First OB, help with ideas?

Viridian · « **on:** 17 Apr 2007, 10:08 pm »

Hi all, firstly I gotta say that this forum has been great. LOTS of good posts to read and learn from. Thanks.

I really want to build an OB set of speakers which will be a first for me and some folks have recommended that I start with a set of Hawthorne SI's. Well, I probably should have done that but I had already put in a bid on eBay for a pair of Coral 12" drivers before that advice. Well, as luck would have it I was the only bidder on those drivers and they are now on their way from the Great White North. They are woofers, not FR. Here are the specs that I found from someone online:

Coral 12L 25B:Paper cone 12" bass driver, about 94 dB sensitivity, lineair upto 3kHz, Re= 6.6 Ohm, Fs=44 Hz, Qms=11.8, Qes=0.62, Qts=0.6, Mms=40 g, Cms=0.33 mm/N, Vas=110 L, BxL= 10.8 N/A, L1k=2.6 mH, 60W, 8 Ohm, Japan.

My question is: do I cut my losses and sell them off and get a pair of SI's or do I scab something together which won't have the advantage of single point source, etc. but will hopefully still sound good?

Here are my hairbrained ideas:
1. Buy an active xover like the dbx that MJK did with his OB project and combine the Corals with this aurum cantus g2si
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=276-400
then bi amp(twin TA 10.1's) the set up in an OB.

2. Same as 1 but instead of the ribbon tweeter get a Fostex FE127E
http://www.madisound.com/cgi-bin/index.cgi?cart_id=3929217.1842&pid=323
and incorporate that into the OB with the corals.

Needless to say I will probably have to use some bass augmentation for either configuration.

So, what do you think? Sell the Corals or keep them and try to make them work with something or other?

What sort of size baffle do you think I would need to have to get the best LF from the Corals? I tend to think that the smallest I can get away with would be best, but i am still very fresh to all this.

When all is said and done I will probably have as much into a 2way setup like I have proposed as I would have spent on SI's to begin with. What would you guys do?

One more hairbrained idea: could I mount the baffles to the ceiling and take advantage of the ceiling to propagate the bass in an unobstructed way? Adjustments to placement would be virtually impossible but it would keep the drivers away from my 2yr old.(big advantage)

Thanks much, I look forward to hearing what you have to say.

Erik

gooberdude · « **Reply #1 on:** 17 Apr 2007, 10:24 pm »

Hey Erik,

My OB experience is so new I won't even try to wax poetic...but the SI's are a terrific deal and a simple way to go OB and not need addtl bass augmentation, unless you want it. they play so goddam low & hard yet sweet & silky its not even funny.

I am curious to see how others respond though.

matt

opnly bafld · « **Reply #2 on:** 17 Apr 2007, 10:51 pm »

Erik,
If you can pick up an active crossover cheap and don't mind biamping, I would suggest using a pair of full range speakers with the Corals so you can keep the x-o point at lower frequencies and out of the critical midrange. I would personally try this if I already had the drivers, but one person's learning experience is another person's waste of time and money (budgets being different and all).
Have fun and experiment.

Lin

Viridian · « **Reply #3 on:** 18 Apr 2007, 02:00 am »

Thanks Matt and Lin,

Lin, what xo freq would you recommend?

opnly bafld · « **Reply #4 on:** 18 Apr 2007, 03:49 am »

Quote from: Viridian on 18 Apr 2007, 02:00 am

Lin, what xo freq would you recommend?

It would depend on which full range drivers you use.
Some of the smaller ones need to be crossed over higher, @400hz, because they run into excursion problems and larger drivers with a higher qts and lower fs can be used down to @200hz.
If you have an SPL meter and a test disc you could determine where the full rangers fall off or if you have a crossover you can adjust the x-o freq. up and down to get a feel for how it is affecting the fr driver.
I would want the x-o as low as possible without leaving a whole or a drop in response between the 2 drivers and high enough with some drivers so that they don't blow up at moderate to loud volumes.

Ambiguously,
Lin

JLM · « **Reply #5 on:** 18 Apr 2007, 09:07 am »

Why not use a subwoofer plate amp that includes crossover? That would be in about your price range and allow you the freedom to select about any extended range mid/tweeter and matching amp size.

The SI is a remarkable product. Due the large difference in woofer/tweeter size, there is some beaming of upper midrange frequencies (around 2500 Hz), but the low bass output and efficiency are remarkable. A lack of detail retrival and the big (natural) OB soundstaging makes them easy to listen to. At this price range any compliants are pure quibbles. (No, I'm not ready to replace my speakers that are "cheap" at 10 times the price for SIs.) Hawthorne is working on a smaller version if you have a sub, and a couple of high end options.

JohninCR · « **Reply #6 on:** 19 Apr 2007, 01:01 am »

An FE127 needs a tweeter to fill in the top so it wouldn't be appropriate. That line of thinking does make sense in terms of flexibility and being able to cross lower, but you'd want something more extended and smoother at the top. A lot is going to depend on your listening habits, musical tastes, system plans, etc.

Viridian · « **Reply #7 on:** 19 Apr 2007, 03:12 am »

Quote from: JohninCR on 19 Apr 2007, 01:01 am

An FE127 needs a tweeter to fill in the top so it wouldn't be appropriate. That line of thinking does make sense in terms of flexibility and being able to cross lower, but you'd want something more extended and smoother at the top. A lot is going to depend on your listening habits, musical tastes, system plans, etc.

Really John? I would have thought that the FE127 rolled off high enough for that not to be much of an issue. Huh, I'll have to look at that again. Ok, how about the FE126? That has extension to 25kHz and is more efficient. As far as listening habits go, I listen to just about everything but rock, rap, metal.

Thanks,
Erik

opnly bafld · « **Reply #8 on:** 19 Apr 2007, 03:44 am »

Quote from: Viridian on 19 Apr 2007, 03:12 am

Quote from: JohninCR on 19 Apr 2007, 01:01 am
An FE127 needs a tweeter to fill in the top so it wouldn't be appropriate.

Really John? I would have thought that the FE127 rolled off high enough for that not to be much of an issue.

There are a number of speakers (commercial and DIY) that use only an FE127E.

Lin

gooberdude · « **Reply #9 on:** 19 Apr 2007, 04:18 am »

Lack of detail retrieval in the Si's? c'mon Gymane! the SI's are lightning fast. there's very little these guys lack & mine are hardly broken in. Detail retrieval is SOTA & they don't beam whatsoever...achieving this was a major goal in their design from what i've read.. the new Sterling model will be even better too.

If it weren't for the raging tight deep bass performance & gigantic stage presentation, you wouldn't know they was 15's.

To felt or not to felt, THAT is the question...

In this configuration @ about 2 weeks old they've completely disappeared. No sound comes from anywhere near the drivers, quite an unexpected ride with the SI's. Oh, and i'm limping along on my backup Muse 100 amp...its not known to throw images like this. I think i'm in for a hair raising experience when the Belles returns from NY.

You can't see it in the pics, but each driver has $10 worth of Ace Hardware adhesive felt attached to the bare metal of the speaker frames. 1 layer of felt on all the stamped metal surfaces made them 'disappear' bigtime.

The grounding wires took them a major leap forward as well. Its amazing how small the baffles need to be for these.
mine are way too big still...

proud papa matt

Viridian · « **Reply #10 on:** 19 Apr 2007, 12:27 pm »

Thanks JLM for the reply. I am pretty committed to the Tripath amps I have now. I see the sense in what you are saying for sure though. JKardell suggested trying to design out the xover instead of using electronics. IOW, in his setup he set the FR driver in the very edge of the baffle so that it would not overlap too much with the woofers he is using. KISS. I wonder how far I can take that idea with woofers that are flat almost to 3kHz? It seems that for this project anyhow that I will need a xover.

things are getting complicated. I have just magically acquired 4 18" high Qts Goldwood drivers, so I am not sure what to think of where I am at with the SI idea. I am fast fattening up with multiple speaker projects. As far as this one goes, I think that I will try to make my Coral woofers work with a Fostex 126E. The reason is, I don't want to invest in a set of good tweeters which I don't see being able to use for something else in future. Instead of creating a classic 2way I would like to make something that is a little more like an FR with bass augmentation.

Matt, thanks for the pics. The SI's, from peoples descriptions, must really sound amazing. I remain intrigued.

Erik

mcgsxr · « **Reply #11 on:** 19 Apr 2007, 12:45 pm »

Ah yes, the Goldwood 18's - I stared at those longingly around a year ago, thinking that they would be fun! I know the XMAX is low, but with 4 x 18, they don't have to move much, to move a ton of air. Have fun with those!

I would honestly consider the CSS FR125 on OB, with OB subs that you plan - but they are lower efficiency than would best leverage your tripath amp. I have no experience with the Fostex drivers, other than hearing a set of Omega Super 3's once, in my system. I prefer my b200 Visatons, but they are more $ than the Fostex you are considering.

Watch for used ones, I guess.

It sounds like you are interested in exploring some speaker building, and I think the ceiling mount would be an excellent idea - you get ceiling boundary gain similar to floor gain, but keep the little hands away from the drivers - my youngest daughter (both are under 3.5 years old) recently pushed in the dust cap of one of my Visatons. The perfect opportunity to install some phase plugs from Planet 10!

Bob in St. Louis · « **Reply #12 on:** 19 Apr 2007, 03:20 pm »

Quote from: Viridian on 19 Apr 2007, 12:27 pm

The SI's, from peoples descriptions, must really sound amazing.

Yes. Absolutely 100%. As I've said before, after purchasing a couple HawthorneAudio SI's, my search for drivers is over. I can't give a higher recommendation.

Bob

robert1325 · « **Reply #13 on:** 19 Apr 2007, 03:22 pm »

zapper7 · « **Reply #14 on:** 19 Apr 2007, 04:19 pm »

Hey Guys, on that ceiling mounting thing.

I have the room and ability to mount the SIs on the ceiling, where do I begin on the baffle required for a ceiling mount?

I think the idea of having the fronts and center ceiling mount would be great for my room, but need to know what the baffles should look like for that application.

I can't even imagine the 3 SIs ceiling mount along with my floor mounted IB subs, would be way cool, I think, right???

Bob in St. Louis · « **Reply #15 on:** 19 Apr 2007, 04:30 pm »

Hey Zap, As far as I know, everything would be the same regarding baffle size, shape, distance from seating, and construction of the baffle. Just mount it to the ceiling. The only thing I see as a PITA is adjusting tilt and toe would be more difficult.

Bob

mcgsxr · « **Reply #16 on:** 19 Apr 2007, 04:49 pm »

I am with Bob, design as though floor mounting, heck even test them there, and then install upside down on the ceiling.

Absolutely zero WAF I should think...

zapper7 · « **Reply #17 on:** 19 Apr 2007, 08:22 pm »

MY room in the house

, she doesn't care.

I will give it some thought and see what happens.

Bob in St. Louis · « **Reply #18 on:** 19 Apr 2007, 08:33 pm »

Ceiling height??

zapper7 · « **Reply #19 on:** 19 Apr 2007, 09:08 pm »

8', so not too much angling of the baffle.
When are the Sterlings coming out anyway, that would be the ticket. 3 of those and off I go