Xmax, efficiency and enclosure confusion

[j.michael droke]

Xmax importance!

Haha thanks for all the info guys. All information is helpful to me at the moment. I think ill miss the LT this time, I am happy enough with the frequency response anyway. But now at least I know for future subwoofers 🙂 Just quicky, when an amp says for example '6db boost at 30hz' is this a form of equalising? and surely that +6db isn't just at 30hz but also the surrounding frequencies? Cheers!

Hi there M: You have been introduced to a large volume of information about loudspeaker drivers and associated enclosures. However, possibly lost in the explanations is the importance of Xmax and mechanical Xlim. If you turn the volume up too high in an attempt to get most bass possible (your stated criteria) and exceed Xm (either one) you risk destroying that really good Dayton RSS driver(s). Usually, bass drivers and all sub woofers are connected with a limiter circuit that cuts off (roles off) the low bass at a frequency higher than the point where Xm would be exceeded. Suggest you purchase a copy of Vance Dickeson's book "Loudspeaker Design Cook Book" 7ed, to get a basic understanding. The book is available from Parts Express or Amazon (new or used). ...regards, Michael

 

[peufeu]

My aim with this sub is to get as lower frequencies as possible in a simple to build, relatively small box that will produce quality sound at a reasonable but not ridiculous volume. It will be accompanying my B&W 686 S2 bookshelf speakers. If you know of a great 10'' sub that suits this application please let me know.

I'm not very good at that loudspeaker thing, but please bear with me. Let's get pragmatic for a second.

How large is your room ? Room gain is the most important thing for bass. you need to think about this first, then required SPL, then and only then what driver will fit the bill.

Differences are what make this world go around, and account for the fact that somehow Donald Trump got elected to the Presidency.

Please don't spoil the fun. Since The Donald got elected, your country stopped randomly bombing the sh*t out of the rest of the world. Are you complaining about this? Please elaborate if you think more bombs need to be dropped.

 

[Myleso]

Myleso, try a few things.....

I completely understand your "pain". I've been reading this forum for years, and have many of the same limitations you have. I'm trying to get help with a project myself right now. My observation of this forum is that there are a lot of lurkers on this site, who despite their posts, probably never build a project. Then, there are guys who build stunningly beautiful speakers, to the point where I can only imagine that they are supremely talented, or own professional manufacturing spaces. Or both. And then there is this vast area in between. I suspect that many of the people on this site are of the engineering persuasion. I've read posts where they argue about technical points for 50 pages, but won't answer a question for someone like you, in a simple manner.

Although my moniker is homebuilder, that is not my profession. That is my hobby. I sell high technology, cutting edge equipment, and have personally mastered one of the most difficult languages in the world, but I still cannot grasp the math, and the technical aspects of speaker design. That is why guys like Andrew Jones exist. I also work with engineers all of the time, and they tend to be dismissive of other professions. But, put them in front of 200 people and ask them to give a speech, and they will turn red and start puking their guts out due to being nervous.

I think there is an incredible marketing opportunity here, for one of these really smart guys on this forum to offer paid services to guys like you and I. Design us a crossover. I'm not speaking for you, but I'd gladly pay. I've proposed that in the past, and have been ignored. My thought is that I've built a dozen houses by myself...what is holding everyone else up on this site?? It is DIY....

I have a couple suggestions for you on this site:

1. Look for a kit that you can build, that is well documented. Dayton sells some nice kits. I've looked at their Ultimax 15" and 18" drivers, and kits. They seems like a super bargain. May be bigger than what you need.
2. Look at designs like Pi Speakers, DIYaudio, Linkwitz kits from Madisound, etc.
3. Look at the Cult of the Infinitely Baffled site. Don't know if you can apply that in your case though. I can in mine, and they are super easy to build.
4. Consider whether you would rather just work some extra hours, make a few extra bucks, and order something on line, or from a local stereo shop.

Good luck with your project. And, no offense meant to any member of this forum. Differences are what make this world go around, and account for the fact that somehow Donald Trump got elected to the Presidency.

Haha I think it was more like intolerance for diferences that got Dump elected.

Thanks for the response, ill continue to sift through pages of disagreements for morcels of useful information for years to come I expect 😉 Haha nah everyone is just trying there best and taking time out to help a newbie is awesome, cheers everyone.

Ill use a kit when I build a set of speakers for sure but I think Im pretty set on my subwofer build now. A Dayton Audio RSS315HF-4 12'' in a 2 cu ft box with a MiniDSP PWR-ICE 125 plate amp. If anyone has a good reson not to build this, let me know now please 🙂 Im about to order it all.

 

[scottjoplin]

Hi folks. Has anyone here heard or built sub using Linkwitz Transform? I have read a lot about it and Linkwitz open baffle undertakings. I have an open baffle set up myself. I'm concerned though about the power and excursion requirements

 

[AndrewT]

...........using Linkwitz Transform? ................. I'm concerned though about the power and excursion requirements

you are right to be concerned. You must do some predictions on power and excursion for a transform that extends the frequency downwards.
If I remember correctly: halving the LF roll-off frequency (while maintaining the same Q), requires 4 times the power and 4 times the excursion, while maintaining the same mid and treble frequencies of the system.

 

[scottjoplin]

you are right to be concerned. You must do some predictions on power and excursion for a transform that extends the frequency downwards.
If I remember correctly: halving the LF roll-off frequency (while maintaining the same Q), requires 4 times the power and 4 times the excursion, while maintaining the same mid and treble frequencies of the system.

Thanks. I think if enclosure size is overriding factor it might be worth considering but only for very low frequencies. I have some suitable drivers and timber knocking about so I may have a play