approaching a 3 way

[mrkramer]

Howdy all,

I'm listening to my TB bamboo BIBS right now. I really like them. Like any new addict however I cant help think they could be better. Ive got some time and Ply. Figure Ill make something different. Something with a little more hit on the bottom end and a little less laser beam on the top. Id really like to maintain that sense of the speakers disappearing but Id like to broadened the soundstage. I also need to make sure it is easy to listen to. For some reason I get a headache quickly listening to some speakers.

Whether its a wise choice or not, I want to try a 3 way system. I also want them to be wide baffled because I'm tired of skinny, and I'm thinking sealed. I somehow imagine half of you thinking "Noob" and the other half just clicking to another thread. I hope not!

I read up everything I could find, and picking crossovers and driver sizes to match dispersion seems to make sense to me. Making the baffle slant back a bit to match acoustic centers sounds appropriate. I have another pair of 4" TB's I could use as mids. They have a pretty wide BW so crossing them over on both sides 1st order sounds somehow correct. Am I barking up the wrong tree here?

I know there are lots of books and articles out there on 3 ways and Ill read any of them that are recommended. Im more interested however in personal thoughts and experiences of the people here. What approach do you take? What worked out well and what wasn't what you hoped for?

Not looking to make the penultimate anything. Don't want to make a kit or a "proven design". Just want to learn, have fun and hopefully make something I like.

Any thoughts?

MrKramer

[Undefinition]

I built a 3-way for my first "original" design. It probably wouldn't have worked, however, unless Andy G was nice enough to guide me along. Mine happened to be a dipole mid project, but that doesn't mean you have to do that. You can do just a standard, monopole 3-way.

Anyway, the advice he gave me would still be the same advice I'd give to you:
+Choose a mid driver with the flattest response possible. This will allow you to use a 1st order electrical on it, which will make EVERYTHING about the project about 10,000 times easier.
+Choose a tweeter that is easy to work with. To my knowledge, the Seas 27TDFC is about as "cooperative" as they get, but there are plenty of others. Try to find something with a nice low Fs and a smooth overall frequency response.
+The bass driver, you can get a bit more experimental, but you're still best off searching for something that is relatively flat, so that the LP filter can remain simple.
+Crossover points at about 250 and 2500 Hz are a very good place to start, as it keeps the midrange IN the mid driver, if that makes sense. You can go up or down on the crossover frequencies from there, but listen to it there first... it's a good "happy zone" for most tweeters, mids, and woofers.

If your drivers are fairly reliable (eg: "flat"), you can actually start out with "textbook" filter values and it will sound pretty good from the get-go. From there, you can continue to tweak (you may also want to start simulating the design in some sort of speaker design software) with crossover values and adjusting padding resistors until the speakers really start sounding the way YOU want them to.

THe only difference between my advice here and what someone as brilliant as Andy would tell you is that Andy would also suggest a series crossover. And if your drivers all do have pretty flat responses, you CAN do a series XO and it's actually pretty easy. He has a spreadsheet where you can get some starter values for components. You hook it up, and continue to tweak by ear. If you choose drivers that have breakup modes, you'll probably want to do a parallel XO.

So there's some stuff to get you started. Hope it helped.

-Paul

[Alex from Oz]

Originally posted by mrkramer

I'm listening to my TB bamboo BIBS right now. I really like them. Like any new addict however I cant help think they could be better. Ive got some time and Ply. Figure Ill make something different. Something with a little more hit on the bottom end and a little less laser beam on the top. Id really like to maintain that sense of the speakers disappearing but Id like to broadened the soundstage. I also need to make sure it is easy to listen to. For some reason I get a headache quickly listening to some speakers.


Any thoughts?

The first thing to consider is why you like the TB BIBs.

A larger FR driver with phase plug would give you the same magic that you have now
PLUS "a little more hit on the bottom end and a little less laser beam on the top."

Cheers,

Alex

[Moondog55]

Hi mrkramer, I must admit a liking for 3ways myself, and to stuffing up a few as well.
Pauls advice is good, just remember to avoid thing like using a 3inch mid with an 18inch woofer and have a go.
Some general advice on little things I've picked up, big woofers make better bass, midranges sound better when used with as wide a range as possible and sometimes if you draw up plans and it doesn't look right, that may be telling you it won't sound right either ( but not always ) A good way to start may be with 10 inch woofers 4 inch midranges and a tweeter, if using MTM the make the mids no bigger than 51/2 inches and keep the distance between the mid andd the tweeter as small as possible Neo tweeters may be of benefit in this situation.
Best wishes
Ted

[Andy G]

All the advice above is logical stuff.

My basic logic for a 3way is....
if its a WMT then the M should be about half the W diameter.
If the mid ends up having to be a 6", then you have to use a 1" tweet with a lowish Fs. A 4" or 5' mid, you can cross a bit higher and maybe use a less robust tweeter, maybe even a 3/4"

So.. 12"+ 6"+ low FS 1" tweeter
or 10" + 5" + normal 1" tweet
or 8" + 4" + maybe a 3/4" tweet

For a W+ MTM design the mid can be a bit smaller so long as you can easily (without forcing EQ) take it down to meet your woofer. This allows for a smaller mid and hence getting the mids closer together, particularly if you can find a smaller faceplate tweeter

this is guideline stuff only, and if you know what you are doing, guidelines can always be bent !!!

For me smooth roll-offs are a must for easy nice sounding x-o filters. IMO the less x-o components you can use the better.. (every component subtracts something, and you cannot always absolutely control what is subtracted..... there is no such thing as a passive component 'adding' something to the sound.)

Generally, avoid choosing drivers that force you to cross between say 300 and 2500 unless you want to play hard-ball with the cross-over.

being able to use a series x-o is, of course, a plus, but does require careful driver choice. If you need to batter your drivers into submission, use a parallel x-o

[PeteMcK]

Re: 'I get a headache quickly listening to some speakers' - as well as a mid with flat response, also check out distortion characteristics, go for the best you can afford. Cheaper drivers may sound OK at low levels, but when you push them...aargh!!!
Manufacturers don't publish distortion figures, that's why tests by guys like Zaph are so valuable to the DIY community.

[mrkramer]

Thankyou all for the responses. Very helpful.

PeteMcK - "Cheaper drivers may sound OK at low levels, but when you push them...aargh!!!"

-Thats it exactly. I end up listening to really low levels.

Andy G - "if its a WMT then the M should be about half the W diameter."
"For a W+ MTM design the mid can be a bit smaller so long as you can easily (without forcing EQ) take it down to meet your woofer."
"this is guideline stuff only, and if you know what you are doing, guidelines can always be bent !!!"

-I read that last line and actually laughed out loud! I'm afraid I know just enough to really screw everything up!

Alex from Oz - "The first thing to consider is why you like the TB BIBs."

-I really love the, well, for lack of a better word "coherent" sound. I really considered a larger fullranger. I have actually made 2 sets of full range speakers. The BiBs being the latest and greatest so far. (ha- best out of 2!) I just really want to try my hand at something different. BTW - Love NSW! Lived in Sydney for a year.

Moondog55 - "A good way to start may be with 10 inch woofers 4 inch midranges and a tweeter"

Undefinition - "Choose a mid driver with the flattest response possible. This will allow you to use a 1st order electrical on it, which will make EVERYTHING about the project about 10,000 times easier."

-I like the sound of "10,000 times easier."!

"Crossover points at about 250 and 2500 Hz are a very good place to start, as it keeps the midrange IN the mid driver, if that makes sense."
"....Andy would also suggest a series crossover"
-----
So.
Ive decided that a WMT configuration is the way I'll go. I read up a bit on the series 1st order crossovers and they are intriguing. I'm not sure how I would calculate them though. Is there any simple software out there someone can recommend? I will use my extra pair of 4"TBs as mids. They seem like a good candidate due to wide/flat BW and as a bonus I already own them! As for the woofer, I had looked at using one of the Dayton RS series, RS180/225/270. After reading your posts however I really started to look at thier graphs and they all get spastic as they hit a certain freq. Ive heard it called "cone breakup" I think. Oh well, they looked nice! How about using this Peerless SLS 10" ?
http://www.madisound.com/catalog/pro...oducts_id=1705
Would this be a good choice? I want an all sealed system and it seems appropriate for that. Will it match well with the TB? Say crossed at somewhere around 250-300?
I havent really looked at tweeters yet. Guess Ill check out the Seas 27TDFC. Any other suggestions? I saw the suggestion to go quite small like a 3/4. I was worried about using that with a 1st order cross.
As far as where to cross them. I can hear my TBs start to get beamy around 4-4500 or so. Im not sure where this acuratly starts but thats roughly where I hear it. It makes sense to me to cross it in that range. Any issues with this? I know most seem to cross it way lower.

Thanks again
MrKramer

[Andy G]

Originally posted by mrkramer


I saw the suggestion to go quite small like a 3/4. I was worried about using that with a 1st order cross.

You are getting wise, young padwan. If you are using a low order cross-over you must use a beefy tweeter, which generally means that you will have a 4" faceplate, which means you need to look at crossing around 2500 or below. Only use a 3/4" if you can do steeper slopes in the x-o


Its difficult for us to suggest drivers available over there. Maybe the new SB Acoustics tweeter? And the SB 10" bass, while quite expensive would surely kick big time, and might be quite usable.. (Why don't they do an 8" I wonder ??) just suggestions to look at.

That Peerless SLS would probably fit the bill quite well, too.

[Moondog55]

That Peerless looks OK, but I would use 2 of them ( I like big bass) but I'd be using the second rolled off first order with a really big inductor no matter what X-O you use higher up, really a 3.5 way.
Andys advice is good so using that 10 inch woofer you could use a 5 inch mid ( I'd say use a Vifa P-13 but sadly no longer available ) plenty of smooth mids around though and using a robust tweeter with a low XO point is always good advice even if crossed over high.

View all the other threads on building 3-ways before starting, stand on someones shoulders to get a head start.
regards Ted

[Alex from Oz]

Originally posted by mrkramer

-I really love the, well, for lack of a better word "coherent" sound...

You will find it very difficult to build a three way with the same
coherent sound that you enjoy in the BIB's.
Another possibility to consider is FR with helper bass woofer.

Cheers,

Alex