Dayton RS225S-8 Transmission Line

[BillH]

It's time to build more speakers! I need a pair of speakers to provide the low end for an upcoming DIY hybrid ESL system. The crossover to the ESLs will be about 200Hz with the option to go higher if necessary. The drivers are here and the MDF is on sawhorses in the garage. It's time to trade computer design tools for the table saw.

Why the 8" Daytons? Reasonable price, low distortion, and I could get an acceptable response curve in Martin King's TL worksheets. Why not a larger driver? It would make the enclosure larger than I was willing to go and I'm not after maximum SPL.

Until the ESLs are done, the TLs will replace a pair of 12" N-pole speakers I've been using with 8" 3-way DIY open baffles.

Since starting the design, the driving factor was keeping the height of the enclosure as short as reasonably possible. Ultimately, there's going to be a 36" tall ESL panel on top of the TL and I didn't want the center of that to be too much above ear level when listening.

Here's a rendering of the design with one side removed:
Actual dimensions are 21-3/8" high, 13-1/2" wide, and 20-1/2" deep. The vertical dowel is an idea I had to stiffen up the panels. I'm not sure if it is necessary with 3/4" MDF.

[BillH]

There's two removeable panels in the back so I can adjust the stuffing with the driver in place and the cavity at the top opposite the driver will be used to house the ESL eletronics. The cavity ended up as a result of the driver position along the line. In order to tame some of the response ripples around 200-300Hz, I had to shorten the line about 4" from my initial design. Not wanting to refigure the entire geometry of the line, I left the cavity.

Final line length is 76-3/4" with the driver positioned 17-3/4" from the closed end and .4 lbs/cu ft. of stuffing. The line tapers from 2.033 to .910 Sd.

Here's the predicted response from MJK's TL Sections worksheet:

Edit: Fixed wrong dimension

[demon2091tb]

Looks to be very intresting, Any possibility that you have a design for the 8" Dayton Ref with ports on the front of the box....Looks like it will sound very nice with those ESL's.

I'm still trying to come up with a usable design that will sound really nice and not cost an arm and a leg, this may be a good choice for a 3way with some dayton gear.

Anyway looks to be nice. Let us know how it sounds.

[BillH]

demon2091tb
Bassbox Pro suggests this as an optimal vented enclosure:

Vb: 1.856 cu. ft. (Corrected for driver and stuffing volume)
Fb: 28.98 Hz
F3: 31.87 Hz
Vent Diameter: 3"
Vent Length: 9.24"

The on and off axis frequency response favors a crossover of about 1.5 KHz or lower. That should work for a 3-way.

Here's the predicted frequency response:

[BillH]

One of the RS drivers died. I was exercising them both last night with a 6 volt, 15 Hz sine wave and one driver had a scratchy sound, like a bad connection somewhere. After I determined that my test setup was not at fault, I shut everything down. 6 volts at 15 Hz is only about 2.4 watts, so I figured it wasn't blown from too much power.

This morning when I checked the resistance of the voice coil, it came up as infinity, dead, a deceased woofer...

I made a call to PartsExpress this morning and have an RMA for a replacement driver. Their tech, Mike thought one of the tinsel leads came disconnected internally. He said that when the driver is returned, the techs will tear the driver apart to find out what went wrong.

Here's a picture of the two of them before they had to be separated:

[BillH]

The MDF is cut. I used a 4' x 8' sheet of 3/4" for everything but the corner angles. The angles are cut from a 2' x 2' piece of 1/2" MDF.

Here's the enclosure parts and Rio, our Golden Retriever:

[BillH]

The first enclosure is finished and I've been listening to it with one of my 3-way open baffle speakers. The transmission line integrates quite well with the open baffle and any crossover point between about 200 and 700 Hz sounds good.

With .33lb/cu ft. stuffing:

[BillH]

In a word, my first impression is 'solid'. Full and low bass with no boom. Not a kick you in the chest kind of brute force, but when the bassist plays the low E I'm hearing it loud and clear. That's with the enclosures about 8' from the back wall and 4' from the nearest side wall with the enclosure raised up 12" from the floor.

My favorite auditioning CD is Little Feat - The Last Record Album. "Long Distance Love" off the CD is a good test for a speaker's bottom end.

After using Martin J. King's worksheets, I knew I wanted to try stuffing in the range of .25 to .4 lb/cu. ft. The goal was to get the first impedance peak flattened out and give a listen after that. In the picture below,taken from Speaker workshop , .25 lb/cu. ft. wasn't enough, .33 lb/cu. ft. flattened the peak, and .4 lb/cu. ft. flattened it more. Notice the ripples above resonance flattening out, too with more stuffing. I went with .33 lb/cu. ft. for the first listening.

[BillH]

Here's a look at the predicted and measured frequency response and system impedance.

First is a graph of driver and terminus predicted frequency response from MJK's TL Sections worksheet. Under it is the measured nearfield frequency response done with a soundcard FFT application. You can clearly see the dips and peaks in the terminus' measured response just as predicted. There is a frequency shift of the dips and peaks on the measured response that I can't explain. I need to measure the RS225S-8 to see if it is close to the values I used for simulation.

The bottom two graphs show the system impedance modeled with TL Sections and under it, the measured impedance from Speaker workshop.

Edit: the lowest frequency of the first graph should read 30, not 10.

[viki_v2]

Originally Posted by BillH

Here's a look at the predicted and measured frequency response and system impedance.

First is a graph of driver and terminus predicted frequency response from MJK's TL Sections worksheet. Under it is the measured nearfield frequency response done with a soundcard FFT application. You can clearly see the dips and peaks in the terminus' measured response just as predicted. There is a frequency shift of the dips and peaks on the measured response that I can't explain. I need to measure the RS225S-8 to see if it is close to the values I used for simulation.

The bottom two graphs show the system impedance modeled with TL Sections and under it, the measured impedance from Speaker workshop.

Edit: the lowest frequency of the first graph should read 30, not 10.

Hello,
Nice Subwoofer , Can you share details of this sproject I would like to Make one for me.