SEAS Thor's Complete

[emack27]

Just finished construction of SEAS's Thor speakers http://www.seas.co.uk/acatalog/THOR.pdf. The sound from these speakers are in a word "Awesome." I compared them with my set of Denon DJ headphones (retail $150 US) and astonishingly I could not tell the difference between the two. However, IMO they do have their shortcommings and I am still trying to figure out why this is. When running a tone generator and sending frequencies from 30 to 150hz. they seemed to produce a standing wave around 100 to 120hz. and the frequency response at these frequencies were dramaticly lower. I am still trying to figure this one out. Maybe it's my room accoustics or maybe its a flaw in my construction of the cabinets. Either way I don't know. Low frequency response is very dependant upon proper placement. I have placed them to produce a 12db per octave rolloff at about 45hz which is what the manufacturer stated in the specs. What's amazing is that in the listening area you get the low frequencies but if you move out of the room the low frequencies are almost indiscernable. It is hard to believe that (4) 6.5 inch speakers can produce such low frequecies. They have a very large soundstage and no coloration of vocals which I have found in JM Lab's Focal speakers. I constructed them using 1" MDF throughout except the transmisssion line and didn't use the stand but simply extended the side walls to be 4" longer. Overall, I am very satisfied with them. The problems that I have found in construction is that the a few dimensions in the original spec's using 3/4" MDF and the spec's at SEAS's website using 1" MDF are slightly different. This caused a slight problem during construction and before you begin go over every stage before acutal construction. Another problem I found is the unusual speaker cut-outs. I went through many front baffles before getting them right.
The next step is to apply the veneer. I'll supply pics when I am done.

[Geoffcin]

Just finished construction of SEAS's Thor spe[IMG]"C:\Documents and Settings\Eric\My Documents\My Pictures\Thor-liten.jpg"[/IMG]akers

We'ld all like to see it!

[Feanor]

Just finished construction of SEAS's Thor speakers http://www.seas.co.uk/acatalog/THOR.pdf. ...

These Seas designs have be around for years, I think. Also, various small manufactures seem to have copied the designs with pretty much minor variations. Obviously they use very high quality drivers, and that, given you have to use two mid/bass drivers, is a problem with them -- they are expensive. For that reason I have never been much tempted to build a pair.

The crossover design is interesting to me, a DIY newbie. I guess it is a computer aided design the aims to minimize the number of components used, (no doubt that is a good thing). For example it's not immediately obvious to naive person like me what the role of the parallel inductor is in the woofer section, nor the parallel capacitor does in the tweeter section. I suppose they serve some sort of notch filter purpose but I'm clueless beyond that.

I note that the low pass filter appears to be 2nd order, which is a little surprising given the high frequency resonances that the Excel mid/woofers exhibit. I would have thought that a 3rd or 4th order filter would have been specified -- but what do I know!

[kexodusc]

I got to hear most of Madisounds Seas kits last year at a DIY meet. The THOR's are as good a kit as I've ever heard. You don't see many kits above $1000. These aren't out of place beside many $5000- $10,000 speakers. A lot of speaker companies (ie:Tyler, Joseph Audio, etc) have $5000 speakers with the same drivers, minuse the T-line. T-lines have a sound that's very unique. If I wasn't so impatient, I'd build all my cabinets with lines.

A good DIY-er could no doubt extract even more performance out of the drivers, but for a convenient kit package that offers real high-end sound these are great.

emack27:

The problem at 100-120 Hz is almost certainly room induced to some extent (the design itself should be fine, even if the cabinets have an issue, that would show up much lower in frequency) I'm surprised you aren't noticing other other issues even lower than that, could be limitations of the tone generator/mic setup you're using?

[emack27]

These Seas designs have be around for years, I think.

Yep. As you can read from the blueprints dated 2/2001 these speakers are ancient.

[emack27]

The problem at 100-120 Hz is almost certainly room induced to some extent (the design itself should be fine, even if the cabinets have an issue, that would show up much lower in frequency) I'm surprised you aren't noticing other other issues even lower than that, could be limitations of the tone generator/mic setup you're using?

Well, I'm using a tone generator downloaded off the internet and using the latest and greatest NVIDIA soundcard. From there the signal goes out through a small headphone type jack which converts to RCA type stereo plugs then goes into my CD input on my Denon Receiver. The mic I'm using are my ears. I don't need a SPL meter cause it is that abvious.
I don't think there is a problem with the signal im getting, but who knows?
The only way I could tell if it's my room acoustics is to take it outside and test them there. I guess.

[emack27]

If it was a standing wave produced by room acoustics. Wouldn't the standing wave dissapear by either simply moving me or the speakers to different locations in the room?

[jocko_nc]

These are on my "to do" list. I have to buy some more woodworking tools soon to do some projects around the house, some bookshelves and built-ins. Added to the cost of the house, the purchase will be miniscule. That should come in handy for building more complex cabinets. I cannot wait.

Jocko

[kexodusc]

If it was a standing wave produced by room acoustics. Wouldn't the standing wave dissapear by either simply moving me or the speakers to different locations in the room?

Not necessarily...it would probably get shifted or altered somewhat in width and intensity but it could still remain in that rough area. I'm guessing it's not a fundamental at 100Hz but an upper resonance.
Try a completely different room with much different dimensions...or better, outdoors to see if you get the same thing.
And be certain your measurment gear isn't innaccurate. My microphone for example is rather unreliable below 200 Hz, so I wouldn't dare use it for measuring speakers.

In the end it could be a problem with a woofer or something, and not room induced, but it's nice to rule out everything first.

[emack27]

Whew!
I was getting scared that my speakers were missing the ability to reproduce frequencies between 100 and 120Hz.
I simply moved my speaker to the middle of the room, layed it sideways on a milk carton and then ran the tone generator. The speaker had virtually no db drop at 100 to 120Hz however there were other noticable peaks and valleys within 20 to 20k hz range.
My problem is definitely room acoustics which is good cause I'm moving out of my apartment and into a house which has alot more sq. ft. in the living room. I think that the problem is sidewall reflection or small roominess phenomenon syndrome.
These speakers were not meant to be listened to in small rooms. They need room to breath. For small rooms I recommend bookshelf speakers.