Closed back midrange drivers - problems?

[River757]

I see these listed right now on various retail sites and I've seen them used in less expensive systems for years. And, these were included in my 3-way kit from Radio Shack I built back in the early 80s* and I didn't notice them sounding particularly bad i.e. no nasal qualities or "hollowness" though admittedly I didn't do any controlled comparisons to arrive at that decision.

What are the negatives of such a driver? I'm thinking of building a 10" 3-way system to be used a learning exercise so I don't want to spend much - think of it as a speaker built by Chevrolet, not Audi - and will only be using them for "casual" use in a bedroom or living room where no critical listening will be done.


* here it is on page 60. FYI the spec page is incorrect: the xover point for the midrange was 900Hz, not 2000Hz as printed in the catalog. I built 4 cu/ft bass reflex enclosures for that kit - whew was that big, even back then. What a hassle they were taking them to college!

[kipman725]

The box volume is defined by the manufacturer and therefore if incorrect cannot be easily modified. In addition to this a closed back midrange as it cannot have a large volume box cannot be tuned very low. For example the goldwood midrange on parts express site goes down to 800Hz. This can be an advantage though as you can use this as part of your crossover.

[tinitus]

Originally Posted by kipman725

In addition to this a closed back midrange as it cannot have a large volume box cannot be tuned very low. For example the goldwood midrange on parts express site goes down to 800Hz. This can be an advantage though as you can use this as part of your crossover.

more or less like a tweeter
and you know to stay well away from ressonance point, and not place xo point too close
either it could cause distortion
and/or, impedance ressonance peak could make the crossover more problematic

at least thats the theory
but with active xo, maybe less problems, I dont know

[River757]

Originally Posted by kipman725

For example the goldwood midrange on parts express site goes down to 800Hz.

That's pretty close to what I was shooting for, mostly to keep the cost of the xover down. 600Hz would be better but I'll have to look at what is available out there to see if that is possible (Parts Express used to sell a pretty nice - for a sealed driver - midrange made by Pioneer but I just checked and it's gone now ).

[dave_gerecke]

Hello River757, I realize this is a few days late, but if you are still looking for some closed back mids, I have a pair you can have, you pay shipping. I have the tweeters that were used with them also.

Peace,

Dave

[River757]

Thanks for the offer Dave but I've decided to go with a conventional mid driver operating in a subenclosure. While I can't spend much, I decided I don't want to sacrifice too much, in this case the important midrange spectrum (and want the xover to be down around the 400Hz range).

[fastbike1]

If the midrange is not closed back, it is usually put in it's own enclosure so that the back wave from the woofer doesn't interfere.

Leaving an open back mid in the same volume as the woofer is a sure recipe for muddy mid-range.