One woofer or two?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Member
Joined 2002
Paid Member
I have a basic design question I'd like some input on. I'm designing a two-way speaker and I'm at a fork in the road. Do I go dual 6.5" bass/mids or a single 8" or 10" woofer? What are the pros and cons of each approach? The tweeter I'm using will 'theoretically' blend well with either approach so I'm puzzled why some designers go one way and some the other.

Dan :)
 
Using dual drivers can increase the overall sensitivity of the speakers, thereby making them easier to drive. Also, distortion is kept minimal, since each driver only has to do half the work to achieve the same output levels.

It should be noted that a number of 8 and 10 inch drivers won't blend properly with most tweeters. Although their specs may extend high enough, the distortion is very high, and they tend to generally have poor midrange sound characteristics. The general exceptions to this would be the use of PA drivers.
 
Woofer

There are more ways than one to skin a cat but most "woofers" larger than 61/2" are not going to mix well with a tweeter and leave you short in the important 600-6000hz frequencies. Take a look at northcreek, madisound and some places like that and look at their design tendencies with 2 way or 21/2 way mtm designs. If you are just starting out (which it sounds like) don't try to design something new. Buy Vance Dickason's Book, The Loudspeaker Design Cookbook. Best $40 you can spend on speakers. Available at www.audioxpress.com. Consider a kit or backdesign/clone a proven winner. All sorts of sites on cloning good designs. Try www.klone-audio.com for one.

Every path in this hobby is a compromise.

Lots a Luck!!!
 
in general, using an 8" driver allows a lower fs. but, as super noted, using two drivers gives greater efficiency, and maybe higher spl, but this depends on the xmax of the drivers. also, the vertical polar response will be different.

the trick is that 8" drivers have a horizontal dispersion pattern quite a bit more narrow than 6.5 and smaller midbass units. this, plus their lower top end means that you really have to try to cross an 8 over between 1-2k. that's a tall order for most tweeters, though it can be done.

there's a view out there that only 5-6" or so drivers can adequately to justice to the midrange, but that's a subjective call. there are good and bad examples of both. i would say it's tougher to design a good 8" 2-way, though.

a 10" 2 way is definitely an advanced project.


if you want a good idea of the difficulty in designing a high quality 8" 2 way, check out Joh Marsh's project in the diy section of HTguide. it's the basis for an upcoming audioxpress article.
 
Member
Joined 2002
Paid Member
Perhaps I should add some more details here to clarify things. The 'tweeter' I'm using is very similar the Bohlender & Graebeners Planar magnetic RD50 which has a manufacturer stated range of 150Hz-18.5KHz. This makes it the exception to most rules because of it's extremely wide bandwith. This makes crossing over at 1500Hz 'easy' on the ribbon and 'easy' on the 8" woofer I'm thinking of. Hence, this woofer is not being asked to go into the 3-4k range of most two-ways.

Does this new information peak anyone's interest?

Dan :)
 
you have a plan

Before I fold my hand I will ask if you have heard it at the specific frequencies w/ the woofer/enclosure you want to use. I have had some unfortunate experiences relying on manuf. specs. It's a lot more work/tweaking to get a decent speaker from scratch by specs and cad, but maybe that's the fun, eh? Sounds like you have a plan.


Good luck
 
Member
Joined 2002
Paid Member
Although it's a first-time project I do have a specific plan. I readily accept the risks and hopefully the rewards of being a DIY'er. I'm reading books, websites, and asking questions of anyone that'll answer. I expect a few bumps in the road but that's all part of the fun!

Dan :)
 
nice ribbons, but tough project.

if i were designing a ribbon, i'd pick as low an xover as i could get away with. you'd just have to test the ribbon and see how low it can go.

here's the rub. a 45" ribbon is fairly tall, and at distances close to the ribbon, acts as a line source (more or less). your LF driver will end up acting like a point source (let's just ignore baffle step effects for now). so, at least for points close to the speaker, if you design for an optimum position, say 3 feet, what happens when you're 6 feet? uh, oh, if you're xover is at 2k, then the LF driver is down an extra 3db compared with the line source--male voices fading... etc. this may or may not be a problem depending on your listening position.

if you can get away with crossing over at say 150 hz or less, then you can bury this in the room gain, or at least get it out of the midrange.

i believe there was an SB review of the newforms a couple years back. i'll try to dig though my pile and see if i can find it.

mark
 
What is your cabinet design?

I would suggest you diverge as far as possible from the Newforms designs, while they are good quality ribbons their finished speakers have met alot of critisism, then again I've never heard the NF's so probably shouldnt spout heresay.

I own a pair of apogee Centaurus and think their design is very clever. From what I figure directly coupling the ribbons to the woofer, and sharing a wide soild baffle, really helps them blend together. Where as Newform tries to shed the cabinet Apogee wasnt afriad to use it to give the ribbon and woofer alot of shared flesh.
 
Account Disabled
Joined 2002
I'll second what Mark said- cross over as low as possible. If you can cross over at 150-250Hz, I would go with 2- 8" or 10" to deliver the bass. Are you going to be biamping or using a passive crossover? It would be a sweet project to biamp, it sounds like. I would like to do something similar in the (hopefully) near future. Also, considering the line/point source and the increased falloff of a point source compared to a line, you may want to consider what your listening distance is going to be and design the system around that.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.