Hi!
I'm a general enthusiast when it comes to building things with my own hands, and I have always liked music systems. I always had quite a nice stereo set (2 home-built 3-way speaker, Rotel pre-amp, NAD amp, Sony QS series CD player, ...). I'm a physicist by trade, and in my spare time I build bikes. I know how to solder decently and I understand a bit of electronics. But as I see enough electronics in my workplace, I generally prefer working with more crude tools when I get home.
Now my girlfriend was never a big fan of the huge, black 3-ways, and so when on a flea market she spotted some old Grundig 70's funky design speakers (came with a broken amp/turntable combo), I bought them for almost nothing with the plan to make them into a little project of speakers we both would like (looks and sound)
The speakers are little spheres of brushed Al, and after removing the oooooold stuf that was inside, now they house small full range fostex FF85wk's with a small reflex port. No filters.
The sound in the mids is fine, but compared to the 3-ways, I miss the bass.
So now my plan is to add a sub to the system. I have a single, highly efficient 12" paper cone woofer still lying around somewhere that I could use. So that will definitely be the next project.
Now for the questions: My amp (the NAD 216 THX) is stereo, and so will not be able to drive the woofer. Or I bridge it, and then I need something else to drive the full range speakers. In any case: I will need to change my amp configuration. But what is the best choice?
I wouldn't mind keeping the 3-ways and the NAD together, as they make quite a perfect combo. And I have to buy an amp anyway, so why not get a 2.1 amp straight away, and be done with it?
I have been browsing around the amp section, and have found cool stuff I never knew existed, but i did not stumble upon my perfect solution.
I was thinking of a few configurations (but please feel free to criticize or add option I have not thought of yet):
1) build the sub with a built-in class D amp which can also drive the 2 full range speakers with low/high pass filter (either in the amp or separate). Clean look, but I have not found a good model yet, but probably I overlooked it (this must exist no?)
2) A set of 2 T-class amps, one bridged or mono for the woofer, one for the full ranges. Will need a pre-amp that can drive this (4 outputs or 2+1) and will need 2 filters. Easy woofer design, as the amp will be table-top and not built-in.
3) Get a ready and stand alone 2.1 amp. So far I have only found Harman Kardon options for 2.1 (and some exotic german stuff). But how would you rate the quality of for example a HK BDS 270 (i don't have a blu-ray player yet, so hey, why not...)
And I listen to all kind of musics (from electronic to Bossa Nova via some beastie boys), listen to the radio, will connect my laptop and watch movies once in a while etc. So multi-purpose it shall be... And I gave up the idea of true High End sound a while ago, so 2000 EUR amps will not be considered
Thanks already for the advice or ideas you might bring!
MDA
I'm a general enthusiast when it comes to building things with my own hands, and I have always liked music systems. I always had quite a nice stereo set (2 home-built 3-way speaker, Rotel pre-amp, NAD amp, Sony QS series CD player, ...). I'm a physicist by trade, and in my spare time I build bikes. I know how to solder decently and I understand a bit of electronics. But as I see enough electronics in my workplace, I generally prefer working with more crude tools when I get home.
Now my girlfriend was never a big fan of the huge, black 3-ways, and so when on a flea market she spotted some old Grundig 70's funky design speakers (came with a broken amp/turntable combo), I bought them for almost nothing with the plan to make them into a little project of speakers we both would like (looks and sound)
The speakers are little spheres of brushed Al, and after removing the oooooold stuf that was inside, now they house small full range fostex FF85wk's with a small reflex port. No filters.
The sound in the mids is fine, but compared to the 3-ways, I miss the bass.
So now my plan is to add a sub to the system. I have a single, highly efficient 12" paper cone woofer still lying around somewhere that I could use. So that will definitely be the next project.
Now for the questions: My amp (the NAD 216 THX) is stereo, and so will not be able to drive the woofer. Or I bridge it, and then I need something else to drive the full range speakers. In any case: I will need to change my amp configuration. But what is the best choice?
I wouldn't mind keeping the 3-ways and the NAD together, as they make quite a perfect combo. And I have to buy an amp anyway, so why not get a 2.1 amp straight away, and be done with it?
I have been browsing around the amp section, and have found cool stuff I never knew existed, but i did not stumble upon my perfect solution.
I was thinking of a few configurations (but please feel free to criticize or add option I have not thought of yet):
1) build the sub with a built-in class D amp which can also drive the 2 full range speakers with low/high pass filter (either in the amp or separate). Clean look, but I have not found a good model yet, but probably I overlooked it (this must exist no?)
2) A set of 2 T-class amps, one bridged or mono for the woofer, one for the full ranges. Will need a pre-amp that can drive this (4 outputs or 2+1) and will need 2 filters. Easy woofer design, as the amp will be table-top and not built-in.
3) Get a ready and stand alone 2.1 amp. So far I have only found Harman Kardon options for 2.1 (and some exotic german stuff). But how would you rate the quality of for example a HK BDS 270 (i don't have a blu-ray player yet, so hey, why not...)
And I listen to all kind of musics (from electronic to Bossa Nova via some beastie boys), listen to the radio, will connect my laptop and watch movies once in a while etc. So multi-purpose it shall be... And I gave up the idea of true High End sound a while ago, so 2000 EUR amps will not be considered
Thanks already for the advice or ideas you might bring!
MDA
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Hi mda1,
CONSIDER building two cute woofers below the two little Fostex F85K Grundig spheres for a 2.0 stereo.
Some clever men L_O_A_N their girlfriend their 3-way speakers and B_O_R_R_O_W her little spheres WITH THE PROMISE to build a small, clever, bass module for each little sphere. Good quality 2-way stereo.
A physicist would know that a <60Hz bass signal's physical location can be identified, and decide to build decent 2.0 stereo speakers with stereo local bass below each Fostex F85k little sphere.
Some clever men would take a bottle of RED wine and some chocolates to a woman's home with a few sketches of cute/clever bass cabinets for her 2.0 stereo. A single 8" or two 7" woofers for higher SPL/watt efficiency can reach below 40Hz. Clever men always listen and adapt ideas.
Any sketches for cute/clever bass cabinets that diyAudio can help review?
Married family men often have flat panel TVs on the wall with 3-way controlled directivity speakers up-against-the-wall(corner) so ALL HEAR a rich soundstage. The speakers you are building could end up in ????
Ha... good advise on all levels. The spheres are actually still at my place being run in... She knows I am working on something, but I think she has a bit forgotten about these speakers, so it will be bit of a gift / surprise. And she definitely does not want the big 3 way speakers at her place
She has no particular interest in coupling sound systems to televisions, but I will do that for her anyway, knowing full well that 95% of the time it will be used to play music from CD's, iPod or laptop. At her place there is no wall behind the television, so wall mounting is no option.
The fact that I have this one high quality 12" driver lying around is the reason I originally thought in the direction of the 2 fostex + 1 sub. First of all it's a waste leaving it there to accumulate dust. Secondly it keeps the project cost down... So I would first like to explore the options with this driver before deciding to change course, and buy new smaller drivers.
In terms of design: I had a look on diysubwoofers.org, and started calculating box sizes and I took a sealed design to start with. From the volume calculations, I noticed that the 'optimal' size for this 12" in sealed configuration was euhm... huge . The ported version is a bit more acceptable, but still big at 90 liters. One idea that shot through my mind was to make a TV cabinet (nothing more than a flat wide box the TV can stand on) that ís the sub. This way it can be huge and at the same time 'invisible'. If I have the driver face to the floor, with spikes to lift the whole sub about an inch off the floor, will that work? With a plate amp built into the sub, I would put the TV, a pre-amp (depending on the choice of sub amp) a dvd player and the spheres on top of this sub / cabinet. Or will the amp vibrations destroy or interfere with the TV and / or any other equipment standing on top (DVD player...)?
I don't have sketches yet, but as soon as I draw something up, I'll upload it here.
Thank already for the advice!
She has no particular interest in coupling sound systems to televisions, but I will do that for her anyway, knowing full well that 95% of the time it will be used to play music from CD's, iPod or laptop. At her place there is no wall behind the television, so wall mounting is no option.
The fact that I have this one high quality 12" driver lying around is the reason I originally thought in the direction of the 2 fostex + 1 sub. First of all it's a waste leaving it there to accumulate dust. Secondly it keeps the project cost down... So I would first like to explore the options with this driver before deciding to change course, and buy new smaller drivers.
In terms of design: I had a look on diysubwoofers.org, and started calculating box sizes and I took a sealed design to start with. From the volume calculations, I noticed that the 'optimal' size for this 12" in sealed configuration was euhm... huge
. The ported version is a bit more acceptable, but still big at 90 liters. One idea that shot through my mind was to make a TV cabinet (nothing more than a flat wide box the TV can stand on) that ís the sub. This way it can be huge and at the same time 'invisible'. If I have the driver face to the floor, with spikes to lift the whole sub about an inch off the floor, will that work? With a plate amp built into the sub, I would put the TV, a pre-amp (depending on the choice of sub amp) a dvd player and the spheres on top of this sub / cabinet. Or will the amp vibrations destroy or interfere with the TV and / or any other equipment standing on top (DVD player...)?I don't have sketches yet, but as soon as I draw something up, I'll upload it here.
Thank already for the advice!
Ok. So. Change of plans.
The old 12" driver that I had, and was stored in the garage for a while seems to have suffered some damage while being stored... So that one is unfortunately ripe for the trashbin.
That is a bad thing and a good thing. Bad because it is a waste of this old driver. Good because now I can choose any (and maybe better) option for my bass.
Also the 2.1 configuration is now not a requirement any more (although I could still consider it of course).
What would be the best combination according to your accumulated acoustic wisdom? 2-way with nice looking mid/woofers? or still a separate sub?
All advise is welcome!
The old 12" driver that I had, and was stored in the garage for a while seems to have suffered some damage while being stored... So that one is unfortunately ripe for the trashbin.
That is a bad thing and a good thing. Bad because it is a waste of this old driver. Good because now I can choose any (and maybe better) option for my bass.
Also the 2.1 configuration is now not a requirement any more (although I could still consider it of course).
What would be the best combination according to your accumulated acoustic wisdom? 2-way with nice looking mid/woofers? or still a separate sub?
All advise is welcome!
Are your sphere speakers on a floor pole stand as common with 1970's Grundigs? Some woofer cabinets can be designed to integrate with the pole stand.
If your sphere speakers are on "stubby" stands, then you can decide between attaching them to one long media cabinet or two separate woofer cabinets.
Two full range speakers will sound better than a single woofer plus two FF85wk spheres.
If your sphere speakers are on "stubby" stands, then you can decide between attaching them to one long media cabinet or two separate woofer cabinets.
Two full range speakers will sound better than a single woofer plus two FF85wk spheres.
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you can get a self powered sub, they work by running your L&R speaker connections to it and from there to your speakers. They have several resistors in the line so your amp never sees the load. That would be the simplest and easiest way, Parts Express may still have one that fits under the couch (I think it is an 8 inch)
1) The Fostex FF85WK 3" Full Range Fs=115Hz 86.5db/watt 7.2ohms requires a Xover frequency to the woofer that is well above the 60Hz-80Hz "single woofer" limit recommended in well-reviewed literature. Stereo woofers directly below each Fostex will sound the best.
2) The Grundig HiFi 210a is 7.5" in diameter. Putting the center of the Grundig HiFi 210a at a 39" ear height is a good starting point for the bass cabinet design.
3) A single 8" woofer (( like the Scan-Speak Discovery, 22W/8534G00, 8" Midwoofer, 8 ohm fs=30Hz Qts=0.39)) might be a cost effective design point in your country. The resulting 11" wide cabinet style should marry well with the 7.5" diameter sphere. The woofer should be near the top of the cabinet to best blend with the Fostex. SO.... start looking for decent, low cost 8" woofers with low Fs and Qts about 0.33 to 0.44.
Two 8" woofers would naturally provide deeper bass, and have enough SPL efficiency to cover the baffle step loss (when the bass sine wave gets longer than the width of the cabinet baffle, and the woofer energy starts to get shared with 360 degree room volume) and you might decide on a 2.5 way design where the bottom woofer mainly covers baffle step loss.
4) A ported bass cabinet with a round vent near the floor is a good starting design for your sketch. CUTE often demands small volumes which support only one woofer.
5) Crossovers will likely be your largest challenge.
Thanks you LineSource for the very constructive reply! I understand all steps except '5'. Why will the crossover be a particular challenge? I have no previous knowledge on crossover filters, so I have no feel for if and why a particular crossover could be potentially challenging... Could you elaborate on that?
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