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Multi-Way Conventional loudspeakers with crossovers

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Old 18th December 2004, 09:21 PM   #1
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Join Date: Dec 2002
Location: Utah
Default Integrated 27-32 TV center channel

Hello everyone,

I have designed a unique home theater center channel speaker to solve a problem that I had. My problem was that when I started building a home theater projector the only wall space that I had to shine the picture was on the same wall as the regular TV. I had the TV up somewhat higher than usual on a custom A/V rack that I had made. I found a way to lower the TV by putting it on a lower table and moving the A/V rack over on the adjacent wall. The A/V rack now has to hold the HTPC and there was now no room to put the center channel speaker except on the floor beneath the TV. It did not look good and could not go on top of the TV because of needed that space free for the wall image.

I came up with this design and although this picture is just the conceptual design I have finished the speaker except for some cosmetic cover for the front which I may leave off.

Here is a photo of the design. It is built to high end standards in the real speaker. This just shows the outer shape. I post the picture in case you are having the same problem and this gives you an idea.

If anyone is interested I will work up a set of plans for minimal cost.

Hezz
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File Type: jpg tv pedestal speaker assembly3.jpg (14.6 KB, 159 views)
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Old 18th December 2004, 09:27 PM   #2
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Here is the snapshot from more of the side. The front baffle is sloped back to angle the sound towards the listener to compensate for the fact that it is so close to the ground. I stripped the componets from my DIY madisound Vifa center channel and because the back of the enclosure is so close to the wall I have made the enclosure an aperiodic one instead of a reflex design. This is better for vocals anyway as deep bass is not so important in a center channel but high transient response.

I'm too lazy right now to go get some 35 mm film developed to disc and I don't have a digital camera so pictures may come later. If anyone would like plans I can work them up for a few dollars.

Hezz
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File Type: jpg tv pedestal speaker assembly4.jpg (12.3 KB, 121 views)
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Old 18th December 2004, 09:32 PM   #3
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I have an opinion on this design, and for a few dollars I'll share it with you
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Old 18th December 2004, 11:11 PM   #4
morbo is offline morbo  Canada
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Just a tip - if you aim to sell these plans to people, you may want to give some details, ie measurements, drivers used etc. This is the second time someone has come on here trying to sell plans for a speaker with few details beyond a box with driver cutouts in it. I can't speak for anyone else, but if I'm going to spend money for plans I'd like an idea of driver/crossover cost. Does this use the same drivers/crossover from the madisound Vifa kit?

From your rendering, I'd consider making the actual 'speaker' part flush with the top and bottom platforms. Also, I take it you have an unobstructed path from this speaker to your ears (ie no coffee tables, etc)?
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Old 19th December 2004, 02:30 AM   #5
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Morbo,

I'm not trying to sell anything I am mearly making information available for a negligable fee for those who might want such plans because they feel they do not have the resources or knowledge to design this themselves. This is a DIY forum and I am not required to post detailed information on the speaker. I am not a commercial manufacturer not do I have acess to speaker test equipment.

Diffraction issues were considered and the design could be improved somewhat by making the whole face flush but I modelled that and did not like the looks of the speaker that way. Other people have to accept the looks of the speaker and so I made this consession. I will remind you that some very high end speakers seem to depart from defraction concerns in favor of styling.

One thing seems obvious after listening though and that is that having the speaker in the appropriate Di'appolito vertical configuration improves the sound significantly over the usual laying the speaker in the horizontal orientation.

There is no furniture between the listener and the speaker. I have the model that I built up and running and I am pleased with it's performance. At first I had it too heavily overstuffed but once I got the fill amount right it started to sing.


Yes. it uses the modisound Vifa center channel speakers and drivers. The drivers are 16 ohm 5.25 mid-bass units and the tweeter a metal dome. I can't remember if titanium or aluminum. I can get you the exact model numbers if you wish but this cabinet could work with many drivers as bass tuning is not of the utmost concern.

The dimensions are such that it should work with about any 5.25 MTM combination as long as the speaker frames are close to normal diameters. As a center channel speaker and aperiodically damped and not expected to dig down into the depths of bass the driver choices are less critical for the size cabinet. This speaker has a slightly larger volume than the original Madisound plans which allow the drivers to sound a little more relexed.

Sound quality is sufficient to easily hear recording and mixing differences when watching over the air broadcast television. Which most cheap center channel speakers do not easily resolve. In fact, in my opinion it is not a good idea to have too high of resolution for center channel speakers for watching braodcast TV. As a lot of the sound is not that well recorded.

In my opinion critically damped speakers in sealed or aperiodic enclosures are the best for a speaker who's primary role is to reproduce the vocal range.

Hezz
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Old 19th December 2004, 03:17 AM   #6
tiroth is offline tiroth  United States
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Hezz,

Your ideas are certainly appreciated. I guess some people are just put off by your statement, because we can tell from looking at the image how such a design could be built. In order to be of monetary (not just creative) value, the design itself (drivers, xover, enclosure time alignment) would have to be unique or refined in some way: that's where the subtlety would lie and where plans would be crucial. Otherwise, anyone can adapt the basic idea to pretty much any design. (For which inspiration I thank you)

One question I had was what difference it makes that the tweeter is likely a significant distance lower than the tweeters on the mains. A TMM would likely help here.
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Old 19th December 2004, 06:18 PM   #7
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Tiroth,

what you say is true, and my assumption is that most DIY speaker builders would just view this as a conceptual idea. But some on the forum are new to speaker building and may not have tools and may just want a set of cheap drawings to give to a friend to help them build the cabinets. I was only trying to be helpful. The amount I had in mind would hardly even account for my time in putting together the plans.

The tweeter on top idea is certainly a good one but there were two reasons that I stayed with this configuration. One is that the crossover was built with the speakers in this orientation and changing the positions could have a small negative impact on the sound. The second has to do with the diffraction issues at the top of the cabinet which I felt would effect the treble frequencies more adversely than the lower ones.

In auditioning the speaker I feel that it performs better than the original Madisound cabinet placed horizontally but higher up and closer to ear level. As I sit on my viewing position on the couch the axis of the speaker is pointed straight at me with nothing in between. The previous placement actually had more diffraction issues because of the second shelf position it was in and the gap at the space between the top of the speaker and the bottom of the top shelf.

I feel that the lower tweeter placement is not such of high concern for a center chanel speaker because of it's role in only playing the vocal range. There are not as many complex high frequency overtones going on in the vocal range as there is with music. In fact, the low placement is beneficial in that the floor reflection is somewhat damped by the carpet which effects the higher frequencies more than the mid and low ones. It has the effect of reducing sibulance in the sound which can be particularly probliematic with metal domes and low quality PCM recordings.



Hezz
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Old 19th December 2004, 09:00 PM   #8
morbo is offline morbo  Canada
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Looks like a nice project Hezz, glad it worked well for you.

Quote:
This is a DIY forum and I am not required to post detailed information on the speaker. I am not a commercial manufacturer not do I have acess to speaker test equipment.
Not at all, I was merely suggesting that IF you are planning on selling them, it would help. Sorry if my earlier comment came off as insistent, that was not my intention at all, merely a suggestion. I think that its because this is a DIY forum that you got the comments you did, we all share our projects, and "if you want to know details you'll have to pay" is not something that most people around here are used to hearing. Of course you are free to manage information about your project as you please.

I have also built an aperiodic design and I have to admit I'm very fond of its sound in the mid-low bass. I have not tried aperiodic for a center channel, but I imagine it would work very well.
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Old 19th December 2004, 09:17 PM   #9
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Morbo,

I am glad to hear that you have had success with an aperiodic design. It is not my intention to sell this speaker and if it were I indeed would need to supply more information about it. I well understand the sharing of info on these forums and am glad to share any of my ideas that I post here free of charge. But sometimes people want plans of things and a detailed workup of the plans requires more of my time than I am willing to provide at no cost. Though I am willing to help the neophyte for very little.

I had forgotten to mention that when I originally built the Madisound center channel speaker that I built a deeper enclosure than the plans called for and this new design is even a little bigger than that. So I have to revise my statement about the new enclosure volume being a little larger than the original Madisound design. It actually is probably nearly twice the volume.

I havn't had time to get the tuning really dialed in but it is sufficient for this application.

Hezz
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