6,5" to 7" midwoofer for sealed enclosure

[martinbls]

Most available drivers in the 6,5" to 7" range have ts-parameters optimized for the use in vented enclosures. Somehow I think for a really nice sounding low frequency range sealed enclosures might (theoretically) be better!

There is the low-efficiency-problem with such a design, though.

That's why I would like to construct a 2,5 way with 6,5" drivers that work really good in sealed enclosures around 20 l. Until now, I wasn't able to find such a driver. Btw., it has to be good in the midrange, too! A smooth response that allows simple crossovers is what I'm looking for.

Any suggestions or experiences?
Thanks a lot!

[alspe]

Driver for closed box should have low Fs (if low bass is needed) and quite high Qts (0,4-0,5). Seas CA18RLY/U18RNX/P might be choice from Seas.

If you are using 2.5-way, you can think of lower Qts (stronger motor, smaller box) and compensate decending bass response with 0,5 driver.

20 liters is too small for 2,5-way (2x6,5"), though depending of driver used.

[martinbls]

Thanks for your reply!

I also had the Seas CA18RLY in mind but I was unsure about its light and thin paper cone. In my experience, those cones do not produce that much "punch" in the low frequency range.

With a volume of around 20l I meant for each driver.

Another driver I found that is supposed to work quite well in sealed enclosures is the Monacor SPH-170. A very versatile driver with a smooth frequency response and a f3 of 60Hz in 25l sealed. But certainly a bit less "high end" than the Seas drivers, even though the Monacors aren't cheap at all.

[jerome69]

This chinese driver W6-1721 ?. I own it little brother W5-1685, a low distortion driver. I would like it more lively but it is my taste.
http://www.tb-speaker.com/detail/1230_04/w6-1721.htm (17L)

If you can ? An other world class but the crossover is not simple.

THE ART OF SOUND PERFECTION BY SEAS - E0018-08S W18E001 (17L for one)

THE ART OF SOUND PERFECTION BY SEAS - E0051-04/06 C16N001/F (15L) See the application note.

The best f3=50Hz, the price too is high.
18W/8531G00 (20L) Scan-Speak

Most of drivers are optimized for BR but some of them could be used in the two configurations.
Note I think you can have good results with an optimized BR. I don't like BR a lot but with the new drivers like SEAS ER18RNX, W18RNX, the bass is very good, tight, no slow down.

2x17cm ~ 20cm ? less expensive. e.g.
THE ART OF SOUND PERFECTION BY SEAS - H1288-08 CA22RNX ?
Note the CA22RNY in a BR box can give you 90dB : http://www.seas.no/index.php?option=...173&Itemid=165

[crazyhub]

Why searching for drivers able to be "enclosed" since you can have the best of both worlds with drivers made for vented enclosures? Please read this:
Sealed_v_Vented
Moreover: I often tune my vented systems by adding acoustat stuff inside the box; however this trick needs impedance measurements to be sure where we are going.

[martinbls]

Hi Jerome!

Well, about some of your (much appreciated!) ideas:

I'm not that fond of those very high-end Seas drivers with magnesium cones etc. I'm of the oppinion that too much "high end" leads to a very accurate but somehow artificial sound, especially with some older, partially badly recorded rock music from the 70's. I'm really into this kind of music. You know, the old Genesis, Led Zeppelin/Robert Plant, Sweet Smoke, Focus, Nektar to name just a few. For this kind of music it's neccessary that a speaker is a bit more forgiving about the source signal :-)

The Scan Speak may be one the best solutions by all means, but it's simply way out of my price range. Let's not even talk about TWO of these drivers per side...

Regarding the Seas ER18RNX I already read Mark K's page about the ER18DXT. While I would love to build this one, I don't really like the idea of a baffle step compensated driver. That's why I thought about the 2,5 way approach. But, nevertheless, Mark's design would make a nice starting point for a modified version: The ER18DXT with an additional woofer for BSC!

With the Seas H1288 you gave me an idea: Why not using two 8-inchers per side, say, 30l sealed cabinet individually for each driver, 2,5 way to fill up the baffle step loss and add a horn loaded tweeter or a waveguide? I HAVE to think about that for a while. The Seas H1288 seems to be a proper chioce for this allignment, despite the peak around 3kHz. (Perhaps a notch filter would help?)
The H1471 seems to have a better roll off but it's more suited to a ported enclosure I'd guess.


Crazyhub:
Nice article! It seems I have to try out more different vented designs, e.g. alter the tuning frequency to see what happens soundwise. Thanks for the link!

[planet10]

SDX7 works well in a sealed enclosure. It thou has a smooth roll-off at 1.1 kHz (with the mod-podge mod), so won'y reach up high enuff for a typical 2-way.

dave

[jerome69]

Martin,

The classic seas paper is very forgiving

I used the ER18RNX, a very nice driver, in a MTM not a 2.5, 30L@43Hz, 91dB/2.83V. I was impressed by the very tight bass. The tweeter is the monacor DT300+WG http://i23.servimg.com/u/f23/11/13/40/71/img_0110.jpg

I also know the CA22RNX, H1288, in a 2.5, 91dB/2.83V. The 3KHz peak can be suppress with a notch filter. The crossover could be simple LR2 2.2KHz. A tweeter with 90-91dB could do the trick.
You can go to a 3.5 or 3 ways, add a 5" midrange, The MCA 15 ? You will have a big speaker
Projet ASTASIA I -Seas CA22RNX + MCA15RCY + Vifa XT25TG30 - Enceintes
Poor Man'
3-Way Classic

Let us know your final choice

[martinbls]

Originally Posted by planet10

SDX7 works well in a sealed enclosure. It thou has a smooth roll-off at 1.1 kHz (with the mod-podge mod), so won'y reach up high enuff for a typical 2-way.

dave

Hey Dave,

now this is an interesting driver!
Did you listen to it fullrange? How is the midrange from these, and how does this nasty behaviour in the range from 600 to 1200Hz sound? Too bad there is no waterfall diagram shown in the datasheet.
Perhaps this one would be nice combined with the CSS EL70PLUSERT26 fullrange plus tweeter-kit?

[planet10]

I've not used it higher than ~400 Hz (1st order). In this kind of ap it is superb. Add a good midtweeter (ie FF85, A6P) and you have a really good 2-way.

The mod-podge mod mostly eliminates the ugliness from 600 up, and also increases DDR.

red is modded driver, yellow stock.

dave