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JRace 17th February 2006 04:08 PM

Running full range (FR125) driver direct to amp...??
My question is, what are the drawbacks to having nothing in line between the amp and the driver? (ie no crossovers, resitors, circuts etc)

I have read about baffle step issues, baffle difraction issues, and am unsure if I do need to compensate for anything with these speakers.

I have built a pair of FR 125's in a small sealed 7lt box. This is my first DIY speaker and have chossen this driver to keep things simple. I have just constructed a 7ltr sealed box with 3/4 mdf. The box is not finished as I am still testing it out before I put the finishing touches on it. I may still port the box.:smash:

The box is 8" wide, and 12.5" tall.

My initial listining impressions (<2hrs total run time on drivers) are that this driver is more than cabable in the highs, however the lows seem slightly reduced. Now being my first time with full range drivers I do not quite know what I should expect.

The room is very open, with the speakers 8 ft from my seat, and 6 ft between them (cannot change at this time). One is 3 ft from the back wall and the other is 5 ft. THey are on stands which puts the driver at my ear height when I am seated.

They are being powered by a Marantz sr5300 AV reciever.
Then end gaol for these speakers will by in my home office as computer speakers placed on my desk.

What am I missing out on by not having any circuts in my design?


sreten 17th February 2006 04:29 PM


the probable answer is not much.

The sound nearfield on your desk will have much
more bass than the sound farfield on open stands.

Nearfield speakers usually do not have baffle step compensation.


Vikash 17th February 2006 04:49 PM

If you turn your question around a bit to does the FR125S need filters, then this may be of interest:

I think 7 litres might be a tad small to go ported with. I definitely prefer the 125 ported. With sealed cab I found stuffing should be kept to minimum as well.

You can use this driver without any filters if you want. It has a few peaks in the upper end which on paper require attention, but me ears don't mind. I also don't see a clear BSC requirement in my measurements.

chrisb 17th February 2006 06:32 PM

A bipole pair of WR/FR in 25litre sealed box sounds wonderful, and trust me, doesn't require any BSC

For DAF (domestic acceptance factor) alone I quite prefer these to the all variants of the straight bipole MLTLs with the same driver complement.

Not enough bass output is generally NOT a problem with these drivers in an appropriate box. I think 7l is definitely too small; you honestly might be better off doing over again.

For ported enclosure, the 13 liter monopole mini-Onken is quite amazing as well, but with the bevelled treatement of the front/sides, is a bit of a complicated build compared to a simple sealed or conventially ported box.


I guess it would help if I read your post fully to understand the application before mouthing off - for small nearfield monitor you're probably restricted to height and width of enclosure but not the depth. If you could live with the dimensions, the folded MLTL for the following FE127 MLTL could work nicely as well:

JRace 17th February 2006 06:34 PM

Thanks for the info. I will read through the other thread for more info.

Seeing as the end goal is a near field monitor sitting on a computer desk with the future possiblity of being augmented with a powered sub I was not too concerned wit the inital low bass ouput.

sreten 18th February 2006 01:12 PM


Originally posted by chrisb
A bipole pair of ......... and trust me, doesn't require any BSC


its not a question of trust, bipoles by definition do not exhibit baffle step.


Vikash 18th February 2006 10:40 PM

Just thinking out loud here.

But what about drivers which do not require BSC (or as much of it) due to their inherent response (TB W3-871S, or even the FR125S if my measurements are to be believed). Using them in bipole config would tip the bass the other way wouldn't it?

Or should I say BS is not wholly compensated for simply by using a bipole config neccessaily...

Vikash 18th February 2006 10:46 PM

Ignore me. Of course its completely compensated for. It just doesn't mean the result will be a flat FR.

JRace 21st February 2006 04:39 PM

Well I moved the speakers into my office, and am powering it with an onkyo 603 av receiver (for now).

The speakers are sitting on my desk, with the drivers just shy of ear level. Pleasantly the low-end response has improved.

Once the weather warms up I will be finishing the speakers with veneer (species undecided)...when that happens I will post some pics.

Dumbass 21st February 2006 07:07 PM


Originally posted by Vikash
But what about drivers which do not require BSC (or as much of it) due to their inherent response (TB W3-871S, or even the FR125S if my measurements are to be believed). Using them in bipole config would tip the bass the other way wouldn't it?
I think it all depends on how you tune the enclosure. I think some people tune enclosures to have a bit of a hump in the hundreds to compensate for baffle step dropoff. Obviously you wouldn't want to do this with a bipole setup.

I also wonder how far from back wall is recommended for bipole.

Rear-firing driver is still producing high freqs, allbeit indirectly.

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