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Old 21st September 2006, 11:17 PM   #1
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Default FE126E in a 23 litre enclosure

will a 23 litre cabinet work and if so should I leave it sealed or bass reflex? What kind of low end response in such a box should I expect?
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Old 22nd September 2006, 01:04 AM   #2
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Hi audiophile36,

The response should be similar to the 1/2 space respose shown in the data sheet,
http://www.lautsprechershop.de/pdf/f...h=%22fe126e%22
minus baffle step. 23 litre sealed cab would be close to a infinite baffle for this driver. You could try a port to give a shelved bass alignment. You will need to use a sub if you want bass. This driver will not produce much bass in a sealed or ported enclosure. It's a nice driver though, I use mine (at the moment) in a small sealed cube roughly 2 litres or so (haven't calculated this, the driver takes up most of the space!) gives a rolloff below 180Hz and Q around 0.7

Regards Philip
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Old 22nd September 2006, 03:05 AM   #3
holdent is offline holdent  Canada
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I modeled the Fostex recommended BR for the FE126E using King's MathCad models and got surprisingly good results using the following paramters:
- a distance of 32" from the baffle to the back wall
- stuffing on all walls with a density of 0.25 lbs/ft3
- a 4.5" long port with a 1.0 inside dia. (slightly different than the metric dimensions given in the Fostex design).
- a BSC of 10 ohms and 2 mH (center freq of 800 Hz with 8 dB of attenuation)

The plotted corrected SPL and phase response was very good without stands (see below). Modeling speaker on 24" stands and/or closer to the walls does not provide as good a result (as expected). Still I was very surprised and impressed particularly after spending so much time working a modeling the FE126E in a BLH. Though the BLH has a higher sensitivity I kept running into a trade off between getting good bass extension, smooth response in the midrange, and decent cabinet size.

I plan on building pair of these cabs next and get some "real world" measurements.

Click the image to open in full size.

Oops - just realized that I attached the wrong title to the chart above. It should read Plotted Corrected SPL Response for the System
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Old 22nd September 2006, 06:42 AM   #4
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That's a pretty good response, all things considered. I'm impressed. However, keep in mind that those 10ohms of resistance in the BSC circuit will dramatically reduce the sensitivity of the speaker (it'll drop to about 83db for 1w), meaning you'll need a pretty powerful amp to feed them.

It's a myth that horns don't suffer from baffle-step -they do, but it's often less of an issue for them (depending on the design and their positioning), and you can usually keep sensitivity up more easily, which is useful.
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Old 22nd September 2006, 11:50 AM   #5
holdent is offline holdent  Canada
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Ahhh... very good point. I got so focused on performance below 1000 Hz I neglected to think about what it would do above. Here's the same cab without a BSC:

Click the image to open in full size.

Now I'm not sure where to go with the BSC - Scottmoose can you make a suggestion?[
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Old 22nd September 2006, 01:56 PM   #6
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Without the compensation circuit it will sound very thin, mid and treble forward, with lightweight bass. You can mitigate against this to an extent by ramming them back against a wall or into a corner, but that won't completely fix it.

A few other ideas. Active Eq is usually the best option for compensation if at all possible as it doesn't cripple sensitivity. if you have a pre/power amp you could look at line-level passive correction, providing your pre produced enough gain as of course it will reduce the signal strength to the power amp. Line level EQ design is not something I'm familiar with though, so I can't help with that. I really should read up on it at some point.

You could also try reducing the values in the normal BSC circuit a bit -keep the inductor the same as that determines the frequency above which everything is attenuated, and reduce the value of the resistor. On the graph it obviously won't show as much attenuation, but it's better than nothing. Try 5ohms if you're set on buiding these and see if that does the trick.

Other than that, a different enclosure might end up being a better way forward for you. Low Q drivers in BR don't often make the happiest combination. The Frugelhorn or my double horn design for example, and there are others too. Only problem with those is there're somewhat harder to build, and, of course, larger. Still, bigger is better when it comes to speakers...

Best
Scott
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Old 22nd September 2006, 09:53 PM   #7
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So what I am gathering from you guys is that the FE126E will have little bass and sound thin no matter what?The Omega Super 3 speakers use the same driver in a smallish BR cab and have satisfactory bass for my likings.The cab I intend to use has about twice the volume as the Omega Super3....shouldn't it have more bass in a bigger enclosure?
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Old 22nd September 2006, 10:14 PM   #8
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No, but it will never be a bass fiend in a resonant cabinet; Q is too low. It's not terrible (better than a 206 for example, though cone area helps the larger driver on the air-moving side), but not ideal.

Bigger = more bass? Kind of. Life doesn't quite work out as simply as that though. You'll end up with an extended bass alignment -a bass-shelf in other words. What will likely happen is that you'll get a decreasing response, which will then flatten some db below nominal before cutting off. Quite popular in the pre T/S days, Gilbert Briggs of Wharefedale frequently promoted this alignment. Thing is, he was using ~10in woofers. Note too that it's not a good idea to tune a driver too far below Fs or the midbass tends to go AWOL.

BTW, I thought it was the 127 that Omega use, though i could be mistaken.
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Old 22nd September 2006, 10:57 PM   #9
holdent is offline holdent  Canada
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When I looked at the plotted response without a BSC and estimated what the whole response curve might look like with a driver that is rated to be 94 db/W (m) it doesn't look too bad. I would estimate that there may be an elevated response between 550 and 1000 Hz that may be objectionable. Without building and measuring the cab I can't be sure.

If it does have an elevated response in this zone, is it possible to tame it using a notch filter (see http://www.carstereo.com/help/Articles.cfm?id=19). Do these filters work well or do they colour the sound so much that they should be avoided?
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Old 22nd September 2006, 11:53 PM   #10
MJK is offline MJK  United States
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I think the response looks very good for such a small driver. I could not resist and played with the model some, the only thing I would change would be to go for a little less baffle step correction. I found in some of my earlier speakers that when I corrected to a flat response the speaker sounded a little dull. When I reduced the correction a couple of dB the speaker sounded much better and the bass was still good enough. So I would change the circuit and start with a 1.5 mH inductor in parallal with a 7 ohm resistor. This produces 90 dB at the bottom rising to about 92-93 dB in the midrange at the top of the baffle step hump. Looking back at the FE-126E SPL curve on the spec sheet, it naturally rises a few dB above 2000 Hz so you would end up being about 92 dB efficient all the way up. If this was still a little bright you can always increase the resistance a little.

The stand is a different issue. Adding the stand produces a big null due to floor reflections. All I can say is that all of my speaker have the driver at ear level so I must be suffering the same type of response. Every speaker with a non-directional driver at 32 to 36 inches off the floor will have the same problem. It looks ugly in the calculations but I am not sure it sounds so ugly in reality.

Conclusion, I think this is a nice little design with a small driver. As long as you recognizing you will not get bass like a bigger driver would produce, I think it will work well.
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