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-   -   Home audio loudspeaker - 8"/10"/15" Coaxials crossover at 1000Hz (https://www.diyaudio.com/forums/multi-way/342273-home-audio-loudspeaker-8-10-15-coaxials-crossover-1000hz.html)

swara 4th September 2019 07:38 AM

Home audio loudspeaker - 8"/10"/15" Coaxials crossover at 1000Hz
 
I am interested in a new sealed box loudspeaker project for home with decent sound dispersion to achieve good soundstage and imaging. I also want good bass at low volumes / listening levels.

It will be used in a 4m x 5m room with a listening distance of about 2.75m.

I am open to using a passive crossover or a Hypex Fusion plate amps (with active DSP crossover). I am trying to achieve a crossover point to match the tweeter's off axis response matches the woofer's off axis response.

Please answer my below questions:

Plan 1: 3-Way loudspeaker with 10" Seas A26RE4 as woofer, 8" Eminence BETA-8CX and PRV audio D290Py-S or BMS 5531ND.
Can I crossover 8" Eminence BETA-8CX and PRV audio D290Py-S or BMS 5531ND at 1000Hz? Does the cone have enough area to load down to 1000Hz?

Plan 2: 3-Way loudspeaker with 10" Seas A26RE4 as woofer, 10" Eminence BETA-10CX and PRV audio D290Py-S or BMS 5531ND.
Can I crossover 10" Eminence BETA-10CX and PRV audio D290Py-S or BMS 5531ND at 1000Hz? Does the cone have enough area to load down to 1000Hz?

Plan 3: 2-Way loudspeaker with 15" Eminence KL3015CX-8 and PRV audio D290Py-S or BMS 5531ND
Can I crossover 15" Eminence KL3015CX-8 and PRV audio D290Py-S or BMS 5531ND at 1000Hz? Does the cone have enough area to load down to 1000Hz? Will this become too directional?

What kind of directivity sounds best?
Constant and narrow over as much of the bandwidth for good imaging and timbre using a 15" coaxial
OR
Wide(er) bandwidth for a wider soundstage using a 8" coaxial

Is 10" a compromise between the 8" and 15" coaxials?

I am new, please be kind and educate me.

TBTL 4th September 2019 10:40 AM

The Eminence coaxials strongly beam at high (>5 kHz) frequencies. B&C Speakers has better drivers with a constant 100 degrees from 2 kHz onwards.

krivium 4th September 2019 11:28 AM

Hello, About FC for coaxials ( Tannoy style where membrane of mid is used as extension for horn) from my experience it is not something you can choose freely/ arbitrarly. The driver overall diameter will ( more or less) dictate where you can cross direct radiator to horn/ waveguide loaded compression driver.

With a 15": you can expect an fc in the 1/1,1khz vicinity,
12": in the 1,2khz
10": in the 1,3/ 1,4khz 8": in the 1,5/ 1,6khz.

This doesn't have to do about membrane area of mid but directivity control of the 'horn' part: you need both to be matched ( so for driver diameter listed you can deduce this is the point where directivity is around 90*90 for the direct radiator). Check with datasheet of different models from differents manufacturers and you'll see the numbers i gave are the trend. In scenari you gave only the 15" will accept close to 1khz fc. But fc is only one of many parameters in the whole design process.

About directivity what sound best? Well there is no definitive answer as it will depend from your own preference, the kind of presentation of audio you want, your room,....

For my own i'm happy with 90*90 from 1khz and up ( for coax Tannoy, i own system 800, worked and listened to almost all the late 90's pro line and liked them). I find 12" and 15" superior tho. Last thing, a 8" isn't 'wider' directivity wise, the frequency where control happen is just 'shifted' higher in frequency ( where the horn start to take care of directivity).

Overall for Tannoy kind, the directivity is almost 'constant', you'll have some beaming in the high end part of spectrum but nothing really bothering in my opinion ( and the high will be 'ragged' in frequency response because of discontinuity between horn and direct radiator, this is one of the compromise of this kind of drivers). And as TBTL stated you'll have to check brand's offer for the 'best' directivity behavior in high end ( or the one you want, constant isn't an absolute rule for everyone preference).

multitask 4th September 2019 12:25 PM

Denovo Audio Vortex coaxial Speaker Kits
Vortex Speaker Kits | HiFiCircuit

krivium 4th September 2019 12:46 PM

Hi,
Yes those drivers seems very good indeed ( directivity control). Maybe this is an option for the OP as he is located in USA. Other brand's offer exist tho, Beyma, Bms, B&C,... very good quality drivers exists.

That said the original plan to use three way ( with a dedicated low/sub way) should not be dropped along imho.
This is a real gain in quality to relieve the coax from low end duties: medium is cleaner and if you make the box closed it is even better ime as you don't have mid leaks anymore to confuse medium too. You can play with cabinet width for BSC and fc for the low end too...

That said it may not be as straigthforward as building a kit: the op will have to simulate a bit, maybe use a linkwitz transform to adapt the now medium ( coax's direct radiator) to the system...
Worth the effort imho, but it is an effort ( need to learn how to measure, how to simulate, invest in mic/soundcard/software and how to use it...).

TBTL 4th September 2019 12:49 PM

The Denovo Vortex also loses most of its upper treble when going off-axis, see these measurements: Vortex Speaker Kits | HiFiCircuit

krivium 4th September 2019 01:00 PM

Tbtl, yes but isn't it a common character for this kind of drivers? The graph looks pretty smooth to me. For my own preference i do not listen on axis, something like 15* off axis and despite the fact my system 800 are designed for nearfield and i'm using them 'midfield' ( 2,5m away listening spot) i don't find the high gradual roll off to be bothering to me. Other flaws are much more disturbing to me with this particular drivers.

Qts 4th September 2019 09:48 PM

Try BMS 15C262 15" coaxial with with active DSP crossover.

krivium 5th September 2019 01:10 PM

+1 with Qts comment: BMS coax are really good drivers and dsp will help a lot ( you may need some delay for direct radiator as emission point may not be coincident for compression driver and direct radiator).

Swara: may i ask why a 1khz fc is important to you? ( i know the answer for myself but would like to know yours ;) ).

swara 6th September 2019 04:46 AM

@krivium: Thank you for your responses.

I want the CD to handle all treble (1.2kHz - 20kHz) and not the woofer.
I want to match the off axis response of the woofer and tweeter as much as possible, to avoid beaming.

I am curious to know your answer.

@Qts and krivium: I will check the BMS coaxial drivers.
I have one more question: Since these drivers are very efficient, will a high power Class D amplifier in the plate amp with DSP, make the loudspeaker shouty for home audio?

Quote:

Originally Posted by TBTL (https://www.diyaudio.com/forums/multi-way/342273-home-audio-loudspeaker-8-10-15-coaxials-crossover-1000hz-post5905025.html#post5905025)
The Eminence coaxials strongly beam at high (>5 kHz) frequencies. B&C Speakers has better drivers with a constant 100 degrees from 2 kHz onwards.

@TBTL: Do you have any measurements of Eminence coaxials?

Quote:

Originally Posted by krivium (https://www.diyaudio.com/forums/multi-way/342273-home-audio-loudspeaker-8-10-15-coaxials-crossover-1000hz-post5905108.html#post5905108)
Yes those drivers seems very good indeed ( directivity control). <snip>

I think that the 15" coax will be hardly moving at average home listening levels of 70 - 85 dB. I prefer a sealed box alignment because it loads the bass better in the room (less room nodes, compared to Bass Reflex) and tight bass.


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