Surround speaker project

**GrahamT** · 04 November 2005, 20:04 Friday

Idea Generation

After researching, I believe that surround speakers would work best for meeting the objectives. I think the sound field would be more even and wide with bipoles rather than dipoles or quadpoles. I encourage any alternative solutions or ideas.

I have also found that there is VERY little information on designing surround speakers, let alone bipolar surround speakers. If anyone knows of a good source for this information let me know. I have read the HT speaker design section in the Cookbook.

Shown below are two proposals for the bipole surround speakers.

Image not available

I don’t know which design would better meet the objectives. I suspect the 90 degree bipole design is more complex, but I don’t know for sure. I am looking for comments regarding the pros and cons of each design. I also don’t know which design would have the best horizontal dispersion.

For the tweeters, an early candidate is the HiVi K1 tweeters (or maybe the X1), here is the info from HiVi: http://www.swanspeaker.com/product/htm/view.asp?id=30 . They seem pretty decent, and price is definitely right. I can get 4 of them for about $40 CDN. As, always I am interested in any other suggestions. The impedance seems smooth and even in the 3-4 kHz region.

These are some comments by John "Zaph" Krutke from www.Zaphaudio.com . I really enjoy reading John's tests and his speaker designs. I share many of his philosophies regarding speaker design.

Originally posted by Zaph

The Hi-Vi K1, while not a stand out performer by any means, is still a standout value. For $9 this is a great tweeter.

Hi-Vi K1 ($9) - Smooth response. Shielded magnet, rather large 116mm flange. Low Fs for a tweeter with no rear chamber and a solid pole piece. High F5 below 2.2khz. Average to slightly high IMD. (not shown) Cross LR4 @ 2.2kHz or LR2 @ 3kHz for best results. Decent performer in a garbage price range.

I am thinking of an LR2 or Butterworth2 crossover at about 3kHz. This will keep the crossover component count down. The 6.5" Paradigm poly driver's FR will likely be ragged by 3-4kHz, but I think it is fine considering this application and the objectives.
Of course, after measuring the midrange drivers I will have a better idea of which tweeters to choose and which filters will be appropriate.

I'm looking for any ideas, comments, references to similar projects of resources etc.
The time frame for the completion of this project is around February-March 2006 so I have lots of time to think through most of the process before anything is built. I plan to get the first measurements and T/S parameters of the Paradigm 6.5" drivers finished on November 12/2005.

Design Links

http://users.d-web.com/dbrown/htdesign/htdesign.htm

Page not found – Home Theater Mag

http://www.hometheatermag.com/loudspeakers/25/index.html

http://www.timn8er.com/aural_imaging_tb3_surround.htm

Sites-polk_us-Site

http://www.polkaudio.com/education/tech_article.php?id=27

Polk Audio

http://www.thx.com/mod/techlib/speakers.html
http://www.soundandvisionmag.com/article.asp?section_id=2&article_id=242&page_numbe r=4
http://72.14.203.104/search?q=cache:yOieylOEVGcJ:www.audioholics.com/techtips/specsformats/THXSelectUltracertificatio2.php+dipole+surround+sp eakers+design+thx&hl=en

**Bent** · 04 November 2005, 20:32 Friday

Graham, you seem to be well on your way - I'd only suggest to try to keep the option of operating them in bi pole or di-pole opreation. Achieved simply with a DPDT toggle on one half of the driver.

**GrahamT** · 04 November 2005, 20:51 Friday

Thanks Ben. Yeah that's true. I might as well include a DPDT switch.

The problem with dipoles for my application is that they would create a null area, so some people would be in the nulls and others wouldn't. But if I ever used them as side surrounds, I could aim the null areas at the listening positions.

**cinema bob** · 04 November 2005, 21:13 Friday

i am defiantly interested in this project because as you have said there is very little info available on surrounds. My vote is for the 90 degree version with the dpdt switch because a person could then build four identical speakers and use them for the four surround positions in a 7.1 or build three and use in a 6.1. They seem to be the most versatile design.

**GrahamT** · 04 November 2005, 21:40 Friday

Originally posted by cinema bob

i am defiantly interested in this project because as you have said there is very little info available on surrounds. My vote is for the 90 degree version with the dpdt switch because a person could then build four identical speakers and use them for the four surround positions in a 7.1 or build three and use in a 6.1. They seem to be the most versatile design.

Alright, that is definitely a possibility. I never thought of using them in a 6.1 or 7.1 system, and the di/bipole configuration with the DPDT switch would work out very well for those applications.

I would like to see if there are others interested also. There will be limited drivers available for this project though because I am in Canada, and because I would like to keep this project very affordable. I dont know what the budget is yet. That will depend on several factors.

This is the idea generation phase of the project, so keep 'em coming.

**Bent** · 04 November 2005, 22:02 Friday

I'm trying to avoid the suggestions I'm thinking of - to redesign my ADP-370s.

You could also consider a center mounted bass driver and the tweeters/6.5"ers on either side... but the x-overs would get ugly...

**GrahamT** · 04 November 2005, 22:16 Friday

Originally posted by Bent

I'm trying to avoid the suggestions I'm thinking of - to redesign my ADP-370s.

You could also consider a center mounted bass driver and the tweeters/6.5"ers on either side... but the x-overs would get ugly...

That's a coincidence. The ADP370 does have the same 6.5" drivers that I do. What dont you like about them? The dipole dispersion, the tweeter? I may stick with the Paradigm drivers. I'll consider all the options before deciding how to proceed on the project. There is plenty of time.

Your idea is very similar to the Paradigm Signature surround speakers. I had considered using a center mounted 8" bass driver, but you are right, the crossover gets more complicated than I want, and the cabinets get bigger. I am designing these to be crossed over at 100Hz anyway. I want to keep this affordable and within my abilities.

One option using other drivers to consider would be based on the HiVi M4n drivers. They are pretty cute I think...hmmmm

**cinema bob** · 04 November 2005, 22:24 Friday

i'm all for keeping this inexpensive. also i dont think that voice matching is crucial for surrounds. i like the ideas of the hi-vi m4n/k1 they seem to be budget performers.

**Bent** · 04 November 2005, 22:58 Friday

Actually I do very much like my ADP's, I can't say as much for my Mini's and CC-350 I have up front - not that I dislike the front three, I'm just tired of them. That's where part the funds will come from for my DIY's (insert name here, your Extremis based project is a front runner though).

**GrahamT** · 04 November 2005, 23:10 Friday

Originally posted by Bent

Actually I do very much like my ADP's, I can't say as much for my Mini's and CC-350 I have up front - not that I dislike the front three, I'm just tired of them. That's where part the funds will come from for my DIY's (insert name here, your Extremis based project is a front runner though).

I totally understand. I had the Paradigm CC370 and Monitor3s up front with Minis in the back. I suggest you sell them and use the money to fund DIY projects if you are tired of them. They have good resale value. Dont take them apart like I did (I'm in engineering so I take everything apart)

I cant say enough good things about the ExtremeMTs, I couldn't be happier with them, other than their current appearance of course.

**GrahamT** · 05 November 2005, 08:07 Saturday

Originally posted by cinema bob

i'm all for keeping this inexpensive. also i dont think that voice matching is crucial for surrounds. i like the ideas of the hi-vi m4n/k1 they seem to be budget performers.

I'll try to think of some more drivers that might work in this application. A simple solution would be to use CSS WR125s drivers wide range, but where's the fun in doing something simple. The HiVi's are inexpensive and available at www.PartsExpress.com , www.madisound.com , and www.solen.ca .

**Dennis H** · 05 November 2005, 10:33 Saturday

Graham, before you build new speakers (I assume you still have the cabinets), I'd play with placement of the ones you have. Monopoles can work well in tight quarters with a little fiddling. They should be outside all the listeners (wider) for starters and should be placed so no one gets direct sound from the tweeter but rather sound reflected off the walls and ceiling. I'd try them on the floor lying on their backs, close to the two chairs, so the chair backs block the direct sound. Or maybe up high, one in the corner and the other equally spaced the other way, both turned to bounce the sound off the wall and ceiling. The one in the corner will have more bass so it helps if your receiver has individual tone controls.

**GrahamT** · 05 November 2005, 11:20 Saturday

Originally posted by Dennis H

Graham, before you build new speakers (I assume you still have the cabinets), I'd play with placement of the ones you have. Monopoles can work well in tight quarters with a little fiddling. They should be outside all the listeners (wider) for starters and should be placed so no one gets direct sound from the tweeter but rather sound reflected off the walls and ceiling. I'd try them on the floor lying on their backs, close to the two chairs, so the chair backs block the direct sound. Or maybe up high, one in the corner and the other equally spaced the other way, both turned to bounce the sound off the wall and ceiling. The one in the corner will have more bass so it helps if your receiver has individual tone controls.

Hi Dennis,

I've had these speakers for years, and tried everything. Firing forward, firing up sideways, etc. The best location as you mentioned, was outside the listeners, one in the corner one equally spaced the other way, which is how I have them now. But with 5 listeners, the sound field isn't satisfactory unless you are in the middle. It is probably because the seats are against the wall.

Plus, I just want to build new speakers. :B

**GrahamT** · 05 November 2005, 18:55 Saturday

Another driver that I am considering is the Silver Flute W14, again Zaph really liked it, and the price is pretty easy to swallow.

My first choice is still the Paradigm midranges, but I havent made up my mind. I'll know more once I measure the 6.5" drivers.

**cinema bob** · 06 November 2005, 23:14 Sunday

my vote is still for the hi-vi's because I think that more people would be able to get in on the fun. myself included

**GrahamT** · 07 November 2005, 06:49 Monday

Yeah lets go with the HiVi M4ns, they seem as good a driver as any in the budget class. Unless you or any one else can think of a better budget driver from 80 Hz to 4 kHz.

Anybody have any comments on bipole design criteria, testing methods etc?

**morbo** · 07 November 2005, 14:49 Monday

Graham, I will watch this project with interest as I will soon build surrounds myself. I had planned to go with FR125 monopole, but thought that dipole might be better since I am in a very small room where the surrounds will be about 3-4 feet away from the oustide listeners. I think the simplest solution like you said would be a pair of FR125s in a bi/dipole, though that would be a bit pricey. A lower priced design using parts readily available in Canada would be great.

**GrahamT** · 07 November 2005, 15:20 Monday

Hi Jakub, hope things are well with you.

I'll order up some M4ns from Solen soon-ish, and probably the K1s aswell. I cant do any construction or measurements here at school, but I will have lots of time in about 5 weeks after finals. So until then I will keep researching, and planning out how I will design them. Try to get most of the work done in my head first, before I spend any money.

This is the order of things to get done first:

1. Decide on the box type for the di/bipoles. 180 degrees, 90 degrees or something inbetween. Then design the box using UniBox.

2. Plan out how to measure these speakers. I have an AutoCAD drawing of the planned measurement position, I'm still looking for feedback on that.

**Paul H** · 07 November 2005, 18:30 Monday

Originally posted by GrahamT

... 2. Plan out how to measure these speakers. I have an AutoCAD drawing of the planned measurement position, I'm still looking for feedback on that. ...

Graham,

Me and I suspect many others missed your drawing above as they appear black until clicked on.

I can't claim any specific knowledge for measuring bipoles, but your measuring position noted in the drawing makes sense. If you're eventually mounting them somewhat above the listening position (as many recommend), you may want to test them the same way (ie with the mic lower than the speaker).

Paul

**GrahamT** · 07 November 2005, 18:55 Monday

Originally posted by Paul H

Graham,

Me and I suspect many others missed your drawing above as they appear black until clicked on.

I can't claim any specific knowledge for measuring bipoles, but your measuring position noted in the drawing makes sense. If you're eventually mounting them somewhat above the listening position (as many recommend), you may want to test them the same way (ie with the mic lower than the speaker).

Paul

Thanks for letting me know, maybe it's the line weight in AutoCAD. Putting the mic lower than the speaker sounds like a good idea too, thanks again. I plan on mounting these 6 to 7 feet above the ground.

I'll try to attach a new measurement drawing with the new mic position below, this time with a white background, hope this works.

Image not available

**GrahamT** · 07 November 2005, 19:28 Monday

Also, any comments on box style is appreciated. My initial thought is to make a traditional box, which has drivers on opposite baffles as in the 180 degree bipole drawing above (I hope everyone can see it) because it would be the simplest design for most people to build. But if there are advantages to changing the angle of the baffles let me know.

I suspect that the baffles on most commercial dipoles are angled to control the size of the null area, or for aesthetics. But that is just a guess.

Here are some examples of the typical surround styles.

Paradigm Reference ADP (slightly less than 180 degrees)

Aperion (appears to be 90 degrees)

Paradigm ADP350 (180 degrees)

**GrahamT** · 09 November 2005, 08:26 Wednesday

I've decided to go with the 180 degree di/bipole. 180 degree dipoles are common, Paradigm has a few as do others. And 180 degree bipoles are used extensively by Def Tech. So I dont think there is any harm in going with the 180 degree di/bipole and the benefit of ease of construction is very important I think. Since I dont really have an algorithm for designing these, when I have to make a decision I will go with Occam's razor.

So I will do some preliminary box modelling when I get a chance in Unibox using the published T/S parameters. I will measure the actual drivers when I get them and make any needed changes if the specs are off. I dont think that will be much of an issue because these will be crossed over around 100 Hz.

Just a note, when designing a dipole enclosure, the drivers have to have seperate enclosures or there will be no bass.

The crossover design will be optimized for bipole use, but with the DPDT toggle it will be able to operate in dipole mode if required for the application.

**dawaro** · 09 November 2005, 17:43 Wednesday

You might want to take a look at Dave Brown's site. He has done some modeling based on driver placement and dispertion pattern. Might be helpful in what you are doing.

dB Site

**GrahamT** · 09 November 2005, 18:15 Wednesday

Thanks for the link David. I had seen that a while ago but totally forgot about it. Those are some interesting results. It also makes me think that the 180 degree di/bipole is probably the best compromise.

**GrahamT** · 09 November 2005, 19:17 Wednesday

I found this frequency response graph of some M&K dipole surround speakers. So using the measuring position posted above, I will try to aim for something similar.
If anyone finds some more links let me know and I will add them to my initial posts.

I think that this was measured at 1 meter, but with the mic in the position drawn in my first post.

**morbo** · 12 November 2005, 21:16 Saturday

One other thing that may be handy is taking a look at this thread:

http://www.audiocircle.com/circles/v...ic.php?t=10915

which details the design of Danny Richie's take on the 'diffuse' surround speaker. Even if the design isnt what you plan on, the process may be valuable.

**GrahamT** · 12 November 2005, 21:54 Saturday

Originally posted by morbo

One other thing that may be handy is taking a look at this thread:

http://www.audiocircle.com/circles/v...ic.php?t=10915

which details the design of Danny Richie's take on the 'diffuse' surround speaker. Even if the design isnt what you plan on, the process may be valuable.

Thanks a lot Jakub.

Actually, that is probably my favourite design so far. It would probably work great for my application. I think I might try to emulate that, which might mean changing drivers. I already have a pair of mids and titanium tweeters that might fit that application perfectly. In that case I would do two of those style firing up and two Minis way out on the sides. I have the tools to make those types of cuts. I also really like the idea of the 45 degree wall mount, that looks really secure.

Thanks again.

**morbo** · 13 November 2005, 18:47 Sunday

Hey no problem, I've been eyeing the design as well for some time, aesthetically its nearly perfect, looks like a little sconce, and I trust Danny to do make the right compromises in a surround speaker. As you may have noticed when researching it, there is little technical info on designing bi/dipole surround speakers out there, so even more so that usual, I feel more comfortable getting a design from someone who knows what they are doing in this case.

The only thing that kept me from jumping on the design is cutting the wierd angles... my woodworking skills are minimal and my tools limited to a router, jigsaw, and sander. I can see how I could use my chamfer bit to do a 45deg angle, but was never sure how I could do the 10 and 20 deg angles needed with any sort of precision. The nice thing is since there is no BSC in the design, I think I could do the same thing with just a FR125 in a sealed box, no filter, though that still leaves the odd angles.

**GrahamT** · 13 November 2005, 21:36 Sunday

Originally posted by morbo

The only thing that kept me from jumping on the design is cutting the wierd angles... my woodworking skills are minimal and my tools limited to a router, jigsaw, and sander. I can see how I could use my chamfer bit to do a 45deg angle, but was never sure how I could do the 10 and 20 deg angles needed with any sort of precision. The nice thing is since there is no BSC in the design, I think I could do the same thing with just a FR125 in a sealed box, no filter, though that still leaves the odd angles.

You can cut the weird angles accurately with the router. You can make a similar table to the one below out of plywood. It is only a very rough sketch, but I hope it gets the point across. You set the flush trim bit on the plunge router to cut flush with the table when then router base is sitting up on the rails. You could use it for future projects too.

Image not available

The FR125s would be nice, but I would personally go with the WR125s since it is a fair amount cheaper, and it already has good HF extension as you know.

**GrahamT** · 13 November 2005, 21:42 Sunday

These are the drivers I am going to use. They are a 8" Paradigm midranges with LPG 26T tweeters. The tweeter voice coils were centered using the technique Jon posted.

Image not available

Image not available

They are both good quality drivers. The Paradigms are poly cones with a cast aluminum basket. The LPGs use a double magnet stack, almost as large as the Paradigm 8" driver.

These surround will work well with some of the other speakers I use which all have titanium tweeters. Now I will have a timbre matched rear sound field with Minis out on the sides and these in back. So it will be a 6.1 system.

Image not available

Image not available

I made these out of MDF with red oak veneer and Krylon Make it Stone. So I would make the surrounds to match with these.

**Dennis H** · 13 November 2005, 22:11 Sunday

Other than the looks, there is no need for fancy angles. You'll get the same sound with a rectangular box that aims the drivers at the ceiling. The main difference between Danny's surround and one of his regular speakers is no baffle step compensation in the surround's crossover because it's designed to be wall mounted. One of the small PE enclosures with an FR125 aimed at the ceiling should work fine. No need for any XO componenents because the baffle step is taken care of with the wall mounting.

**GrahamT** · 14 November 2005, 17:14 Monday

Thanks Dennis. I think I will still go with the angled box. The boxes will be fairly large with 8" drivers, so the angles might help with aesthetics. I'm going to completely paint the boxes with the Krylon Make it Stone, like in the above pictures. Cheap and quick.

**morbo** · 14 November 2005, 18:12 Monday

Thanks Dennis, I am going to try to avoid the curves, I will either go with a simple rectangular box or a laminated compound curve that more closely resemble a 'traditional' sconce. Most likely I will paint them with the same paint as the walls.

One thing I noted is that Danny said in his thread that he aimed for a response that tilted upwards gradually to from about 2khz +5d at 20khz, 2khz seems a bit high for just the normal design without BSC, and being that the FR125 has a naturally rising bottom end, along with a rolled off response on the top end (in terms of power response, not on axis, where it is flat), I wonder if the FR will be balanced like it should...

**KeithM** · 14 November 2005, 18:16 Monday

sorry for asking a dumb question, but where can you buy raw paradigm drivers?

**GrahamT** · 14 November 2005, 20:02 Monday

Originally posted by KeithM

sorry for asking a dumb question, but where can you buy raw paradigm drivers?

Not a dumb question at all, the drivers can be hard to find unless you know where to look.

You can get raw Paradigm drivers from the larger Paradigm dealers who are also parts distributors. For example, in Toronto you can get them from Kromer Radio, at the parts dept.

**Bent** · 14 November 2005, 20:10 Monday

Funny Graham. I just thought you were really hard on enclosures - :ROTF

**Dennis H** · 14 November 2005, 20:35 Monday

About the high end response, the jury is still out. Lexicon, by default (it's adjustable), rolls off the surround highs starting at 7kHz. A fullrange driver, like the FR125, aimed at the ceiling, would probably have a similar rolloff. Maybe it needs fixing with some passive EQ and maybe it doesn't.

**GrahamT** · 20 November 2005, 12:00 Sunday

I think this is how I will build the surrounds. They will likely be the sixth channel in a 6.1 system. Or I might do a poor man's 7.1. I also might experiment by by having both surrounds hooked up to the sixth channel, but out of phase. I dont know how it would sound, but I'll try it and see what happens.

Image not available

They will be built out of good quality ply. I'm tired of MDF dust getting everywhere. That is a 3/4" roundover on the edges. The baffle is perpendicular to the wall.

The dimensions are approximate. I need to measure the the T/S specs first.

Speaking of measurements, I need a new mic. I am trying to decide between the Apex 220 and the Behringer ECM8000. http://apexelectronics.com/index.php?tmp=4&id=83

Page not found | Behringer

http://www.behringer.com/ECM8000/index.cfm?lang=ENG

The page you're looking for doesn't exist or has been moved.

I'm probably going to get the ECM8000. The Apex is cheaper, but I cant find very much info on it.

**cinema bob** · 20 November 2005, 20:20 Sunday

i guess im not really sure what you are gaining over the paradigms that you had. if you just pointed them skyward you would be right where you will be, if you go to the trouble of designing and building this new enclosure.

**GrahamT** · 20 November 2005, 20:44 Sunday

Originally posted by cinema bob

i guess im not really sure what you are gaining over the paradigms that you had. if you just pointed them skyward you would be right where you will be, if you go to the trouble of designing and building this new enclosure.

I'm still using the Minis as side surrounds, but these are going to be used as rear surrounds. So I will be using 4 surround speakers in a 6.1 or 7.1 system. And the only cost is for the new crossovers.

Cost was quite a concern for me since I'm trying to pay my own way through engineering. I chose this design because it achieves the objectives, and for the least amount of money by far.

**GrahamT** · 20 November 2005, 22:24 Sunday

Hey Bob,

If you still want some cheap DIY di/bipole surrounds, you can use the CSS WR125 16 ohm drivers in parallel. All you need are the drivers, input cups and the DPDT switch, no need for a crossover. They will dig pretty deep too if you want to use a low crossover on your BM.

That would be the route I would have gone if I didn't want more experience designing crossovers.

You can get them for $50 each from here: http://www.diycable.com/main/product...89c6fd3de4dbcc

They would end up being cheaper and probably sound better than the HiVi speakers I proposed.

**GrahamT** · 20 November 2005, 22:36 Sunday

I'm currently leaning towards going back to original idea which was using the Paradigm drivers and HiVi tweeters in a bipole configuration. I probably wont make up my mind until I have to start cutting wood. :P

They will probably be made after I build a new center channel.

Surround speaker project

Surround speaker project

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