DIY active monitors: Deep bass from small speakers?

[Joe Bee]

Another thread that does not really fit the board, but I'd hate to go where the audio-phools hang out and much rather stick with the musicians here!

The deal is this: I am looking for a bunch of small general purpose speakers to stick into my iMac for light home recording and keyboard monitoring duty, but mainly for listening to music.

I have looked at the likes of Yamaha HS50 and Genelec 8020, but they are
1) Not satisfying for a DIYer like me
2) Need a subwoofer to produce some decent bass

Now I have made some good experience with the Linkwitz transform circuit for getting deeper bass from a subwoofer, and I was wondering whether the same principle could be applied to get more bass from small (say 4") woofers. I see a few problems with this:

• There simply are no drivers out there with sufficient x_max (i.e inches rather than mm's) to move enough air with a small driver
• Having audible frequencies ride on top of the LF waveforms makes distortion really unacceptable
• There are some theories that say, regardless of driver excursion a small speaker can only go so low

these may well be the reasons why no commercial product like this exists, together with the fact that mating a pair of 100W+ amplifiers to a small table-top speaker seems a bit unconventional.

Anyway I'd like to throw this idea out there and hear what you guys think about it.

[Don Moose]

The Klipsch ProMedia 2.1 setup sounds damned fine to me, and at an MSRP of $150USD (street price touches $100 from time to time) are quite a nice deal.

Not a DIY project, true, but it lets you get on with fiddling with the recording instead of with the monitors.

Hope this helps!

[HardRockHenry]

I have the logitech x530's they're amazing.

[Guitarist]

I imagine this approach would great for guitar as well. Move the bass to a 15 (or 12 or 18") and just send the upper mids to small, enclosed (or not) speakers. These may be hard to come by with a rool off at 5.5K but hey! Any suggestions?

You could really make a cheap stereo tube output (small champ sized transformers or even smaller) if you moved the bass in mono, right?

[Steve Conner]

Hi Joe

I think the deal is that you can EQ as much bass as you like out of small speakers... at low volumes. If you want it loud, you have a pair of induction cone launchers.

For loud, deep bass, you need a large speaker cabinet, end of story. With a small speaker you need to sacrifice either volume, or bass extension at high volume. Sure, it's possible to make small speakers that go very low with poor efficiency, and then drive them with high-powered amps to compensate. But the level of bass you can achieve is still limited by voice-coil burnout or cone launching.

At home I use a pair of Dynaudio BM5s that I bought second-hand, driven by a big home-made MOSFET power amp. I wanted Dynaudios for years, ever since I first heard them in someone else's studio that I was helping to set up. They were the first speaker I'd ever heard that actually made a perfect stereo image. (I realise now it probably had more to do with the nice acoustically treated room they were in, but I'm happy anyway...)

Before that I had the weird-shaped Blueroom mini pods, but I hated the bass from them. I ended up building an active crossover so I could offload the low end to a Paradigm home theatre sub. But the BM5s do fine without the sub.

Rod Elliot has a nice "PC Sound System" project:

http://sound.westhost.com/project73.htm

[Glass Snuff]

Joe, I've been playing with hifi speakers for over 40 years, and I've always been fond of the FE-103.

Sounds like you've got a pretty good handle on it. The basic problem with a wide-excursion driver of small diameter is that at some point the area of the surround exceeds the cone area. This doesn't sound so good.

Perhaps more importantly, we no longer have a stiff panel vibrating in the room, but something more like a plunger, with attendent impedance-mismatching to the air load and perhaps even Doppler problems if we get carried away.