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Old 17th September 2008, 02:52 PM   #531
ecir38 is offline ecir38  United States
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Read this , http://web.mac.com/scress1958/iWeb/S...e-Speaker.html (link is to the first metronome) and search for other threads on the metronome to find what other have done with this cabinet.

If I recall of what I read in my searches in the past is that the metronome doesn't require much dampening and most that have built them overdamped them and had to remove dampening for best results. I would start with no dampening, then maybe line the wall directly behind the the driver or just use stuffing above the driver then go from there.

I think you are over thinking this one. I understand you wanting to learn taking and understanding the measurements, but the real test is your ears. You have to have an idea of whether or not you like how they sound? I am not the best at or like to decribe how amps, speakers, etc. sound because usaually it comes down to personal preferance, but I do know what I like and don't.
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Old 17th September 2008, 03:16 PM   #532
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Hi Peter,

I've only just come across this as I've been quite busy over the past few weeks.

The bass discontinuity you are hearing sounds to me like the third harmonic of the cabinet/driver resonant frequency escaping from the base. If that is the true problem (not saying it is) then it is pretty easy to overcome.

What you need to do is stuff the top third of the cabinet or better still lightly stuff with BAF wadding down to the top of the driver opening. Don't compress the stuffing too much or you will kill the sound stone dead, producing a hard, shrill balance. Try taking out the lining and replacing with the wadding in the top half as I have suggested.

There are not a lot of these larger Mets around. The only other one I know of at the moment is Bill's (lousymusician) hemp 8 inch driver Metronome. His driver is different so his stuffing regime won't really help you. However he did a lot of tweaking with stuffing until he got the balance he wanted. His speakers made quite an impression at the 2007 San Francisco Burning Amp Festival, probably due to the work he put in tuning them to his tastes.

What Scott and others have said is quite true. Because the cabinets are designed to suit a range of drivers then the stuffing has to be worked out carefully, case by case, by listening rather than measuring until the most pleasing tonal balance is obtained. What we have tried to do with these cabinets is to make them suitable for a whole bunch of full range drivers. The downside of this versatility is that the stuffing regime is bound to be different for each driver mounted in the cabinet, so the listener has to tune them according to their room and their personal tastes. A pure engineering solution to this problem is not possible.

However I will say that when optimally stuffed these speakers are capable of stunning sound quality. I don't know of anyone who has built them being disappointed with the sound obtained.

Steve
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Old 17th September 2008, 03:16 PM   #533
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Basically, what the guys above said. It's got to be your call at the end of the day, because you're the one listening to them. i.e. damp / stuff to taste. Adding damping will progressively damp the output of the cabinet. Removing it will allow it to resonate more strongly. We can't tell you exactly what you'll like or not like though -some people prefer a slightly more resonant sound than others. The trick is not to over-damp things, which will appear to 'suck the life' out of the midrange.
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Old 17th September 2008, 03:18 PM   #534
schro20 is offline schro20  United States
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Quote:
Originally posted by ecir38
If I recall of what I read in my searches in the past is that the metronome doesn't require much dampening and most that have built them overdamped them
What does it sound like when it's overdamped? (Ok, I could put a pillow in there and find out that way... but is there a way to say what it sounds like?)

Peter
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Old 17th September 2008, 03:21 PM   #535
gus900 is offline gus900  United Kingdom
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So my FE127e Mets started with a lining of approx. 1cm carpet underlay on all surfaces but ended up with lining only on the back wall, and on the surfaces at the pointy end where my hand couldn't reach. How did I decide on this? It sounded better that way. Was it scientific? Not remotely. Do I have lots of experience? Nope, these were my first attempt at building speakers. My recommendation? Get on and build the things, you'll love 'em.
Cheers,
Gus
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Old 17th September 2008, 03:30 PM   #536
schro20 is offline schro20  United States
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Quote:
Originally posted by schro20

What does it sound like when it's overdamped? (Ok, I could put a pillow in there and find out that way... but is there a way to say what it sounds like?)
When I posted this I had not yet seen Scottmoose's response of "overstuffing sucks the life out." Ok. That's something I think I can listen for.

Thanks also to Steve for his suggestion. I will try those and just listen for a while.

And I promise not to post any more measurements!

Peter
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Old 17th September 2008, 04:13 PM   #537
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Nothing wrong with measurements: they're very useful things, but they aren't ultimately going to tell you exactly what something sounds like -they can tell you a lot, and give an idea of the general balance of a speaker (or whatever), but they have their limitations too.
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Old 17th September 2008, 05:36 PM   #538
schro20 is offline schro20  United States
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Default baffle step correction

Since the subject of BS (baffle step) correction is also a matter of taste it would seem that I need to try that and decide for myself (which I am eager to do). Looking at the metronome tables I find the recommendation 2.8 Ohm and 0.9 mH for a parallel RL in series with the speaker. Right now I don't plan on including the Zobel. Should I? For amps I'll start with Onyx SP3 A/B class tube amp or a
Sonic Impact gen 2 (since I have those sitting around I might as well start with them).

A couple of questions. Is this recommendation for values to be used as a starting point still considered the right place for the FE207e in particular if I don't do the Zobel at the same time? Since it is a parallel RL in series with the driver the overall response is a function of the driver as well and in that case the Zobel parallel to the driver might matter sonically. It certainly would from a filtering point of view, though I am no expert at passive filter design. What wattage on the resistor and what wire gauge on the inductance is recommended?

peter
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Old 17th September 2008, 06:04 PM   #539
ecir38 is offline ecir38  United States
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Default Re: baffle step correction

I can't help on crossovers but I am sure that the other members can help you out with that. One thing I think that might be recommended is that a min. of 200 hrs on this driver would be needed before attempting fine tuning a crossover network. Once you get them both built I would run them 24/7 for awhile facing each other with a blanket thrown over them. I know my FE127e's had took at least 200hrs before sounding good.

I would love to hear what your final results are on the crossover when that time comes.
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Old 23rd September 2008, 01:37 PM   #540
ecir38 is offline ecir38  United States
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Default Re: baffle step correction

peter, any updates?
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