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Multi-Way Conventional loudspeakers with crossovers

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Old 20th March 2007, 10:32 AM   #1
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Default LS3/5a vs Mission 751 vs first DIY project

Hi,

Bit of a speaker newbie here - I am mainly into DACs and CD players.

I own some Mission 751s, which I love. I hope one day to design an active crossover for them and bi amp them (removing the passive crossover).

I also have recently gained the chance to acquire some Chartwell LS3/5a's, and a wilmslow sub to go with it. I wouldn't touch these, due to their age, but if I had them, I could justify modding the missions (as I would have a backup plan).

Firstly, how do you think these compare?

And, if I was to build my own pair of two way speakers, with a reasonable budget , how would I fare compared to these two?

Cheers,
Phil
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Old 20th March 2007, 12:11 PM   #2
SimontY is offline SimontY  United Kingdom
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Hi Phil,

I can't answer all of your questions but I would have to question the sanity of making a small 2-way bookshelf active. The main benefit of active crossovers is to separate bass from the rest, but in a 2-way this doesn't happen - you simply separate the tweeter from the rest, which costs you money and will probably worsen the sound. Most of the power goes into the mid/bass driver so using multiple amps won't massively lower distortion or increase maximum output.

With this sort of speaker you might be wise to upgrade the capicitor that runs in series with the tweeter to a very high quality type (polypropylene film and foil). You will also want to upgrade the inductor that goes in series with the mid/bass driver, as on these speakers it will probably be quite cheap. If it's not a huge coil replace it with a thick-gauged air-core inductor from Audiocom or similar.

Although as I've been waiting for some inductors from them for nearly 2 weeks now I don't like to recommend them. There is a lack of alternatives selling good coils though (I know of none in this country).

The beauty of building your own speakers is being able to tailor them to your own tastes. In value terms they probably will struggle to stack up to 2nd hand commercial speakers, but they will be your pride and joy!

Four or five years ago I still had commercial speakers, B&W DM602 s2, nice speakers. I replaced them with some home-made 2-ways using an Audax 8" plastic mid/bass and 1.25" soft dome tweeter. I would say the speakers sounded quite different but neither was obviously better really, except in the treble, which was far superior in mine, and the bass that was better in the B&Ws. The mids were perhaps more inviting in mine, probably due to the plastic driver.

Simon
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Old 20th March 2007, 12:38 PM   #3
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Hi Simon,

Thanks for the reply.
I'll explain my lunacy a bit....
I'm interested in trying an active crossover, mainly because it would be an interesting exercise and I want to. But also because, at line level, into a several kohm load of a power amplifier rather than 8 ohms, you have a greater choice of components and an easier design environment (you could even use silver mica caps throughout - I know Rowe would ;-)

Also, I believe there is a theory that, without the passive components in the way, it is eaiser for the amp to drive the speaker due to damping factors (I really am blagging it now lol).

So that is why I want to try it, even if it is just replicating the passive that is already present to start with, but before the amplifiers.

I do agree, that for making life easier for the amplifiers, just worrying about the bass would make sense wrt active crossovers.

So, its mainly a 'because I can' approach to the problem. But, I'm also interested in whether I can expect results from my own work (they'd probably start with passive crossovers.
Its good to hear you're happy with yours.

And, I specify making my own 2 way, because I think it be foolhardy to do a three way for my first speaker.

Have you tried Wilmslow Audio? They may be a bit pricey, but they sell air and iron cored inductors.

Cheers,
Phil
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Old 20th March 2007, 12:47 PM   #4
SimontY is offline SimontY  United Kingdom
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Fair enough then. You certainly can expect to get better bass for removing the series inductor and having the amp directly wired to the amp. Re. components - just bear in mind that the signal now has to go through extra op-amps to do the crossing over! So it's time for more sockets and more listening tests! lol

About mine...my younger brother has had them for years and really enjoys them. I've moved onto something else and I'm still not 100% happy with them (see other thread here, lol). Actually I'm interested in adding an extra bass section and actively biamping. So I am very interested in your journey. For me this route will give me true party levels and hopefully much lower distortion. I also generally enjoy feeling the drums on rock music.

Yes I am aware of Wilmslow Audio. Their inductors aren't good enough to be honest, just look at the DCR (resistance)! And the iron core ones look like the boggo jobs you get in ordinary speakers. I ordered some iron dust core ones with nice low DCR from Audiocon to turn my speakers into 2.5 ways. That is if I ever get them....

Simon
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Old 20th March 2007, 01:07 PM   #5
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Hi Simon,

I like feeling drums too :-)
This is one of my many pie in the sky projects (i'm a bit slow as you know), so don't expect results for a while yet.
I probably would use a sub as well at some point.

The opamps in an active filter are a compromise in some respects. Best way to find out is to try it.
I assume the Linkwitz-Riley filter is probably the best way to go.

So how many bass sections do you have at the moment to require another one?!

Cheers,
Phil
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Old 20th March 2007, 01:39 PM   #6
SimontY is offline SimontY  United Kingdom
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Well Philip...

I have 2-way MTMs with 6.5" drivers, good to about 45hz. Then a large 15" sub good to sub-20hz. The problem is my main mid/bass drivers only have 3mm xmax and distortion below port tuning is theoretically very high, as so kindly pointed out by DIY-Audio speaker-critic "Streten". The drivers are low QTS and so sound dreadful sealed (shut in with no dynamics or bass whatsoever) and the cabinets are nice and cost me lots of money so my only "solution" (implies there's a problem, which is only half true!) is to actively roll-off the mid/basses and insert a more robust bass speaker underneath. I have in mind twin cheap 7" drivers per side, as I have loads of these and they sound pleasant. These will work down to about 40hz, which provides an additional benefit of crossing the sub even lower. A massive sub like this is not something you want to hear above 50hz! Also these heavier 7" drivers should bridge the sound quality gap between low-mass 6.5" drivers and a large, heavy 15" driver. It also means the mid-range will be lower in distortion and cabinent resonance will be reduced. Sorry for the long post

Simon
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Old 20th March 2007, 01:57 PM   #7
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So, you'll have a 4 way system then?
What frequency will you roll off the 6.5" drivers?

Sounds like a great project! Good luck.
I can see how active filtering can help you here. Cramming those two speaker channels in before the midrange is going to be fun.

At the moment, I'm interested in really are the LS3/5a's any good compared to a DIY project. I could buy them, or begin my loudspeaker building hobby instead (although I am going to build a sub first). I think I know the answer - even they are regarded classic.

Cheers,
Phil
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Old 20th March 2007, 02:03 PM   #8
SimontY is offline SimontY  United Kingdom
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Yes it would be 4-way I guess, with baffle step correction on the mids, so sort of 4.5 way, or 3.5 way plus sub. I'll experiment, but I'd imagine the x-over there will be around 200hz - allowing the power to be split nicely but not letting the cheap drivers do too much upper bass! No reason I can see for not overlapping so it might as well be 1st order. Experimentation and learning is the name of the game.

It sounds like you're veering toward the DIY project option. I hope you do as ultimately it should be more rewarding and could lead to great things.

Let us know what happens.

Simon
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