Budget build results, SF-Dayton - diyAudio
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Old 14th October 2013, 05:57 PM   #1
tvrgeek is offline tvrgeek  United States
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Default Budget build results, SF-Dayton

I was prompted to report on a little budget build I just completed. I had several goals:
1: Gain further practical real vs. model experience with PSD Lite and HOLM
2: Show how well you can do with cheap best-in-class components keeping a simple (cheap) crossover
3: Prove why I build more expensive speakers

I believe I succeeded in all three.
First driver selected was the SilverFLute W19RC36-8. At under $40, this is a wool-paper cone and is much better than the price suggests. No, it is not a Iluminator beater. It has terrible break-up issues between 4 and 5K so top prevent a very complex (expensive) crossover, it should be used with a very low crossover.It has pretty smooth response and will go quite deep for a 6 inch driver. I set 1.5K, 3rd acoustic as a max. Ouch. Find a 1.5K tweeter cheap? Again, picking best in class, not the best I can find, I selected the Dayton DC28F-8. 1/18 soft dome. Highly respected for a $20 tweeter and is known to not be too terrible crossed over low. Things like the SB29 or a Morel were way out of the budget.

Box was done by odougbo. It is one of his curved sid-port jobs he has posted several times. I don't know how he can do this so well without measurement, but the alignment is dead on. F3 is in the low 60's measured. Like I said, the SF is a budget class leader.

The crossover I ended up with is a second order electrical. Not quite symmetrical. Woofer is a 3.3mH and 12uF. Q is about 1. Tweeter 15uF, .75mH with a 1 & 8 Ohm L Pad. Q came out about .78. I used the Jensen P-core for the big 3.3. Caps are standard Dayton poly. For a strict budget build, I see no reason not to use electro's. I happen to have the films. The films raised the price by over $20. Pick your budget. I doubt you could hear the difference in this application.

One meter on axis, MLS measurements are within a couple dB 100 through 15K. The cabinet does not have the large radius edges I prefer so it sounded a tad bright. I added felt doughnuts around the tweeters to tame them a tad.

Sound.
Well, for me they are a bit disappointing. BUT these are built for under $200 the pair. For the budget, they are actually pretty darn good. The produce REAL bass into the low 50's. The response is surprisingly flat. Imaging is very good. The distortion is just too high for me. Yes Virginia, there is a difference between a $20 tweeter and a $100 one.

Red is the tuned speaker before adding the felt ring. I did not measure after. I did not do any polar measurements. Blue was a test trace I happen to have saved in this jpg. I was not planning to post this, so excuse the graphic.

Conclusion:
Through the crossover region, HOLM is a super tool and it correlates well with listening. I think it correlates better than fast-chirp on TrueRTA. It matches ARTA, but I prefer it now. Of course, the bass response is best done outside with noise, not MLS. Not going to bother, sorry. I use my WooferTester to get the impedance plots.

Using PSD, one can very accurately model repeatable results that correlate with measurements. Great little tool. I still rely on ISD for my box design.

The best budget drivers are pretty good. Only that. No amount of fancy crossover or tuning can overcome the lack of copper pole shunts and basic motor shortcomings. For $200, not a bad build. I would do a conventional rear-ported MDF box with 3/4 inch roundovers on all 12 corners. I may still do that. It may still be a tad bright for some if played stand-alone. With a sub, the balance is not bad. You can always pad the tweeter some, but I found that messed up the crossover region too much. So that means adding a LR parallel filter. More money which puts it outside the project scope.

What else could be done? I have another woofer I got by mistake. I may try doping the cone to see if the breakup can be tamed enough to slide the crossover up over 2K. That would greatly reduce the tweeter distortion and allow a cheaper woofer coil. Maybe I'll play with that while my test blocks for how to hide MDF seams cure.

They will stay in my garage playing the FM until I cycle something else through there. I have not run out of nieces and nephews to overload with prototype speakers yet so they will find a home.
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Old 15th October 2013, 04:09 PM   #2
ODougbo is offline ODougbo  United States
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I did listen to these for about 15miuntes; thought TVR had a bit of a break-through - the woofer sounded great with the larger coil, and TVR also mentioned light on the damping material.
Please remember they are less than $30, and sound like drivers 2 - 3 times the price.

Links: The Madisound Speaker Store
The Madisound Speaker Store

The box are very compact and I do think the side flare ports are enhancing the bass; we'd have to make up some other boxes to compare.

The only drawback I see is that they don't work well at low volume, need to play them at a moderate level. This is less of a problem in the mtm boxes.
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Old 15th October 2013, 04:53 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

If you want a good cheap wide range speaker look no further than :
https://sites.google.com/site/undefinition/diy/amiga

Smaller this is pretty good at the price :
X-LS Classic kit

rgds, sreten.

Basic box design is so simple there is no need to use conjecture.
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When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 15th October 2013 at 04:58 PM.
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Old 16th October 2013, 02:08 PM   #4
ODougbo is offline ODougbo  United States
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Been to the GR site a few times, their pricing seems to be good.

Impressive write up on the X-LS Classic, all that for a mere $109, seems to good to be true.
Wish they had more reviews, e.g. 53 comments on this PE page:
Dayton Audio BR-1 6-1/2" 2-Way Bookshelf Monitor Speaker Kit 300-640

TVR, what about a light spray vanish coat on the SF's?
That ploy is used by a lot of manufactures.
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Old 16th October 2013, 04:44 PM   #5
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Did you try using an elliptical LP filter instead of crossing so low? Care to upload your project files?
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Old 16th October 2013, 10:23 PM   #6
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by dumptruck View Post
Did you try using an elliptical LP filter instead of crossing so low? Care to upload your project files?
Trying to make an elliptical filter hit dead on a resonance peak would be quite a trick. It would have to be tuned to each speaker. I think the Q of the notch is much higher than the Q of the breakup and I have no experience with the phase. I have never explored this with a passive filter.

I played with a wide variety of Q's. PSD lets you do that. I have no doubt higher-steeper filters and a notch would reduce the tweeter distortion. Making the very best crossover possible with these two drivers was not the goal. Simple and cheap was. We already learned this is a great cheap woofer IF you deal with the notch. The Dayton has a pretty solid rep for $20. I have used several other $20 tweeters in the past. The Dayton is way up there in the pack and the only one I know anything about that can be at all civil at 1500Hz.

I would love to see a competition here on under $200 (US)/pair total cost on a mid-size monitor with 60 Hz f3 and reasonable power handling. A speaker for the masses if you will. Could we beat Warfdales for the price? I bet a lot of first time builders would love to see it. Take this as a first shot. There is a lot of experience in this forum and I have no doubt I could be bested. Don't be surprised If I don't follow up as it is just not what interests me right now. Here is an idea: Dope the cone to lower the breakup up Q allowing a higher crossover. I was unable to match the responce with only one resistor in the tweeter pad. Can someone do better? ( Buck-fifty savings) Do the poly caps matter? ( a ten spot to be saved). FG rather than wool stuffing? Anther few bucks. That almost pays for $30 tweeters.

Still, this was a simple build using commonly available best-in-class (really cheap) drivers and demonstrated learning how well PSD matches measurements. I already concluded that for my use, I need to spend the bucks on drivers about two steps up. Seas tweets at about $50 and woofers in the 60 or so range. Crossovers need about twice the number of parts.

When I get to my lab PC, I'll grab the four measurement files and throw them up.
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Old 17th October 2013, 08:40 AM   #7
tvrgeek is offline tvrgeek  United States
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files. frd are 1M on axis, gated
HOLM measured on frd, WT-2 for zma.
Of course, ignore the bass in the frd. The bass alignment was done outside with TrueRTA chirp.
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Old 17th October 2013, 10:05 AM   #8
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by tvrgeek View Post
Trying to make an elliptical filter hit dead on a resonance peak would be quite a trick. It would have to be tuned to each speaker. I think the Q of the notch is much higher than the Q of the breakup and I have no experience with the phase. I have never explored this with a passive filter.
Hi,

Elliptical is not really that difficult approached properly,
see : Zaph|Audio also see his tests of the 4 ohm SF.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 17th October 2013 at 10:09 AM.
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Old 17th October 2013, 06:16 PM   #9
tvrgeek is offline tvrgeek  United States
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Quite familiar with Zaph's data. A most valuable place to start. Of course, one's own measurements and experience has to be added.

An elliptic is anything with a Q of much over 1.2 or so. Higher then Chebyshev. They are not really much use in low order filters and not common where linearity is important. Adding ripple to the pass band is not usually a help. If I remember correctly, Dick Small did a paper on them. I am not aware of any published successful designs using passive ones, and for sure, not second order. Note that the filter Q's are 1 and .78, so they already have some ripple. Play with the model if you wish, who knows what may be stumbled onto.
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Old 17th October 2013, 06:21 PM   #10
tvrgeek is offline tvrgeek  United States
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Where's my files? Ah, Invalid file.

OK I will rename them .txt. After download rename correctly as frd and zma
Attached Files
File Type: txt dc28frd.txt (43.0 KB, 14 views)
File Type: txt sffrd.txt (43.0 KB, 7 views)
File Type: txt SFzma.txt (5.4 KB, 4 views)
File Type: txt DC28zma.txt (5.4 KB, 7 views)
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