OB with Alpair 12P and Eminence Beta 15

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Ali Tait
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#31 Re: OB with Alpair 12P and Eminence Beta 15

Post by Ali Tait »

A few of us have OB's with either Alphas or Betas, the Betas seem to resolve more detail then the Alphas to my ears.
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#32 Re: OB with Alpair 12P and Eminence Beta 15

Post by Max N »

MJK wrote: Sun Jul 02, 2017 2:58 pm OK, your plots make sense now.

Looking at your final plot, which produces the deepest bass output, you are using two Beta 15A woofers with a lower crossover point producing about 95 dB/2.83 V/m down to about 50 Hz. I have a very similar simulation that produces a little more output (96 dB/2.83 V/m) using two Alpha 15A woofers and a higher (less expensive) crossover frequency.

In summary, I think you can get the same low frequency results using less expensive woofers and crossover components. What performance advantage are you gaining by using the Beta 15A woofers?
As Ali said, the choice of Betas over Alphas is partly a subjective preference having heard them. Also, as I said earlier in the thread, I don't want to energise the room mode at 40 Hz. The Alpha with fs at 41Hz and Qts of 1.26 would be asking for trouble. I haven't finally decided on Betas yet. I'm a little worried by the low impedance when connected in parallel. I may try simulating some of the 4ohm or 16ohm Eminence drivers.
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#33 Re: OB with Alpair 12P and Eminence Beta 15

Post by Max N »

MJK wrote: Sun Jul 02, 2017 2:58 pm With respect to the sound being course during break in of the Alpair 12P with a full range signal, I think the performance of the full range driver will improve significantly once you remove the low frequency signal and redirect it to the big woofers. A high pass crossover on the Alpair 12P driver will clean up the performance and relieve low frequency strain on the full range driver
Yes, I'm hoping so. Fingers crossed :)
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#34 Re: OB with Alpair 12P and Eminence Beta 15

Post by Max N »

Does anyone have any experience with the Eminence Delta 15?
They are available in a 16 ohm version. I'm thinking I could run two in parallel and get a decent impedance.....
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#35 Re: OB with Alpair 12P and Eminence Beta 15

Post by IslandPink »

16 ohm one has higher resonant frequency at 45Hz , won't go quite as low as the Betas.
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#36 Re: OB with Alpair 12P and Eminence Beta 15

Post by Max N »

I hadn't
IslandPink wrote: Mon Jul 10, 2017 7:45 pm 16 ohm one has higher resonant frequency at 45Hz , won't go quite as low as the Betas.
I hadn't spotted that, thanks Mark.
I'm having a bit of paralysis by analysis here....
I'd like to just buy a few pairs of different drivers and try them all, but I'm really having to watch the pennies....
Maybe I'll try to sell some stuff that I'm never going to use to raise a bit of cash :)
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#37 Re: OB with Alpair 12P and Eminence Beta 15

Post by steve s »

Mark has a good point you want as low an fs as you can get,
But it has a big magnet and double the bl which generally is a speaker that's faster with more life.
Weight and strength of the magnet usually relates to the cost of the speaker
It's important to look at the response graph (and see how it's measured) to check it's going to do what you want with no big peaks in the frequencies where you want to use it.. look on blue Aaron's website if you have not already. Do your home work and buy the best you can afford would be my advice
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Toppsy
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#38 Re: OB with Alpair 12P and Eminence Beta 15

Post by Toppsy »

Max,
Have you had a look at the Monacor range of 18" and 15" woofers? http://www.monacor.co.uk/categories/speaker-technology/
I'm not up on the price of the Eminence drivers but I can get you any the Monacor drivers at Trade price.

Send me a email of any the drivers that look to meet your requirements and I'll advice you the trade price. These I can have delivered direct to you.

Regards
Colin
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#39 Re: OB with Alpair 12P and Eminence Beta 15

Post by IslandPink »

steve s wrote: Tue Jul 11, 2017 8:25 am But it has a big magnet and double the bl which generally is a speaker that's faster with more life.
Weight and strength of the magnet usually relates to the cost of the speaker
Yes, but ....again ....
The speed and life bit is supposed to be being provided by the midrange driver.
If you want a driver that's going to be an OB bass driver it doesn't want a really bit magnet and a high BL. If you get one like that, it's more of a midrange driver when used on OB because it'll just have a rising response from the bass through to about 300Hz or more. Then you'll have more trouble crossing to eg. the Alpair, and need EQ from 150 down to 50Hz .
This sort of driver is more suited to ported box.
What you want is a driver with the RIGHT SIZED MAGNET to balance against the cone mass to give you a flat response in the upper bass and lower mids when used on a big baffle or infinite baffle as per the datasheet. Look at the datasheet FR of the Beta 15A - it's overall flat from 100Hz to 500Hz. When you use a bit choke as per the Quasar you pull the response down above 100Hz and all it sort-of pivots clockwise around 100Hz so you get relatively more bass below 100Hz than on the datasheet curve.

What you've had to do with your 18" unit on the latest build is load it with undersized ports, which is precisely because it's a large-magnet driver which is more suited to a ported box than OB use.
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#40 Re: OB with Alpair 12P and Eminence Beta 15

Post by Max N »

Toppsy wrote: Tue Jul 11, 2017 9:05 am Max,
Have you had a look at the Monacor range of 18" and 15" woofers? http://www.monacor.co.uk/categories/speaker-technology/
I'm not up on the price of the Eminence drivers but I can get you any the Monacor drivers at Trade price.

Send me a email of any the drivers that look to meet your requirements and I'll advice you the trade price. These I can have delivered direct to you.

Regards
Colin
Thanks Colin I'll take a look :)
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pre65
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#41 Re: OB with Alpair 12P and Eminence Beta 15

Post by pre65 »

Max, I saw these on Ebay, he has 2 pairs.

http://www.ebay.co.uk/itm/Two-working-E ... 1438.l2649
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#42 Re: OB with Alpair 12P and Eminence Beta 15

Post by Max N »

steve s wrote: Tue Jul 11, 2017 8:25 am It's important to look at the response graph (and see how it's measured) to check it's going to do what you want with no big peaks in the frequencies where you want to use it..
....Do your home work and buy the best you can afford would be my advice
IslandPink wrote: Tue Jul 11, 2017 7:08 pm What you want is a driver with the RIGHT SIZED MAGNET to balance against the cone mass to give you a flat response in the upper bass and lower mids when used on a big baffle or infinite baffle as per the datasheet. Look at the datasheet FR of the Beta 15A - it's overall flat from 100Hz to 500Hz. When you use a bit choke as per the Quasar you pull the response down above 100Hz and all it sort-of pivots clockwise around 100Hz so you get relatively more bass below 100Hz than on the datasheet curve.
Thanks both, all this input is very helpful. I know the above quotes are selective, but I'm actually taking in all that you've said and it is clarifying my thoughts, if that makes sense
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#43 Re: OB with Alpair 12P and Eminence Beta 15

Post by IslandPink »

I know, there's a tendency to think you could spend more money and get something better ( eg. with Eminence ) but at the end of the day you have to have the right parameters for the job. There are plenty of 15" drivers there with bigger magnets , lower Qt and greater power handling ; but what are you going to hear in your room on a limited-sized OB at room-level power inputs ? I've looked through most of the Eminence range and there's nothing I can see at present that does the job on OB quite as well as the Beta 15A.
If you want to spend more money, get a pair of these and run them at around 9V supply to the electromagnets :D
http://www.supravox.fr/anglais/haut_par ... 00_EXC.htm

I will have a look through Colin's link to the Monacor's , though. There were a couple that looked interesting. As usual though, it was the cheaper ones with the limited power handling and the smaller magnets ..
Steve - sorry to labour this point, but look at the magnet size on the Supravox 285GMF ( it's under a fancy cover and is not that big ) and note the BL, which is around 10.

Edit : yes, I think the Supravox 400_2000_EXC is the best OB bass unit you could buy , look at the data here :
http://www.supravox.fr/anglais/mesures/mes400EXC1.htm
Clean out to 3kHz.. :notworthy:
Be the first one on the forum to own one, Max !!
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#44 Re: OB with Alpair 12P and Eminence Beta 15

Post by simon »

1085 Eur each Mark, I think you should try them :-D

http://www.hornfabrik.de/preislistesupravox.htm
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#45 Re: OB with Alpair 12P and Eminence Beta 15

Post by Max N »

pre65 wrote: Tue Jul 11, 2017 7:25 pm Max, I saw these on Ebay, he has 2 pairs.

http://www.ebay.co.uk/itm/Two-working-E ... 1438.l2649
Thanks Phil, but I won't get away with 18"ers. I need to end up with something acceptable to my other half :)
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