Thanks morbo, I am indeed at an early stage in fixing on this design. I'm starting with the interaction between my planned box and the mid-bass which looks like the place to start. I am well aware that a "kit" includes the enclosure design but in this case I will have to proceed on the premise that the crossover design I use won't be too far away from my proposed enclosure, just a different shape. This may well affect the baffle interaction, but I'll just have to make it as close as possible. The height and depth of the enclosure are already determined by the aluminium core I have, i.e around 300mm high and 250mm deep ID. I could vary the width for the final build if this was desirable. I haven't fixed on a width yet, except to shoot for 20 litres, but this is flexible. Here's a picture of the aluminium core I have, showing one side. The other side is identical. I wanted thick aluminium for rigidity. It will, of course be well damped.
The other point is that the vast majority of kits are ported ones, and I want a sealed box so that requires a bit of lateral thinking. Two of the designs I'm looking at are the Troels G. CA18RLY one and the SEAS Mimir, since they have the right kind of mid-bass for a sealed box.
http://www.troelsgravesen.dk/SEAS_CA18RLY-COMPACT.htm
https://www.seas.no/index.php?optio...d=381:mimir-seas-diy-kits&catid=66&Itemid=345
https://www.seas.no/images/stories/diykits/pdfdataheet/mimir_plans.pdf
The other point is that the vast majority of kits are ported ones, and I want a sealed box so that requires a bit of lateral thinking. Two of the designs I'm looking at are the Troels G. CA18RLY one and the SEAS Mimir, since they have the right kind of mid-bass for a sealed box.
http://www.troelsgravesen.dk/SEAS_CA18RLY-COMPACT.htm
https://www.seas.no/index.php?optio...d=381:mimir-seas-diy-kits&catid=66&Itemid=345
https://www.seas.no/images/stories/diykits/pdfdataheet/mimir_plans.pdf
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There's always the SS 18W8542. Its been used by proac in their monitors with great success and has very natural, precise low end with really good power handling. It doesn't go any lower than the Seas, but its a bit more linear and has some of the best midrange I've heard from a 7" paper cone. It uses a new generation foam surround, which i believe is the best material for midrange neutrality.
The slit cone SS 18W8531 is another great one if you want something suitable for a sealed box. It goes pretty low and has good xmax. Most of the SS drivers are great and have low distortion motors.
I'm not all that fond of the P17WJ00-08 because of the higher IMD in the lower mids, very similar to the P21 poly cone driver. The P17 however has very linear FR, which may be more of an advantage vs the smidge higher IMD than the rest. It is cheap, but for a reason. I'd only go with the higher end motor of the SS 18Ws. To me they sound the best in the lower mids and have great resolution where it counts.
Thinking outside the box, there is also the SB Acoustics 6MW150D, which I really like alot. It also doesn't go quite as low as the other 6s, but the sensitivity is high, around 94 dB / 2.83V. Its VC is a whopper at 54mm, which isn't common for a 6 inch driver with rubber surround. It also has a vented fiberglass VC former, which IMO is the best material for stiffness, weight and damping.
The slit cone SS 18W8531 is another great one if you want something suitable for a sealed box. It goes pretty low and has good xmax. Most of the SS drivers are great and have low distortion motors.
I'm not all that fond of the P17WJ00-08 because of the higher IMD in the lower mids, very similar to the P21 poly cone driver. The P17 however has very linear FR, which may be more of an advantage vs the smidge higher IMD than the rest. It is cheap, but for a reason. I'd only go with the higher end motor of the SS 18Ws. To me they sound the best in the lower mids and have great resolution where it counts.
Thinking outside the box, there is also the SB Acoustics 6MW150D, which I really like alot. It also doesn't go quite as low as the other 6s, but the sensitivity is high, around 94 dB / 2.83V. Its VC is a whopper at 54mm, which isn't common for a 6 inch driver with rubber surround. It also has a vented fiberglass VC former, which IMO is the best material for stiffness, weight and damping.
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May I ask how much power your amp can deliver? You should include the power output into your decission.
I know that you are a follower of the closed box religion. Maybe you consider that not all religions lead you to heaven?
If you use a vented system, you get like 100% more amp power at the lower frequency, for free.
Also, the thing about closed bass being more precise than vented, is as real as a supersonically flying goat for VIP transportation.
Don't isolate your self from some of the best options for your situation, just by being stubborn.
Just some idea...
I know that you are a follower of the closed box religion. Maybe you consider that not all religions lead you to heaven?
If you use a vented system, you get like 100% more amp power at the lower frequency, for free.
Also, the thing about closed bass being more precise than vented, is as real as a supersonically flying goat for VIP transportation.
Don't isolate your self from some of the best options for your situation, just by being stubborn.
Just some idea...
Maybe you find something interesting here: https://www.der-akustische-untergrund.de/
These guys are some of the top DIYS developer in Germany. They give these, sometimes non commercial award wining designs, to you for free.
They are 98% non commercial and do really good designs. The downside, if they publish a new constructions, a few days later the retailers usually outreageously increase the chassis prices and/or they are sold out after a week.
You can make huge savings if you don't go for the boutique x-over parts and use standard industrial material. Just as good, only a fraction in price. For example a 4uF MKP 250V capacitor without "Mundorf" writen on it is sold at a fraction of a "special audio" part. There is not even one scientific proof that caps with silver and gold mixed in have the smallest advance over a "normal" WIMA or EPCOS part of the same specification.
Same goes for coils. Tight wound and solid copper, maybe dipped in some epoxy. That's state of the art. The rest is marketing snake oiling.
Anyway, you find really good stuff there. Google translator is your friend, if you miss something, just ask for a translation here.
These guys are some of the top DIYS developer in Germany. They give these, sometimes non commercial award wining designs, to you for free.
They are 98% non commercial and do really good designs. The downside, if they publish a new constructions, a few days later the retailers usually outreageously increase the chassis prices and/or they are sold out after a week.
You can make huge savings if you don't go for the boutique x-over parts and use standard industrial material. Just as good, only a fraction in price. For example a 4uF MKP 250V capacitor without "Mundorf" writen on it is sold at a fraction of a "special audio" part. There is not even one scientific proof that caps with silver and gold mixed in have the smallest advance over a "normal" WIMA or EPCOS part of the same specification.
Same goes for coils. Tight wound and solid copper, maybe dipped in some epoxy. That's state of the art. The rest is marketing snake oiling.
Anyway, you find really good stuff there. Google translator is your friend, if you miss something, just ask for a translation here.
I have Rehdeko RK 125-5s speakers . They are around 50 liters and reside in corners of 3m x 3m bedroom . Stiff, treated 10" Audax driver in 12" chassis has FS around 100Hz 96db . The box is ported but measures like a closed box with single hump. frequency is fairly flat down to 60hz. Forget most DIY audio has to offer when dealing with 2A3/300b power levels. All that Scanspeak crappola and Troels an rest of gurus. Get a design with a big, efficient woofer with highish fs . No useless 30-40 Hz FS rubber sounding boomers
Two suggestions from turbowatch and limono - thanks guys, I appreciate your interest in the thread. Criticism is fine!
- don't ignore ported designs. Indeed, I might end up there. But I'd first like to try sealed boxes. I can add a port at some point. But if I only use mid-bass drivers suitable for ported designs I can't go the other way and convert to sealed box. My shortlist of drivers covers either option.
- My SE amps are fine for the room size and I don't listen loud, so no problem there. Quality not quantity.
- use bigger mid-bass units. I have a pair of B200 which would be happier in a larger floorstander. They may come later in another build. But I can't go too big - my listening room is 4.5 x 3.5 metres and there's quite a lot of stuff in it already. A floorstander would have to be fairly slim, though the height is OK. But I hesitate to build a large enclosure, see below.
Believe it or not I used to have stacked Quad 57 speakers in my room at one point, replaced with Apogee Caliper Sigs. Trouble was I couldn't see out of the windows. I'd use panels if I could, but that was in the madness of my youth. These days I like a little space to move around in.
Well, if pro drivers in ported boxes are an option for you as someone passionately pointed out, my ultimate suggestion would be the B&C 8NDL51. It does very well in a QB3 aligned 20 ltr box tuned to 60 hz. A solid 93 dB/w is very good for an 8" bass-mid. Its my favorite pro driver for a 2 way or dedicated midbass.
There's also the Eminence Beta 8A, which is a phenomenal driver for a bass restricted 2 way. Its one of the best kept secrets for a high sensitivity midbass and has the sweetest sounding midrange I've heard at any price, despite being a stamped frame driver. Its also a 60 hz cutoff driver in a smaller ported box. I've use it in 25 ltrs QB3 at 60 hz. It won't move any mountains in low end but it makes up for it everywhere else.
There's nothing wrong with a soft surround driver, as long as the surround is well dampened. Foam is best and has the least coloration. Accordian surrounds can also have nasty resonances, sometimes worse than rubber. The 700 -1k wiggle you see on most 6 - 8" drivers is the telltale thing to look for along with the bump in the impedance curve. The worse the bump, the more intrusive the resonance.
I don't Iike all SS drivers, but the paper and slit cone drivers with foam surrounds are very nice, high resolution pieces. The motors are very good. For the money, I usually favor the B&C and Eminence drivers for higher sensitivity stuff. There are a few other hidden gems from PRV, Beyma, SB and Celestion as well. That SB 6MW150D is a bargain. Its a pretty fancy driver for $90.
There's also the Eminence Beta 8A, which is a phenomenal driver for a bass restricted 2 way. Its one of the best kept secrets for a high sensitivity midbass and has the sweetest sounding midrange I've heard at any price, despite being a stamped frame driver. Its also a 60 hz cutoff driver in a smaller ported box. I've use it in 25 ltrs QB3 at 60 hz. It won't move any mountains in low end but it makes up for it everywhere else.
There's nothing wrong with a soft surround driver, as long as the surround is well dampened. Foam is best and has the least coloration. Accordian surrounds can also have nasty resonances, sometimes worse than rubber. The 700 -1k wiggle you see on most 6 - 8" drivers is the telltale thing to look for along with the bump in the impedance curve. The worse the bump, the more intrusive the resonance.
I don't Iike all SS drivers, but the paper and slit cone drivers with foam surrounds are very nice, high resolution pieces. The motors are very good. For the money, I usually favor the B&C and Eminence drivers for higher sensitivity stuff. There are a few other hidden gems from PRV, Beyma, SB and Celestion as well. That SB 6MW150D is a bargain. Its a pretty fancy driver for $90.
I I have a nice speaker for you http://www.troelsgravesen.dk/QUATTRO.htm
or http://www.troelsgravesen.dk/8008-CORNER.htm
or http://www.troelsgravesen.dk/DTQWT-mkIII-FLAT.htm
rank your priorities. If they stand in the middle of the room cause your bow window, go for a slim floorstand to increase the Vb for bass according what the driver needs. The Beta 8-a has a strong reputation of good sound for the price and I surmise paper is what you need because of your SE tube tastes.
To lowish the cost, go ready made design or second hand. Never forget to go towards highish impedance and sensivity cause your amp.
To lowish the cost, go ready made design or second hand. Never forget to go towards highish impedance and sensivity cause your amp.
Sure, small drivers can sound good but nothing beats surface area when it comes to reproducing bass.
The Fane Sovereign Pro 8-225 would be a very attractive driver for your cause. Don't judge it by it's low price, PA speaker are often many times the value of HIFI-DIYS stuff. You got to find a tweeter that will keep up with it, probably a 30mm 4 Ohm dome. 20 liters is at the low side, but inside a small room should work well if you need no bass monster.
Funny, I searched online for Fane Sovereign Pro 8-225 less than an hour ago. It's not me that is looking for driver recommendations here but this thread is having a bad influence on me: I already have two big systems in my small house, the one in post 48 and another in the next room with corner bass horns, direct radiating JBL 2202H 12" midbass/mids in small ported cabs and LeCleach horns from 1200Hz and up.
Good systems both of them if I may say so myself, but I'm contemplating the possibility to add a third system somewhere in the house. Something very mimimalistic, like a pair of 6,5-8" fullrange drivers driven by a small SET and with only analog sources.
Opposites attract, and I guess this would be the opposite of the multi-amped 4-way system in my hobby room.
Good systems both of them if I may say so myself, but I'm contemplating the possibility to add a third system somewhere in the house. Something very mimimalistic, like a pair of 6,5-8" fullrange drivers driven by a small SET and with only analog sources.
Opposites attract, and I guess this would be the opposite of the multi-amped 4-way system in my hobby room.
Three pages of thread and no discussion about SPL requirements vs F-3dB and accompanying volume displacement with relative low distortion figures? For closed enclosures and a 6" driver I would do this sanity check first. You need a rather long throw unit for substantial sound pressure levels and reasonable bass. Just my 2ct.
This is not very important to the thread starter. He uses a small valve amp. So high excursion is no demand, as the amp can not supply the power to push a cone that far. Any high excursion driver is in the wrong place here.
This is why some here point to a larger than 6.5" driver and a vented inclousure. This is the only way to get decent dynamics and some bass from a tiny amount of amp power.
The logical way is to go for high effiency, which leads to a large cone, a wave guided tweeter, vented enclosure and usually a high quality PA driver. That is what physics dictate. That does not mean that the thread starter is going this way, some have to find out by them selves, a well known thing with DIYS. You are free to do what you want...
This is why some here point to a larger than 6.5" driver and a vented inclousure. This is the only way to get decent dynamics and some bass from a tiny amount of amp power.
The logical way is to go for high effiency, which leads to a large cone, a wave guided tweeter, vented enclosure and usually a high quality PA driver. That is what physics dictate. That does not mean that the thread starter is going this way, some have to find out by them selves, a well known thing with DIYS. You are free to do what you want...
I missed the small amp part, but a Scan Speak 18W8531G in a 20l enclosure maxes out at 40 Hz and everything lower than that with about 10V or 12W peak. For that calculation I'm using the simple rule of thumb that a driver acts linearly as long as the voice coil stays in the gap. Even a Revelator isn't very linear any more at these excursion levels. Let alone the trouble mid bass speakers have to produce undistorted midrange when big excursions are at play. So I still think Vd has to be considered, even with sub-20W amps, even if it only were to get those peak levels at about 90dB/1m right.