would this driver combo work well?

[trespasser_guy]

I am wanting to build a nice pair of speakers for a 2-channel system- no sub to be used here. In hopes of meeting my bass requirements while still keeping a relatively low cost, I am turning to cheaper pro drivers, namely Selenium and Eminence. I am concerned about the matching, though. I REALLY wanted to do a horn-loaded 3-way system, but money, space, and carpentry skills are lacking. So, I have resolved to do a simple, yet nice looking pair of box-type speakers. Stil wishing for 3-way, but the added driver puts too much extra in the expense area. SO, I have decided to do a 2-way system, and it is looking as though it will be crossed over at around 2000Hz. To be made up of the following:

one Eminence Alpha-12A 12" woofer OR one Selenium 12PW3CE 12" woofer
and one Selenium DH200H-M titanium compression horn tweeter

The enclosure will be about 3.5-ish cubic feet. About 14" wide x 12-18" deep x 30-38" tall. Not sure what all volumes those come out to be. Using the Parts Express speaker design software, he Eminence seems to have too high of an F3, while the Selenium is some 10-20 Hz lower. (I don't remember for sure what the difference was) All in all, which would be the best match? All parameters can be found at Parts Express, if they are needed. Also, if needed, I will be driving these speakers with a tube amp that puts out about 8 watts. After all is said and done, would I have een better off just buying a pair of Klipsch Heresy's? Or would these DIY speakers make me never think back upon the Heresy's? Thanks for the help.

[roddyama]

trespasser_guy,

For a two-way system with a horn the top and a direct radiator on the bottom, you would be better off with an x-over in the 500Hz to 800Hz range. This is would be the home version of the classic VOT type speakers. Here’s a link that describes the Altec VOT’s
http://www.soundpractices.com/images/smallVOT.pdf

Here is a link on horns. From Tom Dunker’s site and his links, you’ll be able to find tons of info on horns
http://invalid.ed.unit.no/~dunker/horns.html

Jammin Jersey’s is just one place that sell used equipment. It would be a way get higher quality equipment and stay closer to your budget.
http://www.jamminjersey.com/speaker3.htm#Altec

Have fun,
Rodd Yamashita

[kelticwizard]

Well, let's take look at the woofers. You are using PA speakers for home use, I imagine, because your tube amp output is only 8 watts and you want sensitivity.

Here is the Alpha. It has the smoother response of the two through the midrange. I guess we could call this 94 dB through the midrange response. The big rise in sensitivity could be addressed, to a greater or lesser degree, with an inductor in series.

The Thiele-Small numbers give us a mixed picture. On the one hand, you end up with a pretty smooth, desirable Qtc of 1.15-a bit higher than the optimal range, but no too bad. On the other hand, your F3 is around 63.

I should point out that most DJ boxes are 3 cubic feet, usually ported, (but so what), and have an F3 around 60 Hz. This is how they make their living, and most people find that to be an aceptable F3, even though you would like something deeper for home listening. If 60 Hz sounded "tinny", DJ's would have to use equipment that goes lower, and they don't. So you can slide by there.

Here is the graph of the Alpha 12:

[kelticwizard]

Here is the Selenium. It is a somewhat rough through the midrange. The rise in response near 1500 Hz also can be addressed somewhat by an inductor in series. It also will have an F3 in the 60 Hz range. A notch filter around 3500 might not be a bad idea in the crossover-either that or a very steep slope for the crossover.

[kelticwizard]

Considering that you have only 8 watts to work with, I would say that both of these are workable. Still, you would like to have a slightly deeper response from a large 3.5 cubic foot box, (100 liters). If I were to choose between these two, I think I would lean toward the Eminence because of the smoother midrange response and because it looks like it might be less tricky to cross over.

However, on that tube amp of yours. Does it have a 4 ohm output?

Reason: if you take two 8 ohm speakers and put them in parallel, you will have 6 dB extra output at the same voltage level. However, that voltage level, at 4 ohms, will actually be putting out twice the wattage that it did with an 8 ohm load. The result is, putting two 8 ohm speakers in parallel raises the sensitivity 3 dB.

Since these two PA speakers are about 94 dB through the midrange, what ever their stated sensitivity, that means that if you find an 8 inch speaker or even 6.5 inch speaker with 90 or 91 dB sensitivity through the midrange, hook a pair up in parallel per side, you will have a 93 or 94 dB sensitivity, probaby smoother response, nicer dispersion, and deeper bass in a smaller box.

I have not located these speakers yet, but the numbers seem possible. Do you have a 4 ohm output on the amp? Or a 16 ohm output-that can be configured to raise the sensitivity of two 8 ohm speakers hooked up in series.

Either one-4 ohm or 16 ohm output-would be helpful.

[kelticwizard]

Here is a possible alternative I found already. The Audax HP210GO. Have not used it-maybe somebody on this forum has.

It is rated at 92 dB-but the chart seems to show it is really 90 dB. They rate it as 6 ohms-but believe me, with a 5.6 ohm voice coil, it should be called an 8. Most 8's have a 5.6 ohm voice coil. It has a couple of dips in the response, but overall I would rate it around 90 dB. Two of them hooked up in series or parallel will yield an overall response of 93 dB, if you have the proper hookup.

I would put 2 of these into a vented box of 2.5 cu ft tuned to 48 Hz. You should be 3 dB down at 48 or 49 Hz.

They cost $35 each if you buy 4 or more at Parts Express. That's about $70 per side for your woofer, which was about what you were thinking with the PA models.
http://www.partsexpress.com/pe/pshow...number=296-136

I dont know what the Selenium horn tweeter was going to cost, but a 93 dB tweeter should be available for $20 I would say.

This is just a suggestion. I have not used this driver. There might be others that are better.

[trespasser_guy]

Thanks for the help.

I do have one question, which really doesn't relate to much, but has always made me stop and think... If you take a speaker that has a range from, say, 60-4000Hz, and put it in a ported box of whatever size you have, and it's F3 shows as about 40Hz, is this possible? With its response only going to 60Hz, how can it have an F3 of 40Hz? I just have always wondered...

[trespasser_guy]

Another thought, if I used two 8" PA drivers, each with a said 97dB sens. I would have about 100dB SPL, theoretically. But, if I used this, would having a xover point of 1200Hz be too high?

[trespasser_guy]

I was going to edit this by editing, but it has been over 30 min... so....

Ok, if I have the two 8-ohm woofers and an 8-ohm tweeter, the woofers in parallel for 4-ohms, I can't get 8-ohms out of the system. Can I? Need help here also.

[roddyama]

trespasser_guy,

The problem your going to find with 8” woofers and even most 10” woofer is that you won’t be able to find them with enough efficiency for your 8W amp. If you find a 10” that has 90+db/W/m (and there are very few) one unit will cost you at least $100 or more. 12” woofers are easier to find with higher efficiencies, but as with most direct radiators, the wider the bandwidth, the lower the efficiency. That means if you want a lower f3, you have to accept a lower max SPL from the amp/speaker combination. The trade-offs are co$t/lower f3/efficiency. According to Kelticwizard’s graphs, the Eminence appeared to be the best balance of compromises.

You could run the 12” up to 2kHz if you wanted to. I wouldn’t, but if you did, you might think about a 6db/oct cutoff at about 1000Hz for the woofer and a 12db/oct or steeper cutoff at 2000Hz for the Selenium horn. I gave my suggestions in my earlier post, but this would probably work.

If you go with the Eminence woofer and the Selenium horn, I would suggest that you save some room between the woofer and the horn for a future 6 or 8 inch midrange driver. This driver could than be a true midrange driver to run from about 300Hz to 3kHz.

Rodd Yamashita