DIY Music/HT Tower design

**mayhem13** · **03-28-08, 08:00 AM**

I've decided to take the plunge and build some front mains using fairly inexpensive drivers just in case i fail miserably. I'm looking at a high efficiency design for reference level listening during HT use. I would like to start with the low freq's first. I'm thinking two Dayton RS 8" 4 ohm woofers wired in series. Box volume will be around 100L and i'd like to rear port it with a 4" port all crossed at 130 hz. I plan on using 2 seperate front baffles so i can experiment with mid/highs as i go. Any comments or suggestions?

**Anthony** · **03-28-08, 08:37 AM**

First of all, let me congratulate you on an excellent name!

I like your approach of separate cabs, especially for a first project.

I have been working with the 8 Ohm version of that driver for my Open Baffle (OB) project for a while now. It is a fine driver if you don't push it too much.

I would look at 500 Hz as a crossover point. At 600 Hz and a shallow slope, you may get some nastiness from the breakup mode at either 1200 or 1800 Hz. It's one of those things that doesn't bother you until a note or voice hits it and then your ears feel unclean

The first time I ran these up to 1800 Hz directly to the tweeter (2 way). Sounded fantastic until some woman singing hit that note. I swear I heard cats and dogs crying outside afterwards.

At 500 Hz, you will avoid most of that, but it requires a 3 way design. Personally, I'd rather design a 3 way crossover than notch a breakup mode. Of course, once you start looking at the price of crossover parts, you almost want to buy a better woofer or tweeter that doesn't have breakup node problems. But that's only if you want to push it higher. For a 3 way design, this line of woofers is great.

But enough of the bad. These woofers are solidly built, look great, are pretty efficient, and have plenty of output for bass and mid-bass. With a well tuned port, they could even play full range. They have a good X-max (7mm) and good power handling.

I have only built open baffle and subwoofers, so I'm not an expert on box design, but hopefully someone here can run a few quick calcs for you to see what size you are looking at for different tunings.

In the meantime, check out FRD Consortium (google it) and their list of tools. You need Excel (preferably 2003, Office 2007 breaks some of the macros), but they are pretty easy to use for prototyping.

Good luck and keep us posted.

**BoomieMCT** · **03-28-08, 12:46 PM**

+1 on checking out the FRD Consortium. I'd also search for "Edge" (a baffle simulator).

**mayhem13** · **03-28-08, 08:15 PM**

Any suggestions for mid driver for these. For highs i'm thinking a 1" compression driver mounted to a 8" waveguide or adapt a titanium dome tweeter to the waveguide if the compression horn will be too much. I've been researching waveguide applications and there is a lot of positive results posted using quality 1" drivers stating excellent SQ at reference levels without any break up normally seen in commercial designed high freq tranducers.

**BoomieMCT** · **03-28-08, 08:47 PM**

Quote:

mayhem13 wrote:

Any suggestions for mid driver for these. For highs i'm thinking a 1" compression driver mounted to a 8" waveguide or adapt a titanium dome tweeter to the waveguide if the compression horn will be too much. I've been researching waveguide applications and there is a lot of positive results posted using quality 1" drivers stating excellent SQ at reference levels without any break up normally seen in commercial designed high freq tranducers.

I wounldn't know without testing but I'd look for something 3" - 5" with an efficiency around 92dB or a mid-dome. Something like two of the 5" Dayton reference series in series. There are some small pro-sound drivers that might work also (6.5" Eminence Alpha or Galaxy Audio 5" driver) but I don't know how "hi fi" they are.

If you are going three way you don't really need a compression driver with a waveguide. I see the main advantages of those as being efficiency, power handling and low crossover point usually at the expense of distortion and/or non-flat frequency response (there are exceptions).

**mayhem13** · **03-30-08, 08:13 AM**

I Like the idea of the coaxial drivers for mid-highs. Since it's been recommended to cross the woofers at 500hz, i'll start there with a radian 8" coaxial within a sealed chamber of the same box-possibly a 1/2 sphere mounted on top for creativity. From here i can experiment with compression drivers and x-over points. Maybe an active xover will teach me a thing or two.

**BoomieMCT** · **03-30-08, 09:55 AM**

You may need to use other woofers that play a tad higher w.out breakup but check this out.

**mayhem13** · **03-30-08, 06:33 PM**

I was really interested in that driver from the early stages but Zaph audio did some measurements and didn't like or recommend actually using it. PE says NEW so maybe it's been redesigned. Anyone have experience with this driver?

**mayhem13** · **04-01-08, 08:15 PM**

Back on the subject of the eminence coax's. I'm wondering if i could mount a 1" high sensitivity dome IN FRONT of the cone in it's own housing that tapers to about 1/2" through the center of the cone and thread it to screw into the 1 3/8-18 threaded mount. I have access to a lathe a making a mount out of aluminum wouldn't be too hard. The consensus seems to be that the cone movement adversely effects the output of the tweeter when mounted behind the cone. Any thoughts. I could by the tweeter and driver for leass than $100 so all would not be lost if it didn't work out but i'm still intrigued by the possibilities. I don't have any measuring capabilities but as a former live sound engineer i would like to think i have a trained and capable ear and something tells me that the right dome and xover point is gonna make a real charmer.

**BoomieMCT** · **04-01-08, 10:26 PM**

I'm having trouble imagining what you are describing. Can you draw a simple picture showing it?

**mayhem13** · **04-01-08, 11:40 PM**

Here's a quick drawing. This would thread in from the front of the cone and be attatched via threads in the magnet structure. The length would be determined by the mechanical depth of the threads plus allowing for 3mm cone excursion so draing is not to scale. I could turn this on a lathe using aluminum,plastic rod,acrylic,wood,etc.

horn adapter.jpg

**BoomieMCT** · **04-02-08, 05:23 AM**

Is this just to space the tweeter away from it's housing? I thought the possible issues arose because the cone acted as the tweeter's horn and it was moving.

**mayhem13** · **04-02-08, 06:04 AM**

Yes thats correct-the tweeter wil be flush with the face of the driver, thus removing the 'moving' horn effect yet still maintaining time alignment. Since the tweeters outside diameter is only 1.75 inches, do you forsee any problems with diffraction of the mids ? Will this act like a phase plug(i'm not sure what that does)?

**Anthony** · **04-02-08, 11:45 AM**

I am not sure of the acoustic effects, but you may want to verify that the pipe threading goes all the way through. Right now it's designed to be threaded from the back, the threads might not be cut all the way through the motor structure (which would be a requirement to screw something onto the front).

**zamboniman** · **04-02-08, 12:59 PM**

Quote:

mayhem13 wrote:

Yes thats correct-the tweeter wil be flush with the face of the driver, thus removing the 'moving' horn effect yet still maintaining time alignment. Since the tweeters outside diameter is only 1.75 inches, do you forsee any problems with diffraction of the mids ? Will this act like a phase plug(i'm not sure what that does)?

wouldn't this ruin the time alignment as well.... since the tweeter is physically and acoustically then out front of the acoustic center of the mid driver?

**mayhem13** · **04-02-08, 02:07 PM**

it won't be out in front by much-only a little more than an inch but more important i wont have a moving waveguide with this set up. in regards to the threaded question from anthony-it's not threaded all the way through but that won't be a problem-the threads are open ended so it can thread in from both ways. The only mod i'll have to make is cut out the screen dust cover.

**mayhem13** · **04-04-08, 08:37 PM**

Giving up on the Coax design-don't think those eminence drivers will have the SQ i'm looking for. I think i'll do an MTM design in a sealed configuration with dual subs below since i have 2 12" Dayton HFs from an abandoned project. Each sub will have a dedicated plate amp and drivers side mounted and tops crossed to 80hz for smooth integration. Subs will have the same foorprint as MTMs which would be mounted on top.Anyone build those Dr K's from part express-looks simple enough.

**BoomieMCT** · **04-04-08, 08:44 PM**

Quote:

mayhem13 wrote:

it won't be out in front by much-only a little more than an inch but more important i wont have a moving waveguide with this set up. in regards to the threaded question from anthony-it's not threaded all the way through but that won't be a problem-the threads are open ended so it can thread in from both ways. The only mod i'll have to make is cut out the screen dust cover.

Without that waveguide (moving or not) you couldn't cross as low as you could otherwise.

**mayhem13** · **04-04-08, 09:01 PM**

So you say stick with the coax's then?

**BoomieMCT** · **04-05-08, 08:58 AM**

Quote:

mayhem13 wrote:

So you say stick with the coax's then?

No, I was saying if you do use the coaxes then use their recommended mounting points.

Advertisement