Which 6.5" mid-bass for a sealed box?

well but break-ups due to the material, why you worry about - 3dB at 50° / 2 k hz where a tweeter will work from there ?

Yes it doesn't sound the same than paper. Anyway here the real gem is the AL-130 but it asks 3 ways. (or a sub that climbs withh ligthness)

But that futilities for the talk. The road map needed by Andy was talked and ranked by members about the important issues first.

Edit : it is not easy when your road map is limited : 20 l, 2 ways, amp power, not front wall bass renforcement, budget, design choice about the load.

I live with a Chord amp, so I have not power limitation problems, it can drive difficul impedance loads with knee breaks in the lows w/o sweating.

Turnowatch analysed it the rigth way imho relative to the amp and problem was talked in the first page of this thread.

Well maybe if Nelson Papa was chimming here, he told us 4 W of SET power amp spites more current than SS. But bass needs watts to be happy (transcients, control of the cone)

Perhaps the clever guys choose a SET for the mids and highs and a dsp class D plate amps for the bass, who knows (that's I would do but as I am not clever and knowledged enough it is maybe a bad advice. But anyway is on the table as an option for the discuss)
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Here is a 2 way design using Visaton 6.5” speakers. There are two in this tower design, the one at the top has a 16 litre sealed box, and the bottom unit is ported to give additional bass extension.

My suggestion here is to get your local kitchen cabinet company to cut the wood and the holes and make the rest yourself.

You will save on stands unless you already have them, but you may be able to offload those. The floor area will be similar to a standmount.

Make that your main system and build some small speakers for the kitchen using your aluminium.

I think those will go loud enough for a small living room in an apartment on 3 watts without annoying the neighbours.

Step back. Have a think. Decide on the priority of your wishes and then accept the inevitable compromises that ensue knowing that what you end up with is the best possible speaker given your constraints 😀

I did that with mine and it worked out well for me. I doubt anyone else anywhere would end up with a design like mine.
Does the amp accept 4 Ohm?
The SC10N sure has a reputation though. But there are bazillions of good designs out there. I think we could narrow down the options. The OP wanted a closed box with modest dimensions, about 20l. I guess budget is about £300-400. There is some wish to use aluminium panels for construction. That would exclude complex enclosure shapes. Closed design, wise decision for a 2-way. Who shoots first?
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Maybe if Andy would post exact plans for his cabinet, someone could design a matching kit? So far there has been no real hit in the kit lottery.
If I would take this serious, the Tymphany BC25SC06-04 for a tweeter is a nice candidate. High SPL, wave guide makes things easyer with position on baffle and flat impedance for simple x-over construction.
The woofer is more complicated to find, more than 6", light cone and suited for a closed volume with high efficiency.
I just measure 4 pices W170S-4. None was even near the published TSP and only two could be called "a matching pair".
There should be something better. Offers?
what is the plus of alimunium in a small cabinet? Aluminium has poor damping for this task and stifness is not a problem with most woods and 20 liters little cabinet and do have damping.

The only advantage is a littlier cabinet cause aluminium is less thick at iso stifness than Mdf for instance.But 20 liters is so small you hardly notice it imo.

So if the budget is important but special plan to have cheap machined aluminium, I would cope with natural fiber and CLD or box in box with cheaper 2 thin layer of a different wood made pannel with visco elastic glue in between.

I would put the monney where it is important : passive parts and drivers. a Visaton or Monacor 150 mm WG is an option too. The sb26 cac will certainly meet many 6" or 8" after the baffle step efficienty loss.

I would finally cut the apple in two anch choose aperiodic if needed if the low end has to looks like a sealed. 6 db slope difference 12 vs 18 iirc. But a good driver suited for a SBB4 is near 18 dB slope also, no ?

But I stay on the idea to dev something for 70 hz something f3 for a future +1 way little closed sub with dsp plate amp that will rule the first half octave.

This option opens the choice on many more midwoofers.
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Maybe if Andy would post exact plans for his cabinet, someone could design a matching kit? So far there has been no real hit in the kit lottery.
If I would take this serious, the Tymphany BC25SC06-04 for a tweeter is a nice candidate. High SPL, wave guide makes things easyer with position on baffle and flat impedance for simple x-over construction. The woofer is more complicated to find, more than 6", light cone and suited for a closed volume with high efficiency.
Thanks! I'll post exact plans for the cabinet ASAP. By "kit" you mean the tweeters, woofers and crossover design? I can source the inductors and capacitors. I have quite a lot of each.

Where does the crossover come from with the Tymphany BC25SC06-04? I need a crossover design for whatever units I use. For example, the Peerless P830667 looks good, F3 48Hz in 30 litres sealed. But where does the crossover come from?
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Andy, have you a pdf review somewhere of theactual loudspeaker you have, please ? It could help the people to know more with the bass you are confortable with. What are the woofers models ? How far the speakers are from the front windows, spacing and chair distance ?

The tweeter is not a problem, plenty of candidate, let focus as said TurboW2 on the midwoofer choice.
too bad the the Faital Fe330 has 52g cone because in 28 L sealed this 10" has f3 64 hz, f6 49 hz , f10 38 hz ! Looks like bad numbers but it's a 10" (size matters would say some) with 92 db/2.8V. Put the Cat378 in top of that and you have an Orangoutan Devore like ! impedance is 5.2 R and Fb 65 hz. Fs raw is 35 hz :)
With a 12db low pass, f3
with a cut-off around 2 K hz it is a 1.2 WL c2c spacing with the cat378 with 1 cm of wood (or aluminium) between the 2 drivers !

Can take the size of the orangoutan loudspeaker and just play in the deep to reach 28 L !

Should be a fun speaker ! a little like that : https://www.diyaudio.com/community/threads/devore-orangutan-clone.272810/post-7325925

well off topic, sorry ! Let's cope to the road map with 6" or 8". But the Makako looks awesome !
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Andy, we first need to find the two driver that can work for you. This includes simulating the midwoofer in the cabinet. Then it is time to start simulating the crossover. Some can do this until the last fraction of an Ohm. Then you can put together a working speaker. If the simulation was right, even a fairly good one.

I'm very much "old school". I pick my chassis from any information I can get. On the actual part I measure TSP, then simulate a cabinet and build it. Next I measure each drivers response. Now I simulate a coarse crossover and tweak it during measurments. As soon as this seems to go into the right direction, I do listening and repeated measuring, fine tuning until I'm satisfied. Sometimes a chassis combinationdoesn't work for me, that is part of the game, no catastrophe. These chassis will sure be used on another occasion, sometimes even years later. Good chassis don't really age. There is no real new stuff comming, even if marketing tells you so.

See, I build my first speaker about 45 years ago. I bought my first real measuring system in 1989. I have a technical background of mechanics, electronics and thermodynamics. I see a kind of system in most things I see. This gives me a kind of gut feeling, or call it educated guessing, in anything technical I do. Something you can not transfer to others. Not over the internet.
I see my self using more simulation each year, simply because they are constantly getting better, can be used on a computer without real physical parts and save time and money. Even the free stuff is so fantastic today, we could not even dream of 15 years ago. Sure, computers got fast, that helped.
Anyway, I'm no professional developer and do speakers 95% just for a hobby. There are others that are much better and faster in the simulating game than me. You find them here, but they must be motivated and need resonable data to process.
And remeber, this is DIYS, so in the end you have to decide, build, listen and are responsible for the result.

Please keep another thing in mind: DIYS with cheap, low quality chassis makes no sense. Your home made cabinet will make no mediocre set of chassis and crossover a high end miracle. In building anything cheap, the industry is a million times better than you. So if you plan to spend less than 200$, better look at eBay. You get good used and even new speakers for very little money, if you shop smart.
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Agreed with Turbowatch2 in most. Budget wise, I see no sense in using very expensive drivers if you don't follow a kit design and don't have the means to develop the speaker yourself. The differences between a regular SB 7" and Satori or Scan Speak Discovery vs. Illuminator/Revelator equivalent sure are there, but only will shine when the rest of the design is more than quite excellent. You have to put your attention to the weakest link.

I'd say either build a proven kit to the exact copy or spend a little less and divert to your own design. Midwoofers like the SB17NRX, the Seas U18RNX/P and many others perform excellently and are relatively easy to fit in a crossover. The same for tweeters like the Scan Speak D2604 or the SEAS DXT (which actually is a perfect match to a 6-7" woofer). I remember a very good design from Mark K, the ERDXT. Could fit the bill too, I'll look it up.

[Edit] found the web page print. His site is down since long, sadly.


  • Mark K ER18DXT.pdf
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On IEC baffles...
View attachment 1235846
This is the response of a RS180S (at least the part under 1,5k, in 10 deg steps) in a real life box, some 8,5" wide. Now this is a 7", what do we think an 8" would do at 700Hz?
Interesting - but also suggestive of needing a very small driver under all circumstances if you care about the lower plots.
It would be interesting to see what a tweeter does as well.
Is it my imagination or is there 11 plots?
It looks to me that 60 degrees is the red plot And it seems down a fairly constant amount between 1k and 3k. I can only assume edge diffraction effects?
It actually is the plot of a two way comprised of the RS180 old shielded version and a SB26ST in the WG300 waveguide in a small monitor speaker. You see all kinds of diffraction effects, notwithstanding the waveguide. Larger baffles likely show less, but I wanted a simple rectangular baffle just around the units.

I see 11 plot lines too, should have been 10. I think I added a 45 deg measurement, but I would have to look it up.
Here's the box dimensions.


MyAluBox dims.png
Sorry, got that wrong somehow. Anyway, not the "usual" baffle shape.

6.5mm extruded aluminum is quite silent in such short cut's. A coat of semi elastic material like SIKAFLEX should make it sound dead. You could use a reasonable coat SIKA and top it with some alu-butyl. This works perfect for damping and will stick to the aluminum (eloxal?) for ever.
Don't waste too much volume, money and time on damping. This is no wizzard art work, even as some treat it like that. Dead is dead, you can not win anything with double or tripple kill.
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@markbakk funny you posted the Seas U18RNX / Seas DXT combintion. I just wanted to post the same drivers, just done by a guy doing much more complicated x-over designs and selling the plans. Something not really my first choice, as I prefer using not too much passive parts.
Anyway, you find some well reputated plans on his site.
I second your opinion about the crossover but you need to keep in mind that this project was done to challenge the Neumann monitor speakers KH 150 so maximum linearity as a passive speaker was the goal. From this POV it's a great result, but only if you want to have something close to the Neumann's. Else I would also prefer something more pleasing than max clinical accurate. I heard them once, they are really good but kind of lifeless, not my cup of tea.
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For example, the Peerless P830667 looks good, F3 48Hz in 30 litres sealed. But where does the crossover come from?
The spl curves for that one look unsuitable for your use to me. All over the place past 1kHz and that would need heavily suppressing to get a decent phase /spl match with the 2nd speaker. Fine for a sub that might crossover at less than 2OOHz. There are lots of 8" units like that Othrwise 3way or maybe cross over to a full range speaker.