3-way for bookshelf (in-wall/on-wall)
I need your help fellow DIYers!
A friend of mine is going to have his living room completely redesigned and a custom bookshelf made to fill the entire lower part of one end wall. He has asked me if I wanted to build some speakers for his new setup. The idea is to have the speakers hidden inside this bookshelf. I have attached a 3D rendering of what it’s going to look like. The two red arrows are where the speakers will be.
I know that most speaker design are tuned with BSC to be placed away from the back wall. In this setup however, the speakers will almost be in-wall when the bookshelf is filled up with books etc. Most speakers will sound bloated in the mid bass if positioned here. Are you aware of any good designs out there that would work for this setup?
Additional info: The room is quite large at about 60m2 and 3m to the ceiling. Each bookshelf is big enough to have a speaker of 50 litres internal volume. I will take part in the construction of the bookshelf and make sure it will be stable enough to support the speakers and not vibrate.
I was hoping there was a good 3-way bass-reflex design out there that would work in this setup? Budget is 1000 EUR.
Suggestions and recommendations are welcome.
Thanks!
I need your help fellow DIYers!
A friend of mine is going to have his living room completely redesigned and a custom bookshelf made to fill the entire lower part of one end wall. He has asked me if I wanted to build some speakers for his new setup. The idea is to have the speakers hidden inside this bookshelf. I have attached a 3D rendering of what it’s going to look like. The two red arrows are where the speakers will be.
I know that most speaker design are tuned with BSC to be placed away from the back wall. In this setup however, the speakers will almost be in-wall when the bookshelf is filled up with books etc. Most speakers will sound bloated in the mid bass if positioned here. Are you aware of any good designs out there that would work for this setup?
Additional info: The room is quite large at about 60m2 and 3m to the ceiling. Each bookshelf is big enough to have a speaker of 50 litres internal volume. I will take part in the construction of the bookshelf and make sure it will be stable enough to support the speakers and not vibrate.
I was hoping there was a good 3-way bass-reflex design out there that would work in this setup? Budget is 1000 EUR.
Suggestions and recommendations are welcome.
Thanks!
Attachments
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Hi,
Its debatable how much BSC they would need,
more than inwall IMO, but less than normal.
You can argue until the cows come home but IMO
Zaph|Audio - ZDT3.5
you could do a lot worse the the centre version x/o,
noting the design axis is 12" above the tweeter.
40L to 50L vented is ideal for the design.
No subs I'd low tune vented, i.e. simply use
one of the shown vents instead of two.
YMMV but I don't think you'l find a better design.
rgds, sreten.
Its debatable how much BSC they would need,
more than inwall IMO, but less than normal.
You can argue until the cows come home but IMO
Zaph|Audio - ZDT3.5
you could do a lot worse the the centre version x/o,
noting the design axis is 12" above the tweeter.
40L to 50L vented is ideal for the design.
No subs I'd low tune vented, i.e. simply use
one of the shown vents instead of two.
YMMV but I don't think you'l find a better design.
rgds, sreten.
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Thanks for the input. That looks like an interesting design. I was previously on the parts-express forum where CJD’s In-Khan-Neatos design was recommended, which also uses Dayton drivers. I tend to avoid Dayton (and other American brands) since they’re much more expensive here in Europe compared to over there. I was hoping to find a design using SB, Peerless, Vifa, ScanSpeak, SEAS etc, but perhaps this is unrealistic (?).
Anyway, back to your suggestion. If using the ZD3C I guess I would need to modify the baffle layout and place the tweeter above the midrange since the speakers will be placed slightly below listening position. Actually the tower option baffle layout would be more suitable for my application, although I would need to change the port placement to make it all fit on the baffle, which need to fit inside the hole of the bookshelf, about 68 cm tall and 34 cm wide. But after changing the baffle layout, do you think Zaph's XO will be any good?
I'm concerned about Zaph's comment on the ZD3C:
It's worth noting here that some builders may be wondering if it's a good idea to just build 3 of this design and use them turned upright for lefts and rights also. In a word, no. There's too much in the design that is specific to center channel usage but not suitable for mains. Controlled vertical off axis with wide horizontal off axis, along with low BSC are perfect for a center, but turn into serious shortcomings when used for an upright left and right.
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You may want to take a look at some of the other Zapf designs. Some indeed use other drivers. I highly respect his design methods. Zaph|Audio
Hi,
Zaph comments are pretty pointless, as they address the stupid,
and don't address the clued. Yes its a very bad idea to simply
turn the centre upright for L&R but that is totally clueless.
Of course I'm implying using the centre x/o with the normal
L&R vertical baffle layout and it will work then as implied.
Is obvious you need to maintain vertical mid / treble.
rgds, sreten.
Zaph comments are pretty pointless, as they address the stupid,
and don't address the clued. Yes its a very bad idea to simply
turn the centre upright for L&R but that is totally clueless.
Of course I'm implying using the centre x/o with the normal
L&R vertical baffle layout and it will work then as implied.
Is obvious you need to maintain vertical mid / treble.
rgds, sreten.
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The location is not only on-wall but also on-floor. A woofer at the bottom of your baffle will radiate into a quarter space. I doubt you will find any popular designs suitable for this location. However the woofer is going to be efficient in this location.
The speakers are a bit low and so the tweeter will have to go at the top and probably a bit too close to the top edge. A waveguide would help but may be impractical. Perhaps the SEAS DXT?
The midrange may need to be largish or perhaps doubled if you are to run with an efficient design. Again a waveguide on the tweeter may help.
There may be some sound quality issues from the bookcase cavities, cancellation due to reflection off the back wall and structure-borne radiation from the large surface area of the bookcase. The latter would be improved by normal soffit mounting techniques but not sure much can be done about the others.
It looks like a nice project and it will be interesting to see what you come up with.
Gotcha. So you reckon it would be okay to take the baffle layout of the ZDT3.5 tower and then use the XO of the ZD3C? I will have to widen the baffle slightly as well, and have front-firing ports. Something like the attached drawing?
A thing to consider though is that the RS52 midrange dome sticks out about 2cm from the baffle, and because I will need to attach grille cloth the speakers will have to be pushed into the bookcase a couple of cm, which I’m sure won’t have a positive effect on the sound?
Attachments
Thanks for pointing out the issues related to having the speakers close to the floor. You suggest a waveguide, but without a design suggestion (or least a starting point) I’m in a bit of a loss here
I have built speakers before, but always based on a proven design.For this project I initially thought of some of the 70s classic 3-ways, which were designed with less BSC for the purpose of near-wall / bookshelf placement. Does anyone know of a modern design based on these speakers? I asked Troels Gravesen about his 3-Way Classic, but he told me the 3WC was designed for away-from-walls placement and wouldn’t recommend the design for my setup.
By the way, I recalculated the bookshelf dimension and could actually accommodate speakers with an internal volume of 60 litres.
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Your location will boost the bass a lot and mean both the in-room and on-wall "baffle step correction" circuitry will be wrong in existing designs. It also means that the choice of sensitivities for midrange and woofer in existing designs is likely to be less than ideal. If you choose to design the crossover yourself then you have the opportunity to make a significantly more efficient speaker with the benefits that brings. Alternatively you could make an existing design intended for an on-wall or in-room location and then electronically equalise it for your location.
I would expect a standard 3 way to be more appropriate for your location than multiple small drivers in a narrow baffle design. Are you looking at 10" or 8" sized woofers? Something like the cited 3 way classic using easy to work with drivers from the standard SEAS or Scan-Speak range might be a good place to start for your own design.
Well, I’m intrigued by the idea of designing my own 3-way for this project, but I’m doubting whether I can expect as good results as e.g. the modified ZDT3 sreten suggested?
Anyway, I was looking at the Scan-Speak Discovery range and there are some interesting drivers. What do you think of something like this?
Sealed 3-way WMT, 55 litres, F3 ~40Hz:
- Woofer: 10'' 26W/8534G00 - 8 ohm - 89dB
- Midrange: 5.5’’ 15M/4624G00 - 4 ohm - 92.4dB (400-2500Hz)
- Tweeter: 1” D2604/830000 - 4 ohm - 92.1dB
Soren, I do wonder if designing an expensive built in 3 way is really what you want to do here. 
I would be tempted to do a two way modelled in Visaton Boxsim. For wall placement.
Not hard to give it a smaller than usual bafflestep coil. Maybe 1mH. This thread will give you some idea of a good sounding filter:
http://www.diyaudio.com/forums/multi-way/245917-diy-kef-celestion-6.html#post3868470
I would think 30-50 Litres reflex with a W200S bass speaker. Tweeter to suit. I use cone tweeters myself. Should come out a bit like the WLM La Scala:
I would be tempted to do a two way modelled in Visaton Boxsim. For wall placement.
Not hard to give it a smaller than usual bafflestep coil. Maybe 1mH. This thread will give you some idea of a good sounding filter:
http://www.diyaudio.com/forums/multi-way/245917-diy-kef-celestion-6.html#post3868470
I would think 30-50 Litres reflex with a W200S bass speaker. Tweeter to suit. I use cone tweeters myself. Should come out a bit like the WLM La Scala:
An externally hosted image should be here but it was not working when we last tested it.
I actually have a Behringer ECM8000 mic with a XENYX 302 USB mixer, which I’ve previously used for EQ and active subwoofer integration, but never for passive crossover design.
Thanks for the input, Steve.Soren, I do wonder if designing an expensive built in 3 way is really what you want to do here.
I would be tempted to do a two way modelled in Visaton Boxsim. For wall placement.
Not hard to give it a smaller than usual bafflestep coil. Maybe 1mH. This thread will give you some idea of a good sounding filter:
http://www.diyaudio.com/forums/multi-way/245917-diy-kef-celestion-6.html#post3868470
I would think 30-50 Litres reflex with a W200S bass speaker. Tweeter to suit. I use cone tweeters myself. Should come out a bit like the WLM La Scala:
An externally hosted image should be here but it was not working when we last tested it.
Everything is relative of course, but I don’t think my idea for a 3-way Scan-Speak would be expensive. I picked out some of the cheapest drivers they have. You should also take the budget into consideration and the fact that I don’t really need to worry about cabinet finishing as the speakers will be built into the bookcase.
Of course a Visaton 2-way would be cheaper, but it would also give me less sensitivity and power handling, which I think would be nice to have in a large 60m2 room with 3m ceilings.
Anyway, thanks for the suggestion. I will have a look at the thread and the Boxsim software.
Some (very) personal ideas about your project.
You never designed a speaker, and nevertheless you want to design a 3-way as a first project. The fact that your plan imply a speaker with tweeter not at ear level, a woofer near the floor and with a BSC unknown, and resonance from the partially void bookshelf are problems on top.
And more important, you are doing this for a friend. Think what can happen if the project won't succeed (and there is a big chance on that). For a friend I'd only build a proved design that he had chosen - period.
If your friend doesn't want a tower on the floor there is enough space on (not in) the bookshelf to place a, well, bookshelf speaker. Some designs even provide a reduced BSC option for this arrangement, see here for an example: Zaph|Audio - ZA-SR71
Ralf
You never designed a speaker, and nevertheless you want to design a 3-way as a first project. The fact that your plan imply a speaker with tweeter not at ear level, a woofer near the floor and with a BSC unknown, and resonance from the partially void bookshelf are problems on top.
And more important, you are doing this for a friend. Think what can happen if the project won't succeed (and there is a big chance on that). For a friend I'd only build a proved design that he had chosen - period.
If your friend doesn't want a tower on the floor there is enough space on (not in) the bookshelf to place a, well, bookshelf speaker. Some designs even provide a reduced BSC option for this arrangement, see here for an example: Zaph|Audio - ZA-SR71
Ralf
That is for you to judge. What makes the ZDT3 a good design? If you look at built in 3 way speakers used by studios what do they tend to look like and why? If learning to design a crossover is not something you are going to enjoy then it is probably unwise to pick it up as task.
It looks like a solid starting point. You may want to consider woofers with more bass extension, possibly vented that still fit your volume but they will be more expensive.
If you have Microsoft Excel (I don't) then you can download Jeff Bagby's set of speaker design programs and almost certainly pick up a fair amount of help and guidance on a forum like the Parts Express one (the help is the main attraction of the software). The software includes both baffle diffraction and I believe location near walls and floors. You can do this immediately using the published curves for the 3 drivers above and see how you get on. When the design has settled you can buy the drivers and repeat using the real curves which might tweak the odd value here and there in the crossover.
I think those were actually some of the reasons to do my own design, since no proven design is tuned for this apparently unusual speaker placement.
Excuse me Ralf, but I’m just looking for advice here. I was actually on the search for a proven design, but as this turned out to be difficult, andy19191 suggested to do my own design.
Maybe I haven’t made myself clear here. My friend and his wife are having their living room redesigned and together with the interior designer, who is also a friend of mine, we’re trying to included (hide) the stereo system inside the custom designed bookshelf. The primary objective here is design aesthetics and not sound quality. In other words, freestanding towers or speakers on top of the bookshelf is not an option. The bookshelf is going to be like I showed in my first post and the speakers will go in there. I’m trying to find the best possible solution given these restrictions.
I’m sure I will enjoy learning more about passive crossover design
If vented I would probably have to go for an 8” given the size restrictions. The 10” 26W/8534G00 in a sealed 55 litres gave me an F3 of 40Hz, but I need to simulate more. Perhaps the bass could even be extended with an LT circuit? I will do some more research about this.
I have Excel yes, and I’ve actually played around with Jeff B’s software before. I will try to do some simulations.
Then fill the space with a simple 2.1 system. It doesn't make any sense to put a large amount of money on a mediocre system, if you don't have the necessary ability and experience to create a good solution. A 3-way is much more complex than a 2-way, and you have also some constraints on top of that.
But, again, the primary objective is really shared with your friend? What happens if the speaker won't sound good? You should take in consideration the fact that you could not succeed in designing a good sounding speaker. In other words, a failure can easily happen and you are blamed for the not good sounding speaker built into that beautiful and unmovable piece of furniture.
I gave you my advice, but you don't want to listen. It is quite normal to only listen to what one wants to hear, but a wise person should realize a mistake, and understand if he is up to the task. I don't think that the project is not doable, but is for an experienced designer.
BTW, have you ever asked Troels Gravesen about what he wants to design the speakers you need? (don't know if he do such activities, but you don't have anything to lose).
Ralf
Extending the bass with circuitry is unlikely to be of much benefit because the driver has a limited linear excursion. A more expensive driver may have twice the linear extension and with the contribution from a port could maintain maximum SPL into the mid 30s.
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