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Multi-Way Conventional loudspeakers with crossovers

Pushing the limits of small speakers - The Reference Mini build thread
Pushing the limits of small speakers - The Reference Mini build thread
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Old 14th March 2017, 01:58 PM   #11
bcodemz is offline bcodemz  Canada
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Quote:
Originally Posted by Brisso57 View Post
Are you intending to put a good radius on all of the box edges?

cheers

Doug
I'm planning to put a 3/4" radius on the side panels. The front and rear baffle will be completely flat. There's no way to put a 3/4" radius on the front baffle without increasing the size, and it would be too small do anything for diffraction, and it wouldn't look good either.

Quote:
Originally Posted by Brisso57 View Post
Looking at your first cab, why did you not move the tweeter closer to the woofer? ... given you said you wanted the tightest grouping? Looks trump performance?

Doug
You mean both the tweeter and midrange closer to the woofer? That's because there needs to be room for the edges of the midrange, edge of the midrange chamber, and edge of the woofer. I also need it so I can put a piece of felt in between the woofer and the midrange and tweeter. That little space in between is much smaller than you think at around 0.5" wide.

If it is just the tweeter, I don't see how that would benefit things. The tweeter needs to be close to the midrange, and in this design, it is about as close as it possibly can.

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Originally Posted by chris661 View Post
For what it's worth, I really would've gone with one of the 5-6" mini-subs on the market. You talk about them being low-efficiency, and then apply 17dB of boost to get the frequency response of your chosen drivers flat. The mini-subs would have a lot more excursion available, which means more mechanical headroom and greater potential SPL. You'll need to test distortion figures, though.

If loud bass is a priority, I'd consider using some aluminium plate in the construction, perhaps with an extrusion that thermally connects to the magnets of bass drivers. They're likely to see some real power, and small confined spaces aren't good for that.

I've never heard a dynamic loudness contour done well, even with fairly nice commercial HiFi. We'll probably have to agree to disagree with this one, but for a reference piece, I wouldn't want the speaker doing anything other than taking the signal that's going in, and making it into sound as linearly and accurately as possible.

Chris
The mini woofers would not do as well believe it or not.

If you actually model this speaker, even at a full 150W of power, the driver only slightly exceed its modest Xmax at a narrow band between 55-75Hz. The box is far too small and insensitive to allow mini subwoofer drivers to use all of their available excursion unless I'm putting in 1000W. Therefore, an optimal mid woofer does just as good of a job with bass while providing much more sensitivity and sound quality for midrange. I could have thrown money at an expensive Audio technology or Accuton woofer, but it doesn't actually do as good of a job at bass and low midrange output than the less expensive Wavecor.

The amount of boost is that much simply because of the high 90dB sensitivity of the woofer. If I used a 80dB sensitivity woofer, I'd have a lot less boost, but the power needed is still roughly the same as dictated by the box size.

I haven't heard of many good equal loudness curve implementations either. However I can assure you, if properly done (and that's not easy), it sound subjectively much better with it.

Quote:
Originally Posted by brig001 View Post
Reading the text, you have two woofers, but I can only see one in the pics. Did I miss something? Love the concepts of this design.

Brian
The second woofer is on the back, right behind the front woofer.

Quote:
Originally Posted by USRFobiwan View Post
Stunning research for such a small little expansivebox. The dsp is also inside the box?
Do you have any measurements yet?
The DSP is outside. The miniDSP is the weak link for this speaker and I'll be looking for other DSP's to fill its shoes.

No measurements yet
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Old 14th March 2017, 05:51 PM   #12
sebbyp is offline sebbyp  United Kingdom
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Very interesting design and great research! I have been slowly but surely been looking to build a reference set of speakers in a very small cabinet capable of bass for my desk. I spend more time at my desk than I do in front of the hifi in the living room, I haven't got anywhere as close as you have! I have been thinking of something very similar though in the same vein as the ATC SCM25a layout.

A couple of thoughts and questions..

What listening distance do you have in mind for these?

Have you heard icepower amps? I appreciate you need high power to get the bass driver moving but they wouldnt be my first choice for such high end drivers. I would be tempted to plump for ncore at mid/highs or Class A/B. Then throw in a Icepower ASP1000 for the bass.

Do you think a BE tweeter is necessary? I know you have acquired it but do you appreciate the sound? I wasnt considering spending that much in a tweeter.

I would prototype with minidsp - was my plan too... However I would use Acourate or AudioLense to build your filters and then push audio through the pc... Not ideal if you want to plug your tv into them and a bit touchy to turn them on but opens up tremendous processing power and lots more taps. You could build a much simpler multichannel dac at that point.
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Old 14th March 2017, 06:19 PM   #13
chris661 is offline chris661  United Kingdom
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Quote:
Originally Posted by bcodemz View Post
If you actually model this speaker, even at a full 150W of power, the driver only slightly exceed its modest Xmax at a narrow band between 55-75Hz. The box is far too small and insensitive to allow mini subwoofer drivers to use all of their available excursion unless I'm putting in 1000W. Therefore, an optimal mid woofer does just as good of a job with bass while providing much more sensitivity and sound quality for midrange. I could have thrown money at an expensive Audio technology or Accuton woofer, but it doesn't actually do as good of a job at bass and low midrange output than the less expensive Wavecor.
Yep, I found my TB 6.5" mini-subs need a rocket up them to get moving. 500w peaks per driver is good, but they won't stand that power for anything other than transients.

Anyway, this is a really cool project and I'll be following along.

Chris
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Old 14th March 2017, 08:17 PM   #14
bcodemz is offline bcodemz  Canada
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Quote:
Originally Posted by sebbyp View Post
Very interesting design and great research! I have been slowly but surely been looking to build a reference set of speakers in a very small cabinet capable of bass for my desk. I spend more time at my desk than I do in front of the hifi in the living room, I haven't got anywhere as close as you have! I have been thinking of something very similar though in the same vein as the ATC SCM25a layout.

A couple of thoughts and questions..

What listening distance do you have in mind for these?

Have you heard icepower amps? I appreciate you need high power to get the bass driver moving but they wouldnt be my first choice for such high end drivers. I would be tempted to plump for ncore at mid/highs or Class A/B. Then throw in a Icepower ASP1000 for the bass.

Do you think a BE tweeter is necessary? I know you have acquired it but do you appreciate the sound? I wasnt considering spending that much in a tweeter.

I would prototype with minidsp - was my plan too... However I would use Acourate or AudioLense to build your filters and then push audio through the pc... Not ideal if you want to plug your tv into them and a bit touchy to turn them on but opens up tremendous processing power and lots more taps. You could build a much simpler multichannel dac at that point.
Listening distance is anywhere from nearfield desktop to filling a living room. This is designed as a travel speaker because I work in different cities a lot, but as you can see I got a little carried away

Yes I've heard of the ICEpower amps. It sounds better than any small eBay amp like the TPA3116/TDA7492 that I've heard, and that's coming from someone that does not believe in any noticeable sound quality differences between well designed amps (I don't consider the eBay amp boards to be well designed). The NCores are far too expensive. The amps alone would cost several times more than everything else combined, and by no means I'm using cheap stuff! The other problem was that fitting 4 and a power supply is a lot more hardware engineering work I don't want to do. I'm not really a believer in big sound quality differences in amps, so I'm not putting in efforts, especially that much money and effort for something I may not even hear a difference. Things like drivers, speaker tuning and DSP optimizations make a far bigger difference to me. I can hear a *massive* difference from just a 1dB difference in a shelf filter. I struggle to hear any difference between solid state amps.

Do I think a Be tweeter is necessary? No. I used them because the price increase isn't excessive, I won't ever get the "what if" thought in my mind, and it is the easiest thing to tell people to immediately tell them that this is a serious speaker and not just another crappy small speaker. If budget is an issue, I'd pass on the Be.

Last edited by bcodemz; 14th March 2017 at 08:23 PM.
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Old 14th March 2017, 08:41 PM   #15
Bare is offline Bare  Canada
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Originally Posted by bcodemz View Post
that's coming from someone that does not believe in any noticeable sound quality differences between well designed amps (I don't consider the eBay amp boards to be well designed)....I struggle to hear any difference between solid state amps.
.
That's a fairly interesting viewpoint.
There ARE major audible differences betwixt amps of various design.
I can only assume you've not heard many Amps then ?
Or are perhaps using erm.. Low level Sources and Speakers to base your perceptions upon ?
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Old 14th March 2017, 09:40 PM   #16
Brisso57 is offline Brisso57  Australia
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Quote:
Originally Posted by bcodemz View Post

Do I think a Be tweeter is necessary? No. I used them because the price increase isn't excessive, I won't ever get the "what if" thought in my mind, and it is the easiest thing to tell people to immediately tell them that this is a serious speaker and not just another crappy small speaker. If budget is an issue, I'd pass on the Be.
I'm going to follow this thread. It's very interesting, and of course the choices are yours to make.

What I'd like to propose - once you HAVE a working pair that are performing satisfactorily on your terms - is that you throw it open to everyone who may be interested to work on an alternate spec that perhaps provides 90%+ of the benefits, but at 25% of the cost. This is not to suggest that your goal is in any way unworthy, but there are many DIYers with limited budgets and they may well be interested in such a "budget version".

cheers

Doug
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Old 15th March 2017, 01:09 AM   #17
bcodemz is offline bcodemz  Canada
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Quote:
Originally Posted by Bare View Post
That's a fairly interesting viewpoint.
There ARE major audible differences betwixt amps of various design.
I can only assume you've not heard many Amps then ?
Or are perhaps using erm.. Low level Sources and Speakers to base your perceptions upon ?
I did rigorous A/B testing between several amps from decent receivers to sort of expensive amps. I thought I heard a noticeable improvement in one amp, but then it turned out it was because I had my ears tilted toward to the speaker whenever I switched to the other amp. This caused me to hear more high frequency, and hence the difference. When I made sure my head is not tilted between each test, the noticeable difference went away and I struggled again.

The only noticeable difference I've heard between amps is between a solid state and an expensive tube amp. The difference was immediate. But then it is 2 fundamentally different technologies, and the tube amp is noted for much higher distortion that is theorized to give them the characteristically pleasing sound.

But I'm not here to debate this. After digging this deep into audio with a scientific viewpoint, my experience is that most of my prior beliefs (and commonly believed beliefs) were wrong, and often the real cause is something different than what I expected. I would love to meet someone in the future that can hear major differences between amps, and let him pick any 2 amps he's confident he can tell a difference, let me do a double blind ABX test first to make sure I can't tell a difference (if I can, then I'm wrong), then watch him do the same double blind ABX testing.

Quote:
Originally Posted by Brisso57 View Post
I'm going to follow this thread. It's very interesting, and of course the choices are yours to make.

What I'd like to propose - once you HAVE a working pair that are performing satisfactorily on your terms - is that you throw it open to everyone who may be interested to work on an alternate spec that perhaps provides 90%+ of the benefits, but at 25% of the cost. This is not to suggest that your goal is in any way unworthy, but there are many DIYers with limited budgets and they may well be interested in such a "budget version".

cheers

Doug
I think few people understand the extreme efforts that went into the speaker to make it absolutely small, and how insanely complicated it is to build. If you don't have a CNC machine, this speaker flat out can't be built. I even went through the trouble to make a midrange chamber out of molded ABS plastic to squeeze an extra 7% of internal volume compared to using plywood.

To make a speaker as good as this that can be built with normal tools would require a substantially bigger enclosure, at least 2x. It's not just a bigger internal volume is needed, but 2-3x thicker wood, then it needs bracing. Moving from 1/4" to 3/4" wood increases the size of the speaker by over 50% without even increasing the internal volume. And you need thicker wood. Just think about how would you even screw in a rear mounted driver on 1/4" plywood? That required a special method all by itself just to achieve something as simple as mounting a woofer. These drivers had their driver frames machined off, and if you don't, you have to increase the front baffle length and width by 1", increasing the size by another 40%. These two alone almost doubled the size. Then you have other things that will increase size, such as amp placement. I built something special to stack the amps nicely to reduce footprint. Most people can't/won't do that.

I don't think it is possible to build a speaker 90% as good as this for a much lower price. Half the cost and twice the size would be a more reasonable estimate to achieve a speaker 90% as good, but at that point is not exactly small anymore. To keep it around the same size but still buildable means huge performance compromises.

Last edited by bcodemz; 15th March 2017 at 01:17 AM.
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Old 15th March 2017, 08:35 AM   #18
zman01 is offline zman01  Bangladesh
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Pushing the limits of small speakers - The Reference Mini build thread
bcodemz, very clear goals you have and like your execution... look forward to your listening impressions and (measurements).
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Old 15th March 2017, 02:01 PM   #19
stocktrader200 is offline stocktrader200  Canada
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why not use a really good 2 - 3" fullrange for 500 - 20000 Hz
90 db and point source
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Old 15th March 2017, 02:36 PM   #20
Jonhny is offline Jonhny  Sweden
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Two woofers in one 4L box?
Traditionally that looks like 100Hz extension in my Hornresponse simulation. The passive radiators gives you around 1dB extra output compared to a sealed enclosure in my simulation, so my guess is that they will barely be moving.

What is your plan there?
Am I misunderstanding something?

Last edited by Jonhny; 15th March 2017 at 02:40 PM.
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