[groundie]

hi folks, i must admit upfront that i am just an assemble-level diyer.
and about a year ago, i did just that, using Madisound cabinet and SEAS drivers,
i assembled a pair of speakers that actually sounded great!
what luck...

i did read quite a bit about the benefits of bi-amping with active crossover.
i was convinced and bought Behringer dcx2496 and extra amplifier for my
basic stereo music application.

now of course i have the itch to step up.
i basically am considering two options:
1) repeat the same assemble job but with SEAS Excel drivers; 2-way monitors
2) buy the Odin kit from Madisound without the crossovers since i will be active xo

some specific questions i'd like help with:
1) i have read some negative comments on thor/odin cabinets. but i should be able to tweak
the active xo to my heart's content and fix the issues. right?
2) i understand that mtm design offers better sensitivity with lower impedance but what other
general advantages does it have over 2-way?
3) i've read in so many places about "matched" pair of drivers. what exactly does that mean
that the tweeters are matched?

i'd appreciate any guidance in my research for next step-up.
cheers and happy 2009!

 

[JCD]

hi folks, i must admit upfront that i am just an assemble-level diyer.
and about a year ago, i did just that, using Madisound cabinet and SEAS drivers,
i assembled a pair of speakers that actually sounded great!
what luck...

i did read quite a bit about the benefits of bi-amping with active crossover.
i was convinced and bought Behringer dcx2496 and extra amplifier for my
basic stereo music application.

That's some good stuff you got there! Whenever I'm ready to step up, I'm going to be going the same route.

now of course i have the itch to step up.
i basically am considering two options:
1) repeat the same assemble job but with SEAS Excel drivers; 2-way monitors

The box size is dependent on the drivers that are going to be used. So, dropping different drivers into a box usually doesn't work. There are a few programs out there that help with the box size calculaion. WinISD and speaker workshop come to mind.

2) buy the Odin kit from Madisound without the crossovers since i will be active xo

This will give you the right box size.. however, the driver layout and crossover point are intertwined. To get a correct D'Appolito configuration, the driver separation is related to the crossover point. When done properly, it gives a super off axis performance (I'm pretty sure that's the main benefit) and a single point source (which I think all MTM's are going to give you).

some specific questions i'd like help with:
1) i have read some negative comments on thor/odin cabinets. but i should be able to tweak
the active xo to my heart's content and fix the issues. right?

I think there was some people who didn't think they were tuned correctly, resulting in a loss of bass output. I've heard second hand that the designer did this on purpose because he didn't think that the drivers could go as low cleanly. Whether or not that applies to the current design, I don't know. And maybe you've read something I haven't seen yet. In other words, take what I've related for what it's worth. :bigsmile:

2) i understand that mtm design offers better sensitivity with lower impedance but what other
general advantages does it have over 2-way?

See above

3) i've read in so many places about "matched" pair of drivers. what exactly does that mean
that the tweeters are matched?

Even with drivers that are the same model, the sonic characteristics of one driver to another are going to be different. Take a random sample of the same driver, and you will get Thielle/Small parameters that can be vey different. My understanding is that these differences are particularly noticeable in tweeters. A matched pair is simply a pair of drivers who have similar sonice characteristics (which can be traced to their T/S parameters).

i'd appreciate any guidance in my research for next step-up.
cheers and happy 2009!

Not sure how much that helps in the end, but hopefully I've cleared up some of the issues for you.

Or gave you more questions to ask..

 

[groundie]

hey jcd, thanks for your comments.
these are my current drivers: CA18RNX woofers and 27TDFC tweeters.
the ones i'm thinkin' to upgrade to are: W18EX-001 woofers and T25CF-002 millenium tweeters.
current cabinets are 14 liters.
since madisound sells front baffles for the Excel drivers, i just assumed that 14 liters would be
appropriate, at least not totally out of whack.

as i stated earlier, the extent to which i go as a diyer is basic assembly and some soldering,
not much more. but i do love that sweet sound of music!
thanks for clearing up "matching" tweeters for me; i will read up on Thielle/Small some to educate
myself a little. so, if i buy couple of excel tweeters, it's taking some chance, right?
but i'd think at that price point and seas' reputation that they'd be pretty close.
we're talking about quality control, correct?

another follow-up question:
i'm using a new Parasound amp to drive the woofers and a very old Hafler for tweeters in
my bi-amp setup. i have read elsewhere about the importance of using the same amps but
no one has explained why. can you elaborate on this?

thanks again for your help;
it is great to hear other audio lovers' (and more knowledgeable) comments.

 

[JCD]

hey jcd, thanks for your comments.

No problem! I'm always here to help someone else in this DIY addictio.. err.. hobby!

these are my current drivers: CA18RNX woofers and 27TDFC tweeters.
the ones i'm thinkin' to upgrade to are: W18EX-001 woofers and T25CF-002 millenium tweeters.

So, I'm ASSUMING the drivers you have now are an earlier version of the Odin kit. The latter ones are the current kit. If you're up to it, you can get all the details for the kit here.

current cabinets are 14 liters.
since madisound sells front baffles for the Excel drivers, i just assumed that 14 liters would be
appropriate, at least not totally out of whack.

There is sometimes more to it than that. If the crossover has a baffle step circuit built in to it, then the width of the cabinet is important as well. And as mentioned before, with a true D'Appolitto MTM design, the spacing of the drivers relative to the crossover point is similarly important.

as i stated earlier, the extent to which i go as a diyer is basic assembly and some soldering,
not much more. but i do love that sweet sound of music!

Building the speakers, even from scratch, isn't too hard. It requires some tools, but really isn't too hard in the end.

thanks for clearing up "matching" tweeters for me; i will read up on Thielle/Small some to educate
myself a little. so, if i buy couple of excel tweeters, it's taking some chance, right?
but i'd think at that price point and seas' reputation that they'd be pretty close.
we're talking about quality control, correct?

I would think so, but I don't know so. I'd imagine that a little EQ tweaking might fix any problems that crop up. Again, I'm guessing on this one..

A really good beginner book for DIY is Vance Dickinson's Loudspeaker Designer Cookbook. You can get the older version for $11 here or the latest version for $35 here.

Some T/S/ links
Link 1
Link 2

And this is the mother-lode of DIY information -- Elliot Sound Products.

That should keep you busy for a while. :nerd:

another follow-up question:
i'm using a new Parasound amp to drive the woofers and a very old Hafler for tweeters in
my bi-amp setup. i have read elsewhere about the importance of using the same amps but
no one has explained why. can you elaborate on this?

I actually disagree with this statement -- this brings up one of the good things about actively bi-amping, the ability to match the drivers with the amp.

Tweeters are typically much more sensitive than the mids which are typically a little more sensitive than the woofers. As such, you can get away with less powerful amps as you move from a tweeter to the mids to the woofer.

I think you could go with something like this:

• Tweet -- Class A, ~25-30watts
• Mid -- Class A/B, ~60-70watts
• Woofer -- Class A/B, ~150watts

And depending on the tweeter, you could maybe even go with something even less.

thanks again for your help;
it is great to hear other audio lovers' (and more knowledgeable) comments.

Oh, you thank me now, but so much $$$ later and you'll curse me! :demon:

 

[groundie]

mucho gracias for all the links;
i've got some reading to do.
yes, i bought into true bi-amping after reading Elliot's pages last year;
lots of good no-nonsense info.

my first enhancements of 2009 are a pair of speaker stands;
then, i can finally move the old B&W DM640's down to the TV room.
next decision will be to replace or not the old Hafler DH-200.
this thing really gets hot and has an audible hum when i put my ear down to it.
how in general can one tell if an amp needs work or replacing?
'cause otherwise, speakers sound fine.

 

[JCD]

I don't know enough about amps to answer your questions, but I'll bet these guys might..