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Lostcause 23rd September 2005 01:24 PM

MLTL correction circuit position
Hi guys, just a quick question...I hope!
I'm making a set of FE207E MLTL's and (because of restrictions) I would like to place the correction circuit and indeed my system on top of one of the speakers.
Is this going to affect anything, magnetic fields, interference etc?

Scottmoose 23rd September 2005 06:36 PM

I assume you simply don't want the circuit inside the cabinet, which is fair enought -that's a hostile environment, particularly in a TL.
Will it be a problem in interference terms? Probably not, providing they're not slammed up against something hurling out a huge electro-magnetic field. But this is going to be very much a suck it and see situation. In terms of vibration, it can't be worse than being inside the cabinet itself, though I'd double the top panel, if you haven't already. The other possibility: is there any especial reason why you want the circuit near the speaker anyway? They could both go nicely in a small box with the rest of your gear. Just a thought.

Scottmoose 23rd September 2005 09:38 PM

OK, point taken -I didn't read the post carefully enough (Glasses! Where are my glasses?) Sorry about that. Having re-read, I gather you're intending to place all your gear, including circuits, on top of one of the speakers.

Hmm. Awkward. Generally speaking, I would say that this is possibly the worst place your gear could possibly be. Is there absolutely nowhere else your equipment could go? If there's no floor room near them, and there's some wall-space available, you might want to think about placing it on a shelf, so long as it's a solid wall, not a partition. Even if you have to mount the equipment on the other side of the room and use long cable runs, it'd be worth it: 12AWG wire (or larger is best for long runs) isn't impossible to hide with a little creative cunning.

Assuming you can't put your gear elsewhere, what are the possible issues? Well, as the very minimum, I doubt if it'll do the imaging much good having a quantity of boxes piled on top of one speaker. However, if there's no other option available to you, then that's it, and whether you're worried about it or not, there isn't much you can do about it. On the up-side, I don't think [electro]-magnetic fields will be much of a problem unless you're unlucky. If you do nothing else, put a ferrite clamp on your signal leads, just in case -it'll cut down possible RFI a bit.

My major concern would be with vibration. The top of an MLTL has a lot of stress, which is why I'd always advise doubling the top-panel. In this case, I'd say that'd be what you'd need to do at the very least. Good old Newton also says this is the bit of the speaker (i.e. the top) which will move the most, as the driver is mounted closest to this end, so make sure they are solidly clamped to the floor. Forget spikes: with those things, you create an acoustic cavity under the speaker, which is the last place you'd want one of those. Try sticking them on a marble or veneered concrete slab with a sheet of Blu-Tak or an equivelent -make sure there's no gap between any part of the speaker and the marble / concrete / whatever plinth it stands on. It makes a real difference, believe me, and consts very little. Spikes don't couple speakers to the floor well at all, and being metal, they also resonate slap-bang in the middle of the audio-range.
Try to isolate all your gear on top of the speaker with large dots of Blu-Tak too. Vibration isn't usually an issue with solid-state electronics -they don't in themselves vibrate, but if you place them on or near a vibrating item, they will, and it then becomes more of a problem. The Blu-Tak will help a bit there.

Hope some of this helps.

Lostcause 24th September 2005 10:57 AM

2 Attachment(s)
OK then, so you dont feel that there will be an issue with magnetic fiels and interference to a great degree (or at all?) but you believe vibrations are the big issue here?
So....if I place the speaker on marble with a dampener between and double up the top section........and introduce a dampener between the top and my system that cancels out ALL vibration....

Would this be better than having 4.5>5M runs of cable?

I could put it on a shelf above the speakers at a pinch, definately not the floor though (babies!!).

The wife aint gonna be happy when she sees the size of these things antway!

MJK 24th September 2005 01:16 PM

If you are going to tuck the speakers into those corners, you might get away without a correction circuit or with just a small resistor (1 - 3 ohms) in series.

Why don't you want to place the circuit inside the enclosure? I don't remember what the reason for keeping it outside was, it could be outside for a month until you get the values you like then put it inside.

Amp placement and cable runs in a room that shape and size are tough. No easy answers.

Lostcause 24th September 2005 01:35 PM

Hi Martin, I've e-mailed you directly on this one in the past. (Lee Robinson)
I was going pop them inside eventually, I thought it would be easier to keep them outside until I was happy with the balance. Then I thought....might as well keep em outside!
Dont go telling me I may not need that correction circuit...not after the fiasco of importing those Super Q's!
I'll try both placements of the system to ascertain the difference.

MJK 24th September 2005 01:49 PM

You can still use the super Q's, that would be better then just a simple series resistor. But you may be able to use a lower resistor since the corners will reinforce the bass. The only way to know for sure is to try.

Lostcause 24th September 2005 02:10 PM

Cheers Martin, I'll try the lower values and work my way up....

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