rate my knowledge level on a good day midway between useless and competent. My woodworking skills are slightly better.

JohnR · « **Reply #7 on:** 29 Mar 2016, 07:19 am »

It sounds to me like you should just buy a quad of 15" woofers (e.g. Alpha 15), cut a baffle for them and the FR you already have, and start measuring and experimenting. You can mimic the layout of either the quasar or the pureaudioproject speakers. It won't be perfect but you will learn a lot without spending too much and then be in a position to figure out where to take it from there. I'd let go of the 35 Hz goal with that type of woofer and just focus on getting something that works.

jetpack · « **Reply #8 on:** 29 Mar 2016, 08:26 am »

Yes, you are probably right w.r.t. just jumping in with 4 X 15a.

However, I'm suffering from a little scope creep. For example, my mental process tonight has compared the price of the quad of 15a's (~$300) with the price of a pair of Hawthorne Augies ($460) and a pair of their 15" mid woofers ($370). The $300 for the budget Eminence would go a long way toward the price of the Hawthornes. If I just upgrade in a few months, the price of the 15as would seem like money wasted.

How hard is it to get the sound coherent from something like this? Will a DSP magically be able to mate this sort of combination into the bass/mid portion of a 3-way? The room is pretty long, so I'm hoping that will help. I just don't have any experience with OB so I'm still a bit hesitant to jump in with both feet. I've tried to combine random mid and high-frequency horns into a 3-way and it was almost a complete disaster.

In over my head but thanks for the help!

JohnR · « **Reply #9 on:** 29 Mar 2016, 08:38 am »

I think you need to decide whether you want to get it right first time, or whether you are willing to experient/go out on a limb. The latter means that you WILL make mistakes. That's why not spending too much is a good idea.

You are right in that $X spent on a sub-optimal solution is $x that could be used towards the optimal solution. However, you seem to have no idea what the latter is (no offence). Nor do you really have the budget for a really good solution anyway (per your posts so far).

jetpack · « **Reply #10 on:** 29 Mar 2016, 08:52 am »

Ouch. Thanks for the candor.

JohnR · « **Reply #11 on:** 29 Mar 2016, 09:14 am »

Sorry, I wasn't trying to put you off your project. Just trying to help you make progress - by limiting the scope?

FWIW, my first OB was a RadioShack driver in a piece of plywood, as recommended on some other forum. It was absolutely awful. When I saw awful, I don't mean OK within its limitations, I mean awful. All I can say about that is don't believe anything you read on the Internet

There have been some great recommendations in this thread but OB is just not as simple as boxes.

Poultrygeist · « **Reply #12 on:** 29 Mar 2016, 10:49 am »

I've enjoyed my two Alpha's per side on flat baffles for several years now. Wired parallel, a single 100 watt plate amp is a gracious plenty.

MDF is cheap so you can try any number of wide band drivers on top.

I use my wide banders ( DX3 ) as wide banders with nothing in the signal path and just bring in the woofers to fill in what the wide banders can't do.

I've tried several electronic crossovers but found they took away some of that SET/Lowther magic.

Guy 13 · « **Reply #13 on:** 29 Mar 2016, 11:01 am »

Hi Jetpack,
I did many experimentation with H frame and flat baffles
and all of them gave good results.
Flat baffles is inexpensive and give you a good idea of
how open baffle dipole sounds.
I have two 12'' on each side of the Eminence Acoustinator (Now discountinued)
driven by one on each side GR Research (Now discountinued)
250 watts each plate amplifiers.
Cost less than 600 USD plus some MDF...
For the mids - highs I have an Omega 7F (Or use yor own FR driver)
driven directly with a Decware SE84C+ (2 WPC).
The best system I ever had in my whole life.
Guy 13
Have a look in my photo gallery.

mcgsxr · « **Reply #14 on:** 29 Mar 2016, 02:50 pm »

Unless you are building up a kit that someone else experimented with, or spend a LOT of time researching I am doubtful that the first build will be the last.

I absolutely recommend building mules (ugly but effective) to see what you can live with, and what that delivers.

Lots of folks happy with Alpha's, I doubt you would be unhappy with a quad of those properly Xover'd and on the right size baffle.

When you say narrow - what do you mean?

I assume you mean that you are not interested in something like the 3x4 foot baffles I ran for 10 years. I first built them flat, but later installed piano hinge to allow folding of the wings. It was a great experiment. I was very happy with the resultant sound after about 12 months of playing with it, and left it as is for 9 more years.

A more motivated person might have rebuilt the mules into something more attractive, but the sound was very very good.

I used a Visaton b200 full ranger, and a set of Rockford Fosgate 12 inch car subs (!). I biamped them to great success. A 300w plate amp for the subs, and a 5wpc Magnavox console amp for the full rangers.

JCS · « **Reply #15 on:** 29 Mar 2016, 04:45 pm »

It's not clear to me exactly what you want. That said, if you want something modest in size which would sound pretty good at modest SPLs (I can't stand having peak SPL exceed 85 dB myself), then you might consider a variant of MJK's small passive OB. I built one with a bit more bracing (need to get a proper grip on the Alpha 15a when it kicks!) and tending to a U-baffle. Using no longer available Fostex FF85k and the Eminence Alpha 15a, along w/ Martin's passive XO design with the woofer's XO dropped to 160 Hz instead of the original 200 Hz.

If I did it again, I might look at the new (and only available for a short time) FE108-SOL ($153 each) or good old FX120 ($144); both are close enough in sensitivity to work, and either will have a bit more capability for SPL on complex orchestral music.

Cheers, Jim

flavo · « **Reply #16 on:** 29 Mar 2016, 11:30 pm »

Here's another example of one that's done for you.

http://www.fastlaneaudio.com/yields.html

I have 4 alphas (along with a HA PSI) and see no need to upgrade personally. But I will at some point because you never know. I'm thinking of getting the upper end PAP 15's

I also 2nd picking up some alphas and see where you go from there in terms of FR. I liked the "betsy" enough for what it cost. But I couldnt get it to play loud enough for my tastes.
Poultry has hooked up all kinds of full rangers to those alphas and could probably give you an ear full. But I think only your ear can tell you what you like.

jetpack · « **Reply #17 on:** 30 Mar 2016, 05:18 am »

Thanks to every one that has replied. There is a lot of good information. At the end of the day, the underlying theme seems to be a good one: jump in and see what happens. There are enough success stories out there that I'm convinced it is possible to build something that won't make one's ears bleed. I have perseverance in spades. I'll let you know what I come up with when I come up with it -- ear bleeding or not.

JohnH12 · « **Reply #18 on:** 31 Mar 2016, 03:44 am »

Here's a narrow OB a friend of mine did. I'll hear them this weekend.

http://projectgallery.parts-express.com/uncategorized/the-hurricanes/

Stal · « **Reply #19 on:** 31 Mar 2016, 11:32 am »

http://gainphile.blogspot.co.uk/
This guy seems to have quite a few narrow OB designs.