What drivers should go in this kickin' 60's console??

[Paul C]

Here is the thread where I discussed use of piezo tweeters. On the second page are the results.

http://audiokarma.org/forums/showthread.php?t=79659

And here is the predicted bass response with the 4 cft cabinet tuned to 31 hz (4" dia x 5.5" long port).

Pretty impressive, huh?

 

[macaltec]

Here is the thread where I discussed use of piezo tweeters. On the second page are the results.

http://audiokarma.org/forums/showthread.php?t=79659

And here is the predicted bass response with the 4 cft cabinet tuned to 31 hz (4" dia x 5.5" long port).

Pretty impressive, huh?

I think I need a bigger box.

 

[Urizen]

Urizen,

Great idea. I saw a pair on CL about a year ago and was so intrigued that I almost got them, despite being nearly an hour away. Damn me for not being a compulsive pack rat! Would they work in this volume cabinet, or are they not that fussy regarding the enclosure volume?.

Find some good old triaxials and use the cabinets like the old Dynaco A25 design. Mesh the top opening and stuff with fiberfill until the bass response sounds good.

Btw, that is one of the best looking consoles I have seen. :thmbsp:

 

[ashnut]

Okay, more questions:

So the efficiency of the tweeter is ~95 or so db. Is the port increasing the efficiency of the lower register, in effect raising the 92 dB rating of the Dayton woofer to roughly match the tweeter? If so, I'm following you. If not, why not consider the more efficient woofer, like the Pioneer here?

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=290-105

Would considering a different brand woofer change the synergy of the sound between the two drivers? the only difference I'm seeing is the Dayton goes down to 28 hz vs. 30 with the Pioneer.

And would you recommend putting anything in the cabs, like additional damping material, or does that increase the "volume" further? I'm assuming calculations were made assuming a basically undamped enclosure.

Thanks for the help, guys. This is fun!

 

[Paul C]

No, porting in itself does not raise efficiency of a given woofer in a given box. That is a myth, a misinterpretation of a statement by Theile about certain alignments.

To explain, for a given size box a woofer that would have the characteristics that allowed it to perform with the best bass extension would be about 6 db more efficient than a DIFFERENT woofer that would have characteristcs that would allow maximum bass extension in the same size sealed box. So, this was a comparison of two different woofers. The woofer has the same SPL regardless. The box it is put in, and the whether sealed or ported, affect the low end response, not overall SPL.

The port only increases output in the region of the tuning frequency of the port. It raises the region where the output is rolling off and merely extends the bass a little further.

First, we already know that this woofer (Dayton 295-320) and tweeter work well together, from Macaltec's experience, in boxes in this size range.

The Dayton woofer gives much more extended bass in the same cabinet than the Pioneer, down to a very respectable 31 hz vs 44 hz for the Pioneer. And I think the Dayton's rubber surround and treated cone make for a longer lasting woofer. Both woofers are about the same price.

Pioneer 12"

vs

Dayton 12"

You can't look just at the fs (woofer resonance) alone to compare the low end. You have to consider how each woofer will react in that particular cabinet. There are OTHER woofer characteristics that cause the woofer to roll off before speaker resonance.

You will notice that they have different tuning frequencies. What would happen, you might ask, if you used the same 31 hz tuning freqency with the Pioneer? Good question. But what I did was manipulate tuning frequency to give the flattest response.

I would add some damping to the back, 2 layers (about 2") of Poly fiberfill batting and on the undamped side panel as well. Don't worry about putting anything under the top panel. You can just buy a bag of poly fiberfill batting and staple it in place.

 

[Paul C]

Now look at the Pioneer 12 with the 31 hz port tuning (same as the Dayton 12's port tuning):

I am sure you would agree the higher port tuning gave a better bass response for the Pioneer woofer.

I just wanted to show that in the previous post, I had used the best port tuning for each woofer in that particular box size.

It would also be reasonable to ask, what if I just crank up the bass knob? (or use some EQ boost) with the Pioneer 12"?

With the 31 hz port tuning you would have to increase 6 db at 30 hz to match the performance of the Dayton 12" woofer. (With the 40 hz port tuning you would have to increase 9 db at 30 hz ) 6 db means you would have to quadruple power in the low bass. And that is right where the Pioneer is running out of Xmax. Its power handling is very low there. I did not show the power limit plot (but did take a look) so that it would not be confused with the frequency response curve. But the Pioneer is running out of gas down there even without any bass boost.

For the same money, the Dayton 12" gives a lot better bass performance even though it does have slighly lower SPL.

 

[ashnut]

I actually understand (mostly) what you're talking about. Excellent response, Paul. I'm glad I asked the question. I actually learned something.

Once again, proof that a little knowledge is a dangerous thing. Agreed, the Dayton is the better application for this project. Thanks so much!

 

[macaltec]

I actually understand (mostly) what you're talking about. Excellent response, Paul. I'm glad I asked the question. I actually learned something.

Once again, proof that a little knowledge is a dangerous thing. Agreed, the Dayton is the better application for this project. Thanks so much!

If you decide to go with the Dayton woofers and don't like it I'll buy them from you at your cost. In fact if you do this project with all of the components as laid out by Paul and don't like the results I'll buy all of it from you. How's that for some assurance?

 

[Paul C]

Wow! That's putting his money where his mouth is, quite literally!

I hope you understood my explanation of the "porting a speaker makes it 6 db more efficient" myth. This is so often repeated it is accepted as fact. It is true only if you use a different woofer!

Note that the Dayton's Xmax = 4.3 mm vs the Pioneer's Xmax = 2.4 mm. Xmax is how far the voice coil can move before it begins to travel out of the magnetic field gap. Beyond that amount of movement distortion rises, and eventually the voice coil will strike the back plate. The Dayton can travel further while remaining completely within the magnetic field, and react linearly. This is another thing that helps it be able to play louder before distortion sets in down in the bass range.

There are all kinds of things that to me just make this a better woofer.

And I have to tell you I have a thing against foam surrounds. They are a necessary evil. But if I can buy a woofer with a rubber surround, or better, cloth accordion surround rather than foam, I'll take those over a foam surround any day. My brother's old EPI 100's rubber surrounds look like they came out of the factory yesterday. But that's just me. I don't mind refoaming, but I really hate having to do it.

Agreed, the Dayton is the better application for this project. Right! And they even cost about the same. So that is not even a factor.

I had originally recommended another woofer (Eminence 12LFA) to Macaltec for his Santana project. But he came back with the Dayton. He had run this in one of the modeling programs himself and was impressed. I did the same, got the same results.

The more I looked for a reason not to use it, I just did not find one. Then when he assembled those components into his cabinets and came back with glowing reports, well I wrote back, got all the details, cabinet size, port tuning and made notes of all that in a folder. I plan on recommending this combination of parts quite often. I don't think you could build better for less $$$.

 

[macaltec]

Wow! That's putting his money where his mouth is, quite literally!

I am that pleased and continually impressed with the results. I cannot wait to try it out in a couple of different cabinets. My dad even has a pair of the Daytons that he is using in some Advent utility cabinets (sealed) and he likes them better than the original woofers. Now I'm curious about the 15" version :scratch2: .

 

[ashnut]

Okay,

So now that you've gone through all the trouble of figuring out this configuration, and explaining why it's good (I believe you). Let me ask what you guys think of this:

I may be able to get a set of Utah mid and high horns that would definitely stay with my 60's theme here. I'm sure your suggested setup will sound very good, if not great. But I'm drawn to these like so much of my other 60's and 70's gear. (It's a sickness.)

Would you steer clear and go with the modern setup, or go retro? Honestly, I'm a bit afraid of ending up with a poor sounding frankenspeaker. But on the other hand, if it sounded good, I'd feel like my 60's system is complete. Any advice to help me stay on track here?

Are there performance numbers for older, esoteric drivers (like Utah) that can be plugged into boxplot to put a little science behind a "vintage" DIY?

 

[macaltec]

Are there performance numbers for older, esoteric drivers (like Utah) that can be plugged into boxplot to put a little science behind a "vintage" DIY?

Excellent question. One I would like to know the answer to. If you can find the T/S parameters of those Utah drivers I see no reason for them to not work in Boxplot.

 

[Paul C]

I have had no luck finding T/S parameters on any 1960's woofers. They just did not do that back then. They would say vaguely "30 cps - 4000 cps" or something like that. Perhaps a power rating, and occasionally a box size suggestion. Porting? In those days that was done by trial and error, mostly error. You were advised to stick a tube in the cabinet that was as long as could be fitted. Then you sawed off an inch and listened. If it sounded better, you cut some more, and kept doing this until it was either just right, or losing bass. Then you tried again. And again.

With the Utahs, and other drivers, it would be retro, but you would be on your own as to how to build a crossover and the rest of it.

But consider, once you put in the drivers, close up the back, no one is going to see what is in the speaker, only the sound coming out. Also, with very old drivers like that, paper cones are fragile, surrounds stiff, corrosion and time has taken its toll. They could run for years, or quit next week.

I strongly suggest going with modern components.

----

Edit to add... the math for T/S numbers did not even come about until the 1970's. What I have not found is where anyone has analyzed older speakers to obtain T/S parameters. Even if they did, would they be valid today? Magnets weakened, surrounds stiffened over time?

 

[graywolf]

I have had no luck finding T/S parameters on any 1960's woofers. They just did not do that back then. They would say vaguely "30 cps - 4000 cps" or something like that. Perhaps a power rating, and occasionally a box size suggestion. Porting? In those days that was done by trial and error, mostly error. You were advised to stick a tube in the cabinet that was as long as could be fitted. Then you sawed off an inch and listened. If it sounded better, you cut some more, and kept doing this until it was either just right, or losing bass. Then you tried again. And again.

With the Utahs, and other drivers, it would be retro, but you would be on your own as to how to build a crossover and the rest of it.

But consider, once you put in the drivers, close up the back, no one is going to see what is in the speaker, only the sound coming out. Also, with very old drivers like that, paper cones are fragile, surrounds stiff, corrosion and time has taken its toll. They could run for years, or quit next week.

I strongly suggest going with modern components.

Presumably, one could measure the T/S specs for any driver with Speaker Workshop. The learning curve seems steep however. I hope to get it running eventually, but need to do a bunch more study before investing in the stuff I need to use it which seems can be as little as $20 or so, or as much as you are willing to invest, depending upon how accurate you want your results to be. You can download Speaker Workshop from: http://www.audua.com/

 

[ashnut]

Well, for an update, a year later. I did the upgrade, per Paul's instructions. I took a liberty in the design, and put in a -4db pad on the tweeter. While the sound is good, it never really grew on me.

So, a fellow AK'er set me up with the guts of a pair of Bozak Urbans. So once again, I'm calling for the wisdom of AK's finest. So here's the challenge: the original Bozaks had an internal volume of 8 cu. ft., and the cabinets in the console are 4 cu. ft. Now I was thinking of (1) fully stuffing the cabinets with acousta-fil and (2) using an aperiodic vent to lower the box Q value and increase the cabinet volume.

Any thoughts?

 

[macaltec]

If you decide to go with the Dayton woofers and don't like it I'll buy them from you at your cost. In fact if you do this project with all of the components as laid out by Paul and don't like the results I'll buy all of it from you. How's that for some assurance?

Well, for an update, a year later. I did the upgrade, per Paul's instructions. I took a liberty in the design, and put in a -4db pad on the tweeter. While the sound is good, it never really grew on me.

So, a fellow AK'er set me up with the guts of a pair of Bozak Urbans. So once again, I'm calling for the wisdom of AK's finest. So here's the challenge: the original Bozaks had an internal volume of 8 cu. ft., and the cabinets in the console are 4 cu. ft. Now I was thinking of (1) fully stuffing the cabinets with acousta-fil and (2) using an aperiodic vent to lower the box Q value and increase the cabinet volume.

Any thoughts?

Well I'll be damned! How much we talkin here ????? Kinda strapped right now.

*EDIT* It must be the distance between the drivers, yeah that's it. You need to get the left and right speakers farther apart .

 

[ashnut]

Well I'll be damned! How much we talkin here ????? Kinda strapped right now.

*EDIT* It must be the distance between the drivers, yeah that's it. You need to get the left and right speakers farther apart .

Hey, different sounds for different ears. I never had any intention of calling you on that, but thanks for keeping your bet in earnest.:thmbsp:

Besides, I've got someone interested in goofing with some of the parts. I said have at it. It was a fun learning experience. Who knows, I may end up going back to it. I've even thought the Dayton woofers may be a better application than the Bozaks for the LF driver. Mac, what do you think? Paul?

 

[Paul C]

Just saw this. You may have cut the tweeter too much with -4db cut.

Well, if determined to change it up again, your idea of stuffing the cab with the Bozak parts might work well. See how it works just stuffing the cab first, before adding the aperiodic vents.