Tb W4-657 Rlh

[brsanko]

Hey guys let me know what you think of this RLH design. If I'm doing something totally wrong please let me know. Thanks

[brsanko]

HERE'S MORE INFO.

[brsanko]

Here's the specs on the driver.

[brsanko]

perhaps this pic is a bit clearer.

[fwater]

I'm not a horn expert (always learning), so I can't make too much of a comment on the design. I can say, though, that it looks like the ultimate in simplicity, go ahead and build a prototype out of MDF and hear the results.

What I can comment on is the x-o layout. For starters, if R1 and C2 are a Zobel, they need to be placed last in the signal chain, immediately before the driver. Plus, if you're going to roll off the top end at 700Hz, a Zobel will not be needed. Second, you have your high and low pass labels reversed (I'm a nitpick, I know). Third, IMO a highpass for this driver is completely unnecessary. A highpass network in this application would be prohibitively expensive, not to mention what it might do to phase. If you're wary of overexcursion, don't be. IME, this driver can handle quite a bit of cone movement (in a standard bass reflex) before the onset of any audible disortion. Lastly, it's a shame to use this driver as just a bass unit. I love the sound of this thing run up as high as 8KHz, rolled off with a simple coil, and handing off the top end to a tiny Dayton Neo with a single cap and resistor. I tried a few different x-o combos with these drivers, and I can say that experimentation will give many different levels of satisfying results. It will be a matter of your taste to determine final values.

I say, build it, and try running the TB way higher than you planned.

BTW, I'm in White Bear Lake. We should audition each other's creations...

[brsanko]

the high pass and low pass are not reversed. I have a high pass at 700Hz because the Bass response from the horn is almost 20db higher than the direct output from the driver, and the low pass is in place to use the response all the way down to 35hz or so that is above the 88db of the driver. If I only included the highpas the bass would be attenuated below 70hz where as the combination of the filters should give good response from below 40hz all the way up to 16khz making this a very wide range speaker. I wasn't sure where to put the zobel though, so thank you.

[fwater]

I've never seen it worked out like that. Help me understand- a highpass at 700Hz will pass everything above that point; you'll be (mathematically) 48dB down around 40Hz. A lowpass at 35Hz will pass everyting below that point; you'll be 48dB down at 550Hz. From my understanding, no output below 40Hz and no output above 500Hz will equal essentially no output at all. Explain how it works (I'm not being condiscending, if there's something I'm missing, I want to know).

Are you trying to roll of extra output below a certain point, like a shelving network? If so, a 50uf cap in parallel with a 15 ohm resistor, inserted into the positive leg before the Zobel, would be a good place to start (-10dB @ 70Hz and down, -5dB @ 200Hz, all-pass @ 1KHz). Increase the value of the cap to lower the cutoff points, increase the resistance for greater attenuation.

Without first building the cab, you can't know for sure what the bass output will be. Take it from a guy who used to obsolutely live and die by the numbers. I've been dissapointed so many times by slaving over modelling programs off all different types, building the enclosure or x-o, and finding out the hard way that these programs are tools to help get a person in the neighborhood of what will happen... in-room, with tolerances and numerous other variables. My most successful designs are approached step-by-step. If I were in your shoes, I would build the cab out of cheap material first. Make the CC purposefully oversized and add & subtract mass (wood blocks, tennis balls are nice), line & stuff different areas of the throat, make the curved deflector at the bottom removeable to see if it has an impact on the amount of midbass coming from the mouth, and consider a suprabaffle. After a few different combinations are experienced, then start implementing a shelving network. Hell, even inserting the tweeter has an impact on perceived low frequency output. The journey can be tedious, but it's more rewarding than spending north of $100 in x-o equipment that might not be necessary and you'll be too temped to use. Buff out the sound, then go for the nice wood (or not), and proudly announce your accomplishments.

BTW, your profile (I thought) previousely said you were in River Falls. Cloquet isn't exactly close to White Bear.

[brsanko]

I lived in River Falls till February I then I moved back to Cloquet. Actually with the 12db per octave high pass at 700Hz I'll be down 24db down at 175Hz, with the low pass at 60Hz (not 35 like you said) I'll be down 24db at 240Hz. The two circuits are run parallel not series, with the middle being 107.5 hz down about 20 db which is right where I need it. The slopes combine with the output from the front of the driver and the output of the horn (180 degrees out of phase because it's coming out the back and reflecting off the wall) to form a relitively flat response from 40hz up to 16khz. All theoretic of course but figuring is fun. Obviously I plan to build the box and make tweeks and adjustments before measuring the actual response so as to correctly design the filter, but I just wanted to see what was possible and check with some of the experts here and see if I'm calculating correctly in the first place or if I was doing something way off. The biggest question I have is whether the response out of the horn will really be way up at 110db. It seems unlikely to me but I don't know, I just learning this stuff. the two rear loaded horn systems my friend and I built this summer from plans we found on the internet sound amazing and I wanted to come up with a design of my own to possibly sell so I'm working it out in my head right now because I don't have money to actually make anything at the moment.

[brsanko]

I just realized that if the horn shifts the phase and then the filter shifts it as well I should probably have the horn come out the front. I think I should have put a more attention grabbing title on this thread.

[brsanko]

Considering my new theory regarding phase I redesigned the horn and like this one much better and it gets really similar results.