I have finally finished my Humble Homemade Optimo project: http://www.humblehomemadehifi.com/Optimo.html
The sound is not great - slightly closed in and none of the fantastic midrange that I had expected. I have realised that I need to tune the tramsmission line by changing the amount of stuffing. This appears to be quite a technical issue.
On Tony's website he says to completely fill the first half. In an email from Tony, he said to lighly fill the first half.
The line is 172cm2 x 190cm long.
Initially, I have put a piece of BAF in the first half of the line that is 1000mm x 500mm x 40mm. It weighs 6 Oz (170g).
I have read somewhere (Weems) that TL stuffing should be 8 Oz (227g) per cubic foot (28317 cm3).
Have I put far too much in?
Can you help explain my temporary dissapointment?
I will write a thread with some nice photos once I have got this right.
The sound is not great - slightly closed in and none of the fantastic midrange that I had expected. I have realised that I need to tune the tramsmission line by changing the amount of stuffing. This appears to be quite a technical issue.
On Tony's website he says to completely fill the first half. In an email from Tony, he said to lighly fill the first half.
The line is 172cm2 x 190cm long.
Initially, I have put a piece of BAF in the first half of the line that is 1000mm x 500mm x 40mm. It weighs 6 Oz (170g).
I have read somewhere (Weems) that TL stuffing should be 8 Oz (227g) per cubic foot (28317 cm3).
Have I put far too much in?
Can you help explain my temporary dissapointment?
I will write a thread with some nice photos once I have got this right.
Hi,
http://www.quarter-wave.com/TLs/Alignment_Tables.pdf
See pages 37 onwards in particular.
FWIW I'd suggest lining the 1st 1/4 or so of the TL with high quality
acoustic foam, as you would with a vented box, and then adjusting
the stuffing denstity and length for bass response versus bass ripple.
(Possibly also foam line just the outside front, bottom
and back of the U shaped fold of the line, YMMV.)
IMF used to foam line what can be considered the "back" of the line.
/sreten.
http://www.quarter-wave.com/TLs/Alignment_Tables.pdf
See pages 37 onwards in particular.
FWIW I'd suggest lining the 1st 1/4 or so of the TL with high quality
acoustic foam, as you would with a vented box, and then adjusting
the stuffing denstity and length for bass response versus bass ripple.
(Possibly also foam line just the outside front, bottom
and back of the U shaped fold of the line, YMMV.)
IMF used to foam line what can be considered the "back" of the line.
An externally hosted image should be here but it was not working when we last tested it.
/sreten.Thanks Sreten: I had obviously read a few of Martin's papers, but I had not come across this bit.
Prior to your post, I had just purchased some accoustic egg crate foam to try behind and above the drivers, though I was not planning on much more.
I am now playing the Optimos without any stuffing at all, and the closed in or dead sound has gone. I am now going to fill the first half of the line with torn chunks of BAF which will result in less density.
I will bear in mind your suggestion of placing further foam along the bottom of the U bend. What do you expect this to achieve?
Prior to your post, I had just purchased some accoustic egg crate foam to try behind and above the drivers, though I was not planning on much more.
I am now playing the Optimos without any stuffing at all, and the closed in or dead sound has gone. I am now going to fill the first half of the line with torn chunks of BAF which will result in less density.
I will bear in mind your suggestion of placing further foam along the bottom of the U bend. What do you expect this to achieve?
I have optimo's and they sound great. Of course I used top quality components for the crossover.
I had problem with bass. After some discussion with Tony, he suggested I use sheep wool, IIRC. It was a long time ago, I don't remember what my problem was exactly.
It sounds super now. I can tell you that even with expensive (several kEUR) player and amps, the speakers are the best components in my system.
I had problem with bass. After some discussion with Tony, he suggested I use sheep wool, IIRC. It was a long time ago, I don't remember what my problem was exactly.
It sounds super now. I can tell you that even with expensive (several kEUR) player and amps, the speakers are the best components in my system.
You can see my crossover on Tony's site. I think I used Mundorfs supreme all over. For the series cap for the tweeter, I started with a mix of Mcaps/Mcap Zn and Supreme. Later I threw out the normal caps and replaced them with Mcap supreme silveroil.
This really was a real worthwhile improvement. The highs were muchg better after the change. Normal Mcaps should be avoided at all cost. They don't belong in speakers like optimo's.
I don't think that resistor make much of a difference although I didn't try in crossover (but I do use those expensive naked vishays everywhere else where they do make a difference, hmm). I used mox10 I believe.
The coils should be aircore. I think I used tritec and flatband. It would not explain your problem.
My advice is that you double and triple check your crossover. The optimo's excel in a very open and transperant midrange and of course super highs. The bass is on par with other systems, but should be deep, tight and punchy with good amps and possibly some experimentation with the stuffing.
Unless you use the best of amps and sources, this speaker should not hold your system back.
Unless you use it in a large space of course. There is only so much that a 18cm woofer can do. But it goes easily down to 35 Hz in my home.
BTW. did you use the scanspeak ring radiator?
This really was a real worthwhile improvement. The highs were muchg better after the change. Normal Mcaps should be avoided at all cost. They don't belong in speakers like optimo's.
I don't think that resistor make much of a difference although I didn't try in crossover (but I do use those expensive naked vishays everywhere else where they do make a difference, hmm). I used mox10 I believe.
The coils should be aircore. I think I used tritec and flatband. It would not explain your problem.
My advice is that you double and triple check your crossover. The optimo's excel in a very open and transperant midrange and of course super highs. The bass is on par with other systems, but should be deep, tight and punchy with good amps and possibly some experimentation with the stuffing.
Unless you use the best of amps and sources, this speaker should not hold your system back.
Unless you use it in a large space of course. There is only so much that a 18cm woofer can do. But it goes easily down to 35 Hz in my home.
BTW. did you use the scanspeak ring radiator?
Hello ABO - Thanks for your reply.
I think that I will change the 10uf MCaps for MCap Supremes @ 36EUR each at some stage soon. This is what Tony's high-end version suggests. The Silver Oil ones are 93EUR each!
Yes, I did use the R2904/7000 ring radiator.
I will let you all know how the tuning goes when I had recieved the egg crate foam (I dont want to loosen the self tappers by too many changes).
I think that I will change the 10uf MCaps for MCap Supremes @ 36EUR each at some stage soon. This is what Tony's high-end version suggests. The Silver Oil ones are 93EUR each!
Yes, I did use the R2904/7000 ring radiator.
I will let you all know how the tuning goes when I had recieved the egg crate foam (I dont want to loosen the self tappers by too many changes).
Hmmmmmm!
Take a look at the first attachment ("Optimo 1"). This is how the Optimo TL as designed models with Martin King's Mathcad-based TL worksheets. Those big dips and peaks sure look they would sound ugly. This SS 18W/4531G00 works (models) much better in an ML-TQWT and I modeled one of the same length that could fit within the same box dimensions. Its modeled response is shown in the second attachment ("Optimo 2"). It's obvious the overall respnse is very smooth and F3 is several Hz lower. You can also get a good result in a tapered TL with this driver but the box would need to be larger for the same F3.
Take a look at the first attachment ("Optimo 1"). This is how the Optimo TL as designed models with Martin King's Mathcad-based TL worksheets. Those big dips and peaks sure look they would sound ugly. This SS 18W/4531G00 works (models) much better in an ML-TQWT and I modeled one of the same length that could fit within the same box dimensions. Its modeled response is shown in the second attachment ("Optimo 2"). It's obvious the overall respnse is very smooth and F3 is several Hz lower. You can also get a good result in a tapered TL with this driver but the box would need to be larger for the same F3.
Attachments
Oh my, that looks ugly.
It begs the question as to why a respected designer (and several very happy builders) have been highly satisfied with this formulae/design.
See thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=107201&highlight=humble+optimo
As I said in the previopus thread, we must respect ear over modelling sometimes, and attempt to understand why there are differences.
I am open minded.
It begs the question as to why a respected designer (and several very happy builders) have been highly satisfied with this formulae/design.
See thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=107201&highlight=humble+optimo
As I said in the previopus thread, we must respect ear over modelling sometimes, and attempt to understand why there are differences.
I am open minded.
dublin78 said:
I would call Tony Gee an experienced based designer, i.e. he has much experience and built a lot. Most speakers sound reasonable, but somewhat biassed to the taste of the builder. If you have a similar taste, than you could be very happy with his designs.
If you are looking for something more neutral sounding and more universal applicable, look elsewhere.
I must say that I've only heard a few designs of him, all of them showed this characteristic.
dublin78 said:
Yes, it does look really ugly and just about any constant cross-section TL will have a similarly ugly response unless the line is heavily stuffed. But when you do stuff that line heavily, there is no bass contribution from the terminus, and other than preventing all reflections back through the driver, using the TL loading becomes virtually meaningless IMO.
I did read all of the thread you linked, which I hadn't read before, and I see both Planet10 and Scottmoose saw how poorly the line in the Optimo performs long before I did. All of their comments regarding the deficiencies in the design and the experiments that led to it really hit the "nail on the head".
I have no intent of poo-pooing the respect many people have for Tony's work or Tony himself, but I've also seen a number of negative comments about some of his projects. From my viewpoint he seems to "throw" very expensive drivers and, perhaps also expensive crossover components, at virtually every design, which won't guarantee good or excellent sound if the enclosure and/or crossover design aren't optimized. And, that was my main point; the TL design in the Optimo is far from good, much less "optimum". I appreciate you being open-minded, but one shouldn't dimiss or ignore easily demonstrated problems or deficiencies in a design, especially when spending hard-earned money. Why does the Optimo seem to sound good to a number of people who've built it? Can't answer that or know what/how other people hear. In the end, I agree that it's how good a speaker sounds to the builder/listener that counts, but I'd have a hard time justifying or recommending building a design whose performance I could demonstrate would be poor just because it came from a "respected" designer and others said it sounded good.
I need to add...
Why did you start this thread in the first place? Because your Optimos didn't sound good. So, you asked Tony how much stuffing you should use, and he changes that to an amount different from what he says on his website (and neither amount is clearly defined, I might add). Why did he change and what amount did he really use to decide the Optimo sounded good (to him)? There's really no need to guess at how much stuffing is needed and where to locate it; this can easily be determined by modeling before generating one speck of sawdust.
Have you considered the possibility that your Optimos don't sound good because you're hearing the negative effects of those huge dips and peaks in the response that are really there? Maybe your ears are just plain better than Tony's (or other Optimo builders), or whatever good things you are hearing aren't good enough to allow you to ignore the bad things.
Although I've been reading on this site for quite some time, I just started posting here a couple of days ago and I don't want to be perceived as a trouble-causer or "flame"-starter. So, unless you or someone else has a specific question/comment or two directed at me, I think it would be best for this to be my last post in this thread.
dublin78 said:
Why did you start this thread in the first place? Because your Optimos didn't sound good. So, you asked Tony how much stuffing you should use, and he changes that to an amount different from what he says on his website (and neither amount is clearly defined, I might add). Why did he change and what amount did he really use to decide the Optimo sounded good (to him)? There's really no need to guess at how much stuffing is needed and where to locate it; this can easily be determined by modeling before generating one speck of sawdust.
Have you considered the possibility that your Optimos don't sound good because you're hearing the negative effects of those huge dips and peaks in the response that are really there? Maybe your ears are just plain better than Tony's (or other Optimo builders), or whatever good things you are hearing aren't good enough to allow you to ignore the bad things.
Although I've been reading on this site for quite some time, I just started posting here a couple of days ago and I don't want to be perceived as a trouble-causer or "flame"-starter. So, unless you or someone else has a specific question/comment or two directed at me, I think it would be best for this to be my last post in this thread.
I am no speaker builder and I don't really understand loudspeaker design. But I can tell you how the optimo's started.
I bought the drivers to be used in another kit design. I won't name the designer. I build the kit expecting a lot from it. Unfortunately my expectations were let down because the design sounded crappy, with no midrange and slow bass.
I then turned to Tony whom I only knew from his website. He turned out to be a very friendly and helpful guy and he was willing to help me out. So I send him the driver for him to experiment with.
From what I've come to know from him, he is definately not an EE. But he is a very experienced builder and designer and the designs that he showed me all sounded very good to my humble ears. He seems to clearly understand the sonic impact of any changes he makes.
I can only say that the new design he came up with, the optimo's, sounded much better than the original kit. To me, it was a pleasant surprise when Tony first demonstrated the proto's to me. I couldn't have hoped for a better result. I cannot determine how neutral they are, but I can't hear any obvious faults in the response.
I have yet to hear a better midrange in a two way speaker. The bass gave my some problems in the beginning, but they were easily solved when I started using sheep's wool instead of BAF. I don't know what the differences are between these stuffings. Perhaps someone else can explain the differences.
That's all from me. I am more into electronics really.
Thanks,
Abo
For now, and some years to come, I am happy with the Optimo's and an not considering to change my speakers any time soon.
I bought the drivers to be used in another kit design. I won't name the designer. I build the kit expecting a lot from it. Unfortunately my expectations were let down because the design sounded crappy, with no midrange and slow bass.
I then turned to Tony whom I only knew from his website. He turned out to be a very friendly and helpful guy and he was willing to help me out. So I send him the driver for him to experiment with.
From what I've come to know from him, he is definately not an EE. But he is a very experienced builder and designer and the designs that he showed me all sounded very good to my humble ears. He seems to clearly understand the sonic impact of any changes he makes.
I can only say that the new design he came up with, the optimo's, sounded much better than the original kit. To me, it was a pleasant surprise when Tony first demonstrated the proto's to me. I couldn't have hoped for a better result. I cannot determine how neutral they are, but I can't hear any obvious faults in the response.
I have yet to hear a better midrange in a two way speaker. The bass gave my some problems in the beginning, but they were easily solved when I started using sheep's wool instead of BAF. I don't know what the differences are between these stuffings. Perhaps someone else can explain the differences.
That's all from me. I am more into electronics really.
Thanks,
Abo
For now, and some years to come, I am happy with the Optimo's and an not considering to change my speakers any time soon.
Yes
Tony gave me this info before I had completed the build, so he was not reacting to a complaint.
Absolutely - It is very depressing.
I have spent a lot of time and money on these cabs, and they look stunning (even if I say so myself). I just want to get a good result. I am prepared to build new cabs, but as a last resort. Frankly, this has got me questioning my ears, my gear, my crossover wiring, the lot. Again, very depressing.
I have even considered asking ABO to try my crossover with his Optimos, just to make sure there is nothing wrong with them.
I am very willing to try anything. Please give me details.
Thank you all for your help.
Your input is useful. We are here to learn
An ML-TL
In trying to modify the Optimo cabinet once it's built, it's not at all practical, maybe even impossible, to make a good ML-TL. Yes, you could block off the current large terminus opening and replace it with a port located either there or somewhere down the back of the cabinet. But the primary problem is the location of the woofer; it's way too close to the beginning of the line, which causes a big dip in the response between 100 and 200 Hz or so. Secondly, the current line is too long for an ML-TL to have both a good bass response and an overall smooth response above 200 Hz. Now if the woofer and tweeter locations were reversed, the woofer location would then be much closer to optimum, even with the existing line length, for an ML-TL. Finally, I've modeled ML-TLs for this specific driver for potential personal use, and I've found a line length of 60-65 inches much, much better, as compared to this line with its ~77 inch length.
In trying to modify the Optimo cabinet once it's built, it's not at all practical, maybe even impossible, to make a good ML-TL. Yes, you could block off the current large terminus opening and replace it with a port located either there or somewhere down the back of the cabinet. But the primary problem is the location of the woofer; it's way too close to the beginning of the line, which causes a big dip in the response between 100 and 200 Hz or so. Secondly, the current line is too long for an ML-TL to have both a good bass response and an overall smooth response above 200 Hz. Now if the woofer and tweeter locations were reversed, the woofer location would then be much closer to optimum, even with the existing line length, for an ML-TL. Finally, I've modeled ML-TLs for this specific driver for potential personal use, and I've found a line length of 60-65 inches much, much better, as compared to this line with its ~77 inch length.
OK: Over the weekend, I played around with the stuffing, and I have found a reasonable balance.
I removed the egg crate foam from behind the driver, but I have left a single piece just above it, at the end of the line.
I have stuffed VERY lightly with two strips of BAF (40mm each normally) which I had pulled apart to make less dense.
The sound is no longer closed in, and it is not harsh either. I am still not yet blown away by these, but we are getting there.
The next step is to try Wool stuffing instead of BAF. I have ordered some and will report back.
I removed the egg crate foam from behind the driver, but I have left a single piece just above it, at the end of the line.
I have stuffed VERY lightly with two strips of BAF (40mm each normally) which I had pulled apart to make less dense.
The sound is no longer closed in, and it is not harsh either. I am still not yet blown away by these, but we are getting there.
The next step is to try Wool stuffing instead of BAF. I have ordered some and will report back.
dublin78, a couple of questions:
Have you double and triple checked all of your xover wiring? I know it sounds obvious, but it's easy to make a mistake in the first xover and then to duplicate it in the second.
Also, are your drivers brand new? If they are, they'll need some time to break in to be at their best.
I've recently rebuilt a two way with the 18W8531 (8 ohm version of the 4531) into a TL similar to Tony's design, but with a shorter line (tuned to a higher frequency) for use more near field in a smaller room placed close to a wall. Regardless of what the various modelling software says about his cabinet design, my measured FR is very flat, and it has allowed the 8531 to perform (subjectively to my ears) in a way that it never did in the BR cabinet.
Tony's selection of cabinet design for the Optimo was very empirical - based on actual measurement and listening tests rather than software predictions. I may get flamed for this, but what also has to be borne in mind is that software predictions are only as good as the programmer and the theoretical assumptions made in the software design.
With any aspect of speaker design, there's a certain amount of theory/science involved to get to the starting point, followed by a great deal of experimentation and subjective listening tests to arrive at the finished product.
Have you double and triple checked all of your xover wiring? I know it sounds obvious, but it's easy to make a mistake in the first xover and then to duplicate it in the second.
Also, are your drivers brand new? If they are, they'll need some time to break in to be at their best.
I've recently rebuilt a two way with the 18W8531 (8 ohm version of the 4531) into a TL similar to Tony's design, but with a shorter line (tuned to a higher frequency) for use more near field in a smaller room placed close to a wall. Regardless of what the various modelling software says about his cabinet design, my measured FR is very flat, and it has allowed the 8531 to perform (subjectively to my ears) in a way that it never did in the BR cabinet.
Tony's selection of cabinet design for the Optimo was very empirical - based on actual measurement and listening tests rather than software predictions. I may get flamed for this, but what also has to be borne in mind is that software predictions are only as good as the programmer and the theoretical assumptions made in the software design.
With any aspect of speaker design, there's a certain amount of theory/science involved to get to the starting point, followed by a great deal of experimentation and subjective listening tests to arrive at the finished product.
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