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PostPosted: September 14th, 2018, 10:51 am 
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Jim G wrote:
....It has to be understood they are old technology of course, and come with that baggage but are completely suited to home or studio use in the right system imho.

No argument about newer technology Tom. It wasn't his question though.

Cogito wrote:
...When and why anyone would use guitar woofer for home audio?

I would suggest if you were interested in a high efficiency system, say a 2 way, and were comfortable with the limitations of older drivers, the E-145 would be a good choice. They sound natural. Don't know if there are others.


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PostPosted: September 14th, 2018, 6:31 pm 
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tomp wrote:
In addition, even a used E145 sells for around $300. For comparison, the Dayton Audio RSS390-HO 15 " woofer has an Xmax of 12mm which is almost double the linear output and sells new for $190.


The difference in xmax between E145 and RSS390 is due to their application. E145 is a woofer and RSS390 is a subwoofer.
E145 is capable of producing 110dB at 47Hz where as RSS390 is capable of producing 110dB at 33Hz.

Piston Excursion calculator

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PostPosted: September 14th, 2018, 6:34 pm 
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SoundMods wrote:
Free air resonance and displacement goes a long way to determine bass performance in any box. To add insult to injury with a Fs of 35-Hz. you will get issues a decade above at about 350-Hz. That would make it seem like one is getting a lot of bass but it is more along the lines of "boom."


I dont get it. Can you explain?

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PostPosted: September 14th, 2018, 6:52 pm 
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Cogito wrote:
SoundMods wrote:
Free air resonance and displacement goes a long way to determine bass performance in any box. To add insult to injury with a Fs of 35-Hz. you will get issues a decade above at about 350-Hz. That would make it seem like one is getting a lot of bass but it is more along the lines of "boom."


I dont get it. Can you explain?



Maybe Tom can explain it better -- but a decade above the Fs will be affected in terms of a form of distortion that manifests itself as a muddy quality. That's why the AR-3 worked so well -- with a free-air resonance of 5-Hz. only up to 50-Hz. was impacted which had the effect of supporting the lower bass in subjective terms. In box it had a 42-Hz. resonance. A 35-Hz. driver in box can have a box resonance as high 60-Hz. with a 12-db/octave rolloff from there in a vented or ported box.

Displacement plays a roll in terms of pumping the air. I have a pair of B&W subwoofers that just now sit in my basement. They have 10-inch drivers in a sealed box and will travel a half-inch. In my room they provided overwhelming power down to 25-Hz. WOW! I would guess the free air is somewhere in the single digits.

I hope I helped.

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PostPosted: September 15th, 2018, 7:39 am 
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Cogito wrote:
tomp wrote:
In addition, even a used E145 sells for around $300. For comparison, the Dayton Audio RSS390-HO 15 " woofer has an Xmax of 12mm which is almost double the linear output and sells new for $190.


The difference in xmax between E145 and RSS390 is due to their application. E145 is a woofer and RSS390 is a subwoofer.
E145 is capable of producing 110dB at 47Hz where as RSS390 is capable of producing 110dB at 33Hz.

Piston Excursion calculator


Not quite accurate. Although the E145 would not be considered a subwoofer, the Dayton is quite happy going up to 200 Hz, making it a wide bandwidth woofer. It is also not advisable to use any 15" woofer much higher than that because of beaming at higher frequencies that could potentially cause problems with matching at crossover frequencies to other drivers.


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PostPosted: September 15th, 2018, 7:53 am 
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Re: Walt's claim about problems a decade above Fs, I believe the problems he mentions are more related to beaming which depends more on diameter than Fs. As the radiation pattern narrows, more energy is put on axis and room contributions get less. That can be either good or bad depending on the room. If you have a problem room decreasing room contributions can be helpful. However it will change the perceived timbre and spatial characteristics. I have found that it is usually better to have the radiation patterns match at the crossover frequencies regardless of the beamwidth. Beaming at higher frequencies will certainly accentuate those frequencies.

Distortions at higher frequencies are usually the result of insufficient cone rigidity causing breakup although that breakup can also happen at lower frequencies but higher excursions. That will certainly muddy the sound but is more a result of cone design than distance from Fs. There is no doubt that the higher the frequency required from a cone the greater the demands on cone design. Just making the cone thicker can help strength but affects the TS parameters and efficiency. Cone design is probably as much an art as science because of all the competing parameters. As with everything compromises are necessary.


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PostPosted: September 18th, 2018, 1:11 pm 
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Haven't seen any Guitar woofer maker talk about "voicing" the driver for guitar applications. Guitar Amps have equalizers and tone controls for voicing, so I doubt guitar woofers are voiced. Strictly judging by the retail prices, the quality guitar woofers may not be as good as the high-end home audio woofers.

Harmonics are the soul of any music instrument. Amps should not have problems passing thru' the harmonic content the driver. I think the most important feature of the guitar woofers is their ability to reproduce the harmonic content within a high bandwidth (usually 50Hz to 3kHz).

For the last couple of days, I am using horn loaded Guitar Woofer Eminence Kappa 15c with 4th order crossover points at 70Hz and 700Hz. There is definitely a significant difference between Kappa 15c's presentation of midbass and midrange with that of Altec 411. Kappa 15c is a high compliant and low excursion driver (xmax = 2.4 mm and Qts = .25). 411 is also high compliant driver with excursion of 7mm and .28 Qts. Bl is identical for both drivers.

Altec 411 direct radiator sounds well rounded in the mid-range with well blossomed midrange and impactful low-mid and upper bass. Compared to this, Kappa reproduces the musical instruments with better timber. I can clearly hear the harmonics coming thru on Kappa which are not that noticeable on Altec 411. Very little difference in vocals (do vocals have harmonics) . Kappa's presentation is not that "impactful" which I believe is due to the following factors.
1. Horn loaded application are about 10 times more efficient than direct radiators, so they not need to move as much air (pressure) to generate the same sonic SPL
2. Smaller excursion of Kappa limits its ability to move air.

The presence of harmonics in the foundation frequencies (80-800Hz approx.) has a significant effect on the overall sonic experience. There is some booming which could be due to the phase shift of high order crossover at critical frequencies.

I am theorizing that smaller excursion of Kappa 15c is giving it the ability to react faster to harmonics.

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PostPosted: September 18th, 2018, 2:41 pm 
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1. Horn loaded application are about 10 times more efficient than direct radiators, so they not need to move as much air (pressure) to generate the same sonic SPL

This is a slightly misleading statement. It should say that the driver in a horn loaded system does not have to move as much air "AT THE DRIVER CONE" to achieve the same external SPL. SPL is a function of volume velocity and for a given size cone, the amount of excursion. It has nothing to do with efficiency of the driver itself. Higher efficiency drivers need less power to move the same volume of air, but whether the driver is high or low efficiency it must have the same excursion to move the same volume of air. Note that I am not talking about gain with horns or ported systems, but only the raw movement of the driver in an unassisted enclosure.

In a horn, the transition from high pressure and low volume to low pressure high volume does allow for higher SPLs for a given cone excursion inside the horn but it is that transform that allows the lower excursion, not sensitivity. Think of a regular electrical transformer with the voltage being equivalent to driver pressure and the current being equal to volume displaced. For the sake of example, you could have a very low efficiency driver in a horn enclosure so that the overall efficiency with the horn is the same as another direct radiating driver and the excursion of the horn loaded driver would be less for the same SPL. That is because in the horn the higher pressure compared to a direct radiator equates to the higher voltage on the primary of the transformer. Once through the horn (transformer) the higher pressure transforms to higher volume at the low pressure side, therefore the cone does not have to move as much to achieve the same volume velocity but does have to create a higher pressure inside the horn for the transform to work.

It is the same as an electrical transformer where if 100% efficient, the product of the voltage times current on the primary side equals the voltage times current on the secondary side. The transformer substitutes voltage for current either way depending whether it is a step up or step down transformer. With horns, they convert pressure to volume.


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PostPosted: September 18th, 2018, 4:10 pm 
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[quote="Cogito"]Haven't seen any Guitar woofer maker talk about "voicing" the driver for guitar applications. Guitar Amps have equalizers and tone controls for voicing, so I doubt guitar woofers are voiced. Strictly judging by the retail prices, the quality guitar woofers may not be as good as the high-end home audio woofers.


You will not find the kind of hi-fi marketing hype you are used to reading when it comes to guitar amps. Guitar speakers are part of a system as sold by such manufacturers as
Fender, Gibson, Marshall, Mesa Boogie, and Peavey to name a few. Those manufacturers make the cabinets and amplifiers together with speaker drivers typically by others. The OEM driver suppliers market to the guitar amp. manufacturers and not the general consumer.

Musicians buy what sounds good to them and their art -- PERIOD. The concern is only that the finished product serves their art and the guts or how that sound is created is not even a consideration. Things like the guitars themselves, magnetic pick-ups, picks, and strings get the attention to dial-in the sound. Of course there is the tube vs. solid-state conflict but that is outside any considerations regarding drivers.

There are those that theorized that hi-fi equipment would better serve guitars -- you know -- a nice audio amp. tied toa nice hi-fi speaker -- the results were disappointing to say the least.

The applications are not compatible. One is to reproduce music as accurately as possible -- the other is to simply make music.

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PostPosted: September 18th, 2018, 5:06 pm 
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Tom,

I was specifically talking about the "horn loaded applications", other than that we basically agree on all the points you raise.

In horn loaded applications, cone area is not a critical factor of SPL as the output from the cone can be compressed to generate higher pressures to match that of larger cones and larger excursions.

In regards to the excursions, larger excursions require firmer cones and larger mass. Laws of physics play a negative role on the sound quality of heavier mass, large excursions and larger diameter cones. As the mass increases, momentum increases which reduces the response of voice coil to the changes in electrical energy. It takes longer time to accelerate and decelerate. That is why large excursion and large mass sub woofers HT subwoofers are not deemed suitable music reproduction.

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