A Few (hopefully) Quick Questions - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Old 04-13-2006, 06:54 PM - Thread Starter
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1.) When selecting your drivers, is it important to have matching sensitivities throughout all the drivers? If not, is there some kind of guideline, i.e., don't exceed more than a 2dB difference between drivers and/or does a crossover compensate for this?

2.) When selecting a midbass & tweeter combo, I read somewhere that the tweeter should pick up 1-2 octaves above the Fs (resonant frequency?) of the midbass? Is this true? If not, what is the guideline in selection? Is it smarter to stick with the same brand between midbass/woofer and tweeter or does it not matter? Also, if using an aluminum cone midbass should a metal dome tweeter be used for continuity or can textile domes be mixed and matched with aluminum midbass/woofers and vice-versa?

3.) How important is building your own crossover? Would I be able to get away with buying a pre-built xover from PartsExpress or some other retailer without sacrificing too much in sound quality as long as it mated well with the drivers I've chosen?

4.) From messing around with WinISD, it seems to be only for subwoofer cabinet construction, is there anything similar (that's $free$) for designing bookshelf or tower speakers?

Thanks guys. I have The Loudspeaker Design Cookbook coming, but I just can't wait! And searching the web yields too many deadends, not to mention me getting distracted by other information, so I figured I'd ask here.
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post #2 of 7 Old 04-14-2006, 02:15 AM - Thread Starter
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On a sidenote here, I was reading the driver round-ups and reviews on the Zaph Audio (zaphaudio.com) website, and now I'm honestly scared to buy any driver for fear of it sounding poor. All this talk of breakup nodes, and harmonic distorion at X frequency... meh, maybe it's just overwhelming. On the other hand though, I took apart my pair of Polk Audio Monitor 40 bookshelf speakers tonight (dual 5 1/4" woofers, 1" tweeter, MTM array), just to see the internal construction and hoping to to see if the drivers used were branded (I was careful not to damage or mar anything, as I will be returning these speakers). To my surprise, there was no internal bracing and only a small amount of stuffing, or filler, whatever, clumped at the bottom of the cabinet. Unfortunately, the drivers weren't branded. I don't know if this is cheap construction or not, but I expected a bit more, as these speakers sound pretty good for their retail price of $299/pair. So maybe it isn't so complex to create a pair of passable-sounding speakers.

If any of you veterans out there would like to take a newb under their wing with regards to design, driver choice, and possibly some finishing advice via PMs I would be extremely grateful. Obviously this would be on an as-time-permits basis for any kind soul who cares to help me out. Please send me a PM if you are interested, and once again I would be very appreciative. :)
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post #3 of 7 Old 04-15-2006, 12:23 AM
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Quote:
Originally Posted by DirectX
1.) When selecting your drivers, is it important to have matching sensitivities throughout all the drivers? If not, is there some kind of guideline, i.e., don't exceed more than a 2dB difference between drivers and/or does a crossover compensate for this?

Not really, the crossover can fix the differences

2.) When selecting a midbass & tweeter combo, I read somewhere that the tweeter should pick up 1-2 octaves above the Fs (resonant frequency?) of the midbass? Is this true? If not, what is the guideline in selection? Is it smarter to stick with the same brand between midbass/woofer and tweeter or does it not matter? Also, if using an aluminum cone midbass should a metal dome tweeter be used for continuity or can textile domes be mixed and matched with aluminum midbass/woofers and vice-versa?

You want each speaker to be able to operate in it's "sweet spot". As for brand mixing, it doesn't matter as long as the crossover is good

3.) How important is building your own crossover? Would I be able to get away with buying a pre-built xover from PartsExpress or some other retailer without sacrificing too much in sound quality as long as it mated well with the drivers I've chosen?

This is __BY FAR__ the most important aspect of DIY speakers. If you don't have an INTIMATE knowledge of crossover design and the proper toolset to take measurements and tweak designs, don't even bother because you will end up with very very subpar results

4.) From messing around with WinISD, it seems to be only for subwoofer cabinet construction, is there anything similar (that's $free$) for designing bookshelf or tower speakers?

Not that I know of. I don't mess with crossover design much, so I just stick with established designs that others have done.

Thanks guys. I have The Loudspeaker Design Cookbook coming, but I just can't wait! And searching the web yields too many deadends, not to mention me getting distracted by other information, so I figured I'd ask here.

.
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post #4 of 7 Old 04-15-2006, 01:34 AM - Thread Starter
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Thanks Fryguy. So do you have any idea what kind of tools and gadget I'll need to take proper measurements to tweak crossovers? And if so how much do you think it will cost, total? Thanks.
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post #5 of 7 Old 04-15-2006, 01:35 AM
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No, like I said I don't get involved in speaker design at all. I just research and use/recommend existing designs.
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post #6 of 7 Old 04-15-2006, 06:06 AM
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X---As far as differing driver sensitivity; just make sure the mid and tweeter are more sensitive than the woofer, you can easily adjust their outputs with L-pads.

Don't worry too much about crossover design yet, most DIY speakerbuilders start with turnkey crossovers like PE models and you can get good results with them. As you go along you'll get deeper into crossovers.

"When selecting a midbass & tweeter combo, I read somewhere that the tweeter should pick up 1-2 octaves above the Fs (resonant frequency?) of the midbass? Is this true?'

No, absolute rubbish. If true this would have us crossing from woofer to tweeter at 200hz. Look at the response curve of the woofer chosen and crossover to the next driver before rolloff or at rolloff. Much depends on the crossver slope. If you use 1st order (6db per octave) you need to cross earlier than if using a higher order crossover. You can mix brands and materials.

The same principles for bass enclosure design hold true whether the box is to be used as a sub or as a fullrange speaker.

Read the cookbook and any other speaker design books you can get ahold of such as the excellent little books by John Weems. Don't be afraid to use simple and easy methods, there will be plenty of time to get complicated as you go along. Very basic speakers can sound very good.

You'll also have Berenek's Law in your favor. Berenek's Law states that when one builds a speaker according to one's notions of what should work the speaker will sound good to the builder.
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post #7 of 7 Old 04-15-2006, 07:27 PM - Thread Starter
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Tom! This is the kind of response I was looking for, solid answers on my questions and very encouraging to boot! Thanks a bunch, I feel much more confident about undertaking my project now, amid all the talk of breakup nodes and perfectionist crossovers, feeling confident you can create a quality sounding speaker is what's important, and will allow me to truly enjoy creating and hopefully listening to them instead of worrying about getting every exact detail perfect. Although perfection is good, when you start on your first project, some of the advice given here can be pretty overwhelming. I think some of the more experienced people around here may forget the anxiety that goes into your first build, nobody likes to build something that's crap, much less to have to worry about every miniscule detail (perfectionist xover tuning) during the construction period.

Thanks again Tom.

Edit: I think I love Berenek's Law. :D
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