The Pentaview - or the results from my latest inspiration

[454Casull]

Check it out, let me know what you think. Still a design concept, no actual work done.

I still think the enclosure is kind of ugly. Oh well. What will make it worse is that I want to use felt all around the upper 4 drivers.

Couple of things to note: the baffle is shared, but the inner air space is not. Uh, also, I won't be able to really select the proper crossover point between the sub and the lower mid until I measure the drivers in-baffle.

[boris81]

It looks alright so far. I think that you might be able to meet the requirements with a 4-way design. Also I think that separate subwoofers can give you more flexibility with room placement especially if you can time-delay them with DSP.

[454Casull]

Originally Posted by boris81

It looks alright so far. I think that you might be able to meet the requirements with a 4-way design. Also I think that separate subwoofers can give you more flexibility with room placement especially if you can time-delay them with DSP.

Would you suggest taking out a driver or replacing two of them with a different one?

Going 4-way is a definite possibility but I couldn't really see how without running into either beaming (even however slight) or high center-to-center spacing.

[454Casull]

Something came up that is being rather irksome. I now want to attenuate the effect of floor bounce, and at my listening position, the dip is centered around 290 Hz. Unfortunately, with the crossover at 250 Hz, the cone mid is definitely going to effect the dip.

Now, the easy solution is to push the woofer up as high as possible, but center-to-center gets quite high (up to 3/4 wl). I suppose I could drop the crossover point a little, say to 350-400 Hz, and compensate with the proximity to the dip with an ~8th-order elliptic filter, Jon Marsh/Bob Ellis-style, but still...

Ideas?

[boris81]

There are a few options to explore but I would start with trying to eliminate the 1" tweeter. I've had success with crossing over the Vifa NE19VTA-04 very low and Zaph's measurements suggest it's good to about 2kHz. I also cut out the flange to get better center-to-center spacing (it's aluminum). I don't do 110dB so you should run some experiments to see how it holds up.
If you are willing to spend the money (you save some by eliminating a driver) the ScanSpeak D2004/6020 looks great.

[454Casull]

Originally Posted by boris81

There are a few options to explore but I would start with trying to eliminate the 1" tweeter. I've had success with crossing over the Vifa NE19VTA-04 very low and Zaph's measurements suggest it's good to about 2kHz. I also cut out the flange to get better center-to-center spacing (it's aluminum). I don't do 110dB so you should run some experiments to see how it holds up.
If you are willing to spend the money (you save some by eliminating a driver) the ScanSpeak D2004/6020 looks great.

Unfortunately the NE19VTA doesn't measure quite as well as the Aura or the DQ25SC16, and at this point I would have no way of knowing whether the difference is audible. I really do not want to cut more than one baffle.

Any clues about the floor bounce?

[454Casull]

Oh, the OX20SC00-04 looks really good for this application. Damn, looks like I might have to rename this project.

[454Casull]

Still looks like the Aura is the better tweeter for now. If I run it straight to the RS52, I can get better than 1/2 wavelength spacing, but at the 2 kHz required to avoid the beaming of the 2" dome, I can only get 105 dB half-space out of the tweeter, assuming 0.6mm p-p Xmax and not 0.6mm one-way.

Three things help: 1) my calcs tell me "average" music will need only about 103 dB, with excursion weighted around the high-pass but sparingly distributed, 2) a 4th-order LR will give me a -3 dB dip at the high-pass. Still, pushing it a little bit, and 3) HD tends to be harder to hear in a tweeter since 3/4/5th-order is so high up in frequency.

[454Casull]

Couple of changes... it looks better, at least.

Too tired to put up the worksheet, but a few notes now:

- drivers are Aura NT1-204-8D, Dayton RS52AN-8, SB17NRX35C-4, 2x Dayton RSS265HO-4
- obviously, the RS52 was modeled without the flange cutout for the dome tweeter
- the brace in the middle is solid and helps keep the two bass drivers from affecting the cone mid
- the lower air space is a ~1.3 cubic foot vented enclosure, tuned to 30 Hz. F3 is at approx 35 Hz.
- outer dimensions are 320 mm x 320 mm x 1000 mm

[adason]

hi 454Casull, I would recommend this tweeter:
Dayton Audio ND16FA-6 5/8" Neodymium Dome Tweeter 275-025
its inexpensive, it sounds great, its small, it complements dome's sound character well, and it has been used succesfully with dayton dome
I have used it few times, and zaph has 3.5 design with it as well, so you can get some info on the crossover...