Matching Tweeters, Mids and Bass

[lebeaudj]

Good Morning all,

As you may have noticed already, this is my virgin post on Audioholics and hopefully the start of many (and replies...)

Although I wouldn't call myself a beginner in general, I am just starting to research building cabinets instead of buying off the shelf. I am quite happy (and useful) with wood, spraying, etc, but calculating the correct speakers for my design is causing me a bit of a headache.

Basic background - I am currently looking to build a small, custom speaker rig based on 2 x 3 way speakers (Bass Driver, Mid and Tweeter) and possibly 1 or 2 Sub-Woofer boxes.

I am quite happy working out the cabinet designs (internal capacity, etc) but am getting stuck on working out the composition of the speakers.
So far I have managed to learn that in theory (could be completely wrong!) a two way speaker works on a 70/30 split (roughly) so based on a cabinet rating of 100W - that would be split 70W Bass Driver and 30W Tweet.

Can anyone expand or possibly point me at the correct calculations to find the correct speaker setup based on Output Wattage of each component?

Hopefully some of this makes sense - I know what I want to ask in my head, putting finger to keyboard loses some of the translation!

Regards and thank you in advance,

Dan
UK

 

[jonnythan]

Well that depends on the crossover network.

Building a 3-way crossover is a lot more complicated than a 2-way, which is itself pretty complicated. Ambitious first project, certainly.

 

[Swerd]

Although I wouldn't call myself a beginner in general, I am just starting to research building cabinets instead of buying off the shelf. I am quite happy (and useful) with wood, spraying, etc, but calculating the correct speakers for my design is causing me a bit of a headache.

Basic background - I am currently looking to build a small, custom speaker rig based on 2 x 3 way speakers (Bass Driver, Mid and Tweeter) and possibly 1 or 2 Sub-Woofer boxes.

I am quite happy working out the cabinet designs (internal capacity, etc) but am getting stuck on working out the composition of the speakers.
So far I have managed to learn that in theory (could be completely wrong!) a two way speaker works on a 70/30 split (roughly) so based on a cabinet rating of 100W - that would be split 70W Bass Driver and 30W Tweet.

Can anyone expand or possibly point me at the correct calculations to find the correct speaker setup based on Output Wattage of each component

Dan

Welcome to AH , and because you are interested in DIY speaker building, make that a double welcome .

Your woodworking experience will certainly help quite a bit. Your other questions about selecting drivers and how to blend them well, suggest you have a lot to learn. There are books that cover the basics of speaker design, such as Speaker Building 201 by Ray Alden. I don't know what would be the best source of that book in the UK.

Because others have asked similar questions to yours, I have linked a few threads you might want to read:

Where to begin?

Practical Outline of DIY Speaker Design

An Example of 3-way crossover design

I have one question for you. Do you want to invest the time and money to learn how to properly design speakers, or do want to build your own speakers one time? I ask this because the measuring equipment is expensive and requires experience before you become good at using it, and because there are many good DIY designs done by others available on the internet. I can suggest a few, such as the ER18 MTM.

 

[lebeaudj]

Thank you both for your replies....

I possibly need to explain my plans overall a little better so you can better answer my question (I hope!).

In the very near future, my wife is planning to buy a franchised drama school here in the UK. I also tend to get asked a lot of "favours" from friends and family to provide music for events.
I have worked for many years with A/V equipment, generally on a commercial scale, providing services for festivals, conferances, etc... Because of this I have a good knowledge of building systems, acoustics, etc.
Over the years it feels like many companies are producing more and more poorly build speakers, amps, etc.

Based on the above, I would love to build custom cabinets (woodworking, covering, painting skills) for use in a "general" setting. My overall design will be modular, so as time goes on, I can add bass bins (subs) and more.

At the moment, I will be useing off the shelf speakers, crossovers and cabinet furniture (corners, handles, inputs, etc).

So, hopefully the question makes more sense with a little more background, but to re-word...

I know that within a standard speaker cabinet the output ratings for bass driver, mid-range and tweeter will be different. I am aware that a cross-over is used to split the input signal into the correct ranges for each speaker.

Is there a calculation based on a cross-over (are there specific values for each output?) with a specific output value (i.e. 100W RMS) that will tell me what my max outputs for each speaker need to be?

As a secondary question, what upper and lower hz and mhz rating is desirable on a crossover?

I hope I make a little more sense this time and as you guessed, at this point, I am not interested in building the electrical/speaker parts of the project. If this goes well, I hope to dive into that part of building at a later stage.

Kind Regards,

Dan

 

[Swerd]

… At the moment, I will be using off the shelf speakers, crossovers and cabinet furniture (corners, handles, inputs, etc).

I know that within a standard speaker cabinet the output ratings for bass driver, mid-range and tweeter will be different. I am aware that a cross-over is used to split the input signal into the correct ranges for each speaker.

I hope I make a little more sense this time and as you guessed, at this point, I am not interested in building the electrical/speaker parts of the project. If this goes well, I hope to dive into that part of building at a later stage.

Dan

Although I want to strongly encourage your enthusiasm, your words, "off the shelf speakers, crossovers, …" and "I am not interested in building the electrical/speaker parts of the project" give me pause.

The real function of a properly designed crossover in a speaker is to smoothly blend the output of a woofer and tweeter (in a 2-way), without any dips or peaks, so that the two drivers sound as if they are one. This requires more than selecting the low-pass frequency for the woofer and the high-pass frequency for a tweeter. The crossover also has to act as an equalizer. The reason why DIY speakers with custom designed crossovers usually work so much better than most commercially available speakers is that most commercially available speakers use improperly designed crossovers. Trying to use "off the shelf" crossovers with two or more drivers, even if they are carefully selected, will not result in success.

For this reason, I strongly suggest that you first try building existing designs. Your post suggests to me that you are more interested in building public address (PA) speakers than for home audio. Correct?

Is there a calculation based on a cross-over (are there specific values for each output?) with a specific output value (i.e. 100W RMS) that will tell me what my max outputs for each speaker need to be?

The problem is more complex than adjusting for maximum output. There is no simple (or complex) formula for this. It requires measurements of frequency response and impedance of woofers and tweeters already mounted in appropriately designed cabinets.

As a secondary question, what upper and lower hz and mhz rating is desirable on a crossover?

Without first selecting a woofer and tweeter, it is not possible to answer this question.

 

[GranteedEV]

I know that within a standard speaker cabinet the output ratings for bass driver, mid-range and tweeter will be different.

Output ratings are a lot more complex than just "watts". A balanced speaker design will factor in things like sensitivity, impedance, thermal power handling, ability to maintain motor force, suspension linearity, and most important of all - intended passband.

I am aware that a cross-over is used to split the input signal into the correct ranges for each speaker.

For each collection of drivers in a speaker, the crossover must be carefully custom-designed, in order to get them to behave as a single, tonally balanced, undistorted speaker.

Is there a calculation based on a cross-over (are there specific values for each output?) with a specific output value (i.e. 100W RMS) that will tell me what my max outputs for each speaker need to be?

You need to throw the concept of watts out the window, for starters. It's akin to designing a car for x amount of horsepower. It's an easy sell, but there's so much more going on and that in and of itself is just a by-product.

As a secondary question, what upper and lower hz and mhz rating is desirable on a crossover?

There is no single desirable frequency, if that's what you're asking. There's different frequencies where different drivers will have the best

Additionally, getting a crossover transfer function to behave as "planned", especially for a passive speaker but even for an active speaker, isn't as simple as picking a number and sticking it in. You need to factor in acoustic rolloffs and otherwise individualized driver frequency response, as well as its off axis behaviour, and also its interaction with the enclosure, as well as its power handling in the passband, among countless other things. A woofer that can take 100wRMS at its resonance frequency in free air, can't take the same thermal power at a frequency where it's barely moving. A woofer that can take to full excursion, will damage itself with the same power input on a 10hz tone. So the concept of power handling, as I stated earlier, needs to be thrown out the window until you can figure out the optimal power handling for the system as a whole. Watts ratings have their use, but they're also somewhat useless.

At this point, I am not interested in building the electrical/speaker parts of the project.

Then a kit of some sort is absolutely the plan of action you need to take. For your purposes, which appear related to larger rooms, Perhaps look into

Wayne Parham's Pi Speaker Kits

http://www.pispeakers.com/