Middriver selection?

[buggsson]

I am still struggling with what kind of a system to build. While I am trying to decide, I know as much as I will build either a sub and a two-way system on top of the sub, or a threeway system, all sealed.

When selecting mids, does the EBP-value (Fs/Qes) still have to be below 50 to be really suitable for a sealed implementation?

I will try to crossover to the tweeter at around 6 kHz, which narrows my search considerably. (I do not want to go lower than 4 kHz, minimum.)

I have the woofers more or less sorted out.

For a threeway system, can you really approach driver selection in a stepwise procedure as I am trying to? If not, can someone please lay out a proper procedure?

And what about polypropylen cones? I have stayed away from these in my subwoofer selection, are they okey as mids?

 

[Caferacer]

You can use a sealed box for pretty much any mid. As long as it goes as low as you need it to go in that sized box. Gives the best power handling too.
As for your upper end, a 4K crossover means 5.25" is about as big as you can go. 6K probably limits you to 4" without off axis problems.
Polypropelene has been used in a lot of good mids. The 5.25" Vifa's come to mind. Many poly mids have a nice rolloff at the top making them easier to cross high like you want to.

 

[Samuli^]

6kHz wave is about 5.6cm long, so even with a 3" driver you're going to have beaming issues and vertical lobing. How much that is subjectively a problem at those frequencies I don't know, but to me crossing over at 6 kHz doesn't sound practical.

What is your reasoning choosing XO that high? Also, before suggesting
a mid, how high are the woofers good to?

 

[planet10]

Here is a left field suggestion... i've recently been playing with the Fostex FF85K (not stock mind you) and have really been impressed. I've started thinking of this as a 3/4" tweeter which with its big surround allows XOs as low as 200-350 Hz. It opens up a whole new world of possibilities.

Its one downside is fairly low efficiency (~87 dB once i've done it up)

dave

 

[buggsson]

Well my reasons for wanting to go that high is to avoid crossing over in a region of interest, and I read it on a speaker manufactuers home page, that I trusted to know what he was talking about. I know most folks cross much lower. I guess I might have to rethink that. I see that even crossing over at 4 kHz would only allow me of using a 5.25" driver, I was planning to use primarily a pair of 7" or 8" drivers per channel. As it seems, I will have to comprimise, either in crossover frequency or driver size, or both?

I don't know where I would like to cross the woofers, it depends on the system I will decide on. Presently I am contemplating 3 different systems, and I am trying to find some suitable drivers to put into my software for simulations once I decide on system. For woofers, I have on my list from 10" to 15".

Maybe it would be wiser to first finally decide on the system and then go driver hunting?

 

[Caferacer]

There are compelling reasons for running a midrange high to keep the crossover out of our ears most sensitive region. Heck, check out the fullrange forum. Some people run a small mid "fullrange" and add just a supertweeter at like 10K. However, asking a standard 7" midwoofer to go that high is asking too much. Some are better than others, but they all get ragged and lose dispersion above say 3K.

 

[Samuli^]

If you're undecided on the woofers, you might want to look at the SLS series from peerless. These are modestly priced, but good quality drivers with okayish xmax (+-8mm) and the 10/12" versions will go happily to 1 Khz or so with good dispersion, allowing you lots of room to use small midrange to help cross high at the tweeter. Downside is these require relatively big boxes.

 

[tinitus]

This seem to be a good 12", not too many of those around

http://www.sbacoustics.com/specproduct.php?product_name=12 SB34NRX75-6

 

[Samuli^]

Looks like an excellent driver judging from the datasheet! How much does those cost and is there any distortion measurements available?

 

[tinitus]

http://www.madisound.com/catalog/product_info.php?cPath=45_338_381&products_id=8304

Madisound says 141USD, but sold out...I dont know how and why as they have not been on the market yet...funny that Madisound are the first to announce a "danish" driver, before its even available

Being in EU it might be worth a try to contact SBA directly

 

[buggsson]

Thank you all so far for your input.

I think that it might be best if I could descide on which system to strive for, otherwise, the options migth be too many and confusing. I'll start a new thread. It is very difficult indeed, in my opinion to know what to do, and when to do it, regarding this business of building loudspeakers.

 

[buggsson]

Apparently, there would be problems to go higher than 4 kHz such as off axis, beaming and vertical lobing if using larger mids than 5,25". However, you see all the time speakers using up to at least 8" units as mid drivers, so I guess there is at least one solution to come around the problem, or do they all sound bad from those perspectives?

As mentioned, some use fullrange drivers as mids, any negatives with that choice?

To get back to the ears and their most sensitive region, for the upper range, how high do you need to go, at a minimum, is there a general consensus, or any consensus at all in this regard, in which region shall you not cross?

Can someone just shortly explain how you can come up with the sizes you can use depending on crossover frequency, and perhaps with a tip on where I can learn more about how to choose drivers?

As to woofers, I have to do some simulations so I know which ones will give me my desired low end respons. Then I will know how high I can cross the woofers, and so forth.

 

[Caferacer]

"However, you see all the time speakers using up to at least 8" units as mid drivers, so I guess there is at least one solution to come around the problem, or do they all sound bad from those perspectives?"

8" two way is not bad per say, but compromized. Crossover has to be lower, like less than 2.5K. More stress on the tweeter. And there is still a big jump in horizontal dispersion at the crossover. It makes the crossover design harder to pull off. That's the real issue. No design is perfect, you always are making tradeoffs. A smaller midrange has a cleaner upper end. A bigger midrange has a cleaner lower end.

Speaking of fullranges with "helper" super tweeters added on at 10K. You will notice that those designers favor horn tweeters many times. I believe this is because the narrower dispersion of the horn better matches the midrange at that high crossover point.

 

[buggsson]

8" two way is not bad per say, but compromized. Crossover has to be lower, like less than 2.5K.

Will that be irrespective of the driver in question? I don't neccessarily want do use a 8", but something has made me decide that I would primarily want to use a larger mid, 8" or 7". That might change however as I proceed. Why I ask, is that some mids have recommended frequency ranges of like 33-5000 Hz. At least theoretically, I would believe that if you crossed one of those, it would be safe to cross at around say 4000 Hz so as not to stress it overly?

Also, how do you know that a mid driver is suitable for a closed application? EBP does not seem to be usable as with subwoofer drivers, what do you look for?

I found a web page about music and the human ear; http://www.silcom.com/~aludwig/EARS.htm
that says that the ears most sensitive region lies between 2000-5000 Hz, is that the region to avoid crossing over in?

 

[planet10]

As mentioned, some use fullrange drivers as mids, any negatives with that choice?

Visaton B200 with phase plugs or FE208eS would make killer 8" midranges. As long as you take care to use a tweeter with narrower dispersion (no domes -- something i find unnatural about domes so no loss), you won't have much if any of a tweeter flare at the bottom of its passband. XO between 5 & 10K.

dave

 

[planet10]

the ears most sensitive region lies between 2000-5000 Hz, is that the region to avoid crossing over in?

Yes.

Actually that might be where i have gained my dislike of domes -- they are most often XOed in that region.

dave

 

[buggsson]

Visaton B200 with phase plugs or FE208eS would make killer 8" midranges.

I take it that the FE208ES is ment to be the Fostex FE208ES? It seems to be disbanded, there is only a FE206ES in the FE series, or was that the one you had in mind? Also, the recommended volume for the Visaton is 70 L sealed, that's a tad large I would think, but that might be different, requires less volume when used as mid? The BG 20 8 ohms is stated as a similar product, would that seem to be a much worse driver? It only needs 30 L sealed.

 

[buggsson]

Can someone please go through the parameters of interest and what they should be, for the driver to be a good one for a sealed application?

I have seen manufacturers that state their mid drivers as to be used as sealed or vented, so I don't know how to pick them out if it is not stated.

 

[BHTX]

It all depends on the application and how the drivers are being used.
Honestly, I don't like the idea of mid drivers crammed in a box.
..Especially when they must be used in very small enclosures.
Btw, the B200 works best on an open baffle.

 

[tinitus]

http://www.tb-speaker.com/detail/1208_03/w5-1611sa.htm

http://www.tb-speaker.com/detail/1208_03/w4-654se.htm

Two fine mids(probably), one is 85db and the other 90db - powerhandling is sadly not too good, bust used solely as mids they should last, one is a bit better in this respect and at the same time with better sensitivity...try figure it out