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Old 19th December 2012, 09:56 AM   #1
pkozul is offline pkozul  Australia
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Default Fostex FE87E Recommended Back Loaded Horn

Hi there,

A relative newbie here. I'm still waiting for enough free time to start my first DIY speaker build, but in the meantime, I ended up buying a pair of these Fostex horns for a really good price (I think their binding posts are worth more than what I paid!!!).

Excuse the aspect ratio... wasn't sure how to get that right...

Click the image to open in full size.

Click the image to open in full size.

The actual speaker plans can be found here:

http://www.madisound.com/pdf/fostexcabs/87e_revencl.pdf

As for the sound, it's pretty good to my ears although there is not much in terms of highs. Hard to explain, but the sound is just not as clear as I'd hoped. Bass is lacking, but that's OK as I've now hooked them up to a subwoofer, crossed at 150 Hz.

I have no idea if there is any stuffing in the speakers. I cannot see any behind the driver, and could not notice any up inside the mouth of the horn.

Any suggestions on what I could try to improve the sound?

I have no idea how many hours they have on them, so maybe some more burn-in time?

If stuffing might help, how much and where should I place it? I only really have access to the horn mouth, and behind the driver, as the speakers are all permanently glued up.

Also, does their location make much of a difference? They are currently sitting on a tallboy, but maybe on the floor would be better?

Thanks!
Pete
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Old 19th December 2012, 11:10 AM   #2
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1 - what are you comparing to?
2 - how long have you listened to them for?

I wouldn't expect a small Fostex driver to ever be short on clarity or treble.

Sitting them on the floor would improve bass output, but even so; you're using a small driver with tiny excursion - a subwoofer will (IMO) always be required.

Chris
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Old 19th December 2012, 11:18 AM   #3
xrk971 is offline xrk971  United States
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That's a great deal if you got them for less than binding posts.
I think the FE87's are known for great high end so not sure why you are not hearing that. I think some stuffing at a minimum needs to be in chamber behind driver to absorb back reflections. This may be drowning out the treble, experiment with it but I would guess a pretty dense amount is needed. Makes a big difference in bass output too. Some can also be added behind chamber with a piece of wire coat hanger to push in place.
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Old 19th December 2012, 07:57 PM   #4
pkozul is offline pkozul  Australia
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Hi there,

Chris, I’m comparing the sound of these to other speakers I have at home (mostly 2-ways) such as Inifity RS2, Mission M70, etc. I’ve only had them running for about 10 hours or so as I just got them a few days ago. Maybe I should give them a hundred hours or so before I really jump to any conclusions….

xrk971, thanks for the suggestions regarding stuffing. I will try experimenting with this and see how things go. I have lots of leftover polyester ceiling insulation batts, so will try using that. Is it OK if the tightly-packed stuffing behind the driver touches the actual magnet, or should there be a gap between them? (BTW, great threads on foam core enclosures… tempted to make the cornucopya my first build!!!).

In the meantime, I stumbled across this article… (translated from Italian)…

http://digilander.libero.it/giovanni...ia/monovia.htm

Quote:
Some time ago, the brilliant and very kind Tony Gee of Humble Homemade Hifi we exchanged a few emails, I specifically asked him his impressions of the project and some advice on soundproofing, carry a few phrases of interest:

The FE87E horn looks like a very good design to start with. All important is a sturdy construction with thick panels to minimize vibrations. Experiment a lot with the position and amount of damping material, this has a strong effect on the overall response of the system. Full-range drivers can get congested on complex material but they do excel in spatiality and dynamics considering the small size of the driver.

I tend to have slightly denser damping material at the beginning of the horn, then decrease the amount and density towards the mouth of the horn. The more dense damping material the dryer and tighter the sound will be, but too much damping will kill the bass. The less material the more dense dynamic and fuller the sound, but too little damping may make it sound blurred.

So, to sum up, a bit all the recommendations and the various readings show that the problem is on the horns spurious traveling inevitably led in and create an annoying boom or tail acoustics that "dirty" the working frequencies for which it was designed the horn itself (usually for the single screw from the low range).

In general it is convenient to intervene in the initial area of the trumpet, around the driver, so as to immediately interrupt the propagation of unwanted frequencies. The rest of the duct can be completely free but in the case of horns folded can be put, but their finishing, the sound absorbing material on the outer side of the curves.
Cheers,
Pete
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Old 19th December 2012, 08:12 PM   #5
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Quote:
Originally Posted by pkozul View Post
Hi there,

Chris, I’m comparing the sound of these to other speakers I have at home (mostly 2-ways) such as Inifity RS2, Mission M70, etc. I’ve only had them running for about 10 hours or so as I just got them a few days ago. Maybe I should give them a hundred hours or so before I really jump to any conclusions….

Cheers,
Pete
Hi Pete,

I'd advise you listen only to the Fostex (plus the subwoofer) for a while - commercial speakers will often have boosted treble in order to sound more exciting. If your ears are accustomed to this, it'll make these Fostexes sound lifeless.
Let your ears adjust to the Fostexes for a while, see what you think then.

They may well need breaking in (ask the seller if he/she used them much), but there won't be much change in the treble there.

Chris
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Old 19th December 2012, 08:28 PM   #6
xrk971 is offline xrk971  United States
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It's ok for stuffing to touch magnet. Mine is surrounded like a nest. Old pillows make great stuffing sources. Thanks for the kind words. The Cornu made with foam core is easy enough for a first time project. Try it, you will be so glad you did.
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Old 19th December 2012, 08:38 PM   #7
pkozul is offline pkozul  Australia
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I will let the speakers burn in for at least a hundred hours (knowing my wife will ask me why am I leaving things switched on and running!!!), and then try the stuffing after that.

Yeah, the cornu is really appealing and I can imagine it fitting in well in almost any room in the house... might also give me an incentive to rekindle an old hobby of drawing/painting :-) Perfect canvases for my 2-year old son and I to get creative with some paint brushes...

Thanks again guys.
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Old 19th December 2012, 09:11 PM   #8
xrk971 is offline xrk971  United States
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Micro cornu is perfect for kid's room. The cornu would probably work very well with FF87e in a 24 inch cornu. Similar to vifa tc9fd in size.
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