Usher 8945P / Peerless HDS 810921 Two-way Posted

[Jay_WJ]

FYI, my new 2-way design has been posted at my website:

http://www.geocities.com/woove99/Spk...Usher_2way.htm

Any comments are welcome!

[ttan98]

I have a pair of 8945 in their boxes to be put in their cabinet, I also have a pair of complimentary usher tweeters.

your design looks very complicated, what is your ultimate efficiency you are getting? I think between 85-87db, quite low I think.

I like to design based on using active filter and biamp, via electronic x-over such as Behringer DCX2396. your design looks interesting esp. compensating for the dip at 1.2khz. It helps. This way I don't have to compromise on the efficiency at the same time, don't have to spend 100's of dollars on capacitors and inductors, using wrong components can be expensive, leaving 10-100's of dollars unused capacitors and inductors in the cupboard.

you should try open baffle, a total different experience to box speakers.

[Jay_WJ]

The efficiency isn't actually quite low as a small, conventional 2-way. It's 2 db higher than my RS180 2-way design. Even if you go your active route, you'll need to sacrifice the driver's raw SPL because you need to use BSC and notch filtering. IMO a notch filter at 900 Hz is required for this woofer. Otherwise, you'll have too much energy around this frequency. The XO is not that complicated actually. It's simply electrical 3rd order with a notch filter on the woofer net, and electrical 2nd order with a notch filter on the tweeter net.

[Dave Bullet]

Hi Jay,

I like your site because of your approach to voicing the speakers.

You seem to have a gentle 2 - 3dB fall from approx 1.5Khz down to 3Khz in both of your designs, which introduce a slight rise back again at the top end (to give a bit of extra sparkle / air).

This to me supports the "ear is more sensitive from 1 - 5KHz" that many people purport. This would definitely reduce the risk of fatiguing speakers that may otherwise be designed to measure flat.

Cheers,
David.

[ttan98]

Active filter and driving the woofer direct with the amp will give a more dynamic sound. My amp would only be about 50watt per channel. I need min 4 channels for 2 way. I am building 6 channels, the final price is very cheap and give good sound at the same time do the job I want.

A DCX 2496 is about US$250 it is very flexible and I can build many speakers with it. No need for caps and ind.

With a 85db effciency you amp must be of high powered and a good one is very expensive.

I can program baffle step in the DCX and not lose out on effciency. the notch filter is in parrallel with speaker has no impact on the efficiency, and will impact on the sound I believe.

I am in the process of building....and you have completed..cheers..and to each his own...

[Dave Bullet]

I can program baffle step in the DCX and not lose out on effciency. the notch filter is in parrallel with speaker has no impact on the efficiency, and will impact on the sound I believe.

Are you saying you can drive a speaker louder in an active configuration over passive - regardless of available power to each setup?

No matter how you allow for baffle step (attentuating the top end or boosting the bottom), you are limited by woofer excursion in how hard you can drive it. ie. a driver will only play so loud before excursion / thermal limits are reached. Whether power is "wasted" in a passive crossover or used more efficienctly in an active is of no consequence to the driver.

When I'm sick of passives, I plan on giving actives a go. There are quite a few benefits.

Cheers,
David.

[Jay_WJ]

I agree with Dave. Power will be wasted in a passive XO (i.e., lowered efficiency), but with available power, how loud (or dynamic, if you'd like) the speaker plays will not be affected by whether you use active or passive XO.

[Jay_WJ]

Originally posted by Dave Bullet
Hi Jay,

I like your site because of your approach to voicing the speakers.

You seem to have a gentle 2 - 3dB fall from approx 1.5Khz down to 3Khz in both of your designs, which introduce a slight rise back again at the top end (to give a bit of extra sparkle / air).

This to me supports the "ear is more sensitive from 1 - 5KHz" that many people purport. This would definitely reduce the risk of fatiguing speakers that may otherwise be designed to measure flat.

Cheers,
David.

I'm not 100% certain that the simulated woofer-tweeter balance is really accurate. But after voicing, I found that tweeter's 2-3 dB fall in that range (in my simulation, at least) sounds "right" to my ear. Anyway, this is consistent with findings in Equal-loudness Contour:

http://en.wikipedia.org/wiki/Equal-loudness_contour

[ttan98]

Originally posted by Dave Bullet


Are you saying you can drive a speaker louder in an active configuration over passive - regardless of available power to each setup?

No matter how you allow for baffle step (attentuating the top end or boosting the bottom), you are limited by woofer excursion in how hard you can drive it. ie. a driver will only play so loud before excursion / thermal limits are reached. Whether power is "wasted" in a passive crossover or used more efficienctly in an active is of no consequence to the driver.

When I'm sick of passives, I plan on giving actives a go. There are quite a few benefits.

Cheers,
David.

I lose 3-4db if I use passive components, with active I don't, besides these speakers are not efficient anyway, to maximise their effciency by driving them directly with LOW powered amplifier. A 85db speaker needs HIGH powered amp to give a good listening level.

Also, direct connection to the amplifier would have better control of the cone. I don't have to concern of impedance level(irregular) matching if I use passive components with the woofer as well.

[Jay_WJ]

Originally posted by ttan98

A 85db speaker needs HIGH powered amp to give a good listening level.

Interesting. What is your good listening level? If it's Dolby reference level for HT, you'll really need an amp with high power---woofer's excursion will be limited anyway before reaching that level unless you use a subwoofer. But if it's for music, 25 watt amp (e.g., Nad) is more than adequate for these speakers to give me a good listening level.