Dayton Twin Towers

[Thumper Tom]

Re: Dayton Twin Towers

Did some scaling off your pics.
Looks like the tweeter/mid distance is about 7-1/2", setting THAT Fc near 1.8kHz, which is about the limit for the -070 "Silky". You could have gotten down to more like 4-1/2" (using the truncated "Silky - which I think was going for $12) which would have let you use a lot more of the mid-dome's range, up to about 3kHz.

Larger problem is that the dome mid shouldn't go below 500Hz (that dome should "ideally" cover 3 octaves - which you'd know if . . . , 500 to 4000 Hz would be sweet, but you'd need a smaller faceplate tweeter).

Your distance down from the center of the mid-dome to you lower woofer looks to be almost 19". 13,500ips / 19in = 700 cps.
So your mid needs to run from 500 to 1800 Hz.

Also, most boxes (today) are deeper than wide. Personally, I'd have turned your box "sideways" so it was 10"w x 14"d. That way you'd have 4 more inches available for port length. Dual 8's really beg for a 4"dia. port (like Dave Tennie's "Dayton 8's"). Looks like even a 7" long vent could barely fit in there w/out an elbow. Also, I figure your volume at under 2.4 cf, which is pretty small for vented dual 8s. You'd have ended up with 2.9 cf if you hadn't triple-baffled.

The crossover is the Dayton XO3W-500/4000 http://www.parts-express.com/pe/show...number=260-152, so my center to center should be 3.375 in. Currently my center to center is 7.5 inches, so over double. I have not read the book SpeakerBuilding 201, so what is going to be the big disadvantage of not having the center to center set at 3.375 in?

[Chris Roemer]

Re: Dayton Twin Towers

That dog won't hunt (I've always wanted to say that).

That stock "textbook" XO won't hardly work at all (they almost never do).

Cross pts with your drivers end up near 400Hz (with bad phase issues) and both the tweeter AND mid running concurrently betwee 4kHz and 6kHz. This is particularly bad given your driver spacing.

The woofer doesn't rolloff nicely and the mid runs from 400Hz (bad) up to 6kHz. The response ends up about 90dB +/-3dB above 400Hz. There's almost no baffle step compensation.

I've designed you a custom XO that crosses near 500Hz and 2k. The woofers roll off nicely, and mid and tweeter levels are matched. It ends up about 87dB +/-1dB, with +4dB of baffle step built in. Did I tell you that you need a 4"id x 10" long vent for that box?

I can email you pics if you care to PM me your address.

Chris

[johnastockman]

Re: Dayton Twin Towers

Oh, I wasn't aware that you were going to use the pre-made XO, which completely changes this whole discussion. Unfortunately, and I'm sorry to say this, but you will not be able to use that XO; yes, it'll pass the signal, but it is extremely inadequate for any application and especially this one. You need to use the XO that was designed for those 3 drivers. The main issue with using the pre-made XOs is they assume the driver is a constant 4 or 8 ohms. That is never the case, as the impedance varies with frequency. And varying impedance is only one of the many factors that must be taken into account. If the impedance is not 4/8 ohms at your cross-point, the XO's stated cross-frequency(s) will be way off and the driver won't be crossing where it should or where you want it to. A driver won't be a fixed 4 or 8 ohms (which is what the pre-made XO part values are calculated for) at the XO frequency. It could be 12, 15 or even 20 ohms. You can see right there why using a fixed number for a number that is constantly varying is a recipe for a lousy SQ reproduction. I tried for many years (before I found this forum over 12 years back) to get all manner of pre-made and fixed number algebra-calculated XOs to work properly...they never did and always left me frustrated as to why I wasn't getting something I could stand to listen to for more than a minute. What I got was harshness, a much too forward/shouty midrange, unclear & muddy highs, and no imaging or balance between the drivers frequency response. "The numbers are adding up, but I can't get a decent SQ..." was my initial questions when I came here looking for answers. The answer was that you cannot use a fixed-number for one that is variable. I can get the XO diagram for you, and I think it's archived also. Even though you'll be going TMM instead of MTM, using the XO that was designed specifically for those drivers will be light years beyond what that pre-made XO will provide. Everyone here will tell you the same thing: don't use pre-made XOs (for the same reasons I outlined above). I feel bad having to tell you this, as I know you've already got the stuff and are this far along with the project...I should not have assumed myself that you were using the original D8 XO. There's that assume thing again. :o But if you want a SQ that you can enjoy listening to, which is the reason for doing all this, you'll need to use the XO that was designed for that exact driver compliment. Anything else and you're cheating yourself and your ears out of some great listening pleasure. I'm sure Chris will advise the same AFA the pre-made XO. So let's start from there and you can tell us where you're at with this. Again, much apologies for my assumptions.


John A.


PS I see that Chris has come up with a XO that was designed for this app. Use that one definitely!

[Thumper Tom]

Re: Dayton Twin Towers

Did not want to Frankenstein the boxes but I think I have a way to get the tweeter and mids closer together but will have to use a lot of bondo. We will see how it goes tomorrow.

[Chris Roemer]

Re: Dayton Twin Towers

If you use MY XO, you don't have to screw with the driver layout.
Right now your biggest problem is the stock Dayton XO.
2nd biggest problem is getting a proper vent in there.

[Thumper Tom]

Re: Dayton Twin Towers

If you use MY XO, you don't have to screw with the driver layout.
Right now your biggest problem is the stock Dayton XO.
2nd biggest problem is getting a proper vent in there.

Sounds good, did you get my PM?

[Chris Roemer]

Re: Dayton Twin Towers

Ygm

[Thumper Tom]

Re: Dayton Twin Towers

Ygm

Here is the layout of the new crossover that Chris designed, thanks a lot, should have the parts on Wednesday.

[Chris Roemer]

Re: Dayton Twin Towers

Your schematic looks correct to me!

[Thumper Tom]

Re: Dayton Twin Towers

Thanks for the crossover Chris, and here is a little update:

Layout of the crossover:



Underside:



Sound Testing:



SQ wise needs a little work but I think with a little bit more play time the speakers with sound a lot better.

As for movie watching they work really well, watched Inception last night in stereo, and I think my dad will be very impressed.

All I need to do is disassemble, sand, seal, and paint. Hope to have it all done by Friday. :D

[Chris Roemer]

Re: Dayton Twin Towers

I'm going to look over the XO pretty well, but I trust you wired it all up properly. The sim showed the parallel woofers AND mid to have normal polarity (+ to + / - to -), with only the tweeter wired "reverse". That's how you showed it on your schematic. Just a reminder.

Other thing I noticed is that you've really got a lot of "stuff" out in front of these, not the tweeters really, but the woofers & mids, esp. the mid on the left. Those boxes out in front probably aren't helping anything (like "imaging"). I'd even recess the PC to get it behind the baffle, if you can.

And you DO have them lined, don't you?

[kevinr]

Re: Dayton Twin Towers

Could this crossover be changed to work with only one Dayton Classic 8 woofer instead of 2 per cabinet ?
I'd really like to add the Classic Dayton Mid to my Dayton Eight

[Wolf]

Re: Dayton Twin Towers

Wayne Jaeschke's 'Lyra' is what you're after.
Wolf

[Thumper Tom]

Re: Dayton Twin Towers

I'm going to look over the XO pretty well, but I trust you wired it all up properly. The sim showed the parallel woofers AND mid to have normal polarity (+ to + / - to -), with only the tweeter wired "reverse". That's how you showed it on your schematic. Just a reminder.

Other thing I noticed is that you've really got a lot of "stuff" out in front of these, not the tweeters really, but the woofers & mids, esp. the mid on the left. Those boxes out in front probably aren't helping anything (like "imaging"). I'd even recess the PC to get it behind the baffle, if you can.

And you DO have them lined, don't you?

Everything is wired up the way we had it listed in the schematics. If you look at the tweeter terminal I went ahead and wired a red wire for the positive but on the underside it is soldered to the negative and vise versa with the black wire.

The boxes are lined with pollyfil and some recycled cotton insulation, and the sub boxes to the left do have a good effect on the sound but I mainly wanted to make sure the crossovers were working correctly.

[kevinr]

Re: Dayton Twin Towers

Thanks for the tip on Wayne's 10 inch Classic 3 way Lyra project Wolf...... but I already built the Dayton 8 project which uses the classic 8 like Thumper Tom's twin towers.
I found all the information on line about the Lyra's but could not find the enclosure and crossover data for them .
I wondered if I could adjust Chris R's crossover for Tom by changing the coil and cap for one woofer instead of two 8's. I like the Dayton 8's but would really like to listen to them as a 3 way and also move them out of the sealed .90 cu. ft. enclosure to a larger vented cabinet