MCM 8" 55-2421 Isobaric

[tb46]

Hi fastbike1,

The 55-2421 models just about the same as the TB W8-740P in the THSPUD tapped horn, as seen in geitmans thread: Dual 8" tapped horn = TH-SPUD.

Just in general, the 55-2421 seems to work best in FLHs or THs.

Regards,

[tb46]

Hi Odougbo,

Have you seen the CSS Quartet10 Subwoofer Kit?

Creative Sound - Product Details

Regards,

[ODougbo]

Originally Posted by Don Hills

Doug,
I'm an isobaric fan myself, which is why I read this thread, but after doing the sums I can see the logic behind Sreten's recommendation of a standard layout 2 driver setup.

Regarding port size, you said your port is 10 inches wide and about 3/4 inch high. No way is that 100 square inches. A square port (10 inches by 10 inches) would be 100 square inches...

Regarding the CSS driver versus 2x MCM, see the attached graph.
It shows isobaric MCM 55-2421 versus single CSS Trio8 in a 30 litre enclosure tuned to 30 Hz. The MCM drivers are fed a total of 240 watts, and the CSS driver is fed 200 watts. (Ignore the "modified response" caption, the spreadsheet I used allows applying filters and adjusting for measured room response etc.)

Thanks Don, very helpful. I like the sound of 8" and Isobaric, and may try this woofer, don't think I could fit 2 in an Iso box though.

If I went this route, I'd buy two and have a 30 liter box on each side.

[ODougbo]

Originally Posted by tb46

Hi Odougbo,

Have you seen the CSS Quartet10 Subwoofer Kit?

Creative Sound - Product Details

Regards,

Thanks, I did see that a while ago. I just got off the phone with Meniscus, unfortunately the teck fellow wasn't there. I had a few questions about the SDX10.

http://meniscusaudio.com/css-sdx10-p-773.html

I tried some aliments in WinISD and Perfect box, they were about the same: a 2.25 cf (64L) box tuned at 25hz gave some impressive results; -2.8db @ 27.8hz
Sounds too easy...can someone check please, or recommend a box size?

The suggested box size is 43 liters, net. 3” flared port, 17” long for 24.5 tuning.

Imp - 4 ohm
Fs - 26 Hz
Qts - .42
Vas - 53L
SPL - 85 dB
Xmax - 18.5mm

BTW, Don the Trio 8" won’t be in till January.

[tb46]

Hi ODougbo,

That sounds right, I end up with a 4 cm longer duct for 24.5 Hz in Hornresp, so about the same (SDX10; Vrc(net): 43 L; duct area: 45.6 cm^2; length: 47.4 cm).

Regards,

[revboden]

Originally Posted by ODougbo

Sounds too easy...can someone check please, or recommend a box size?

LOL! You've been chopping down trees with a duck... now that you have an ax it's too easy...hahahahaha

about the box: that's about right.

[ODougbo]

Originally Posted by Don Hills

They would be more useful there, where the woofer does mid duties as well.

Looking at your design, the biggest problem I see, apart from the ones that other people have already pointed out, is that your slot port is too small and has very high losses. You can see that from the relative size of the 20Hz and 40Hz resonant peaks. If your port was more efficient, the speaker would have a lower excursion for the same output at resonance. The port ought to be 2 to 3 times as large (cross section) as it is now, and of course a lot longer if you want to keep the 30 Hz tuning point. It then gets hard to fit a port that long into the enclosure. Do consider it though, because the results are desirable - lower distortion because the drivers don't exceed xmax at high power, and less port noise ("chuffing").

I wouldn't build these enclosures for myself. They are simply too large and tuned too low for the drivers to give of their best. Your description of their performance (in post #73) shows that. The problem is, there doesn't appear to be any way the drivers are suitable for sub-bass use. They would make a good woofer, or maybe in a bandpass enclosure as suggested by Michael.

I note that a single CSS Trio8 would be a better match to your enclosure, and would provide about the same output for the same power and a similar price (1 Trio8 vs 2 55-2421, assuming both at full retail price.)

Thanks Don, a very good lead, I'm going to request to be added to waiting list.

I ran it two programs, it will go a bit lower in a 36l - 42l without too much of a dip, and get past the 30hz line, there would be a 1 db hump at 35hz.

They wouldn’t give me a $$ quote over the phone for the new TRIO 8”, but I think the price is going to be up there.

http://meniscusaudio.com/images/CSS%20TRIO8.pdf

[Don Hills]

Good luck... it's all academic to me, such drivers are "too rich for my blood" - too expensive down here at the bottom of the world. I have to make do with drivers "liberated" from thrift-shop finds etc.

[ODougbo]

Maybe I should have started off this thread with “best subwoofer for around $100”

[2 woofers delivered - $76]

I hooked the signal generator to the processor, did not move the speakers out of the room.
They sound like the modeling on post #97, there is a slight dip before the 30-35hz peak, I don’t think dip is that bad; also there are ways to compensate, yes? I don’t find the need too, I just run them flat – crossed over at 80hz.

I’m pretty sure the 30 – 35hz peak is above the flat line. I am always impressed with the “power” - they just have a powerful feel to them.

Also, unsure why a classic tuning method – is now a false impedance reading.

I may be stirring the pot again, never, never my intention; the target was more of what can be done for less.

Brief history, My Grandfather used to send me 12” die cast Electro voice woofers back in the early 70s, I’ve been “building speakers” since then; cars, trucks, houses; out of wood, PCV, on and on.

[ODougbo]

All most forgot about this build; similar to the last. Started off with 2 - 10s, Foster drivers (If I have the name right).

They were both side by side in a 6cf sealed box, used them for years; the box configuration was recommended by the seller. Then about 5 years ago contacted the seller (starts with an M); they said no, no, no, build a 4 cf vented box and run them parallel since they were 12 ohm woofers. They even sent a plan; fine it worked great, much better than the sealed.

From that point, I got the idea to go 2cf isobaric (tunnel), well that was the best sub woofer out of all three. We are still using it in my dad's HT, it is very "powerful". Sure got my $$ out of these woofers!

So that said, I have one more plan/build up my sleeve AND this new Iso box models nicely in WinISD. more to come.

I'll be back……….