Arpeggio Music & Sound

    
 

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Frequently Asked Questions

General

How can I learn about speaker building?
Speaker building can be as simple as buying and building an easy pre-designed kit, or as complicated and involved as fine woodworking, complex analog (or digital) electronics, and calculus-based acoustical physics (all of the latter went into this site's development). In other words, this can be as simple or as complicated as one wishes to make it. The purpose of this site is to simplify and consolidate some of its more complicated, tedious and overlooked elements into an easy-to-use system. In addition, there are many excellent books on the subject. We found Speaker Building 201 particularly practical and useful (though it has many typographical errors, especially in its formulas).

Where can I get speaker parts?
You are welcome to purchase speaker parts from us as kit, individually, or even assembled into the final speaker. When you design your system, the parts list can be automatically combined into a single parts kit and ordered via our store. We carry only mid-level to top-grade audiophile components (Mills non-inductive resistors, Reliable AudioCap Polypropylene and Tin foil (theta) capacitors, Alpha foil inductors, etc.). Components with lower prices and lesser reputations can be found elsewhere; there are dozens of speaker parts suppliers in the world. Just do a search for 'speaker parts' on your favorite search engine (or click here).

Do I have to pay anything to use this site?
No, general use is free. But you will not be able to use some of its more advanced features unless you make a donation of at least $25.

Why is this site so plain. Give me some graphics!
The time we would spend on snazzy graphics is better spent designing and making speakers (and improving the formulas on the site). Some graphs are genuinely useful, but many are a little like real-time freight tracking; it is a nice 'warm fuzzy,' but it doesn't actually help the package arrive any faster (or at all). First, most graphs used for speaker design are hypothetical, mathematical predictions or, if they are empirical, are measured in an entirely different environment than that in which the speakers will ultimately reside. Consequently, their usefulness is questionable at best for practical speaker building. We find the graphs provided by the manufacturers useful for estimating the flatness of driver response and helping to find good crossover points.

Should I use the speaker's factory specs, or measure them?
It depends on your religion, your budget, and your free time. Given the other factors that affect the perceived sound, we aren't convinced that it is necessary to set up your own anechoic chamber, test equipment, etc., to do speaker measurements. If you have the time, drive and budget, go for it -- you may very well get more precise results; it might make you feel better about the project, too, which is a good thing. But unless there is a QC problem at the factory, their specs should be close enough. In our own practice, we do measure the specs for the purpose of fine tuning the crossover componenents, but we design the enclosure off of the factory specs.

I want to call you with a question. What is your number?
Sorry, but we've probably no time for that. Feel free to send us an e-mail via our contact form. If we have time and know the answer, we'll reply.

What is this gibberish in my project save file?
That is simple-encoded text. Don't mess with it, or you won't be able to reload your project.

Do you have a library of drivers?
Yes, for several hundred. Once you've added an enclosure to your project a down arrow will appear next to the drivers. Click the down arrow to go to the driver import screen.

Design Issues/Problems

I entered [strange/fancy configuration X] and the results don't make sense. Is something wrong with the site, or my design?
Maybe one. Maybe both. Perhaps neither. The site does not anticipate every possible speaker configuration. Just the basics, though it handles these fairly well. It could be that you are attempting a configuration that was not anticipated by the program.

When I enter the EXACT figures suggested by the 'ported enclosure' recommendation, the system projects a lower volume resonance. Why?
The initial ported enclosure recommended figures are based on general rules of thumb and 'cookbook'-style speaker formulas. The projected box resonance is based upon actual Helmholtz resonance physical acoustics experiments and takes into account (approximately) the effect of air at the port openings. For this reason, the actual port can often be a little shorter than the 'cookbook' port length, and if you enter a port with the cookbook length, it will project a lower box resonance. The good news in this is that you can either use a slightly shorter port, or better yet, a smaller box, and still get a good, low air resonance.

Will you please add the ability to handle [configuration Y]?
We'll consider it. Please e-mail us the details.

Which SPL basis should I use here?
Pragmatically, it doesn't matter that much as long as you use the same one for all of the drivers in a particular enclosure.

The site is not properly indicating the polarity for my complex crossover.
Alas. Determining speaker phase polarity is not presently incorporated into the system except for obvious cases (parallel or push pull systems). Using a signal generator you can easily check for properly polarity by ear and adjust accordingly.

What about active filter designs?
There are some compelling reasons to use active filtering and amplifiers for individual drivers... if you have the time and money. For our purposes, however, passive crossover systems are usually more than sufficient.

Active FiltersPassive Filters

Pro

  • Less hum at high power levels
  • Less expensive, smaller and lighter discrete components (the crossover might cost just a few dollars in components and weigh a few ounces)
  • Greater array of discrete component values allowing closer tuning of the filter

Con

  • Generally requires a separate amplifier and power line for each individual driver in each enclosure
  • Clipping at over-power levels (which not only sounds bad but can damage some drivers)
  • Additional cost of individual amps generally offsets any savings found in the crossover circuitry
  • More susceptible to power spike damage than passive components

Pro

  • Simple wiring
  • Usually requires only a single receiver/amplifier
  • Handles power spikes well without clipping or damage (but by passing them right through to the driver)

Con

  • Larger, more expensive individual components (a quality, two-way, 3rd order crossover can cost about $50 in parts and weigh over a pound)
  • More difficult to fine tune due to component value separation
  • Usually consume more power and more-likely to hum and high power levels
  • Three or more way crossovers can pose impedance problems for some amplifiers
  • Driver feedback into the circuit may "color" the sound

How do I make the port?
We use black ABS material, cut it to length, de-burr and round the internal end, and cut a hole in the enclosure face to fit snug. We create a support within the enclosure, and glue the ABS into place at the enclosure face panel and internal support. We then trim-route, sand and polish the visible end. The results are very professional-looking. You can also use PVC (usually white), or pre-made ports with flares available from some suppliers.

What material should be used for the enclosure?
The enclosure fulfills two primary functions; mechanical housing and acoustic coupling for the drivers, and aesthetic appearance. It is, after all, a kind of furniture. Many kits and makers use MDF, medium-density fiberboard in 3/4 or 1 inch thickness, then apply laminant or paint. This is relatively easy, requires little woodworking skill, and is inexpensive. Six boards, some glue, nails or screws, and you have a box. However, if you have the resources and understand woodworking, hardwoods are very nice. It is worth noting that nothing that is particularly valuable, visually-pleasing or long lasting is ever made from MDF. Also, MDF is sensitive to moisture (it expands, often permanently). We use solid hardwoods because this results in a finished box with strength surpassing MDF, more rigidity, and superior appearance (no one wants to see MDF dovetails, do they?).

But some have said that hardwoods should not be used for speakers?
A properly-constructed hardwood box is not only as strong or stronger than MDF, but it is better looking and longer lasting. It is true, however, that a poorly constructed hardwood box will have problems, as would any poorly constructed box. It is also true that some hardwoods continue to expand and contract slightly with relative humidity, but certainly not enough to affect a speaker's performance to a degree discernable to the human ear, and proper construction methods preclude any possibility of the wood 'breathing' causing leaks.

Which is better, box or pedestal enclosures?
It is primarily a matter of taste, skill, tooling availability and budget. Box enclosures are easier to make, require fewer tools, and mount nicely on stands. Pedestal enclosures have the same acoustic properties, but are visually more pleasing (to most people). The require greater woodworking skill, additional wood and more tools. Either style can be made with hardwood or MDF. A significant advantage to (our) pedestal enclosures is that the crossover circuitry is mounted externally (hidden under the apron). The allows for easy crossover adjustment, if needed, without having to crack open the entire enclosure. It also eliminates crossover heat and vibration problems under high power conditions.

I see that I can get just about everything I need for my speakers from you except for drivers. Where should I get them?
We have chosen not to stock drivers at this time for a variety of reasons (mostly because the manufacturers require purchases of at least 250 units of each model). You can get drivers from many places. The most popular sources (in no particular order) are Parts Express, Speaker City, Madisound and Zalytron. Each carries a slightly different selection, and prices can vary significantly. If you are ordering a kit of other parts from us we can acquire the drivers for you for 20% over whatever we pay for them at the going market price (we buy drivers direct from distributors at a slight discount over public retail prices -- but not much).

Why is the 'Power Effeciency' percentage so low?
Because speakers are quite inefficient at converting electrical power to acoustical power. This figure just tells you what that amount really is.

The speakers and port are not lining up the way I want on the enclosure diagram. What can I do?
Don't worry about it. The purpose of the enclosure diagram is to provide outside measurement drawings for the enclosure materials, not layout your port and driver locations. The speaker and port images are just 'sanity-checks' to make sure everything will fit in the box. It isn't intended as a tool for laying out the drivers and port (yet).

Why are some of my projections reading zero or 'NaN'?
This happens when a variable has not been entered that is necessary to try to come up with the variable you are examining. Try filling in more data for your driver and enclosure.

This is pretty neat. Is it copyrighted?
The source formulas used to derive the results are in the public domain. However, this site and its original content are all protected by copyright law. You are welcome to reproduce and distribute the information found here as long as your reproductions include an obvious reference (http address) back to this web site and acknowledge the source using the following or similar language:

Copyright 2005 Simple Way Limited Partnership dba Arpeggio Music and Sound: http://speaker.rosaryshop.com/index.php. All Rights Reserved. Used with permission.

If you have a web site or use e-mail and wish to provide a link/referral to this site, we welcome it. The address to link to is http://speaker.rosaryshop.com/index.php.

Accounts, Donations

My e-mail address has changed and now I can't sign back in. What do I do?
Sign in using your old e-mail address until your key code expires, then get a new key code with the new address.

I made a donation, but did not get a key code with full access. What's up with that?
Full access key codes are only available if you donated $25.00 or more. Either your donation was less than this amount, you entered an incorrect e-mail address, or something went very wrong with the Internet's routing of your particular e-mail.

I've made a donation, but I lost or never received the e-mail containing my key code. Can I get a replacement?
We will do so once, but only by sending it to the address you used to register. If you've changed addresses, you are out of luck.

Do you sell my e-mail address to others?
No.

I made a donation. Why did the charge appear as "The Rosary Shop"?
The Rosary Shop and Arpeggio Music and Sound are are 'sister' companies of sorts (they are actually both just expressions of Simple Way Limited Partnership). The Rosary Shop clears all credit card charges for both companies.

Is this site secure?
Yes, the donation system uses The Rosary Shop's security certificate.

I made a donation and now have changed my mind.
Hmm. Bummer. Donations are not refundable.




Copyright 2005 Simple Way Limited Partnership DBA Arpeggio Music and Sound. All Rights Reserved. http://speaker.rosaryshop.com/index.php Terms of Use

Arpeggio Music and Sound, 805 NW Alder St, McMinnville, OR, USA. 97128
Telephone 503-472-0688; FAX 503-434-5803; Hours 10 AM - 5 PM Pacific Time, Monday through Friday
Visits by appointment only.