need ideas for compact musical speakers

[maleemi]

I would like to build a pair of compact (about 7-8 liters internal) speakers that will be used for critical listening in a small (12ft x 14ft) room.

Primary requirement is the ability to reproduce acoustic and vocal material with a high degree of accuracy but I'll also be listening to some rock and jazz. If necessary, low end extension may be sacrificed for musical fidelity but high frequencies must be smooth with no hint of harshness. The speakers will be placed several inches from the back wall and about 3 feet from side walls on book shelves.

FWIW the speakers will be driven by a diy chip amp. Most likely an audiosector LM3875 or LM4780 Kit

I'll be building them out of 3/4" mdf and either a sealed or vented design is acceptable but since they'll be close to the rear wall a vent in the back may not be optimal.

Budget is around $75.00 per speaker for driver and crossover components. I'm not adverse to using full range drivers if that will give the best results

Can anyone recommend drivers and (if needed) a crossover design that will work for my project?


Best Regards,

Marcel

[dondiba]

hi,
why not fostex fe103e?
the fostex recommended enclosure is a horn but plenty of other more compact designs are available on the internet
a simple zobel will be useful to cope with some harshness in hight frequencies
regards
dondiba

[oshifis]

My musical preferences are similar and I also had surprisinly good result with a back-loaded small horn (Buschhorn) using Tangband W3-871S, its height is 30".

[gtforme00]

How about Madisound's Swifty ? The drivers cost 27 and crossovers 35 for each speaker. Specifications and plans are in this datasheet .

[planet10]

The (modded) FE127 would be my 1st choice, We have done boxes of 13 liters & 4.5 lityres that are quite good (bigger one goes lower and is a bit more open) so a box the size you want should be doable.

Given the the chip amp the CSS FR125 is also a viable alternative.

dave

[maleemi]

Originally posted by planet10
The (modded) FE127 would be my 1st choice,

planet10;

I was looking at your website and the fe127 did interest me. One thing that concerns me about the fostex's is that most of the threads I've seen about them indicate the need for a zobel or some other shaping circuit to deal with the resonance peaks. Do your 4.5L and 13L designs use any kind of shaping circuit or do your modifications address the resonance peaks. As i said in the original post I'm hoping for a design that gives very smooth response, hopefully without a lot of trial and error experimentation.

Also are your 4.5L and 13L enclosures tuned to 71hz per the fostex data sheet or have you found other tuning to work better?


Best Regards,

Marcel

[planet10]

Originally posted by maleemi
I was looking at your website and the fe127 did interest me. One thing that concerns me about the fostex's is that most of the threads I've seen about them indicate the need for a zobel or some other shaping circuit to deal with the resonance peaks. Do your 4.5L and 13L designs use any kind of shaping circuit or do your modifications address the resonance peaks. As i said in the original post I'm hoping for a design that gives very smooth response, hopefully without a lot of trial and error experimentation.

Also are your 4.5L and 13L enclosures tuned to 71hz per the fostex data sheet or have you found other tuning to work better?

The whole point of the cone mods is to deal with the cone problems at the source instead of band-aiding them with a filter (a filter doesn't fix the problem it just tries to hide it).

Without looking at my models i couldn't tell you what the tuning frequency is (i am more concerned with the shape of the curve) -- and those are only a 1st step as the cabinet designs are such that they are not true BR and the model just gives me a starting point.

dave

[MJL21193]

Originally posted by maleemi


One thing that concerns me about the fostex's is that most of the threads I've seen about them indicate the need for a zobel or some other shaping circuit to deal with the resonance peaks.

The Zobel is a necessary part of most crossovers, not just for FR drivers. It counteracts the impedance peak at the resonant frequency. This actually improves sound quality and response.

[planet10]

Originally posted by MJL21193
The Zobel is a necessary part of most crossovers, not just for FR drivers. It counteracts the impedance peak at the resonant frequency. This actually improves sound quality and response.

John,

You got that ALL wrong. A Zobel flattens the impedance rise in the high frequencies due to voice coil inductance.

What you describe (resonance trap?) is only used on tweeters (and maybe mids), the parts values needed for a woofer or a full range would be totally impractical

If you use the prefered high output impedance amplifier the extra power where the rise in the impedance at LF & HF happens helps the full-ranges response where it is needed.

dave

[MJL21193]

Originally posted by planet10


John,

You got that ALL wrong. A Zobel flattens the impedance rise in the high frequencies due to voice coil inductance.

Not wrong at all. True I failed to mention the impedance rise above resonance, but it was implied. The Zobel will very effectively reduce the impedance peak as should in this graphic: