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Author Topic: The great speaker design thread  (Read 2141 times)

Consul

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The great speaker design thread
« on: December 19, 2006, 12:52:58 am »

Instead of just asking you specific questions on what I want, I thought I might instead ask some more generic questions that we can all benefit from.

When it comes to speaker design, specifically for studio monitoring, what are the aspects of a loudspeaker design that are most important? By that, I guess I'm referring to parameters: Qtc, Fc, and the like.

Do you prefer ported or sealed enclosures? Or perhaps chambered enclosures, where some drivers are sealed and some ported?

Can a two-way ever be a good monitor, or do you really need a three-way? How about full-range elements, and how they might fit in? (I would imagine room size and treatment has a lot to do with these questions.)

The only thing I've learned in studying the field is that there is more than one way to skin this cat. I read through the Loudspeaker Design Cookbook, and here's what I came away with:
  • Sealed enclosure, which means higher-Qts drivers, above .30 or so.
  • Low cabinet Qtc, around .8, which means a pretty large box.

According to him, this will give a high transient response, which means a more accurate speaker. At least, that's how I interpreted it.

I appreciate any response you have to give. Thank you for your time, and I hope this isn't too many questions at once.
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Darren Landrum

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L_Tofastrud

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Re: The great speaker design thread
« Reply #1 on: December 22, 2006, 10:38:40 am »

I think you're question is a little bit too open ended for me to give you a real reply.  Books have been written on the subject and every single loudspeaker manufacturer will give you a different answer.

What do you need from the loudspeaker system?  What size restrictions do you have?  The budget?

It's a series of compromises where the parameters that you mention are just a small part of the data that needs to be examined.  Power handling, max SPL, target cabinet size, and so on are all equally important as those you mention.  The selected drivers will also need to have other design features, like voice coil cooling method, magnet system design, cone material, cone size,  and last but not least the desired sound quality.

Finally it's how you integrate the drivers you pick into a system.  This is an area where there are a lot of easy solutions floating around.  An off-the-shelf crossover might look like an easy solution but unfortunately it is so only if the drivers you picked are flat 2-3 octaves beyond your xover point.  Without a properly designed crossover it doesn't really help how good your drivers are or if they are in closed or vented cabinets.  A properly designed xover means that it is the measured frequency response of each individual driver that conforms to, for example, the very popular linkwitz/riley 24dB/oct.  The transfer function of the electrical filter alone isn't important - it is the sum of the xover plus the driver that is important.

Consul wrote on Mon, 18 December 2006 22:52


  • Sealed enclosure, which means higher-Qts drivers, above .30 or so.
  • Low cabinet Qtc, around .8, which means a pretty large box.

According to him, this will give a high transient response, which means a more accurate speaker. At least, that's how I interpreted it.


We can discuss this for a looooooong time.. it has been discussed by people the last 50 years Smile
Closed boxes has their own set of compromises, like limitations when it comes to maxSPL and low-frequency extension.  To get this you need a HUGE box and large cone area and huge xMax, and other parameters that actually fit for this box.  Then you need the power handling to reach the target SPL...
They _might_ have better transient response but there are plenty of poorly designed closed boxes where transient response is way worse than a reasonably tuned bass reflex box.  Unfortunately there is no holy grail and the only thing that will tell _you_ what you like better is to start designing loudspeaker systems
Smile

Regards
Lars Tofastrud
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Consul

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Re: The great speaker design thread
« Reply #2 on: December 22, 2006, 12:10:28 pm »

Thank you for the reply!

Actually, you just gave me a much better answer than I was hoping for. Wink Because, you just told me all about why the large sealed box will not work for me at all, as I suspected it might not.

Unfortunately, I have two possible situations I might be in. One is to build out my small but serviceable basement. Right now, that plan looks something like this (clickable thumbnail):

http://img395.imageshack.us/img395/4752/basementstudioww0.th.jpg

(EDIT: I just realized that the dimensions aren't really visible in that image. My basement is 13' by 17' by 6.5'.)

If I can get the basement, I can build soffits for the monitors to sit in, which would be ideal.

If I end up stuck using my bedroom, which is smaller (though a higher ceiling), I won't be able to have either soffit walls or a drum set (that last one is the one that irritates me the most about the whole situation). Unfortunately, the room is too small for any standalone speakers to be able to sit three feet or however much out into the room as well. That leaves me with one option: build a set specifically designed to hang on the wall.

(Just as an aside, the basement leaks water, and it's going to be a real chore to fix that, because it means digging outside the house to re-do the backfill. I really don't think that's going to happen, which means trying to seal from the inside, which is at best a temporary solution. I swear if I ever get my hands on the so-called contractor who "re-modeled" it...)

One of my other problems, getting back to speakers themselves, is that I've only very recently started paying attention to how various speakers I like the sound of are designed, but in the end, I can tell you the best ones I've heard are relatively small ported boxes. Usually, they're back-ported, which wouldn't work well for either soffit- or wall-mounting.

As for my requirements, well, I'm a prog-rock guy, so 40-20K would be fine. I'm an IT guy, so I'm considering doing the crossover in DSP with a dedicated computer system, which I've researched a lot of in the past few weeks. Regardless of what room I get, they are both small, so any drivers beyond 8" in size would likely be pointless. My budget? That's up in the air at the moment, as I want to know what to aim for. A computer crossover set-up will likely be about $800 or so for a computer and decent sound card right there (yes, I know people will say I need $1000 just for the sound card, but that part of the system is upgradeable quite easily). Add in the drivers, and I'm looking at $1200 or so I think. MDF is cheap, so I'm not really counting that. Of course, there's always active crossovers if the computer option doesn't pan out.

That was probably more ranting than real information, but there you go. Smile Again, thank you for the reply.
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Darren Landrum

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Tom C

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Re: The great speaker design thread
« Reply #3 on: December 24, 2006, 07:35:34 am »

Consul wrote on Fri, 22 December 2006 18:10


If I can get the basement, I can build soffits for the monitors to sit in, which would be ideal.



You know that this won't be 'real' soffit mounting?
The (theoretical) advantage of soffits is that they are mounted
directly in a (concrete/stone) wall.

Quote:


[...]
would likely be pointless. My budget? That's up in the air at the moment, as I want to know what to aim for. A computer crossover set-up will likely be about $800 or so for a computer and decent sound card right there (yes, I know people will say I need $1000 just for the sound card, but that part of the system is upgradeable quite easily). Add in the drivers, and I'm looking at $1200 or so I think. MDF is cheap, so I'm not really counting that. Of course, there's always active crossovers if the computer option doesn't pan out.



To be honest, with that budget you'd most probably a better
quality/dollar ratio when you buy some decent active
nearfield monitors and maybe a small sub for the lower octave.

Believe me, if you really want to do all the R&D for a good
2- or 3-way monitor setup the measuring/analysing hardware
alone will cost you more.




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Tom

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Consul

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Re: The great speaker design thread
« Reply #4 on: December 24, 2006, 12:34:04 pm »

Believe me, there's a part of me that wonders if I'm over-thinking this, and should just find a good set of used monitors somewhere. A few friends have already pointed out some of the real bargains out there right now, like the EV Sentry 100a, which can be had used for as little as $100 in good working order. Tannoy PBM 6.5s are also an option, at around $150 a pair in good working order.

If I can learn something from an investigation and a few thought experiments, though, why not?

EDIT: And just to let you know, that soffit wall as in the drawing is just me being lazy with the CAD software. The real thing would be much meatier. I'm still debating whether they are worth the trouble, though.
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Darren Landrum

"Never be afraid to try something new. Remember that a lone amateur built the Ark. A large group of professionals built the Titanic." - Dave Barry

franman

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Re: The great speaker design thread
« Reply #5 on: December 31, 2006, 03:03:53 pm »

In our designs In-wall monitors (I don't like to use the term soffit mounted, as this infers some type of overhang to me) are used for a couple of reasons...
1. The mains will get an inherent bass reinforcement by installation in the "infinite baffle" that the front wall provides.
2. The fixed monitor position is controlled by design (both a blessing and a curse!!)
3. The large main monitors are build in and thus out of the way.

I agree whole heartedly that the front wall must be massive, rigid and strong for in wall monitor applications but I don't feel that it needs to be concrete/stone... The concrete front wall has been implemented a few times in well known design with great results, but to do it right while detailing the typical window, amp racks and speaker enclosures is a construction feet for none but the most experienced... it's tricky sh_t man...

At the end of the day, I would have to agree with Tom and say that you will probably do best to purchase some decent two-way active monitors and spend time on positioning and installation of as much bass trapping as possible..

Just want to get some thoughts posted on the In-Wall monitor issue.. this could be a good thread spin-off on it's own..  Twisted Evil

cheers.


Tom C wrote on Sun, 24 December 2006 07:35


You know that this won't be 'real' soffit mounting?
The (theoretical) advantage of soffits is that they are mounted
directly in a (concrete/stone) wall.

To be honest, with that budget you'd most probably a better
quality/dollar ratio when you buy some decent active
nearfield monitors and maybe a small sub for the lower octave.

Believe me, if you really want to do all the R&D for a good
2- or 3-way monitor setup the measuring/analysing hardware
alone will cost you more.


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Consul

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Re: The great speaker design thread
« Reply #6 on: December 31, 2006, 04:37:33 pm »

Yeah, I'm thinking it would be both cheaper, easier, and in the end better for me to go without building a new set of walls. Which leaves me with the matter of the speakers themselves.

This design looks interesting:

http://www.zaphaudio.com/ZD5.html

Sure, I could go build my own, but my ability to test speaker builds is limited at best. The ZD5 would run me about $600 for all of the parts. That's as much as I'd pay for an average sounding set of studio monitors that I may or may not like.
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Darren Landrum

"Never be afraid to try something new. Remember that a lone amateur built the Ark. A large group of professionals built the Titanic." - Dave Barry
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