Active studio monitors

Yoda

Member
2001-07-30 1:35 am
I am interested in building a set of active studio monitors with the alesis amps at apexjr. these have a 68w and 40w amp along with an 8th order 1.6khz active crossover. at $5 a piece, you cant beat it. ok, so i've got an amp, but what drivers to use? i want to stick with the original 1600hz crossover, so the tweeter needs to be able to extend pretty low. I am thinking of using the morel MDT-20, with an Fs of 650hz and a price tag of just $25, i'm sold. my biggest problem is what woofer to use, any suggestions? i was thinking of using an 8" because more bass would be appreciated and it doesn't have to extend too high (with a 48db/octave crossover that is). a main design goal of this speaker is to have quick transients, will a cheap 8" fullfill this, or should i use a 6.5" instead. I realize that more costly drivers will make it sound better, but i'm on a budget.
BTW, by cheap i mean $50/driver
 

argo

Member
2001-02-12 3:35 pm
Estonia
Given your price and driver size requirements I would suggest Seas CA21REX. It is well-proven 8” woofer, has paper cone (considered to be more musical and accurate cone material than polyprop for example), relatively high sensitivity - 93dB (you need it for baffle step correction) and has good high frequency extension.
Crossing it at 1600 Hz with 4th order LR (24dB/octave) filter should yield promising results. I would personally get rid of that 48-dB/octave x-over. I think that can be done easily by removing couple of sections of cascaded filters.
As for tweeters MDT 20 sounds OK but you can consider also Seas 25TAC/G aluminium dome as an alternative.


Argo
 

Yoda

Member
2001-07-30 1:35 am
i don't like the seas' response graphs, it rises continually throughout the range i'm lookin at (<1600hz). What about the AUDAX HP210G0 8" COATED PAPER CONE POLYMER WOOFER ? it is cheaper, which is always a good thing, but i'm afraid that an 8" woofer will have horrible midrange qualities? will a sealed box help?
 

argo

Member
2001-02-12 3:35 pm
Estonia
Yoda

About Seas CA21REX. I recommended that specific driver because you looked specifically for 8” driver and there are not so many 8 inchers around that could give you similar results as this woofer. This particular driver was used in Seas Njord kit and the resulting product gave really spectacular overall sound and delicate midrange for such combo. A negative thing if you were considering them for studio application would be the box size of that combo - 40 liters for studio monitor is a little too much I guess. Of course you can go with closed box but then again you don’t have that extra bass you were looking after.
Closed box will not give you a better midrange but tighter and more natural bass and midbass because of better transient response of 12dB/octave bass cutoff slope of closed box.
I have seen some more two - way monitors where 8" was used with good success. One of them used also Seas driver but it was custom made P21REX and was twice as expensive than its cousins. This particular speaker put many monitors with 5 and 6,5 incher to shame.
What I want to say is, that it’s not totally impossible to design two-way monitor with 8” driver and achieve good midrange but you will be quite limited with the choice of drivers. Also there are many 5 or 6,5” drivers that can give you inferior results.
And finally, of course with 6,5" drivers you have lot more freedom to choose between suitable drivers in your design and you don’t need necessarily loose in bass response if you choose your drivers and box alignment carefully.

Good luck

Argo
 
Not to rain on your parade, but I would be rather careful with those modules. They're not exactly the highest quality and have some nasty features, like a woofer output that's 6dB higher then the tweeter, and I think a high-pass on the woofer output.

You can't beat them at that price, but you might notice audibly why they've got that price.