'Perceive' Contruction Diary

[ShinOBIWAN]

Just to illustate the quality of the ATC dome mid:




The ATC certainly offers more material value than the Scan ring. Also note the irregular rear on the Scan, most likely to minimise reflections passed into the rear of the cabinet. Nice touch.

This thing weighs in at 9kg, more than most so called subs

[ScottG]

The excel driver isn't the natural choice here, rather this new seas driver is (understanding that power input will need to be increased to achieve flat bsc response):

http://www.seas.no/seas_line/woofers/H1252.pdf

Only two things bother me with HiFi woofers: dynamics and distortion nearing fs. Provided you have the skills I'd be more inclined to mass load the Beyma 8G40 (but the result would be even less efficient) vs. the Seas driver - but the easier choice is still the Seas (and it will provide much greater spl).

The ONLY 8 inch driver I can think of that has enough eff. (even with a bit of mass loading to lower fs) is more expensive and probably has worse distortion nearing fs (though superior dynamic capability and far more "transparent" upper bass and lower midrange):

http://www.supravox.fr/haut_parleurs/215_GMF.htm

It would be my first choice (a pair with a bit of added mass), though costly. (note the csd at 300 Hz, there is about 9db of clean signal, almost like a Manger driver this low in freq..)

[ShinOBIWAN]

Its funny you should mention the Sea's L22, it was in my mind as a potential condidate.

Here's the short list so far that look suitable:

Sea's L22RXP
Sea's Excel W22
Volt B220.2
Volt B250.8
Scan-Speak 22W

The supravox are very difficult(second hand market only) to get hold of here in the UK and I would never consider shipping another speaker from a different country ever again after the hassle I've had previously.

[ShinOBIWAN]

My aim isn't floor pounding bass like some would pursue.

I want these to be about imaging, detail, speed and transparency.

I don't think I could have made a better choice regarding treble and mid units, they're the best that's available in the UK. The bass driver however is always more trouble.

I can boost the low end of bass drivers using a linkwitz transform circuit or maybe that's a little too drastic and could further increase distortion.

[ShinOBIWAN]

What about the Eton 8-800/37 Hexacone?

Never tried one of these but would be interested to hear others thoughts.

[jleaman]

Thats a nice nice Tweeter you will have to forsure to post pictures of the box's when they are done.

[JohnL]

Have you looked at the Audio Technology flex units, they are expensive, but you seem to have a good budget. Other than that, the Scan 22w would be a better choice that the Seas W22.

I have used Eton drivers, and they sound nice, but I don't think they would be a good fit for this system.

[ScottG]

Originally posted by ShinOBIWAN
My aim isn't floor pounding bass like some would pursue.

I want these to be about imaging, detail, speed and transparency.

Hmm, to bad then about the Supravox - that would be their forte (and better dynamics to "boot").

The 8/800 37Hex looks pretty good. (a little higher Qts is a good thing for the T-Line, though fs isn't quite as low as the Seas). I'm guessing though that the driver will be a little dynamically "stunted" (as would the Seas). Excursion isn't much - so spl's would suffer. At least they publish distortion figures - it sure would be nice to see what the distortion was like on the Seas. Between the two I'd opt for the Seas (which is virutually tailored for a T-Line).

The Volt drivers don't do anything for me - nothing special on the TS param.s and no distortion figures (and the smaller one doesn't have the "Q" neccesary for a T-Line).

As for the Scan Speak, the Q is a little low BUT the response seems to "take up the slack". Like the Seas you are missing data on distortion, but this is Scan Speak.. Excursion is lower than the Seas while MMs is higher. Again, between the two I'd opt for the Seas.

[ShinOBIWAN]

Hello again folks.

I've had quite a drastic turnaround regarding the loading in the bass cabinet. Originally I had planned a TL loading but after modelling using MJK's excellent MathCAD sheets I'm now having second thoughts.

My proposal is for a sealed box design both heavily braced and stuffed. Then apply a Linkwitz transform to lower the response.

This of course means a totally different look at potential drivers used for the sub enclosure.

Right here are the requirements for the driver:

-Driver must be flat to at least 500hz+ as it will be crossed over at around 400hz.

-The lower the Fs the better.

-The higher the efficiency the better - less power required.

-The higher the excursion the better - less distortion

-Enclosure volume is likely to be 70 liters.

I would really appreciate any suggests on the types of driver(s) to be used. I'm also going to consider drivers upto 10" instead of the 8" previously.

Once I've got this bass situation sorted I can start work.

[tiroth]

I'm curious about how the plan to use LT interacts with the statement that "floor pounding bass" isn't needed. How low do you want? In my experience, F3 around 50 can be quite authoritative in a sealed alignment. The advantage being, there are a lot more drivers to choose from in the Fs ~40 range that will deliver this performance at high efficiency. Also, I think it limits excursion and thus distortion.

I hope you don't object to me picking your brain as you work through this process; it's of particular interest to me as I am also working on a TMWW design that seems to stem from similar design principles: high efficiency, a wideband true mid, coherent woofers, all active. I've already got the basic design done but I am still playing with the XO...I'm interested in 4th order because of the phase alignment benefits, but since I have a good-sounding 2nd-order XO, I'm afraid of the supposed sonic penalties of higher-order designs.