Idea for tall slim B3s design- MMTMM

[joe carrow]

Hi all,

I noticed that on Zaphaudio.com, Zaph's poll suggested that a tall slim floorstanding unit with an optional side-firing sub was something in great demand. A little thought about my living situation (apartment complex, not much space) made me realize that this might be best for me as well. Rather than wait for a design, I thought I'd get the ball rolling.

First, I suggest using the Hi Vi B3s driver as an extended mid running from 200-300hz up to the tweeter crossover. http://www.partsexpress.com/pe/showd...number=297-427

Next, the Dayton ND20TA tweeter running as high in frequency as possible. This tweeter is selected to minimize center to center spacing for the high crossover. http://www.partsexpress.com/pe/showd...number=275-030

Finally, for the bass I propose the RS180S, chosen for its size and versatility.http://www.partsexpress.com/pe/showd...number=295-364

The main problem with this driver (so i hear) is the high frequency breakup. Because I propose to use this driver in a side-firing application from 30-40hz up to 200-300hz, it should be passable with a second order crossover. Any breakup modes will be at a higher frequency(more directional) and 90 degrees off axis to the listener. I took inspiration for this from the Linkwitz Pluto (linkwitzlab.com), where he uses a 5" driver at 90 degreees off axis all the way up to 1khz. I think that the RS180 will be reasonably omnidirectional and able to be placed within 1/8 wavelength at 250ish hz.

Some things to note about this project: The entire package will be 5-6 inches wide in MMTMM arrangement. Max SPL should be safely over 100 db at 1 meter, maybe 105 db optimistically. Crossovers can be 2nd order; this is definitely a three-way design. Depending on how I align the RS180, I think this can be made to function from below 40hz up to 25k.

Total cost of drivers is around $160 per pair. Second order crossovers should keep parts count low, and reduce crossover cost. Obviously, the low crossover could be improved if it is active.

I will be looking at the possibility of loading the mids into a tapered terminated tube, and having a transmission line for the RS180. I might be able to cram all of this in a 5" by 11" by 32" package.

So, what do you think?

Joe

[Zaph]

Hi Joe,

Thanks for reading my poll and the interest in a project like that.

I've been a little busy on business lately, but that hasn't stopped me from at least thinking about what I wanted in an MTM. I may just post another poll to see what you guys think. Mainly, I wanted to find the right balance of cheap, slim, good looks and good sound. (not neccessarily in that order)

Within and hour or so, I should have another poll up. Of course, the B3S is a nice super-slim option which would be pretty cheap for all the drivers required. For the side firing sub however, I wanted a plate amp powered option, probably of 12 or 10", 8" at the minimum.

John

[Ap]

Joe - sounds like a great idea/design.
I had been thinking about something similar.
I feel you could increase height to 40", possibly reduce depth a little & still keep it domestically acceptable.
Going for a TL on the bass might be overdoing it.

[jdybnis]

Zaph, the M4N could be good for a slim MTM. I plan on getting a pair of these to play with. They are cheap but they look very nice from their specs. From their impedance and frequency plots the first breakup looks to be at 6k.

The B4N might be good too if you cross over steep and low. It's first breakup is at 3k.

[jdybnis]

Looking at the CLIO measurements on parts express the B4N might be good until 5k. Major inconsistency with the manufacturer spec.

[joe carrow]

Good morning, all.

Originally posted by Zaph
... Mainly, I wanted to find the right balance of cheap, slim, good looks and good sound. (not neccessarily in that order)

I think I'll steal that as a motto for the project

Originally posted by Zaph
Within and hour or so, I should have another poll up. Of course, the B3S is a nice super-slim option which would be pretty cheap for all the drivers required. For the side firing sub however, I wanted a plate amp powered option, probably of 12 or 10", 8" at the minimum.

John [/B]

I agree with you on the woofer size, if you're in a "normal" house. The plate amp is a great idea, though- I hadn't thought of that. If I see one that plays well to over 1khz, it would help a lot.

Originally posted by Ap
Joe - sounds like a great idea/design.
I had been thinking about something similar.
I feel you could increase height to 40", possibly reduce depth a little & still keep it domestically acceptable.
Going for a TL on the bass might be overdoing it.

Thanks Ap- I agree that it could be taller and acceptable... but the TL might be necessary for this design to work to its potential. The reason why hinges on the B3s midrange. If I can push these much below 200 hz, then there are more options. The problem is that for a midbass running up to 300 hz in a cabinet less than 5 inches across internally, the depth and height start adding up to a good portion of a wavelength inside the passband for a box with any sort of volume.

[joe carrow]

jdybnis- I think you're on the right track with a driver larger than the B3s. Going MTM with 5" drivers could probably get enough midbass to cross to a 10" side-firing woofer without problems in directivity. Furthermore, a 10" could have enough displacement to withstand a linkwitz transform, and the whole cabinet could be smaller for it.

The main problem that remains is cost. I have a very limited budget and already own a nice 250 watt amp. Low-order high-frequency crossovers are a big win on cost, so that's why I want to do it like that. If I can find a 5" midbass that does 100hz-3ish khz, and crosses easily to a cheap tweeter... then I'm happy.

[jdybnis]

I'd wouldn't discount the 4" midbass. It seems that there are more cheap tweeters that sound good above 3k than below. And going from the m4n to the m5n the price goes up 50%. Also the higher crossover means the crossover parts are cheaper.

With the right ported/TL alignment you could probably get strong performance with a 4" down to about 150Hz. I'm not really knowledgeable enough to really figure that out off the top of my head. I'm guesstimating here based on comparing the Vd with a ported 8" two-way that's flat down to 40Hz. Add in a $50 sub driver and I think your good down to the 20's in a small room. Maybe the 8" quatro or one of the TB subs like the one onsale today at PE.

[Pallas]

This project sounds interesting, if not necessarily for hard-core audiophiles at least to build as presents. I'd consider building a pair to replace the crap speakers in my sister's HTIB. (It's Koss thingy from Best Buy, and the electronics box with its TI PurePath amps is surprisingly good but the speakers unsurprisingly suck rocks through straws.)

I like the Aura NS3 for the midrange, for a variety of reasons that have been well-discussed. (To summarize, cheap, underhung low-distortion motor, massive excursion for a 3" driver, smooth FR.) For the tweeter, does anyone know if there's a US supplier for the ATD spiral planars? E-Speakers.com used to carry them, but they don't list ATD any more. That's a really, really sweet tweeter that basically nobody has used because it requires a three-way design. (Genesis used it commercially.) Then again, a German planar/ribbon vendor Expolinear (who generally do a good job of editing their collection, and as BerlinerInnen are ipso facto cool) lists a HiVi model as their replacement for the ATD spiral. It appears to be available in the USA, too. Even if it's more expensive than the alternatives, its resistive impedance should allow fewer crossover parts.

For an optional sidefiring woofer, given the emphasis on a slim baffle John Janowitz's new 10" sub seems to recommend itself. It is a bit pricey, though a "slimline NHT 3.3" (i.e. speaker designed to be against the wall, creating its own virtual room corner for the woofer while sticking the mid and tweet out far enough into the room to sound good) is a very cool idea.

[Ap]

For design inspiration I quite like the Bosendorfer loudspeakers (yes the piano makers).
From memeory the B3n tested/reviewed really well even compared to the larger M4n.
http://forum.ecoustics.com/bbs/messa...81/134286.html