Beginner question/s OB

tjthe1st · 8th December 2007, 08:12 AM

Hi all

I’ll start of by introducing myself. I live in Canberra at the moment, though I move around a fair bit with my job. After seeing my dad build himself a set of loudspeakers a few years ago I thought “I could do that” as I have done a reasonable amount of woodworking in the past. So I started to read about it a bit (finding this sight on the way) and developing ideas for my project. After reading a whole lot of information, opinions and sights (including linkwitz lab and music and design which I am still working my way through) and getting a few books, including the loudspeaker design cookbook, I am starting to develop a few ideas about the form that I want the system to take, but they still need a lot of development.

At the moment I have a lot of questions about the very basics of speakers & systems as well as sound in general and was wondering if someone could point me towards a book or website that thoroughly introduces all the basic concepts? I am picking it up slowly as I go along but I find that I am spending a lot of my effort trying to learn the basics rather than concentrating on what I am reading.

The speakers I am thinking about building are a bit of a hybrid. I mainly use our current (very basic package) system for home theatre but want any upgrade to be able to produce good sound for my partner who listens to a bit of music. After looking at a few PMS builds, I though I could adapt it a bit by reducing the height a bit but retaining or even increasing the volume by increasing the curve in the rear wall. This would be used as a closed box for sub-woofers and an open baffle would be formed by continuing the curved face of the sub-woofers upwards. The open baffle would be removable and I would make several of these to form all the surround speakers to keep everything consistent. To finish it a bit of marquetry in the veneer would be used to pretty them up.

While the woodworking will be a bit of a challenge, I should be able to do it without too much trouble. The speakers however I am realising are a completely different kettle of fish. I am not sure if I would be able to produce a good system, especially as it is my first attempt at something like this, so I am leaning towards taking an existing design and modifying the box/baffle parameters to meet this. For example, using Linkwitz’s Orion midrange and tweeter centre channel with the sides of the baffle extended and curved to align with the curved face of the woofer and then Linkwitz’s Thor as the basis of the woofer. Would adapting an existing system be a viable option or would it be better to take the time and start from scratch? If an existing system/design was to be used can anyone recommend one that would be appropriate?

As I am approaching this from the woodworking side any advice, suggestions comments etc would be greatly appreciated.

Thanks for reading

TJ

c2cthomas · 8th December 2007, 12:44 PM

Take a look at the MJK Ob design:
http://www.quarter-wave.com/General/OB_Design.pdf

There is a thread here at diyAudio with lots of good information. Panomaniac also has a nice design for OB, but seeing as you have stated that you want to do some surround sound I think that Martins design might be of interest as you could use the full range speakers in all locations and they would "voice" closely. I'm not sure about being able to do the surrounds as an OB design as they need to be set out from the walls (about 1 meter). You might consider something like Planet10's Fonkens for the surrounds.

tjthe1st · 20th December 2007, 05:09 AM

Thanks for the reply. I have gone through the OB Design.pdf again, but I am looking at going with either a active or PC based XO. Here is a quick sketch up of what they will look like, the dimensions are a little flexible at the moment. They are 450mm wide by about 1100mm total (600&500) high, with the woofer enclosure about 40ish litres volume at the moment (this could easily increase) and they have approval to go inside (which was the first major hurdle).

After a bit more reading/learning I will probably use different surround speakers not sure of what sort of design yet though. The centre speaker is also a bit of a dilemma, with a baffle as big as these there won’t be much room for the screen, maybe a virtual one would be appropriate?

Now I have to decide what drivers I will use, but after much reading I realise this is probably a bit beyond my abilities at the moment. Can anyone suggest any pre-existing designs that I would adapt well to this design?

8th December 2007, 08:12 AM	#1
tjthe1st diyAudio Member Join Date: Oct 2007	Beginner question/s OB Hi all I’ll start of by introducing myself. I live in Canberra at the moment, though I move around a fair bit with my job. After seeing my dad build himself a set of loudspeakers a few years ago I thought “I could do that” as I have done a reasonable amount of woodworking in the past. So I started to read about it a bit (finding this sight on the way) and developing ideas for my project. After reading a whole lot of information, opinions and sights (including linkwitz lab and music and design which I am still working my way through) and getting a few books, including the loudspeaker design cookbook, I am starting to develop a few ideas about the form that I want the system to take, but they still need a lot of development. At the moment I have a lot of questions about the very basics of speakers & systems as well as sound in general and was wondering if someone could point me towards a book or website that thoroughly introduces all the basic concepts? I am picking it up slowly as I go along but I find that I am spending a lot of my effort trying to learn the basics rather than concentrating on what I am reading. The speakers I am thinking about building are a bit of a hybrid. I mainly use our current (very basic package) system for home theatre but want any upgrade to be able to produce good sound for my partner who listens to a bit of music. After looking at a few PMS builds, I though I could adapt it a bit by reducing the height a bit but retaining or even increasing the volume by increasing the curve in the rear wall. This would be used as a closed box for sub-woofers and an open baffle would be formed by continuing the curved face of the sub-woofers upwards. The open baffle would be removable and I would make several of these to form all the surround speakers to keep everything consistent. To finish it a bit of marquetry in the veneer would be used to pretty them up. While the woodworking will be a bit of a challenge, I should be able to do it without too much trouble. The speakers however I am realising are a completely different kettle of fish. I am not sure if I would be able to produce a good system, especially as it is my first attempt at something like this, so I am leaning towards taking an existing design and modifying the box/baffle parameters to meet this. For example, using Linkwitz’s Orion midrange and tweeter centre channel with the sides of the baffle extended and curved to align with the curved face of the woofer and then Linkwitz’s Thor as the basis of the woofer. Would adapting an existing system be a viable option or would it be better to take the time and start from scratch? If an existing system/design was to be used can anyone recommend one that would be appropriate? As I am approaching this from the woodworking side any advice, suggestions comments etc would be greatly appreciated. Thanks for reading TJ

8th December 2007, 12:44 PM	#2
c2cthomas 49 - for the 17th time diyAudio Member Join Date: Oct 2006 Location: Near "Music City" (Nashville Tennessee)	Take a look at the MJK Ob design: http://www.quarter-wave.com/General/OB_Design.pdf There is a thread here at diyAudio with lots of good information. Panomaniac also has a nice design for OB, but seeing as you have stated that you want to do some surround sound I think that Martins design might be of interest as you could use the full range speakers in all locations and they would "voice" closely. I'm not sure about being able to do the surrounds as an OB design as they need to be set out from the walls (about 1 meter). You might consider something like Planet10's Fonkens for the surrounds. __________________ DIY audio can be expensive – but getting to see things go up in smoke - that's priceless!!!! ..... "whatever - call it brainfart of Mighty ZM"

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20th December 2007, 05:09 AM	#3
tjthe1st diyAudio Member Join Date: Oct 2007	Thanks for the reply. I have gone through the OB Design.pdf again, but I am looking at going with either a active or PC based XO. Here is a quick sketch up of what they will look like, the dimensions are a little flexible at the moment. They are 450mm wide by about 1100mm total (600&500) high, with the woofer enclosure about 40ish litres volume at the moment (this could easily increase) and they have approval to go inside (which was the first major hurdle). After a bit more reading/learning I will probably use different surround speakers not sure of what sort of design yet though. The centre speaker is also a bit of a dilemma, with a baffle as big as these there won’t be much room for the screen, maybe a virtual one would be appropriate? Now I have to decide what drivers I will use, but after much reading I realise this is probably a bit beyond my abilities at the moment. Can anyone suggest any pre-existing designs that I would adapt well to this design?